audio/mp3: Move side_info_* to Go

audio/mp3/decode_notjs.go

@@ -73,6 +73,18 @@ func Get_Bytes(num C.unsigned, data *C.unsigned) C.unsigned {
 	return C.OK
 }
 
+func getBytes(num int) ([]int, error) {
+	r := make([]int, num)
+	for i := 0; i < num; i++ {
+		v := Get_Byte()
+		if v == eof {
+			return r, io.EOF
+		}
+		r[i] = int(v)
+	}
+	return r, nil
+}
+
 //export Get_Filepos
 func Get_Filepos() C.unsigned {
 	if len(readerCache) == 0 && readerEOF {

audio/mp3/pdmp3.c

@@ -117,13 +117,11 @@ static int Read_Main_L3(void);
 static int Set_Main_Pos(unsigned bit_pos);
 
 static unsigned Get_Main_Pos(void);
-static unsigned Get_Side_Bits(unsigned number_of_bits);
 
 static void audio_write(unsigned *samples,unsigned nsamples,int sample_rate);
 static void audio_write_raw(unsigned *samples,unsigned nsamples);
 static void Decode_L3_Init_Song(void);
 static void Error(const char *s,int e);
-static void Get_Sideinfo(unsigned sideinfo_size);
 static void IMDCT_Win(float in[18],float out[36],unsigned block_type);
 static void L3_Antialias(unsigned gr,unsigned ch);
 static void L3_Frequency_Inversion(unsigned gr,unsigned ch);
@@ -463,11 +461,7 @@ static unsigned hsynth_init = 1,synth_init = 1,
   g_main_data_vec[2*1024],/* Large static data */
   *g_main_data_ptr,/* Pointer into the reservoir */
   g_main_data_idx,/* Index into the current byte(0-7) */
-  g_main_data_top = 0,/* Number of bytes in reservoir(0-1024) */
-  /* Bit reservoir for side info */
-  side_info_vec[32+4],
-  *side_info_ptr,  /* Pointer into the reservoir */
-  side_info_idx;  /* Index into the current byte(0-7) */
+  g_main_data_top = 0;/* Number of bytes in reservoir(0-1024) */
 
 /* Scale factor band indices
  *
@@ -1090,26 +1084,6 @@ static unsigned Get_Main_Pos(void){
   return(pos);
 }
 
-/**Description: reads 'number_of_bits' from buffer which contains side_info.
-* Parameters: number_of_bits to read(max 16)
-* Return value: The bits are returned in the LSB of the return value.
-* Author: Krister Lagerström(krister@kmlager.com) **/
-static unsigned Get_Side_Bits(unsigned number_of_bits){
-  unsigned tmp;
-
-  /* Form a word of the next four bytes */                   //TODO endianness?
-  tmp =(side_info_ptr[0] << 24) |(side_info_ptr[1] << 16) |
-       (side_info_ptr[2] <<  8) |(side_info_ptr[3] <<  0);
-  /* Remove bits already used */
-  tmp = tmp << side_info_idx;
-  /* Remove bits after the desired bits */
-  tmp = tmp >>(32 - number_of_bits);
-  /* Update pointers */
-  side_info_ptr +=(side_info_idx + number_of_bits) >> 3;
-  side_info_idx =(side_info_idx + number_of_bits) & 0x07;
-  return(tmp);
-}
-
 /**Description: TBD
 * Parameters: TBD
 * Return value: TBD
@@ -1119,22 +1093,6 @@ static void Error(const char *s,int e){
   exit(e);
 }
 
-/**Description: Reads sideinfo from bitstream into buffer for Get_Side_Bits.
-* Parameters: TBD
-* Return value: TBD
-* Author: Krister Lagerström(krister@kmlager.com) **/
-static void Get_Sideinfo(unsigned sideinfo_size){
-  if(Get_Bytes(sideinfo_size,side_info_vec) != OK) {
-    ERR("\nCouldn't read sideinfo %d bytes at pos %d\n",
-   sideinfo_size,Get_Filepos());
-    return;
-  }
-
-  side_info_ptr = &(side_info_vec[0]);
-  side_info_idx = 0;
-
-}
-
 /**Description: reinit decoder before playing new song,or seeking current song.
 * Parameters: None
 * Return value: None

audio/mp3/pdmp3.h

@@ -23,6 +23,8 @@ size_t writeToWriter(void* data, int size);
 
 unsigned Get_Main_Bit(void);
 unsigned Get_Main_Bits(unsigned number_of_bits);
+void Get_Sideinfo(unsigned sideinfo_size);
+unsigned Get_Side_Bits(unsigned number_of_bits);
 
 int Huffman_Decode(unsigned table_num, int32_t* x, int32_t*y, int32_t* v, int32_t* w);
 

audio/mp3/sideinfo.go

@@ -0,0 +1,65 @@
+// Copyright 2017 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !js
+
+package mp3
+
+// #include "pdmp3.h"
+import "C"
+
+import (
+	"fmt"
+)
+
+// A sideInfo is a bit reservoir for side info
+type sideInfo struct {
+	vec []int
+	idx int // Index into the current byte(0-7)
+}
+
+var theSideInfo sideInfo
+
+//export Get_Sideinfo
+func Get_Sideinfo(size C.unsigned) {
+	var err error
+	theSideInfo.vec, err = getBytes(int(size))
+	if err != nil {
+		g_error = fmt.Errorf("mp3: couldn't read sideinfo %d bytes at pos %d: %v",
+			size, Get_Filepos(), err)
+		return
+	}
+	theSideInfo.idx = 0
+}
+
+//export Get_Side_Bits
+func Get_Side_Bits(num C.unsigned) C.unsigned {
+	// Form a word of the next four bytes
+	// TODO: endianness?
+	b := make([]int, 4)
+	for i := range b {
+		if len(theSideInfo.vec) > i {
+			b[i] = theSideInfo.vec[i]
+		}
+	}
+	tmp := (uint32(b[0]) << 24) | (uint32(b[1]) << 16) | (uint32(b[2]) << 8) | (uint32(b[3]) << 0)
+	// Remove bits already used
+	tmp = tmp << uint(theSideInfo.idx)
+	// Remove bits after the desired bits
+	tmp = tmp >> (32 - num)
+	// Update pointers
+	theSideInfo.vec = theSideInfo.vec[(theSideInfo.idx+int(num))>>3:]
+	theSideInfo.idx = (theSideInfo.idx + int(num)) & 0x07
+	return C.unsigned(tmp)
+}