/* initialize buffer, call once before first getbits or showbits */
void _apeg_initialize_buffer(APEG_LAYER *layer)
{
layer->Incnt = 0;
layer->got_last = FALSE;
switch(layer->buffer_type)
{
case DISK_BUFFER:
// (Re)open the file
if(layer->pf)
pack_fclose(layer->pf);
layer->pf = pack_fopen(layer->fname, F_READ);
if(!layer->pf)
{
sprintf(apeg_error, "Couldn't open %s", layer->fname);
apeg_error_jump(NULL);
}
break;
case MEMORY_BUFFER:
layer->mem_data.buf -= layer->buffer_size -
layer->mem_data.bytes_left;
layer->mem_data.bytes_left = layer->buffer_size;
break;
case USER_BUFFER:
if(!layer->ext_data.request || !layer->ext_data.skip ||
!layer->ext_data.init)
apeg_error_jump("Unable to request data");
layer->buffer_size = layer->ext_data.init(layer->ext_data.ptr);
if(layer->buffer_size <= 0)
apeg_error_jump("Data init failed");
layer->buffer_size = (layer->buffer_size+3) & (~3);
break;
default:
sprintf(apeg_error, "Unknown buffer type: %d", layer->buffer_type);
apeg_error_jump(NULL);
}
layer->Bfr = 0;
layer->Incnt = 0;
layer->Rdmax = 0;
if(layer->system_stream_flag != MPEG_SYSTEM)
layer->Rdmax = ~0u;
if(layer->system_stream_flag != OGG_SYSTEM)
apeg_flush_bits(layer, 0); /* fills valid data into Bfr */
}
static int Get_Chroma_DC_dct_diff(APEG_LAYER *layer)
{
int code, size;
/* decode length */
code = show_bits(layer, 5);
if (code<31)
{
/* Table B-13, dct_dc_size_chrominance, codes 00xxx ... 11110 */
static const VLCtab DCchromtab0[32] = {
{0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2},
{1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2},
{2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2},
{3, 3}, {3, 3}, {3, 3}, {3, 3}, {4, 4}, {4, 4}, {5, 5}, {0, 0}
};
size = DCchromtab0[code].val;
apeg_flush_bits8(layer, DCchromtab0[code].len);
if(size == 0)
return 0;
}
else
{
/* Table B-13, dct_dc_size_chrominance, codes 111110xxxx ... 1111111111 */
static const VLCtab DCchromtab1[32] = {
{6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, { 6, 6}, { 6, 6},
{6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, { 6, 6}, { 6, 6},
{7, 7}, {7, 7}, {7, 7}, {7, 7}, {7, 7}, {7, 7}, { 7, 7}, { 7, 7},
{8, 8}, {8, 8}, {8, 8}, {8, 8}, {9, 9}, {9, 9}, {10,10}, {11,10}
};
code = show_bits(layer, 10) - 992;
size = DCchromtab1[code].val;
apeg_flush_bits(layer, DCchromtab1[code].len);
}
{
const int dct_diff = apeg_get_bits(layer, size);
const int f = ((dct_diff >> (size-1))&1)^1;
return dct_diff - ((f<<size) - f);
/* int dct_diff = apeg_get_bits(layer, size);
if (( dct_diff & (1 << (size-1)) ) == 0)
return dct_diff - ((1<<size) - 1);
return dct_diff;*/
}
}
