<?php
/*
	This class outputs the body of a joined series of truncated FLV files (no metadata or first 9 bytes).
	It assumes you've already sent the beginning of the file and will send the end of the file afterward.
	It also assumes that each file starts its millisecond numbering with 0.
*/

class FlvOutput
{
	protected $files;
	protected $ms = 0;
	protected $previous_length = 0;
	protected $content;
	protected $content_length;
	protected $folder = '.';
	protected $chapter_folder = 'chapters';
	protected $cache;
	const FRAME_HEADER_LENGTH = 15;
	const FRAME_HEADER_META_DIFF = 4;

	public function __construct()
	{
	}

	public function Folder($folder) #set the folder in which the files are located; no trailing slash
	{
		$this->folder = $folder;
	}

	public function Lines(ReadDbFile $obj) #set which files to stream
	{
		$this->files = $obj->Lines();
	}

	public function PreviousLength($length) #set an int indicating the length of the previous meta frame
	{
		$this->previous['full_length'] = $length;
	}

	public function StreamChapter(ReadDbFile $obj) #stream a complete chapter; no need to mess with metadata
	{
		$chapter = $obj->CompleteChapter();
		$file = $this->folder . '/' . $this->chapter_folder . "/$chapter.flv";
		if (@file_exists($file) && @readfile($file)) return true;
		return false;
	}

	public function Stream() #stream all the files
	{
		if (empty($this->files)) return false; #no files to stream
		foreach ($this->files as $file)
		{
			$this->get_file_contents($file);
			$this->do_stream();
		}
	}

	protected function do_stream() #do the actual streaming
	{
		$this->handle_first_frame();
		$content = $this->content;
		$this->content = '';
		$content_length = strlen($content);
		$fhl = self::FRAME_HEADER_LENGTH;
		$this_ms = $this->ms;
		while ($content_length >= $fhl)
		{
			list(, $length) = unpack('N', "\0" . substr($content, 5, 3));
			$length += $fhl;
			$frame = substr($content, 0, $length);
			$content = substr($content, $length);
			$content_length -= $length;
			if ($this_ms)
			{
				list(, $ms) = unpack('N', "\0" . substr($frame, 8, 3));
				$frame = substr_replace($frame,
					#get 3 bytes of the 4 as required by the format
					substr(pack('N', $ms + $this_ms), 1),
					8, 3);
			}
			echo $frame;
			flush();
		}
		if (!$this_ms) list(, $ms) = unpack('N', "\0" . substr($frame, 8, 3));
		$this->ms = $this_ms + $ms;
		$this->previous_length = $length - self::FRAME_HEADER_META_DIFF;
	}

	protected function handle_first_frame() #correct the frame length of the previous frame, which is unpredictable
	{
		$this->content = substr_replace($this->content, pack('N', $this->previous_length), 0, 4);
	}

	protected function get_file_contents($file)
	{
		$file = $this->folder . "/$file";
		if (@file_exists($file)) $this->content = file_get_contents($file);
		else new FatalError(__METHOD__ . ":'$file' doesn't exist");
	}
}

?>