.drone.yml

@@ -5,5 +5,6 @@ steps:
 - name: build & test
   image: euantorano/zig:0.9.1
   commands:
-  - zig build test
+  - apk --no-cache add build-base sdl2-dev
-  - $(find zig-cache -name test) main.zig
+  - zig build
+  - ./zig-out/bin/test main.zig

.vscode/launch.json

@@ -2,23 +2,26 @@
 	"version": "0.2.0",
 	"configurations": [
 		{
-			"name": "Build",
+			"name": "Ona",
 			"type": "gdb",
 			"request": "launch",
 			"target": "${workspaceFolder}/zig-out/bin/ona",
 			"cwd": "${workspaceRoot}",
 			"valuesFormatting": "parseText",
-			"preLaunchTask": "Build",
+			"preLaunchTask": "Build Debug",
+			"internalConsoleOptions": "openOnSessionStart",
 		},
+
 		{
 			"name": "Test",
 			"type": "gdb",
 			"request": "launch",
-			"target": "${workspaceFolder}/zig-cache/o/b57ef32c79a05339fbe4a8eb648ff6df/test",
+			"target": "${workspaceFolder}/zig-out/bin/test",
 			"arguments": "main.zig",
 			"cwd": "${workspaceRoot}",
 			"valuesFormatting": "parseText",
-			"preLaunchTask": "Build Test",
+			"preLaunchTask": "Build Debug",
+			"internalConsoleOptions": "openOnSessionStart",
 		},
 	]
 }

.vscode/settings.json

@@ -14,4 +14,5 @@
 
     "git.detectSubmodulesLimit": 0,
     "git.ignoreSubmodules": true,
+    "debug.onTaskErrors": "showErrors",
 }

.vscode/tasks.json

@@ -1,60 +1,40 @@
 {
 	"version": "2.0.0",
 
+	"problemMatcher": {
+		"source": "zig",
+		"owner": "cpptools",
+
+		"fileLocation": [
+			"autoDetect",
+			"${cwd}",
+		],
+
+		"pattern": {
+			"regexp": "^(.*?):(\\d+):(\\d*):?\\s+(?:fatal\\s+)?(warning|error):\\s+(.*)$",
+			"file": 1,
+			"line": 2,
+			"column": 3,
+			"severity": 4,
+			"message": 5,
+		}
+	},
+
 	"tasks": [
 		{
-			"label": "Build",
+			"label": "Build Debug",
 			"type": "shell",
 			"command": "zig build",
-
+			"group": "build",
-			"group": {
-				"kind": "build",
-				"isDefault": true
-			},
-
 			"presentation": {
 				"echo": true,
-				"reveal": "always",
+				"reveal": "silent",
 				"focus": true,
 				"panel": "shared",
 				"showReuseMessage": true,
 				"clear": true,
 				"revealProblems": "onProblem",
 			},
-
-			"problemMatcher": {
-				"source": "gcc",
-				"owner": "cpptools",
-
-				"fileLocation": [
-					"autoDetect",
-					"${cwd}",
-				],
-
-				"pattern": {
-					"regexp": "^(.*?):(\\d+):(\\d*):?\\s+(?:fatal\\s+)?(warning|error):\\s+(.*)$",
-					"file": 1,
-					"line": 2,
-					"column": 3,
-					"severity": 4,
-					"message": 5,
-				}
-			}
-		},
-		{
-			"label": "Test",
-			"type": "shell",
-			"command": "$(find zig-cache -name test) src/main.zig",
-			"group": {
-				"kind": "test",
-				"isDefault": true
-			},
-		},
-		{
-			"label": "Build Test",
-			"type": "shell",
-			"command": "zig build test",
-			"group": "test"
 		},
 	],
 }

build.zig

@@ -1,34 +1,45 @@
 const std = @import("std");
 
+///
+/// Builds the engine, tools, and dependencies of all.
+///
 pub fn build(builder: *std.build.Builder) void {
     const target = builder.standardTargetOptions(.{});
     const mode = builder.standardReleaseOptions();
+    const core_pkg = projectPkg("core", &.{});
 
     // Ona executable.
     {
-        const ona_exe = builder.addExecutable("ona", "./src/main.zig");
+        const ona = builder.addExecutable("ona", "./src/ona/main.zig");
 
-        ona_exe.setTarget(target);
+        ona.addPackage(core_pkg);
-        ona_exe.setBuildMode(mode);
+        ona.setTarget(target);
-        ona_exe.install();
+        ona.setBuildMode(mode);
-        ona_exe.addIncludeDir("./ext");
+        ona.install();
-        ona_exe.linkSystemLibrary("SDL2");
+        ona.addIncludeDir("./ext");
-
+        ona.linkSystemLibrary("SDL2");
-        const run_cmd = ona_exe.run();
+        ona.linkLibC();
-
-        run_cmd.step.dependOn(builder.getInstallStep());
-
-        if (builder.args) |args| run_cmd.addArgs(args);
-
-        builder.step("run", "Run Ona application").dependOn(&run_cmd.step);
     }
 
-    // Ona tests.
+    // Tests executable.
     {
-        const ona_tests = builder.addTestExe("test", "./src/main.zig");
+        const tests = builder.addTestExe("test", "./src/tests.zig");
 
-        ona_tests.setTarget(target);
+        tests.addPackage(core_pkg);
-        ona_tests.setBuildMode(mode);
+        tests.setTarget(target);
-        builder.step("test", "Run Ona unit tests").dependOn(&ona_tests.step);
+        tests.setBuildMode(mode);
+        tests.install();
     }
 }
+
+///
+/// Returns a [std.build.Pkg] within the project codebase path at `name` with `dependencies` as its
+/// dependencies.
+///
+fn projectPkg(comptime name: []const u8, dependencies: []const std.build.Pkg) std.build.Pkg {
+    return std.build.Pkg{
+        .name = name,
+        .path = .{.path = "./src/" ++ name ++ "/main.zig"},
+        .dependencies = dependencies,
+    };
+}

src/core/io.zig

@@ -0,0 +1,594 @@
+const math = @import("./math.zig");
+const meta = @import("./meta.zig");
+const stack = @import("./stack.zig");
+const testing = @import("./testing.zig");
+
+///
+/// [AccessError.Inacessible] is a generic catch-all for IO resources that are inaccessible for
+/// implementation-specific reasons.
+///
+pub const AccessError = error {
+    Inaccessible,
+};
+
+///
+/// [AllocationError.OutOfMemory] if the requested amount of memory could not be allocated.
+///
+pub const AllocationError = error {
+    OutOfMemory,
+};
+
+///
+/// Memory layout description for a memory allocation.
+///
+pub const AllocationLayout = struct {
+    length: usize,
+    alignment: u29 = 8,
+};
+
+///
+/// Interface for dynamic memory allocation through the state machine of the wrapped allocator
+/// implementation.
+///
+pub const Allocator = struct {
+    context: *anyopaque,
+
+    vtable: *const struct {
+        alloc: fn (*anyopaque, AllocationLayout) AllocationError![*]u8,
+        dealloc: fn (*anyopaque, [*]u8) void,
+        realloc: fn (*anyopaque, [*]u8, AllocationLayout) AllocationError![*]u8,
+    },
+
+    ///
+    /// Attempts to allocate a block of memory from `allocator` according to `layout`, returning it
+    /// or [AllocationError] if it failed.
+    ///
+    pub fn alloc(allocator: Allocator, layout: AllocationLayout) AllocationError![*]u8 {
+        return allocator.vtable.alloc(allocator.context, layout);
+    }
+
+    ///
+    /// Deallocates the block of memory from `allocator` referenced by `allocation`.
+    ///
+    pub fn dealloc(allocator: Allocator, allocation: [*]u8) void {
+        allocator.vtable.dealloc(allocator.context, allocation);
+    }
+
+    ///
+    /// Attempts to reallocate the existing block of memory from `allocator` referenced by
+    /// `allocation` according to `layout`, returning it or [AllocationError] if it failed.
+    ///
+    pub fn realloc(allocator: Allocator, allocation: [*]u8,
+        layout: AllocationLayout) AllocationError![*]u8 {
+
+        return allocator.vtable.realloc(allocator.context, allocation, layout);
+    }
+
+    ///
+    /// Wraps `implementation`, returning the [Allocator] value.
+    ///
+    pub fn wrap(implementation: anytype) Allocator {
+        const Implementation = @TypeOf(implementation.*);
+
+        return .{
+            .context = @ptrCast(*anyopaque, implementation),
+
+            .vtable = switch (@typeInfo(Implementation)) {
+                .Struct => &.{
+                    .alloc = struct {
+                        fn call(context: *anyopaque, layout: AllocationLayout) AllocationError![*]u8 {
+                            return @ptrCast(*Implementation, @alignCast(
+                                @alignOf(Implementation), context)).alloc(layout);
+                        }
+                    }.call,
+
+                    .dealloc = struct {
+                        fn call(context: *anyopaque, allocation: [*]u8) void {
+                            return @ptrCast(*Implementation, @alignCast(
+                                @alignOf(Implementation), context)).dealloc(allocation);
+                        }
+                    }.call,
+
+                    .realloc = struct {
+                        fn call(context: *anyopaque, allocation: [*]u8,
+                            layout: AllocationLayout) AllocationError![*]u8 {
+
+                            return @ptrCast(*Implementation, @alignCast(
+                                @alignOf(Implementation), context)).realloc(allocation, layout);
+                        }
+                    }.call,
+                },
+
+                .Opaque => &.{
+                    .alloc = struct {
+                        fn call(context: *anyopaque, layout: AllocationLayout) AllocationError![*]u8 {
+                            return @ptrCast(*Implementation, context).alloc(layout);
+                        }
+                    }.call,
+
+                    .dealloc = struct {
+                        fn call(context: *anyopaque, allocation: [*]u8) void {
+                            return @ptrCast(*Implementation, context).dealloc(allocation);
+                        }
+                    }.call,
+
+                    .realloc = struct {
+                        fn call(context: *anyopaque, allocation: [*]u8,
+                            layout: AllocationLayout) AllocationError![*]u8 {
+
+                            return @ptrCast(*Implementation, context).realloc(allocation, layout);
+                        }
+                    }.call,
+                },
+
+                else => @compileError(
+                    "`context` must a single-element pointer referencing a struct or opaque type"),
+            },
+        };
+    }
+};
+
+///
+/// Returns a state machine for lazily computing all `Element` components of a given source input
+/// that match a delimiting pattern.
+///
+pub fn Spliterator(comptime Element: type) type {
+    return struct {
+        source: []const Element,
+        delimiter: []const Element,
+
+        const Self = @This();
+
+        ///
+        /// Returns `true` if there is more data to be processed, otherwise `false`.
+        ///
+        pub fn hasNext(self: Self) bool {
+            return (self.source.len != 0);
+        }
+
+        ///
+        /// Iterates on `self` and returns the next view of [Spliterator.source] that matches
+        /// [Spliterator.delimiter], or `null` if there is no more data to be processed.
+        ///
+        pub fn next(self: *Self) ?[]const Element {
+            if (!self.hasNext()) return null;
+
+            if (self.delimiter.len == 0) {
+                defer self.source = self.source[self.source.len .. self.source.len];
+
+                return self.source[0 .. self.source.len];
+            }
+
+            if (findFirstOf(Element, self.source, self.delimiter, struct {
+                fn testEquality(this: Element, that: Element) bool {
+                    return this == that;
+                }
+            }.testEquality)) |head| {
+                defer self.source = self.source[(head + self.delimiter.len) .. self.source.len];
+
+                return self.source[0 .. head];
+            }
+
+            defer self.source = self.source[self.source.len .. self.source.len];
+
+            return self.source;
+        }
+    };
+}
+
+test "Spliterator(u8)" {
+    // Empty source.
+    {
+        var spliterator = Spliterator(u8){
+            .source = "",
+            .delimiter = " ",
+        };
+
+        try testing.expect(!spliterator.hasNext());
+    }
+
+    // Empty delimiter.
+    {
+        var spliterator = Spliterator(u8){
+            .source = "aaa",
+            .delimiter = "",
+        };
+
+        try testing.expect(spliterator.hasNext());
+        try testing.expect(equals(u8, spliterator.next().?, "aaa"));
+        try testing.expect(!spliterator.hasNext());
+    }
+
+    // Single-character delimiter.
+    {
+        var spliterator = Spliterator(u8){
+            .source = "single.character.separated.hello.world",
+            .delimiter = ".",
+        };
+
+        const components = [_][]const u8{"single",
+            "character", "separated", "hello", "world"};
+
+        var index = @as(usize, 0);
+        const components_tail = components.len - 1;
+
+        while (spliterator.next()) |split| : (index += 1) {
+            try testing.expect(spliterator.hasNext() == (index < components_tail));
+            try testing.expect(equals(u8, split, components[index]));
+        }
+
+        try testing.expect(!spliterator.hasNext());
+    }
+
+    // Multi-character delimiter.
+    {
+        var spliterator = Spliterator(u8){
+            .source = "finding a needle in a needle stack",
+            .delimiter = "needle",
+        };
+
+        const components = [_][]const u8{"finding a ", " in a ", " stack"};
+        var index = @as(usize, 0);
+        const components_tail = components.len - 1;
+
+        while (spliterator.next()) |split| : (index += 1) {
+            try testing.expect(spliterator.hasNext() == (index < components_tail));
+            try testing.expect(equals(u8, split, components[index]));
+        }
+
+        try testing.expect(!spliterator.hasNext());
+    }
+}
+
+///
+/// Interface for capturing a reference to a writable resource like block devices, memory buffers,
+/// network sockets, and more.
+///
+pub const Writer = struct {
+    context: *anyopaque,
+
+    vtable: *const struct {
+        write: fn (*anyopaque, []const u8) AccessError!usize,
+    },
+
+    ///
+    /// Wraps `implementation`, returning the [Writer] value.
+    ///
+    pub fn wrap(implementation: anytype) Writer {
+        const Implementation = @TypeOf(implementation.*);
+
+        return .{
+            .context = @ptrCast(*anyopaque, implementation),
+
+            .vtable = switch (@typeInfo(Implementation)) {
+                .Struct => &.{
+                    .write = struct {
+                        fn call(context: *anyopaque, buffer: []const u8) AccessError!usize {
+                            return @ptrCast(*Implementation,
+                                @alignCast(@alignOf(Implementation), context)).write(buffer);
+                        }
+                    }.call,
+                },
+
+                .Opaque => &.{
+                    .write = struct {
+                        fn call(context: *anyopaque, buffer: []const u8) AccessError!usize {
+                            return @ptrCast(*Implementation, context).write(buffer);
+                        }
+                    }.call,
+                },
+
+                else => @compileError(
+                    "`context` must a single-element pointer referencing a struct or opaque type"),
+            },
+        };
+    }
+
+    ///
+    /// Attempts to write to `buffer` to `writer`, returning the number of successfully written or
+    /// [AccessError] if it failed.
+    ///
+    pub fn write(writer: Writer, buffer: []const u8) AccessError!usize {
+        return writer.vtable.write(writer.context, buffer);
+    }
+};
+
+///
+/// Returns a sliced reference of the raw bytes in `pointer`.
+///
+pub fn bytesOf(pointer: anytype) switch (@typeInfo(@TypeOf(pointer))) {
+    .Pointer => |info| if (info.is_const) []const u8 else []u8,
+    else => @compileError("`pointer` must be a pointer type"),
+} {
+    const Pointer = @TypeOf(pointer);
+    const pointer_info = @typeInfo(Pointer).Pointer;
+
+    switch (pointer_info.size) {
+        .Many => @compileError("`pointer` cannot be an unbound pointer type"),
+        .C => @compileError("`pointer` cannot be a C-style pointer"),
+
+        .One => return @ptrCast(if (pointer_info.is_const) [*]const u8
+                else [*]u8, pointer)[0 .. @sizeOf(Pointer)],
+
+        .Slice => return @ptrCast(if (pointer_info.is_const) [*]const u8 else
+            [*]u8, pointer.ptr)[0 .. (@sizeOf(Pointer) * pointer.len)],
+    }
+}
+
+test "bytesOf" {
+    var foo: u32 = 10;
+
+    try testing.expect(bytesOf(&foo)[0] == 0x0a);
+}
+
+///
+/// Compares `this` to `that`, returning the difference between the first byte deviation in the two
+/// sequences, otherwise `0` if they are identical.
+///
+pub fn compareBytes(this: []const u8, that: []const u8) isize {
+    const range = math.min(usize, this.len, that.len);
+    var index: usize = 0;
+
+    while (index < range) : (index += 1) {
+        const difference = (this[index] - that[index]);
+
+        if (difference != 0) return difference;
+    }
+
+    return (@intCast(isize, this.len) - @intCast(isize, that.len));
+}
+
+test "compareBytes" {
+    try testing.expect(compareBytes(&.{69, 42, 0}, &.{69, 42, 0}) == 0);
+    try testing.expect(compareBytes(&.{69, 42, 11}, &.{69, 42}) == 1);
+    try testing.expect(compareBytes(&.{69, 42}, &.{69, 42, 11}) == -1);
+}
+
+///
+/// Copies the contents of `source` into `target`
+///
+pub fn copy(comptime Element: type, target: []Element, source: []const Element) void {
+    for (source) |element, index| target[index] = element;
+}
+
+test "copy" {
+    var buffer = [_]u32{0} ** 20;
+    const data = [_]u32{3, 20, 8000};
+
+    copy(u32, &buffer, &data);
+
+    for (data) |datum, index| try testing.expect(buffer[index] == datum);
+}
+
+///
+/// Returns `true` if `this` is the same length and contains the same data as `that`, otherwise
+/// `false`.
+///
+pub fn equals(comptime Element: type, this: []const Element, that: []const Element) bool {
+    if (this.len != that.len) return false;
+
+    var index: usize = 0;
+
+    while (index < this.len) : (index += 1) if (this[index] != that[index]) return false;
+
+    return true;
+}
+
+test "equals" {
+    const bytes_sequence = &.{69, 42, 0};
+
+    try testing.expect(equals(u8, bytes_sequence, bytes_sequence));
+    try testing.expect(!equals(u8, bytes_sequence, &.{69, 42}));
+}
+
+///
+/// Fills the contents of `target` with `source`.
+///
+pub fn fill(comptime Element: type, target: []Element, source: Element) void {
+    for (target) |_, index| target[index] = source;
+}
+
+test "fill" {
+    var buffer = [_]u32{0} ** 8;
+
+    fill(u32, &buffer, 1);
+
+    for (buffer) |element| try testing.expect(element == 1);
+}
+
+///
+/// Linearly searches for the first instance of an `Element` equal to `needle` in `haystack`,
+/// returning its index or `null` if nothing was found.
+///
+/// **Note** that this operation has `O(n)` time complexity.
+///
+pub fn findFirst(comptime Element: type, haystack: []const Element,
+    needle: Element, comptime testEquality: fn (Element, Element) bool) ?usize {
+
+    for (haystack) |element, index| if (testEquality(element, needle)) return index;
+
+    return null;
+}
+
+test "findFirst" {
+    const haystack = &.{"", "", "foo"};
+
+    const testEquality = struct {
+        fn testEquality(this: []const u8, that: []const u8) bool {
+            return equals(u8, this, that);
+        }
+    }.testEquality;
+
+    try testing.expect(findFirst([]const u8, haystack, "foo", testEquality).? == 2);
+    try testing.expect(findFirst([]const u8, haystack, "bar", testEquality) == null);
+}
+
+///
+/// Searches for the first instance of an `Element` sequence equal to the contents of `needle` in
+/// `haystack`, returning the starting index or `null` if nothing was found.
+///
+/// **Note** that this operation has `O(nm)` time complexity.
+///
+pub fn findFirstOf(comptime Element: type, haystack: []const Element,
+    needle: []const Element, comptime testEquality: fn (Element, Element) bool) ?usize {
+
+    var head: usize = 0;
+    const tail = (haystack.len - needle.len);
+
+    walk_haystack: while (head <= tail) : (head += 1) {
+        for (needle) |element, index|
+            if (!testEquality(haystack[head + index], element)) continue: walk_haystack;
+
+        return head;
+    }
+
+    return null;
+}
+
+test "findFirstOf" {
+    const haystack = &.{"foo", "bar", "baz"};
+
+    const testEquality = struct {
+        fn testEquality(this: []const u8, that: []const u8) bool {
+            return equals(u8, this, that);
+        }
+    }.testEquality;
+
+    try testing.expect(findFirstOf([]const u8, haystack, &.{"bar", "baz"}, testEquality).? == 1);
+    try testing.expect(findFirstOf([]const u8, haystack, &.{"baz", "bar"}, testEquality) == null);
+}
+
+///
+/// Frees `allocated_memory` using `allocator`.
+///
+/// *Note* that only memory known to be freeable by `allocator` should be passed via
+/// `allocated_memory`. Anything else will result is considered unreachable logic.
+///
+pub fn free(allocator: Allocator, allocated_memory: anytype) void {
+    allocator.dealloc(@ptrCast([*]u8, switch (@typeInfo(@TypeOf(allocated_memory))) {
+        .Pointer => |info| switch (info.size) {
+            .One, .Many, .C => allocated_memory,
+            .Slice => allocated_memory.ptr,
+        },
+
+        else => @compileError("`allocated_memory` must be a pointer"),
+    }));
+}
+
+test "free" {
+    var buffer = [_]u8{0} ** 4096;
+    var memory = stack.Fixed(u8){.buffer = &buffer};
+    const fixed_allocator = stack.fixedAllocator(&memory);
+    const block_size = 8;
+    const allocated_block = (try makeMany(u8, fixed_allocator, block_size))[0 .. block_size];
+
+    defer free(fixed_allocator, allocated_block);
+}
+
+///
+/// Returns a deterministic hash code compiled from each byte in `bytes`.
+///
+/// **Note** that this operation has `O(n)` time complexity.
+///
+pub fn hashBytes(bytes: []const u8) usize {
+    var hash = @as(usize, 5381);
+
+    for (bytes) |byte| hash = ((hash << 5) + hash) + byte;
+
+    return hash;
+}
+
+test "hashBytes" {
+    const bytes_sequence = &.{69, 42, 0};
+
+    try testing.expect(hashBytes(bytes_sequence) == hashBytes(bytes_sequence));
+    try testing.expect(hashBytes(bytes_sequence) != hashBytes(&.{69, 42}));
+}
+
+///
+/// Attempts to allocate a buffer of `size` `Element`s using `allocator`, returning it or a
+/// [MakeError] if it failed.
+///
+pub fn makeMany(comptime Element: type, allocator: Allocator, size: usize) AllocationError![*]Element {
+    const alignment = @alignOf(Element);
+
+    return @ptrCast([*]Element, @alignCast(alignment, try allocator.alloc(.{
+        .length = @sizeOf(Element) * size,
+        .alignment = alignment,
+    })));
+}
+
+test "makeMany" {
+    var buffer = [_]u8{0} ** 4096;
+    var memory = stack.Fixed(u8){.buffer = &buffer};
+    const block_size = 8;
+
+    // Don't care about the actual allocation - just assertions about it.
+    _ = (try makeMany(u8, stack.fixedAllocator(&memory), block_size))[0 .. block_size];
+}
+
+///
+/// Attempts to allocate a buffer of `1` `Element` using `allocator`, returning it or a [MakeError]
+/// if it failed.
+///
+pub fn makeOne(comptime Element: type, allocator: Allocator) AllocationError!*Element {
+    const alignment = @alignOf(Element);
+
+    return @ptrCast(*Element, @alignCast(alignment, try allocator.alloc(.{
+        .length = @sizeOf(Element),
+        .alignment = alignment,
+    })));
+}
+
+test "makeOne" {
+    var buffer = [_]u8{0} ** 4096;
+    var memory = stack.Fixed(u8){.buffer = &buffer};
+
+    // Don't care about the actual allocation - just assertions about it.
+    _ = try makeOne(u8, stack.fixedAllocator(&memory));
+}
+
+///
+/// Swaps the `Data` in `this` with `that`.
+///
+pub fn swap(comptime Data: type, this: *Data, that: *Data) void {
+    const temp = this.*;
+    this.* = that.*;
+    that.* = temp;
+}
+
+test "swap" {
+    var a: u64 = 0;
+    var b: u64 = 1;
+
+    swap(u64, &a, &b);
+
+    try testing.expect(a == 1);
+    try testing.expect(b == 0);
+}
+
+///
+/// Mandatory context variable used by [null_writer].
+///
+const null_context: u64 = 0;
+
+///
+/// Thread-safe and lock-free [Writer] that silently consumes all given data without failure and
+/// throws it away.
+///
+/// This is commonly used for testing or redirected otherwise unwanted output data that has to be
+/// sent somewhere for whatever reason.
+///
+pub const null_writer = Writer.wrap(@ptrCast(*const opaque {
+    const Self = @This();
+
+    fn write(_: Self, buffer: []const u8) usize {
+        return buffer.len;
+    }
+}, &null_context));
+
+test "null_writer" {
+    const sequence = "foo";
+
+    try testing.expect(null_writer.call(sequence) == sequence.len);
+}

src/core/main.zig

@@ -0,0 +1,45 @@
+
+///
+/// Platform-agnostic input and output interfaces for working with memory, files, and networks.
+///
+pub const io = @import("./io.zig");
+
+///
+/// Math types and functions with a focus on graphics-specific linear algebra.
+///
+pub const math = @import("./math.zig");
+
+///
+/// Metaprogramming introspection and generation.
+///
+pub const meta = @import("./meta.zig");
+
+///
+/// Sequential, last-in first-out data structures.
+///
+pub const stack = @import("./stack.zig");
+
+///
+/// Unordered key-value association data structures.
+///
+pub const table = @import("./table.zig");
+
+///
+/// Unit testing suite utilities.
+///
+pub const testing = @import("./testing.zig");
+
+///
+/// Unicode-encoded string analysis and processing with a focus on UTF-8 encoded text.
+///
+pub const unicode = @import("./unicode.zig");
+
+test {
+    _ = io;
+    _ = math;
+    _ = meta;
+    _ = stack;
+    _ = table;
+    _ = testing;
+    _ = unicode;
+}

src/core/math.zig

@@ -0,0 +1,61 @@
+const std = @import("std");
+const testing = @import("./testing.zig");
+
+// TODO: Remove stdlib dependency.
+pub const IntFittingRange = std.math.IntFittingRange;
+
+///
+/// Returns the highest integer value representable by `Integer`.
+///
+pub fn maxIntValue(comptime Integer: type) comptime_int {
+    return switch (@typeInfo(Integer)) {
+        .Int => |info| if (info.bits == 0) 0 else
+            ((1 << (info.bits - @boolToInt(info.signedness == .signed))) - 1),
+
+        else => @compileError("`" ++ @typeName(Integer) ++ "` must be an int"),
+    };
+}
+
+test "maxIntValue" {
+    try testing.expect(maxIntValue(u8) == 255);
+    try testing.expect(maxIntValue(i8) == 127);
+
+    try testing.expect(maxIntValue(u16) == 65535);
+    try testing.expect(maxIntValue(i16) == 32767);
+}
+
+///
+/// Returns the highest `Number` value between `this` and `that`.
+///
+pub fn max(comptime Number: type, this: Number, that: Number) Number {
+    return switch (@typeInfo(Number)) {
+        .Int, .Float, .ComptimeInt, .ComptimeFloat => if (this > that) this else that,
+
+        else => @compileError("`" ++ @typeName(Number) ++
+            "` must be an int, float, comptime_int, or comptime_float"),
+    };
+}
+
+test "max" {
+    try testing.expect(max(f32, 0.1, 1.0) == 1.0);
+    try testing.expect(max(f64, 1.0, 1.01) == 1.01);
+    try testing.expect(max(u32, 35615, 2873) == 35615);
+}
+
+///
+/// Returns the lowest `Number` value between `this` and `that`.
+///
+pub fn min(comptime Number: type, this: Number, that: Number) Number {
+    return switch (@typeInfo(Number)) {
+        .Int, .Float, .ComptimeInt, .ComptimeFloat => if (this < that) this else that,
+
+        else => @compileError("`" ++ @typeName(Number) ++
+            "` must be an int, float, comptime_int, or comptime_float"),
+    };
+}
+
+test "min" {
+    try testing.expect(min(f32, 0.1, 1.0) == 0.1);
+    try testing.expect(min(f64, 1.0, 1.01) == 1.0);
+    try testing.expect(min(u32, 35615, 2873) == 2873);
+}

src/core/meta.zig

@@ -0,0 +1,10 @@
+///
+/// Returns the return type of the function type `Fn`.
+///
+pub fn FnReturn(comptime Fn: type) type {
+    const type_info = @typeInfo(Fn);
+
+    if (type_info != .Fn) @compileError("`Fn` must be a function type");
+
+    return type_info.Fn.return_type orelse void;
+}

src/core/stack.zig

@@ -0,0 +1,286 @@
+const io = @import("./io.zig");
+const testing = @import("./testing.zig");
+
+///
+/// Returns a fixed-size stack type of `Element`s.
+///
+pub fn Fixed(comptime Element: type) type {
+    return struct {
+        filled: usize = 0,
+        buffer: []Element,
+
+        ///
+        /// Stack type.
+        ///
+        const Self = @This();
+
+        ///
+        /// Resets the number of filled items to `0`, otherwise leaving the actual memory contents
+        /// of the buffer untouched until it is later overwritten by following operations on it.
+        ///
+        pub fn clear(self: *Self) void {
+            self.filled = 0;
+        }
+
+        ///
+        /// Returns `true` if `self` has filled its buffer to maximum capacity, otherwise `false`.
+        ///
+        pub fn isFull(self: Self) bool {
+            return (self.filled == self.buffer.len);
+        }
+
+        ///
+        /// If `self` is filled with at least `1` value, it is decremented by `1`, otherwise leaving
+        /// the actual memory contents of the buffer untouched until it is later overwritten by
+        /// following operations on it.
+        ///
+        /// The value of the element removed from the list is returned if something existed to be
+        /// popped, otherwise `null` if it contained no elements.
+        ///
+        pub fn pop(self: *Self) ?Element {
+            if (self.filled == 0) return null;
+
+            self.filled -= 1;
+
+            return self.buffer[self.filled];
+        }
+
+        ///
+        /// Attempts to push `element` into `self`, returning a [FixedPushError] if it failed.
+        ///
+        pub fn push(self: *Self, element: Element) FixedPushError!void {
+            if (self.isFull()) return error.BufferOverflow;
+
+            self.buffer[self.filled] = element;
+            self.filled += 1;
+        }
+
+        ///
+        /// Attempts to push all of `elements` into `self`, returning a [FixedPushError] if it
+        /// failed.
+        ///
+        pub fn pushAll(self: *Self, elements: []const Element) FixedPushError!void {
+            const filled = (self.filled + elements.len);
+
+            if (filled > self.buffer.len) return error.BufferOverflow;
+
+            io.copy(Element, self.buffer[self.filled ..], elements);
+
+            self.filled = filled;
+        }
+
+        ///
+        /// Attempts to push `count` instances of `element` into `self`, returning a
+        /// [FixedPushError] if it failed.
+        ///
+        pub fn pushMany(self: *Self, element: Element, count: usize) FixedPushError!void {
+            const filled = (self.filled + count);
+
+            if (filled > self.buffer.len) return error.BufferOverflow;
+
+            io.fill(Element, self.buffer[self.filled ..], element);
+
+            self.filled = filled;
+        }
+    };
+}
+
+test "Fixed([]const u8)" {
+    const default_value = "";
+    var buffer = [_][]const u8{default_value} ** 4;
+    var shopping_list = Fixed([]const u8){.buffer = &buffer};
+
+    // Pop empty stack.
+    {
+        try testing.expect(shopping_list.pop() == null);
+        try testing.expect(shopping_list.filled == 0);
+        try testing.expect(shopping_list.buffer.ptr == &buffer);
+        try testing.expect(shopping_list.buffer.len == buffer.len);
+
+        for (shopping_list.buffer) |item|
+            try testing.expect(io.equals(u8, item, default_value));
+    }
+
+    // Push single element.
+    {
+        try shopping_list.push("milk");
+        try testing.expect(shopping_list.filled == 1);
+        try testing.expect(shopping_list.buffer.ptr == &buffer);
+        try testing.expect(shopping_list.buffer.len == buffer.len);
+        try testing.expect(io.equals(u8, shopping_list.buffer[0], "milk"));
+
+        for (shopping_list.buffer[1 ..]) |item|
+            try testing.expect(io.equals(u8, item, default_value));
+
+        // TODO: Test stack overflow.
+    }
+
+    // Pop single element.
+    {
+        try testing.expect(io.equals(u8, shopping_list.pop().?, "milk"));
+        try testing.expect(shopping_list.filled == 0);
+        try testing.expect(shopping_list.buffer.ptr == &buffer);
+        try testing.expect(shopping_list.buffer.len == buffer.len);
+        try testing.expect(io.equals(u8, shopping_list.buffer[0], "milk"));
+
+        for (shopping_list.buffer[1 ..]) |item|
+            try testing.expect(io.equals(u8, item, default_value));
+    }
+
+    // TODO: Multiple elements.
+    // TODO: Clear elements.
+}
+
+///
+/// Potential errors that may occur while trying to push one or more elements into a [Fixed] stack.
+///
+pub const FixedPushError = error {
+    BufferOverflow,
+};
+
+///
+/// Creates and returns a [io.Allocator] value wrapping `fixed_stack`.
+///
+/// The returned [io.Allocator] uses `fixed_stack` and its backing memory buffer as a fixed-length
+/// memory pool to linearly allocate memory from.
+///
+pub fn fixedAllocator(fixed_stack: *Fixed(u8)) io.Allocator {
+    const FixedStack = @TypeOf(fixed_stack.*);
+
+    return io.Allocator.wrap(@ptrCast(*opaque {
+        const Self = @This();
+
+        pub fn alloc(self: *Self, layout: io.AllocationLayout) io.AllocationError![*]u8 {
+            // TODO: Remove stdlib dependency.
+            const stack = self.stackCast();
+
+            const adjusted_offset = @import("std").mem.alignPointerOffset(stack.buffer.ptr +
+                stack.filled, layout.alignment) orelse return error.OutOfMemory;
+
+            const head = stack.filled + adjusted_offset;
+            const tail = head + layout.length;
+
+            stack.pushMany(0, tail) catch return error.OutOfMemory;
+
+            return stack.buffer[head .. tail].ptr;
+        }
+
+        pub fn dealloc(self: *Self, allocation: [*]u8) void {
+            // Deallocate the memory.
+            const stack = self.stackCast();
+            const allocation_address = @ptrToInt(allocation);
+            const stack_address = @ptrToInt(stack.buffer.ptr);
+
+            // Check the buffer is within the address space of the stack buffer. If not, it cannot
+            // be freed.
+            if (allocation_address < stack_address or allocation_address >=
+                (stack_address + stack.filled)) unreachable;
+
+            // TODO: Investigate ways of actually freeing if it is the last allocation.
+        }
+
+        pub fn realloc(self: *Self, allocation: [*]u8,
+            layout: io.AllocationLayout) io.AllocationError![*]u8 {
+
+            // TODO: Investigate ways of in-place relocating if it is the last allocation.
+            // TODO: Remove stdlib dependency.
+            const stack = self.stackCast();
+            const allocation_address = @ptrToInt(allocation);
+            const stack_address = @ptrToInt(stack.buffer.ptr);
+
+            // Check the buffer is within the address space of the stack buffer. If not, it cannot
+            // be reallocated.
+            if (allocation_address < stack_address or allocation_address >=
+                (stack_address + stack.filled)) unreachable;
+
+            const adjusted_offset = @import("std").mem.alignPointerOffset(stack.buffer.ptr +
+                stack.filled, layout.alignment) orelse return error.OutOfMemory;
+
+            const head = stack.filled + adjusted_offset;
+            const tail = head + layout.length;
+
+            stack.pushMany(0, tail) catch return error.OutOfMemory;
+
+            return stack.buffer[head .. tail].ptr;
+        }
+
+        fn stackCast(self: *Self) *Fixed(u8) {
+            return @ptrCast(*FixedStack, @alignCast(@alignOf(FixedStack), self));
+        }
+    }, fixed_stack));
+}
+
+test "fixedAllocator" {
+    var buffer = [_]u8{0} ** 32;
+    var stack = Fixed(u8){.buffer = &buffer};
+    const allocator = fixedAllocator(&stack);
+
+    // Allocation
+    var block_memory = try allocator.alloc(.{
+        .alignment = @alignOf(u64),
+        .length = @sizeOf(u64),
+    });
+
+    const buffer_address_head = @ptrToInt(&buffer);
+    const buffer_address_tail = @ptrToInt(&buffer) + buffer.len;
+
+    {
+        const block_memory_address = @ptrToInt(block_memory);
+
+        try testing.expect(block_memory_address >= buffer_address_head and
+            block_memory_address < buffer_address_tail);
+    }
+
+    // Reallocation.
+    block_memory = try allocator.realloc(block_memory, .{
+        .alignment = @alignOf(u64),
+        .length = @sizeOf(u64),
+    });
+
+    {
+        const block_memory_address = @ptrToInt(block_memory);
+
+        try testing.expect(block_memory_address >= buffer_address_head and
+            block_memory_address < buffer_address_tail);
+    }
+
+    // Deallocation.
+    allocator.dealloc(block_memory);
+}
+
+///
+/// Returns an [io.Writer] wrapping `fixed_stack`.
+///
+/// Writing to the returned [io.Writer] will push values to the underlying [Fixed] stack instance
+/// referenced by `fixed_stack` until it is full.
+///
+pub fn fixedWriter(fixed_stack: *Fixed(u8)) io.Writer {
+    const FixedStack = @TypeOf(fixed_stack.*);
+
+    return io.Writer.wrap(@ptrCast(*opaque {
+        const Self = @This();
+
+        fn stackCast(self: *Self) *Fixed(u8) {
+            return @ptrCast(*FixedStack, @alignCast(@alignOf(FixedStack), self));
+        }
+
+        pub fn write(self: *Self, buffer: []const u8) io.AccessError!usize {
+            self.stackCast().pushAll(buffer) catch |err| switch (err) {
+                error.BufferOverflow => return 0,
+            };
+
+            return buffer.len;
+        }
+    }, fixed_stack));
+}
+
+test "fixedWriter" {
+    var buffer = [_]u8{0} ** 4;
+    var sequence_stack = Fixed(u8){.buffer = &buffer};
+    const sequence_data = [_]u8{8, 16, 32, 64};
+
+    try testing.expect((try fixedWriter(&sequence_stack).
+        write(&sequence_data)) == sequence_data.len);
+
+    try testing.expect(io.equals(u8, sequence_stack.buffer, &sequence_data));
+}

src/core/table.zig

@@ -0,0 +1,221 @@
+const io = @import("./io.zig");
+const stack = @import("./stack.zig");
+const testing = @import("./testing.zig");
+
+///
+/// Returns a hash-backed table type of `Value`s indexed by `Key` and using `key_context` as the key
+/// context.
+///
+pub fn Hashed(comptime Key: type, comptime Value: type,
+    comptime key_context: KeyContext(Key)) type {
+
+    const Allocator = io.Allocator;
+
+    return struct {
+        allocator: Allocator,
+        load_limit: f32,
+        buckets: []Bucket,
+        filled: usize,
+
+        ///
+        /// A slot in the hash table.
+        ///
+        const Bucket = struct {
+            maybe_entry: ?struct {
+                key: Key,
+                value: Value,
+            } = null,
+
+            maybe_next_index: ?usize = null,
+        };
+
+        ///
+        /// Errors that may occur during initialization of a hash table.
+        ///
+        pub const InitError = io.AllocationError;
+
+        ///
+        /// Hash table type.
+        ///
+        const Self = @This();
+
+        ///
+        /// Deinitializes `self`, preventing any further use.
+        ///
+        pub fn deinit(self: *Self) void {
+            io.free(self.allocator, self.buckets);
+
+            self.buckets = &.{};
+        }
+
+        ///
+        /// Initializes a [Self] using `allocator` as the memory allocation strategy.
+        ///
+        /// Returns a new [Self] value or an [InitError] if initializing failed.
+        ///
+        pub fn init(allocator: Allocator) InitError!Self {
+            const capacity = 4;
+
+            return Self{
+                .buckets = (try io.makeMany(Bucket, allocator, capacity))[0 .. capacity],
+                .filled = 0,
+                .allocator = allocator,
+                .load_limit = 0.75,
+            };
+        }
+
+        ///
+        /// Searches for `key` and deletes it from `self.
+        ///
+        /// The removed value is returned or `null` if no key matching `key` was found.
+        ///
+        pub fn remove(self: *Self, key: Key) ?Value {
+            var bucket = &(self.buckets[@mod(key_context.hash(key), self.buckets.len)]);
+
+            if (bucket.maybe_entry) |*entry| if (key_context.equals(entry.key, key)) {
+                defer {
+                    bucket.maybe_entry = null;
+                    self.filled -= 1;
+                }
+
+                return entry.value;
+            };
+
+            while (bucket.maybe_next_index) |index| {
+                bucket = &(self.buckets[index]);
+
+                if (bucket.maybe_entry) |*entry| if (key_context.equals(entry.key, key)) {
+                    defer {
+                        bucket.maybe_entry = null;
+                        self.filled -= 1;
+                    }
+
+                    return entry.value;
+                };
+            }
+
+            return null;
+        }
+
+        ///
+        /// Attempts to insert the value at `key` to be `value` in `self`, returning an
+        /// [InsertError] if it fails.
+        ///
+        pub fn insert(self: *Self, key: Key, value: Value) InsertError!void {
+            if (self.isOverloaded()) {
+                const old_buckets = self.buckets;
+
+                defer io.free(self.allocator, old_buckets);
+
+                const bucket_count = old_buckets.len * 2;
+
+                self.buckets = (try io.makeMany(Bucket, self.allocator,
+                    bucket_count))[0 .. bucket_count];
+
+                for (old_buckets) |bucket, index| self.buckets[index] = bucket;
+            }
+
+            var hash = @mod(key_context.hash(key), self.buckets.len);
+
+            while (true) {
+                const bucket = &(self.buckets[hash]);
+
+                if (key_context.equals((bucket.maybe_entry orelse {
+                    bucket.maybe_entry = .{
+                        .key = key,
+                        .value = value
+                    };
+
+                    self.filled += 1;
+
+                    break;
+                }).key, key)) return error.KeyExists;
+
+                hash = @mod(hash + 1, self.buckets.len);
+            }
+        }
+
+        ///
+        /// Returns `true` if the current load factor, derived from the number of elements filling
+        /// the bucket table, is greater than the current load limit.
+        ///
+        pub fn isOverloaded(self: Self) bool {
+            return (@intToFloat(f32, self.filled) /
+                @intToFloat(f32, self.buckets.len)) >= self.load_limit;
+        }
+
+        ///
+        /// Searches for a value indexed with `key` in `self`.
+        ///
+        /// The found value is returned or `null` if any key matching `key` failed to be found.
+        ///
+        pub fn lookup(self: Self, key: Key) ?Value {
+            var bucket = &(self.buckets[@mod(key_context.hash(key), self.buckets.len)]);
+
+            if (bucket.maybe_entry) |entry|
+                if (key_context.equals(entry.key, key)) return entry.value;
+
+            while (bucket.maybe_next_index) |index| {
+                bucket = &(self.buckets[index]);
+
+                if (bucket.maybe_entry) |entry|
+                    if (key_context.equals(entry.key, key)) return entry.value;
+            }
+
+            return null;
+        }
+    };
+}
+
+///
+/// [InsertError.KeyExists] occurs when an insertion was attempted on a table with a matching key
+/// already present.
+///
+pub const InsertError = io.AllocationError || error {
+    KeyExists,
+};
+
+///
+/// Returns a context type for handling `Key` as a key in a table, associating hashing and equality
+/// behaviors to it.
+///
+pub fn KeyContext(comptime Key: type) type {
+    return struct {
+        hash: fn (Key) usize,
+        equals: fn (Key, Key) bool,
+    };
+}
+
+///
+/// A [KeyContext] for dealing with string literal (i.e. []const u8) values.
+///
+/// **Note** that, while lightweight, this context should only be considered safe to use with string
+/// literals or variables pointing to string literals - as the [KeyContext] does not take ownership
+/// of its keys beyond copying the reference.
+///
+pub const string_literal_context = KeyContext([]const u8){
+    .hash = io.hashBytes,
+
+    .equals = struct {
+        fn stringsEqual(this: []const u8, that: []const u8) bool {
+            return io.equals(u8, this, that);
+        }
+    }.stringsEqual,
+};
+
+test "Hashed([]const u8, u32, string_literal_context)" {
+    var buffer = [_]u8{0} ** 4096;
+    var memory = stack.Fixed(u8){.buffer = &buffer};
+
+    var table = try Hashed([]const u8, u32, string_literal_context).
+        init(stack.fixedAllocator(&memory));
+
+    defer table.deinit();
+
+    const foo = 69;
+
+    try testing.expect(table.remove("foo") == null);
+    try table.insert("foo", foo);
+    try testing.expect(table.remove("foo").? == foo);
+    try testing.expect(table.remove("foo") == null);
+}

src/core/testing.zig

@@ -0,0 +1,22 @@
+///
+/// [TestError.UnexpectedResult] occurs when a conditional that should have been `true` was actually
+/// `false`.
+///
+pub const TestError = error {
+    UnexpectedResult,
+};
+
+///
+/// Returns a [TestError] if `ok` is false.
+///
+pub fn expect(ok: bool) TestError!void {
+    if (!ok) return error.UnexpectedResult;
+}
+
+test "expect" {
+    try expect(true);
+
+    expect(false) catch {};
+}
+
+pub const expectError = @import("std").testing.expectError;

src/core/unicode.zig

@@ -0,0 +1,119 @@
+const io = @import("./io.zig");
+const math = @import("./math.zig");
+const stack = @import("./stack.zig");
+const testing = @import("./testing.zig");
+
+///
+/// [PrintError.WriteFailure] occurs when the underlying [io.Writer] implementation failed to write
+/// the entirety of a the requested print operation.
+///
+pub const PrintError = io.AccessError || error {
+    WriteFailure,
+};
+
+///
+/// Named identifiers for number formats used in printing functions.
+///
+pub const Radix = enum {
+    binary,
+    tinary,
+    quaternary,
+    quinary,
+    senary,
+    septenary,
+    octal,
+    nonary,
+    decimal,
+    undecimal,
+    duodecimal,
+    tridecimal,
+    tetradecimal,
+    pentadecimal,
+    hexadecimal,
+
+    ///
+    /// Returns the base number of `radix`.
+    ///
+    pub fn base(radix: Radix) u8 {
+        return switch (radix) {
+            .binary => 2,
+            .tinary => 3,
+            .quaternary => 4,
+            .quinary => 5,
+            .senary => 6,
+            .septenary => 7,
+            .octal => 8,
+            .nonary => 9,
+            .decimal => 10,
+            .undecimal => 11,
+            .duodecimal => 12,
+            .tridecimal => 13,
+            .tetradecimal => 14,
+            .pentadecimal => 15,
+            .hexadecimal => 16,
+        };
+    }
+};
+
+///
+/// Writes `value` as a ASCII / UTF-8 encoded integer to `writer`, returning `true` if the full
+/// sequence was successfully written, otherwise `false`.
+///
+/// The `radix` argument identifies which base system to format `value` as.
+///
+pub fn printInt(writer: io.Writer, radix: Radix, value: anytype) PrintError!void {
+    const Int = @TypeOf(value);
+
+    switch (@typeInfo(Int)) {
+        .Int => |info| {
+            if (value == 0) {
+                const zero = "0";
+
+                if ((try writer.write(zero)) != zero.len) return error.WriteFailure;
+            } else {
+                // Big enough to hold the hexadecimal representation of the integer type, which is
+                // the largest number format accomodated for in [Radix].
+                var buffer = [_]u8{0} ** (@sizeOf(Int) * (@bitSizeOf(u8) / 4));
+                var buffer_count: usize = 0;
+                var n1 = value;
+
+                if (info.signedness == .signed and value < 0) {
+                    // Negative value.
+                    n1 = -value;
+                    buffer[0] = '-';
+                    buffer_count += 1;
+                }
+
+                while (n1 != 0) {
+                    const base = radix.base();
+
+                    buffer[buffer_count] = @intCast(u8, (n1 % base) + '0');
+                    n1 = (n1 / base);
+                    buffer_count += 1;
+                }
+
+                for (buffer[0 .. (buffer_count / 2)]) |_, i|
+                    io.swap(u8, &buffer[i], &buffer[buffer_count - i - 1]);
+
+                if ((try writer.write(buffer[0 .. buffer_count])) != buffer_count)
+                    return error.WriteFailure;
+            }
+        },
+
+        // Cast comptime int into known-size integer and try again.
+        .ComptimeInt => return printInt(writer, radix,
+            @intCast(math.IntFittingRange(value, value), value)),
+
+        else => @compileError("`value` must be of type int or comptime_int"),
+    }
+}
+
+test "printInt" {
+    // Max digits to represent a decimal u8 is 3 (i.e. 127 / 255).
+    var decimal_buffer = [_]u8{0} ** 3;
+    var decimal_stack = stack.Fixed(u8){.buffer = &decimal_buffer};
+    var decimal_writer = stack.fixedWriter(&decimal_stack);
+
+    try printInt(decimal_writer, .decimal, 365);
+    try testing.expect(decimal_stack.isFull());
+}

src/io.zig

@@ -1,148 +0,0 @@
-const stack = @import("./stack.zig");
-const std = @import("std");
-
-///
-/// Opaque interface to a "writable" resource, such as a block device, memory buffer, or network
-/// socket.
-///
-pub const Writer = struct {
-    context: *anyopaque,
-    writeContext: fn (*anyopaque, []const u8) usize,
-
-    ///
-    /// Radices supported by [writeInt].
-    ///
-    pub const Radix = enum {
-        binary,
-        tinary,
-        quaternary,
-        quinary,
-        senary,
-        septenary,
-        octal,
-        nonary,
-        decimal,
-        undecimal,
-        duodecimal,
-        tridecimal,
-        tetradecimal,
-        pentadecimal,
-        hexadecimal,
-    };
-
-    ///
-    /// Wraps and returns a reference to `write_context` of type `WriteContext` and its associated
-    /// `writeContext` writing operation in a [Writer].
-    ///
-    pub fn wrap(
-        comptime WriteContext: type,
-        write_context: *WriteContext,
-        comptime writeContext: fn (*WriteContext, []const u8) usize
-    ) Writer {
-        return .{
-            .context = write_context,
-
-            .writeContext = struct {
-                fn write(context: *anyopaque, buffer: []const u8) usize {
-                    return writeContext(@ptrCast(*WriteContext,
-                        @alignCast(@alignOf(WriteContext), context)), buffer);
-                }
-            }.write,
-        };
-    }
-
-    ///
-    /// Attempts to write `buffer` to `writer`, returning the number of bytes from `buffer` that
-    /// were successfully written.
-    ///
-    pub fn write(writer: Writer, buffer: []const u8) usize {
-        return writer.writeContext(writer.context, buffer);
-    }
-
-    ///
-    /// Writes the singular `byte` to `writer`, returning `true` if it was successfully written,
-    /// otherwise `false`.
-    ///
-    pub fn writeByte(writer: Writer, byte: u8) bool {
-        return (writer.writeContext(writer.context,
-            @ptrCast([*]const u8, &byte)[0 .. 1]) != 0);
-    }
-
-    ///
-    /// Writes `value` as a ASCII / UTF-8 encoded integer to `writer`, returning `true` if the full
-    /// sequence was successfully written, otherwise `false`.
-    ///
-    /// The `radix` argument identifies which base system to encode `value` as, with `10` being
-    /// decimal, `16` being hexadecimal, `8` being octal`, so on and so forth.
-    ///
-    pub fn writeInt(writer: Writer, radix: Radix, value: anytype) bool {
-        const Int = @TypeOf(value);
-        const type_info = @typeInfo(Int);
-
-        switch (type_info) {
-            .Int => {
-                if (value == 0) return writer.writeByte('0');
-
-                // TODO: Unhardcode this as it will break with large ints.
-                var buffer = std.mem.zeroes([28]u8);
-                var buffer_count = @as(usize, 0);
-                var n1 = value;
-
-                if ((type_info.Int.signedness == .signed) and (value < 0)) {
-                    // Negative value.
-                    n1 = -value;
-                    buffer[0] = '-';
-                    buffer_count += 1;
-                }
-
-                while (n1 != 0) {
-                    const base = @enumToInt(radix);
-
-                    buffer[buffer_count] = @intCast(u8, (n1 % base) + '0');
-                    n1 = (n1 / base);
-                    buffer_count += 1;
-                }
-
-                for (buffer[0 .. (buffer_count / 2)]) |_, i|
-                    std.mem.swap(u8, &buffer[i], &buffer[buffer_count - i - 1]);
-
-                return (writer.write(buffer[0 .. buffer_count]) == buffer_count);
-            },
-
-            // Cast comptime int into known-size integer and try again.
-            .ComptimeInt => return writer.
-                writeInt(radix, @intCast(std.math.IntFittingRange(value, value), value)),
-
-            else => @compileError("value must be of type int"),
-        }
-    }
-};
-
-///
-/// Writer that silently throws consumed data away and never fails.
-///
-/// This is commonly used for testing or redirected otherwise unwanted output data that can't not be
-/// sent somewhere for whatever reason.
-///
-pub const null_writer = Writer{
-    .context = undefined,
-
-    .writeContext = struct {
-        fn write(_: *anyopaque, buffer: []const u8) usize {
-            return buffer.len;
-        }
-    }.write,
-};
-
-test {
-    const testing = std.testing;
-
-    {
-        const sequence = "foo";
-
-        try testing.expectEqual(null_writer.write(sequence), sequence.len);
-    }
-
-    try testing.expect(null_writer.writeByte(0));
-    try testing.expect(null_writer.writeInt(.decimal, 420));
-}

src/main.zig

@@ -1,50 +0,0 @@
-const ext = @cImport({
-    @cInclude("SDL2/SDL.h");
-});
-
-const io = @import("./io.zig");
-const stack = @import("./stack.zig");
-const std = @import("std");
-const sys = @import("./sys.zig");
-
-///
-/// Entry point.
-///
-pub fn main() anyerror!void {
-    return sys.runGraphics(anyerror, run);
-}
-
-test {
-    _ = io;
-    _ = stack;
-    _ = std;
-    _ = sys;
-}
-
-fn run(event_loop: *sys.EventLoop, graphics: *sys.GraphicsContext) anyerror!void {
-    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
-
-    defer _ = gpa.deinit();
-
-    {
-        const file_access = try event_loop.open(.readonly,
-            try sys.FileSystem.data.joinedPath(&.{"data", "ona.lua"}));
-
-        defer event_loop.close(file_access);
-
-        const file_size = try file_access.size(event_loop);
-        const allocator = gpa.allocator();
-        const buffer = try allocator.alloc(u8, file_size);
-
-        defer allocator.free(buffer);
-
-        if ((try event_loop.readFile(file_access, buffer)) != file_size)
-            return error.ScriptLoadFailure;
-
-        event_loop.log(.debug, buffer);
-    }
-
-    while (graphics.poll()) |_| {
-        graphics.present();
-    }
-}

src/mem.zig

@@ -1,87 +0,0 @@
-const std = @import("std");
-
-///
-/// State machine for lazily computing all components of [Spliterator.source] that match the pattern
-/// in [Spliterator.delimiter].
-///
-pub fn Spliterator(comptime Element: type) type {
-    return struct {
-        source: []const Element,
-        delimiter: []const Element,
-
-        const Self = @This();
-
-        ///
-        /// Returns `true` if there is more data to be processed, otherwise `false`.
-        ///
-        pub fn hasNext(self: Self) bool {
-            return (self.source.len != 0);
-        }
-
-        ///
-        /// Iterates on `self` and returns the next view of [Spliterator.source] that matches
-        /// [Spliterator.delimiter], or `null` if there is no more data to be processed.
-        ///
-        pub fn next(self: *Self) ?[]const Element {
-            if (!self.hasNext()) return null;
-
-            if (std.mem.indexOfPos(Element, self.source, 0, self.delimiter)) |index| {
-                defer self.source = self.source[(index + self.delimiter.len) .. self.source.len];
-
-                return self.source[0 .. index];
-            }
-
-            defer self.source = self.source[self.source.len .. self.source.len];
-
-            return self.source;
-        }
-    };
-}
-
-test {
-    const testing = std.testing;
-
-    // Single-character delimiter.
-    {
-        var spliterator = Spliterator(u8){
-            .source = "single.character.separated.hello.world",
-            .delimiter = ".",
-        };
-
-        const components = [_][]const u8{"single", "character", "separated", "hello", "world"};
-        var index = @as(usize, 0);
-
-        while (spliterator.next()) |split| : (index += 1) {
-            try testing.expect(std.mem.eql(u8, split, components[index]));
-        }
-    }
-
-    // Multi-character delimiter.
-    {
-        var spliterator = Spliterator(u8){
-            .source = "finding a needle in a needle stack",
-            .delimiter = "needle",
-        };
-
-        const components = [_][]const u8{"finding a ", " in a ", " stack"};
-        var index = @as(usize, 0);
-
-        while (spliterator.next()) |split| : (index += 1) {
-            try testing.expect(std.mem.eql(u8, split, components[index]));
-        }
-    }
-}
-
-///
-/// Searches the slice of `Data` referenced by `data` for the first instance of `sought_datum`,
-/// returning its index or `null` if it could not be found.
-///
-pub fn findFirst(comptime Data: type, data: []const Data, sought_datum: Data) ?usize {
-    for (data) |datum, index| if (datum == sought_datum) return index;
-
-    return null;
-}
-
-test {
-    try std.testing.expectEqual(findFirst(u8, "1234567890", '7'), 6);
-}

src/ona/main.zig

@@ -0,0 +1,40 @@
+const core = @import("core");
+const std = @import("std");
+const sys = @import("./sys.zig");
+
+///
+/// Application entry-point.
+///
+pub fn main() anyerror!void {
+    return nosuspend await async sys.display(anyerror, runEngine);
+}
+
+///
+/// Runs the game engine.
+///
+fn runEngine(app: *sys.App, graphics: *sys.Graphics) anyerror!void {
+    {
+        const path = try sys.Path.from(&.{"ona.lua"});
+        var file_reader = try app.data.openFileReader(path);
+
+        defer file_reader.close();
+
+        const file_size = (try app.data.query(path)).length;
+        const allocator = sys.threadSafeAllocator();
+        const buffer = (try core.io.makeMany(u8, allocator, file_size))[0 .. file_size];
+
+        defer core.io.free(allocator, buffer);
+
+        if ((try file_reader.read(buffer)) != file_size) return error.ScriptLoadFailure;
+
+        app.log(.debug, buffer);
+    }
+
+    while (graphics.poll()) |_| {
+        graphics.present();
+    }
+}
+
+test {
+    _ = sys;
+}

src/ona/oar.zig

@@ -0,0 +1,103 @@
+const core = @import("core");
+const sys = @import("./sys.zig");
+
+///
+/// Metadata of an Oar archive file entry.
+///
+const Entry = extern struct {
+    signature: [signature_magic.len]u8 = signature_magic,
+    path: sys.Path = sys.Path.empty,
+    data_offset: u64 = 0,
+    data_length: u64 = 0,
+    padding: [232]u8 = [_]u8{0} ** 232,
+
+    comptime {
+        const entry_size = @sizeOf(@This());
+
+        if (entry_size != 512) @compileError("EntryBlock is not 512 bytes");
+    }
+};
+
+///
+/// [FindError.ArchiveUnsupported] occurs when trying to read a file that does not follow an Oar
+/// archive format considered valid by this implemenatation.
+///
+/// [FindError.EntryNotFound] occurs when the queried entry was not found in the archive file.
+///
+pub const FindError = core.io.AccessError || error {
+    ArchiveUnsupported,
+    EntryNotFound,
+};
+
+///
+/// Header data that every Oar archive file starts with at byte offset `0`.
+///
+const Header = extern struct {
+    signature: [signature_magic.len]u8 = signature_magic,
+    revision: u8 = revision_magic,
+    entry_count: u32 = 0,
+    padding: [502]u8 = [_]u8{0} ** 502,
+
+    comptime {
+        const size = @sizeOf(@This());
+
+        if (size != 512) @compileError("Header is not 512 bytes");
+    }
+};
+
+///
+/// Attempts to find an [Entry] with a path name matching `path` in `archive_reader`.
+///
+/// An [Entry] value is returned if a match was found, otherwise [FindError] if it failed.
+///
+pub fn findEntry(archive_reader: sys.FileReader, path: sys.Path) FindError!Entry {
+    var header = Header{};
+    const header_size = @sizeOf(Header);
+    const io = core.io;
+
+    if ((try archive_reader.read(io.bytesOf(&header))) != header_size)
+        return error.ArchiveUnsupported;
+
+    if (!io.equals(u8, &header.signature, &signature_magic))
+        return error.ArchiveUnsupported;
+
+    if (header.revision != revision_magic) return error.ArchiveUnsupported;
+
+    // Read file table.
+    var head: u64 = 0;
+    var tail: u64 = (header.entry_count - 1);
+    const entry_size = @sizeOf(Entry);
+
+    while (head <= tail) {
+        var entry = Entry{};
+        const midpoint = head + ((tail - head) / 2);
+        const offset = header_size + (entry_size * midpoint);
+
+        try archive_reader.seek(offset);
+
+        if ((try archive_reader.read(io.bytesOf(&entry))) != entry_size)
+            return error.ArchiveUnsupported;
+
+        const comparison = path.compare(entry.path);
+
+        if (comparison == 0) return entry;
+
+        if (comparison > 0) {
+            head = (midpoint + 1);
+        } else {
+            tail = (midpoint - 1);
+        }
+    }
+
+    return error.EntryNotFound;
+}
+
+///
+/// Magic revision number that this Oar software implementation understands.
+///
+const revision_magic = 0;
+
+///
+/// Magic identifier used to validate [Header] and [Block] data.
+///
+const signature_magic = [3]u8{'o', 'a', 'r'};

src/ona/sys.zig

@@ -0,0 +1,781 @@
+const ext = @cImport({
+    @cInclude("SDL2/SDL.h");
+});
+
+const core = @import("core");
+const oar = @import("./oar.zig");
+const std = @import("std");
+
+///
+/// Thread-safe platform abstraction over multiplexing system I/O processing and event handling.
+///
+pub const App = struct {
+    message_chain: ?*Message = null,
+    message_semaphore: *ext.SDL_sem,
+    message_mutex: *ext.SDL_mutex,
+    data: FileSystem,
+    user: FileSystem,
+
+    ///
+    /// Enqueues `message` to the message chain in `app`.
+    ///
+    fn enqueue(app: *App, message: *Message) void {
+        {
+            // TODO: Error check these.
+            _ = ext.SDL_LockMutex(app.message_mutex);
+
+            defer _ = ext.SDL_UnlockMutex(app.message_mutex);
+
+            if (app.message_chain) |message_chain| {
+                message_chain.next = message;
+            } else {
+                app.message_chain = message;
+            }
+        }
+
+        // TODO: Error check this.
+        _ = ext.SDL_SemPost(app.message_semaphore);
+    }
+
+    ///
+    /// Asynchronously executes `procedure` with `arguments` as an anonymous struct of its arguments
+    /// and `app` as its execution context.
+    ///
+    /// Once the execution frame resumes, the value returned by executing `procedure` is returned.
+    ///
+    pub fn schedule(app: *App, procedure: anytype,
+        arguments: anytype) core.meta.FnReturn(@TypeOf(procedure)) {
+
+        const Task = struct {
+            procedure: @TypeOf(procedure),
+            arguments: *@TypeOf(arguments),
+            result: core.meta.FnReturn(@TypeOf(procedure)),
+
+            const Task = @This();
+
+            fn process(userdata: *anyopaque) void {
+                const task = @ptrCast(*Task, @alignCast(@alignOf(Task), userdata));
+
+                task.result = @call(.{}, task.procedure, task.arguments.*);
+            }
+        };
+
+        var task = Task{
+            .procedure = procedure,
+            .arguments = &arguments,
+        };
+
+        var message = Message{
+            .kind = .{.task = .{
+                .data = &task,
+                .action = Task.process,
+                .frame = @frame(),
+            }},
+        };
+
+        suspend app.enqueue(&message);
+    }
+
+    ///
+    /// Asynchronously logs `info` with `logger` as the logging method and `app` as the execution
+    /// context.
+    ///
+    pub fn log(app: *App, logger: Logger, info: []const u8) void {
+        var message = Message{
+            .kind = .{.log = .{
+                .logger = logger,
+                .info = info,
+            }},
+        };
+
+        app.enqueue(&message);
+    }
+};
+
+///
+/// Snapshotted information about the status of a file.
+///
+pub const FileStatus = struct {
+    length: u64,
+};
+
+///
+/// Interface for working with bi-directional, streamable resources accessed through a file-system.
+///
+pub const FileReader = struct {
+    context: *anyopaque,
+
+    vtable: *const struct {
+        close: fn (*anyopaque) void,
+        read: fn (*anyopaque, []u8) core.io.AccessError!u64,
+        seek: fn (*anyopaque, u64) core.io.AccessError!void,
+    },
+
+    ///
+    /// Closes the `file_reader`, logging a wraning if the `file_reader` is already considered
+    /// closed.
+    ///
+    pub fn close(file_reader: FileReader) void {
+        file_reader.vtable.close(file_reader.context);
+    }
+
+    ///
+    /// Attempts to read from `file_reader` into `buffer`, returning the number of bytes
+    /// successfully read or [core.io.AccessError] if it failed.
+    ///
+    pub fn read(file_reader: FileReader, buffer: []u8) core.io.AccessError!u64 {
+        return file_reader.vtable.read(file_reader.context, buffer);
+    }
+
+    ///
+    /// Attempts to seek from the beginning of `file_reader` to `cursor` bytes in, returning
+    /// [core.io.AccessError] if it failed.
+    ///
+    pub fn seek(file_reader: FileReader, cursor: u64) core.io.AccessError!void {
+        return file_reader.vtable.seek(file_reader.context, cursor);
+    }
+
+    ///
+    /// Wraps `implementation`, returning a [FileReader] value.
+    ///
+    pub fn wrap(implementation: anytype) FileReader {
+        const Implementation = @TypeOf(implementation.*);
+
+        return .{
+            .context = @ptrCast(*anyopaque, implementation),
+
+            .vtable = switch (@typeInfo(Implementation)) {
+                .Struct => &.{
+                    .close = struct {
+                        fn call(context: *anyopaque) void {
+                            @ptrCast(*Implementation, @alignCast(
+                                @alignOf(Implementation), context)).close();
+                        }
+                    }.call,
+
+                    .read = struct {
+                        fn call(context: *anyopaque, buffer: []u8) core.io.AccessError!u64 {
+                            return @ptrCast(*Implementation, @alignCast(
+                                @alignOf(Implementation), context)).read(buffer);
+                        }
+                    }.call,
+
+                    .seek = struct {
+                        fn call(context: *anyopaque, cursor: u64) core.io.AccessError!void {
+                            return @ptrCast(*Implementation, @alignCast(
+                                @alignOf(Implementation), context)).seek(cursor);
+                        }
+                    }.call,
+                },
+
+                .Opaque => &.{
+                    .close = struct {
+                        fn call(context: *anyopaque) void {
+                            @ptrCast(*Implementation, context).close();
+                        }
+                    }.call,
+
+                    .read = struct {
+                        fn call(context: *anyopaque, buffer: []u8) core.io.AccessError!u64 {
+                            return @ptrCast(*Implementation, context).read(buffer);
+                        }
+                    }.call,
+
+                    .seek = struct {
+                        fn call(context: *anyopaque, cursor: u64) core.io.AccessError!void {
+                            return @ptrCast(*Implementation, context).seek(cursor);
+                        }
+                    }.call,
+                },
+
+                else => @compileError(
+                    "`context` must a single-element pointer referencing a struct or opaque type"),
+            },
+        };
+    }
+};
+
+///
+/// Platform-agnostic mechanism for working with an abstraction of the underlying file-system(s)
+/// available to the application in a sandboxed environment.
+///
+pub const FileSystem = union(enum) {
+    native: []const u8,
+
+    archive: struct {
+        file_system: *const FileSystem,
+        path: Path,
+    },
+
+    ///
+    /// [AccessError.FileNotFound] occurs when a queried file could not be found on the file-system
+    /// by the process. This may mean the file does not exist, however it may also mean that the
+    /// process does not have sufficient rights to read it.
+    ///
+    /// [AccessError.FileSystemfailure] denotes a file-system implementation-specific failure to
+    /// access resources has occured and therefore cannot proceed to access the file.
+    ///
+    pub const AccessError = error {
+        FileNotFound,
+        FileSystemFailure,
+    };
+
+    ///
+    /// Attempts to open the file identified by `path` on `file_system` for reading, returning a
+    /// [FileReader] value that provides access to the opened file or [AccessError] if it failed.
+    ///
+    pub fn openFileReader(file_system: FileSystem, path: Path) AccessError!FileReader {
+        switch (file_system) {
+            .archive => |archive| {
+                const archive_reader = try archive.file_system.openFileReader(archive.path);
+
+                errdefer archive_reader.close();
+
+                const entry = oar.findEntry(archive_reader, path) catch |err| return switch (err) {
+                    error.ArchiveUnsupported, error.Inaccessible => error.FileSystemFailure,
+                    error.EntryNotFound => error.FileNotFound,
+                };
+
+                archive_reader.seek(entry.data_offset) catch return error.FileSystemFailure;
+
+                const io = core.io;
+
+                const allocator = threadSafeAllocator();
+
+                const entry_reader = io.makeOne(struct {
+                    allocator: io.Allocator,
+                    base_reader: FileReader,
+                    cursor: u64,
+                    offset: u64,
+                    length: u64,
+
+                    const Self = @This();
+
+                    pub fn close(self: *Self) void {
+                        self.base_reader.close();
+                        io.free(self.allocator, self);
+                    }
+
+                    pub fn read(self: *Self, buffer: []u8) io.AccessError!u64 {
+                        try self.base_reader.seek(self.offset + self.cursor);
+
+                        return self.base_reader.read(buffer[0 ..
+                            core.math.min(usize, buffer.len, self.length)]);
+                    }
+
+                    pub fn seek(self: *Self, cursor: u64) io.AccessError!void {
+                        self.cursor = cursor;
+                    }
+                }, allocator) catch return error.FileSystemFailure;
+
+                errdefer io.free(allocator, entry_reader);
+
+                entry_reader.* = .{
+                    .allocator = allocator,
+                    .base_reader = archive_reader,
+                    .cursor = 0,
+                    .offset = entry.data_offset,
+                    .length = entry.data_length,
+                };
+
+                return FileReader.wrap(entry_reader);
+            },
+
+            .native => |native| {
+                if (native.len == 0) return error.FileNotFound;
+
+                var path_buffer = [_]u8{0} ** 4096;
+                const seperator_length = @boolToInt(native[native.len - 1] != Path.seperator);
+
+                if ((native.len + seperator_length + path.length) >= path_buffer.len)
+                    return error.FileNotFound;
+
+                const io = core.io;
+
+                io.copy(u8, &path_buffer, native);
+
+                if (seperator_length != 0) path_buffer[native.len] = Path.seperator;
+
+                io.copy(u8, path_buffer[native.len .. path_buffer.len],
+                    path.buffer[0 .. path.length]);
+
+                ext.SDL_ClearError();
+
+                const rw_ops =
+                    ext.SDL_RWFromFile(&path_buffer, "rb") orelse return error.FileNotFound;
+
+                errdefer _ = ext.SDL_RWclose(rw_ops);
+
+                return FileReader.wrap(@ptrCast(*opaque {
+                    const Self = @This();
+
+                    fn rwOpsCast(self: *Self) *ext.SDL_RWops {
+                        return @ptrCast(*ext.SDL_RWops, @alignCast(@alignOf(ext.SDL_RWops), self));
+                    }
+
+                    pub fn read(self: *Self, buffer: []u8) core.io.AccessError!u64 {
+                        ext.SDL_ClearError();
+
+                        const bytes_read =
+                            ext.SDL_RWread(self.rwOpsCast(), buffer.ptr, @sizeOf(u8), buffer.len);
+
+                        if ((bytes_read == 0) and (ext.SDL_GetError() != null))
+                            return error.Inaccessible;
+
+                        return bytes_read;
+                    }
+
+                    pub fn seek(self: *Self, cursor: u64) core.io.AccessError!void {
+                        ext.SDL_ClearError();
+
+                        const math = core.math;
+                        const min = math.min;
+                        const maxIntValue = math.maxIntValue;
+                        var sought = min(u64, cursor, maxIntValue(i64));
+                        const ops = self.rwOpsCast();
+
+                        if (ext.SDL_RWseek(ops, @intCast(i64, sought), ext.RW_SEEK_SET) < 0)
+                            return error.Inaccessible;
+
+                        var to_seek = cursor - sought;
+
+                        while (to_seek != 0) {
+                            sought = min(u64, to_seek, maxIntValue(i64));
+
+                            ext.SDL_ClearError();
+
+                            if (ext.SDL_RWseek(ops, @intCast(i64, sought), ext.RW_SEEK_CUR) < 0)
+                                return error.Inaccessible;
+
+                            to_seek -= sought;
+                        }
+                    }
+
+                    pub fn close(self: *Self) void {
+                        ext.SDL_ClearError();
+
+                        if (ext.SDL_RWclose(self.rwOpsCast()) != 0)
+                            return ext.SDL_LogWarn(ext.SDL_LOG_CATEGORY_APPLICATION,
+                                "Attempt to close an invalid file reference");
+                    }
+                }, rw_ops));
+            },
+        }
+    }
+
+    ///
+    /// Attempts to query the status of the file identified by `path` on `file_system` for reading,
+    /// returning a [FileStatus] value containing a the state of the file at the moment or
+    /// [AccessError] if it failed.
+    ///
+    pub fn query(file_system: FileSystem, path: Path) AccessError!FileStatus {
+        switch (file_system) {
+            .archive => |archive| {
+                const archive_reader = try archive.file_system.openFileReader(archive.path);
+
+                defer archive_reader.close();
+
+                const entry = oar.findEntry(archive_reader, path) catch |err| return switch (err) {
+                    error.ArchiveUnsupported, error.Inaccessible => error.FileSystemFailure,
+                    error.EntryNotFound => error.FileNotFound,
+                };
+
+                return FileStatus{
+                    .length = entry.data_length,
+                };
+            },
+
+            .native => |native| {
+                if (native.len == 0) return error.FileNotFound;
+
+                var path_buffer = [_]u8{0} ** 4096;
+                const seperator_length = @boolToInt(native[native.len - 1] != Path.seperator);
+
+                if ((native.len + seperator_length + path.length) >= path_buffer.len)
+                    return error.FileNotFound;
+
+                const io = core.io;
+
+                io.copy(u8, &path_buffer, native);
+
+                if (seperator_length != 0) path_buffer[native.len] = Path.seperator;
+
+                io.copy(u8, path_buffer[native.len .. path_buffer.len],
+                    path.buffer[0 .. path.length]);
+
+                ext.SDL_ClearError();
+
+                const rw_ops =
+                    ext.SDL_RWFromFile(&path_buffer, "rb") orelse return error.FileSystemFailure;
+
+                defer if (ext.SDL_RWclose(rw_ops) != 0) unreachable;
+
+                ext.SDL_ClearError();
+
+                const size = ext.SDL_RWsize(rw_ops);
+
+                if (size < 0) return error.FileSystemFailure;
+
+                return FileStatus{
+                    .length = @intCast(u64, size),
+                };
+            },
+        }
+    }
+};
+
+///
+///
+///
+pub const Graphics = opaque {
+    ///
+    ///
+    ///
+    pub const Event = struct {
+        keys_up: Keys = std.mem.zeroes(Keys),
+        keys_down: Keys = std.mem.zeroes(Keys),
+        keys_held: Keys = std.mem.zeroes(Keys),
+
+        const Keys = [256]bool;
+    };
+
+    ///
+    ///
+    ///
+    const Implementation = struct {
+        event: Event,
+    };
+
+    ///
+    ///
+    ///
+    pub fn poll(graphics: *Graphics) ?*const Event {
+        _ = graphics;
+
+        return null;
+    }
+
+    ///
+    ///
+    ///
+    pub fn present(graphics: *Graphics) void {
+        // TODO: Implement;
+        _ = graphics;
+    }
+};
+
+///
+/// [Logger.info] logs information that isn't necessarily an error but indicates something useful to
+/// be logged.
+///
+/// [Logger.debug] logs information only when the engine is in debug mode.
+///
+/// [Logger.warning] logs information to indicate a non-critical error has occured.
+///
+pub const Logger = enum(u32) {
+    info = ext.SDL_LOG_PRIORITY_INFO,
+    debug = ext.SDL_LOG_PRIORITY_DEBUG,
+    warning = ext.SDL_LOG_PRIORITY_WARN,
+};
+
+///
+/// Linked list of asynchronous messages chained together to be processed by the work processor.
+///
+pub const Message = struct {
+    next: ?*Message = null,
+
+    kind: union(enum) {
+        quit,
+
+        log: struct {
+            logger: Logger,
+            info: []const u8,
+        },
+
+        task: struct {
+            data: *anyopaque,
+            action: fn (*anyopaque) void,
+            frame: anyframe,
+        },
+    },
+};
+
+///
+/// Path to a file on a [FileSystem].
+///
+pub const Path = extern struct {
+    buffer: [255]u8,
+    length: u8,
+
+    ///
+    /// [Error.TooLong] occurs when creating a path that is greater than the maximum path size **in
+    /// bytes**.
+    ///
+    pub const FromError = error {
+        TooLong,
+    };
+
+    ///
+    /// An empty [Path] with a length of `0`.
+    ///
+    pub const empty = Path{
+        .buffer = [_]u8{0} ** 255,
+        .length = 0,
+    };
+
+    ///
+    /// Returns a value above `0` if the path of `this` is greater than `that`, below `0` if it is
+    /// less, or `0` if they are identical.
+    ///
+    pub fn compare(this: Path, that: Path) isize {
+        return core.io.compareBytes(this.buffer[0 ..this.length], that.buffer[0 .. that.length]);
+    }
+
+    ///
+    /// Returns `true` if `this` is equal to `that`, otherwise `false`.
+    ///
+    pub fn equals(this: Path, that: Path) bool {
+        return core.io.equals(u8, this.buffer[0 ..this.length], that.buffer[0 .. that.length]);
+    }
+
+    ///
+    /// Attempts to create a [Path] with the path components in `sequences` as a fully qualified
+    /// path from root.
+    ///
+    /// A [Path] value is returned containing the fully qualified path from the file-system root or
+    /// a [FromError] if it could not be created.
+    ///
+    pub fn from(sequences: []const []const u8) FromError!Path {
+        var path = empty;
+
+        if (sequences.len != 0) {
+            const last_sequence_index = sequences.len - 1;
+
+            for (sequences) |sequence, index| if (sequence.len != 0) {
+                var components = core.io.Spliterator(u8){
+                    .source = sequence,
+                    .delimiter = "/",
+                };
+
+                while (components.next()) |component| if (component.len != 0) {
+                    for (component) |byte| {
+                        if (path.length == max) return error.TooLong;
+
+                        path.buffer[path.length] = byte;
+                        path.length += 1;
+                    }
+
+                    if (components.hasNext()) {
+                        if (path.length == max) return error.TooLong;
+
+                        path.buffer[path.length] = '/';
+                        path.length += 1;
+                    }
+                };
+
+                if (index < last_sequence_index) {
+                    if (path.length == max) return error.TooLong;
+
+                    path.buffer[path.length] = '/';
+                    path.length += 1;
+                }
+            };
+        }
+
+        return path;
+    }
+
+    ///
+    /// Returns the hash of the text in `path`.
+    ///
+    pub fn hash(path: Path) usize {
+        return core.io.hashBytes(path.buffer[0 .. path.length]);
+    }
+
+    ///
+    /// Maximum number of **bytes** in a [Path].
+    ///
+    pub const max = 255;
+
+    ///
+    /// Textual separator between components of a [Path].
+    ///
+    pub const seperator = '/';
+};
+
+///
+/// [RunError.InitFailure] occurs when the runtime fails to initialize.
+///
+pub const RunError = error {
+    InitFailure,
+};
+
+///
+/// Returns a thread-safe [core.io.Allocator] value based on the default system allocation strategy.
+///
+pub fn threadSafeAllocator() core.io.Allocator {
+    const io = core.io;
+
+    return io.Allocator.wrap(@as(*opaque {
+        const Self = @This();
+
+        pub fn alloc(_: *Self, layout: io.AllocationLayout) io.AllocationError![*]u8 {
+            return @ptrCast([*]u8, ext.SDL_malloc(layout.length) orelse return error.OutOfMemory);
+        }
+
+        pub fn realloc(_: *Self, allocation: [*]u8,
+            layout: io.AllocationLayout) io.AllocationError![*]u8 {
+
+            return @ptrCast([*]u8, ext.SDL_realloc(allocation, layout.length)
+                orelse return error.OutOfMemory);
+        }
+
+        pub fn dealloc(_: *Self, allocation: [*]u8) void {
+            ext.SDL_free(allocation);
+        }
+    }, undefined));
+}
+
+///
+/// Runs a graphical application referenced by `run` with `error` as its error set.
+///
+/// Should an error from `run` occur, an `Error` is returned, otherwise a [RunError] is returned if
+/// the underlying runtime fails and is logged.
+///
+pub fn display(comptime Error: anytype,
+    comptime run: fn (*App, *Graphics) callconv(.Async) Error!void) (RunError || Error)!void {
+
+    const cwd = FileSystem{.native = "./"};
+    const user_prefix = ext.SDL_GetPrefPath("ona", "ona") orelse return error.InitFailure;
+
+    defer ext.SDL_free(user_prefix);
+
+    var app = App{
+        .user = .{.native = std.mem.sliceTo(user_prefix, 0)},
+
+        .message_semaphore = ext.SDL_CreateSemaphore(0) orelse {
+            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION,
+                "Failed to create message semaphore");
+
+            return error.InitFailure;
+        },
+
+        .message_mutex = ext.SDL_CreateMutex() orelse {
+            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION,
+                "Failed to create message mutex");
+
+            return error.InitFailure;
+        },
+
+        .data = .{.archive = .{
+            .file_system = &cwd,
+            .path = try Path.from(&.{"./data.oar"}),
+        }},
+    };
+
+    defer {
+        ext.SDL_DestroySemaphore(app.message_semaphore);
+        ext.SDL_DestroyMutex(app.message_mutex);
+    }
+
+    const message_thread = ext.SDL_CreateThread(processMessages, "Message Processor", &app) orelse {
+        ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to create message processor");
+
+        return error.InitFailure;
+    };
+
+    defer {
+        var message = Message{.kind = .quit};
+
+        app.enqueue(&message);
+
+        {
+            var status: c_int = 0;
+
+            // SDL2 defines waiting on a null thread reference as a no-op. See
+            // https://wiki.libsdl.org/SDL_WaitThread for more information
+            ext.SDL_WaitThread(message_thread, &status);
+
+            if (status != 0) {
+                // TODO: Error check this.
+            }
+        }
+    }
+
+    if (ext.SDL_Init(ext.SDL_INIT_EVERYTHING) != 0) {
+        ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to initialize runtime");
+
+        return error.InitFailure;
+    }
+
+    defer ext.SDL_Quit();
+
+    const window = create_window: {
+        const pos = ext.SDL_WINDOWPOS_UNDEFINED;
+        var flags = @as(u32, 0);
+
+        break: create_window ext.SDL_CreateWindow("Ona", pos, pos, 640, 480, flags) orelse {
+            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to create window");
+
+            return error.InitFailure;
+        };
+    };
+
+    defer ext.SDL_DestroyWindow(window);
+
+    const renderer = create_renderer: {
+        var flags = @as(u32, 0);
+
+        break: create_renderer ext.SDL_CreateRenderer(window, -1, flags) orelse {
+            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to create renderer");
+
+            return error.InitFailure;
+        };
+    };
+
+    defer ext.SDL_DestroyRenderer(renderer);
+
+    var graphics = Graphics.Implementation{
+        .event = .{
+
+        },
+    };
+
+    return run(@ptrCast(*App, &app), @ptrCast(*Graphics, &graphics));
+}
+
+///
+/// [FileSystemMessage] processing function used by a dedicated worker thread, where `data`
+/// is a type-erased reference to a [EventLoop].
+///
+/// The processor returns `0` if it exited normally or any other value if an erroneous exit
+/// occured.
+///
+pub fn processMessages(userdata: ?*anyopaque) callconv(.C) c_int {
+    const app = @ptrCast(*App, @alignCast(@alignOf(App), userdata orelse unreachable));
+
+    while (true) {
+        // TODO: Error check these.
+        _ = ext.SDL_SemWait(app.message_semaphore);
+        _ = ext.SDL_LockMutex(app.message_mutex);
+
+        defer _ = ext.SDL_UnlockMutex(app.message_mutex);
+
+        while (app.message_chain) |message| {
+            switch (message.kind) {
+                .quit => return 0,
+
+                .log => |log| ext.SDL_LogMessage(ext.SDL_LOG_CATEGORY_APPLICATION,
+                    @enumToInt(log.logger), "%.*s", log.info.len, log.info.ptr),
+
+                .task => |task| {
+                    task.action(task.data);
+
+                    resume task.frame;
+                },
+            }
+
+            app.message_chain = message.next;
+        }
+    }
+}

src/stack.zig

@@ -1,117 +0,0 @@
-const io = @import("./io.zig");
-const std = @import("std");
-
-pub fn Fixed(comptime Element: type) type {
-    return struct {
-        filled: usize = 0,
-        buffer: []Element,
-
-        const Self = @This();
-
-        ///
-        /// Wraps `self` and returns it in a [io.Writer] value.
-        ///
-        /// Note that this will raise a compilation error if [Element] is not `u8`.
-        ///
-        pub fn writer(self: *Self) io.Writer {
-            if (Element != u8) @compileError("Cannot coerce fixed stack of type " ++
-                @typeName(Element) ++ " into a Writer");
-
-            return io.Writer.wrap(Self, self, struct {
-                fn write(stack: *Self, buffer: []const u8) usize {
-                    stack.pushAll(buffer) catch |err| switch (err) {
-                        error.Overflow => return 0,
-                    };
-
-                    return buffer.len;
-                }
-            }.write);
-        }
-
-        ///
-        /// Clears all elements from `self`.
-        ///
-        pub fn clear(self: *Self) void {
-            self.filled = 0;
-        }
-
-        ///
-        /// Counts and returns the number of pushed elements in `self`.
-        ///
-        pub fn count(self: Self) usize {
-            return self.filled;
-        }
-
-        ///
-        /// Attempts to pop the tail-end of `self`, returning the element value or `null` if the
-        /// stack is empty.
-        ///
-        pub fn pop(self: *Self) ?Element {
-            if (self.filled == 0) return null;
-
-            self.filled -= 1;
-
-            return self.buffer[self.filled];
-        }
-
-        ///
-        /// Attempts to push `element` into `self`, returning a [FixedPushError] if it failed.
-        ///
-        pub fn push(self: *Self, element: Element) FixedPushError!void {
-            if (self.filled == self.buffer.len) return error.Overflow;
-
-            self.buffer[self.filled] = element;
-            self.filled += 1;
-        }
-
-        ///
-        /// Attempts to push all of `elements` into `self`, returning a [FixedPushError] if it
-        /// failed.
-        ///
-        pub fn pushAll(self: *Self, elements: []const u8) FixedPushError!void {
-            const filled = (self.filled + elements.len);
-
-            if (filled > self.buffer.len) return error.Overflow;
-
-            std.mem.copy(u8, self.buffer[self.filled ..], elements);
-
-            self.filled = filled;
-        }
-    };
-}
-
-///
-/// Potential errors that may occur while trying to push one or more elements into a stack of a
-/// known maximum size.
-///
-/// [FinitePushError.Overflow] is returned if the stack does not have sufficient capacity to hold a
-/// given set of elements.
-///
-pub const FixedPushError = error {
-    Overflow,
-};
-
-test {
-    const testing = std.testing;
-    var buffer = std.mem.zeroes([4]u8);
-    var stack = Fixed(u8){.buffer = &buffer};
-
-    try testing.expectEqual(stack.count(), 0);
-    try testing.expectEqual(stack.pop(), null);
-    try stack.push(69);
-    try testing.expectEqual(stack.count(), 1);
-    try testing.expectEqual(stack.pop(), 69);
-    try stack.pushAll(&.{42, 10, 95, 0});
-    try testing.expectEqual(stack.count(), 4);
-    try testing.expectError(FixedPushError.Overflow, stack.push(1));
-    try testing.expectError(FixedPushError.Overflow, stack.pushAll(&.{1, 11, 11}));
-
-    stack.clear();
-
-    try testing.expectEqual(stack.count(), 0);
-
-    const writer = stack.writer();
-
-    try testing.expectEqual(writer.write(&.{0, 0, 0, 0}), 4);
-    try testing.expectEqual(writer.writeByte(0), false);
-}

src/sys.zig

@@ -1,642 +0,0 @@
-const ext = @cImport({
-    @cInclude("SDL2/SDL.h");
-});
-
-const io = @import("./io.zig");
-const mem = @import("./mem.zig");
-const stack = @import("./stack.zig");
-const std = @import("std");
-
-///
-/// A thread-safe platform abstraction over multiplexing system I/O processing and event handling.
-///
-pub const EventLoop = opaque {
-    ///
-    /// Linked list of messages chained together to be processed by the internal file system message
-    /// processor of an [EventLoop].
-    ///
-    const FileSystemMessage = struct {
-        next: ?*FileSystemMessage = null,
-        frame: anyframe,
-
-        request: union(enum) {
-            exit,
-
-            close: struct {
-                file_access: *FileAccess,
-            },
-
-            log: struct {
-                message: []const u8,
-                kind: LogKind,
-            },
-
-            open: struct {
-                mode: OpenMode,
-                file_system_path: *const FileSystem.Path,
-                result: OpenError!*FileAccess = error.NotFound,
-            },
-
-            read_file: struct {
-                file_access: *FileAccess,
-                buffer: []const u8,
-                result: FileError!usize = error.Inaccessible,
-            },
-
-            seek_file: struct {
-                file_access: *FileAccess,
-                origin: SeekOrigin,
-                offset: usize,
-                result: FileError!void = error.Inaccessible,
-            },
-
-            tell_file: struct {
-                file_access: *FileAccess,
-                result: FileError!usize = error.Inaccessible,
-            },
-        },
-    };
-
-    ///
-    /// Internal state of the event loop hidden from the API consumer.
-    ///
-    const Implementation = struct {
-        user_prefix: []const u8,
-        file_system_semaphore: *ext.SDL_sem,
-        file_system_mutex: *ext.SDL_mutex,
-        file_system_thread: *ext.SDL_Thread,
-        file_system_messages: ?*FileSystemMessage = null,
-
-        ///
-        /// Casts `event_loop` to a [Implementation] reference.
-        ///
-        /// *Note* that if `event_loop` does not have the same alignment as [Implementation],
-        /// safety-checked undefined behavior will occur.
-        ///
-        fn cast(event_loop: *EventLoop) *Implementation {
-            return @ptrCast(*Implementation, @alignCast(@alignOf(Implementation), event_loop));
-        }
-    };
-
-    ///
-    /// [LogKind.info] represents a log message which is purely informative and does not indicate
-    /// any kind of issue.
-    ///
-    /// [LogKind.debug] represents a log message which is purely for debugging purposes and will
-    /// only occurs in debug builds.
-    ///
-    /// [LogKind.warning] represents a log message which is a warning about a issue that does not
-    /// break anything important but is not ideal.
-    ///
-    pub const LogKind = enum(c_int) {
-        info = ext.SDL_LOG_PRIORITY_INFO,
-        debug = ext.SDL_LOG_PRIORITY_DEBUG,
-        warning = ext.SDL_LOG_PRIORITY_WARN,
-    };
-
-    ///
-    /// [OpenError.NotFound] is a catch-all for when a file could not be located to be opened. This
-    /// may be as simple as it doesn't exist or the because the underlying file-system will not /
-    /// cannot give access to it at this time.
-    ///
-    pub const OpenError = error {
-        NotFound,
-    };
-
-    ///
-    /// [OpenMode.readonly] indicates that an existing file is opened in a read-only state,
-    /// disallowing write access.
-    ///
-    /// [OpenMode.overwrite] indicates that an empty file has been created or an existing file has
-    /// been completely overwritten into.
-    ///
-    /// [OpenMode.append] indicates that an existing file that has been opened for reading from and
-    /// writing to on the end of existing data.
-    ///
-    pub const OpenMode = enum {
-        readonly,
-        overwrite,
-        append,
-    };
-
-    ///
-    /// [SeekOrigin.head] indicates that a seek operation will seek from the offset origin of the
-    /// file beginning, or "head".
-    ///
-    /// [SeekOrigin.tail] indicates that a seek operation will seek from the offset origin of the
-    /// file end, or "tail".
-    ///
-    /// [SeekOrigin.cursor] indicates that a seek operation will seek from the current position of
-    /// the file cursor.
-    ///
-    pub const SeekOrigin = enum {
-        head,
-        tail,
-        cursor,
-    };
-
-    ///
-    /// Closes access to the file referenced by `file_access` via `event_loop`.
-    ///
-    /// *Note* that nothing happens to `file_access` if it is already closed.
-    ///
-    pub fn close(event_loop: *EventLoop, file_access: *FileAccess) void {
-        var file_system_message = FileSystemMessage{
-            .frame = @frame(),
-            .request = .{.close = .{.file_access = file_access}},
-        };
-
-        suspend event_loop.enqueueFileSystemMessage(&file_system_message);
-    }
-
-    ///
-    /// Enqueues `message` to the file system message processor to be processed at a later, non-
-    /// deterministic point.
-    ///
-    fn enqueueFileSystemMessage(event_loop: *EventLoop, message: *FileSystemMessage) void {
-        const implementation = Implementation.cast(event_loop);
-
-        // TODO: Error check this.
-        _ = ext.SDL_LockMutex(implementation.file_system_mutex);
-
-        if (implementation.file_system_messages) |messages| {
-            messages.next = message;
-        } else {
-            implementation.file_system_messages = message;
-        }
-
-        // TODO: Error check these.
-        _ = ext.SDL_UnlockMutex(implementation.file_system_mutex);
-        _ = ext.SDL_SemPost(implementation.file_system_semaphore);
-    }
-
-    ///
-    /// Writes `message` to the application log with `kind` via `event_loop`.
-    ///
-    /// *Note* that `message` is not guaranteed to be partly, wholely, or at all written.
-    ///
-    pub fn log(event_loop: *EventLoop, kind: LogKind, message: []const u8) void {
-        var file_system_message = FileSystemMessage{
-            .frame = @frame(),
-
-            .request = .{.log = .{
-                .message = message,
-                .kind = kind,
-            }},
-        };
-
-        suspend event_loop.enqueueFileSystemMessage(&file_system_message);
-    }
-
-    ///
-    /// Attempts to open access to a file referenced at `file_system_path` using `mode` as the way
-    /// to open it via `event_loop`.
-    ///
-    /// A [FileAccess] pointer is returned referencing the opened file or a [OpenError] if the file
-    /// could not be opened.
-    ///
-    /// *Note* that all files are opened in "binary-mode", or Unix-mode. There are no conversions
-    /// applied when data is accessed from a file.
-    ///
-    pub fn open(event_loop: *EventLoop, mode: OpenMode,
-        file_system_path: FileSystem.Path) OpenError!*FileAccess {
-
-        var file_system_message = FileSystemMessage{
-            .frame = @frame(),
-
-            .request = .{.open = .{
-                .mode = mode,
-                .file_system_path = &file_system_path,
-            }},
-        };
-
-        suspend event_loop.enqueueFileSystemMessage(&file_system_message);
-
-        return file_system_message.request.open.result;
-    }
-
-    ///
-    /// [FileSystemMessage] processing function used by a dedicated worker thread, where `data` is
-    /// a type-erased reference to a [EventLoop].
-    ///
-    /// The processor returns `0` if it exited normally or any other value if an erroneous exit
-    /// occured.
-    ///
-    fn processFileSystemMessages(data: ?*anyopaque) callconv(.C) c_int {
-        const implementation = Implementation.cast(@ptrCast(*EventLoop, data orelse unreachable));
-
-        while (true) {
-            while (implementation.file_system_messages) |messages| {
-                switch (messages.request) {
-                    .exit => return 0,
-
-                    .log => |*log_request| ext.SDL_LogMessage(ext.SDL_LOG_CATEGORY_APPLICATION,
-                                @enumToInt(log_request.priority), log_request.message),
-
-                    .open => |*open_request| {
-                        switch (open_request.path.file_system) {
-                            .data => {
-                                // TODO: Implement
-                                open_request.result = error.NotFound;
-                            },
-
-                            .user => {
-                                var path_buffer = std.mem.zeroes([4096]u8);
-                                var path = stack.Fixed(u8){.buffer = path_buffer[0 .. ]};
-
-                                path.pushAll(implementation.user_prefix) catch {
-                                    open_request.result = error.BadFileSystem;
-
-                                    continue;
-                                };
-
-                                if (!open_request.path.write(path.writer())) {
-                                    open_request.result = error.NotFound;
-
-                                    continue;
-                                }
-
-                                if (ext.SDL_RWFromFile(&path_buffer, switch (open_request.mode) {
-                                    .readonly => "rb",
-                                    .overwrite => "wb",
-                                    .append => "ab",
-                                })) |rw_ops| {
-                                    open_request.result = @ptrCast(*FileAccess, rw_ops);
-                                } else {
-                                    open_request.result = error.NotFound;
-                                }
-                            },
-                        }
-                    },
-
-                    .close => |*close_request| {
-                        // TODO: Use this result somehow.
-                        _ = ext.SDL_RWclose(@ptrCast(*ext.SDL_RWops, @alignCast(
-                                @alignOf(ext.SDL_RWops), close_request.file_access)));
-                    },
-
-                    .read_file => |read_request| {
-                        // TODO: Implement.
-                        _ = read_request;
-                    },
-
-                    .seek_file => |seek_request| {
-                        // TODO: Implement.
-                        _ = seek_request;
-                    },
-
-                    .tell_file => |tell_request| {
-                        // TODO: Implement.
-                        _ = tell_request;
-                    },
-                }
-
-                resume messages.frame;
-
-                implementation.file_system_messages = messages.next;
-            }
-
-            // TODO: Error check this.
-            _ = ext.SDL_SemWait(implementation.file_system_semaphore);
-        }
-    }
-
-    ///
-    /// Attempts to read the contents of the file referenced by `file_access` at the current file
-    /// cursor position into `buffer`.
-    ///
-    /// The number of bytes that could be read / fitted into `buffer` is returned or a [FileError]
-    /// if the file failed to be read.
-    ///
-    pub fn readFile(event_loop: *EventLoop, file_access: *FileAccess,
-        buffer: []const u8) FileError!usize {
-
-        var file_system_message = FileSystemMessage{
-            .frame = @frame(),
-
-            .request = .{.read_file = .{
-                .file_access = file_access,
-                .buffer = buffer,
-            }},
-        };
-
-        suspend event_loop.enqueueFileSystemMessage(&file_system_message);
-
-        return file_system_message.request.read_file.result;
-    }
-
-    ///
-    /// Attempts to tell the current file cursor position for the file referenced by `file_access`.
-    ///
-    /// Returns the number of bytes into the file that the cursor is relative to its beginning or a
-    /// [FileError] if the file failed to be queried.
-    ///
-    pub fn queryFile(event_loop: *EventLoop, file_access: *FileAccess) FileError!usize {
-        var file_system_message = FileSystemMessage{
-            .frame = @frame(),
-            .request = .{.tell_file = .{.file_access = file_access}},
-        };
-
-        suspend event_loop.enqueueFileSystemMessage(&file_system_message);
-
-        return file_system_message.request.tell_file.result;
-    }
-
-    ///
-    /// Attempts to seek the file cursor through the file referenced by `file_access` from `origin`
-    /// to `offset` via `event_loop`, returning a [FileError] if the file failed to be sought.
-    ///
-    pub fn seekFile(event_loop: *EventLoop, file_access: *FileAccess,
-        origin: SeekOrigin, offset: usize) FileError!void {
-
-        var file_system_message = FileSystemMessage{
-            .frame = @frame(),
-
-            .request = .{
-                .seek_file = .{
-                    .file_access = file_access,
-                    .origin = origin,
-                    .offset = offset,
-                },
-            },
-        };
-
-        suspend event_loop.enqueueFileSystemMessage(&file_system_message);
-
-        return file_system_message.request.seek_file.result;
-    }
-};
-
-///
-/// File-system agnostic abstraction for manipulating a file.
-///
-pub const FileAccess = opaque {
-    ///
-    /// Scans the number of bytes in the file referenced by `file_access` via `event_loop`, returing
-    /// its byte size or a [FileError] if it failed.
-    ///
-    pub fn size(file_access: *FileAccess, event_loop: *EventLoop) FileError!usize {
-        // Save cursor to return to it later.
-        const origin_cursor = try event_loop.queryFile(file_access);
-
-        try event_loop.seekFile(file_access, .tail, 0);
-
-        const ending_cursor = try event_loop.queryFile(file_access);
-
-        // Return to original cursor.
-        try event_loop.seekFile(file_access, .head, origin_cursor);
-
-        return ending_cursor;
-    }
-};
-
-///
-/// With files typically being backed by a block device, they can produce a variety of errors -
-/// from physical to virtual errors - these are all encapsulated by the API as general
-/// [Error.Inaccessible] errors.
-///
-pub const FileError = error {
-    Inaccessible,
-};
-
-///
-/// Platform-agnostic mechanism for working with an abstraction of the underlying file-system(s)
-/// available to the application in a sandboxed environment.
-///
-pub const FileSystem = enum {
-    data,
-    user,
-
-    ///
-    /// Platform-agnostic mechanism for referencing files and directories on a [FileSystem].
-    ///
-    pub const Path = struct {
-        file_system: FileSystem,
-        length: u16,
-        buffer: [max]u8,
-
-        ///
-        /// Returns `true` if the length of `path` is empty, otherwise `false`.
-        ///
-        pub fn isEmpty(path: Path) bool {
-            return (path.length == 0);
-        }
-
-        ///
-        /// Returns `true` if `this` is equal to `that`, otherwise `false`.
-        ///
-        pub fn equals(this: Path, that: Path) bool {
-            return std.mem.eql(u8, this.buffer[0 .. this.length], that.buffer[0 .. that.length]);
-        }
-
-        ///
-        /// The maximum possible byte-length of a [Path].
-        ///
-        /// Note that paths are encoded using UTF-8, meaning that a character may be bigger than one
-        /// byte. Because of this, it is not safe to asume that a path may hold [max] individual
-        /// characters.
-        ///
-        pub const max = 1000;
-
-        ///
-        ///
-        ///
-        pub fn write(path: Path, writer: io.Writer) bool {
-            return (writer.write(path.buffer[0 .. path.length]) == path.length);
-        }
-    };
-
-    ///
-    /// [PathError.TooLong] occurs when creating a path that is greater than the maximum size **in
-    /// bytes**.
-    ///
-    pub const PathError = error {
-        TooLong,
-    };
-
-    ///
-    /// Creates and returns a [Path] value in the file system to the location specified by the
-    /// joining of the `sequences` path values.
-    ///
-    pub fn joinedPath(file_system: FileSystem, sequences: []const []const u8) PathError!Path {
-        var path = Path{
-            .file_system = file_system,
-            .buffer = std.mem.zeroes([Path.max]u8),
-            .length = 0,
-        };
-
-        for (sequences) |sequence| if (sequence.len != 0) {
-            var components = mem.Spliterator(u8){
-                .source = sequence,
-                .delimiter = "/",
-            };
-
-            while (components.next()) |component| if (component.len != 0) {
-                for (component) |byte| {
-                    if (path.length == Path.max) return error.TooLong;
-
-                    path.buffer[path.length] = byte;
-                    path.length += 1;
-                }
-
-                if (path.length == Path.max) return error.TooLong;
-
-                path.buffer[path.length] = '/';
-                path.length += 1;
-            };
-        };
-
-        return path;
-    }
-};
-
-///
-///
-///
-pub const GraphicsContext = opaque {
-    ///
-    ///
-    ///
-    pub const Event = struct {
-        keys_up: Keys = std.mem.zeroes(Keys),
-        keys_down: Keys = std.mem.zeroes(Keys),
-        keys_held: Keys = std.mem.zeroes(Keys),
-
-        const Keys = [256]bool;
-    };
-
-    const Implementation = struct {
-        event: Event,
-    };
-
-    ///
-    ///
-    ///
-    pub fn poll(graphics_context: *GraphicsContext) ?*const Event {
-        _ = graphics_context;
-
-        return null;
-    }
-
-    ///
-    ///
-    ///
-    pub fn present(graphics_context: *GraphicsContext) void {
-        // TODO: Implement;
-        _ = graphics_context;
-    }
-};
-
-///
-///
-///
-pub fn GraphicsRunner(comptime Errors: type) type {
-    return fn (*EventLoop, *GraphicsContext) Errors!void;
-}
-
-///
-///
-///
-pub fn runGraphics(comptime Errors: anytype, run: GraphicsRunner(Errors)) Errors!void {
-    if (ext.SDL_Init(ext.SDL_INIT_EVERYTHING) != 0) {
-        ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to initialize runtime");
-
-        return error.InitFailure;
-    }
-
-    defer ext.SDL_Quit();
-
-    const pref_path = create_pref_path: {
-        const path = ext.SDL_GetPrefPath("ona", "ona") orelse {
-            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to load user path");
-
-            return error.InitFailure;
-        };
-
-        break: create_pref_path path[0 .. std.mem.len(path)];
-    };
-
-    defer ext.SDL_free(pref_path.ptr);
-
-    const window = create_window: {
-        const pos = ext.SDL_WINDOWPOS_UNDEFINED;
-        var flags = @as(u32, 0);
-
-        break: create_window ext.SDL_CreateWindow("Ona", pos, pos, 640, 480, flags) orelse {
-            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to create window");
-
-            return error.InitFailure;
-        };
-    };
-
-    defer ext.SDL_DestroyWindow(window);
-
-    const renderer = create_renderer: {
-        var flags = @as(u32, 0);
-
-        break: create_renderer ext.SDL_CreateRenderer(window, -1, flags) orelse {
-            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to create renderer");
-
-            return error.InitFailure;
-        };
-    };
-
-    defer ext.SDL_DestroyRenderer(renderer);
-
-    var event_loop = EventLoop.Implementation{
-        .file_system_semaphore = ext.SDL_CreateSemaphore(0) orelse {
-            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION,
-                "Failed to create file-system work scheduler");
-
-            return error.InitFailure;
-        },
-
-        .file_system_mutex = ext.SDL_CreateMutex() orelse {
-            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION,
-                "Failed to create file-system work lock");
-
-            return error.InitFailure;
-        },
-
-        .file_system_thread = unreachable,
-        .user_prefix = pref_path,
-    };
-
-    event_loop.file_system_thread = ext.SDL_CreateThread(
-        EventLoop.processFileSystemMessages, "File System Worker", &event_loop) orelse {
-
-        ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION,
-            "Failed to create file-system work processor");
-
-        return error.InitFailure;
-    };
-
-    defer {
-        ext.SDL_DestroyThread(event_loop.file_system_thread);
-        ext.SDL_DestroySemaphore(event_loop.file_system_mutex);
-        ext.SDL_DestroySemaphore(event_loop.file_system_semaphore);
-    }
-
-    var graphics_context = GraphicsContext.Implementation{
-        .event = .{
-
-        },
-    };
-
-    var message = EventLoop.FileSystemMessage{
-        .frame = @frame(),
-        .request = .exit,
-    };
-
-    @ptrCast(*EventLoop, event_loop).enqueueFileSystemMessage(&message);
-
-    var status = @as(c_int, 0);
-
-    ext.SDL_WaitThread(event_loop.file_system_thread, &status);
-
-    if (status != 0) {
-        // TODO: Error check this.
-    }
-
-    return run(@ptrCast(*EventLoop, &event_loop), @ptrCast(*GraphicsContext, &graphics_context));
-}

src/tests.zig

@@ -0,0 +1,4 @@
+test {
+    _ = @import("./core/main.zig");
+    _ = @import("./ona/main.zig");
+}