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