/*====================================================================*
- Copyright (C) 2001 Leptonica. All rights reserved.
- This software is distributed in the hope that it will be
- useful, but with NO WARRANTY OF ANY KIND.
- No author or distributor accepts responsibility to anyone for the
- consequences of using this software, or for whether it serves any
- particular purpose or works at all, unless he or she says so in
- writing. Everyone is granted permission to copy, modify and
- redistribute this source code, for commercial or non-commercial
- purposes, with the following restrictions: (1) the origin of this
- source code must not be misrepresented; (2) modified versions must
- be plainly marked as such; and (3) this notice may not be removed
- or altered from any source or modified source distribution.
*====================================================================*/
/*
* queue.c
*
* Create/Destroy L_Queue
* L_QUEUE *lqueueCreate()
* void *lqueueDestroy()
*
* Operations to add/remove to/from a L_Queue
* l_int32 lqueueAdd()
* l_int32 lqueueExtendArray()
* void *lqueueRemove()
*
* Accessors
* l_int32 lqueueGetCount()
*
* Debug output
* l_int32 lqueuePrint()
*
* The lqueue is a fifo that implements a queue of void* pointers.
* It can be used to hold a queue of any type of struct.
* Internally, it maintains two counters:
* nhead: location of head (in ptrs) from the beginning
* of the buffer
* nelem: number of ptr elements stored in the queue
* As items are added to the queue, nelem increases.
* As items are removed, nhead increases and nelem decreases.
* Any time the tail reaches the end of the allocated buffer,
* all the pointers are shifted to the left, so that the head
* is at the beginning of the array.
* If the buffer becomes more than 3/4 full, it doubles in size.
*
* [A circular queue would allow us to skip the shifting and
* to resize only when the buffer is full. For most applications,
* the extra work we do for a linear queue is not significant.]
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "allheaders.h"
static const l_int32 MIN_BUFFER_SIZE = 20; /* n'importe quoi */
static const l_int32 INITIAL_BUFFER_ARRAYSIZE = 1024; /* n'importe quoi */
/*--------------------------------------------------------------------------*
* L_Queue create/destroy *
*--------------------------------------------------------------------------*/
/*!
* lqueueCreate()
*
* Input: size of ptr array to be alloc'd (0 for default)
* Return: lqueue, or null on error
*
* Notes:
* (1) Allocates a ptr array of given size, and initializes counters.
*/
L_QUEUE *
lqueueCreate(l_int32 nalloc)
{
L_QUEUE *lq;
PROCNAME("lqueueCreate");
if (nalloc < MIN_BUFFER_SIZE)
nalloc = INITIAL_BUFFER_ARRAYSIZE;
if ((lq = (L_QUEUE *)CALLOC(1, sizeof(L_QUEUE))) == NULL)
return (L_QUEUE *)ERROR_PTR("lq not made", procName, NULL);
if ((lq->array = (void **)CALLOC(nalloc, sizeof(void *))) == NULL)
return (L_QUEUE *)ERROR_PTR("ptr array not made", procName, NULL);
lq->nalloc = nalloc;
lq->nhead = lq->nelem = 0;
return lq;
}
/*!
* lqueueDestroy()
*
* Input: &lqueue (<to be nulled>)
* freeflag (TRUE to free each remaining struct in the array)
* Return: void
*
* Notes:
* (1) If freeflag is TRUE, frees each struct in the array.
* (2) If freeflag is FALSE but there are elements on the array,
* gives a warning and destroys the array. This will
* cause a memory leak of all the items that were on the queue.
* So if the items require their own destroy function, they
* must be destroyed before the queue. The same applies to the
* auxiliary stack, if it is used.
* (3) To destroy the L_Queue, we destroy the ptr array, then
* the lqueue, and then null the contents of the input ptr.
*/
void
lqueueDestroy(L_QUEUE **plq,
l_int32 freeflag)
{
void *item;
L_QUEUE *lq;
PROCNAME("lqueueDestroy");
if (plq == NULL) {
L_WARNING("ptr address is NULL", procName);
return;
}
if ((lq = *plq) == NULL)
return;
if (freeflag) {
while(lq->nelem > 0) {
item = lqueueRemove(lq);
FREE(item);
}
}
else if (lq->nelem > 0)
L_WARNING_INT("memory leak of %d items in lqueue!",
procName, lq->nelem);
if (lq->array)
FREE(lq->array);
if (lq->stack)
lstackDestroy(&lq->stack, freeflag);
FREE(lq);
*plq = NULL;
return;
}
/*--------------------------------------------------------------------------*
* Accessors *
*--------------------------------------------------------------------------*/
/*!
* lqueueAdd()
*
* Input: lqueue
* item to be added to the tail of the queue
* Return: 0 if OK, 1 on error
*
* Notes:
* (1) The algorithm is as follows. If the queue is populated
* to the end of the allocated array, shift all ptrs toward
* the beginning of the array, so that the head of the queue
* is at the beginning of the array. Then, if the array is
* more than 0.75 full, realloc with double the array size.
* Finally, add the item to the tail of the queue.
*/
l_int32
lqueueAdd(L_QUEUE *lq,
void *item)
{
PROCNAME("lqueueAdd");
if (!lq)
return ERROR_INT("lq not defined", procName, 1);
if (!item)
return ERROR_INT("item not defined", procName, 1);
/* If filled to the end and the ptrs can be shifted to the left,
* shift them. */
if ((lq->nhead + lq->nelem >= lq->nalloc) && (lq->nhead != 0)) {
memmove(lq->array, lq->array + lq->nhead, sizeof(void *) * lq->nelem);
lq->nhead = 0;
}
/* If necessary, expand the allocated array by a factor of 2 */
if (lq->nelem > 0.75 * lq->nalloc)
lqueueExtendArray(lq);
/* Now add the item */
lq->array[lq->nhead + lq->nelem] = (void *)item;
lq->nelem++;
return 0;
}
/*!
* lqueueExtendArray()
*
* Input: lqueue
* Return: 0 if OK, 1 on error
*/
l_int32
lqueueExtendArray(L_QUEUE *lq)
{
PROCNAME("lqueueExtendArray");
if (!lq)
return ERROR_INT("lq not defined", procName, 1);
if ((lq->array = (void **)reallocNew((void **)&lq->array,
sizeof(void *) * lq->nalloc,
2 * sizeof(void *) * lq->nalloc)) == NULL)
return ERROR_INT("new ptr array not returned", procName, 1);
lq->nalloc = 2 * lq->nalloc;
return 0;
}
/*!
* lqueueRemove()
*
* Input: lqueue
* Return: ptr to item popped from the head of the queue,
* or null if the queue is empty or on error
*
* Notes:
* (1) If this is the last item on the queue, so that the queue
* becomes empty, nhead is reset to the beginning of the array.
*/
void *
lqueueRemove(L_QUEUE *lq)
{
void *item;
PROCNAME("lqueueRemove");
if (!lq)
return (void *)ERROR_PTR("lq not defined", procName, NULL);
if (lq->nelem == 0)
return NULL;
item = lq->array[lq->nhead];
lq->array[lq->nhead] = NULL;
if (lq->nelem == 1)
lq->nhead = 0; /* reset head ptr */
else
(lq->nhead)++; /* can't go off end of array because nelem > 1 */
lq->nelem--;
return item;
}
/*!
* lqueueGetCount()
*
* Input: lqueue
* Return: count, or 0 on error
*/
l_int32
lqueueGetCount(L_QUEUE *lq)
{
PROCNAME("lqueueGetCount");
if (!lq)
return ERROR_INT("lq not defined", procName, 0);
return lq->nelem;
}
/*---------------------------------------------------------------------*
* Debug output *
*---------------------------------------------------------------------*/
/*!
* lqueuePrint()
*
* Input: stream
* lqueue
* Return: 0 if OK; 1 on error
*/
l_int32
lqueuePrint(FILE *fp,
L_QUEUE *lq)
{
l_int32 i;
PROCNAME("lqueuePrint");
if (!fp)
return ERROR_INT("stream not defined", procName, 1);
if (!lq)
return ERROR_INT("lq not defined", procName, 1);
fprintf(fp, "\n L_Queue: nalloc = %d, nhead = %d, nelem = %d, array = %p\n",
lq->nalloc, lq->nhead, lq->nelem, lq->array);
for (i = lq->nhead; i < lq->nhead + lq->nelem; i++)
fprintf(fp, "array[%d] = %p\n", i, lq->array[i]);
return 0;
}