linux/drivers/media/dvb-core/dvb_ringbuffer.h

/*
 *
 * dvb_ringbuffer.h: ring buffer implementation for the dvb driver
 *
 * Copyright (C) 2003 Oliver Endriss
 * Copyright (C) 2004 Andrew de Quincey
 *
 * based on code originally found in av7110.c & dvb_ci.c:
 * Copyright (C) 1999-2003 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;
	int               error;

	wait_queue_head_t queue;
	spinlock_t        lock;
};

#define DVB_RINGBUFFER_PKTHDRSIZE 3


/*
 * 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);
 *     else
 *         ...
 *
 *     *** read min. 1000, max. @bufsize: bytes ***
 *     avail = dvb_ringbuffer_avail(rbuf);
 *     if (avail >= 1000)
 *         count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize));
 *     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.
 *     Resetting the buffer counts as a read and write 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);


/*
 * Reset the read and write pointers to zero and flush the buffer
 * This counts as a read and write operation
 */
extern void dvb_ringbuffer_reset(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_user(struct dvb_ringbuffer *rbuf,
				   u8 __user *buf, size_t len);
extern void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf,
				   u8 *buf, size_t len);


/* 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);
extern ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf,
				         const u8 __user *buf, size_t len);


/**
 * dvb_ringbuffer_pkt_write - Write a packet into the ringbuffer.
 *
 * @rbuf: Ringbuffer to write to.
 * @buf: Buffer to write.
 * @len: Length of buffer (currently limited to 65535 bytes max).
 * returns Number of bytes written, or -EFAULT, -ENOMEM, -EVINAL.
 */
extern ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf,
					size_t len);

/**
 * dvb_ringbuffer_pkt_read_user - Read from a packet in the ringbuffer.
 *
 * @rbuf: Ringbuffer concerned.
 * @idx: Packet index as returned by dvb_ringbuffer_pkt_next().
 * @offset: Offset into packet to read from.
 * @buf: Destination buffer for data.
 * @len: Size of destination buffer.
 *
 * returns Number of bytes read, or -EFAULT.
 *
 * .. note::
 *
 *    unlike dvb_ringbuffer_read(), this does **NOT** update the read pointer
 *    in the ringbuffer. You must use dvb_ringbuffer_pkt_dispose() to mark a
 *    packet as no longer required.
 */
extern ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer *rbuf,
					    size_t idx,
				            int offset, u8 __user *buf,
					    size_t len);

/**
 * dvb_ringbuffer_pkt_read - Read from a packet in the ringbuffer.
 * Note: unlike dvb_ringbuffer_read_user(), this DOES update the read pointer
 * in the ringbuffer.
 *
 * @rbuf: Ringbuffer concerned.
 * @idx: Packet index as returned by dvb_ringbuffer_pkt_next().
 * @offset: Offset into packet to read from.
 * @buf: Destination buffer for data.
 * @len: Size of destination buffer.
 *
 * returns Number of bytes read, or -EFAULT.
 */
extern ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
				       int offset, u8 *buf, size_t len);

/**
 * dvb_ringbuffer_pkt_dispose - Dispose of a packet in the ring buffer.
 *
 * @rbuf: Ring buffer concerned.
 * @idx: Packet index as returned by dvb_ringbuffer_pkt_next().
 */
extern void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx);

/**
 * dvb_ringbuffer_pkt_next - Get the index of the next packet in a ringbuffer.
 *
 * @rbuf: Ringbuffer concerned.
 * @idx: Previous packet index, or -1 to return the first packet index.
 * @pktlen: On success, will be updated to contain the length of the packet in bytes.
 * returns Packet index (if >=0), or -1 if no packets available.
 */
extern ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen);


#endif /* _DVB_RINGBUFFER_H_ */