libmpeg3/bitstream.c

   1 #include "mpeg3private.h"
   2 #include "mpeg3protos.h"
   3
   4 #include <stdlib.h>
   5
   6 mpeg3_bits_t* mpeg3bits_new_stream(mpeg3_t *file, mpeg3_demuxer_t *demuxer)
   7 {
   8         mpeg3_bits_t *stream = malloc(sizeof(mpeg3_bits_t));
   9         stream->bfr = 0;
  10         stream->bfr_size = 0;
  11         stream->bit_number = 0;
  12         stream->file = file;
  13         stream->demuxer = demuxer;
  14         stream->input_ptr = 0;
  15         return stream;
  16 }
  17
  18 int mpeg3bits_delete_stream(mpeg3_bits_t* stream)
  19 {
  20         free(stream);
  21         return 0;
  22 }
  23
  24
  25 /* Fill a buffer.  Only works if bit_number is on an 8 bit boundary */
  26 int mpeg3bits_read_buffer(mpeg3_bits_t* stream, unsigned char *buffer, int bytes)
  27 {
  28         int result, i = 0;
  29         while(stream->bit_number > 0)
  30         {
  31                 stream->bit_number -= 8;
  32                 mpeg3demux_read_prev_char(stream->demuxer);
  33         }
  34
  35         stream->bit_number = 0;
  36         stream->bfr_size = 0;
  37         stream->bfr = 0;
  38         result = mpeg3demux_read_data(stream->demuxer, buffer, bytes);
  39         return result;
  40 }
  41
  42 /* For mp3 decompression use a pointer in a buffer for getbits. */
  43 int mpeg3bits_use_ptr(mpeg3_bits_t* stream, unsigned char *buffer)
  44 {
  45         stream->bfr_size = stream->bit_number = 0;
  46         stream->bfr = 0;
  47         stream->input_ptr = buffer;
  48         return 0;
  49 }
  50
  51 /* Go back to using the demuxer for getbits in mp3. */
  52 int mpeg3bits_use_demuxer(mpeg3_bits_t* stream)
  53 {
  54         if(stream->input_ptr)
  55         {
  56                 stream->bfr_size = stream->bit_number = 0;
  57                 stream->input_ptr = 0;
  58                 stream->bfr = 0;
  59         }
  60
  61         return 0;
  62 }
  63
  64 /* Reconfigure for reverse operation */
  65 /* Default is forward operation */
  66 void mpeg3bits_start_reverse(mpeg3_bits_t* stream)
  67 {
  68         int i;
  69         for(i = 0; i < stream->bfr_size; i += 8)
  70         {
  71                 if(stream->input_ptr)
  72                         stream->input_ptr--;
  73                 else
  74                         mpeg3demux_read_prev_char(stream->demuxer);
  75         }
  76 }
  77
  78 /* Reconfigure for forward operation */
  79 void mpeg3bits_start_forward(mpeg3_bits_t* stream)
  80 {
  81         int i;
  82
  83 // If already at the bof, the buffer is already invalid.
  84         if(stream->demuxer && mpeg3bits_bof(stream))
  85         {
  86                 stream->bfr_size = 0;
  87                 stream->bit_number = 0;
  88                 stream->bfr = 0;
  89                 stream->input_ptr = 0;
  90                 mpeg3demux_read_char(stream->demuxer);
  91         }
  92         else
  93         for(i = 0; i < stream->bfr_size; i += 8)
  94         {
  95                 if(stream->input_ptr)
  96                         stream->input_ptr++;
  97                 else
  98                         mpeg3demux_read_char(stream->demuxer);
  99         }
 100 }
 101
 102 /* Erase the buffer with the next 4 bytes in the file. */
 103 int mpeg3bits_refill(mpeg3_bits_t* stream)
 104 {
 105         stream->bit_number = 32;
 106         stream->bfr_size = 32;
 107
 108         if(stream->input_ptr)
 109         {
 110                 stream->bfr = (unsigned int)(*stream->input_ptr++) << 24;
 111                 stream->bfr |= (unsigned int)(*stream->input_ptr++) << 16;
 112                 stream->bfr |= (unsigned int)(*stream->input_ptr++) << 8;
 113                 stream->bfr |= *stream->input_ptr++;
 114         }
 115         else
 116         {
 117                 stream->bfr = mpeg3demux_read_char(stream->demuxer) << 24;
 118                 stream->bfr |= mpeg3demux_read_char(stream->demuxer) << 16;
 119                 stream->bfr |= mpeg3demux_read_char(stream->demuxer) << 8;
 120                 stream->bfr |= mpeg3demux_read_char(stream->demuxer);
 121         }
 122         return mpeg3demux_eof(stream->demuxer);
 123 }
 124
 125 /* Erase the buffer with the previous 4 bytes in the file. */
 126 int mpeg3bits_refill_backwards(mpeg3_bits_t* stream)
 127 {
 128         stream->bit_number = 0;
 129         stream->bfr_size = 32;
 130         stream->bfr = mpeg3demux_read_prev_char(stream->demuxer);
 131         stream->bfr |= (unsigned int)mpeg3demux_read_prev_char(stream->demuxer) << 8;
 132         stream->bfr |= (unsigned int)mpeg3demux_read_prev_char(stream->demuxer) << 16;
 133         stream->bfr |= (unsigned int)mpeg3demux_read_prev_char(stream->demuxer) << 24;
 134         return mpeg3demux_eof(stream->demuxer);
 135 }
 136
 137 int mpeg3bits_byte_align(mpeg3_bits_t *stream)
 138 {
 139         stream->bit_number = (stream->bit_number + 7) & 0xf8;
 140         return 0;
 141 }
 142
 143 int mpeg3bits_open_title(mpeg3_bits_t* stream, int title)
 144 {
 145         stream->bfr_size = stream->bit_number = 0;
 146         return mpeg3demux_open_title(stream->demuxer, title);
 147 }
 148
 149 /*
 150  * int mpeg3bits_seek_time(mpeg3_bits_t* stream, double time_position)
 151  * {
 152  *      stream->bfr_size = stream->bit_number = 0;
 153  *      return mpeg3demux_seek_time(stream->demuxer, time_position);
 154  * }
 155  */
 156
 157 int mpeg3bits_seek_byte(mpeg3_bits_t* stream, int64_t position)
 158 {
 159         stream->bfr_size = stream->bit_number = 0;
 160         return mpeg3demux_seek_byte(stream->demuxer, position);
 161 }
 162
 163 void mpeg3bits_reset(mpeg3_bits_t *stream)
 164 {
 165         stream->bfr_size = stream->bit_number = 0;
 166 }
 167
 168 int64_t mpeg3bits_tell(mpeg3_bits_t* stream)
 169 {
 170         return mpeg3demux_tell_byte(stream->demuxer);
 171 }
 172
 173 int mpeg3bits_getbitoffset(mpeg3_bits_t *stream)
 174 {
 175         return stream->bit_number & 7;
 176 }
 177