590402bb5
Denys Vlasenko
2017-01-09
Subject
unlzma: expand comments, no code changes
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archival/libarchive/decompress_unlzma.c+18 -0
| @@ -432,6 +432,21 @@ unpack_lzma_stream(transformer_state_t *xstate) | |
| } | |
| len += LZMA_MATCH_MIN_LEN; | |
| + | /* |
| + | * LZMA SDK has this optimized: |
| + | * it precalculates size and copies many bytes |
| + | * in a loop with simpler checks, a-la: |
| + | * do |
| + | * *(dest) = *(dest + ofs); |
| + | * while (++dest != lim); |
| + | * and |
| + | * do { |
| + | * buffer[buffer_pos++] = buffer[pos]; |
| + | * if (++pos == header.dict_size) |
| + | * pos = 0; |
| + | * } while (--cur_len != 0); |
| + | * Our code is slower (more checks per byte copy): |
| + | */ |
| IF_NOT_FEATURE_LZMA_FAST(string:) | |
| do { | |
| uint32_t pos = buffer_pos - rep0; | |
| @@ -451,6 +466,9 @@ unpack_lzma_stream(transformer_state_t *xstate) | |
| } while (len != 0 && buffer_pos < header.dst_size); | |
| /* FIXME: ...........^^^^^ | |
| * shouldn't it be "global_pos + buffer_pos < header.dst_size"? | |
| + | * It probably should, but it is a "do we accidentally |
| + | * unpack more bytes than expected?" check - which |
| + | * never happens for well-formed compression data... |
| */ | |
| } | |
| } | |