queue.c File Reference

#include <string.h>
#include "allheaders.h"

Go to the source code of this file.

Functions
static l_int32	lqueueExtendArray (L_QUEUE *lq)
L_QUEUE *	lqueueCreate (l_int32 nalloc)
void	lqueueDestroy (L_QUEUE **plq, l_int32 freeflag)
l_ok	lqueueAdd (L_QUEUE *lq, void *item)
void *	lqueueRemove (L_QUEUE *lq)
l_int32	lqueueGetCount (L_QUEUE *lq)
l_ok	lqueuePrint (FILE *fp, L_QUEUE *lq)

Variables
static const l_int32	MIN_BUFFER_SIZE = 20
static const l_int32	INITIAL_BUFFER_ARRAYSIZE = 1024

Detailed Description

     Create/Destroy L_Queue
         L_QUEUE        *lqueueCreate()
         void           *lqueueDestroy()

     Operations to add/remove to/from a L_Queue
         l_int32         lqueueAdd()
         static 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.]

Definition in file queue.c.

Function Documentation

lqueueAdd()

l_ok lqueueAdd	(	L_QUEUE *	lq,
		void *	item )

lqueueAdd()

Parameters

[in]	lq	lqueue
[in]	item	to be added to the tail of the queue

Returns

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.

Definition at line 184 of file queue.c.

References L_Queue::array, lqueueExtendArray(), L_Queue::nalloc, L_Queue::nelem, and L_Queue::nhead.

lqueueCreate()

L_QUEUE * lqueueCreate

(

l_int32

nalloc

)

lqueueCreate()

Parameters

[in]

nalloc

size of ptr array to be alloc'd; 0 for default

Returns

lqueue, or NULL on error

Notes:
     (1) Allocates a ptr array of given size, and initializes counters.

Definition at line 93 of file queue.c.

References L_Queue::array, lqueueDestroy(), L_Queue::nalloc, L_Queue::nelem, and L_Queue::nhead.

lqueueDestroy()

void lqueueDestroy	(	L_QUEUE **	plq,
		l_int32	freeflag )

lqueueDestroy()

Parameters

[in,out]	plq	will be set to null before returning
[in]	freeflag	TRUE to free each remaining struct in the array

Returns

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.

Definition at line 132 of file queue.c.

References L_Queue::array, lqueueRemove(), L_Queue::nelem, and L_Queue::stack.

Referenced by lqueueCreate().

lqueueExtendArray()

static l_int32 lqueueExtendArray ( L_QUEUE * lq )

static

lqueueExtendArray()

Parameters

[in]

lq

lqueue

Returns

0 if OK, 1 on error

Definition at line 220 of file queue.c.

References L_Queue::array, and L_Queue::nalloc.

Referenced by lqueueAdd().

lqueueGetCount()

l_int32 lqueueGetCount

(

L_QUEUE *

lq

)

lqueueGetCount()

Parameters

[in]

lq

lqueue

Returns

count, or 0 on error

Definition at line 276 of file queue.c.

References L_Queue::nelem.

lqueuePrint()

l_ok lqueuePrint	(	FILE *	fp,
		L_QUEUE *	lq )

lqueuePrint()

Parameters

[in]	fp	file stream
[in]	lq	lqueue

Returns

0 if OK; 1 on error

Definition at line 296 of file queue.c.

References L_Queue::array, L_Queue::nalloc, L_Queue::nelem, and L_Queue::nhead.

lqueueRemove()

void * lqueueRemove

(

L_QUEUE *

lq

)

lqueueRemove()

Parameters

[in]

lq

lqueue

Returns

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.

Definition at line 249 of file queue.c.

References L_Queue::array, L_Queue::nelem, and L_Queue::nhead.

Referenced by lqueueDestroy().

Variable Documentation

INITIAL_BUFFER_ARRAYSIZE

const l_int32 INITIAL_BUFFER_ARRAYSIZE = 1024

static

Definition at line 73 of file queue.c.

MIN_BUFFER_SIZE

const l_int32 MIN_BUFFER_SIZE = 20

static

Definition at line 72 of file queue.c.