dvb_ringbuffer.h

dvb的系统程序。基于lunix系统.经过改进更新

/*
 *
 * dvb_ringbuffer.h: ring buffer implementation for the dvb driver
 *
 * Copyright (C) 2003 Oliver Endriss 
 * 
 * based on code originally found in av7110.c:
 * Copyright (C) 1999-2002 Ralph Metzler & Marcus Metzler
 *                         for convergence integrated media GmbH
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#ifndef _DVB_RINGBUFFER_H_
#define _DVB_RINGBUFFER_H_

#include <linux/spinlock.h>
#include <linux/wait.h>

struct dvb_ringbuffer {
        u8               *data;
        ssize_t           size;
        ssize_t           pread;
        ssize_t           pwrite;

        wait_queue_head_t queue;
        spinlock_t        lock;
};


/*
** Notes:
** ------
** (1) For performance reasons read and write routines don't check buffer sizes
**     and/or number of bytes free/available. This has to be done before these
**     routines are called. For example:
**
**     *** write <buflen> bytes ***
**     free = dvb_ringbuffer_free(rbuf);
**     if (free >= buflen) 
**         count = dvb_ringbuffer_write(rbuf, buffer, buflen, 0);
**     else
**         ...
**
**     *** read min. 1000, max. <bufsize> bytes ***
**     avail = dvb_ringbuffer_avail(rbuf);
**     if (avail >= 1000)
**         count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize), 0);
**     else
**         ...
**
** (2) If there is exactly one reader and one writer, there is no need 
**     to lock read or write operations.
**     Two or more readers must be locked against each other.
**     Flushing the buffer counts as a read operation.
**     Two or more writers must be locked against each other.
*/

/* initialize ring buffer, lock and queue */
extern void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len);

/* test whether buffer is empty */
extern int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf);

/* return the number of free bytes in the buffer */
extern ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf);

/* return the number of bytes waiting in the buffer */
extern ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf);


/* read routines & macros */
/* ---------------------- */
/* flush buffer */
extern void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf);

/* flush buffer protected by spinlock and wake-up waiting task(s) */
extern void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf);

/* peek at byte <offs> in the buffer */
#define DVB_RINGBUFFER_PEEK(rbuf,offs)	\
			(rbuf)->data[((rbuf)->pread+(offs))%(rbuf)->size]

/* advance read ptr by <num> bytes */
#define DVB_RINGBUFFER_SKIP(rbuf,num)	\
			(rbuf)->pread=((rbuf)->pread+(num))%(rbuf)->size
 
/*
** read <len> bytes from ring buffer into <buf> 
** <usermem> specifies whether <buf> resides in user space
** returns number of bytes transferred or -EFAULT
*/
extern ssize_t dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf, 
                                   size_t len, int usermem);


/* write routines & macros */
/* ----------------------- */
/* write single byte to ring buffer */
#define DVB_RINGBUFFER_WRITE_BYTE(rbuf,byte)	\
			{ (rbuf)->data[(rbuf)->pwrite]=(byte); \
			(rbuf)->pwrite=((rbuf)->pwrite+1)%(rbuf)->size; }
/*
** write <len> bytes to ring buffer
** <usermem> specifies whether <buf> resides in user space
** returns number of bytes transferred or -EFAULT
*/
extern ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf,
                                    size_t len, int usermem);

#endif /* _DVB_RINGBUFFER_H_ */