zlibx: Make DecompressSized return the number of bytes consumed

2 files changed, 12 insertions, 11 deletions

diff --git a/internal/zlibx/decompress.go b/internal/zlibx/decompress.go
index 23fae8fa..6bb5d45c 100644
--- a/internal/zlibx/decompress.go
+++ b/internal/zlibx/decompress.go
@@ -10,44 +10,45 @@ import (
 )
 
 func Decompress(src []byte) (bufpool.Buffer, error) {
-	return DecompressSized(src, 0)
+	out, _, err := DecompressSized(src, 0)
+	return out, err
 }
 
-func DecompressSized(src []byte, sizeHint int) (bufpool.Buffer, error) {
+func DecompressSized(src []byte, sizeHint int) (bufpool.Buffer, int, error) {
 	if len(src) < 6 {
-		return bufpool.Buffer{}, io.ErrUnexpectedEOF
+		return bufpool.Buffer{}, 0, io.ErrUnexpectedEOF
 	}
 
 	cmf := src[0]
 	flg := src[1]
 	if (cmf&0x0f != zlibDeflate) || (cmf>>4 > zlibMaxWindow) || (binary.BigEndian.Uint16(src[:2])%31 != 0) {
-		return bufpool.Buffer{}, ErrHeader
+		return bufpool.Buffer{}, 0, ErrHeader
 	}
 
 	offset := 2
 	if flg&0x20 != 0 {
-		return bufpool.Buffer{}, ErrHeader
+		return bufpool.Buffer{}, 0, ErrHeader
 	}
 
 	if len(src[offset:]) < 4 {
-		return bufpool.Buffer{}, io.ErrUnexpectedEOF
+		return bufpool.Buffer{}, 0, io.ErrUnexpectedEOF
 	}
 
 	deflateData := src[offset:]
 	out, consumed, err := flatex.DecompressSized(deflateData, sizeHint)
 	if err != nil {
-		return bufpool.Buffer{}, err
+		return bufpool.Buffer{}, 0, err
 	}
 
 	checksumPos := offset + consumed
 	if checksumPos+4 > len(src) {
 		out.Release()
-		return bufpool.Buffer{}, io.ErrUnexpectedEOF
+		return bufpool.Buffer{}, 0, io.ErrUnexpectedEOF
 	}
 	expected := binary.BigEndian.Uint32(src[checksumPos : checksumPos+4])
 	if expected != adler32.Checksum(out.Bytes()) {
 		out.Release()
-		return bufpool.Buffer{}, ErrChecksum
+		return bufpool.Buffer{}, 0, ErrChecksum
 	}
-	return out, nil
+	return out, checksumPos + 4, nil
 }
diff --git a/internal/zlibx/decompress_test.go b/internal/zlibx/decompress_test.go
index 2b9f0672..bea348d2 100644
--- a/internal/zlibx/decompress_test.go
+++ b/internal/zlibx/decompress_test.go
@@ -155,7 +155,7 @@ func TestDecompressSizedUsesHint(t *testing.T) {
 	compressed := compressZlib(t, payload)
 
 	const hint = 1 << 20
-	out, err := DecompressSized(compressed, hint)
+	out, _, err := DecompressSized(compressed, hint)
 	if err != nil {
 		t.Fatalf("DecompressSized: %v", err)
 	}