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/*
* decverb.c * * Decoding verbatim-bit blocks */#include "decoder.h"
static long special_decode_verbatim_block( t_decoder_context *context, long BufPos, int amount_to_decode ){ ulong match_pos; long bufpos_end; int match_length; int c; ulong dec_bitbuf; byte *dec_input_curpos; byte *dec_end_input_pos; byte *dec_mem_window; char dec_bitcount; ulong m;
/*
* Store commonly used variables locally */ dec_bitcount = context->dec_bitcount; dec_bitbuf = context->dec_bitbuf; dec_input_curpos = context->dec_input_curpos; dec_end_input_pos = context->dec_end_input_pos; dec_mem_window = context->dec_mem_window;
bufpos_end = BufPos + amount_to_decode;
/*
* We may overflow by up to MAX_MATCH */ while (BufPos < bufpos_end) { /* decode an item from the main tree */ DECODE_MAIN_TREE(c);
if ((c -= NUM_CHARS) < 0) { /* it's a character */ /* note: c - 256 == c if c is a byte */#ifdef TRACING
TracingLiteral(BufPos, (byte) c);#endif
context->dec_mem_window[BufPos] = (byte) c;
/* we know BufPos < bufpos_end here, so no need to check for overflow */ context->dec_mem_window[context->dec_window_size+BufPos] = (byte) c; BufPos++; } else { /* get match length header */ if ((match_length = c & NUM_PRIMARY_LENGTHS) == NUM_PRIMARY_LENGTHS) { /* get match length footer if necessary */ DECODE_LEN_TREE_NOEOFCHECK(match_length); }
/* get match position slot */ m = c >> NL_SHIFT;
/* read any extra bits for the match position */ if (m > 2) { if (m > 3) /* dec_extra_bits[m] != 0 */ { GET_BITS17_NOEOFCHECK(dec_extra_bits[ m ], match_pos); match_pos += MP_POS_minus2[m]; } else { match_pos = 1; // MP_POS_minus2[3];
}
/*
* Add match base to "extra bits". Our match base * table has 2 subtracted from all the elements. * * This is because encoded positions 0,1,2 denote * repeated offsets. Encoded position 3 denotes * a match 1 character away, 4 encodes 2 away, etc. * Hence the subtraction of 2, which has been * incorporated into the table. */
/* update LRU repeated offset list */ context->dec_last_matchpos_offset[2] = context->dec_last_matchpos_offset[1]; context->dec_last_matchpos_offset[1] = context->dec_last_matchpos_offset[0]; context->dec_last_matchpos_offset[0] = match_pos; } else { /* positions 0, 1, 2 denote repeated offsets */ match_pos = context->dec_last_matchpos_offset[m];
if (m) { context->dec_last_matchpos_offset[m] = context->dec_last_matchpos_offset[0]; context->dec_last_matchpos_offset[0] = match_pos; } }
/* match lengths range from 2...257 */ match_length += MIN_MATCH;
#ifdef EXTRALONGMATCHES
if ( match_length == MAX_MATCH ) {
//
// See detailed explanation in decalign.c
//
ULONG ExtraMatchLength, ExtraMatchLengthResidue;
GET_BITS_NOEOFCHECK( 9, ExtraMatchLength );
if ( ExtraMatchLength & ( 1 << 8 )) { if ( ExtraMatchLength & ( 1 << 7 )) { if ( ExtraMatchLength & ( 1 << 6 )) { ExtraMatchLength = ( ExtraMatchLength & (( 1 << 6 ) - 1 )) << 9; GET_BITS_NOEOFCHECK( 9, ExtraMatchLengthResidue ); ExtraMatchLength |= ExtraMatchLengthResidue; } else { ExtraMatchLength = ( ExtraMatchLength & (( 1 << 6 ) - 1 )) << 6; GET_BITS_NOEOFCHECK( 6, ExtraMatchLengthResidue ); ExtraMatchLength |= ExtraMatchLengthResidue; ExtraMatchLength += ( 1 << 8 ) + ( 1 << 10 ); } } else { ExtraMatchLength = ( ExtraMatchLength & (( 1 << 7 ) - 1 )) << 3; GET_BITS_NOEOFCHECK( 3, ExtraMatchLengthResidue ); ExtraMatchLength |= ExtraMatchLengthResidue; ExtraMatchLength += ( 1 << 8 ); } }
match_length += ExtraMatchLength; }
#endif
#ifdef TRACING
TracingMatch(BufPos, BufPos - match_pos, context->dec_window_size, match_length, m);#endif
/* copy match data */ do { context->dec_mem_window[BufPos] = context->dec_mem_window[(BufPos-match_pos) & context->dec_window_mask];
/* replicate bytes */ if (BufPos < MAX_MATCH) // what does this do? Does it need to be more than MAX_MATCH now?
context->dec_mem_window[context->dec_window_size+BufPos] = context->dec_mem_window[BufPos];
BufPos++; } while (--match_length > 0); } }
context->dec_bitcount = dec_bitcount; context->dec_bitbuf = dec_bitbuf; context->dec_input_curpos = dec_input_curpos;
return BufPos;}
#ifdef ASM_DECODE_VERBATIM_BLOCK
long __cdecl fast_decode_verbatim_block( t_decoder_context *context, long BufPos, int amount_to_decode );
#else /* !ASM_DECODE_VERBATIM_BLOCK */
long fast_decode_verbatim_block(t_decoder_context *context, long BufPos, int amount_to_decode){ ulong match_pos; ulong match_ptr; long bufpos_end; long decode_residue; int match_length; int c; ulong dec_bitbuf; byte *dec_input_curpos; byte *dec_end_input_pos; byte *dec_mem_window; char dec_bitcount; ulong m;
/*
* Store commonly used variables locally */ dec_bitcount = context->dec_bitcount; dec_bitbuf = context->dec_bitbuf; dec_input_curpos = context->dec_input_curpos; dec_end_input_pos = context->dec_end_input_pos; dec_mem_window = context->dec_mem_window;
bufpos_end = BufPos + amount_to_decode;
while (BufPos < bufpos_end) { /* decode an item from the main tree */ DECODE_MAIN_TREE(c);
if ((c -= NUM_CHARS) < 0) { /* it's a character */ /* note: c - 256 == c if c is a byte */#ifdef TRACING
TracingLiteral(BufPos, (byte) c);#endif
context->dec_mem_window[BufPos++] = (byte) c; } else { /* get match length header */ if ((match_length = c & NUM_PRIMARY_LENGTHS) == NUM_PRIMARY_LENGTHS) { /* get match length footer if necessary */ DECODE_LEN_TREE_NOEOFCHECK(match_length); }
/* get match position slot */ m = c >> NL_SHIFT;
/* read any extra bits for the match position */ if (m > 2) { if (m > 3) /* dec_extra_bits[m] != 0 */ { GET_BITS17_NOEOFCHECK(dec_extra_bits[ m ], match_pos); match_pos += MP_POS_minus2[m]; } else { match_pos = MP_POS_minus2[3]; }
/*
* Add match base to "extra bits". Our match base * table has 2 subtracted from all the elements. * * This is because encoded positions 0,1,2 denote * repeated offsets. Encoded position 3 denotes * a match 1 character away, 4 encodes 2 away, etc. * Hence the subtraction of 2, which has been * incorporated into the table. */
/* update LRU repeated offset list */ context->dec_last_matchpos_offset[2] = context->dec_last_matchpos_offset[1]; context->dec_last_matchpos_offset[1] = context->dec_last_matchpos_offset[0]; context->dec_last_matchpos_offset[0] = match_pos; } else { /* positions 0, 1, 2 denote repeated offsets */ match_pos = context->dec_last_matchpos_offset[m];
if (m) { context->dec_last_matchpos_offset[m] = context->dec_last_matchpos_offset[0]; context->dec_last_matchpos_offset[0] = match_pos; } }
/* match lengths range from 2...257 */ match_length += MIN_MATCH;
#ifdef EXTRALONGMATCHES
if ( match_length == MAX_MATCH ) {
//
// See detailed explanation in decalign.c
//
ULONG ExtraMatchLength, ExtraMatchLengthResidue;
GET_BITS_NOEOFCHECK( 9, ExtraMatchLength );
if ( ExtraMatchLength & ( 1 << 8 )) { if ( ExtraMatchLength & ( 1 << 7 )) { if ( ExtraMatchLength & ( 1 << 6 )) { ExtraMatchLength = ( ExtraMatchLength & (( 1 << 6 ) - 1 )) << 9; GET_BITS_NOEOFCHECK( 9, ExtraMatchLengthResidue ); ExtraMatchLength |= ExtraMatchLengthResidue; } else { ExtraMatchLength = ( ExtraMatchLength & (( 1 << 6 ) - 1 )) << 6; GET_BITS_NOEOFCHECK( 6, ExtraMatchLengthResidue ); ExtraMatchLength |= ExtraMatchLengthResidue; ExtraMatchLength += ( 1 << 8 ) + ( 1 << 10 ); } } else { ExtraMatchLength = ( ExtraMatchLength & (( 1 << 7 ) - 1 )) << 3; GET_BITS_NOEOFCHECK( 3, ExtraMatchLengthResidue ); ExtraMatchLength |= ExtraMatchLengthResidue; ExtraMatchLength += ( 1 << 8 ); } }
match_length += ExtraMatchLength; }
#endif
match_ptr = (BufPos - match_pos) & context->dec_window_mask;
#ifdef TRACING
TracingMatch(BufPos, BufPos - match_pos, context->dec_window_size, match_length, m);#endif
/* copy match data */
do { context->dec_mem_window[BufPos++] = context->dec_mem_window[match_ptr++]; } while (--match_length > 0); } }
context->dec_bitcount = dec_bitcount; context->dec_bitbuf = dec_bitbuf; context->dec_input_curpos = dec_input_curpos;
/* should be zero */ decode_residue = BufPos - bufpos_end;
BufPos &= context->dec_window_mask; context->dec_bufpos = BufPos;
return decode_residue;}#endif /* ASM_DECODE_VERBATIM_BLOCK */
int decode_verbatim_block(t_decoder_context *context, long BufPos, int amount_to_decode){ /*
* Special case code when BufPos is near the beginning of the window; * we must properly update our MAX_MATCH wrapper bytes. */ if (BufPos < MAX_MATCH) { long new_bufpos; long amount_to_slowly_decode;
amount_to_slowly_decode = min(MAX_MATCH-BufPos, amount_to_decode);
/*
* It's ok to end up decoding more than we wanted if we * restricted it to decoding only MAX_MATCH; there's * no guarantee a match doesn't straddle MAX_MATCH */ new_bufpos = special_decode_verbatim_block( context, BufPos, amount_to_slowly_decode );
amount_to_decode -= (new_bufpos-BufPos);
context->dec_bufpos = BufPos = new_bufpos;
/*
* Note: if amount_to_decode < 0 then we're in trouble */ if (amount_to_decode <= 0) return amount_to_decode; }
return fast_decode_verbatim_block(context, BufPos, amount_to_decode);}
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