diff options
Diffstat (limited to '')
| -rw-r--r-- | src/liblzma/lz/lz_decoder.c | 48 |
1 files changed, 34 insertions, 14 deletions
diff --git a/src/liblzma/lz/lz_decoder.c b/src/liblzma/lz/lz_decoder.c index 06c95c1..92913f2 100644 --- a/src/liblzma/lz/lz_decoder.c +++ b/src/liblzma/lz/lz_decoder.c @@ -1,3 +1,5 @@ +// SPDX-License-Identifier: 0BSD + /////////////////////////////////////////////////////////////////////////////// // /// \file lz_decoder.c @@ -6,9 +8,6 @@ // Authors: Igor Pavlov // Lasse Collin // -// This file has been put into the public domain. -// You can do whatever you want with this file. -// /////////////////////////////////////////////////////////////////////////////// // liblzma supports multiple LZ77-based filters. The LZ part is shared @@ -54,9 +53,10 @@ typedef struct { static void lz_decoder_reset(lzma_coder *coder) { - coder->dict.pos = 0; + coder->dict.pos = 2 * LZ_DICT_REPEAT_MAX; coder->dict.full = 0; - coder->dict.buf[coder->dict.size - 1] = '\0'; + coder->dict.buf[2 * LZ_DICT_REPEAT_MAX - 1] = '\0'; + coder->dict.has_wrapped = false; coder->dict.need_reset = false; return; } @@ -70,8 +70,15 @@ decode_buffer(lzma_coder *coder, { while (true) { // Wrap the dictionary if needed. - if (coder->dict.pos == coder->dict.size) - coder->dict.pos = 0; + if (coder->dict.pos == coder->dict.size) { + // See the comment of #define LZ_DICT_REPEAT_MAX. + coder->dict.pos = LZ_DICT_REPEAT_MAX; + coder->dict.has_wrapped = true; + memcpy(coder->dict.buf, coder->dict.buf + + coder->dict.size + - LZ_DICT_REPEAT_MAX, + LZ_DICT_REPEAT_MAX); + } // Store the current dictionary position. It is needed to know // where to start copying to the out[] buffer. @@ -253,21 +260,31 @@ lzma_lz_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, // dictionary to the output buffer, since applications are // recommended to give aligned buffers to liblzma. // + // Reserve 2 * LZ_DICT_REPEAT_MAX bytes of extra space which is + // needed for alloc_size. + // // Avoid integer overflow. - if (lz_options.dict_size > SIZE_MAX - 15) + if (lz_options.dict_size > SIZE_MAX - 15 - 2 * LZ_DICT_REPEAT_MAX) return LZMA_MEM_ERROR; lz_options.dict_size = (lz_options.dict_size + 15) & ~((size_t)(15)); + // Reserve extra space as explained in the comment + // of #define LZ_DICT_REPEAT_MAX. + const size_t alloc_size + = lz_options.dict_size + 2 * LZ_DICT_REPEAT_MAX; + // Allocate and initialize the dictionary. - if (coder->dict.size != lz_options.dict_size) { + if (coder->dict.size != alloc_size) { lzma_free(coder->dict.buf, allocator); - coder->dict.buf - = lzma_alloc(lz_options.dict_size, allocator); + coder->dict.buf = lzma_alloc(alloc_size, allocator); if (coder->dict.buf == NULL) return LZMA_MEM_ERROR; - coder->dict.size = lz_options.dict_size; + // NOTE: Yes, alloc_size, not lz_options.dict_size. The way + // coder->dict.full is updated will take care that we will + // still reject distances larger than lz_options.dict_size. + coder->dict.size = alloc_size; } lz_decoder_reset(next->coder); @@ -280,9 +297,12 @@ lzma_lz_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, const size_t copy_size = my_min(lz_options.preset_dict_size, lz_options.dict_size); const size_t offset = lz_options.preset_dict_size - copy_size; - memcpy(coder->dict.buf, lz_options.preset_dict + offset, + memcpy(coder->dict.buf + coder->dict.pos, + lz_options.preset_dict + offset, copy_size); - coder->dict.pos = copy_size; + + // dict.pos isn't zero after lz_decoder_reset(). + coder->dict.pos += copy_size; coder->dict.full = copy_size; } |