diff options
Diffstat (limited to 'absl/strings/numbers.h')
-rw-r--r-- | absl/strings/numbers.h | 99 |
1 files changed, 86 insertions, 13 deletions
diff --git a/absl/strings/numbers.h b/absl/strings/numbers.h index e9878016..d872cca5 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> @@ -32,39 +36,54 @@ #include <string> #include <type_traits> +#include "absl/base/config.h" +#include "absl/base/internal/bits.h" +#ifdef __SSE4_2__ +// TODO(jorg): Remove this when we figure out the right way +// to swap bytes on SSE 4.2 that works with the compilers +// we claim to support. Also, add tests for the compiler +// that doesn't support the Intel _bswap64 intrinsic but +// does support all the SSE 4.2 intrinsics +#include "absl/base/internal/endian.h" +#endif #include "absl/base/macros.h" #include "absl/base/port.h" #include "absl/numeric/int128.h" #include "absl/strings/string_view.h" namespace absl { -inline namespace lts_2019_08_08 { +ABSL_NAMESPACE_BEGIN // SimpleAtoi() // -// Converts the given string into an integer value, returning `true` if -// successful. The string must reflect a base-10 integer (optionally followed or -// preceded by ASCII whitespace) whose value falls within the range of the -// integer type. If any errors are encountered, this function returns `false`, -// leaving `out` in an unspecified state. +// Converts the given string (optionally followed or preceded by ASCII +// whitespace) into an integer value, returning `true` if successful. The string +// must reflect a base-10 integer whose value falls within the range of the +// integer type (optionally preceded by a `+` or `-`). If any errors are +// encountered, this function returns `false`, leaving `out` in an unspecified +// state. template <typename int_type> ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view str, int_type* out); // SimpleAtof() // // Converts the given string (optionally followed or preceded by ASCII -// whitespace) into a float, which may be rounded on overflow or underflow. +// whitespace) into a float, which may be rounded on overflow or underflow, +// returning `true` if successful. // 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-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 SimpleAtof(absl::string_view str, float* out); // SimpleAtod() // // Converts the given string (optionally followed or preceded by ASCII -// whitespace) into a double, which may be rounded on overflow or underflow. +// whitespace) into a double, which may be rounded on overflow or underflow, +// returning `true` if successful. // 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); @@ -78,20 +97,40 @@ ABSL_MUST_USE_RESULT bool SimpleAtod(absl::string_view str, double* out); // unspecified state. ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* out); -} // inline namespace lts_2019_08_08 +ABSL_NAMESPACE_END } // namespace absl // End of public API. Implementation details follow. namespace absl { -inline namespace lts_2019_08_08 { +ABSL_NAMESPACE_BEGIN namespace numbers_internal { +// Digit conversion. +ABSL_DLL extern const char kHexChar[17]; // 0123456789abcdef +ABSL_DLL extern const char + kHexTable[513]; // 000102030405060708090a0b0c0d0e0f1011... +ABSL_DLL extern const char + two_ASCII_digits[100][2]; // 00, 01, 02, 03... + +// Writes a two-character representation of 'i' to 'buf'. 'i' must be in the +// range 0 <= i < 100, and buf must have space for two characters. Example: +// char buf[2]; +// PutTwoDigits(42, buf); +// // buf[0] == '4' +// // buf[1] == '2' +inline void PutTwoDigits(size_t i, char* buf) { + assert(i < 100); + memcpy(buf, two_ASCII_digits[i], 2); +} + // 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); bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base); bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base); +bool safe_strtou128_base(absl::string_view text, absl::uint128* value, + int base); static const int kFastToBufferSize = 32; static const int kSixDigitsToBufferSize = 16; @@ -173,6 +212,35 @@ 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) { +#ifdef __SSE4_2__ + uint64_t be = absl::big_endian::FromHost64(val); + 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_loadl_epi64(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 = (val >> (56 - 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() @@ -187,7 +255,12 @@ ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view str, int_type* out) { return numbers_internal::safe_strtoi_base(str, out, 10); } -} // inline namespace lts_2019_08_08 +ABSL_MUST_USE_RESULT inline bool SimpleAtoi(absl::string_view str, + absl::uint128* out) { + return numbers_internal::safe_strtou128_base(str, out, 10); +} + +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_STRINGS_NUMBERS_H_ |