string_builder.hpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */
 
#ifndef STRING_BUILDER_HPP
#define STRING_BUILDER_HPP
 
#include <charconv>
 
class BaseStringBuilder {
public:
  using size_type = std::string_view::size_type;
 
  virtual ~BaseStringBuilder() = default;
 
  virtual void PutBuffer(std::span<const char> str) = 0;
 
  void Put(std::string_view str) { this->PutBuffer(str); }
 
  void PutUint8(uint8_t value);
  void PutSint8(int8_t value);
  void PutUint16LE(uint16_t value);
  void PutSint16LE(int16_t value);
  void PutUint32LE(uint32_t value);
  void PutSint32LE(int32_t value);
  void PutUint64LE(uint64_t value);
  void PutSint64LE(int64_t value);
 
  void PutChar(char c);
  void PutUtf8(char32_t c);
 
  template <class T>
  void PutIntegerBase(T value, int base)
  {
    std::array<char, 32> buf;
    auto result = std::to_chars(buf.data(), buf.data() + buf.size(), value, base);
    if (result.ec != std::errc{}) return;
    size_type len = result.ptr - buf.data();
    this->PutBuffer({buf.data(), len});
  }
};
 
class StringBuilder final : public BaseStringBuilder {
  std::string *dest;
public:
  StringBuilder(std::string &dest) : dest(&dest) {}
 
  [[nodiscard]] bool AnyBytesWritten() const noexcept { return !this->dest->empty(); }
  [[nodiscard]] size_type GetBytesWritten() const noexcept { return this->dest->size(); }
  [[nodiscard]] const std::string &GetWrittenData() const noexcept { return *dest; }
  [[nodiscard]] std::string &GetString() noexcept { return *dest; }
 
  void PutBuffer(std::span<const char> str) override;
 
  StringBuilder& operator+=(std::string_view str)
  {
    this->Put(str);
    return *this;
  }
 
  using back_insert_iterator = std::back_insert_iterator<std::string>;
  back_insert_iterator back_inserter()
  {
    return back_insert_iterator(*this->dest);
  }
};
 
#endif /* STRING_BUILDER_HPP */