codec/mjpeg/jpeg.go: added writeHuffman function to write JPEG huffman tables to an io.Writer.

codec/mjpeg/jpeg.go

@@ -24,7 +24,10 @@ LICENSE
 
 package mjpeg
 
-import "io"
+import (
+	"fmt"
+	"io"
+)
 
 // JPEG marker codes.
 const (
@@ -37,11 +40,36 @@ const (
 	sof0 = 0xc0 // Baseline
 )
 
-// putMarker writes an JPEG marker with code to w.
+// writeMarker writes an JPEG marker with code to w.
-func putMarker(w io.Writer, code byte) error {
+func writeMarker(w io.Writer, code byte) error {
 	_, err := w.Write([]byte{0xff, code})
 	if err != nil {
 		return err
 	}
 	return nil
 }
+
+// writeHuffman write a JPEG huffman table to w.
+func writeHuffman(w io.Writer, class, id int, bits, values []byte) error {
+	_, err := w.Write([]byte{byte(class<<4 | id)})
+	if err != nil {
+		return fmt.Errorf("could not write class and id: %w", err)
+	}
+
+	var n int
+	for i := 1; i <= 16; i++ {
+		n += int(bits[i])
+	}
+
+	_, err = w.Write(bits[1:17])
+	if err != nil {
+		return fmt.Errorf("could not write first lot of huffman bytes: %w", err)
+	}
+
+	_, err = w.Write(values[0:n])
+	if err != nil {
+		return fmt.Errorf("could not write second lot of huffman bytes: %w", err)
+	}
+
+	return nil
+}