diff options
Diffstat (limited to 'absl/strings/numbers.h')
| -rw-r--r-- | absl/strings/numbers.h | 45 |
1 files changed, 43 insertions, 2 deletions
diff --git a/absl/strings/numbers.h b/absl/strings/numbers.h index 100839b04626..745de67ad86d 100644 --- a/absl/strings/numbers.h +++ b/absl/strings/numbers.h @@ -24,6 +24,10 @@ #ifndef ABSL_STRINGS_NUMBERS_H_ #define ABSL_STRINGS_NUMBERS_H_ +#ifdef __SSE4_2__ +#include <x86intrin.h> +#endif + #include <cstddef> #include <cstdlib> #include <cstring> @@ -32,6 +36,8 @@ #include <string> #include <type_traits> +#include "absl/base/internal/bits.h" +#include "absl/base/internal/endian.h" #include "absl/base/macros.h" #include "absl/base/port.h" #include "absl/numeric/int128.h" @@ -54,7 +60,8 @@ ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view str, int_type* out); // Converts the given string (optionally followed or preceded by ASCII // whitespace) into a float, which may be rounded on overflow or underflow. // See https://en.cppreference.com/w/c/string/byte/strtof for details about the -// allowed formats for `str`. If any errors are encountered, this function +// allowed formats for `str`, except SimpleAtof() is locale-indepdent and will +// always use the "C" locale. If any errors are encountered, this function // returns `false`, leaving `out` in an unspecified state. ABSL_MUST_USE_RESULT bool SimpleAtof(absl::string_view str, float* out); @@ -63,7 +70,8 @@ ABSL_MUST_USE_RESULT bool SimpleAtof(absl::string_view str, float* out); // Converts the given string (optionally followed or preceded by ASCII // whitespace) into a double, which may be rounded on overflow or underflow. // See https://en.cppreference.com/w/c/string/byte/strtof for details about the -// allowed formats for `str`. If any errors are encountered, this function +// allowed formats for `str`, except SimpleAtod is locale-independent and will +// always use the "C" locale. If any errors are encountered, this function // returns `false`, leaving `out` in an unspecified state. ABSL_MUST_USE_RESULT bool SimpleAtod(absl::string_view str, double* out); @@ -84,6 +92,10 @@ ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* out); namespace absl { namespace numbers_internal { +// Digit conversion. +extern const char kHexChar[17]; // 0123456789abcdef +extern const char kHexTable[513]; // 000102030405060708090a0b0c0d0e0f1011... + // safe_strto?() functions for implementing SimpleAtoi() bool safe_strto32_base(absl::string_view text, int32_t* value, int base); bool safe_strto64_base(absl::string_view text, int64_t* value, int base); @@ -170,6 +182,35 @@ ABSL_MUST_USE_RESULT bool safe_strtoi_base(absl::string_view s, int_type* out, return parsed; } +// FastHexToBufferZeroPad16() +// +// Outputs `val` into `out` as if by `snprintf(out, 17, "%016x", val)` but +// without the terminating null character. Thus `out` must be of length >= 16. +// Returns the number of non-pad digits of the output (it can never be zero +// since 0 has one digit). +inline size_t FastHexToBufferZeroPad16(uint64_t val, char* out) { + uint64_t be = absl::big_endian::FromHost64(val); +#ifdef __SSE4_2__ + const auto kNibbleMask = _mm_set1_epi8(0xf); + const auto kHexDigits = _mm_setr_epi8('0', '1', '2', '3', '4', '5', '6', '7', + '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'); + auto v = _mm_loadu_si64(reinterpret_cast<__m128i*>(&be)); // load lo dword + auto v4 = _mm_srli_epi64(v, 4); // shift 4 right + auto il = _mm_unpacklo_epi8(v4, v); // interleave bytes + auto m = _mm_and_si128(il, kNibbleMask); // mask out nibbles + auto hexchars = _mm_shuffle_epi8(kHexDigits, m); // hex chars + _mm_storeu_si128(reinterpret_cast<__m128i*>(out), hexchars); +#else + for (int i = 0; i < 8; ++i) { + auto byte = (be >> (8 * i)) & 0xFF; + auto* hex = &absl::numbers_internal::kHexTable[byte * 2]; + std::memcpy(out + 2 * i, hex, 2); + } +#endif + // | 0x1 so that even 0 has 1 digit. + return 16 - absl::base_internal::CountLeadingZeros64(val | 0x1) / 4; +} + } // namespace numbers_internal // SimpleAtoi() |