+global\Image_XMP::_get_jpeg_header_data()

Complexity

Conditions	13
Paths	10

Size

Total Lines

102

Duplication

Lines	0
Ratio	0 %

Importance

Changes

0

<?php
	public function _get_jpeg_header_data($filename)
	{
		// prevent refresh from aborting file operations and hosing file
		ignore_user_abort(true);

		// Attempt to open the jpeg file - the at symbol supresses the error message about
		// not being able to open files. The file_exists would have been used, but it
		// does not work with files fetched over http or ftp.
		if (is_readable($filename) && is_file($filename) && ($filehnd = fopen($filename, 'rb'))) {
			// great
		} else {
			return false;
		}

		// Read the first two characters
		$data = fread($filehnd, 2);

		// Check that the first two characters are 0xFF 0xD8  (SOI - Start of image)
		if ($data != "\xFF\xD8")
		{
			// No SOI (FF D8) at start of file - This probably isn't a JPEG file - close file and return;
			echo '<p>This probably is not a JPEG file</p>'."\n";
			fclose($filehnd);
			return false;
		}

		// Read the third character
		$data = fread($filehnd, 2);

		// Check that the third character is 0xFF (Start of first segment header)
		if ($data[0] != "\xFF")
		{
			// NO FF found - close file and return - JPEG is probably corrupted
			fclose($filehnd);
			return false;
		}

		// Flag that we havent yet hit the compressed image data
		$hit_compressed_image_data = false;

		$headerdata = array();
		// Cycle through the file until, one of: 1) an EOI (End of image) marker is hit,
		//                                       2) we have hit the compressed image data (no more headers are allowed after data)
		//                                       3) or end of file is hit

		while (($data[1] != "\xD9") && (!$hit_compressed_image_data) && (!feof($filehnd)))
		{
			// Found a segment to look at.
			// Check that the segment marker is not a Restart marker - restart markers don't have size or data after them
			if ((ord($data[1]) < 0xD0) || (ord($data[1]) > 0xD7))
			{
				// Segment isn't a Restart marker
				// Read the next two bytes (size)
				$sizestr = fread($filehnd, 2);

				// convert the size bytes to an integer
				$decodedsize = unpack('nsize', $sizestr);

				// Save the start position of the data
				$segdatastart = ftell($filehnd);

				// Read the segment data with length indicated by the previously read size
				$segdata = fread($filehnd, $decodedsize['size'] - 2);

				// Store the segment information in the output array
				$headerdata[] = array(
					'SegType'      => ord($data[1]),
					'SegName'      => $GLOBALS['JPEG_Segment_Names'][ord($data[1])],
					'SegDataStart' => $segdatastart,
					'SegData'      => $segdata,
				);
			}

			// If this is a SOS (Start Of Scan) segment, then there is no more header data - the compressed image data follows
			if ($data[1] == "\xDA")
			{
				// Flag that we have hit the compressed image data - exit loop as no more headers available.
				$hit_compressed_image_data = true;
			}
			else
			{
				// Not an SOS - Read the next two bytes - should be the segment marker for the next segment
				$data = fread($filehnd, 2);

				// Check that the first byte of the two is 0xFF as it should be for a marker
				if ($data[0] != "\xFF")
				{
					// NO FF found - close file and return - JPEG is probably corrupted
					fclose($filehnd);
					return false;
				}
			}
		}

		// Close File
		fclose($filehnd);
		// Alow the user to abort from now on
		ignore_user_abort(false);

		// Return the header data retrieved
		return $headerdata;
	}