Initial work on new system-level abstraction

src/main.zig

@@ -11,76 +11,26 @@ const sys = @import("./sys.zig");
 /// Entry point.
 ///
 pub fn main() anyerror!void {
-    if (ext.SDL_Init(ext.SDL_INIT_EVERYTHING) != 0) {
-        ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to initialize SDL2 runtime");
-
-        return error.InitFailure;
+    return sys.runGraphics(anyerror, run);
 }
 
-    defer ext.SDL_Quit();
+fn run(event_loop: *sys.EventLoop, graphics: *sys.GraphicalContext) anyerror!void {
+    var gpa = std.heap.GeneralPurposeAllocator(){};
 
-    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");
+    {
+        const file = event_loop.open(.readonly, sys.Path.get(.data, &.{"ona.lua"}));
 
-            return error.InitFailure;
-        };
+        defer _ = event_loop.closeFile(file);
 
-        break: create_pref_path path[0 .. std.mem.len(path)];
-    };
+        const file_size = try file.size(event_loop);
+        var buffer = try gpa.allocator().alloc(u8, file_size);
 
-    defer ext.SDL_free(pref_path.ptr);
+        if (try event_loop.readFile(buffer) != file_size) return error.ScriptLoadError;
 
-    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 load SDL2 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 load SDL2 renderer");
-
-            return error.InitFailure;
-        };
-    };
-
-    defer ext.SDL_DestroyRenderer(renderer);
-
-    var event_loop = sys.EventLoop{};
-    var is_running = true;
-
-    while (is_running) {
-        var event = std.mem.zeroes(ext.SDL_Event);
-
-        while (ext.SDL_PollEvent(&event) != 0) {
-            switch (event.type) {
-                ext.SDL_QUIT => is_running = false,
-                else => {},
-            }
+        sys.log(buffer);
     }
 
-        if (ext.SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255) != 0) {
-            ext.SDL_LogError(ext.SDL_LOG_CATEGORY_VIDEO, ext.SDL_GetError());
-            ext.SDL_ClearError();
-        }
-
-        if (ext.SDL_RenderClear(renderer) != 0) {
-            ext.SDL_LogError(ext.SDL_LOG_CATEGORY_VIDEO, ext.SDL_GetError());
-            ext.SDL_ClearError();
-        }
-
-        ext.SDL_RenderPresent(renderer);
-        event_loop.tick();
-        ext.SDL_Delay(1);
+    while (graphics.poll()) |_| {
+        graphics.present();
     }
 }

src/stack.zig

@@ -1,17 +1,6 @@
 const io = @import("./io.zig");
 const std = @import("std");
 
-///
-/// 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,
-};
-
 pub fn Fixed(comptime Element: type) type {
     return struct {
         filled: usize = 0,
@@ -24,7 +13,7 @@ pub fn Fixed(comptime Element: type) type {
         ///
         /// Note that this will raise a compilation error if [Element] is not `u8`.
         ///
-        pub fn asWriter(self: *Self) io.Writer {
+        pub fn writer(self: *Self) io.Writer {
             if (Element != u8) @compileError("Cannot coerce fixed stack of type " ++
                 @typeName(Element) ++ " into a Writer");
 
@@ -91,6 +80,17 @@ pub fn Fixed(comptime Element: type) type {
     };
 }
 
+///
+/// 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 "fixed stack" {
     const testing = @import("std").testing;
     const expectError = testing.expectError;
@@ -112,7 +112,7 @@ test "fixed stack" {
 
     try expectEqual(stack.count(), 0);
 
-    const writer = stack.asWriter();
+    const writer = stack.writer();
 
     try expectEqual(writer.write(&.{0, 0, 0, 0}), 4);
     try expectEqual(writer.writeByte(0), false);

src/sys.zig

@@ -10,163 +10,31 @@ const std = @import("std");
 ///
 ///
 ///
-pub const EventLoop = packed struct {
-    current_request: ?*Request = null,
+pub const EventLoop = struct {
 
-    ///
-    /// [OpenError.NotFound] is used as a catch-all for any hardware or software-specific reason for
-    /// failing to open a given file. This includes file-system restrictions surrounding a specific
-    /// file as well as it simply not existing.
-    ///
-    /// [OpenError.OutOfFiles] occurs when there are no more resources available to open further
-    /// files. As a result, some open files must be closed before more may be opened.
-    ///
-    pub const OpenError = error {
-        NotFound,
-        OutOfFiles,
 };
 
 ///
-    /// Indicates what kind of access the consumer logic has to a file.
-    ///
-    /// [OpenMode.read] is for reading from an existing file from the start.
-    ///
-    /// [OpenMode.overwrite] is for deleting the contents of a file, or creating an empty one if no
-    /// such file exists, and writing to it from the start.
-    ///
-    /// [OpenMode.append] is for writing additional contents to a file, creating an empty one if no
-    /// such file exists, on the end of whatever it already contains.
-    ///
-    pub const OpenMode = enum {
-        readonly,
-        overwrite,
-        append,
-    };
-
-    const Request = struct {
-        next: ?*Request = null,
-        frame: anyframe,
-
-        message: union(enum) {
-            close: struct {
-                file: *FileAccess,
-            },
-
-            open: struct {
-                file_system: FileSystem,
-                path: *const Path,
-                mode: OpenMode,
-                file: OpenError!*FileAccess = error.OutOfFiles,
-            },
-        },
-    };
-
-    const max_files = 512;
-
-    ///
-    /// Asynchronously closes `file_access` via `event_loop`.
-    ///
-    /// *Note* that `file_access` must have been opened by `event_loop` for it to be closed by it,
-    /// otherwise it will cause undefined behavior.
-    ///
-    pub fn close(event_loop: *EventLoop, file_access: *FileAccess) void {
-        var request = Request{
-            .frame = @frame(),
-            .message = .{.close = @ptrCast(*ext.SDL_RWops, file_access)},
-        };
-
-        suspend if (event_loop.current_request) |current_request| {
-            current_request.next = &request;
-        } else {
-            event_loop.current_request = &request;
-        };
-    }
-
 ///
 ///
+pub const FileAccess = opaque {
     ///
-    pub fn open(event_loop: *EventLoop, file_system: FileSystem,
-        path: Path, mode: OpenMode) OpenError!*FileAccess {
-
-        var request = Request{
-            .frame = @frame(),
-
-            .message = .{
-                .open = .{
-                    .file_system = file_system,
-                    .path = &path,
-                    .mode = mode,
-                },
-            },
-        };
-
-        suspend if (event_loop.current_request) |current_request| {
-            current_request.next = &request;
-        } else {
-            event_loop.current_request = &request;
-        };
-
-        return @ptrCast(*FileAccess, try request.message.open.file);
-    }
-
+    /// 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 tick(event_loop: *EventLoop) void {
-        while (event_loop.current_request) |request| {
-            switch (request.message) {
-                .close => |*close| {
-                    // Swallow file close errors.
-                    _ = ext.SDL_RWclose(@ptrCast(*ext.SDL_RWops, @alignCast(@alignOf(ext.SDL_RWops), close.file)));
-                },
+    pub fn size(file_access: *FileAccess, event_loop: *EventLoop) FileError!usize {
+        const origin_cursor = try app.tellFile(file_access);
 
-                .open => |*open| {
-                    switch (open.file_system) {
-                        .data => {
-                            var zeroed_path_buffer = std.mem.zeroes([4096]u8);
-                            var zeroed_path = stack.Fixed(u8){.buffer = &zeroed_path_buffer};
+        try app.seekFile(file_access, .tail, 0);
 
-                            zeroed_path.push('.') catch continue;
+        const ending_cursor = try app.tellFile(file_access);
 
-                            _ = open.path.write(zeroed_path.asWriter());
+        try app.seekFile(file_access, .head, origin_cursor);
 
-                            zeroed_path.push(0) catch continue;
-
-                            // TODO: Access TAR file.
-                        },
-
-                        .user => {
-                            var zeroed_path_buffer = std.mem.zeroes([4096]u8);
-                            var zeroed_path = stack.Fixed(u8){.buffer = &zeroed_path_buffer};
-
-                            zeroed_path.pushAll("/home/kayomn/.local/share") catch continue;
-
-                            _ = open.path.write(zeroed_path.asWriter());
-
-                            zeroed_path.push(0) catch continue;
-
-                            open.file = @ptrCast(?*FileAccess, ext.SDL_RWFromFile(&zeroed_path_buffer, switch (open.mode) {
-                                .readonly => "rb",
-                                .overwrite => "wb",
-                                .append => "ab",
-                            })) orelse error.NotFound;
-                        },
-                    }
-                },
-            }
-
-            resume request.frame;
-
-            event_loop.current_request = request.next;
-        }
+        return ending_cursor;
     }
 };
 
-///
-///
-///
-pub const FileAccess = opaque {};
-
 ///
 /// 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
@@ -176,14 +44,6 @@ pub const FileError = error {
     Inaccessible,
 };
 
-///
-///
-///
-pub const FileSystem = enum {
-    data,
-    user,
-};
-
 ///
 /// Platform-agnostic mechanism for accessing files on any of the virtual file-systems supported by
 /// Ona.
@@ -199,6 +59,13 @@ pub const Path = struct {
         TooLong,
     };
 
+    ///
+    ///
+    ///
+    pub fn isComplete(path: Path) bool {
+        return (path.length != 0) and (path.buffer[0] == '/');
+    }
+
     ///
     /// Returns `true` if the length of `path` is empty, otherwise `false`.
     ///
@@ -213,6 +80,80 @@ pub const Path = struct {
         return std.mem.eql(u8, this.buffer[0 .. this.length], that.buffer[0 .. that.length]);
     }
 
+    ///
+    /// Creates and returns a [Path] value in the file system indicated by `file_system` from the
+    /// path components in `component_groups`.
+    ///
+    pub fn from(file_system: FileSystem, component_groups: []const []const u8) Error!Path {
+        var path = Path{
+            .file_system = file_system,
+            .buffer = std.mem.zeroes([max]u8),
+            .length = 0,
+        };
+
+        for (component_groups) |first_component_group,
+            first_component_group_index| if (first_component_group.len != 0) {
+
+            var first_component_root_offset = @as(usize, 0);
+
+            if (component_group[0] == '/') {
+                comptime if (max < 1) unreachable;
+
+                path.buffer[path.length] = '/';
+                path.length += 1;
+                first_component_root_offset = 1;
+            }
+
+            var first_components = mem.Spliterator(u8){
+                .source = first_component_group[first_component_root_offset ..
+                    (first_component_group.len - first_component_root_offset)],
+
+                .delimiter = "/",
+            };
+
+            while (first_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 (path.length == max) return error.TooLong;
+
+                path.buffer[path.length] = '/';
+                path.length += 1;
+            };
+
+            const second_component_group_index = (first_component_group_index + 1);
+
+            for (component_groups[second_component_group_index .. (component_groups.len -
+                second_component_group_index)]) |component_group| if (component_group.len != 0) {
+
+                var components = mem.Spliterator(u8){
+                    .source = component_group,
+                    .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 (path.length == max) return error.TooLong;
+
+                    path.buffer[path.length] = '/';
+                    path.length += 1;
+                };
+            };
+        };
+
+        return path;
+    }
+
     ///
     /// The maximum possible byte-length of a [Path].
     ///
@@ -222,31 +163,17 @@ pub const Path = struct {
     ///
     pub const max = 1000;
 
-    ///
-    ///
-    ///
-    pub fn parseJoins(path: Path, joins: []const []const u8) Error!Path {
-        _ = path;
-        _ = joins;
-
-        return Path{
-            .buffer = std.mem.zeroes([max]u8),
-            .length = 0
-        };
-    }
-
     ///
     ///
     ///
     pub fn write(path: Path, writer: io.Writer) bool {
         return (writer.write(path.buffer[0 .. path.length]) == path.length);
     }
+};
 
 ///
 ///
 ///
-    pub const root = Path{
-        .buffer = [_]u8{'/'} ** max,
-        .length = 1,
-    };
-};
+pub fn runGraphics(comptime ErrorUnion: anytype, run: fn (*App) ErrorUnion!void) void {
+
+}