libc/src/__support/CPP/string.h

   1 //===-- A simple implementation of the string class -------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC_SUPPORT_CPP_STRING_H
  10 #define LLVM_LIBC_SRC_SUPPORT_CPP_STRING_H
  11
  12 #include "src/__support/CPP/string_view.h"
  13 #include "src/__support/integer_to_string.h" // IntegerToString
  14 #include "src/string/memory_utils/memcpy_implementations.h"
  15 #include "src/string/memory_utils/memset_implementations.h"
  16 #include "src/string/string_utils.h" // string_length
  17
  18 #include <stddef.h> // size_t
  19 #include <stdlib.h> // malloc, free
  20
  21 namespace __llvm_libc {
  22 namespace cpp {
  23
  24 // This class mimics std::string but does not intend to be a full fledged
  25 // implementation. Most notably it does not provide support for character traits
  26 // nor custom allocator.
  27 class string {
  28 private:
  29   static constexpr char NULL_CHARACTER = '\0';
  30   static constexpr char *get_empty_string() {
  31     return const_cast<char *>(&NULL_CHARACTER);
  32   }
  33
  34   char *buffer_ = get_empty_string();
  35   size_t size_ = 0;
  36   size_t capacity_ = 0;
  37
  38   constexpr void reset_no_deallocate() {
  39     buffer_ = get_empty_string();
  40     size_ = 0;
  41     capacity_ = 0;
  42   }
  43
  44   void set_size_and_add_null_character(size_t size) {
  45     size_ = size;
  46     if (buffer_ != get_empty_string())
  47       buffer_[size_] = NULL_CHARACTER;
  48   }
  49
  50 public:
  51   LIBC_INLINE constexpr string() {}
  52   LIBC_INLINE string(const string &other) { this->operator+=(other); }
  53   LIBC_INLINE constexpr string(string &&other)
  54       : buffer_(other.buffer_), size_(other.size_), capacity_(other.capacity_) {
  55     other.reset_no_deallocate();
  56   }
  57   LIBC_INLINE string(const char *cstr, size_t count) {
  58     resize(count);
  59     inline_memcpy((void *)buffer_, (const void *)cstr, count);
  60   }
  61   LIBC_INLINE string(const char *cstr)
  62       : string(cstr, ::__llvm_libc::internal::string_length(cstr)) {}
  63   LIBC_INLINE string(size_t size_, char value) {
  64     resize(size_);
  65     inline_memset((void *)buffer_, value, size_);
  66   }
  67
  68   LIBC_INLINE string &operator=(const string &other) {
  69     resize(0);
  70     return (*this) += other;
  71   }
  72
  73   LIBC_INLINE string &operator=(string &&other) {
  74     buffer_ = other.buffer_;
  75     size_ = other.size_;
  76     capacity_ = other.capacity_;
  77     other.reset_no_deallocate();
  78     return *this;
  79   }
  80
  81   LIBC_INLINE ~string() {
  82     if (buffer_ != get_empty_string())
  83       ::free(buffer_);
  84   }
  85
  86   LIBC_INLINE constexpr size_t capacity() const { return capacity_; }
  87   LIBC_INLINE constexpr size_t size() const { return size_; }
  88   LIBC_INLINE constexpr bool empty() const { return size_ == 0; }
  89
  90   LIBC_INLINE constexpr const char *data() const { return buffer_; }
  91   LIBC_INLINE char *data() { return buffer_; }
  92
  93   LIBC_INLINE constexpr const char *begin() const { return data(); }
  94   LIBC_INLINE char *begin() { return data(); }
  95
  96   LIBC_INLINE constexpr const char *end() const { return data() + size_; }
  97   LIBC_INLINE char *end() { return data() + size_; }
  98
  99   LIBC_INLINE constexpr const char &front() const { return data()[0]; }
 100   LIBC_INLINE char &front() { return data()[0]; }
 101
 102   LIBC_INLINE constexpr const char &back() const { return data()[size_ - 1]; }
 103   LIBC_INLINE char &back() { return data()[size_ - 1]; }
 104
 105   LIBC_INLINE constexpr const char &operator[](size_t index) const {
 106     return data()[index];
 107   }
 108   LIBC_INLINE char &operator[](size_t index) { return data()[index]; }
 109
 110   LIBC_INLINE const char *c_str() const { return data(); }
 111
 112   LIBC_INLINE operator string_view() const {
 113     return string_view(buffer_, size_);
 114   }
 115
 116   LIBC_INLINE void reserve(size_t new_capacity) {
 117     ++new_capacity; // Accounting for the terminating '\0'
 118     if (new_capacity <= capacity_)
 119       return;
 120     // We extend the capacity to amortize buffer_ reallocations.
 121     // We choose to augment the value by 11 / 8, this is about +40% and division
 122     // by 8 is cheap. We guard the extension so the operation doesn't overflow.
 123     if (new_capacity < SIZE_MAX / 11)
 124       new_capacity = new_capacity * 11 / 8;
 125     if (void *Ptr = ::realloc(buffer_ == get_empty_string() ? nullptr : buffer_,
 126                               new_capacity)) {
 127       buffer_ = static_cast<char *>(Ptr);
 128       capacity_ = new_capacity;
 129     } else {
 130       __builtin_unreachable(); // out of memory
 131     }
 132   }
 133
 134   LIBC_INLINE void resize(size_t size) {
 135     if (size > capacity_) {
 136       reserve(size);
 137       const size_t size_extension = size - size_;
 138       inline_memset(data() + size_, '\0', size_extension);
 139     }
 140     set_size_and_add_null_character(size);
 141   }
 142
 143   LIBC_INLINE string &operator+=(const string &rhs) {
 144     const size_t new_size = size_ + rhs.size();
 145     reserve(new_size);
 146     inline_memcpy(buffer_ + size_, rhs.data(), rhs.size());
 147     set_size_and_add_null_character(new_size);
 148     return *this;
 149   }
 150
 151   LIBC_INLINE string &operator+=(const char c) {
 152     const size_t new_size = size_ + 1;
 153     reserve(new_size);
 154     buffer_[size_] = c;
 155     set_size_and_add_null_character(new_size);
 156     return *this;
 157   }
 158 };
 159
 160 LIBC_INLINE bool operator==(const string &lhs, const string &rhs) {
 161   return string_view(lhs) == string_view(rhs);
 162 }
 163 LIBC_INLINE bool operator!=(const string &lhs, const string &rhs) {
 164   return string_view(lhs) != string_view(rhs);
 165 }
 166 LIBC_INLINE bool operator<(const string &lhs, const string &rhs) {
 167   return string_view(lhs) < string_view(rhs);
 168 }
 169 LIBC_INLINE bool operator<=(const string &lhs, const string &rhs) {
 170   return string_view(lhs) <= string_view(rhs);
 171 }
 172 LIBC_INLINE bool operator>(const string &lhs, const string &rhs) {
 173   return string_view(lhs) > string_view(rhs);
 174 }
 175 LIBC_INLINE bool operator>=(const string &lhs, const string &rhs) {
 176   return string_view(lhs) >= string_view(rhs);
 177 }
 178
 179 LIBC_INLINE string operator+(const string &lhs, const string &rhs) {
 180   string Tmp(lhs);
 181   return Tmp += rhs;
 182 }
 183 LIBC_INLINE string operator+(const string &lhs, const char *rhs) {
 184   return lhs + string(rhs);
 185 }
 186 LIBC_INLINE string operator+(const char *lhs, const string &rhs) {
 187   return string(lhs) + rhs;
 188 }
 189
 190 namespace internal {
 191 template <typename T> string to_dec_string(T value) {
 192   char dec_buf[IntegerToString::dec_bufsize<T>()];
 193   auto maybe_string_view = IntegerToString::dec(value, dec_buf);
 194   const auto &string_view = *maybe_string_view;
 195   return string(string_view.data(), string_view.size());
 196 }
 197 } // namespace internal
 198
 199 LIBC_INLINE string to_string(int value) {
 200   return internal::to_dec_string<int>(value);
 201 }
 202 LIBC_INLINE string to_string(long value) {
 203   return internal::to_dec_string<long>(value);
 204 }
 205 LIBC_INLINE string to_string(long long value) {
 206   return internal::to_dec_string<long long>(value);
 207 }
 208 LIBC_INLINE string to_string(unsigned value) {
 209   return internal::to_dec_string<unsigned>(value);
 210 }
 211 LIBC_INLINE string to_string(unsigned long value) {
 212   return internal::to_dec_string<unsigned long>(value);
 213 }
 214 LIBC_INLINE string to_string(unsigned long long value) {
 215   return internal::to_dec_string<unsigned long long>(value);
 216 }
 217
 218 // TODO: Support floating point
 219 // LIBC_INLINE string to_string(float value);
 220 // LIBC_INLINE string to_string(double value);
 221 // LIBC_INLINE string to_string(long double value);
 222
 223 } // namespace cpp
 224 } // namespace __llvm_libc
 225
 226 #endif // LLVM_LIBC_SRC_SUPPORT_CPP_STRING_H