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745 lines
17 KiB
745 lines
17 KiB
///////////////////////////////////////////////////////////////////////////////
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//
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/// \file lz_encoder_mf.c
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/// \brief Match finders
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///
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// Authors: Igor Pavlov
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// Lasse Collin
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "lz_encoder.h"
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#include "lz_encoder_hash.h"
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#include "memcmplen.h"
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/// \brief Find matches starting from the current byte
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///
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/// \return The length of the longest match found
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extern uint32_t
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lzma_mf_find(lzma_mf *mf, uint32_t *count_ptr, lzma_match *matches)
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{
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// Call the match finder. It returns the number of length-distance
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// pairs found.
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// FIXME: Minimum count is zero, what _exactly_ is the maximum?
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const uint32_t count = mf->find(mf, matches);
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// Length of the longest match; assume that no matches were found
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// and thus the maximum length is zero.
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uint32_t len_best = 0;
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if (count > 0) {
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#ifndef NDEBUG
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// Validate the matches.
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for (uint32_t i = 0; i < count; ++i) {
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assert(matches[i].len <= mf->nice_len);
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assert(matches[i].dist < mf->read_pos);
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assert(memcmp(mf_ptr(mf) - 1,
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mf_ptr(mf) - matches[i].dist - 2,
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matches[i].len) == 0);
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}
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#endif
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// The last used element in the array contains
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// the longest match.
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len_best = matches[count - 1].len;
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// If a match of maximum search length was found, try to
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// extend the match to maximum possible length.
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if (len_best == mf->nice_len) {
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// The limit for the match length is either the
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// maximum match length supported by the LZ-based
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// encoder or the number of bytes left in the
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// dictionary, whichever is smaller.
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uint32_t limit = mf_avail(mf) + 1;
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if (limit > mf->match_len_max)
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limit = mf->match_len_max;
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// Pointer to the byte we just ran through
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// the match finder.
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const uint8_t *p1 = mf_ptr(mf) - 1;
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// Pointer to the beginning of the match. We need -1
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// here because the match distances are zero based.
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const uint8_t *p2 = p1 - matches[count - 1].dist - 1;
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len_best = lzma_memcmplen(p1, p2, len_best, limit);
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}
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}
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*count_ptr = count;
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// Finally update the read position to indicate that match finder was
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// run for this dictionary offset.
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++mf->read_ahead;
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return len_best;
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}
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/// Hash value to indicate unused element in the hash. Since we start the
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/// positions from dict_size + 1, zero is always too far to qualify
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/// as usable match position.
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#define EMPTY_HASH_VALUE 0
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/// Normalization must be done when lzma_mf.offset + lzma_mf.read_pos
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/// reaches MUST_NORMALIZE_POS.
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#define MUST_NORMALIZE_POS UINT32_MAX
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/// \brief Normalizes hash values
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///
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/// The hash arrays store positions of match candidates. The positions are
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/// relative to an arbitrary offset that is not the same as the absolute
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/// offset in the input stream. The relative position of the current byte
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/// is lzma_mf.offset + lzma_mf.read_pos. The distances of the matches are
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/// the differences of the current read position and the position found from
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/// the hash.
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///
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/// To prevent integer overflows of the offsets stored in the hash arrays,
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/// we need to "normalize" the stored values now and then. During the
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/// normalization, we drop values that indicate distance greater than the
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/// dictionary size, thus making space for new values.
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static void
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normalize(lzma_mf *mf)
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{
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assert(mf->read_pos + mf->offset == MUST_NORMALIZE_POS);
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// In future we may not want to touch the lowest bits, because there
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// may be match finders that use larger resolution than one byte.
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const uint32_t subvalue
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= (MUST_NORMALIZE_POS - mf->cyclic_size);
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// & ~((UINT32_C(1) << 10) - 1);
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for (uint32_t i = 0; i < mf->hash_count; ++i) {
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// If the distance is greater than the dictionary size,
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// we can simply mark the hash element as empty.
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if (mf->hash[i] <= subvalue)
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mf->hash[i] = EMPTY_HASH_VALUE;
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else
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mf->hash[i] -= subvalue;
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}
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for (uint32_t i = 0; i < mf->sons_count; ++i) {
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// Do the same for mf->son.
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//
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// NOTE: There may be uninitialized elements in mf->son.
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// Valgrind may complain that the "if" below depends on
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// an uninitialized value. In this case it is safe to ignore
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// the warning. See also the comments in lz_encoder_init()
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// in lz_encoder.c.
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if (mf->son[i] <= subvalue)
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mf->son[i] = EMPTY_HASH_VALUE;
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else
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mf->son[i] -= subvalue;
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}
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// Update offset to match the new locations.
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mf->offset -= subvalue;
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return;
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}
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/// Mark the current byte as processed from point of view of the match finder.
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static void
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move_pos(lzma_mf *mf)
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{
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if (++mf->cyclic_pos == mf->cyclic_size)
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mf->cyclic_pos = 0;
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++mf->read_pos;
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assert(mf->read_pos <= mf->write_pos);
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if (unlikely(mf->read_pos + mf->offset == UINT32_MAX))
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normalize(mf);
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}
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/// When flushing, we cannot run the match finder unless there is nice_len
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/// bytes available in the dictionary. Instead, we skip running the match
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/// finder (indicating that no match was found), and count how many bytes we
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/// have ignored this way.
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///
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/// When new data is given after the flushing was completed, the match finder
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/// is restarted by rewinding mf->read_pos backwards by mf->pending. Then
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/// the missed bytes are added to the hash using the match finder's skip
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/// function (with small amount of input, it may start using mf->pending
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/// again if flushing).
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///
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/// Due to this rewinding, we don't touch cyclic_pos or test for
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/// normalization. It will be done when the match finder's skip function
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/// catches up after a flush.
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static void
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move_pending(lzma_mf *mf)
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{
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++mf->read_pos;
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assert(mf->read_pos <= mf->write_pos);
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++mf->pending;
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}
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/// Calculate len_limit and determine if there is enough input to run
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/// the actual match finder code. Sets up "cur" and "pos". This macro
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/// is used by all find functions and binary tree skip functions. Hash
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/// chain skip function doesn't need len_limit so a simpler code is used
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/// in them.
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#define header(is_bt, len_min, ret_op) \
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uint32_t len_limit = mf_avail(mf); \
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if (mf->nice_len <= len_limit) { \
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len_limit = mf->nice_len; \
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} else if (len_limit < (len_min) \
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|| (is_bt && mf->action == LZMA_SYNC_FLUSH)) { \
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assert(mf->action != LZMA_RUN); \
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move_pending(mf); \
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ret_op; \
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} \
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const uint8_t *cur = mf_ptr(mf); \
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const uint32_t pos = mf->read_pos + mf->offset
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/// Header for find functions. "return 0" indicates that zero matches
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/// were found.
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#define header_find(is_bt, len_min) \
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header(is_bt, len_min, return 0); \
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uint32_t matches_count = 0
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/// Header for a loop in a skip function. "continue" tells to skip the rest
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/// of the code in the loop.
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#define header_skip(is_bt, len_min) \
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header(is_bt, len_min, continue)
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/// Calls hc_find_func() or bt_find_func() and calculates the total number
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/// of matches found. Updates the dictionary position and returns the number
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/// of matches found.
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#define call_find(func, len_best) \
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do { \
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matches_count = func(len_limit, pos, cur, cur_match, mf->depth, \
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mf->son, mf->cyclic_pos, mf->cyclic_size, \
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matches + matches_count, len_best) \
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- matches; \
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move_pos(mf); \
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return matches_count; \
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} while (0)
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////////////////
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// Hash Chain //
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////////////////
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#if defined(HAVE_MF_HC3) || defined(HAVE_MF_HC4)
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///
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///
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/// \param len_limit Don't look for matches longer than len_limit.
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/// \param pos lzma_mf.read_pos + lzma_mf.offset
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/// \param cur Pointer to current byte (mf_ptr(mf))
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/// \param cur_match Start position of the current match candidate
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/// \param depth Maximum length of the hash chain
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/// \param son lzma_mf.son (contains the hash chain)
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/// \param cyclic_pos
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/// \param cyclic_size
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/// \param matches Array to hold the matches.
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/// \param len_best The length of the longest match found so far.
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static lzma_match *
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hc_find_func(
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const uint32_t len_limit,
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const uint32_t pos,
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const uint8_t *const cur,
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uint32_t cur_match,
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uint32_t depth,
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uint32_t *const son,
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const uint32_t cyclic_pos,
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const uint32_t cyclic_size,
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lzma_match *matches,
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uint32_t len_best)
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{
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son[cyclic_pos] = cur_match;
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while (true) {
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const uint32_t delta = pos - cur_match;
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if (depth-- == 0 || delta >= cyclic_size)
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return matches;
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const uint8_t *const pb = cur - delta;
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cur_match = son[cyclic_pos - delta
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+ (delta > cyclic_pos ? cyclic_size : 0)];
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if (pb[len_best] == cur[len_best] && pb[0] == cur[0]) {
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uint32_t len = lzma_memcmplen(pb, cur, 1, len_limit);
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if (len_best < len) {
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len_best = len;
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matches->len = len;
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matches->dist = delta - 1;
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++matches;
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if (len == len_limit)
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return matches;
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}
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}
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}
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}
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#define hc_find(len_best) \
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call_find(hc_find_func, len_best)
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#define hc_skip() \
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do { \
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mf->son[mf->cyclic_pos] = cur_match; \
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move_pos(mf); \
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} while (0)
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#endif
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#ifdef HAVE_MF_HC3
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extern uint32_t
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lzma_mf_hc3_find(lzma_mf *mf, lzma_match *matches)
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{
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header_find(false, 3);
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hash_3_calc();
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const uint32_t delta2 = pos - mf->hash[hash_2_value];
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const uint32_t cur_match = mf->hash[FIX_3_HASH_SIZE + hash_value];
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mf->hash[hash_2_value] = pos;
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mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
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uint32_t len_best = 2;
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if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
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len_best = lzma_memcmplen(cur - delta2, cur,
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len_best, len_limit);
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matches[0].len = len_best;
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matches[0].dist = delta2 - 1;
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matches_count = 1;
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if (len_best == len_limit) {
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hc_skip();
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return 1; // matches_count
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}
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}
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hc_find(len_best);
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}
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extern void
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lzma_mf_hc3_skip(lzma_mf *mf, uint32_t amount)
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{
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do {
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if (mf_avail(mf) < 3) {
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move_pending(mf);
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continue;
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}
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const uint8_t *cur = mf_ptr(mf);
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const uint32_t pos = mf->read_pos + mf->offset;
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hash_3_calc();
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const uint32_t cur_match
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= mf->hash[FIX_3_HASH_SIZE + hash_value];
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mf->hash[hash_2_value] = pos;
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mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
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hc_skip();
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} while (--amount != 0);
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}
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#endif
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#ifdef HAVE_MF_HC4
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extern uint32_t
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lzma_mf_hc4_find(lzma_mf *mf, lzma_match *matches)
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{
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header_find(false, 4);
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hash_4_calc();
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uint32_t delta2 = pos - mf->hash[hash_2_value];
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const uint32_t delta3
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= pos - mf->hash[FIX_3_HASH_SIZE + hash_3_value];
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const uint32_t cur_match = mf->hash[FIX_4_HASH_SIZE + hash_value];
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mf->hash[hash_2_value ] = pos;
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mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
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mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
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uint32_t len_best = 1;
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if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
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len_best = 2;
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matches[0].len = 2;
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matches[0].dist = delta2 - 1;
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matches_count = 1;
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}
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if (delta2 != delta3 && delta3 < mf->cyclic_size
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&& *(cur - delta3) == *cur) {
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len_best = 3;
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matches[matches_count++].dist = delta3 - 1;
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delta2 = delta3;
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}
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if (matches_count != 0) {
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len_best = lzma_memcmplen(cur - delta2, cur,
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len_best, len_limit);
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matches[matches_count - 1].len = len_best;
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if (len_best == len_limit) {
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hc_skip();
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return matches_count;
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}
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}
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if (len_best < 3)
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len_best = 3;
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hc_find(len_best);
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}
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extern void
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lzma_mf_hc4_skip(lzma_mf *mf, uint32_t amount)
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{
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do {
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if (mf_avail(mf) < 4) {
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move_pending(mf);
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continue;
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}
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const uint8_t *cur = mf_ptr(mf);
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const uint32_t pos = mf->read_pos + mf->offset;
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hash_4_calc();
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const uint32_t cur_match
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= mf->hash[FIX_4_HASH_SIZE + hash_value];
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mf->hash[hash_2_value] = pos;
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mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
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mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
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hc_skip();
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} while (--amount != 0);
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}
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#endif
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/////////////////
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// Binary Tree //
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/////////////////
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#if defined(HAVE_MF_BT2) || defined(HAVE_MF_BT3) || defined(HAVE_MF_BT4)
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static lzma_match *
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bt_find_func(
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const uint32_t len_limit,
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const uint32_t pos,
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const uint8_t *const cur,
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uint32_t cur_match,
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uint32_t depth,
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uint32_t *const son,
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const uint32_t cyclic_pos,
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const uint32_t cyclic_size,
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lzma_match *matches,
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uint32_t len_best)
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{
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uint32_t *ptr0 = son + (cyclic_pos << 1) + 1;
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uint32_t *ptr1 = son + (cyclic_pos << 1);
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uint32_t len0 = 0;
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uint32_t len1 = 0;
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while (true) {
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const uint32_t delta = pos - cur_match;
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if (depth-- == 0 || delta >= cyclic_size) {
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*ptr0 = EMPTY_HASH_VALUE;
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*ptr1 = EMPTY_HASH_VALUE;
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return matches;
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}
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uint32_t *const pair = son + ((cyclic_pos - delta
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+ (delta > cyclic_pos ? cyclic_size : 0))
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<< 1);
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const uint8_t *const pb = cur - delta;
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uint32_t len = my_min(len0, len1);
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if (pb[len] == cur[len]) {
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len = lzma_memcmplen(pb, cur, len + 1, len_limit);
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if (len_best < len) {
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len_best = len;
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matches->len = len;
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matches->dist = delta - 1;
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++matches;
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if (len == len_limit) {
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*ptr1 = pair[0];
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*ptr0 = pair[1];
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return matches;
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}
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}
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}
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if (pb[len] < cur[len]) {
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*ptr1 = cur_match;
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ptr1 = pair + 1;
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cur_match = *ptr1;
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len1 = len;
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} else {
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*ptr0 = cur_match;
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ptr0 = pair;
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cur_match = *ptr0;
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len0 = len;
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}
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}
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}
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static void
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bt_skip_func(
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const uint32_t len_limit,
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const uint32_t pos,
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const uint8_t *const cur,
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uint32_t cur_match,
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uint32_t depth,
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uint32_t *const son,
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const uint32_t cyclic_pos,
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const uint32_t cyclic_size)
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{
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uint32_t *ptr0 = son + (cyclic_pos << 1) + 1;
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uint32_t *ptr1 = son + (cyclic_pos << 1);
|
|
|
|
uint32_t len0 = 0;
|
|
uint32_t len1 = 0;
|
|
|
|
while (true) {
|
|
const uint32_t delta = pos - cur_match;
|
|
if (depth-- == 0 || delta >= cyclic_size) {
|
|
*ptr0 = EMPTY_HASH_VALUE;
|
|
*ptr1 = EMPTY_HASH_VALUE;
|
|
return;
|
|
}
|
|
|
|
uint32_t *pair = son + ((cyclic_pos - delta
|
|
+ (delta > cyclic_pos ? cyclic_size : 0))
|
|
<< 1);
|
|
const uint8_t *pb = cur - delta;
|
|
uint32_t len = my_min(len0, len1);
|
|
|
|
if (pb[len] == cur[len]) {
|
|
len = lzma_memcmplen(pb, cur, len + 1, len_limit);
|
|
|
|
if (len == len_limit) {
|
|
*ptr1 = pair[0];
|
|
*ptr0 = pair[1];
|
|
return;
|
|
}
|
|
}
|
|
|
|
if (pb[len] < cur[len]) {
|
|
*ptr1 = cur_match;
|
|
ptr1 = pair + 1;
|
|
cur_match = *ptr1;
|
|
len1 = len;
|
|
} else {
|
|
*ptr0 = cur_match;
|
|
ptr0 = pair;
|
|
cur_match = *ptr0;
|
|
len0 = len;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
#define bt_find(len_best) \
|
|
call_find(bt_find_func, len_best)
|
|
|
|
#define bt_skip() \
|
|
do { \
|
|
bt_skip_func(len_limit, pos, cur, cur_match, mf->depth, \
|
|
mf->son, mf->cyclic_pos, \
|
|
mf->cyclic_size); \
|
|
move_pos(mf); \
|
|
} while (0)
|
|
|
|
#endif
|
|
|
|
|
|
#ifdef HAVE_MF_BT2
|
|
extern uint32_t
|
|
lzma_mf_bt2_find(lzma_mf *mf, lzma_match *matches)
|
|
{
|
|
header_find(true, 2);
|
|
|
|
hash_2_calc();
|
|
|
|
const uint32_t cur_match = mf->hash[hash_value];
|
|
mf->hash[hash_value] = pos;
|
|
|
|
bt_find(1);
|
|
}
|
|
|
|
|
|
extern void
|
|
lzma_mf_bt2_skip(lzma_mf *mf, uint32_t amount)
|
|
{
|
|
do {
|
|
header_skip(true, 2);
|
|
|
|
hash_2_calc();
|
|
|
|
const uint32_t cur_match = mf->hash[hash_value];
|
|
mf->hash[hash_value] = pos;
|
|
|
|
bt_skip();
|
|
|
|
} while (--amount != 0);
|
|
}
|
|
#endif
|
|
|
|
|
|
#ifdef HAVE_MF_BT3
|
|
extern uint32_t
|
|
lzma_mf_bt3_find(lzma_mf *mf, lzma_match *matches)
|
|
{
|
|
header_find(true, 3);
|
|
|
|
hash_3_calc();
|
|
|
|
const uint32_t delta2 = pos - mf->hash[hash_2_value];
|
|
const uint32_t cur_match = mf->hash[FIX_3_HASH_SIZE + hash_value];
|
|
|
|
mf->hash[hash_2_value] = pos;
|
|
mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
|
|
|
|
uint32_t len_best = 2;
|
|
|
|
if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
|
|
len_best = lzma_memcmplen(
|
|
cur, cur - delta2, len_best, len_limit);
|
|
|
|
matches[0].len = len_best;
|
|
matches[0].dist = delta2 - 1;
|
|
matches_count = 1;
|
|
|
|
if (len_best == len_limit) {
|
|
bt_skip();
|
|
return 1; // matches_count
|
|
}
|
|
}
|
|
|
|
bt_find(len_best);
|
|
}
|
|
|
|
|
|
extern void
|
|
lzma_mf_bt3_skip(lzma_mf *mf, uint32_t amount)
|
|
{
|
|
do {
|
|
header_skip(true, 3);
|
|
|
|
hash_3_calc();
|
|
|
|
const uint32_t cur_match
|
|
= mf->hash[FIX_3_HASH_SIZE + hash_value];
|
|
|
|
mf->hash[hash_2_value] = pos;
|
|
mf->hash[FIX_3_HASH_SIZE + hash_value] = pos;
|
|
|
|
bt_skip();
|
|
|
|
} while (--amount != 0);
|
|
}
|
|
#endif
|
|
|
|
|
|
#ifdef HAVE_MF_BT4
|
|
extern uint32_t
|
|
lzma_mf_bt4_find(lzma_mf *mf, lzma_match *matches)
|
|
{
|
|
header_find(true, 4);
|
|
|
|
hash_4_calc();
|
|
|
|
uint32_t delta2 = pos - mf->hash[hash_2_value];
|
|
const uint32_t delta3
|
|
= pos - mf->hash[FIX_3_HASH_SIZE + hash_3_value];
|
|
const uint32_t cur_match = mf->hash[FIX_4_HASH_SIZE + hash_value];
|
|
|
|
mf->hash[hash_2_value] = pos;
|
|
mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
|
|
mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
|
|
|
|
uint32_t len_best = 1;
|
|
|
|
if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
|
|
len_best = 2;
|
|
matches[0].len = 2;
|
|
matches[0].dist = delta2 - 1;
|
|
matches_count = 1;
|
|
}
|
|
|
|
if (delta2 != delta3 && delta3 < mf->cyclic_size
|
|
&& *(cur - delta3) == *cur) {
|
|
len_best = 3;
|
|
matches[matches_count++].dist = delta3 - 1;
|
|
delta2 = delta3;
|
|
}
|
|
|
|
if (matches_count != 0) {
|
|
len_best = lzma_memcmplen(
|
|
cur, cur - delta2, len_best, len_limit);
|
|
|
|
matches[matches_count - 1].len = len_best;
|
|
|
|
if (len_best == len_limit) {
|
|
bt_skip();
|
|
return matches_count;
|
|
}
|
|
}
|
|
|
|
if (len_best < 3)
|
|
len_best = 3;
|
|
|
|
bt_find(len_best);
|
|
}
|
|
|
|
|
|
extern void
|
|
lzma_mf_bt4_skip(lzma_mf *mf, uint32_t amount)
|
|
{
|
|
do {
|
|
header_skip(true, 4);
|
|
|
|
hash_4_calc();
|
|
|
|
const uint32_t cur_match
|
|
= mf->hash[FIX_4_HASH_SIZE + hash_value];
|
|
|
|
mf->hash[hash_2_value] = pos;
|
|
mf->hash[FIX_3_HASH_SIZE + hash_3_value] = pos;
|
|
mf->hash[FIX_4_HASH_SIZE + hash_value] = pos;
|
|
|
|
bt_skip();
|
|
|
|
} while (--amount != 0);
|
|
}
|
|
#endif
|