117 lines
4.6 KiB
C++
117 lines
4.6 KiB
C++
/*
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* Copyright 2017 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef RTC_BASE_STRING_TO_NUMBER_H_
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#define RTC_BASE_STRING_TO_NUMBER_H_
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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/types/optional.h"
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namespace rtc {
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// This file declares a family of functions to parse integers from strings.
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// The standard C library functions either fail to indicate errors (atoi, etc.)
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// or are a hassle to work with (strtol, sscanf, etc.). The standard C++ library
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// functions (std::stoi, etc.) indicate errors by throwing exceptions, which
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// are disabled in WebRTC.
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//
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// Integers are parsed using one of the following functions:
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// absl::optional<int-type> StringToNumber(const char* str, int base = 10);
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// absl::optional<int-type> StringToNumber(const std::string& str,
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// int base = 10);
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//
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// These functions parse a value from the beginning of a string into one of the
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// fundamental integer types, or returns an empty Optional if parsing
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// failed. Values outside of the range supported by the type will be
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// rejected. The strings must begin with a digit or a minus sign. No leading
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// space nor trailing contents are allowed.
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// By setting base to 0, one of octal, decimal or hexadecimal will be
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// detected from the string's prefix (0, nothing or 0x, respectively).
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// If non-zero, base can be set to a value between 2 and 36 inclusively.
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//
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// If desired, this interface could be extended with support for floating-point
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// types.
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namespace string_to_number_internal {
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// These must be (unsigned) long long, to match the signature of strto(u)ll.
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using unsigned_type = unsigned long long; // NOLINT(runtime/int)
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using signed_type = long long; // NOLINT(runtime/int)
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absl::optional<signed_type> ParseSigned(const char* str, int base);
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absl::optional<unsigned_type> ParseUnsigned(const char* str, int base);
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template <typename T>
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absl::optional<T> ParseFloatingPoint(const char* str);
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} // namespace string_to_number_internal
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template <typename T>
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typename std::enable_if<std::is_integral<T>::value && std::is_signed<T>::value,
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absl::optional<T>>::type
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StringToNumber(const char* str, int base = 10) {
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using string_to_number_internal::signed_type;
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static_assert(
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std::numeric_limits<T>::max() <=
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std::numeric_limits<signed_type>::max() &&
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std::numeric_limits<T>::lowest() >=
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std::numeric_limits<signed_type>::lowest(),
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"StringToNumber only supports signed integers as large as long long int");
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absl::optional<signed_type> value =
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string_to_number_internal::ParseSigned(str, base);
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if (value && *value >= std::numeric_limits<T>::lowest() &&
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*value <= std::numeric_limits<T>::max()) {
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return static_cast<T>(*value);
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}
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return absl::nullopt;
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}
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template <typename T>
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typename std::enable_if<std::is_integral<T>::value &&
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std::is_unsigned<T>::value,
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absl::optional<T>>::type
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StringToNumber(const char* str, int base = 10) {
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using string_to_number_internal::unsigned_type;
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static_assert(std::numeric_limits<T>::max() <=
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std::numeric_limits<unsigned_type>::max(),
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"StringToNumber only supports unsigned integers as large as "
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"unsigned long long int");
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absl::optional<unsigned_type> value =
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string_to_number_internal::ParseUnsigned(str, base);
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if (value && *value <= std::numeric_limits<T>::max()) {
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return static_cast<T>(*value);
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}
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return absl::nullopt;
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}
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template <typename T>
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typename std::enable_if<std::is_floating_point<T>::value,
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absl::optional<T>>::type
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StringToNumber(const char* str, int base = 10) {
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static_assert(
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std::numeric_limits<T>::max() <= std::numeric_limits<long double>::max(),
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"StringToNumber only supports floating-point numbers as large "
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"as long double");
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return string_to_number_internal::ParseFloatingPoint<T>(str);
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}
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// The std::string overloads only exists if there is a matching const char*
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// version.
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template <typename T>
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auto StringToNumber(const std::string& str, int base = 10)
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-> decltype(StringToNumber<T>(str.c_str(), base)) {
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return StringToNumber<T>(str.c_str(), base);
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}
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} // namespace rtc
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#endif // RTC_BASE_STRING_TO_NUMBER_H_
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