Initial work on allocator replacement

src/core/io.zig

@@ -4,9 +4,66 @@ const stack = @import("./stack.zig");
 const testing = @import("./testing.zig");
 
 ///
+/// Dynamic memory allocation interface.
 ///
-///
-pub const Allocator = @import("std").mem.Allocator;
+pub const Allocator = union (enum) {
+    bound: struct {
+        alloc: fn (usize) ?[*]u8,
+        dealloc: fn ([*]u8) void,
+    },
+
+    arena: struct {
+        buffer: []u8,
+        cursor: usize = 0,
+    },
+
+    ///
+    /// [MakeError.OutOfMemory] is used to indicate there is not enough memory available for a given
+    /// operation.
+    ///
+    pub const MakeError = error {
+        OutOfMemory,
+    };
+
+    ///
+    /// Frees `allocation` using `allocator`.
+    ///
+    pub fn free(allocator: *Allocator, allocation: anytype) void {
+        switch (@typeInfo(@TypeOf(allocation))) {
+            .Pointer => |pointer| if (pointer.size == .Slice)
+                @compileError("`allocation` cannot be a slice"),
+
+            else => @compileError("`allocation` must be a pointer"),
+        }
+
+        if (@typeInfo(@TypeOf(allocation)) != .Pointer)
+            @compileError("`allocation` must be a pointer");
+
+        // TODO: Implement arena de-allocation.
+        switch (allocator.*) {
+            .bound => |bound| bound.dealloc(@ptrCast([*]u8, allocation)),
+            .arena => {},
+        }
+    }
+
+    ///
+    /// Attempts to allocate `size` number of `Element`s using `allocator`.
+    ///
+    /// Returns the allocation or a [MakeError] if it failed.
+    ///
+    pub fn make(allocator: *Allocator, comptime Element: type, size: usize) MakeError![*]Element {
+        switch (allocator.*) {
+            .bound => |bound| return @ptrCast([*]Element, @alignCast(@alignOf(Element),
+                bound.alloc(@sizeOf(Element) * size) orelse return error.OutOfMemory)),
+
+            .arena => |*stack| {
+                defer stack.cursor += size;
+
+                return @ptrCast([*]Element, @alignCast(@alignOf(Element), stack.buffer.ptr));
+            },
+        }
+    }
+};
 
 ///
 /// Closure that captures a reference to readable resources like block devices, memory buffers,
@@ -32,26 +89,6 @@ pub fn Spliterator(comptime Element: type) type {
             return (self.source.len != 0);
         }
 
-        test "Check has data" {
-            var empty_spliterator = Spliterator(u8){
-                .source = "",
-                .delimiter = "/",
-            };
-
-            try testing.expect(!empty_spliterator.hasNext());
-
-            var stateful_spliterator = Spliterator(u8){
-                .source = "data",
-                .delimiter = "/",
-            };
-
-            try testing.expect(stateful_spliterator.hasNext());
-
-            _ = try stateful_spliterator.next();
-
-            try testing.expect(!stateful_spliterator.hasNext());
-        }
-
         ///
         /// 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.
@@ -59,22 +96,52 @@ pub fn Spliterator(comptime Element: type) type {
         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)) |index| {
-                defer self.source = self.source[(index + self.delimiter.len) .. self.source.len];
+            }.testEquality)) |head| {
+                defer self.source = self.source[(head + self.delimiter.len) .. self.source.len];
 
-                return self.source[0 .. index];
+                return self.source[0 .. head];
             }
 
             defer self.source = self.source[self.source.len .. self.source.len];
 
             return self.source;
         }
+    };
+}
+
+test "Spliterator of string literals" {
+    // 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());
+    }
 
-        test "Iterate through data" {
     // Single-character delimiter.
     {
         var spliterator = Spliterator(u8){
@@ -86,10 +153,14 @@ pub fn Spliterator(comptime Element: type) type {
             "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.
@@ -101,13 +172,15 @@ pub fn Spliterator(comptime Element: type) type {
 
         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());
     }
-        }
-    };
 }
 
 ///
@@ -116,22 +189,6 @@ pub fn Spliterator(comptime Element: type) type {
 ///
 pub const Writer = meta.Function(@sizeOf(usize), []const u8, usize);
 
-///
-/// Returns `true` if `elements` starts with the characters in `with`, otherwise `false`.
-///
-pub fn begins(comptime Element: type, elements: []const Element, with: []const Element) bool {
-    if (elements.len < with.len) return false;
-
-    return equals(Element, elements[0 .. with.len], with);
-}
-
-test "Check memory begins with" {
-    const bytes_sequence = &.{69, 42};
-
-    try testing.expect(begins(u8, &.{69, 42, 0, 89}, bytes_sequence));
-    try testing.expect(!begins(u8, &.{69, 89, 42, 0}, bytes_sequence));
-}
-
 ///
 /// Returns a sliced reference of the raw bytes in `pointer`.
 ///
@@ -254,24 +311,30 @@ test "Find first of element" {
 pub fn findFirstOf(comptime Element: type, haystack: []const Element,
     needle: []const Element, comptime testEquality: fn (Element, Element) bool) ?usize {
 
-    var cursor: usize = 0;
-    const end = (haystack.len - needle.len);
+    var head: usize = 0;
+    const tail = (haystack.len - needle.len);
 
-    walk_haystack: while (cursor <= end) : (cursor += 1) {
-        const range = (cursor + needle.len);
-        var index = cursor;
+    walk_haystack: while (head <= tail) : (head += 1) {
+        for (needle) |element, index|
+            if (!testEquality(haystack[head + index], element)) continue: walk_haystack;
 
-        while (index < range) : (index += 1)
-            if (testEquality(haystack[index], needle[index])) continue: walk_haystack;
-
-        return cursor;
+        return head;
     }
 
     return null;
 }
 
 test "Find first of sequence" {
+    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);
 }
 
 ///

src/core/stack.zig

@@ -113,7 +113,7 @@ test "Fixed stack of string literals" {
 ///
 /// Potential errors that may occur while trying to push one or more elements into a stack.
 ///
-pub const PushError = io.Allocator.Error;
+pub const PushError = io.Allocator.MakeError;
 
 ///
 /// Returns an [io.Writer] wrapping `fixed_stack`.

src/core/table.zig

@@ -1,4 +1,5 @@
 const io = @import("./io.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
@@ -10,7 +11,7 @@ pub fn Hashed(comptime Key: type, comptime Value: type,
     const Allocator = io.Allocator;
 
     return struct {
-        allocator: Allocator,
+        allocator: *Allocator,
         load_limit: f32,
         buckets: []Bucket,
         filled: usize,
@@ -36,7 +37,7 @@ pub fn Hashed(comptime Key: type, comptime Value: type,
         /// Deinitializes `self`, preventing any further use.
         ///
         pub fn deinit(self: *Self) void {
-            self.allocator.free(self.buckets);
+            self.allocator.free(self.buckets.ptr);
 
             self.buckets = &.{};
         }
@@ -44,13 +45,13 @@ pub fn Hashed(comptime Key: type, comptime Value: type,
         ///
         /// Initializes a [Self] using `allocator` as the memory allocation strategy.
         ///
-        /// Returns a new [Self] value or an [io.Allocator.Error] if initializing failed.
+        /// Returns a new [Self] value or an [io.Allocator.MakeError] if initializing failed.
         ///
-        pub fn init(allocator: Allocator) Allocator.Error!Self {
+        pub fn init(allocator: *Allocator) Allocator.MakeError!Self {
             const initial_capacity = 4;
 
             return Self{
-                .buckets = try allocator.alloc(Bucket, initial_capacity),
+                .buckets = (try allocator.make(Bucket, initial_capacity))[0 .. initial_capacity],
                 .filled = 0,
                 .allocator = allocator,
                 .load_limit = 0.75,
@@ -98,9 +99,11 @@ pub fn Hashed(comptime Key: type, comptime Value: type,
             if (self.loadFactor() >= self.load_limit) {
                 const old_buckets = self.buckets;
 
-                defer self.allocator.free(old_buckets);
+                defer self.allocator.free(old_buckets.ptr);
 
-                self.buckets = try self.allocator.alloc(Bucket, old_buckets.len * 2);
+                const bucket_count = old_buckets.len * 2;
+
+                self.buckets = (try self.allocator.make(Bucket, bucket_count))[0 .. bucket_count];
 
                 for (old_buckets) |bucket, index| self.buckets[index] = bucket;
             }
@@ -160,7 +163,7 @@ pub fn Hashed(comptime Key: type, comptime Value: type,
 /// [InsertError.KeyExists] occurs when an insertion was attempted on a table with a matching key
 /// already present.
 ///
-pub const InsertError = io.Allocator.Error || error {
+pub const InsertError = io.Allocator.MakeError || error {
     KeyExists,
 };
 
@@ -193,16 +196,16 @@ pub const string_literal_context = KeyContext([]const u8){
 };
 
 test "Hash table manipulation with string literal context" {
-    const testing = @import("std").testing;
-
-    var table = try Hashed([]const u8, u32, string_literal_context).init(testing.allocator);
+    var buffer = [_]u8{0} ** 1024;
+    var allocator = io.Allocator{.arena = .{.buffer = &buffer}};
+    var table = try Hashed([]const u8, u32, string_literal_context).init(&allocator);
 
     defer table.deinit();
 
     const foo = @as(u32, 69);
 
-    try testing.expectEqual(table.remove("foo"), null);
+    try testing.expect(table.remove("foo") == null);
     try table.insert("foo", foo);
-    try testing.expectEqual(table.remove("foo"), foo);
-    try testing.expectEqual(table.remove("foo"), null);
+    try testing.expect(table.remove("foo").? == foo);
+    try testing.expect(table.remove("foo") == null);
 }

src/ona/sys.zig

@@ -378,12 +378,14 @@ pub const Path = extern struct {
                 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;
                     }
@@ -426,6 +428,19 @@ pub const RunError = error {
     InitFailure,
 };
 
+///
+/// Returns a [core.io.Allocator] bound to the underlying system allocator.
+///
+pub fn allocator() core.io.Allocator {
+    // TODO: Add leak detection.
+    return .{
+        .bound = .{
+            .alloc = ext.SDL_alloc,
+            .dealloc = ext.SDL_free,
+        },
+    };
+}
+
 ///
 /// Runs a graphical application referenced by `run` with `error` as its error set.
 ///