file_body.hpp

//
// Copyright (c) 2013-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#ifndef BEAST_EXAMPLE_FILE_BODY_H_INCLUDED
#define BEAST_EXAMPLE_FILE_BODY_H_INCLUDED

#include <beast/core/error.hpp>
#include <beast/http/message.hpp>
#include <boost/asio/buffer.hpp>
#include <boost/assert.hpp>
#include <boost/filesystem.hpp>
#include <cstdint>
#include <cstdio>

namespace beast {
namespace http {

struct file_body {
  using value_type = std::string;

  class writer {
    std::uint64_t size_ = 0;
    std::uint64_t offset_ = 0;
    std::string const &path_;
    FILE *file_ = nullptr;
    char buf_[4096];
    std::size_t buf_len_;

  public:
    writer(writer const &) = delete;
    writer &operator=(writer const &) = delete;

    template <bool isRequest, class Fields>
    writer(message<isRequest, file_body, Fields> const &m) noexcept
        : path_(m.body) {
    }

    ~writer() {
      if (file_)
        fclose(file_);
    }

    void init(error_code &ec) noexcept {
      file_ = fopen(path_.c_str(), "rb");
      if (!file_)
        ec = error_code{errno, system_category()};
      else
        size_ = boost::filesystem::file_size(path_);
    }

    std::uint64_t content_length() const noexcept {
      return size_;
    }

    template <class WriteFunction>
    bool write(error_code &ec, WriteFunction &&wf) noexcept {
      if (size_ - offset_ < sizeof(buf_))
        buf_len_ = static_cast<std::size_t>(size_ - offset_);
      else
        buf_len_ = sizeof(buf_);
      auto const nread = fread(buf_, 1, sizeof(buf_), file_);
      if (ferror(file_)) {
        ec = error_code(errno, system_category());
        return true;
      }
      BOOST_ASSERT(nread != 0);
      offset_ += nread;
      wf(boost::asio::buffer(buf_, nread));
      return offset_ >= size_;
    }
  };
};

} // namespace http
} // namespace beast

#endif