diff options
Diffstat (limited to 'src/liblzma/simple')
| -rw-r--r-- | src/liblzma/simple/arm64.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/liblzma/simple/arm64.c b/src/liblzma/simple/arm64.c index 911e30c1..0437f736 100644 --- a/src/liblzma/simple/arm64.c +++ b/src/liblzma/simple/arm64.c @@ -72,6 +72,9 @@ arm64_code(void *simple_ptr, uint32_t now_pos, bool is_encoder, src <<= 2; src &= ADDR28_MASK; + // When the conversion width isn't the maximum, + // check that the highest bits are either all zero + // or all one. if ((src & sign_mask) != 0 && (src & sign_mask) != sign_mask) continue; @@ -197,7 +200,17 @@ arm64_coder_init(lzma_next_coder *next, const lzma_allocator *allocator, lzma_simple_coder *coder = next->coder; lzma_simple_arm64 *simple = coder->simple; + // This will be used to detect if the value, after + // conversion has been done, is negative. The location + // of the sign bit depends on the conversion width. simple->sign_bit = UINT32_C(1) << (opt->width - 1); + + // When conversion width isn't the maximum, the highest + // bits must all be either zero or one, that is, they + // all are copies of the sign bit. This mask is used to + // (1) detect if input value is in the range specified + // by the conversion width and (2) clearing or setting + // the high bits after conversion (integers can wrap around). simple->sign_mask = (UINT32_C(1) << 28) - simple->sign_bit; } |