mapped_file.hh

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/*
 * libkeepass - KeePass key database importer/exporter
 * Copyright (C) 2014 Christian Kindahl
 * Copyright (C) 2024 Dominik Krümpelmann
 *
 * This program 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include <cstddef>
#include <streambuf>
#include <string>
 
#include "libkeepass/export.hh"
 
namespace keepass {
namespace detail {
 
class LIBKEEPASS_API MappedFile final {
public:
 
  explicit MappedFile(const std::string& path);
 
  ~MappedFile();
 
  MappedFile(const MappedFile&) = delete;
  MappedFile& operator=(const MappedFile&) = delete;
  MappedFile(MappedFile&&) = delete;
  MappedFile& operator=(MappedFile&&) = delete;
 
  const char* data() const noexcept { return static_cast<const char*>(data_); }
 
  std::size_t size() const noexcept { return size_; }
 
  bool empty() const noexcept { return size_ == 0; }
 
private:
  void* data_ = nullptr;
  std::size_t size_ = 0;
 
#ifdef _WIN32
  void* file_ = nullptr;
  void* mapping_ = nullptr;
#else
  int fd_ = -1;
#endif
};
 
class LIBKEEPASS_API mapped_istreambuf final : public std::streambuf {
public:
  mapped_istreambuf(const char* data, std::size_t size) {
    // A zero-sized mapping has no valid pointer; use a static sentinel so the
    // stream buffer never forms a pointer past nullptr.
    static char empty = 0;
    begin_ = size == 0 ? &empty : const_cast<char*>(data);
    end_ = begin_ + size;
    setg(begin_, begin_, end_);
  }
 
protected:
  std::streampos seekoff(std::streamoff off, std::ios_base::seekdir way,
                         std::ios_base::openmode which) override;
  std::streampos seekpos(std::streampos sp, std::ios_base::openmode which) override;
 
private:
  char* begin_ = nullptr;
  char* end_ = nullptr;
};
 
} // namespace detail
} // namespace keepass