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