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         mlt_deque this = malloc( sizeof( struct mlt_deque_s ) );
  44         if ( this != NULL )
  45         {
  46                 this->list = NULL;
  47                 this->size = 0;
  48                 this->count = 0;
  49         }
  50         return this;
  51 }
  52
  53 /** Return the number of items in the deque.
  54 */
  55
  56 int mlt_deque_count( mlt_deque this )
  57 {
  58         return this->count;
  59 }
  60
  61 /** Allocate space on the deque.
  62 */
  63
  64 static int mlt_deque_allocate( mlt_deque this )
  65 {
  66         if ( this->count == this->size )
  67         {
  68                 this->list = realloc( this->list, sizeof( void * ) * ( this->size + 20 ) );
  69                 this->size += 20;
  70         }
  71         return this->list == NULL;
  72 }
  73
  74 /** Push an item to the end.
  75 */
  76
  77 int mlt_deque_push_back( mlt_deque this, void *item )
  78 {
  79         int error = mlt_deque_allocate( this );
  80
  81         if ( error == 0 )
  82                 this->list[ this->count ++ ] = item;
  83
  84         return error;
  85 }
  86
  87 /** Pop an item.
  88 */
  89
  90 void *mlt_deque_pop_back( mlt_deque this )
  91 {
  92         return this->count > 0 ? this->list[ -- this->count ] : NULL;
  93 }
  94
  95 /** Queue an item at the start.
  96 */
  97
  98 int mlt_deque_push_front( mlt_deque this, void *item )
  99 {
 100         int error = mlt_deque_allocate( this );
 101
 102         if ( error == 0 )
 103         {
 104                 memmove( &this->list[ 1 ], this->list, ( this->count ++ ) * sizeof( void * ) );
 105                 this->list[ 0 ] = item;
 106         }
 107
 108         return error;
 109 }
 110
 111 /** Remove an item from the start.
 112 */
 113
 114 void *mlt_deque_pop_front( mlt_deque this )
 115 {
 116         void *item = NULL;
 117
 118         if ( this->count > 0 )
 119         {
 120                 item = this->list[ 0 ];
 121                 memmove( this->list, &this->list[ 1 ], ( -- this->count ) * sizeof( void * ) );
 122         }
 123
 124         return item;
 125 }
 126
 127 /** Inquire on item at back of deque but don't remove.
 128 */
 129
 130 void *mlt_deque_peek_back( mlt_deque this )
 131 {
 132         return this->count > 0 ? this->list[ this->count - 1 ] : NULL;
 133 }
 134
 135 /** Inquire on item at front of deque but don't remove.
 136 */
 137
 138 void *mlt_deque_peek_front( mlt_deque this )
 139 {
 140         return this->count > 0 ? this->list[ 0 ] : NULL;
 141 }
 142
 143 /** Close the queue.
 144 */
 145
 146 void mlt_deque_close( mlt_deque this )
 147 {
 148         free( this->list );
 149         free( this );
 150 }
 151
 152