/*
** Copyright (C) 2004-2006 by Carnegie Mellon University.
**
** @OPENSOURCE_HEADER_START@
** 
** Use of the SILK system and related source code is subject to the terms 
** of the following licenses:
** 
** GNU Public License (GPL) Rights pursuant to Version 2, June 1991
** Government Purpose License Rights (GPLR) pursuant to DFARS 252.225-7013
** 
** NO WARRANTY
** 
** ANY INFORMATION, MATERIALS, SERVICES, INTELLECTUAL PROPERTY OR OTHER 
** PROPERTY OR RIGHTS GRANTED OR PROVIDED BY CARNEGIE MELLON UNIVERSITY 
** PURSUANT TO THIS LICENSE (HEREINAFTER THE "DELIVERABLES") ARE ON AN 
** "AS-IS" BASIS. CARNEGIE MELLON UNIVERSITY MAKES NO WARRANTIES OF ANY 
** KIND, EITHER EXPRESS OR IMPLIED AS TO ANY MATTER INCLUDING, BUT NOT 
** LIMITED TO, WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE, 
** MERCHANTABILITY, INFORMATIONAL CONTENT, NONINFRINGEMENT, OR ERROR-FREE 
** OPERATION. CARNEGIE MELLON UNIVERSITY SHALL NOT BE LIABLE FOR INDIRECT, 
** SPECIAL OR CONSEQUENTIAL DAMAGES, SUCH AS LOSS OF PROFITS OR INABILITY 
** TO USE SAID INTELLECTUAL PROPERTY, UNDER THIS LICENSE, REGARDLESS OF 
** WHETHER SUCH PARTY WAS AWARE OF THE POSSIBILITY OF SUCH DAMAGES. 
** LICENSEE AGREES THAT IT WILL NOT MAKE ANY WARRANTY ON BEHALF OF 
** CARNEGIE MELLON UNIVERSITY, EXPRESS OR IMPLIED, TO ANY PERSON 
** CONCERNING THE APPLICATION OF OR THE RESULTS TO BE OBTAINED WITH THE 
** DELIVERABLES UNDER THIS LICENSE.
** 
** Licensee hereby agrees to defend, indemnify, and hold harmless Carnegie 
** Mellon University, its trustees, officers, employees, and agents from 
** all claims or demands made against them (and any related losses, 
** expenses, or attorney's fees) arising out of, or relating to Licensee's 
** and/or its sub licensees' negligent use or willful misuse of or 
** negligent conduct or willful misconduct regarding the Software, 
** facilities, or other rights or assistance granted by Carnegie Mellon 
** University under this License, including, but not limited to, any 
** claims of product liability, personal injury, death, damage to 
** property, or violation of any laws or regulations.
** 
** Carnegie Mellon University Software Engineering Institute authored 
** documents are sponsored by the U.S. Department of Defense under 
** Contract F19628-00-C-0003. Carnegie Mellon University retains 
** copyrights in all material produced under this contract. The U.S. 
** Government retains a non-exclusive, royalty-free license to publish or 
** reproduce these documents, or allow others to do so, for U.S. 
** Government purposes only pursuant to the copyright license under the 
** contract clause at 252.227.7013.
** 
** @OPENSOURCE_HEADER_END@
*/

/*
**
**    Circular buffer API
**
*/


#include "silk.h"

RCSIDENT("$SiLK: circbuf.c 2920 2006-02-06 18:02:36Z mthomas $");

#include "circbuf.h"


typedef void (*cleanupHandler)(void *);

typedef struct circBuf_struct_t {
    uint32_t maxsize;		/* Maximum number of cells */
    uint32_t size;		/* Current number of cells in use */
    uint32_t cellsize;		/* Size of a single cell */
    uint32_t head;		/* Index of next unused cell */
    uint32_t tail;	   /* Index of oldest unprocessed used cell */
    uint8_t *data;		/* The cell data */
    pthread_mutex_t mutex;	/* Mutex */
    pthread_cond_t cond;        /* Condition variable */
    unsigned destroyed : 1;  	/* Whether we are being destroyed */
    unsigned init_head : 1;	/* Whether our first head has been asked for */
    unsigned writing   : 1;
    unsigned reading   : 1;
} circBuf_struct_t;

/*
**    +---+---+---+---+---+---+---+
**    |   | u | d | d | d | f |   |
**    +---+---+---+---+---+---+---+
**    t               h
**  
**    d = data
**    f = being filled
**    u = data-in-use
**    t = tail index
**    h = head index
**    <blank> = unused
**  
*/

circBuf_t circBufCreate(uint32_t item_size, uint32_t size)
{
    circBuf_t buf;

    if (size < 3) {
        return NULL;
    }
    buf = (circBuf_t)calloc(1, sizeof(circBuf_struct_t));
    if (buf == NULL) {
        return NULL;
    }
    buf->data = (uint8_t *)calloc(size, item_size);
    if (buf->data == NULL) {
        free(buf);
        return NULL;
    }
    buf->maxsize = size;
    buf->cellsize = item_size;
    pthread_mutex_init(&buf->mutex, NULL);
    pthread_cond_init(&buf->cond, NULL);
    return buf;
}


uint8_t *circBufNextHead(circBuf_t buf)
{
    uint8_t *retval;

    pthread_cleanup_push((cleanupHandler)pthread_mutex_unlock,
                         (void *)(&buf->mutex));
    pthread_mutex_lock(&buf->mutex);
    buf->writing = 1;
    if (++buf->head == buf->maxsize) {
        buf->head = 0;
    }
    retval = &buf->data[buf->head * buf->cellsize];
    while (!buf->destroyed && (buf->size == buf->maxsize - 2)) {
        pthread_cond_wait(&buf->cond, &buf->mutex);
    }
    if (buf->destroyed) {
        retval = NULL;
    } else if (!buf->init_head) {
        buf->init_head = 1; /* Do not increment size the first time */
    } else if (buf->size++ == 0) {
        /* Used to be empty */
        pthread_cond_broadcast(&buf->cond);
    }
    buf->writing = 0;
    if (buf->destroyed) {
        pthread_cond_broadcast(&buf->cond);
    }
    pthread_cleanup_pop(1);

    return retval;
}


uint8_t *circBufNextTail(circBuf_t buf)
{
    uint8_t *retval;

    pthread_cleanup_push((cleanupHandler)pthread_mutex_unlock,
                         (void *)(&buf->mutex));
    pthread_mutex_lock(&buf->mutex); 
    buf->reading = 1;
    while (!buf->destroyed && buf->size == 0) {
        pthread_cond_wait(&buf->cond, &buf->mutex);
    }
    if (buf->destroyed) {
        retval = NULL;
    } else {
        if (buf->size-- == buf->maxsize - 2) {
            /* We were full, we will be no longer after this */
            pthread_cond_broadcast(&buf->cond);
        }
        if (++buf->tail == buf->maxsize) {
            buf->tail = 0;
        }
        retval = &buf->data[buf->tail * buf->cellsize];
    }
    buf->reading = 0;
    if (buf->destroyed) {
        pthread_cond_broadcast(&buf->cond);
    }
    pthread_cleanup_pop(1);

    return retval;
}

void circBufDestroy(circBuf_t buf)
{
    pthread_cleanup_push((cleanupHandler)pthread_mutex_unlock,
                         (void *)(&buf->mutex));
    pthread_mutex_lock(&buf->mutex);
  
    buf->destroyed = 1;
    pthread_cond_broadcast(&buf->cond);
    while (buf->reading || buf->writing) {
        pthread_cond_wait(&buf->cond, &buf->mutex);
    }
    pthread_cleanup_pop(1);

    pthread_mutex_destroy(&buf->mutex);
    pthread_cond_destroy(&buf->cond);
    free(buf->data);
    free(buf);
}