CPU generator

internal/generator/cpu.go

@@ -0,0 +1,93 @@
+package generator
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+type YCbCr10 struct {
+	Y  uint32
+	Cb uint32
+	Cr uint32
+}
+
+type PixelSampler func(x, y, width, height, frameIndex int) YCbCr10
+
+type CPUGenerator struct {
+	width   int
+	height  int
+	sampler PixelSampler
+}
+
+func NewCPUGenerator(
+	width, height uint,
+	sampler PixelSampler,
+) (*CPUGenerator, error) {
+	if width == 0 || height == 0 {
+		return nil, fmt.Errorf(
+			"width and height must be greater than 0, got: %dx%d",
+			width,
+			height,
+		)
+	}
+	if width%6 != 0 {
+		return nil, fmt.Errorf(
+			"width must be divisible by 6, got: %d",
+			width,
+		)
+	}
+	if sampler == nil {
+		return nil, fmt.Errorf("pixel sampler is nil")
+	}
+
+	return &CPUGenerator{
+		width:   int(width),
+		height:  int(height),
+		sampler: sampler,
+	}, nil
+}
+
+func (g *CPUGenerator) GenerateFrame(dest []byte, frameIndex int) error {
+	frameSize := (g.width / 6) * g.height * 16
+	if len(dest) < frameSize {
+		return fmt.Errorf(
+			"cpu: destination is too small: got %d bytes, need %d",
+			len(dest),
+			frameSize,
+		)
+	}
+
+	const componentMask uint32 = 0x3ff
+	offset := 0
+	for y := 0; y < g.height; y++ {
+		for x := 0; x < g.width; x += 6 {
+			var pixels [6]YCbCr10
+			for i := range pixels {
+				pixels[i] = g.sampler(x+i, y, g.width, g.height, frameIndex)
+			}
+
+			word0 := pixels[0].Cb&componentMask |
+				(pixels[0].Y&componentMask)<<10 |
+				(pixels[0].Cr&componentMask)<<20
+			word1 := pixels[1].Y&componentMask |
+				(pixels[2].Cb&componentMask)<<10 |
+				(pixels[2].Y&componentMask)<<20
+			word2 := pixels[2].Cr&componentMask |
+				(pixels[3].Y&componentMask)<<10 |
+				(pixels[4].Cb&componentMask)<<20
+			word3 := pixels[4].Y&componentMask |
+				(pixels[4].Cr&componentMask)<<10 |
+				(pixels[5].Y&componentMask)<<20
+
+			binary.LittleEndian.PutUint32(dest[offset:], word0)
+			binary.LittleEndian.PutUint32(dest[offset+4:], word1)
+			binary.LittleEndian.PutUint32(dest[offset+8:], word2)
+			binary.LittleEndian.PutUint32(dest[offset+12:], word3)
+			offset += 16
+		}
+	}
+
+	return nil
+}
+
+func (g *CPUGenerator) Close() error { return nil }