audio/mp3: Move Read_Frame to Go

audio/mp3/decode_notjs.go

@@ -37,29 +37,6 @@ var (
 	writer      io.Writer
 )
 
-//export Read_CRC
-func Read_CRC() C.int {
-	buf := make([]int, 2)
-	n := 0
-	var err error
-	for n < 2 && err == nil {
-		nn, err2 := getBytes(buf[n:])
-		n += nn
-		err = err2
-	}
-	if err == io.EOF {
-		if n < 2 {
-			return C.ERROR
-		}
-		return C.OK
-	}
-	if err != nil {
-		g_error = err
-		return C.ERROR
-	}
-	return C.OK
-}
-
 func getByte() (uint8, error) {
 	for len(readerCache) == 0 && !readerEOF {
 		buf := make([]uint8, 4096)
@@ -117,13 +94,17 @@ func decode(r io.Reader, w io.Writer) error {
 	reader = r
 	writer = w
 	for Get_Filepos() != eof {
-		if C.Read_Frame() == C.OK {
+		err := readFrame()
+		if err == nil {
 			C.Decode_L3()
 			continue
 		}
 		if Get_Filepos() == eof {
 			break
 		}
+		if err != nil {
+			return err
+		}
 		return errors.New("mp3: not enough maindata to decode frame")
 	}
 	return g_error

audio/mp3/pdmp3.c

@@ -204,43 +204,6 @@ int Decode_L3(void){
   return(OK);   /* Done */
 }
 
-/**Description: Search for next frame and read it into  buffer. Main data in
-   this frame is saved for two frames since it might be needed by them.
-* Parameters: None
-* Return value: OK if a frame is successfully read,ERROR otherwise.
-* Author: Krister Lagerström(krister@kmlager.com) **/
-int Read_Frame(void){
-  unsigned first = 0;
-
-  if(Get_Filepos() == 0) Decode_L3_Init_Song();
-  /* Try to find the next frame in the bitstream and decode it */
-  if(Read_Header() != OK) return(ERROR);
-#ifdef DEBUG
-  { static int framenum = 0;
-    printf("\nFrame %d\n",framenum++);
-    dmp_fr(&g_frame_header);
-  }
-    DBG("Starting decode,Layer: %d,Rate: %6d,Sfreq: %05d",
-         g_frame_header.layer,
-         g_mpeg1_bitrates[g_frame_header.layer - 1][g_frame_header.bitrate_index],
-         g_sampling_frequency[g_frame_header.sampling_frequency]);
-#endif
-  /* Get CRC word if present */
-  if((g_frame_header.protection_bit==0)&&(Read_CRC()!=OK)) return(ERROR);
-  if(g_frame_header.layer == 3) {  /* Get audio data */
-    Read_Audio_L3();  /* Get side info */
-    dmp_si(&g_frame_header,&g_side_info); /* DEBUG */
-    /* If there's not enough main data in the bit reservoir,
-     * signal to calling function so that decoding isn't done! */
-    /* Get main data(scalefactors and Huffman coded frequency data) */
-    if(Read_Main_L3() != OK) return(ERROR);
-  }else{
-    ERR("Only layer 3(!= %d) is supported!\n",g_frame_header.layer);
-    return(ERROR);
-  }
-  return(OK);
-}
-
 /**Description: TBD
 * Parameters: TBD
 * Return value: TBD
@@ -250,14 +213,6 @@ static void Error(const char *s,int e){
   exit(e);
 }
 
-/**Description: reinit decoder before playing new song,or seeking current song.
-* Parameters: None
-* Return value: None
-* Author: Krister Lagerström(krister@kmlager.com) **/
-static void Decode_L3_Init_Song(void){
-  synth_init = 1;
-}
-
 /**Description: output audio data
 * Parameters: Pointers to the samples,the number of samples
 * Return value: None

audio/mp3/pdmp3.h

@@ -86,7 +86,6 @@ t_sf_band_indices;
 
 unsigned Get_Filepos(void);
 int Decode_L3(void);
-int Read_Frame(void);
 size_t writeToWriter(void* data, int size);
 
 unsigned Get_Main_Pos(void);

audio/mp3/read.go

@@ -28,6 +28,52 @@ import (
 	"io"
 )
 
+func readCRC() error {
+	buf := make([]int, 2)
+	n := 0
+	var err error
+	for n < 2 && err == nil {
+		nn, err2 := getBytes(buf[n:])
+		n += nn
+		err = err2
+	}
+	if err == io.EOF {
+		if n < 2 {
+			return fmt.Errorf("mp3: unexpected EOF at readCRC")
+		}
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func readFrame() error {
+	if err := readHeader(); err != nil {
+		return err
+	}
+	/* Get CRC word if present */
+	if C.g_frame_header.protection_bit == 0 {
+		if err := readCRC(); err != nil {
+			return err
+		}
+	}
+	if C.g_frame_header.layer == 3 { /* Get audio data */
+		Read_Audio_L3() /* Get side info */
+		/* If there's not enough main data in the bit reservoir,
+		 * signal to calling function so that decoding isn't done! */
+		/* Get main data(scalefactors and Huffman coded frequency data) */
+		if Read_Main_L3() != C.OK {
+			// TODO: Fix this
+			return fmt.Errorf("mp3: Read_Main_L3")
+		}
+	} else {
+		return fmt.Errorf("mp3: Only layer 3(!= %d) is supported!", C.g_frame_header.layer)
+	}
+	return nil
+}
+
 func isHeader(header uint32) bool {
 	const C_SYNC = 0xffe00000
 	if (header & C_SYNC) != C_SYNC {
@@ -44,8 +90,7 @@ func isHeader(header uint32) bool {
 	return true
 }
 
-//export Read_Header
+func readHeader() error {
-func Read_Header() C.int {
 	/* Get the next four bytes from the bitstream */
 	buf := make([]int, 4)
 	n := 0
@@ -56,10 +101,10 @@ func Read_Header() C.int {
 		err = err2
 	}
 	if n < 4 {
-		if err != io.EOF {
+		if err == io.EOF {
-			g_error = err
+			return fmt.Errorf("mp3: unexpected EOF at readHeader")
 		}
-		return C.ERROR
+		return err
 	}
 	b1 := uint32(buf[0])
 	b2 := uint32(buf[1])
@@ -75,10 +120,10 @@ func Read_Header() C.int {
 		/* Get one new byte from the bitstream */
 		b, err := getByte()
 		if err != nil {
-			if err != io.EOF {
+			if err == io.EOF {
-				g_error = err
+				return fmt.Errorf("mp3: unexpected EOF at readHeader")
 			}
-			return C.ERROR
+			return err
 		}
 		b4 = uint32(b)
 		header = (b1 << 24) | (b2 << 16) | (b3 << 8) | (b4 << 0)
@@ -100,33 +145,27 @@ func Read_Header() C.int {
 	C.g_frame_header.emphasis = C.uint((header & 0x00000003) >> 0)
 	/* Check for invalid values and impossible combinations */
 	if C.g_frame_header.id != 3 {
-		g_error = fmt.Errorf("mp3: ID must be 3\nHeader word is 0x%08x at file pos %d",
+		return fmt.Errorf("mp3: ID must be 3\nHeader word is 0x%08x at file pos %d",
 			header, C.Get_Filepos())
-		return C.ERROR
 	}
 	if C.g_frame_header.bitrate_index == 0 {
-		g_error = fmt.Errorf("mp3: Free bitrate format NIY!\nHeader word is 0x%08x at file pos %d",
+		return fmt.Errorf("mp3: Free bitrate format NIY!\nHeader word is 0x%08x at file pos %d",
 			header, Get_Filepos())
-		return C.ERROR
-		//exit(1);
 	}
 	if C.g_frame_header.bitrate_index == 15 {
-		g_error = fmt.Errorf("mp3: bitrate_index = 15 is invalid!\nHeader word is 0x%08x at file pos %d",
+		return fmt.Errorf("mp3: bitrate_index = 15 is invalid!\nHeader word is 0x%08x at file pos %d",
 			header, Get_Filepos())
-		return C.ERROR
 	}
 	if C.g_frame_header.sampling_frequency == 3 {
-		g_error = fmt.Errorf("mp3: sampling_frequency = 3 is invalid! Header word is 0x%08x at file pos %d",
+		return fmt.Errorf("mp3: sampling_frequency = 3 is invalid! Header word is 0x%08x at file pos %d",
 			header, Get_Filepos())
-		return C.ERROR
 	}
 	if C.g_frame_header.layer == 0 {
-		g_error = fmt.Errorf("mp3: layer = 0 is invalid! Header word is 0x%08x at file pos %d",
+		return fmt.Errorf("mp3: layer = 0 is invalid! Header word is 0x%08x at file pos %d",
 			header, Get_Filepos())
-		return C.ERROR
 	}
 	C.g_frame_header.layer = 4 - C.g_frame_header.layer
-	return C.OK
+	return nil
 }
 
 func readHuffman(part_2_start, gr, ch int) error {