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| author | Denys Vlasenko | 2017-01-09 13:55:11 +0100 |
|---|---|---|
| committer | Denys Vlasenko | 2017-01-09 14:02:55 +0100 |
| commit | 3989e5adf454a3ab98412b249c2c9bd2a3175ae0 (patch) | |
| tree | 8361ddd5dd5e4d35067ab4166f63aa482fece476 | |
| parent | 8c1d857d2582c689681c7e6d3dc299613b4a7167 (diff) | |
| download | busybox-3989e5adf454a3ab98412b249c2c9bd2a3175ae0.zip busybox-3989e5adf454a3ab98412b249c2c9bd2a3175ae0.tar.gz | |
unlzma: fix erroneous "while" instead of "if". Closes 4682
These parts of the code essentially check whether
stepping back by rep0 goes negative or not.
LZMA SDK from lzma1604.7z has the following in the corresponding places:
... = dic[dicPos - rep0 + (dicPos < rep0 ? dicBufSize : 0)]
Clearly, not loop here.
Technically, "while" here works: if condition is false (because pos
underflowed), it iterates once, adds header.dict_size (a.k.a. dicBufSize),
this makes pos positive but smaller than header.dict_size, and loop exits.
Now we'll just check for negative result of subtraction, which is less code:
function old new delta
unpack_lzma_stream 2659 2641 -18
(I hope 2 Gbyte+ dictionaries won't be in use soon).
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
| -rw-r--r-- | archival/libarchive/decompress_unlzma.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/archival/libarchive/decompress_unlzma.c b/archival/libarchive/decompress_unlzma.c index c8622f9..90a4285 100644 --- a/archival/libarchive/decompress_unlzma.c +++ b/archival/libarchive/decompress_unlzma.c @@ -278,9 +278,10 @@ unpack_lzma_stream(transformer_state_t *xstate) if (state >= LZMA_NUM_LIT_STATES) { int match_byte; - uint32_t pos = buffer_pos - rep0; + uint32_t pos; - while (pos >= header.dict_size) + pos = buffer_pos - rep0; + if ((int32_t)pos < 0) pos += header.dict_size; match_byte = buffer[pos]; do { @@ -336,9 +337,11 @@ unpack_lzma_stream(transformer_state_t *xstate) ); if (!rc_is_bit_1(rc, prob2)) { #if ENABLE_FEATURE_LZMA_FAST - uint32_t pos = buffer_pos - rep0; + uint32_t pos; state = state < LZMA_NUM_LIT_STATES ? 9 : 11; - while (pos >= header.dict_size) + + pos = buffer_pos - rep0; + if ((int32_t)pos < 0) pos += header.dict_size; previous_byte = buffer[pos]; goto one_byte1; @@ -432,7 +435,7 @@ unpack_lzma_stream(transformer_state_t *xstate) IF_NOT_FEATURE_LZMA_FAST(string:) do { uint32_t pos = buffer_pos - rep0; - while (pos >= header.dict_size) + if ((int32_t)pos < 0) pos += header.dict_size; previous_byte = buffer[pos]; IF_NOT_FEATURE_LZMA_FAST(one_byte2:) |