diff options
Diffstat (limited to 'source')
| -rw-r--r-- | source/core/slang-byte-encode-util.cpp | 72 |
1 files changed, 36 insertions, 36 deletions
diff --git a/source/core/slang-byte-encode-util.cpp b/source/core/slang-byte-encode-util.cpp index c542cc265..c7022397f 100644 --- a/source/core/slang-byte-encode-util.cpp +++ b/source/core/slang-byte-encode-util.cpp @@ -196,6 +196,34 @@ static const uint32_t s_unalignedUInt32Mask[5] = 0xffffffff, }; +// Decode the >= kLiteCut2. +// in is pointing past the first byte. +// Only valid numBytesRemaining is 2, 3, or 4 +SLANG_FORCE_INLINE static uint32_t _decodeLiteCut2UInt32(const uint8_t* in, int numBytesRemaining) +{ + uint32_t value = 0; +#if SLANG_BYTE_ENCODE_USE_UNALIGNED_ACCESS + switch (numBytesRemaining) + { + case 2: value = *(const uint16_t*)in; break; + case 3: value = (uint32_t(in[2]) << 16) | (uint32_t(in[1]) << 8) | uint32_t(in[0]); break; + case 4: value = *(const uint32_t*)in; break; + default: break; + } +#else + // This works on all cpus although slower + value = in[0]; + switch (numBytesRemaining) + { + case 4: value |= uint32_t(in[3]) << 24; /* fall thru */ + case 3: value |= uint32_t(in[2]) << 16; /* fall thru */ + case 2: value |= uint32_t(in[1]) << 8; /* fall thru */ + case 1: break; + } +#endif + return value; +} + /* static */int ByteEncodeUtil::decodeLiteUInt32(const uint8_t* in, uint32_t* out) { uint8_t b0 = *in++; @@ -212,25 +240,8 @@ static const uint32_t s_unalignedUInt32Mask[5] = } else { - int numBytesRemaining = b0 - kLiteCut2 + 2 - 1; - -#if SLANG_BYTE_ENCODE_USE_UNALIGNED_ACCESS - //const uint32_t mask = s_unalignedUInt32Mask[numBytesRemaining]; - const uint32_t mask = ~(uint32_t(0xffffff00) << ((numBytesRemaining - 1) * 8)); - const uint32_t value = (*(const uint32_t*)in) & mask; -#else - // This works on all cpus although slower - uint32_t value = in[0]; - - switch (numBytesRemaining) - { - case 4: value |= uint32_t(in[3]) << 24; /* fall thru */ - case 3: value |= uint32_t(in[2]) << 16; /* fall thru */ - case 2: value |= uint32_t(in[1]) << 8; /* fall thru */ - case 1: break; - } -#endif - *out = value; + const int numBytesRemaining = b0 - kLiteCut2 + 2 - 1; + *out = _decodeLiteCut2UInt32(in, numBytesRemaining); return numBytesRemaining + 1; } } @@ -253,34 +264,23 @@ static const uint32_t s_unalignedUInt32Mask[5] = } else { - int numBytesRemaining = b0 - kLiteCut2 + 2 - 1; + const int numBytesRemaining = b0 - kLiteCut2 + 2 - 1; -#if SLANG_BYTE_ENCODE_USE_UNALIGNED_ACCESS - uint32_t value = 0; - // Do not use unaligned access for the last two values, + // For unaligned access, do not use unaligned access for the last two values, // (3rd last is safe because this value will have at least 2 bytes, followed by at worst two 1-byte values) // otherwise we can access outside the bounds of the encoded array // This prevents memory validation tools from causing an exception here - if (i < numValues - 2) + if (SLANG_BYTE_ENCODE_USE_UNALIGNED_ACCESS && i < numValues - 2) { const uint32_t mask = s_unalignedUInt32Mask[numBytesRemaining]; //const uint32_t mask = ~(uint32_t(0xffffff00) << ((numBytesRemaining - 1) * 8)); - value = (*(const uint32_t*)encodeIn) & mask; + valuesOut[i] = (*(const uint32_t*)encodeIn) & mask; } else -#endif { - // This works on all cpus although slower - value = encodeIn[0]; - switch (numBytesRemaining) - { - case 4: value |= uint32_t(encodeIn[3]) << 24; /* fall thru */ - case 3: value |= uint32_t(encodeIn[2]) << 16; /* fall thru */ - case 2: value |= uint32_t(encodeIn[1]) << 8; /* fall thru */ - case 1: break; - } + valuesOut[i] = _decodeLiteCut2UInt32(encodeIn, numBytesRemaining); } - valuesOut[i] = value; + encodeIn += numBytesRemaining; } } |