91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
|
/*
|
||
|
|
* decuncmp.c
|
||
|
|
*
|
||
|
|
* Decoding uncompressed blocks
|
||
|
|
*/
|
||
|
|
#include "decoder.h"
|
||
|
|
|
||
|
|
|
||
|
|
int decode_uncompressed_block(t_decoder_context *context, long bufpos, int amount_to_decode)
|
||
|
|
{
|
||
|
|
long bytes_decoded = 0;
|
||
|
|
long bufpos_end;
|
||
|
|
long decode_residue;
|
||
|
|
ulong bufpos_start;
|
||
|
|
ulong end_copy_pos;
|
||
|
|
byte * p;
|
||
|
|
|
||
|
|
bufpos_start = bufpos;
|
||
|
|
bufpos_end = bufpos + amount_to_decode;
|
||
|
|
|
||
|
|
p = context->dec_input_curpos;
|
||
|
|
|
||
|
|
while (bufpos < bufpos_end)
|
||
|
|
{
|
||
|
|
if (p >= context->dec_end_input_pos)
|
||
|
|
return -1; // input overflow
|
||
|
|
|
||
|
|
context->dec_mem_window[bufpos++] = *p++;
|
||
|
|
}
|
||
|
|
|
||
|
|
context->dec_input_curpos = p;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Make sure the MAX_MATCH bytes starting at window[window_size]
|
||
|
|
* are always the same as the first MAX_MATCH bytes starting at
|
||
|
|
* window[0]. This is for our optimisation in decverb.c and
|
||
|
|
* decalign.c which allows us to not have to & window_mask all the
|
||
|
|
* time.
|
||
|
|
*/
|
||
|
|
end_copy_pos = (((MAX_MATCH) < (bufpos_end)) ? (MAX_MATCH) : (bufpos_end));
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Keep copying until we hit MAX_MATCH or the number of bytes
|
||
|
|
* we decoded
|
||
|
|
*/
|
||
|
|
while (bufpos_start < end_copy_pos)
|
||
|
|
{
|
||
|
|
context->dec_mem_window[bufpos_start + context->dec_window_size] =
|
||
|
|
context->dec_mem_window[bufpos_start];
|
||
|
|
bufpos_start++;
|
||
|
|
}
|
||
|
|
|
||
|
|
decode_residue = bufpos - bufpos_end;
|
||
|
|
|
||
|
|
bufpos &= context->dec_window_mask;
|
||
|
|
context->dec_bufpos = bufpos;
|
||
|
|
|
||
|
|
return (int) decode_residue;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
bool handle_beginning_of_uncompressed_block(t_decoder_context *context)
|
||
|
|
{
|
||
|
|
int i;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* we want to read the 16 bits already in bitbuf, so backtrack
|
||
|
|
* the input pointer by 2 bytes.
|
||
|
|
*/
|
||
|
|
context->dec_input_curpos -= 2;
|
||
|
|
|
||
|
|
if (context->dec_input_curpos+4 >= context->dec_end_input_pos)
|
||
|
|
return false;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* update LRU repeated offset list
|
||
|
|
*/
|
||
|
|
for (i = 0; i < NUM_REPEATED_OFFSETS; i++)
|
||
|
|
{
|
||
|
|
context->dec_last_matchpos_offset[i] =
|
||
|
|
((ulong) *( (byte *) context->dec_input_curpos) ) |
|
||
|
|
((ulong) *( ((byte *) context->dec_input_curpos) + 1) << 8) |
|
||
|
|
((ulong) *( ((byte *) context->dec_input_curpos) + 2) << 16) |
|
||
|
|
((ulong) *( ((byte *) context->dec_input_curpos) + 3) << 24);
|
||
|
|
|
||
|
|
context->dec_input_curpos += 4; /* increment by 4 bytes */
|
||
|
|
}
|
||
|
|
|
||
|
|
return true;
|
||
|
|
}
|