1 // Copyright 2020 The Pigweed Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not 4 // use this file except in compliance with the License. You may obtain a copy of 5 // the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 12 // License for the specific language governing permissions and limitations under 13 // the License. 14 #pragma once 15 16 #include <cstring> 17 #include <limits> 18 #include <string> 19 20 #if __cplusplus >= 201703L 21 #include <string_view> 22 #endif // __cplusplus >= 201703L 23 24 namespace pw { 25 namespace kvs { 26 27 // Key is a simplified string_view used for KVS. This helps KVS work on 28 // platforms without C++17. 29 class Key { 30 public: 31 using value_type = const char; 32 33 // Constructors Key()34 constexpr Key() : str_{nullptr}, length_{0} {} 35 constexpr Key(const Key&) = default; Key(const char * str)36 constexpr Key(const char* str) : str_{str}, length_{CStringLength(str)} {} Key(const char * str,size_t len)37 constexpr Key(const char* str, size_t len) : str_{str}, length_{len} {} Key(const std::string & str)38 Key(const std::string& str) : str_{str.data()}, length_{str.length()} {} 39 40 #if __cplusplus >= 201703L Key(const std::string_view & str)41 constexpr Key(const std::string_view& str) 42 : str_{str.data()}, length_{str.length()} {} string_view()43 operator std::string_view() { return std::string_view{str_, length_}; } 44 #endif // __cplusplus >= 201703L 45 46 // Assignment 47 constexpr Key& operator=(const Key&) = default; 48 49 // Traits size()50 constexpr size_t size() const { return length_; } length()51 constexpr size_t length() const { return length_; } empty()52 constexpr bool empty() const { return length_ == 0; } 53 54 // Access 55 constexpr const char& operator[](size_t pos) const { return str_[pos]; } at(size_t pos)56 constexpr const char& at(size_t pos) const { return str_[pos]; } front()57 constexpr const char& front() const { return str_[0]; } back()58 constexpr const char& back() const { return str_[length_ - 1]; } data()59 constexpr const char* data() const { return str_; } 60 61 // Iterator begin()62 constexpr const char* begin() const { return str_; } end()63 constexpr const char* end() const { return str_ + length_; } 64 65 // Equal 66 constexpr bool operator==(Key other_key) const { 67 return length() == other_key.length() && 68 std::memcmp(str_, other_key.data(), length()) == 0; 69 } 70 71 // Not Equal 72 constexpr bool operator!=(Key other_key) const { 73 return length() != other_key.length() || 74 std::memcmp(str_, other_key.data(), length()) != 0; 75 } 76 77 private: 78 // constexpr version of strlen CStringLength(const char * str)79 static constexpr size_t CStringLength(const char* str) { 80 size_t length = 0; 81 while (str[length] != '\0') { 82 length += 1; 83 } 84 return length; 85 } 86 87 const char* str_; 88 size_t length_; 89 }; 90 91 } // namespace kvs 92 } // namespace pw 93