tiny.gif.DecodePlan

1pub const Plan = struct {2    input_bytes: usize,3    input_hash: u64,4    width: u32,5    height: u32,6    canvas_pixels: usize,7    canvas_rgba8_bytes: usize,8    frames: usize,9    frame_pixels: usize,10    compressed_bytes: usize,11    retained_rgba8_bytes: usize,1213    pub fn inspect(bytes: []const u8, bounds: Bounds) Error!Plan {14        var reader = stream.Reader{ .bytes = bytes };15        const header = try stream.readHeader(&reader);16        const canvas_pixels = try multiplied(header.width, header.height);17        if (canvas_pixels > bounds.canvas_pixels) return error.CanvasPixelCapacityExceeded;18        const canvas_rgba8_bytes = try multiplied(canvas_pixels, 4);1920        var frame_count: usize = 0;21        var frame_pixels: usize = 0;22        var compressed_bytes: usize = 0;23        var retained_rgba8_bytes: usize = 0;24        var trailer = false;2526        while (!trailer) {27            switch (try reader.byte()) {28                0x21 => {29                    const label = try reader.byte();30                    if (label == 0xf9) {31                        _ = try stream.readControl(&reader);32                    } else {33                        try stream.skipSubBlocks(&reader);34                    }35                },36                0x2c => {37                    const descriptor = try stream.readDescriptor(&reader, header.global_table);38                    const descriptor_pixels = descriptor.pixelCount();39                    if (descriptor_pixels > bounds.frame_pixels) return error.FramePixelCapacityExceeded;40                    frame_pixels = @max(frame_pixels, descriptor_pixels);4142                    frame_count = std.math.add(usize, frame_count, 1) catch return error.CapacityOverflow;43                    if (frame_count > bounds.frames) return error.FrameCapacityExceeded;4445                    const compressed = try stream.readSubBlocks(&reader, null, bounds.compressed_bytes);46                    compressed_bytes = @max(compressed_bytes, compressed);4748                    retained_rgba8_bytes = std.math.add(49                        usize,50                        retained_rgba8_bytes,51                        canvas_rgba8_bytes,52                    ) catch return error.CapacityOverflow;53                    if (retained_rgba8_bytes > bounds.retained_rgba8_bytes) {54                        return error.RetainedRgba8CapacityExceeded;55                    }56                },57                0x3b => trailer = true,58                else => return error.InvalidDescriptor,59            }60        }6162        if (frame_count == 0) return error.NoFrames;63        return .{64            .input_bytes = bytes.len,65            .input_hash = std.hash.Wyhash.hash(0, bytes),66            .width = header.width,67            .height = header.height,68            .canvas_pixels = canvas_pixels,69            .canvas_rgba8_bytes = canvas_rgba8_bytes,70            .frames = frame_count,71            .frame_pixels = frame_pixels,72            .compressed_bytes = compressed_bytes,73            .retained_rgba8_bytes = retained_rgba8_bytes,74        };75    }7677    pub fn exactBounds(self: Plan) Bounds {78        return .{79            .canvas_pixels = self.canvas_pixels,80            .frame_pixels = self.frame_pixels,81            .frames = self.frames,82            .compressed_bytes = self.compressed_bytes,83            .retained_rgba8_bytes = self.retained_rgba8_bytes,84        };85    }86};

1pub const DecodePlan = decode.Plan;