downloader.hpp

// Copyright 2017 MongoDB Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#pragma once
 
#include <cstddef>
#include <cstdint>
#include <memory>
 
#include <bsoncxx/document/value.hpp>
#include <bsoncxx/document/view.hpp>
#include <bsoncxx/stdx/optional.hpp>
#include <bsoncxx/types/bson_value/view.hpp>
#include <mongocxx/cursor.hpp>
#include <mongocxx/stdx.hpp>
 
#include <mongocxx/config/prelude.hpp>
 
namespace mongocxx {
MONGOCXX_INLINE_NAMESPACE_BEGIN
namespace gridfs {
 
struct chunks_and_bytes_offset {
    std::int32_t chunks_offset = 0;
    std::int32_t bytes_offset = 0;
};
 
class MONGOCXX_API downloader {
   public:
    downloader() noexcept;
 
    downloader(downloader&&) noexcept;
 
    downloader& operator=(downloader&&) noexcept;
 
    downloader(const downloader&) = delete;
 
    downloader& operator=(const downloader&) = delete;
 
    ~downloader();
 
    explicit operator bool() const noexcept;
 
    std::size_t read(std::uint8_t* buffer, std::size_t length);
 
    void close();
 
    std::int32_t chunk_size() const;
 
    std::int64_t file_length() const;
 
    bsoncxx::document::view files_document() const;
 
   private:
    friend class bucket;
 
    //
    // Constructs a new downloader stream.
    //
    // @param chunks
    //   The cursor to read the chunks of the file from. It must have a value if the length of the
    //   file is non-zero.
    //
    // @param start
    //   The offset from which to start reading the chunks of the file.
    //
    // @param chunk_size
    //   The expected size of a chunk in bytes.
    //
    // @param file_len
    //   The expected size of the file in bytes.
    //
    // @param files_doc
    //   The files collection document of the file being downloaded.
    //
    MONGOCXX_PRIVATE downloader(stdx::optional<cursor> chunks,
                                chunks_and_bytes_offset start,
                                std::int32_t chunk_size,
                                std::int64_t file_len,
                                bsoncxx::document::value files_doc);
 
    MONGOCXX_PRIVATE void fetch_chunk();
 
    class MONGOCXX_PRIVATE impl;
 
    MONGOCXX_PRIVATE impl& _get_impl();
    MONGOCXX_PRIVATE const impl& _get_impl() const;
 
    std::unique_ptr<impl> _impl;
};
 
}  // namespace gridfs
MONGOCXX_INLINE_NAMESPACE_END
}  // namespace mongocxx