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/*
* SHL - Ring buffer
*
* Copyright (c) 2011-2014 David Herrmann <dh.herrmann@gmail.com>
* Dedicated to the Public Domain
*/
/*
* Ring buffer
*/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/uio.h>
#include "shl-macro.h"
#include "shl-ring.h"
#define RING_MASK(_r, _v) ((_v) & ((_r)->size - 1))
void shl_ring_flush(struct shl_ring *r)
{
r->start = 0;
r->used = 0;
}
void shl_ring_clear(struct shl_ring *r)
{
free(r->buf);
memset(r, 0, sizeof(*r));
}
/*
* Get data pointers for current ring-buffer data. @vec must be an array of 2
* iovec objects. They are filled according to the data available in the
* ring-buffer. 0, 1 or 2 is returned according to the number of iovec objects
* that were filled (0 meaning buffer is empty).
*
* Hint: "struct iovec" is defined in <sys/uio.h> and looks like this:
* struct iovec {
* void *iov_base;
* size_t iov_len;
* };
*/
size_t shl_ring_peek(struct shl_ring *r, struct iovec *vec)
{
if (r->used == 0) {
return 0;
} else if (r->start + r->used <= r->size) {
if (vec) {
vec[0].iov_base = &r->buf[r->start];
vec[0].iov_len = r->used;
}
return 1;
} else {
if (vec) {
vec[0].iov_base = &r->buf[r->start];
vec[0].iov_len = r->size - r->start;
vec[1].iov_base = r->buf;
vec[1].iov_len = r->used - (r->size - r->start);
}
return 2;
}
}
/*
* Copy data from the ring buffer into the linear external buffer @buf. Copy
* at most @size bytes. If the ring buffer size is smaller, copy less bytes and
* return the number of bytes copied.
*/
size_t shl_ring_copy(struct shl_ring *r, void *buf, size_t size)
{
size_t l;
if (size > r->used)
size = r->used;
if (size > 0) {
l = r->size - r->start;
if (size <= l) {
memcpy(buf, &r->buf[r->start], size);
} else {
memcpy(buf, &r->buf[r->start], l);
memcpy((uint8_t*)buf + l, r->buf, size - l);
}
}
return size;
}
/*
* Resize ring-buffer to size @nsize. @nsize must be a power-of-2, otherwise
* ring operations will behave incorrectly.
*/
static int ring_resize(struct shl_ring *r, size_t nsize)
{
uint8_t *buf;
size_t l;
buf = malloc(nsize);
if (!buf)
return -ENOMEM;
if (r->used > 0) {
l = r->size - r->start;
if (r->used <= l) {
memcpy(buf, &r->buf[r->start], r->used);
} else {
memcpy(buf, &r->buf[r->start], l);
memcpy(&buf[l], r->buf, r->used - l);
}
}
free(r->buf);
r->buf = buf;
r->size = nsize;
r->start = 0;
return 0;
}
/*
* Resize ring-buffer to provide enough room for @add bytes of new data. This
* resizes the buffer if it is too small. It returns -ENOMEM on OOM and 0 on
* success.
*/
static int ring_grow(struct shl_ring *r, size_t add)
{
size_t need;
if (r->size - r->used >= add)
return 0;
need = r->used + add;
if (need <= r->used)
return -ENOMEM;
else if (need < 4096)
need = 4096;
need = SHL_ALIGN_POWER2(need);
if (need == 0)
return -ENOMEM;
return ring_resize(r, need);
}
/*
* Push @len bytes from @u8 into the ring buffer. The buffer is resized if it
* is too small. -ENOMEM is returned on OOM, 0 on success.
*/
int shl_ring_push(struct shl_ring *r, const void *u8, size_t size)
{
int err;
size_t pos, l;
if (size == 0)
return 0;
err = ring_grow(r, size);
if (err < 0)
return err;
pos = RING_MASK(r, r->start + r->used);
l = r->size - pos;
if (l >= size) {
memcpy(&r->buf[pos], u8, size);
} else {
memcpy(&r->buf[pos], u8, l);
memcpy(r->buf, (const uint8_t*)u8 + l, size - l);
}
r->used += size;
return 0;
}
/*
* Remove @len bytes from the start of the ring-buffer. Note that we protect
* against overflows so removing more bytes than available is safe.
*/
void shl_ring_pull(struct shl_ring *r, size_t size)
{
if (size > r->used)
size = r->used;
r->start = RING_MASK(r, r->start + size);
r->used -= size;
}
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