diff options
| -rw-r--r-- | snappy.cc | 38 |
1 files changed, 21 insertions, 17 deletions
@@ -157,26 +157,30 @@ static inline char* EmitLiteral(char* op, const char* literal, int len, bool allow_fast_path) { - int n = len - 1; // Zero-length literals are disallowed - if (n < 60) { + // The vast majority of copies are below 16 bytes, for which a + // call to memcpy is overkill. This fast path can sometimes + // copy up to 15 bytes too much, but that is okay in the + // main loop, since we have a bit to go on for both sides: + // + // - The input will always have kInputMarginBytes = 15 extra + // available bytes, as long as we're in the main loop, and + // if not, allow_fast_path = false. + // - The output will always have 32 spare bytes (see + // MaxCompressedLength). + assert(len > 0); // Zero-length literals are disallowed + int n = len - 1; + if (allow_fast_path && len <= 16) { // Fits in tag byte *op++ = LITERAL | (n << 2); - // The vast majority of copies are below 16 bytes, for which a - // call to memcpy is overkill. This fast path can sometimes - // copy up to 15 bytes too much, but that is okay in the - // main loop, since we have a bit to go on for both sides: - // - // - The input will always have kInputMarginBytes = 15 extra - // available bytes, as long as we're in the main loop, and - // if not, allow_fast_path = false. - // - The output will always have 32 spare bytes (see - // MaxCompressedLength). - if (allow_fast_path && len <= 16) { - UnalignedCopy64(literal, op); - UnalignedCopy64(literal + 8, op + 8); - return op + len; - } + UnalignedCopy64(literal, op); + UnalignedCopy64(literal + 8, op + 8); + return op + len; + } + + if (n < 60) { + // Fits in tag byte + *op++ = LITERAL | (n << 2); } else { // Encode in upcoming bytes char* base = op; |