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/* queue.h -- a queue abstraction
* Copyright 2009, 2011 Red Hat Inc., Durham, North Carolina.
* All Rights Reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Authors:
* Steve Grubb <sgrubb@redhat.com>
* Miloslav Trmač <mitr@redhat.com>
*/
#ifndef QUEUE_HEADER
#define QUEUE_HEADER
#include <sys/types.h>
struct queue;
enum {
// Queue storage. Both options can be set at the same time.
Q_IN_MEMORY = 1 << 0, // Keep a copy of the queue in memory
Q_IN_FILE = 1 << 1, // Store the queue in a file
// Other flags for use with Q_IN_FILE
Q_CREAT = 1 << 2, // Create the queue if it does not exist
Q_EXCL = 1 << 3, // With Q_CREAT, don't open an existing queue
Q_SYNC = 1 << 4, // fdatasync() after each operation
Q_RESIZE = 1 << 5, // resize the queue if needed
};
/* Open a queue using Q_FLAGS and return it. If Q_IN_FILE: use PATH for the
* file, NUM_ENTRIES must be the same for all users of the file unless Q_RESIZE
* is set. ENTRY_SIZE is the maximum length of a stored string, including the
* trailing NUL. If Q_IN_FILE, it must be the same for all users of the file.
* On error, return NULL and set errno. */
struct queue *q_open(int q_flags, const char *path, size_t num_entries,
size_t entry_size);
/* Close Q. */
void q_close(struct queue *q);
/* Add DATA to tail of Q. Return 0 on success, -1 on error and set errno. */
int q_append(struct queue *q, const char *data);
/* Peek at head of Q, storing it into BUF of SIZE. Return 1 if an entry
* exists, 0 if queue is empty. On error, return -1 and set errno. */
int q_peek(struct queue *q, char *buf, size_t size);
/* Drop head of Q and return 0. On error, return -1 and set errno. */
int q_drop_head(struct queue *q);
/* Return the number of entries in Q. */
size_t q_queue_length(const struct queue *q);
#endif
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