adpcm: encoder and decoder structs are now exported

codec/adpcm/adpcm.go

@@ -27,7 +27,7 @@ LICENSE
 	Reference algorithms for ADPCM compression and decompression are in part 6.
 */
 
-// Package adpcm provides encoder and decoder structs to encode and decode PCM to and from ADPCM.
+// Package adpcm provides Encoder and Decoder structs to encode and decode PCM to and from ADPCM.
 package adpcm
 
 import (
@@ -69,8 +69,8 @@ var stepTable = []int16{
 	32767,
 }
 
-// encoder is used to encode to ADPCM from PCM data.
-type encoder struct {
+// Encoder is used to encode to ADPCM from PCM data.
+type Encoder struct {
 	// dst is the destination for encoded data.
 	dst io.Writer
 
@@ -79,8 +79,8 @@ type encoder struct {
 	index int16
 }
 
-// decoder is used to decode from ADPCM to PCM data.
-type decoder struct {
+// Decoder is used to decode from ADPCM to PCM data.
+type Decoder struct {
 	// dst is the output buffer that implements io.Writer and io.Bytewriter, ie. where the decoded PCM data is written to.
 	dst io.Writer
 
@@ -90,9 +90,9 @@ type decoder struct {
 	step  int16
 }
 
-// NewEncoder retuns a new ADPCM encoder.
-func NewEncoder(dst io.Writer) *encoder {
-	e := encoder{
+// NewEncoder retuns a new ADPCM Encoder.
+func NewEncoder(dst io.Writer) *Encoder {
+	e := Encoder{
 		dst: dst,
 	}
 	return &e
@@ -100,7 +100,7 @@ func NewEncoder(dst io.Writer) *encoder {
 
 // encodeSample takes a single 16 bit PCM sample and
 // returns a byte of which the last 4 bits are an encoded ADPCM nibble.
-func (e *encoder) encodeSample(sample int16) byte {
+func (e *Encoder) encodeSample(sample int16) byte {
 	// Find difference between the sample and the previous estimation.
 	delta := capAdd16(sample, -e.est)
 
@@ -144,10 +144,10 @@ func (e *encoder) encodeSample(sample int16) byte {
 	return nib
 }
 
-// calcHead sets the state for the encoder by running the first sample through
-// the encoder, and writing the first sample to the encoder's io.Writer (dst).
-// It returns the number of bytes written to the encoder's io.Writer (dst) along with any errors.
-func (e *encoder) calcHead(sample []byte, pad bool) (int, error) {
+// calcHead sets the state for the Encoder by running the first sample through
+// the Encoder, and writing the first sample to the Encoder's io.Writer (dst).
+// It returns the number of bytes written to the Encoder's io.Writer (dst) along with any errors.
+func (e *Encoder) calcHead(sample []byte, pad bool) (int, error) {
 	// Check that we are given 1 sample.
 	if len(sample) != byteDepth {
 		return 0, fmt.Errorf("length of given byte array is: %v, expected: %v", len(sample), byteDepth)
@@ -176,10 +176,10 @@ func (e *encoder) calcHead(sample []byte, pad bool) (int, error) {
 	return n, nil
 }
 
-// init initializes the encoder's estimation to the first uncompressed sample and the index to
+// init initializes the Encoder's estimation to the first uncompressed sample and the index to
 // point to a suitable quantizer step size.
 // The suitable step size is the closest step size in the stepTable to half the absolute difference of the first two samples.
-func (e *encoder) init(samples []byte) {
+func (e *Encoder) init(samples []byte) {
 	int1 := int16(binary.LittleEndian.Uint16(samples[:byteDepth]))
 	int2 := int16(binary.LittleEndian.Uint16(samples[byteDepth:initBytes]))
 	e.est = int1
@@ -197,10 +197,10 @@ func (e *encoder) init(samples []byte) {
 }
 
 // Write takes a slice of bytes of arbitrary length representing pcm and encodes it into adpcm.
-// It writes its output to the encoder's dst.
+// It writes its output to the Encoder's dst.
 // The number of bytes written out is returned along with any error that occured.
-func (e *encoder) Write(b []byte) (int, error) {
-	// Check that pcm has enough data to initialize decoder.
+func (e *Encoder) Write(b []byte) (int, error) {
+	// Check that pcm has enough data to initialize Decoder.
 	pcmLen := len(b)
 	if pcmLen < initBytes {
 		return 0, fmt.Errorf("length of given byte array must be >= %v", initBytes)
@@ -240,9 +240,9 @@ func (e *encoder) Write(b []byte) (int, error) {
 	return n, nil
 }
 
-// NewDecoder retuns a new ADPCM decoder.
-func NewDecoder(dst io.Writer) *decoder {
-	d := decoder{
+// NewDecoder retuns a new ADPCM Decoder.
+func NewDecoder(dst io.Writer) *Decoder {
+	d := Decoder{
 		dst: dst,
 	}
 	return &d
@@ -250,7 +250,7 @@ func NewDecoder(dst io.Writer) *decoder {
 
 // decodeSample takes a byte, the last 4 bits of which contain a single
 // 4 bit ADPCM nibble, and returns a 16 bit decoded PCM sample.
-func (d *decoder) decodeSample(nibble byte) int16 {
+func (d *Decoder) decodeSample(nibble byte) int16 {
 	// Calculate difference.
 	var diff int16
 	if nibble&4 != 0 {
@@ -289,10 +289,10 @@ func (d *decoder) decodeSample(nibble byte) int16 {
 }
 
 // Write takes a slice of bytes of arbitrary length representing adpcm and decodes it into pcm.
-// It writes its output to the decoder's dst.
+// It writes its output to the Decoder's dst.
 // The number of bytes written out is returned along with any error that occured.
-func (d *decoder) Write(b []byte) (int, error) {
-	// Initialize decoder with first 4 bytes of b.
+func (d *Decoder) Write(b []byte) (int, error) {
+	// Initialize Decoder with first 4 bytes of b.
 	d.est = int16(binary.LittleEndian.Uint16(b[:byteDepth]))
 	d.index = int16(b[byteDepth])
 	d.step = stepTable[d.index]