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Make zippy decompression branchless

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PiperOrigin-RevId: 342423961
This commit is contained in:
Snappy Team
2020-11-14 15:27:36 +00:00
committed by Victor Costan
parent 3bfa265a04
commit 289c8a3c0a
2 changed files with 210 additions and 6 deletions
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6
snappy-internal.h
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@@ -274,7 +274,8 @@ static const int kMaximumTagLength = 5; // COPY_4_BYTE_OFFSET plus the actual o
// because of efficiency reasons:
// (1) Extracting a byte is faster than a bit-field
// (2) It properly aligns copy offset so we do not need a <<8
static const uint16_t char_table[256] = {
static constexpr uint16_t char_table[256] = {
// clang-format off
0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
@@ -306,7 +307,8 @@ static const uint16_t char_table[256] = {
0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040,
// clang-format on
};
} // end namespace internal