diff options
Diffstat (limited to '')
| -rw-r--r-- | src/liblzma/lz/lz_encoder.c | 56 |
1 files changed, 46 insertions, 10 deletions
diff --git a/src/liblzma/lz/lz_encoder.c b/src/liblzma/lz/lz_encoder.c index d5f84826..6a39d0f5 100644 --- a/src/liblzma/lz/lz_encoder.c +++ b/src/liblzma/lz/lz_encoder.c @@ -86,12 +86,16 @@ fill_window(lzma_coder *coder, lzma_allocator *allocator, const uint8_t *in, if (coder->mf.read_pos >= coder->mf.size - coder->mf.keep_size_after) move_window(&coder->mf); + // Maybe this is ugly, but lzma_mf uses uint32_t for most things + // (which I find cleanest), but we need size_t here when filling + // the history window. + size_t write_pos = coder->mf.write_pos; size_t in_used; lzma_ret ret; if (coder->next.code == NULL) { // Not using a filter, simply memcpy() as much as possible. in_used = lzma_bufcpy(in, in_pos, in_size, coder->mf.buffer, - &coder->mf.write_pos, coder->mf.size); + &write_pos, coder->mf.size); ret = action != LZMA_RUN && *in_pos == in_size ? LZMA_STREAM_END : LZMA_OK; @@ -100,11 +104,13 @@ fill_window(lzma_coder *coder, lzma_allocator *allocator, const uint8_t *in, const size_t in_start = *in_pos; ret = coder->next.code(coder->next.coder, allocator, in, in_pos, in_size, - coder->mf.buffer, &coder->mf.write_pos, + coder->mf.buffer, &write_pos, coder->mf.size, action); in_used = *in_pos - in_start; } + coder->mf.write_pos = write_pos; + // If end of stream has been reached or flushing completed, we allow // the encoder to process all the input (that is, read_pos is allowed // to reach write_pos). Otherwise we keep keep_size_after bytes @@ -181,9 +187,12 @@ static bool lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator, const lzma_lz_options *lz_options) { + // For now, the dictionary size is limited to 1.5 GiB. This may grow + // in the future if needed, but it needs a little more work than just + // changing this check. if (lz_options->dictionary_size < LZMA_DICTIONARY_SIZE_MIN || lz_options->dictionary_size - > LZMA_DICTIONARY_SIZE_MAX + > (UINT32_C(1) << 30) + (UINT32_C(1) << 29) || lz_options->find_len_max > lz_options->match_len_max) return true; @@ -198,6 +207,13 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator, // memmove()s become more expensive when the size of the buffer // increases, we reserve more space when a large dictionary is // used to make the memmove() calls rarer. + // + // This works with dictionaries up to about 3 GiB. If bigger + // dictionary is wanted, some extra work is needed: + // - Several variables in lzma_mf have to be changed from uint32_t + // to size_t. + // - Memory usage calculation needs something too, e.g. use uint64_t + // for mf->size. uint32_t reserve = lz_options->dictionary_size / 2; if (reserve > (UINT32_C(1) << 30)) reserve /= 2; @@ -208,8 +224,6 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator, const uint32_t old_size = mf->size; mf->size = mf->keep_size_before + reserve + mf->keep_size_after; - // FIXME Integer overflows - // Deallocate the old history buffer if it exists but has different // size than what is needed now. if (mf->buffer != NULL && old_size != mf->size) { @@ -220,7 +234,23 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator, // Match finder options mf->match_len_max = lz_options->match_len_max; mf->find_len_max = lz_options->find_len_max; - mf->cyclic_buffer_size = lz_options->dictionary_size + 1; + + // cyclic_size has to stay smaller than 2 Gi. Note that this doesn't + // mean limitting dictionary size to less than 2 GiB. With a match + // finder that uses multibyte resolution (hashes start at e.g. every + // fourth byte), cyclic_size would stay below 2 Gi even when + // dictionary size is greater than 2 GiB. + // + // It would be possible to allow cyclic_size >= 2 Gi, but then we + // would need to be careful to use 64-bit types in various places + // (size_t could do since we would need bigger than 32-bit address + // space anyway). It would also require either zeroing a multigigabyte + // buffer at initialization (waste of time and RAM) or allow + // normalization in lz_encoder_mf.c to access uninitialized + // memory to keep the code simpler. The current way is simple and + // still allows pretty big dictionaries, so I don't expect these + // limits to change. + mf->cyclic_size = lz_options->dictionary_size + 1; // Validate the match finder ID and setup the function pointers. switch (lz_options->match_finder) { @@ -298,9 +328,15 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator, hs += HASH_4_SIZE; */ + // If the above code calculating hs is modified, make sure that + // this assertion stays valid (UINT32_MAX / 5 is not strictly the + // exact limit). If it doesn't, you need to calculate that + // hash_size_sum + sons_count cannot overflow. + assert(hs < UINT32_MAX / 5); + const uint32_t old_count = mf->hash_size_sum + mf->sons_count; mf->hash_size_sum = hs; - mf->sons_count = mf->cyclic_buffer_size; + mf->sons_count = mf->cyclic_size; if (is_bt) mf->sons_count *= 2; @@ -335,11 +371,11 @@ lz_encoder_init(lzma_mf *mf, lzma_allocator *allocator) return true; } - // Use cyclic_buffer_size as initial mf->offset. This allows + // Use cyclic_size as initial mf->offset. This allows // avoiding a few branches in the match finders. The downside is // that match finder needs to be normalized more often, which may // hurt performance with huge dictionaries. - mf->offset = mf->cyclic_buffer_size; + mf->offset = mf->cyclic_size; mf->read_pos = 0; mf->read_ahead = 0; mf->read_limit = 0; @@ -364,7 +400,7 @@ lz_encoder_init(lzma_mf *mf, lzma_allocator *allocator) } mf->son = mf->hash + mf->hash_size_sum; - mf->cyclic_buffer_pos = 0; + mf->cyclic_pos = 0; // Initialize the hash table. Since EMPTY_HASH_VALUE is zero, we // can use memset(). |