1 /* 2 * Copyright 2017 The WebRTC Project Authors. All rights reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef RTC_BASE_STRING_TO_NUMBER_H_ 12 #define RTC_BASE_STRING_TO_NUMBER_H_ 13 14 #include <limits> 15 #include <string> 16 #include <type_traits> 17 18 #include "absl/strings/string_view.h" 19 #include "absl/types/optional.h" 20 21 namespace rtc { 22 23 // This file declares a family of functions to parse integers from strings. 24 // The standard C library functions either fail to indicate errors (atoi, etc.) 25 // or are a hassle to work with (strtol, sscanf, etc.). The standard C++ library 26 // functions (std::stoi, etc.) indicate errors by throwing exceptions, which 27 // are disabled in WebRTC. 28 // 29 // Integers are parsed using: 30 // absl::optional<int-type> StringToNumber(absl::string_view str, 31 // int base = 10); 32 // 33 // These functions parse a value from the beginning of a string into one of the 34 // fundamental integer types, or returns an empty Optional if parsing 35 // failed. Values outside of the range supported by the type will be 36 // rejected. The strings must begin with a digit or a minus sign. No leading 37 // space nor trailing contents are allowed. 38 // By setting base to 0, one of octal, decimal or hexadecimal will be 39 // detected from the string's prefix (0, nothing or 0x, respectively). 40 // If non-zero, base can be set to a value between 2 and 36 inclusively. 41 42 namespace string_to_number_internal { 43 // These must be (unsigned) long long, to match the signature of strto(u)ll. 44 using unsigned_type = unsigned long long; // NOLINT(runtime/int) 45 using signed_type = long long; // NOLINT(runtime/int) 46 47 absl::optional<signed_type> ParseSigned(absl::string_view str, int base); 48 absl::optional<unsigned_type> ParseUnsigned(absl::string_view str, int base); 49 50 template <typename T> 51 absl::optional<T> ParseFloatingPoint(absl::string_view str); 52 } // namespace string_to_number_internal 53 54 template <typename T> 55 typename std::enable_if<std::is_integral<T>::value && std::is_signed<T>::value, 56 absl::optional<T>>::type 57 StringToNumber(absl::string_view str, int base = 10) { 58 using string_to_number_internal::signed_type; 59 static_assert( 60 std::numeric_limits<T>::max() <= 61 std::numeric_limits<signed_type>::max() && 62 std::numeric_limits<T>::lowest() >= 63 std::numeric_limits<signed_type>::lowest(), 64 "StringToNumber only supports signed integers as large as long long int"); 65 absl::optional<signed_type> value = 66 string_to_number_internal::ParseSigned(str, base); 67 if (value && *value >= std::numeric_limits<T>::lowest() && 68 *value <= std::numeric_limits<T>::max()) { 69 return static_cast<T>(*value); 70 } 71 return absl::nullopt; 72 } 73 74 template <typename T> 75 typename std::enable_if<std::is_integral<T>::value && 76 std::is_unsigned<T>::value, 77 absl::optional<T>>::type 78 StringToNumber(absl::string_view str, int base = 10) { 79 using string_to_number_internal::unsigned_type; 80 static_assert(std::numeric_limits<T>::max() <= 81 std::numeric_limits<unsigned_type>::max(), 82 "StringToNumber only supports unsigned integers as large as " 83 "unsigned long long int"); 84 absl::optional<unsigned_type> value = 85 string_to_number_internal::ParseUnsigned(str, base); 86 if (value && *value <= std::numeric_limits<T>::max()) { 87 return static_cast<T>(*value); 88 } 89 return absl::nullopt; 90 } 91 92 template <typename T> 93 typename std::enable_if<std::is_floating_point<T>::value, 94 absl::optional<T>>::type 95 StringToNumber(absl::string_view str, int base = 10) { 96 static_assert( 97 std::numeric_limits<T>::max() <= std::numeric_limits<long double>::max(), 98 "StringToNumber only supports floating-point numbers as large " 99 "as long double"); 100 return string_to_number_internal::ParseFloatingPoint<T>(str); 101 } 102 103 } // namespace rtc 104 105 #endif // RTC_BASE_STRING_TO_NUMBER_H_ 106