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/*
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)
{
/* 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;
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;
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;
}
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