libc/src/__support/char_vector.h

   1 //===-- Standalone implementation of a char vector --------------*- 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_CHARVECTOR_H
  10 #define LLVM_LIBC_SRC___SUPPORT_CHARVECTOR_H
  11
  12 #include "hdr/func/free.h"
  13 #include "hdr/func/malloc.h"
  14 #include "hdr/func/realloc.h"
  15 #include "src/__support/common.h" // LIBC_INLINE
  16 #include "src/__support/macros/config.h"
  17
  18 #include <stddef.h> // size_t
  19
  20 namespace LIBC_NAMESPACE_DECL {
  21
  22 // This is very simple alternate of the std::string class. There is no
  23 // bounds check performed in any of the methods. The callers are expected to
  24 // do the checks before invoking the methods.
  25 //
  26 // This class will be extended as needed in future.
  27
  28 class CharVector {
  29   static constexpr size_t INIT_BUFF_SIZE = 64;
  30   char local_buffer[INIT_BUFF_SIZE];
  31   char *cur_str = local_buffer;
  32   size_t cur_buff_size = INIT_BUFF_SIZE;
  33   size_t index = 0;
  34
  35 public:
  36   CharVector() = default;
  37   LIBC_INLINE ~CharVector() {
  38     if (cur_str != local_buffer)
  39       free(cur_str);
  40   }
  41
  42   // append returns true on success and false on allocation failure.
  43   LIBC_INLINE bool append(char new_char) {
  44     // Subtract 1 for index starting at 0 and another for the null terminator.
  45     if (index >= cur_buff_size - 2) {
  46       // If the new character would cause the string to be longer than the
  47       // buffer's size, attempt to allocate a new buffer.
  48       cur_buff_size = cur_buff_size * 2;
  49       if (cur_str == local_buffer) {
  50         char *new_str;
  51         new_str = reinterpret_cast<char *>(malloc(cur_buff_size));
  52         if (new_str == nullptr) {
  53           return false;
  54         }
  55         // TODO: replace with inline memcpy
  56         for (size_t i = 0; i < index; ++i)
  57           new_str[i] = cur_str[i];
  58         cur_str = new_str;
  59       } else {
  60         cur_str = reinterpret_cast<char *>(realloc(cur_str, cur_buff_size));
  61         if (cur_str == nullptr) {
  62           return false;
  63         }
  64       }
  65     }
  66     cur_str[index] = new_char;
  67     ++index;
  68     return true;
  69   }
  70
  71   LIBC_INLINE char *c_str() {
  72     cur_str[index] = '\0';
  73     return cur_str;
  74   }
  75
  76   LIBC_INLINE size_t length() { return index; }
  77 };
  78
  79 } // namespace LIBC_NAMESPACE_DECL
  80
  81 #endif // LLVM_LIBC_SRC___SUPPORT_CHARVECTOR_H