//
// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// -----------------------------------------------------------------------------
// File: numbers.h
// -----------------------------------------------------------------------------
//
// This package contains functions for converting strings to numbers. For
// converting numbers to strings, use `StrCat()` or `StrAppend()` in str_cat.h,
// which automatically detect and convert most number values appropriately.
#ifndef ABSL_STRINGS_NUMBERS_H_
#define ABSL_STRINGS_NUMBERS_H_
#ifdef __SSE4_2__
#include <x86intrin.h>
#endif
#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <limits>
#include <string>
#include <type_traits>
#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 {
// SimpleAtoi()
//
// 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,
// returning `true` if successful.
// See https://en.cppreference.com/w/c/string/byte/strtof for details about the
// 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,
// returning `true` if successful.
// See https://en.cppreference.com/w/c/string/byte/strtof for details about the
// 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);
// SimpleAtob()
//
// Converts the given string into a boolean, returning `true` if successful.
// The following case-insensitive strings are interpreted as boolean `true`:
// "true", "t", "yes", "y", "1". The following case-insensitive strings
// are interpreted as boolean `false`: "false", "f", "no", "n", "0". If any
// errors are encountered, this function returns `false`, leaving `out` in an
// unspecified state.
ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* out);
} // namespace absl
// End of public API. Implementation details follow.
namespace absl {
namespace numbers_internal {
// Digit conversion.
extern const char kHexChar[17]; // 0123456789abcdef
extern const char kHexTable[513]; // 000102030405060708090a0b0c0d0e0f1011...
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;
// Helper function for fast formatting of floating-point values.
// The result is the same as printf's "%g", a.k.a. "%.6g"; that is, six
// significant digits are returned, trailing zeros are removed, and numbers
// outside the range 0.0001-999999 are output using scientific notation
// (1.23456e+06). This routine is heavily optimized.
// Required buffer size is `kSixDigitsToBufferSize`.
size_t SixDigitsToBuffer(double d, char* buffer);
// These functions are intended for speed. All functions take an output buffer
// as an argument and return a pointer to the last byte they wrote, which is the
// terminating '\0'. At most `kFastToBufferSize` bytes are written.
char* FastIntToBuffer(int32_t, char*);
char* FastIntToBuffer(uint32_t, char*);
char* FastIntToBuffer(int64_t, char*);
char* FastIntToBuffer(uint64_t, char*);
// For enums and integer types that are not an exact match for the types above,
// use templates to call the appropriate one of the four overloads above.
template <typename int_type>
char* FastIntToBuffer(int_type i, char* buffer) {
static_assert(sizeof(i) <= 64 / 8,
"FastIntToBuffer works only with 64-bit-or-less integers.");
// TODO(jorg): This signed-ness check is used because it works correctly
// with enums, and it also serves to check that int_type is not a pointer.
// If one day something like std::is_signed<enum E> works, switch to it.
if (static_cast<int_type>(1) - 2 < 0) { // Signed
if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
return FastIntToBuffer(static_cast<int64_t>(i), buffer);
} else { // 32-bit or less
return FastIntToBuffer(static_cast<int32_t>(i), buffer);
}
} else { // Unsigned
if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
return FastIntToBuffer(static_cast<uint64_t>(i), buffer);
} else { // 32-bit or less
return FastIntToBuffer(static_cast<uint32_t>(i), buffer);
}
}
}
// Implementation of SimpleAtoi, generalized to support arbitrary base (used
// with base different from 10 elsewhere in Abseil implementation).
template <typename int_type>
ABSL_MUST_USE_RESULT bool safe_strtoi_base(absl::string_view s, int_type* out,
int base) {
static_assert(sizeof(*out) == 4 || sizeof(*out) == 8,
"SimpleAtoi works only with 32-bit or 64-bit integers.");
static_assert(!std::is_floating_point<int_type>::value,
"Use SimpleAtof or SimpleAtod instead.");
bool parsed;
// TODO(jorg): This signed-ness check is used because it works correctly
// with enums, and it also serves to check that int_type is not a pointer.
// If one day something like std::is_signed<enum E> works, switch to it.
if (static_cast<int_type>(1) - 2 < 0) { // Signed
if (sizeof(*out) == 64 / 8) { // 64-bit
int64_t val;
parsed = numbers_internal::safe_strto64_base(s, &val, base);
*out = static_cast<int_type>(val);
} else { // 32-bit
int32_t val;
parsed = numbers_internal::safe_strto32_base(s, &val, base);
*out = static_cast<int_type>(val);
}
} else { // Unsigned
if (sizeof(*out) == 64 / 8) { // 64-bit
uint64_t val;
parsed = numbers_internal::safe_strtou64_base(s, &val, base);
*out = static_cast<int_type>(val);
} else { // 32-bit
uint32_t val;
parsed = numbers_internal::safe_strtou32_base(s, &val, base);
*out = static_cast<int_type>(val);
}
}
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()
//
// Converts a string to an integer, using `safe_strto?()` functions for actual
// parsing, returning `true` if successful. The `safe_strto?()` functions apply
// strict checking; the string must be a base-10 integer, optionally followed or
// preceded by ASCII whitespace, with a value in the range of the corresponding
// integer type.
template <typename int_type>
ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view str, int_type* out) {
return numbers_internal::safe_strtoi_base(str, out, 10);
}
ABSL_MUST_USE_RESULT inline bool SimpleAtoi(absl::string_view str,
absl::uint128* out) {
return numbers_internal::safe_strtou128_base(str, out, 10);
}
} // namespace absl
#endif // ABSL_STRINGS_NUMBERS_H_
