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Improve comments in IncrementalCopy, add an assert. 

PiperOrigin-RevId: 292506754
This commit is contained in:
Snappy Team 2020-01-31 09:44:03 +00:00 committed by Victor Costan
parent 537f4ad624
commit cddd9c0875
1 changed files with 6 additions and 3 deletions
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snappy.cc
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@ -190,9 +190,12 @@ inline char* IncrementalCopy(const char* src, char* op, char* const op_limit,
assert(src < op);
assert(op <= op_limit);
assert(op_limit <= buf_limit);
// NOTE: The compressor always emits 4 <= len <= 64. It is ok to assume that
// to optimize this function but we have to also handle other cases in case
// the input does not satisfy these conditions.
// NOTE: The copy tags use 3 or 6 bits to store the copy length, so len <= 64.
assert(op_limit - op <= 64);
// NOTE: In practice the compressor always emits len >= 4, so it is ok to
// assume that to optimize this function, but this is not guaranteed by the
// compression format, so we have to also handle len < 4 in case the input
// does not satisfy these conditions.
size_t pattern_size = op - src;
// The cases are split into different branches to allow the branch predictor,