RecordReader.php

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<?php
class Dataface_RecordReader implements Iterator {
        private $start = null;
        
        private $limit = null;
        
        private $query = null;
        
        private $bufferSize = 30;
        
        private $buffer = null;
        
        private $bufferStartPos = null;
        
        private $currPos = null;
        
        public $previewRecords = true;
        
        
        public function __construct(array $query, $bufferSize=30, $previewRecords = true){
                $this->start = @$query['-skip'] ? intval($query['-skip']):0;
                $this->limit = @$query['-limit'] ? intval($query['-limit']):null;
                $this->query = $query;
                $this->bufferSize = $bufferSize;
                $this->buffer = null;
                $this->bufferStartPos = null;
                $this->currPos = $this->start;
                $this->previewRecords = $previewRecords;
                if ( isset($this->limit) and $this->limit < $this->bufferSize ) $this->bufferSize = $this->limit;
        }
        
        public function __destruct(){
                $this->buffer = null;
        }
        
        
        public function rewind(){
                $this->currPos = $this->start;
                
                if ( !isset($this->bufferStartPos) ){
                        // The buffer isn't set yet so we are at the beginning
                        return;
                } else if ( $this->bufferStartPos > $this->start ){
                        // The buffer is beyond the first buffer set
                        // so we reset the buffer now
                        $this->buffer = null;
                        $this->bufferStartPos = null;
                } else {
                        // The buffer is not beyond the first set
                        // so the buffer is good.
                }
                
        }
        
        private function loadBuffer(){
                if ( $this->currPos >= $this->bufferStartPos + $this->bufferSize ){
                        $this->bufferStartPos += $this->bufferSize;
                } else if ( !isset($this->bufferStartPos) ){
                        $this->bufferStartPos = $this->start;
                } else {
                        return;
                }
                $q = $this->query;
                $q['-skip'] = $this->bufferStartPos;
                $q['-limit'] = $this->bufferSize;
                if ( isset($this->limit) ){
                        $q['-limit'] = min($this->bufferSize, $this->start+$this->limit-$this->bufferStartPos);
                }
                if ( $q['-limit'] > 0 ){
                        $this->buffer = df_get_records_array($q['-table'], $q, $q['-skip'], $q['-limit'], $this->previewRecords);
                } else {
                        $this->buffer = array();
                }
        
        }
        
        public function current(){
                $this->loadBuffer();
                return $this->buffer[$this->currPos-$this->bufferStartPos];
        }
        
        public function key(){
                return $this->currPos;
        }
        
        public function next(){
                ++$this->currPos;
        }
        
        public function valid(){
                $this->loadBuffer();
                return isset($this->buffer[$this->currPos-$this->bufferStartPos]);
        }
}