diff options
Diffstat (limited to 'src/liblzma/lzma/lzma_decoder.c')
| -rw-r--r-- | src/liblzma/lzma/lzma_decoder.c | 760 |
1 files changed, 445 insertions, 315 deletions
diff --git a/src/liblzma/lzma/lzma_decoder.c b/src/liblzma/lzma/lzma_decoder.c index 26c148a..0abed02 100644 --- a/src/liblzma/lzma/lzma_decoder.c +++ b/src/liblzma/lzma/lzma_decoder.c @@ -1,3 +1,5 @@ +// SPDX-License-Identifier: 0BSD + /////////////////////////////////////////////////////////////////////////////// // /// \file lzma_decoder.c @@ -5,9 +7,7 @@ /// // Authors: Igor Pavlov // Lasse Collin -// -// This file has been put into the public domain. -// You can do whatever you want with this file. +// Jia Tan // /////////////////////////////////////////////////////////////////////////////// @@ -22,25 +22,20 @@ # pragma GCC diagnostic ignored "-Wimplicit-fallthrough" #endif +// Minimum number of input bytes to safely decode one LZMA symbol. +// The worst case is that we decode 22 bits using probabilities and 26 +// direct bits. This may decode at maximum 20 bytes of input. +#define LZMA_IN_REQUIRED 20 -#ifdef HAVE_SMALL // Macros for (somewhat) size-optimized code. -#define seq_4(seq) seq - -#define seq_6(seq) seq - -#define seq_8(seq) seq - -#define seq_len(seq) \ - seq ## _CHOICE, \ - seq ## _CHOICE2, \ - seq ## _BITTREE - +// This is used to decode the match length (how many bytes must be repeated +// from the dictionary). This version is used in the Resumable mode and +// does not unroll any loops. #define len_decode(target, ld, pos_state, seq) \ do { \ case seq ## _CHOICE: \ - rc_if_0(ld.choice, seq ## _CHOICE) { \ + rc_if_0_safe(ld.choice, seq ## _CHOICE) { \ rc_update_0(ld.choice); \ probs = ld.low[pos_state];\ limit = LEN_LOW_SYMBOLS; \ @@ -48,7 +43,7 @@ case seq ## _CHOICE: \ } else { \ rc_update_1(ld.choice); \ case seq ## _CHOICE2: \ - rc_if_0(ld.choice2, seq ## _CHOICE2) { \ + rc_if_0_safe(ld.choice2, seq ## _CHOICE2) { \ rc_update_0(ld.choice2); \ probs = ld.mid[pos_state]; \ limit = LEN_MID_SYMBOLS; \ @@ -64,98 +59,39 @@ case seq ## _CHOICE2: \ symbol = 1; \ case seq ## _BITTREE: \ do { \ - rc_bit(probs[symbol], , , seq ## _BITTREE); \ + rc_bit_safe(probs[symbol], , , seq ## _BITTREE); \ } while (symbol < limit); \ target += symbol - limit; \ } while (0) -#else // HAVE_SMALL - -// Unrolled versions -#define seq_4(seq) \ - seq ## 0, \ - seq ## 1, \ - seq ## 2, \ - seq ## 3 - -#define seq_6(seq) \ - seq ## 0, \ - seq ## 1, \ - seq ## 2, \ - seq ## 3, \ - seq ## 4, \ - seq ## 5 - -#define seq_8(seq) \ - seq ## 0, \ - seq ## 1, \ - seq ## 2, \ - seq ## 3, \ - seq ## 4, \ - seq ## 5, \ - seq ## 6, \ - seq ## 7 - -#define seq_len(seq) \ - seq ## _CHOICE, \ - seq ## _LOW0, \ - seq ## _LOW1, \ - seq ## _LOW2, \ - seq ## _CHOICE2, \ - seq ## _MID0, \ - seq ## _MID1, \ - seq ## _MID2, \ - seq ## _HIGH0, \ - seq ## _HIGH1, \ - seq ## _HIGH2, \ - seq ## _HIGH3, \ - seq ## _HIGH4, \ - seq ## _HIGH5, \ - seq ## _HIGH6, \ - seq ## _HIGH7 -#define len_decode(target, ld, pos_state, seq) \ +// This is the faster version of the match length decoder that does not +// worry about being resumable. It unrolls the bittree decoding loop. +#define len_decode_fast(target, ld, pos_state) \ do { \ symbol = 1; \ -case seq ## _CHOICE: \ - rc_if_0(ld.choice, seq ## _CHOICE) { \ + rc_if_0(ld.choice) { \ rc_update_0(ld.choice); \ - rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW0); \ - rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW1); \ - rc_bit_case(ld.low[pos_state][symbol], , , seq ## _LOW2); \ - target = symbol - LEN_LOW_SYMBOLS + MATCH_LEN_MIN; \ + rc_bittree3(ld.low[pos_state], \ + -LEN_LOW_SYMBOLS + MATCH_LEN_MIN); \ + target = symbol; \ } else { \ rc_update_1(ld.choice); \ -case seq ## _CHOICE2: \ - rc_if_0(ld.choice2, seq ## _CHOICE2) { \ + rc_if_0(ld.choice2) { \ rc_update_0(ld.choice2); \ - rc_bit_case(ld.mid[pos_state][symbol], , , \ - seq ## _MID0); \ - rc_bit_case(ld.mid[pos_state][symbol], , , \ - seq ## _MID1); \ - rc_bit_case(ld.mid[pos_state][symbol], , , \ - seq ## _MID2); \ - target = symbol - LEN_MID_SYMBOLS \ - + MATCH_LEN_MIN + LEN_LOW_SYMBOLS; \ + rc_bittree3(ld.mid[pos_state], -LEN_MID_SYMBOLS \ + + MATCH_LEN_MIN + LEN_LOW_SYMBOLS); \ + target = symbol; \ } else { \ rc_update_1(ld.choice2); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH0); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH1); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH2); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH3); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH4); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH5); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH6); \ - rc_bit_case(ld.high[symbol], , , seq ## _HIGH7); \ - target = symbol - LEN_HIGH_SYMBOLS \ + rc_bittree8(ld.high, -LEN_HIGH_SYMBOLS \ + MATCH_LEN_MIN \ - + LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS; \ + + LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS); \ + target = symbol; \ } \ } \ } while (0) -#endif // HAVE_SMALL - /// Length decoder probabilities; see comments in lzma_common.h. typedef struct { @@ -173,7 +109,7 @@ typedef struct { /////////////////// /// Literals; see comments in lzma_common.h. - probability literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE]; + probability literal[LITERAL_CODERS_MAX * LITERAL_CODER_SIZE]; /// If 1, it's a match. Otherwise it's a single 8-bit literal. probability is_match[STATES][POS_STATES_MAX]; @@ -232,7 +168,7 @@ typedef struct { uint32_t pos_mask; // (1U << pb) - 1 uint32_t literal_context_bits; - uint32_t literal_pos_mask; + uint32_t literal_mask; /// Uncompressed size as bytes, or LZMA_VLI_UNKNOWN if end of /// payload marker is expected. @@ -251,22 +187,26 @@ typedef struct { enum { SEQ_NORMALIZE, SEQ_IS_MATCH, - seq_8(SEQ_LITERAL), - seq_8(SEQ_LITERAL_MATCHED), + SEQ_LITERAL, + SEQ_LITERAL_MATCHED, SEQ_LITERAL_WRITE, SEQ_IS_REP, - seq_len(SEQ_MATCH_LEN), - seq_6(SEQ_DIST_SLOT), + SEQ_MATCH_LEN_CHOICE, + SEQ_MATCH_LEN_CHOICE2, + SEQ_MATCH_LEN_BITTREE, + SEQ_DIST_SLOT, SEQ_DIST_MODEL, SEQ_DIRECT, - seq_4(SEQ_ALIGN), + SEQ_ALIGN, SEQ_EOPM, SEQ_IS_REP0, SEQ_SHORTREP, SEQ_IS_REP0_LONG, SEQ_IS_REP1, SEQ_IS_REP2, - seq_len(SEQ_REP_LEN), + SEQ_REP_LEN_CHOICE, + SEQ_REP_LEN_CHOICE2, + SEQ_REP_LEN_BITTREE, SEQ_COPY, } sequence; @@ -321,7 +261,7 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, const size_t dict_start = dict.pos; // Range decoder - rc_to_local(coder->rc, *in_pos); + rc_to_local(coder->rc, *in_pos, LZMA_IN_REQUIRED); // State uint32_t state = coder->state; @@ -340,7 +280,7 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, uint32_t offset = coder->offset; uint32_t len = coder->len; - const uint32_t literal_pos_mask = coder->literal_pos_mask; + const uint32_t literal_mask = coder->literal_mask; const uint32_t literal_context_bits = coder->literal_context_bits; // Temporary variables @@ -367,8 +307,24 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, might_finish_without_eopm = true; } - // The main decoder loop. The "switch" is used to restart the decoder at - // correct location. Once restarted, the "switch" is no longer used. + // The main decoder loop. The "switch" is used to resume the decoder at + // correct location. Once resumed, the "switch" is no longer used. + // The decoder loops is split into two modes: + // + // 1 - Non-resumable mode (fast). This is used when it is guaranteed + // there is enough input to decode the next symbol. If the output + // limit is reached, then the decoder loop will save the place + // for the resumable mode to continue. This mode is not used if + // HAVE_SMALL is defined. This is faster than Resumable mode + // because it reduces the number of branches needed and allows + // for more compiler optimizations. + // + // 2 - Resumable mode (slow). This is used when a previous decoder + // loop did not have enough space in the input or output buffers + // to complete. It uses sequence enum values to set remind + // coder->sequence where to resume in the decoder loop. This + // is the only mode used when HAVE_SMALL is defined. + switch (coder->sequence) while (true) { // Calculate new pos_state. This is skipped on the first loop @@ -376,13 +332,339 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, // variables. pos_state = dict.pos & pos_mask; +#ifndef HAVE_SMALL + + /////////////////////////////// + // Non-resumable Mode (fast) // + /////////////////////////////// + + // Go to Resumable mode (1) if there is not enough input to + // safely decode any possible LZMA symbol or (2) if the + // dictionary is full, which may need special checks that + // are only done in the Resumable mode. + if (unlikely(!rc_is_fast_allowed() + || dict.pos == dict.limit)) + goto slow; + + // Decode the first bit from the next LZMA symbol. + // If the bit is a 0, then we handle it as a literal. + // If the bit is a 1, then it is a match of previously + // decoded data. + rc_if_0(coder->is_match[state][pos_state]) { + ///////////////////// + // Decode literal. // + ///////////////////// + + // Update the RC that we have decoded a 0. + rc_update_0(coder->is_match[state][pos_state]); + + // Get the correct probability array from lp and + // lc params. + probs = literal_subcoder(coder->literal, + literal_context_bits, literal_mask, + dict.pos, dict_get0(&dict)); + + if (is_literal_state(state)) { + update_literal_normal(state); + + // Decode literal without match byte. + rc_bittree8(probs, 0); + } else { + update_literal_matched(state); + + // Decode literal with match byte. + rc_matched_literal(probs, + dict_get(&dict, rep0)); + } + + // Write decoded literal to dictionary + dict_put(&dict, symbol); + continue; + } + + /////////////////// + // Decode match. // + /////////////////// + + // Instead of a new byte we are going to decode a + // distance-length pair. The distance represents how far + // back in the dictionary to begin copying. The length + // represents how many bytes to copy. + + rc_update_1(coder->is_match[state][pos_state]); + + rc_if_0(coder->is_rep[state]) { + /////////////////// + // Simple match. // + /////////////////// + + // Not a repeated match. In this case, + // the length (how many bytes to copy) must be + // decoded first. Then, the distance (where to + // start copying) is decoded. + // + // This is also how we know when we are done + // decoding. If the distance decodes to UINT32_MAX, + // then we know to stop decoding (end of payload + // marker). + + rc_update_0(coder->is_rep[state]); + update_match(state); + + // The latest three match distances are kept in + // memory in case there are repeated matches. + rep3 = rep2; + rep2 = rep1; + rep1 = rep0; + + // Decode the length of the match. + len_decode_fast(len, coder->match_len_decoder, + pos_state); + + // Next, decode the distance into rep0. + + // The next 6 bits determine how to decode the + // rest of the distance. + probs = coder->dist_slot[get_dist_state(len)]; + + rc_bittree6(probs, -DIST_SLOTS); + assert(symbol <= 63); + + if (symbol < DIST_MODEL_START) { + // If the decoded symbol is < DIST_MODEL_START + // then we use its value directly as the + // match distance. No other bits are needed. + // The only possible distance values + // are [0, 3]. + rep0 = symbol; + } else { + // Use the first two bits of symbol as the + // highest bits of the match distance. + + // "limit" represents the number of low bits + // to decode. + limit = (symbol >> 1) - 1; + assert(limit >= 1 && limit <= 30); + rep0 = 2 + (symbol & 1); + + if (symbol < DIST_MODEL_END) { + // When symbol is > DIST_MODEL_START, + // but symbol < DIST_MODEL_END, then + // it can decode distances between + // [4, 127]. + assert(limit <= 5); + rep0 <<= limit; + assert(rep0 <= 96); + + // -1 is fine, because we start + // decoding at probs[1], not probs[0]. + // NOTE: This violates the C standard, + // since we are doing pointer + // arithmetic past the beginning of + // the array. + assert((int32_t)(rep0 - symbol - 1) + >= -1); + assert((int32_t)(rep0 - symbol - 1) + <= 82); + probs = coder->pos_special + rep0 + - symbol - 1; + symbol = 1; + offset = 1; + + // Variable number (1-5) of bits + // from a reverse bittree. This + // isn't worth manual unrolling. + // + // NOTE: Making one or many of the + // variables (probs, symbol, offset, + // or limit) local here (instead of + // using those declared outside the + // main loop) can affect code size + // and performance which isn't a + // surprise but it's not so clear + // what is the best. + do { + rc_bit_add_if_1(probs, + rep0, offset); + offset <<= 1; + } while (--limit > 0); + } else { + // The distance is >= 128. Decode the + // lower bits without probabilities + // except the lowest four bits. + assert(symbol >= 14); + assert(limit >= 6); + + limit -= ALIGN_BITS; + assert(limit >= 2); + + rc_direct(rep0, limit); + + // Decode the lowest four bits using + // probabilities. + rep0 <<= ALIGN_BITS; + rc_bittree_rev4(coder->pos_align); + rep0 += symbol; + + // If the end of payload marker (EOPM) + // is detected, jump to the safe code. + // The EOPM handling isn't speed + // critical at all. + // + // A final normalization is needed + // after the EOPM (there can be a + // dummy byte to read in some cases). + // If the normalization was done here + // in the fast code, it would need to + // be taken into account in the value + // of LZMA_IN_REQUIRED. Using the + // safe code allows keeping + // LZMA_IN_REQUIRED as 20 instead of + // 21. + if (rep0 == UINT32_MAX) + goto eopm; + } + } + + // Validate the distance we just decoded. + if (unlikely(!dict_is_distance_valid(&dict, rep0))) { + ret = LZMA_DATA_ERROR; + goto out; + } + + } else { + rc_update_1(coder->is_rep[state]); + + ///////////////////// + // Repeated match. // + ///////////////////// + + // The match distance is a value that we have decoded + // recently. The latest four match distances are + // available as rep0, rep1, rep2 and rep3. We will + // now decode which of them is the new distance. + // + // There cannot be a match if we haven't produced + // any output, so check that first. + if (unlikely(!dict_is_distance_valid(&dict, 0))) { + ret = LZMA_DATA_ERROR; + goto out; + } + + rc_if_0(coder->is_rep0[state]) { + rc_update_0(coder->is_rep0[state]); + // The distance is rep0. + + // Decode the next bit to determine if 1 byte + // should be copied from rep0 distance or + // if the number of bytes needs to be decoded. + + // If the next bit is 0, then it is a + // "Short Rep Match" and only 1 bit is copied. + // Otherwise, the length of the match is + // decoded after the "else" statement. + rc_if_0(coder->is_rep0_long[state][pos_state]) { + rc_update_0(coder->is_rep0_long[ + state][pos_state]); + + update_short_rep(state); + dict_put(&dict, dict_get(&dict, rep0)); + continue; + } + + // Repeating more than one byte at + // distance of rep0. + rc_update_1(coder->is_rep0_long[ + state][pos_state]); + + } else { + rc_update_1(coder->is_rep0[state]); + + // The distance is rep1, rep2 or rep3. Once + // we find out which one of these three, it + // is stored to rep0 and rep1, rep2 and rep3 + // are updated accordingly. There is no + // "Short Rep Match" option, so the length + // of the match must always be decoded next. + rc_if_0(coder->is_rep1[state]) { + // The distance is rep1. + rc_update_0(coder->is_rep1[state]); + + const uint32_t distance = rep1; + rep1 = rep0; + rep0 = distance; + + } else { + rc_update_1(coder->is_rep1[state]); + + rc_if_0(coder->is_rep2[state]) { + // The distance is rep2. + rc_update_0(coder->is_rep2[ + state]); + + const uint32_t distance = rep2; + rep2 = rep1; + rep1 = rep0; + rep0 = distance; + + } else { + // The distance is rep3. + rc_update_1(coder->is_rep2[ + state]); + + const uint32_t distance = rep3; + rep3 = rep2; + rep2 = rep1; + rep1 = rep0; + rep0 = distance; + } + } + } + + update_long_rep(state); + + // Decode the length of the repeated match. + len_decode_fast(len, coder->rep_len_decoder, + pos_state); + } + + ///////////////////////////////// + // Repeat from history buffer. // + ///////////////////////////////// + + // The length is always between these limits. There is no way + // to trigger the algorithm to set len outside this range. + assert(len >= MATCH_LEN_MIN); + assert(len <= MATCH_LEN_MAX); + + // Repeat len bytes from distance of rep0. + if (unlikely(dict_repeat(&dict, rep0, &len))) { + coder->sequence = SEQ_COPY; + goto out; + } + + continue; + +slow: +#endif + /////////////////////////// + // Resumable Mode (slow) // + /////////////////////////// + + // This is very similar to Non-resumable Mode, so most of the + // comments are not repeated. The main differences are: + // - case labels are used to resume at the correct location. + // - Loops are not unrolled. + // - Range coder macros take an extra sequence argument + // so they can save to coder->sequence the location to + // resume in case there is not enough input. case SEQ_NORMALIZE: case SEQ_IS_MATCH: if (unlikely(might_finish_without_eopm && dict.pos == dict.limit)) { // In rare cases there is a useless byte that needs // to be read anyway. - rc_normalize(SEQ_NORMALIZE); + rc_normalize_safe(SEQ_NORMALIZE); // If the range decoder state is such that we can // be at the end of the LZMA stream, then the @@ -405,49 +687,37 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, eopm_is_valid = true; } - rc_if_0(coder->is_match[state][pos_state], SEQ_IS_MATCH) { - rc_update_0(coder->is_match[state][pos_state]); + rc_if_0_safe(coder->is_match[state][pos_state], SEQ_IS_MATCH) { + ///////////////////// + // Decode literal. // + ///////////////////// - // It's a literal i.e. a single 8-bit byte. + rc_update_0(coder->is_match[state][pos_state]); probs = literal_subcoder(coder->literal, - literal_context_bits, literal_pos_mask, - dict.pos, dict_get(&dict, 0)); + literal_context_bits, literal_mask, + dict.pos, dict_get0(&dict)); symbol = 1; if (is_literal_state(state)) { + update_literal_normal(state); + // Decode literal without match byte. -#ifdef HAVE_SMALL + // The "slow" version does not unroll + // the loop. case SEQ_LITERAL: do { - rc_bit(probs[symbol], , , SEQ_LITERAL); + rc_bit_safe(probs[symbol], , , + SEQ_LITERAL); } while (symbol < (1 << 8)); -#else - rc_bit_case(probs[symbol], , , SEQ_LITERAL0); - rc_bit_case(probs[symbol], , , SEQ_LITERAL1); - rc_bit_case(probs[symbol], , , SEQ_LITERAL2); - rc_bit_case(probs[symbol], , , SEQ_LITERAL3); - rc_bit_case(probs[symbol], , , SEQ_LITERAL4); - rc_bit_case(probs[symbol], , , SEQ_LITERAL5); - rc_bit_case(probs[symbol], , , SEQ_LITERAL6); - rc_bit_case(probs[symbol], , , SEQ_LITERAL7); -#endif } else { + update_literal_matched(state); + // Decode literal with match byte. - // - // We store the byte we compare against - // ("match byte") to "len" to minimize the - // number of variables we need to store - // between decoder calls. len = (uint32_t)(dict_get(&dict, rep0)) << 1; - // The usage of "offset" allows omitting some - // branches, which should give tiny speed - // improvement on some CPUs. "offset" gets - // set to zero if match_bit didn't match. offset = 0x100; -#ifdef HAVE_SMALL case SEQ_LITERAL_MATCHED: do { const uint32_t match_bit @@ -456,7 +726,7 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, = offset + match_bit + symbol; - rc_bit(probs[subcoder_index], + rc_bit_safe(probs[subcoder_index], offset &= ~match_bit, offset &= match_bit, SEQ_LITERAL_MATCHED); @@ -469,61 +739,10 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, len <<= 1; } while (symbol < (1 << 8)); -#else - // Unroll the loop. - uint32_t match_bit; - uint32_t subcoder_index; - -# define d(seq) \ - case seq: \ - match_bit = len & offset; \ - subcoder_index = offset + match_bit + symbol; \ - rc_bit(probs[subcoder_index], \ - offset &= ~match_bit, \ - offset &= match_bit, \ - seq) - - d(SEQ_LITERAL_MATCHED0); - len <<= 1; - d(SEQ_LITERAL_MATCHED1); - len <<= 1; - d(SEQ_LITERAL_MATCHED2); - len <<= 1; - d(SEQ_LITERAL_MATCHED3); - len <<= 1; - d(SEQ_LITERAL_MATCHED4); - len <<= 1; - d(SEQ_LITERAL_MATCHED5); - len <<= 1; - d(SEQ_LITERAL_MATCHED6); - len <<= 1; - d(SEQ_LITERAL_MATCHED7); -# undef d -#endif } - //update_literal(state); - // Use a lookup table to update to literal state, - // since compared to other state updates, this would - // need two branches. - static const lzma_lzma_state next_state[] = { - STATE_LIT_LIT, - STATE_LIT_LIT, - STATE_LIT_LIT, - STATE_LIT_LIT, - STATE_MATCH_LIT_LIT, - STATE_REP_LIT_LIT, - STATE_SHORTREP_LIT_LIT, - STATE_MATCH_LIT, - STATE_REP_LIT, - STATE_SHORTREP_LIT, - STATE_MATCH_LIT, - STATE_REP_LIT - }; - state = next_state[state]; - case SEQ_LITERAL_WRITE: - if (unlikely(dict_put(&dict, symbol))) { + if (dict_put_safe(&dict, symbol)) { coder->sequence = SEQ_LITERAL_WRITE; goto out; } @@ -531,64 +750,47 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, continue; } - // Instead of a new byte we are going to get a byte range - // (distance and length) which will be repeated from our - // output history. + /////////////////// + // Decode match. // + /////////////////// rc_update_1(coder->is_match[state][pos_state]); case SEQ_IS_REP: - rc_if_0(coder->is_rep[state], SEQ_IS_REP) { - // Not a repeated match + rc_if_0_safe(coder->is_rep[state], SEQ_IS_REP) { + /////////////////// + // Simple match. // + /////////////////// + rc_update_0(coder->is_rep[state]); update_match(state); - // The latest three match distances are kept in - // memory in case there are repeated matches. rep3 = rep2; rep2 = rep1; rep1 = rep0; - // Decode the length of the match. len_decode(len, coder->match_len_decoder, pos_state, SEQ_MATCH_LEN); - // Prepare to decode the highest two bits of the - // match distance. probs = coder->dist_slot[get_dist_state(len)]; symbol = 1; -#ifdef HAVE_SMALL case SEQ_DIST_SLOT: do { - rc_bit(probs[symbol], , , SEQ_DIST_SLOT); + rc_bit_safe(probs[symbol], , , SEQ_DIST_SLOT); } while (symbol < DIST_SLOTS); -#else - rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT0); - rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT1); - rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT2); - rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT3); - rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT4); - rc_bit_case(probs[symbol], , , SEQ_DIST_SLOT5); -#endif - // Get rid of the highest bit that was needed for - // indexing of the probability array. + symbol -= DIST_SLOTS; assert(symbol <= 63); if (symbol < DIST_MODEL_START) { - // Match distances [0, 3] have only two bits. rep0 = symbol; } else { - // Decode the lowest [1, 29] bits of - // the match distance. limit = (symbol >> 1) - 1; assert(limit >= 1 && limit <= 30); rep0 = 2 + (symbol & 1); if (symbol < DIST_MODEL_END) { - // Prepare to decode the low bits for - // a distance of [4, 127]. assert(limit <= 5); rep0 <<= limit; assert(rep0 <= 96); @@ -607,95 +809,36 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, symbol = 1; offset = 0; case SEQ_DIST_MODEL: -#ifdef HAVE_SMALL do { - rc_bit(probs[symbol], , + rc_bit_safe(probs[symbol], , rep0 += 1U << offset, SEQ_DIST_MODEL); } while (++offset < limit); -#else - switch (limit) { - case 5: - assert(offset == 0); - rc_bit(probs[symbol], , - rep0 += 1U, - SEQ_DIST_MODEL); - ++offset; - --limit; - case 4: - rc_bit(probs[symbol], , - rep0 += 1U << offset, - SEQ_DIST_MODEL); - ++offset; - --limit; - case 3: - rc_bit(probs[symbol], , - rep0 += 1U << offset, - SEQ_DIST_MODEL); - ++offset; - --limit; - case 2: - rc_bit(probs[symbol], , - rep0 += 1U << offset, - SEQ_DIST_MODEL); - ++offset; - --limit; - case 1: - // We need "symbol" only for - // indexing the probability - // array, thus we can use - // rc_bit_last() here to omit - // the unneeded updating of - // "symbol". - rc_bit_last(probs[symbol], , - rep0 += 1U << offset, - SEQ_DIST_MODEL); - } -#endif } else { - // The distance is >= 128. Decode the - // lower bits without probabilities - // except the lowest four bits. assert(symbol >= 14); assert(limit >= 6); limit -= ALIGN_BITS; assert(limit >= 2); case SEQ_DIRECT: - // Not worth manual unrolling - do { - rc_direct(rep0, SEQ_DIRECT); - } while (--limit > 0); + rc_direct_safe(rep0, limit, + SEQ_DIRECT); - // Decode the lowest four bits using - // probabilities. rep0 <<= ALIGN_BITS; - symbol = 1; -#ifdef HAVE_SMALL - offset = 0; + symbol = 0; + offset = 1; case SEQ_ALIGN: do { - rc_bit(coder->pos_align[ - symbol], , - rep0 += 1U << offset, + rc_bit_last_safe( + coder->pos_align[ + offset + + symbol], + , + symbol += offset, SEQ_ALIGN); - } while (++offset < ALIGN_BITS); -#else - case SEQ_ALIGN0: - rc_bit(coder->pos_align[symbol], , - rep0 += 1, SEQ_ALIGN0); - case SEQ_ALIGN1: - rc_bit(coder->pos_align[symbol], , - rep0 += 2, SEQ_ALIGN1); - case SEQ_ALIGN2: - rc_bit(coder->pos_align[symbol], , - rep0 += 4, SEQ_ALIGN2); - case SEQ_ALIGN3: - // Like in SEQ_DIST_MODEL, we don't - // need "symbol" for anything else - // than indexing the probability array. - rc_bit_last(coder->pos_align[symbol], , - rep0 += 8, SEQ_ALIGN3); -#endif + offset <<= 1; + } while (offset < ALIGN_SIZE); + + rep0 += symbol; if (rep0 == UINT32_MAX) { // End of payload marker was @@ -710,6 +853,9 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, // that EOPM might be used // (it's not allowed in // LZMA2). +#ifndef HAVE_SMALL +eopm: +#endif if (!eopm_is_valid) { ret = LZMA_DATA_ERROR; goto out; @@ -718,7 +864,7 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, case SEQ_EOPM: // LZMA1 stream with // end-of-payload marker. - rc_normalize(SEQ_EOPM); + rc_normalize_safe(SEQ_EOPM); ret = rc_is_finished(rc) ? LZMA_STREAM_END : LZMA_DATA_ERROR; @@ -727,36 +873,30 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, } } - // Validate the distance we just decoded. if (unlikely(!dict_is_distance_valid(&dict, rep0))) { ret = LZMA_DATA_ERROR; goto out; } } else { + ///////////////////// + // Repeated match. // + ///////////////////// + rc_update_1(coder->is_rep[state]); - // Repeated match - // - // The match distance is a value that we have had - // earlier. The latest four match distances are - // available as rep0, rep1, rep2 and rep3. We will - // now decode which of them is the new distance. - // - // There cannot be a match if we haven't produced - // any output, so check that first. if (unlikely(!dict_is_distance_valid(&dict, 0))) { ret = LZMA_DATA_ERROR; goto out; } case SEQ_IS_REP0: - rc_if_0(coder->is_rep0[state], SEQ_IS_REP0) { + rc_if_0_safe(coder->is_rep0[state], SEQ_IS_REP0) { rc_update_0(coder->is_rep0[state]); - // The distance is rep0. case SEQ_IS_REP0_LONG: - rc_if_0(coder->is_rep0_long[state][pos_state], + rc_if_0_safe(coder->is_rep0_long + [state][pos_state], SEQ_IS_REP0_LONG) { rc_update_0(coder->is_rep0_long[ state][pos_state]); @@ -764,8 +904,9 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, update_short_rep(state); case SEQ_SHORTREP: - if (unlikely(dict_put(&dict, dict_get( - &dict, rep0)))) { + if (dict_put_safe(&dict, + dict_get(&dict, + rep0))) { coder->sequence = SEQ_SHORTREP; goto out; } @@ -773,8 +914,6 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, continue; } - // Repeating more than one byte at - // distance of rep0. rc_update_1(coder->is_rep0_long[ state][pos_state]); @@ -782,11 +921,7 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, rc_update_1(coder->is_rep0[state]); case SEQ_IS_REP1: - // The distance is rep1, rep2 or rep3. Once - // we find out which one of these three, it - // is stored to rep0 and rep1, rep2 and rep3 - // are updated accordingly. - rc_if_0(coder->is_rep1[state], SEQ_IS_REP1) { + rc_if_0_safe(coder->is_rep1[state], SEQ_IS_REP1) { rc_update_0(coder->is_rep1[state]); const uint32_t distance = rep1; @@ -796,7 +931,7 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, } else { rc_update_1(coder->is_rep1[state]); case SEQ_IS_REP2: - rc_if_0(coder->is_rep2[state], + rc_if_0_safe(coder->is_rep2[state], SEQ_IS_REP2) { rc_update_0(coder->is_rep2[ state]); @@ -821,7 +956,6 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, update_long_rep(state); - // Decode the length of the repeated match. len_decode(len, coder->rep_len_decoder, pos_state, SEQ_REP_LEN); } @@ -830,13 +964,10 @@ lzma_decode(void *coder_ptr, lzma_dict *restrict dictptr, // Repeat from history buffer. // ///////////////////////////////// - // The length is always between these limits. There is no way - // to trigger the algorithm to set len outside this range. assert(len >= MATCH_LEN_MIN); assert(len <= MATCH_LEN_MAX); case SEQ_COPY: - // Repeat len bytes from distance of rep0. if (unlikely(dict_repeat(&dict, rep0, &len))) { coder->sequence = SEQ_COPY; goto out; @@ -890,7 +1021,6 @@ out: } - static void lzma_decoder_uncompressed(void *coder_ptr, lzma_vli uncompressed_size, bool allow_eopm) @@ -917,7 +1047,7 @@ lzma_decoder_reset(void *coder_ptr, const void *opt) literal_init(coder->literal, options->lc, options->lp); coder->literal_context_bits = options->lc; - coder->literal_pos_mask = (1U << options->lp) - 1; + coder->literal_mask = literal_mask_calc(options->lc, options->lp); // State coder->state = STATE_LIT_LIT; |