merge format and formatdecenc into formats (#222)

pkg/formats/rtpmjpeg/headers/jpeg.go

@@ -0,0 +1,51 @@
+package headers
+
+import (
+	"fmt"
+)
+
+// JPEG is a JPEG header.
+type JPEG struct {
+	TypeSpecific   uint8
+	FragmentOffset uint32
+	Type           uint8
+	Quantization   uint8
+	Width          int
+	Height         int
+}
+
+// Unmarshal decodes the header.
+func (h *JPEG) Unmarshal(byts []byte) (int, error) {
+	if len(byts) < 8 {
+		return 0, fmt.Errorf("buffer is too short")
+	}
+
+	h.TypeSpecific = byts[0]
+	h.FragmentOffset = uint32(byts[1])<<16 | uint32(byts[2])<<8 | uint32(byts[3])
+
+	h.Type = byts[4]
+	if h.Type != 1 {
+		return 0, fmt.Errorf("Type %d is not supported", h.Type)
+	}
+
+	h.Quantization = byts[5]
+	if h.Quantization != 255 {
+		return 0, fmt.Errorf("Q %d is not supported", h.Quantization)
+	}
+
+	h.Width = int(byts[6]) * 8
+	h.Height = int(byts[7]) * 8
+
+	return 8, nil
+}
+
+// Marshal encodes the header.
+func (h JPEG) Marshal(byts []byte) []byte {
+	byts = append(byts, h.TypeSpecific)
+	byts = append(byts, []byte{byte(h.FragmentOffset >> 16), byte(h.FragmentOffset >> 8), byte(h.FragmentOffset)}...)
+	byts = append(byts, h.Type)
+	byts = append(byts, h.Quantization)
+	byts = append(byts, byte(h.Width/8))
+	byts = append(byts, byte(h.Height/8))
+	return byts
+}