text: #ifndef TNT_STREAM_H_INCLUDED
  #define TNT_STREAM_H_INCLUDED
  
  /*
   * Redistribution and use in source and binary forms, with or
   * without modification, are permitted provided that the following
   * conditions are met:
   *
   * 1. Redistributions of source code must retain the above
   *    copyright notice, this list of conditions and the
   *    following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above
   *    copyright notice, this list of conditions and the following
   *    disclaimer in the documentation and/or other materials
   *    provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
   * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
   * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
   * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  /**
   * \file tnt_stream.h
   * \brief Basic stream object
   */
  
  #include <sys/types.h>
  #include <sys/uio.h>
  
  #include <tarantool/tnt_reply.h>
  #include <tarantool/tnt_request.h>
  
  /**
   * \brief Basic stream object
   * all function pointers are NULL, if operation is not supported
   */
  struct tnt_stream {
  	int alloc; /*!< Allocation mark */
  	ssize_t (*write)(struct tnt_stream *s, const char *buf, size_t size); /*!< write to buffer function */
  	ssize_t (*writev)(struct tnt_stream *s, struct iovec *iov, int count); /*!< writev function */
  	ssize_t (*write_request)(struct tnt_stream *s, struct tnt_request *r, uint64_t *sync); /*!< write request function */
  
  	ssize_t (*read)(struct tnt_stream *s, char *buf, size_t size); /*!< read from buffer function */
  	int (*read_reply)(struct tnt_stream *s, struct tnt_reply *r); /*!< read reply from buffer */
  
  	void (*free)(struct tnt_stream *s); /*!< free custom buffer types (destructor) */
  
  	void *data; /*!< subclass data */
  	uint32_t wrcnt; /*!< count of write operations */
  	uint64_t reqid; /*!< request id of current operation */
  };
  
  /**
   * \brief Base function for allocating stream. For internal use only.
   */
  struct tnt_stream *tnt_stream_init(struct tnt_stream *s);
  /**
   * \brief Base function for freeing stream. For internal use only.
   */
  void tnt_stream_free(struct tnt_stream *s);
  
  /**
   * \brief set reqid number. It's incremented at every request compilation.
   * default is 0
   */
  uint32_t tnt_stream_reqid(struct tnt_stream *s, uint32_t reqid);
  
  #endif /* TNT_STREAM_H_INCLUDED */
  