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/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*
* Queue data structure implementation.
*/
#include "queue.h"
#include "util.h"
void queue_init(struct queue const *q)
{
ASSERT(POWER_OF_TWO(q->buffer_units));
q->state->head = 0;
q->state->tail = 0;
}
int queue_is_empty(struct queue const *q)
{
return q->state->head == q->state->tail;
}
size_t queue_count(struct queue const *q)
{
return q->state->tail - q->state->head;
}
size_t queue_space(struct queue const *q)
{
return q->buffer_units - queue_count(q);
}
size_t queue_add_unit(struct queue const *q, void const *src)
{
size_t tail = q->state->tail & (q->buffer_units - 1);
if (queue_space(q) == 0)
return 0;
if (q->unit_bytes == 1)
q->buffer[tail] = *((uint8_t *) src);
else
memcpy(q->buffer + tail * q->unit_bytes, src, q->unit_bytes);
q->state->tail += 1;
return 1;
}
size_t queue_add_units(struct queue const *q, void const *src, size_t count)
{
return queue_add_memcpy(q, src, count, memcpy);
}
size_t queue_add_memcpy(struct queue const *q,
void const *src,
size_t count,
void *(*memcpy)(void *dest,
void const *src,
size_t n))
{
size_t transfer = MIN(count, queue_space(q));
size_t tail = q->state->tail & (q->buffer_units - 1);
size_t first = MIN(transfer, q->buffer_units - tail);
memcpy(q->buffer + tail * q->unit_bytes,
src,
first * q->unit_bytes);
if (first < transfer)
memcpy(q->buffer,
((uint8_t const *) src) + first * q->unit_bytes,
(transfer - first) * q->unit_bytes);
q->state->tail += transfer;
return transfer;
}
static void queue_read_safe(struct queue const *q,
void *dest,
size_t head,
size_t transfer,
void *(*memcpy)(void *dest,
void const *src,
size_t n))
{
size_t first = MIN(transfer, q->buffer_units - head);
memcpy(dest,
q->buffer + head * q->unit_bytes,
first * q->unit_bytes);
if (first < transfer)
memcpy(((uint8_t *) dest) + first * q->unit_bytes,
q->buffer,
(transfer - first) * q->unit_bytes);
}
size_t queue_remove_unit(struct queue const *q, void *dest)
{
size_t head = q->state->head & (q->buffer_units - 1);
if (queue_count(q) == 0)
return 0;
if (q->unit_bytes == 1)
*((uint8_t *) dest) = q->buffer[head];
else
memcpy(dest, q->buffer + head * q->unit_bytes, q->unit_bytes);
q->state->head += 1;
return 1;
}
size_t queue_remove_units(struct queue const *q, void *dest, size_t count)
{
return queue_remove_memcpy(q, dest, count, memcpy);
}
size_t queue_remove_memcpy(struct queue const *q,
void *dest,
size_t count,
void *(*memcpy)(void *dest,
void const *src,
size_t n))
{
size_t transfer = MIN(count, queue_count(q));
size_t head = q->state->head & (q->buffer_units - 1);
queue_read_safe(q, dest, head, transfer, memcpy);
q->state->head += transfer;
return transfer;
}
size_t queue_peek_units(struct queue const *q,
void *dest,
size_t i,
size_t count)
{
size_t available = queue_count(q);
size_t transfer = MIN(count, available - i);
if (i < available) {
size_t head = (q->state->head + i) & (q->buffer_units - 1);
queue_read_safe(q, dest, head, transfer, memcpy);
}
return transfer;
}
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