ADPCM: 'writ' variables changed to 'n' as per convention. Documentation improved.

audio/adpcm/adpcm.go

@@ -191,7 +191,8 @@ func (d *decoder) decodeSample(nibble byte) int16 {
 }
 
 // calcHead sets the state for the encoder by running the first sample through
-// the encoder, and writing the first sample.
+// the encoder, and writing the first sample to the encoder's io.Writer (dest).
+// It returns the number of bytes written to the encoder's io.Writer (dest) along with any errors.
 func (e *encoder) calcHead(sample []byte) (int, error) {
 	// Check that we are given 1 16-bit sample (2 bytes).
 	const sampSize = 2
@@ -202,40 +203,40 @@ func (e *encoder) calcHead(sample []byte) (int, error) {
 	intSample := int16(binary.LittleEndian.Uint16(sample))
 	e.encodeSample(intSample)
 
-	writ, err := e.dest.Write(sample)
+	n, err := e.dest.Write(sample)
 	if err != nil {
-		return writ, err
+		return n, err
 	}
 
 	err = e.dest.WriteByte(byte(uint16(e.index)))
 	if err != nil {
-		return writ, err
+		return n, err
 	}
-	writ++
+	n++
 
 	err = e.dest.WriteByte(byte(0x00))
 	if err != nil {
-		return writ, err
+		return n, err
 	}
-	writ++
+	n++
-	return writ, nil
+	return n, nil
 }
 
 // encodeBlock takes a slice of 1010 bytes (505 16-bit PCM samples).
-// It outputs encoded (compressed) bytes (each byte containing two ADPCM nibbles) to the encoder's dest writer.
+// It writes encoded (compressed) bytes (each byte containing two ADPCM nibbles) to the encoder's io.Writer (dest).
+// The number of bytes written is returned along with any errors.
 // Note: nibbles are output in little endian order, eg. n1n0 n3n2 n5n4...
 // Note: first 4 bytes are for initializing the decoder before decoding a block.
 // 		- 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 writ, fmt.Errorf("unsupported block size. Given: %v, expected: %v, ie. 505 16-bit PCM samples", len(block), PcmBS)
+		return 0, 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])
+	n, err := e.calcHead(block[0:2])
 	if err != nil {
-		return writ, err
+		return n, err
 	}
 
 	for i := 3; i < PcmBS; i += 4 {
@@ -243,29 +244,29 @@ func (e *encoder) encodeBlock(block []byte) (int, error) {
 		nib2 := e.encodeSample(int16(binary.LittleEndian.Uint16(block[i+1 : i+3])))
 		err = e.dest.WriteByte(byte((nib2 << 4) | nib1))
 		if err != nil {
-			return writ, err
+			return n, err
 		}
-		writ++
+		n++
 	}
 
-	return writ, nil
+	return n, 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.
+// It writes the resulting decoded (decompressed) 16-bit PCM samples to the decoder's io.Writer (dest).
+// The number of bytes written is returned along with any errors.
 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)
+		return 0, 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])
+	n, err := d.dest.Write(block[0:2])
 	if err != nil {
-		return writ, err
+		return n, err
 	}
 
 	// For each byte, seperate it into two nibbles (each nibble is a compressed sample),
@@ -277,22 +278,22 @@ func (d *decoder) decodeBlock(block []byte) (int, error) {
 
 		firstBytes := make([]byte, 2)
 		binary.LittleEndian.PutUint16(firstBytes, uint16(d.decodeSample(nib1)))
-		writS, err := d.dest.Write(firstBytes)
+		_n, err := d.dest.Write(firstBytes)
-		writ += writS
+		n += _n
 		if err != nil {
-			return writ, err
+			return n, err
 		}
 
 		secondBytes := make([]byte, 2)
 		binary.LittleEndian.PutUint16(secondBytes, uint16(d.decodeSample(nib2)))
-		writS, err = d.dest.Write(secondBytes)
+		_n, err = d.dest.Write(secondBytes)
-		writ += writS
+		n += _n
 		if err != nil {
-			return writ, err
+			return n, err
 		}
 	}
 
-	return writ, nil
+	return n, nil
 }
 
 // Write takes a slice of bytes of arbitrary length representing pcm and encodes in into adpcm.
@@ -300,17 +301,17 @@ func (d *decoder) decodeBlock(block []byte) (int, error) {
 // The number of bytes written out is returned along with any error that occured.
 func (e *encoder) Write(inPcm []byte) (int, error) {
 	numBlocks := len(inPcm) / PcmBS
-	writ := 0
+	n := 0
 	for i := 0; i < numBlocks; i++ {
 		block := inPcm[PcmBS*i : PcmBS*(i+1)]
-		writB, err := e.encodeBlock(block)
+		_n, err := e.encodeBlock(block)
-		writ += writB
+		n += _n
 		if err != nil {
-			return writ, err
+			return n, err
 		}
 	}
 
-	return writ, nil
+	return n, nil
 }
 
 // Write takes a slice of bytes of arbitrary length representing adpcm and decodes in into pcm.
@@ -318,15 +319,15 @@ func (e *encoder) Write(inPcm []byte) (int, error) {
 // The number of bytes written out is returned along with any error that occured.
 func (d *decoder) Write(inAdpcm []byte) (int, error) {
 	numBlocks := len(inAdpcm) / AdpcmBS
-	writ := 0
+	n := 0
 	for i := 0; i < numBlocks; i++ {
 		block := inAdpcm[AdpcmBS*i : AdpcmBS*(i+1)]
-		writB, err := d.decodeBlock(block)
+		_n, err := d.decodeBlock(block)
-		writ += writB
+		n += _n
 		if err != nil {
-			return writ, err
+			return n, err
 		}
 	}
 
-	return writ, nil
+	return n, nil
 }