<?php 

define('RANGE_PCRE', '/bytes=(\d*)-(\d*)/si');

class RecoverStream {

	var $ErrNo      = -1;
	var $ErrStr     = '';
	var $BufferSize = -1;

	function RecoverStream() {
		$this->__constructor();
	}

	function __constructor() {
		$_SERVER['HTTP_RANGE'] = isset($_SERVER['HTTP_RANGE']) ? $_SERVER['HTTP_RANGE'] : '';
		$this->BufferSize = 512 * 1024; // 512Kb
	}
	
	function Error(&$errno, &$errstr) {
		$errno  = $this->ErrNo;
		$errstr = $this->ErrStr;
		return ($this->ErrNo !== -1);
	}
	
	function HandleAndExit() {
		if ($this->Handle()) {
			exit();
		}
		return false;
	}
	
	function Handle() {

		$this->ErrNo  = -1;
		$this->ErrStr = '';

		$offset = 0;
		$length = 0;
		
		if (preg_match(RANGE_PCRE, $_SERVER['HTTP_RANGE'], $matches)) {
			if (($matches[1] !== '') && ($matches[2] !== '')) {
				$offset = $matches[1];
				$length = $matches[2] + 1;
			} elseif ($matches[1] !== '') {
				$offset = $matches[1];
				$length   = $this->ContentLength() - $matches[1];
			} else { // if ($matches[2] !== '') {
				$offset = $this->ContentLength() - $matches[2];
				$length   = $matches[2]; 
			}
		} else {
			$offset = 0;
			$length = $this->ContentLength();
		}
		
		if ($this->Open()) {
			if ($this->Seek($offset)) {

				$headers = $this->AdditionalHeaders();
				foreach ($headers as $header) {
					if (is_array($header) && isset($header['header']) && isset($header['replace'])) {
						header($header['header'], $header['replace']);
					} else {
						header($header);
					}
				}
				header('Content-Type: '   . $this->ContentType());
				header('Content-Length: ' . $length);

				while ($length > $this->BufferSize) {
					$content = $this->Read($this->BufferSize);
					if ($content !== false) {
						echo($content);
					} else {
						return false;
					}
					$length = $length - $this->BufferSize;					
				}

				$content = $this->Read($length);
				if ($content !== false) {
					echo($content);
				} else {
					return false;
				}

				return $this->Close();
			}
		}
		return false;
	}
	
	// abstract
	function AdditionalHeaders() {
		// RecoverStream::AdditionalHeaders() method COULD be overwritten!
		return array();
	}

	// abstract
	function Open() {
		// RecoverStream::Open() method COULD be overwritten!
		return true;
	}
	
	// abstract
	function Close() {
		// RecoverStream::Close() method COULD be overwritten!
		return true;
	}

	// abstract
	function Seek($offset) {
		die('RecoverStream::Seek() method MUST be overwritten!');
	}

	// abstract
	function Read($length) {
		die('RecoverStream::Read() method MUST be overwritten!');
	}
	
	// abstract
	function ContentType() {
		die('RecoverStream::ContentType() method MUST be overwritten!');
	}

	// abstract
	function ContentLength() {
		die('RecoverStream::ContentLength() method MUST be overwritten!');
	}
	
}

?>