research.m1stereo.tv/gitweb/ - melted/blob - src/framework/mlt_deque.c

   1 /*
   2  * mlt_deque.c -- double ended queue
   3  * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
   4  * Author: Charles Yates <charles.yates@pandora.be>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19  */
  20
  21 // Local header files
  22 #include "mlt_deque.h"
  23
  24 // System header files
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 /** Private structure.
  29 */
  30
  31 struct mlt_deque_s
  32 {
  33         void **list;
  34         int size;
  35         int count;
  36 };
  37
  38 /** Create a deque.
  39 */
  40
  41 mlt_deque mlt_deque_init( )
  42 {
  43         return calloc( 1, sizeof( struct mlt_deque_s ) );
  44 }
  45
  46 /** Return the number of items in the deque.
  47 */
  48
  49 int mlt_deque_count( mlt_deque this )
  50 {
  51         return this->count;
  52 }
  53
  54 /** Allocate space on the deque.
  55 */
  56
  57 static int mlt_deque_allocate( mlt_deque this )
  58 {
  59         if ( this->count == this->size )
  60         {
  61                 this->list = realloc( this->list, sizeof( void * ) * ( this->size + 10 ) );
  62                 this->size += 10;
  63         }
  64         return this->list == NULL;
  65 }
  66
  67 /** Push an item to the end.
  68 */
  69
  70 int mlt_deque_push_back( mlt_deque this, void *item )
  71 {
  72         int error = mlt_deque_allocate( this );
  73
  74         if ( error == 0 )
  75                 this->list[ this->count ++ ] = item;
  76
  77         return error;
  78 }
  79
  80 /** Pop an item.
  81 */
  82
  83 void *mlt_deque_pop_back( mlt_deque this )
  84 {
  85         return this->count > 0 ? this->list[ -- this->count ] : NULL;
  86 }
  87
  88 /** Queue an item at the start.
  89 */
  90
  91 int mlt_deque_push_front( mlt_deque this, void *item )
  92 {
  93         int error = mlt_deque_allocate( this );
  94
  95         if ( error == 0 )
  96         {
  97                 memmove( &this->list[ 1 ], this->list, ( this->count ++ ) * sizeof( void * ) );
  98                 this->list[ 0 ] = item;
  99         }
 100
 101         return error;
 102 }
 103
 104 /** Remove an item from the start.
 105 */
 106
 107 void *mlt_deque_pop_front( mlt_deque this )
 108 {
 109         void *item = NULL;
 110
 111         if ( this->count > 0 )
 112         {
 113                 item = this->list[ 0 ];
 114                 memmove( this->list, &this->list[ 1 ], ( -- this->count ) * sizeof( void * ) );
 115         }
 116
 117         return item;
 118 }
 119
 120 /** Inquire on item at back of deque but don't remove.
 121 */
 122
 123 void *mlt_deque_peek_back( mlt_deque this )
 124 {
 125         return this->count > 0 ? this->list[ this->count - 1 ] : NULL;
 126 }
 127
 128 /** Inquire on item at front of deque but don't remove.
 129 */
 130
 131 void *mlt_deque_peek_front( mlt_deque this )
 132 {
 133         return this->count > 0 ? this->list[ 0 ] : NULL;
 134 }
 135
 136 /** Close the queue.
 137 */
 138
 139 void mlt_deque_close( mlt_deque this )
 140 {
 141         free( this->list );
 142         free( this );
 143 }
 144
 145