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/*
*
* File: squeue.h
* Author: Bryan Jurish <moocow@ling.uni-potsdam.de>
*
* Copyright (c) 2003 Bryan Jurish. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
*/
#include <stdlib.h>
#include <errno.h>
#include "squeue.h"
/*----------------------------------------------------------------------
* Creation / Deletion
*----------------------------------------------------------------------*/
squeue_ptr squeue_new(unsigned int size) {
squeue_ptr sq = (squeue_ptr)malloc(sizeof(squeue_t));
if (!sq || !size) {
errno = ENOMEM;
return NULL;
}
sq->data = (void **)malloc(size*sizeof(void *));
if (!sq->data) {
errno = ENOMEM;
return NULL;
}
# ifdef SQUEUE_DEBUG
memset(sq->data,0,size*sizeof(void *));
# endif
sq->size = size-1;
sq->head = NULL;
sq->tail = NULL;
return sq;
}
void squeue_destroy(squeue_ptr sq) {
squeue_clear(sq);
free(sq->data);
free(sq);
}
/*----------------------------------------------------------------------
* Predicates
*----------------------------------------------------------------------*/
#ifdef SQUEUE_DEBUG
char squeue_empty(squeue_ptr sq) {
return (!sq->head);
}
char squeue_full(squeue_ptr sq) {
return (sq->head && sq->head == squeue_next(sq,sq->tail));
}
#endif
/*----------------------------------------------------------------------
* utilities
*----------------------------------------------------------------------*/
#ifdef SQUEUE_DEBUG
void **squeue_prev(squeue_t *sq, void **p) {
//return (p && p > sq->data ? p-1 : p+sq->size);
return (p && p > sq->data ? p-1 : sq->data+sq->size);
}
void **squeue_next(squeue_t *sq, void **p) {
return (p && p < sq->data+sq->size ? p+1 : sq->data);
}
#endif
/*----------------------------------------------------------------------
* Manipulation
*----------------------------------------------------------------------*/
#ifdef SQUEUE_DEBUG
void squeue_clear(squeue_ptr sq) {
sq->head = NULL;
sq->tail = NULL;
# ifdef SQUEUE_DEBUG
memset(sq->data,0,sq->size*sizeof(void *));
# endif
}
#endif
void **squeue_prepend(squeue_ptr sq, void *data) {
sq->head = squeue_prev(sq,sq->head);
if (!sq->tail) {
// -- empty-queue
sq->tail = sq->head;
} else if (sq->head == sq->tail) {
// -- xrun (full queue)
sq->head = squeue_next(sq,sq->head);
return NULL;
// alternative: push the overwritten older pointer along a notch
//sq->tail = squeue_prev(sq,sq->tail);
}
// -- set the data
*(sq->head) = data;
return sq->head;
}
void **squeue_append(squeue_ptr sq, void *data) {
sq->tail = squeue_next(sq,sq->tail);
if (!sq->head) {
// -- empty-queue check
sq->head = sq->tail;
} else if (sq->tail == sq->head) {
// -- xrun (full queue)
sq->tail = squeue_prev(sq,sq->tail);
return NULL;
// alternative: push the overwritten older pointer along a notch
//sq->head = squeue_next(sq,sq->head);
}
// -- set the data
*(sq->tail) = data;
return sq->tail;
}
/*----------------------------------------------------------------------
* Access
*----------------------------------------------------------------------*/
void *squeue_shift(squeue_ptr sq) {
if (squeue_empty(sq)) return NULL;
else {
void *data = *(sq->head);
// -- empty queue check
if (sq->head == sq->tail) {
sq->head = NULL;
sq->tail = NULL;
} else {
sq->head = squeue_next(sq, sq->head);
}
return data;
}
}
void *squeue_pop(squeue_ptr sq) {
if (squeue_empty(sq)) return NULL;
else {
void *data = *(sq->tail);
if (sq->head == sq->tail) {
sq->head = NULL;
sq->tail = NULL;
} else {
sq->tail = squeue_prev(sq, sq->tail);
}
return data;
}
}
#ifdef SQUEUE_DEBUG
// Returns the first datum in the queue, or NULL if queue is empty.
void *squeue_peek_head(squeue_ptr sq) {
return sq->head ? *(sq->head) : NULL;
}
// Returns the final datum in the queue, or NULL if queue is empty.
void *squeue_peek_tail(squeue_ptr sq) {
return sq->tail ? *(sq->tail) : NULL;
}
#endif
/*----------------------------------------------------------------------
* Iteration
*----------------------------------------------------------------------*/
#ifdef SQUEUE_DEBUG
// Returns a pointer-pointer to the first datum in the queue,
// or NULL if queue is empty.
squeue_iter_t squeue_iter_first(squeue_t *sq) { return sq->head; }
// Returns a pointer-pointer to the final datum in the queue,
// or NULL if queue is empty.
squeue_iter_t squeue_iter_last(squeue_t *sq) { return sq->tail; }
// Returns a pointer to the next datum in the queue, or
// NULL if queue is empty.
squeue_iter_t squeue_iter_next(squeue_t *sq, squeue_iter_t p) {
return p == sq->tail ? NULL : squeue_next(sq,p);
}
// Returns a pointer-pointer to the final datum in the queue,
// or NULL if queue is empty.
extern squeue_iter_t squeue_iter_prev(squeue_t *sq, squeue_iter_t p) {
return p == sq->head ? NULL : squeue_prev(sq,p);
}
// Returns a true value if p is a valid iterator value, false otherwise.
// Warning: this is not even as paranoid as it ought to be!
extern char squeue_iter_valid(squeue_t *sq, squeue_iter_t p) {
return (p && p >= sq->data && p <= sq->data+sq->size);
}
/// Get the datum from an iterator.
void *squeue_iter_data(squeue_iter_t p) { return *p; }
#endif
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