gstreamer/sys/shm/shmpipe.h

/* GStreamer
 * Copyright (C) <2009> Collabora Ltd
 *  @author: Olivier Crete <olivier.crete@collabora.co.uk
 * Copyright (C) <2009> Nokia Inc
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/*
 * None of this code is thread safe, if you want to use it in a multi-threaded
 * context, please protect it with a mutex.
 *
 * First, create a writer with sp_writer_create()
 * And selectes() on the socket from sp_get_fd()
 * If the socket is closed or there are errors from any function, the app
 * should call sp_close() and assume the writer is dead
 * The server calls sp_writer_accept_client() when there is something to read
 * from the server fd
 * It then needs to select() on the socket from sp_writer_get_client_fd()
 * If it gets an error on that socket, it call sp_writer_close_client().
 * If there is something to read, it calls sp_writer_recv().
 *
 * The writer allocates buffers with sp_writer_alloc_block(),
 * writes something in the buffer (retrieved with sp_writer_block_get_buf(),
 * then calls  sp_writer_send_buf() to send the buffer or a subsection to
 * the other side. When it is done with the block, it calls
 * sp_writer_free_block().
 * If alloc fails, then the server must wait for events from the clients before
 * trying again.
 *
 *
 * The clients connect with sp_client_open()
 * And select() on the fd from sp_get_fd() until there is something to read.
 * Then they must read using sp_client_recv() which will return > 0 if there
 * is a valid buffer (which is read only). It will return 0 if it is an internal
 * message and <0 if there was an error. If there was an error, one must close
 * it with sp_close(). If was valid buffer was received, the client must release
 * it with sp_client_recv_finish() when it is done reading from it.
 */


#ifndef __SHMPIPE_H__
#define __SHMPIPE_H__

#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


#ifdef __cplusplus
extern "C" {
#endif

typedef struct _ShmClient ShmClient;
typedef struct _ShmPipe ShmPipe;
typedef struct _ShmBlock ShmBlock;

ShmPipe *sp_writer_create (const char *path, size_t size, mode_t perms);
const char *sp_writer_get_path (ShmPipe *pipe);
void sp_close (ShmPipe * self);

int sp_writer_setperms_shm (ShmPipe * self, mode_t perms);
int sp_writer_resize (ShmPipe * self, size_t size);

int sp_get_fd (ShmPipe * self);
int sp_writer_get_client_fd (ShmClient * client);

ShmBlock *sp_writer_alloc_block (ShmPipe * self, size_t size);
void sp_writer_free_block (ShmBlock *block);
int sp_writer_send_buf (ShmPipe * self, char *buf, size_t size);
char *sp_writer_block_get_buf (ShmBlock *block);

ShmClient * sp_writer_accept_client (ShmPipe * self);
void sp_writer_close_client (ShmPipe *self, ShmClient * client);
int sp_writer_recv (ShmPipe * self, ShmClient * client);

int sp_writer_pending_writes (ShmPipe * self);

ShmPipe *sp_client_open (const char *path);
long int sp_client_recv (ShmPipe * self, char **buf);
int sp_client_recv_finish (ShmPipe * self, char *buf);

#ifdef __cplusplus
}
#endif

#endif /* __SHMPIPE_H__ */