mirror of https://git.tukaani.org/xz.git
Some fixes to LZ encoder.
This commit is contained in:
Lasse Collin
parent
ede675f9ac
commit
fc68165745
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@ -86,12 +86,16 @@ fill_window(lzma_coder *coder, lzma_allocator *allocator, const uint8_t *in,
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if (coder->mf.read_pos >= coder->mf.size - coder->mf.keep_size_after)
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move_window(&coder->mf);
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// Maybe this is ugly, but lzma_mf uses uint32_t for most things
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// (which I find cleanest), but we need size_t here when filling
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// the history window.
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size_t write_pos = coder->mf.write_pos;
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size_t in_used;
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lzma_ret ret;
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if (coder->next.code == NULL) {
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// Not using a filter, simply memcpy() as much as possible.
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in_used = lzma_bufcpy(in, in_pos, in_size, coder->mf.buffer,
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&coder->mf.write_pos, coder->mf.size);
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&write_pos, coder->mf.size);
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ret = action != LZMA_RUN && *in_pos == in_size
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? LZMA_STREAM_END : LZMA_OK;
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@ -100,11 +104,13 @@ fill_window(lzma_coder *coder, lzma_allocator *allocator, const uint8_t *in,
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const size_t in_start = *in_pos;
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ret = coder->next.code(coder->next.coder, allocator,
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in, in_pos, in_size,
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coder->mf.buffer, &coder->mf.write_pos,
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coder->mf.buffer, &write_pos,
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coder->mf.size, action);
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in_used = *in_pos - in_start;
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}
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coder->mf.write_pos = write_pos;
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// If end of stream has been reached or flushing completed, we allow
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// the encoder to process all the input (that is, read_pos is allowed
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// to reach write_pos). Otherwise we keep keep_size_after bytes
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@ -181,9 +187,12 @@ static bool
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lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
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const lzma_lz_options *lz_options)
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{
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// For now, the dictionary size is limited to 1.5 GiB. This may grow
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// in the future if needed, but it needs a little more work than just
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// changing this check.
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if (lz_options->dictionary_size < LZMA_DICTIONARY_SIZE_MIN
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|| lz_options->dictionary_size
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> LZMA_DICTIONARY_SIZE_MAX
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> (UINT32_C(1) << 30) + (UINT32_C(1) << 29)
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|| lz_options->find_len_max
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> lz_options->match_len_max)
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return true;
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@ -198,6 +207,13 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
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// memmove()s become more expensive when the size of the buffer
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// increases, we reserve more space when a large dictionary is
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// used to make the memmove() calls rarer.
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//
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// This works with dictionaries up to about 3 GiB. If bigger
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// dictionary is wanted, some extra work is needed:
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// - Several variables in lzma_mf have to be changed from uint32_t
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// to size_t.
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// - Memory usage calculation needs something too, e.g. use uint64_t
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// for mf->size.
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uint32_t reserve = lz_options->dictionary_size / 2;
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if (reserve > (UINT32_C(1) << 30))
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reserve /= 2;
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@ -208,8 +224,6 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
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const uint32_t old_size = mf->size;
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mf->size = mf->keep_size_before + reserve + mf->keep_size_after;
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// FIXME Integer overflows
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// Deallocate the old history buffer if it exists but has different
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// size than what is needed now.
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if (mf->buffer != NULL && old_size != mf->size) {
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@ -220,7 +234,23 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
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// Match finder options
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mf->match_len_max = lz_options->match_len_max;
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mf->find_len_max = lz_options->find_len_max;
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mf->cyclic_buffer_size = lz_options->dictionary_size + 1;
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// cyclic_size has to stay smaller than 2 Gi. Note that this doesn't
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// mean limitting dictionary size to less than 2 GiB. With a match
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// finder that uses multibyte resolution (hashes start at e.g. every
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// fourth byte), cyclic_size would stay below 2 Gi even when
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// dictionary size is greater than 2 GiB.
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//
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// It would be possible to allow cyclic_size >= 2 Gi, but then we
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// would need to be careful to use 64-bit types in various places
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// (size_t could do since we would need bigger than 32-bit address
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// space anyway). It would also require either zeroing a multigigabyte
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// buffer at initialization (waste of time and RAM) or allow
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// normalization in lz_encoder_mf.c to access uninitialized
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// memory to keep the code simpler. The current way is simple and
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// still allows pretty big dictionaries, so I don't expect these
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// limits to change.
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mf->cyclic_size = lz_options->dictionary_size + 1;
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// Validate the match finder ID and setup the function pointers.
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switch (lz_options->match_finder) {
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@ -298,9 +328,15 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
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hs += HASH_4_SIZE;
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*/
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// If the above code calculating hs is modified, make sure that
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// this assertion stays valid (UINT32_MAX / 5 is not strictly the
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// exact limit). If it doesn't, you need to calculate that
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// hash_size_sum + sons_count cannot overflow.
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assert(hs < UINT32_MAX / 5);
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const uint32_t old_count = mf->hash_size_sum + mf->sons_count;
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mf->hash_size_sum = hs;
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mf->sons_count = mf->cyclic_buffer_size;
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mf->sons_count = mf->cyclic_size;
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if (is_bt)
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mf->sons_count *= 2;
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@ -335,11 +371,11 @@ lz_encoder_init(lzma_mf *mf, lzma_allocator *allocator)
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return true;
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}
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// Use cyclic_buffer_size as initial mf->offset. This allows
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// Use cyclic_size as initial mf->offset. This allows
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// avoiding a few branches in the match finders. The downside is
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// that match finder needs to be normalized more often, which may
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// hurt performance with huge dictionaries.
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mf->offset = mf->cyclic_buffer_size;
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mf->offset = mf->cyclic_size;
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mf->read_pos = 0;
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mf->read_ahead = 0;
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mf->read_limit = 0;
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@ -364,7 +400,7 @@ lz_encoder_init(lzma_mf *mf, lzma_allocator *allocator)
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}
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mf->son = mf->hash + mf->hash_size_sum;
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mf->cyclic_buffer_pos = 0;
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mf->cyclic_pos = 0;
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// Initialize the hash table. Since EMPTY_HASH_VALUE is zero, we
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// can use memset().
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@ -53,18 +53,20 @@ struct lzma_mf_s {
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/// Number of bytes that must be kept in buffer after read_pos.
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/// That is, read_pos <= write_pos - keep_size_after as long as
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/// stream_end_was_reached is false (once it is true, read_pos
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/// is allowed to reach write_pos).
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/// action is LZMA_RUN; when action != LZMA_RUN, read_pos is allowed
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/// to reach write_pos so that the last bytes get encoded too.
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uint32_t keep_size_after;
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/// Match finders store locations of matches using 32-bit integers.
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/// To avoid adjusting several megabytes of integers every time the
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/// input window is moved with move_window(), we only adjust the
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/// offset of the buffer. Thus, buffer[match_finder_pos - offset]
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/// is the byte pointed by match_finder_pos.
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/// input window is moved with move_window, we only adjust the
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/// offset of the buffer. Thus, buffer[value_in_hash_table - offset]
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/// is the byte pointed by value_in_hash_table.
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uint32_t offset;
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/// buffer[read_pos] is the current byte.
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/// buffer[read_pos] is the next byte to run through the match
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/// finder. This is incremented in the match finder once the byte
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/// has been processed.
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uint32_t read_pos;
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/// Number of bytes that have been ran through the match finder, but
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@ -103,8 +105,8 @@ struct lzma_mf_s {
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uint32_t *hash;
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uint32_t *son;
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uint32_t cyclic_buffer_pos;
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uint32_t cyclic_buffer_size; // Must be dictionary_size + 1.
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uint32_t cyclic_pos;
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uint32_t cyclic_size; // Must be dictionary size + 1.
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uint32_t hash_mask;
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/// Maximum number of loops in the match finder
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@ -121,7 +121,7 @@ normalize(lzma_mf *mf)
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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_buffer_size);
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= (MUST_NORMALIZE_POS - mf->cyclic_size);
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// & (~(UINT32_C(1) << 10) - 1);
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const uint32_t count = mf->hash_size_sum + mf->sons_count;
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@ -155,8 +155,8 @@ normalize(lzma_mf *mf)
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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_buffer_pos == mf->cyclic_buffer_size)
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mf->cyclic_buffer_pos = 0;
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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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@ -177,7 +177,7 @@ move_pos(lzma_mf *mf)
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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_buffer_pos or test for
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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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@ -227,8 +227,7 @@ move_pending(lzma_mf *mf)
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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->loops, \
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mf->son, mf->cyclic_buffer_pos, \
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mf->cyclic_buffer_size, \
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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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@ -249,8 +248,8 @@ do { \
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/// \param cur_match Start position of the current match candidate
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/// \param loops 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_buffer_pos
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/// \param cyclic_buffer_size
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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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@ -261,22 +260,21 @@ hc_find_func(
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uint32_t cur_match,
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uint32_t loops,
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uint32_t *const son,
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const uint32_t cyclic_buffer_pos,
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const uint32_t cyclic_buffer_size,
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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_buffer_pos] = cur_match;
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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 (loops-- == 0 || delta >= cyclic_buffer_size)
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if (loops-- == 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_buffer_pos - delta
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+ (delta > cyclic_buffer_pos
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? cyclic_buffer_size : 0)];
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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 = 0;
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@ -297,23 +295,6 @@ hc_find_func(
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}
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}
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/*
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#define hc_header_find(len_min, ret_op) \
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uint32_t len_limit = mf_avail(mf); \
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if (mf->find_len_max <= len_limit) { \
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len_limit = mf->find_len_max; \
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} else if (len_limit < (len_min)) { \
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move_pending(mf); \
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ret_op; \
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} \
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#define header_hc(len_min, ret_op) \
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do { \
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if (mf_avail(mf) < (len_min)) { \
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move_pending(mf); \
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ret_op; \
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} \
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} while (0)
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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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@ -321,7 +302,7 @@ do { \
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#define hc_skip() \
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do { \
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mf->son[mf->cyclic_buffer_pos] = cur_match; \
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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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@ -344,7 +325,7 @@ lzma_mf_hc3_find(lzma_mf *mf, lzma_match *matches)
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uint32_t len_best = 2;
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if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
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if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
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for ( ; len_best != len_limit; ++len_best)
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if (*(cur + len_best - delta2) != cur[len_best])
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break;
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@ -409,14 +390,14 @@ lzma_mf_hc4_find(lzma_mf *mf, lzma_match *matches)
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uint32_t len_best = 1;
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if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
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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_buffer_size
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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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@ -484,28 +465,28 @@ bt_find_func(
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uint32_t cur_match,
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uint32_t loops,
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uint32_t *const son,
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const uint32_t cyclic_buffer_pos,
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const uint32_t cyclic_buffer_size,
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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_buffer_pos << 1) + 1;
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uint32_t *ptr1 = son + (cyclic_buffer_pos << 1);
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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 (loops-- == 0 || delta >= cyclic_buffer_size) {
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if (loops-- == 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_buffer_pos - delta
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+ (delta > cyclic_buffer_pos
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? cyclic_buffer_size : 0)) << 1);
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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 = MIN(len0, len1);
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@ -552,26 +533,26 @@ bt_skip_func(
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uint32_t cur_match,
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uint32_t loops,
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uint32_t *const son,
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const uint32_t cyclic_buffer_pos,
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const uint32_t cyclic_buffer_size)
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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_buffer_pos << 1) + 1;
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uint32_t *ptr1 = son + (cyclic_buffer_pos << 1);
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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 (loops-- == 0 || delta >= cyclic_buffer_size) {
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if (loops-- == 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;
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}
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uint32_t *pair = son + ((cyclic_buffer_pos - delta
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+ (delta > cyclic_buffer_pos
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? cyclic_buffer_size : 0)) << 1);
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uint32_t *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 *pb = cur - delta;
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uint32_t len = MIN(len0, len1);
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@ -608,8 +589,8 @@ bt_skip_func(
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#define bt_skip() \
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do { \
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bt_skip_func(len_limit, pos, cur, cur_match, mf->loops, \
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mf->son, mf->cyclic_buffer_pos, \
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mf->cyclic_buffer_size); \
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mf->son, mf->cyclic_pos, \
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mf->cyclic_size); \
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move_pos(mf); \
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} while (0)
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@ -665,7 +646,7 @@ lzma_mf_bt3_find(lzma_mf *mf, lzma_match *matches)
|
|||
|
||||
uint32_t len_best = 2;
|
||||
|
||||
if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
|
||||
if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
|
||||
for ( ; len_best != len_limit; ++len_best)
|
||||
if (*(cur + len_best - delta2) != cur[len_best])
|
||||
break;
|
||||
|
|
@ -724,14 +705,14 @@ lzma_mf_bt4_find(lzma_mf *mf, lzma_match *matches)
|
|||
|
||||
uint32_t len_best = 1;
|
||||
|
||||
if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
|
||||
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_buffer_size
|
||||
if (delta2 != delta3 && delta3 < mf->cyclic_size
|
||||
&& *(cur - delta3) == *cur) {
|
||||
len_best = 3;
|
||||
matches[matches_count++].dist = delta3 - 1;
|
||||
|
|
|
|||
Loading…
Reference in New Issue