From 29f4acd7fe1d65eb576eb03139806cecb9ed43d2 Mon Sep 17 00:00:00 2001
From: Trek H <trek.hopton@gmail.com>
Date: Thu, 28 Feb 2019 13:12:41 +1030
Subject: [PATCH] ADPCM: decoder now writes to bytes.Buffer instead of
 returning a byte array, tests updated.

---
 stream/adpcm/adpcm.go      | 13 ++++++-------
 stream/adpcm/adpcm_test.go |  9 ++++-----
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/stream/adpcm/adpcm.go b/stream/adpcm/adpcm.go
index 326f6758..9e9bb324 100644
--- a/stream/adpcm/adpcm.go
+++ b/stream/adpcm/adpcm.go
@@ -247,17 +247,16 @@ func (e *Encoder) EncodeBlock(block []byte) error {
 
 // DecodeBlock takes a slice of 256 bytes, each byte should contain two ADPCM encoded nibbles.
 // It returns a byte slice containing the resulting decoded (uncompressed) 16-bit PCM samples.
-func (d *Decoder) DecodeBlock(block []byte) ([]byte, error) {
+func (d *Decoder) DecodeBlock(block []byte) error {
 	bSize := 256
 	if len(block) != bSize {
-		return nil, fmt.Errorf("unsupported block size. Given: %v, expected: %v", len(block), bSize)
+		return fmt.Errorf("unsupported block size. Given: %v, expected: %v", len(block), bSize)
 	}
 
-	var result []byte
 	d.pred = int16(binary.LittleEndian.Uint16(block[0:2]))
 	d.index = int16(block[2])
 	d.step = stepTable[d.index]
-	result = append(result, block[0:2]...)
+	d.dest.Write(block[0:2])
 
 	for i := 4; i < len(block); i++ {
 		originalSample := block[i]
@@ -266,12 +265,12 @@ func (d *Decoder) DecodeBlock(block []byte) ([]byte, error) {
 
 		firstBytes := make([]byte, 2)
 		binary.LittleEndian.PutUint16(firstBytes, uint16(d.decodeSample(firstSample)))
-		result = append(result, firstBytes...)
+		d.dest.Write(firstBytes)
 
 		secondBytes := make([]byte, 2)
 		binary.LittleEndian.PutUint16(secondBytes, uint16(d.decodeSample(secondSample)))
-		result = append(result, secondBytes...)
+		d.dest.Write(secondBytes)
 	}
 
-	return result, nil
+	return nil
 }
diff --git a/stream/adpcm/adpcm_test.go b/stream/adpcm/adpcm_test.go
index 9ab1ac55..f82b421b 100644
--- a/stream/adpcm/adpcm_test.go
+++ b/stream/adpcm/adpcm_test.go
@@ -81,15 +81,14 @@ func TestDecodeBlock(t *testing.T) {
 	inBSize := 256
 	numBlocks := len(comp) / inBSize
 	outBSize := 2 + (inBSize-4)*4 // 2 bytes are copied, 2 are used as block header info, the remaining bytes are decompressed 1:4
-	decoded := make([]byte, 0, outBSize*numBlocks)
-	dec := NewDecoder(nil)
+	decoded := bytes.NewBuffer(make([]byte, 0, outBSize*numBlocks))
+	dec := NewDecoder(decoded)
 	for i := 0; i < numBlocks; i++ {
 		block := comp[inBSize*i : inBSize*(i+1)]
-		decBlock, err := dec.DecodeBlock(block)
+		err := dec.DecodeBlock(block)
 		if err != nil {
 			log.Fatal(err)
 		}
-		decoded = append(decoded, decBlock...)
 	}
 
 	//read expected pcm file
@@ -98,7 +97,7 @@ func TestDecodeBlock(t *testing.T) {
 		t.Errorf("Unable to read expected PCM file: %v", err)
 	}
 
-	if !bytes.Equal(decoded, exp) {
+	if !bytes.Equal(decoded.Bytes(), exp) {
 		t.Error("PCM generated does not match expected PCM")
 	}
 }