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189 lines
7.5 KiB
C++
189 lines
7.5 KiB
C++
//
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// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// -----------------------------------------------------------------------------
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// File: numbers.h
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// -----------------------------------------------------------------------------
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//
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// This package contains functions for converting strings to numbers. For
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// converting numbers to strings, use `StrCat()` or `StrAppend()` in str_cat.h,
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// which automatically detect and convert most number values appropriately.
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#ifndef ABSL_STRINGS_NUMBERS_H_
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#define ABSL_STRINGS_NUMBERS_H_
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#include <cstddef>
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#include <cstdlib>
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#include <cstring>
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#include <ctime>
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#include <limits>
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#include <string>
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#include <type_traits>
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#include "absl/base/macros.h"
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#include "absl/base/port.h"
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#include "absl/numeric/int128.h"
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#include "absl/strings/string_view.h"
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namespace absl {
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inline namespace lts_2018_12_18 {
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// SimpleAtoi()
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//
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// Converts the given string into an integer value, returning `true` if
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// successful. The string must reflect a base-10 integer (optionally followed or
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// preceded by ASCII whitespace) whose value falls within the range of the
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// integer type.
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template <typename int_type>
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ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view s, int_type* out);
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// SimpleAtof()
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//
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// Converts the given string (optionally followed or preceded by ASCII
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// whitespace) into a float, which may be rounded on overflow or underflow.
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// See http://en.cppreference.com/w/c/string/byte/strtof for details about the
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// allowed formats for `str`.
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ABSL_MUST_USE_RESULT bool SimpleAtof(absl::string_view str, float* value);
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// SimpleAtod()
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//
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// Converts the given string (optionally followed or preceded by ASCII
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// whitespace) into a double, which may be rounded on overflow or underflow.
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// See http://en.cppreference.com/w/c/string/byte/strtof for details about the
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// allowed formats for `str`.
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ABSL_MUST_USE_RESULT bool SimpleAtod(absl::string_view str, double* value);
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// SimpleAtob()
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//
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// Converts the given string into a boolean, returning `true` if successful.
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// The following case-insensitive strings are interpreted as boolean `true`:
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// "true", "t", "yes", "y", "1". The following case-insensitive strings
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// are interpreted as boolean `false`: "false", "f", "no", "n", "0".
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ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* value);
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} // inline namespace lts_2018_12_18
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} // namespace absl
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// End of public API. Implementation details follow.
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namespace absl {
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inline namespace lts_2018_12_18 {
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namespace numbers_internal {
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// safe_strto?() functions for implementing SimpleAtoi()
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bool safe_strto32_base(absl::string_view text, int32_t* value, int base);
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bool safe_strto64_base(absl::string_view text, int64_t* value, int base);
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bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base);
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bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base);
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static const int kFastToBufferSize = 32;
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static const int kSixDigitsToBufferSize = 16;
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// Helper function for fast formatting of floating-point values.
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// The result is the same as printf's "%g", a.k.a. "%.6g"; that is, six
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// significant digits are returned, trailing zeros are removed, and numbers
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// outside the range 0.0001-999999 are output using scientific notation
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// (1.23456e+06). This routine is heavily optimized.
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// Required buffer size is `kSixDigitsToBufferSize`.
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size_t SixDigitsToBuffer(double d, char* buffer);
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// These functions are intended for speed. All functions take an output buffer
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// as an argument and return a pointer to the last byte they wrote, which is the
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// terminating '\0'. At most `kFastToBufferSize` bytes are written.
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char* FastIntToBuffer(int32_t, char*);
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char* FastIntToBuffer(uint32_t, char*);
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char* FastIntToBuffer(int64_t, char*);
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char* FastIntToBuffer(uint64_t, char*);
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// For enums and integer types that are not an exact match for the types above,
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// use templates to call the appropriate one of the four overloads above.
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template <typename int_type>
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char* FastIntToBuffer(int_type i, char* buffer) {
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static_assert(sizeof(i) <= 64 / 8,
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"FastIntToBuffer works only with 64-bit-or-less integers.");
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// TODO(jorg): This signed-ness check is used because it works correctly
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// with enums, and it also serves to check that int_type is not a pointer.
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// If one day something like std::is_signed<enum E> works, switch to it.
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if (static_cast<int_type>(1) - 2 < 0) { // Signed
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if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
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return FastIntToBuffer(static_cast<int64_t>(i), buffer);
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} else { // 32-bit or less
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return FastIntToBuffer(static_cast<int32_t>(i), buffer);
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}
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} else { // Unsigned
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if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
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return FastIntToBuffer(static_cast<uint64_t>(i), buffer);
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} else { // 32-bit or less
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return FastIntToBuffer(static_cast<uint32_t>(i), buffer);
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}
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}
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}
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// Implementation of SimpleAtoi, generalized to support arbitrary base (used
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// with base different from 10 elsewhere in Abseil implementation).
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template <typename int_type>
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ABSL_MUST_USE_RESULT bool safe_strtoi_base(absl::string_view s, int_type* out,
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int base) {
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static_assert(sizeof(*out) == 4 || sizeof(*out) == 8,
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"SimpleAtoi works only with 32-bit or 64-bit integers.");
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static_assert(!std::is_floating_point<int_type>::value,
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"Use SimpleAtof or SimpleAtod instead.");
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bool parsed;
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// TODO(jorg): This signed-ness check is used because it works correctly
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// with enums, and it also serves to check that int_type is not a pointer.
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// If one day something like std::is_signed<enum E> works, switch to it.
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if (static_cast<int_type>(1) - 2 < 0) { // Signed
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if (sizeof(*out) == 64 / 8) { // 64-bit
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int64_t val;
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parsed = numbers_internal::safe_strto64_base(s, &val, base);
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*out = static_cast<int_type>(val);
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} else { // 32-bit
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int32_t val;
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parsed = numbers_internal::safe_strto32_base(s, &val, base);
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*out = static_cast<int_type>(val);
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}
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} else { // Unsigned
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if (sizeof(*out) == 64 / 8) { // 64-bit
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uint64_t val;
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parsed = numbers_internal::safe_strtou64_base(s, &val, base);
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*out = static_cast<int_type>(val);
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} else { // 32-bit
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uint32_t val;
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parsed = numbers_internal::safe_strtou32_base(s, &val, base);
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*out = static_cast<int_type>(val);
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}
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}
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return parsed;
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}
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} // namespace numbers_internal
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// SimpleAtoi()
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//
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// Converts a string to an integer, using `safe_strto?()` functions for actual
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// parsing, returning `true` if successful. The `safe_strto?()` functions apply
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// strict checking; the string must be a base-10 integer, optionally followed or
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// preceded by ASCII whitespace, with a value in the range of the corresponding
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// integer type.
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template <typename int_type>
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ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view s, int_type* out) {
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return numbers_internal::safe_strtoi_base(s, out, 10);
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}
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} // inline namespace lts_2018_12_18
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} // namespace absl
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#endif // ABSL_STRINGS_NUMBERS_H_
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