From d2750b650fb3600ef2cf7b7139998e1a71c7d5ef Mon Sep 17 00:00:00 2001
From: Dan Villiom Podlaski Christiansen <danchr@gmail.com>
Date: Wed, 7 Sep 2016 03:58:33 +0200
Subject: [ticket/14774] Support partial downloads of attachments

phpBB already had limited support for partial downloads, but only for
resuming downloads, disregarding any range ending before EOF.

WebKit on iOS and OS X uses partial downloads when fetching media
files. Previously, only MP3 attachments could play directly in the
browser, reported as a live stream, but with this change, all
supported media formats should render as expected.

Tested using cURL by verifying that partial downloads give exactly the
same results compared to Apache.

PHPBB3-14774
---
 phpBB/includes/functions_download.php | 98 ++++++++++++++++++++---------------
 1 file changed, 55 insertions(+), 43 deletions(-)

(limited to 'phpBB/includes/functions_download.php')

diff --git a/phpBB/includes/functions_download.php b/phpBB/includes/functions_download.php
index 2c6f62227c..78ccebf276 100644
--- a/phpBB/includes/functions_download.php
+++ b/phpBB/includes/functions_download.php
@@ -254,11 +254,21 @@ function send_file_to_browser($attachment, $upload_dir, $category)
 				send_status_line(206, 'Partial Content');
 				header('Content-Range: bytes ' . $range['byte_pos_start'] . '-' . $range['byte_pos_end'] . '/' . $range['bytes_total']);
 				header('Content-Length: ' . $range['bytes_requested']);
-			}
 
-			while (!feof($fp))
+				// First read chunks
+				while (!feof($fp) && ftell($fp) < $range['byte_pos_end'] - 8192)
+				{
+					echo fread($fp, 8192);
+				}
+				// Then, read the remainder
+				echo fread($fp, $range['bytes_requested'] % 8192);
+			}
+			else
 			{
-				echo fread($fp, 8192);
+				while (!feof($fp))
+				{
+					echo fread($fp, 8192);
+				}
 			}
 			fclose($fp);
 		}
@@ -529,6 +539,9 @@ function phpbb_find_range_request()
 */
 function phpbb_parse_range_request($request_array, $filesize)
 {
+	$first_byte_pos	= -1;
+	$last_byte_pos	= -1;
+
 	// Go through all ranges
 	foreach ($request_array as $range_string)
 	{
@@ -540,62 +553,61 @@ function phpbb_parse_range_request($request_array, $filesize)
 			continue;
 		}
 
+		// Substitute defaults
 		if ($range[0] === '')
 		{
-			// Return last $range[1] bytes.
-
-			if (!$range[1])
-			{
-				continue;
-			}
+			$range[0] = 0;
+		}
 
-			if ($range[1] >= $filesize)
-			{
-				return false;
-			}
+		if ($range[1] === '')
+		{
+			$range[1] = $filesize - 1;
+		}
 
-			$first_byte_pos	= $filesize - (int) $range[1];
-			$last_byte_pos	= $filesize - 1;
+		if ($last_byte_pos >= 0 && $last_byte_pos + 1 != $range[0])
+		{
+			// We only support contiguous ranges, no multipart stuff :(
+			return false;
 		}
-		else
+
+		if ($range[1] && $range[1] < $range[0])
 		{
-			// Return bytes from $range[0] to $range[1]
+			// The requested range contains 0 bytes.
+			continue;
+		}
 
+		// Return bytes from $range[0] to $range[1]
+		if ($first_byte_pos < 0)
+		{
 			$first_byte_pos	= (int) $range[0];
-			$last_byte_pos	= (int) $range[1];
-
-			if ($last_byte_pos && $last_byte_pos < $first_byte_pos)
-			{
-				// The requested range contains 0 bytes.
-				continue;
-			}
+		}
 
-			if ($first_byte_pos >= $filesize)
-			{
-				// Requested range not satisfiable
-				return false;
-			}
+		$last_byte_pos	= (int) $range[1];
 
-			// Adjust last-byte-pos if it is absent or greater than the content.
-			if ($range[1] === '' || $last_byte_pos >= $filesize)
-			{
-				$last_byte_pos = $filesize - 1;
-			}
+		if ($first_byte_pos >= $filesize)
+		{
+			// Requested range not satisfiable
+			return false;
 		}
 
-		// We currently do not support range requests that end before the end of the file
-		if ($last_byte_pos != $filesize - 1)
+		// Adjust last-byte-pos if it is absent or greater than the content.
+		if ($range[1] === '' || $last_byte_pos >= $filesize)
 		{
-			continue;
+			$last_byte_pos = $filesize - 1;
 		}
+	}
 
-		return array(
-			'byte_pos_start'	=> $first_byte_pos,
-			'byte_pos_end'		=> $last_byte_pos,
-			'bytes_requested'	=> $last_byte_pos - $first_byte_pos + 1,
-			'bytes_total'		=> $filesize,
-		);
+	if ($first_byte_pos < 0 || $last_byte_pos < 0)
+	{
+		return false;
 	}
+
+	return array(
+		'byte_pos_start'	=> $first_byte_pos,
+		'byte_pos_end'		=> $last_byte_pos,
+		'bytes_requested'	=> $last_byte_pos - $first_byte_pos + 1,
+		'bytes_total'		=> $filesize,
+	);
 }
 
 /**
-- 
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