safely stage video frames

internal/renderer/renderer.go

@@ -3,17 +3,20 @@ package renderer
 import (
 	"errors"
 	"fmt"
-	"mxl-player/internal/sdl"
 	"unsafe"
 
+	"mxl-player/internal/sdl"
+
 	"github.com/christerso/vulkan-go/vk"
 )
 
-// Raises by swapchain creation, whem windos is minimized
-var ErrMinimized = errors.New("window minimized")
-
-// ErrOutOfDate is returned by DrawFrame when the swapchain needs recreation.
-var ErrOutOfDate = errors.New("swapchain out of date")
+var (
+	// Raises by swapchain creation, whem windos is minimized
+	ErrMinimized = errors.New("window minimized")
+	// ErrOutOfDate is returned by DrawFrame when the swapchain needs recreation.
+	ErrOutOfDate         = errors.New("swapchain out of date")
+	ErrInvalidVideoFrame = errors.New("invalid video frame")
+)
 
 // shader push-constants block
 type PushConstants struct {
@@ -392,6 +395,64 @@ func (r *Renderer) RecreateBuffers(newSize vk.DeviceSize) error {
 	return nil
 }
 
+func (r *Renderer) StageFrame(
+	payload []byte,
+	width uint32,
+	height uint32,
+	stride uint32,
+) error {
+	frameSize, err := validateFramePayload(len(payload), width, height, stride)
+	if err != nil {
+		return err
+	}
+
+	if frameSize != r.FrameSize() {
+		// RecreateBuffers waits for the device to become idle.
+		if err := r.RecreateBuffers(frameSize); err != nil {
+			return fmt.Errorf("resize video buffers: %w", err)
+		}
+	} else {
+		// The previous submitted frame may still read the mapped staging buffer.
+		if err := r.dev.WaitFence(r.inFlight, ^uint64(0)); err != nil {
+			return fmt.Errorf("wait before staging video: %w", err)
+		}
+	}
+
+	vk.CopyToMapped(
+		r.StagingMapped(),
+		payload[:int(frameSize)],
+	)
+	return nil
+}
+
+func validateFramePayload(
+	payloadLen int,
+	width uint32,
+	height uint32,
+	stride uint32,
+) (vk.DeviceSize, error) {
+	if width == 0 || height == 0 || stride == 0 {
+		return 0, fmt.Errorf(
+			"%w: dimensions=%dx%d stride=%d",
+			ErrInvalidVideoFrame,
+			width,
+			height,
+			stride,
+		)
+	}
+
+	requiredSize := uint64(stride) * uint64(height)
+	if payloadLen < 0 || requiredSize > uint64(payloadLen) {
+		return 0, fmt.Errorf(
+			"%w: payload=%d required=%d",
+			ErrInvalidVideoFrame,
+			payloadLen,
+			requiredSize,
+		)
+	}
+	return vk.DeviceSize(requiredSize), nil
+}
+
 // DrawFrame acquires an image, records commands, submits, and presents.
 // Returns ErrOutOfDate if the swapchain needs recreation
 func (r *Renderer) DrawFrame(videoW, videoH, stride uint32) error {