/*

	SFIFO 1.3 Simple portable lock-free FIFO

	(c) 2000-2002, David Olofson - free software under the terms of the LGPL 2.1

*/

/*

-----------------------------------------------------------

TODO:

	* Is there a way to avoid losing one byte of buffer

	  space to avoid extra variables or locking?

	* Test more compilers and environments.

-----------------------------------------------------------

 */

#include	<string.h>

#include	<stdlib.h>

#include "sfifo.h"

#include "debug.h"

/*

 * Alloc buffer, init FIFO etc...

 */

SFIFO_SCOPE int sfifo_init(sfifo_t *f, int size)

{

	memset(f, 0, sizeof(sfifo_t));

	if(size > SFIFO_MAX_BUFFER_SIZE)

		return -EINVAL;

	/*

	 * Set sufficient power-of-2 size.

	 *

	 * No, there's no bug. If you need

	 * room for N bytes, the buffer must

	 * be at least N+1 bytes. (The fifo

	 * can't tell 'empty' from 'full'

	 * without unsafe index manipulations

	 * otherwise.)

	 */

	f->size = 1;

	for(; f->size <= size; f->size <<= 1)

		;

	/* Get buffer */

	if( 0 == (f->buffer = (void *)malloc(f->size)) )

		return -ENOMEM;

	return 0;

}

/*

 * Dealloc buffer etc...

 */

SFIFO_SCOPE void sfifo_close(sfifo_t *f)

{

	if(f->buffer) {

		free(f->buffer);

		f->buffer = NULL;	/* Prevent double free */

	}

}

/*

 * Empty FIFO buffer

 */

SFIFO_SCOPE void sfifo_flush(sfifo_t *f)

{

	debug("sfifo_flush()");

	/* Reset positions */

	f->readpos = 0;

	f->writepos = 0;

}

/*

 * Write bytes to a FIFO

 * Return number of bytes written, or an error code

 */

SFIFO_SCOPE int sfifo_write(sfifo_t *f, const void *_buf, int len)

{

	int total;

	int i;

	const char *buf = (const char *)_buf;

	if(!f->buffer)

		return -ENODEV;	/* No buffer! */

	/* total = len = min(space, len) */

	total = sfifo_space(f);

	debug1("sfifo_space() = %d",total);

	if(len > total)

		len = total;

	else

		total = len;

	debug1("sfifo_write() = %d", total);

	i = f->writepos;

	if(i + len > f->size)

	{

		memcpy(f->buffer + i, buf, f->size - i);

		buf += f->size - i;

		len -= f->size - i;

		i = 0;

	}

	memcpy(f->buffer + i, buf, len);

	f->writepos = i + len;

	return total;

}

/*

 * Read bytes from a FIFO

 * Return number of bytes read, or an error code

 */

SFIFO_SCOPE int sfifo_read(sfifo_t *f, void *_buf, int len)

{

	int total;

	int i;

	char *buf = (char *)_buf;

	if(!f->buffer)

		return -ENODEV;	/* No buffer! */

	/* total = len = min(used, len) */

	total = sfifo_used(f);

	debug1("sfifo_used() = %d",total);

	if(len > total)

		len = total;

	else

		total = len;

	debug1("sfifo_read() = %d", total);

	i = f->readpos;

	if(i + len > f->size)

	{

		memcpy(buf, f->buffer + i, f->size - i);

		buf += f->size - i;

		len -= f->size - i;

		i = 0;

	}

	memcpy(buf, f->buffer + i, len);

	f->readpos = i + len;

	return total;

}