ADPCM: added a Write function to decoder so that it implements io.Writer,

and also so that it can decode adpcm of arbitrary length.
Updated test and decode command to use Write.

audio/adpcm/adpcm.go

@@ -227,8 +227,9 @@ func (e *Encoder) calcHead(sample []byte) (int, error) {
 // 		- First two bytes contain the first 16-bit sample uncompressed.
 // 		- Third byte is the decoder's starting index for the block, the fourth is padding and ignored.
 func (e *Encoder) EncodeBlock(block []byte) (int, error) {
+	writ := 0
 	if len(block) != PcmBS {
-		return 0, fmt.Errorf("unsupported block size. Given: %v, expected: %v, ie. 505 16-bit PCM samples", len(block), PcmBS)
+		return writ, fmt.Errorf("unsupported block size. Given: %v, expected: %v, ie. 505 16-bit PCM samples", len(block), PcmBS)
 	}
 
 	writ, err := e.calcHead(block[0:2])
@@ -249,6 +250,50 @@ func (e *Encoder) EncodeBlock(block []byte) (int, error) {
 	return writ, nil
 }
 
+// DecodeBlock takes a slice of 256 bytes, each byte after the first 4 should contain two ADPCM encoded nibbles.
+// It outputs the resulting decoded (decompressed) 16-bit PCM samples to the decoder's dest writer.
+func (d *Decoder) DecodeBlock(block []byte) (int, error) {
+	writ := 0
+	if len(block) != AdpcmBS {
+		return writ, fmt.Errorf("unsupported block size. Given: %v, expected: %v", len(block), AdpcmBS)
+	}
+
+	// Initialize decoder with first 4 bytes of the block.
+	d.pred = int16(binary.LittleEndian.Uint16(block[0:2]))
+	d.index = int16(block[2])
+	d.step = stepTable[d.index]
+	writ, err := d.dest.Write(block[0:2])
+	if err != nil {
+		return writ, err
+	}
+
+	// For each byte, seperate it into two nibbles (each nibble is a compressed sample),
+	// then decode each nibble and output the resulting 16-bit samples.
+	for i := 4; i < AdpcmBS; i++ {
+		twoNibs := block[i]
+		nib2 := byte(twoNibs >> 4)
+		nib1 := byte((nib2 << 4) ^ twoNibs)
+
+		firstBytes := make([]byte, 2)
+		binary.LittleEndian.PutUint16(firstBytes, uint16(d.decodeSample(nib1)))
+		writS, err := d.dest.Write(firstBytes)
+		writ += writS
+		if err != nil {
+			return writ, err
+		}
+
+		secondBytes := make([]byte, 2)
+		binary.LittleEndian.PutUint16(secondBytes, uint16(d.decodeSample(nib2)))
+		writS, err = d.dest.Write(secondBytes)
+		writ += writS
+		if err != nil {
+			return writ, err
+		}
+	}
+
+	return writ, nil
+}
+
 func (e *Encoder) Write(inPcm []byte) (int, error) {
 	numBlocks := len(inPcm) / PcmBS
 	writ := 0
@@ -264,34 +309,17 @@ func (e *Encoder) Write(inPcm []byte) (int, error) {
 	return writ, nil
 }
 
-// DecodeBlock takes a slice of 256 bytes, each byte after the first 4 should contain two ADPCM encoded nibbles.
-// It outputs the resulting decoded (decompressed) 16-bit PCM samples to the decoder's dest writer.
-func (d *Decoder) DecodeBlock(block []byte) error {
-	if len(block) != AdpcmBS {
-		return fmt.Errorf("unsupported block size. Given: %v, expected: %v", len(block), AdpcmBS)
+func (d *Decoder) Write(inAdpcm []byte) (int, error) {
+	numBlocks := len(inAdpcm) / AdpcmBS
+	writ := 0
+	for i := 0; i < numBlocks; i++ {
+		block := inAdpcm[AdpcmBS*i : AdpcmBS*(i+1)]
+		writB, err := d.DecodeBlock(block)
+		writ += writB
+		if err != nil {
+			return writ, err
+		}
 	}
 
-	// Initialize decoder with first 4 bytes of the block.
-	d.pred = int16(binary.LittleEndian.Uint16(block[0:2]))
-	d.index = int16(block[2])
-	d.step = stepTable[d.index]
-	d.dest.Write(block[0:2])
-
-	// For each byte, seperate it into two nibbles (each nibble is a compressed sample),
-	// then decode each nibble and output the resulting 16-bit samples.
-	for i := 4; i < AdpcmBS; i++ {
-		twoNibs := block[i]
-		nib2 := byte(twoNibs >> 4)
-		nib1 := byte((nib2 << 4) ^ twoNibs)
-
-		firstBytes := make([]byte, 2)
-		binary.LittleEndian.PutUint16(firstBytes, uint16(d.decodeSample(nib1)))
-		d.dest.Write(firstBytes)
-
-		secondBytes := make([]byte, 2)
-		binary.LittleEndian.PutUint16(secondBytes, uint16(d.decodeSample(nib2)))
-		d.dest.Write(secondBytes)
-	}
-
-	return nil
+	return writ, nil
 }

audio/adpcm/adpcm_test.go

@@ -75,12 +75,9 @@ func TestDecodeBlock(t *testing.T) {
 	numBlocks := len(comp) / AdpcmBS
 	decoded := bytes.NewBuffer(make([]byte, 0, PcmBS*numBlocks))
 	dec := NewDecoder(decoded)
-	for i := 0; i < numBlocks; i++ {
-		block := comp[AdpcmBS*i : AdpcmBS*(i+1)]
-		err := dec.DecodeBlock(block)
-		if err != nil {
-			t.Errorf("Unable to write to decoder: %v", err)
-		}
+	_, err = dec.Write(comp)
+	if err != nil {
+		t.Errorf("Unable to write to decoder: %v", err)
 	}
 
 	// Read expected pcm file.

exp/adpcm/decode-pcm/decode-pcm.go

@@ -57,12 +57,9 @@ func main() {
 	numBlocks := len(comp) / adpcm.AdpcmBS
 	decoded := bytes.NewBuffer(make([]byte, 0, adpcm.PcmBS*numBlocks))
 	dec := adpcm.NewDecoder(decoded)
-	for i := 0; i < numBlocks; i++ {
-		block := comp[adpcm.AdpcmBS*i : adpcm.AdpcmBS*(i+1)]
-		err := dec.DecodeBlock(block)
-		if err != nil {
-			log.Fatal(err)
-		}
+	_, err = dec.Write(comp)
+	if err != nil {
+		log.Fatal(err)
 	}
 
 	// Save pcm to file.