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/* Copyright (c) 2008, 2009, 2012, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "byteq.h"
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include "util.h"
/* Initializes 'q' as an empty byteq that uses the 'size' bytes of 'buffer' to
* store data. 'size' must be a power of 2.
*
* The caller must ensure that 'buffer' remains available to the byteq as long
* as 'q' is in use. */
void
byteq_init(struct byteq *q, uint8_t *buffer, size_t size)
{
ovs_assert(is_pow2(size));
q->buffer = buffer;
q->size = size;
q->head = q->tail = 0;
}
/* Returns the number of bytes current queued in 'q'. */
int
byteq_used(const struct byteq *q)
{
return q->head - q->tail;
}
/* Returns the number of bytes that can be added to 'q' without overflow. */
int
byteq_avail(const struct byteq *q)
{
return q->size - byteq_used(q);
}
/* Returns true if no bytes are queued in 'q',
* false if at least one byte is queued. */
bool
byteq_is_empty(const struct byteq *q)
{
return !byteq_used(q);
}
/* Returns true if 'q' has no room to queue additional bytes,
* false if 'q' has room for at least one more byte. */
bool
byteq_is_full(const struct byteq *q)
{
return !byteq_avail(q);
}
/* Adds 'c' at the head of 'q', which must not be full. */
void
byteq_put(struct byteq *q, uint8_t c)
{
ovs_assert(!byteq_is_full(q));
*byteq_head(q) = c;
q->head++;
}
/* Adds the 'n' bytes in 'p' at the head of 'q', which must have at least 'n'
* bytes of free space. */
void
byteq_putn(struct byteq *q, const void *p_, size_t n)
{
const uint8_t *p = p_;
ovs_assert(byteq_avail(q) >= n);
while (n > 0) {
size_t chunk = MIN(n, byteq_headroom(q));
memcpy(byteq_head(q), p, chunk);
byteq_advance_head(q, chunk);
p += chunk;
n -= chunk;
}
}
/* Appends null-terminated string 's' to the head of 'q', which must have
* enough space. The null terminator is not added to 'q'. */
void
byteq_put_string(struct byteq *q, const char *s)
{
byteq_putn(q, s, strlen(s));
}
/* Removes a byte from the tail of 'q' and returns it. 'q' must not be
* empty. */
uint8_t
byteq_get(struct byteq *q)
{
uint8_t c;
ovs_assert(!byteq_is_empty(q));
c = *byteq_tail(q);
q->tail++;
return c;
}
/* Writes as much of 'q' as possible to 'fd'. Returns 0 if 'q' is fully
* drained by the write, otherwise a positive errno value (e.g. EAGAIN if a
* socket or tty buffer filled up). */
int
byteq_write(struct byteq *q, int fd)
{
while (!byteq_is_empty(q)) {
ssize_t n = write(fd, byteq_tail(q), byteq_tailroom(q));
if (n > 0) {
byteq_advance_tail(q, n);
} else {
ovs_assert(n < 0);
return errno;
}
}
return 0;
}
/* Reads as much possible from 'fd' into 'q'. Returns 0 if 'q' is completely
* filled up by the read, EOF if end-of-file was reached before 'q' was filled,
* and otherwise a positive errno value (e.g. EAGAIN if a socket or tty buffer
* was drained). */
int
byteq_read(struct byteq *q, int fd)
{
while (!byteq_is_full(q)) {
ssize_t n = read(fd, byteq_head(q), byteq_headroom(q));
if (n > 0) {
byteq_advance_head(q, n);
} else {
return !n ? EOF : errno;
}
}
return 0;
}
/* Returns the number of contiguous bytes of in-use space starting at the tail
* of 'q'. */
int
byteq_tailroom(const struct byteq *q)
{
int used = byteq_used(q);
int tail_to_end = q->size - (q->tail & (q->size - 1));
return MIN(used, tail_to_end);
}
/* Returns the first in-use byte of 'q', the point at which data is removed
* from 'q'. */
const uint8_t *
byteq_tail(const struct byteq *q)
{
return &q->buffer[q->tail & (q->size - 1)];
}
/* Removes 'n' bytes from the tail of 'q', which must have at least 'n' bytes
* of tailroom. */
void
byteq_advance_tail(struct byteq *q, unsigned int n)
{
ovs_assert(byteq_tailroom(q) >= n);
q->tail += n;
}
/* Returns the byte after the last in-use byte of 'q', the point at which new
* data will be added to 'q'. */
uint8_t *
byteq_head(struct byteq *q)
{
return &q->buffer[q->head & (q->size - 1)];
}
/* Returns the number of contiguous bytes of free space starting at the head
* of 'q'. */
int
byteq_headroom(const struct byteq *q)
{
int avail = byteq_avail(q);
int head_to_end = q->size - (q->head & (q->size - 1));
return MIN(avail, head_to_end);
}
/* Adds to 'q' the 'n' bytes after the last currently in-use byte of 'q'. 'q'
* must have at least 'n' bytes of headroom. */
void
byteq_advance_head(struct byteq *q, unsigned int n)
{
ovs_assert(byteq_headroom(q) >= n);
q->head += n;
}
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