Encode lpc fix for unary (#68)

* Support writing Unaries above 255

* Improve unary test error messages

* Update comment on "44 - ...flac" test

enc_test.go

@@ -96,11 +96,11 @@ func TestEncode(t *testing.T) {
 		"testdata/flac-test-files/subset/41 - 6 channels (5.1).flac",
 		"testdata/flac-test-files/subset/42 - 7 channels (6.1).flac",
 		"testdata/flac-test-files/subset/43 - 8 channels (7.1).flac",
-		// TODO: check why there is an audio sample diff (they look identical,
-		// except for using `sample_rate: 0b1100 (end of header (8 bit*1000))`
-		// for orig and `sample_rate: 192000 (0b11)` for mewkiz/flac); orig md5:
-		// cdf531d4d4b95233986bc499518a89db, output md5:
-		// 678a704da087bf8e98a19f1ad47ca359.
+		// NOTE: the only diff is that "44 - ...flac" uses `0b1100 (end of header
+		// (8 bit*1000))` to encode the sample rate at the end of the header,
+		// whereas mewkiz/flac encodes it directly `192000 (0b11)`. Notably, the
+		// computed md5 hash of the decoded audio samples is identical
+		// (MD5: cdf531d4d4b95233986bc499518a89db). Thus, ignore the test case.
 		//"testdata/flac-test-files/subset/44 - 8-channel surround, 192kHz, 24 bit, using only 32nd order predictors.flac",
 		"testdata/flac-test-files/subset/45 - no total number of samples set.flac",
 		"testdata/flac-test-files/subset/46 - no min-max framesize set.flac",

internal/bits/unary.go

@@ -43,11 +43,14 @@ func (br *Reader) ReadUnary() (x uint64, err error) {
 //	5 => 000001
 //	6 => 0000001
 func WriteUnary(bw *bitio.Writer, x uint64) error {
-	bits := uint64(1)
-	n := byte(1)
-	for ; x > 0; x-- {
-		n++
+	for ; x > 8; x -= 8 {
+		if err := bw.WriteByte(0x0); err != nil {
+			return err
+		}
 	}
+
+	bits := uint64(1)
+	n := byte(x + 1)
 	if err := bw.WriteBits(bits, n); err != nil {
 		return err
 	}

internal/bits/unary_test.go

@@ -0,0 +1,36 @@
+package bits_test
+
+import (
+	"bytes"
+	"github.com/icza/bitio"
+	"github.com/mewkiz/flac/internal/bits"
+	"testing"
+)
+
+func TestUnary(t *testing.T) {
+	w := new(bytes.Buffer)
+	bw := bitio.NewWriter(w)
+
+	var want uint64
+	for ; want < 1000; want++ {
+		// Write unary
+		if err := bits.WriteUnary(bw, want); err != nil {
+			t.Fatalf("unable to write unary; %v", err)
+		}
+		// Flush buffer
+		if err := bw.Close(); err != nil {
+			t.Fatalf("unable to close (flush) the bit buffer; %v", err)
+		}
+
+		// Read written unary
+		r := bits.NewReader(w)
+		got, err := r.ReadUnary()
+		if err != nil {
+			t.Fatalf("unable to read unary; %v", err)
+		}
+
+		if got != want {
+			t.Fatalf("the written and read unary doesn't match the original value, got: %v, expected: %v", got, want)
+		}
+	}
+}