Index: includes/file.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/file.inc,v
retrieving revision 1.238
diff -u -p -r1.238 file.inc
--- includes/file.inc	18 Oct 2010 01:00:39 -0000	1.238
+++ includes/file.inc	18 Oct 2010 18:49:47 -0000
@@ -90,12 +90,37 @@ define('FILE_STATUS_PERMANENT', 1);
  *
  * A stream is referenced as "scheme://target".
  *
+ * The optional $filter parameter can be used to retrieve only the stream
+ * wrappers that are appropriate for particular usage. For example, this returns
+ * only stream wrappers that use local file storage:
+ * @code
+ *   $local_stream_wrappers = file_get_stream_wrappers(STEAM_WRAPPERS_LOCAL);
+ * @endcode
+ *
+ * The $filter parameter can only filter to types containing a particular flag.
+ * In some cases, you may want to filter to types that do not contain a
+ * particular flag. For example, you may want to retrieve all stream wrappers
+ * that are not writable, or all stream wrappers that are not local. PHP's
+ * array_diff_key() function can be used to help with this. For example, this
+ * returns only stream wrappers that do not use local file storage:
+ * @code
+ *   $remote_stream_wrappers = array_diff_key(file_get_stream_wrappers(STREAM_WRAPPERS_ALL), file_get_stream_wrappers(STEAM_WRAPPERS_LOCAL));
+ * @endcode
+ *
  * @param $filter
- *  Optionally filter out all types except these.  Defaults to
- *  STREAM_WRAPPERS_ALL, which returns all registered stream wrappers.
+ *   (Optional) Filters out all types except those with an on bit for each on
+ *   bit in $filter. For example, if $filter is STREAM_WRAPPERS_WRITE_VISIBLE,
+ *   which is equal to (STREAM_WRAPPERS_READ | STREAM_WRAPPERS_WRITE |
+ *   STREAM_WRAPPERS_VISIBLE), then only stream wrappers with all three of these
+ *   bits set are returned. Defaults to STREAM_WRAPPERS_ALL, which returns all
+ *   registered stream wrappers.
  *
  * @return
- *   Returns the entire Drupal stream wrapper registry.
+ *   An array keyed by scheme, with values containing an array of information
+ *   about the stream wrapper, as returned by hook_stream_wrappers(). If $filter
+ *   is omitted or set to STREAM_WRAPPERS_ALL, the entire Drupal stream wrapper
+ *   registry is returned. Otherwise only the stream wrappers whose 'type'
+ *   bitmask has an on bit for each bit specified in $filter are returned.
  *
  * @see hook_stream_wrappers()
  * @see hook_stream_wrappers_alter()
@@ -122,11 +147,11 @@ function file_get_stream_wrappers($filte
         else {
           $wrappers[$scheme]['override'] = FALSE;
         }
-        if (($info['type'] & STREAM_WRAPPERS_REMOTE) == STREAM_WRAPPERS_REMOTE) {
-          stream_wrapper_register($scheme, $info['class'], STREAM_IS_URL);
+        if (($info['type'] & STREAM_WRAPPERS_LOCAL) == STREAM_WRAPPERS_LOCAL) {
+          stream_wrapper_register($scheme, $info['class']);
         }
         else {
-          stream_wrapper_register($scheme, $info['class']);
+          stream_wrapper_register($scheme, $info['class'], STREAM_IS_URL);
         }
       }
       // Pre-populate the static cache with the filters most typically used.
@@ -141,7 +166,7 @@ function file_get_stream_wrappers($filte
     $wrappers_storage[$filter] = array();
     foreach ($wrappers_storage[STREAM_WRAPPERS_ALL] as $scheme => $info) {
       // Bit-wise filter.
-      if ($info['type'] & $filter == $filter) {
+      if (($info['type'] & $filter) == $filter) {
         $wrappers_storage[$filter][$scheme] = $info;
       }
     }
Index: includes/stream_wrappers.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/stream_wrappers.inc,v
retrieving revision 1.20
diff -u -p -r1.20 stream_wrappers.inc
--- includes/stream_wrappers.inc	17 Aug 2010 22:05:22 -0000	1.20
+++ includes/stream_wrappers.inc	18 Oct 2010 18:49:47 -0000
@@ -22,6 +22,9 @@
 
 /**
  * Stream wrapper bit flags that are the basis for composite types.
+ *
+ * Note that 0x0002 is skipped, because it was the value of a constant that has
+ * since been removed.
  */
 
 /**
@@ -35,11 +38,6 @@ define('STREAM_WRAPPERS_ALL', 0x0000);
 define('STREAM_WRAPPERS_LOCAL', 0x0001);
 
 /**
- * Stream wrapper bit flag -- refers to a remote filesystem location.
- */
-define('STREAM_WRAPPERS_REMOTE', 0x0002);
-
-/**
  * Stream wrapper bit flag -- wrapper is readable (almost always true).
  */
 define('STREAM_WRAPPERS_READ', 0x0004);
@@ -65,6 +63,11 @@ define('STREAM_WRAPPERS_VISIBLE', 0x0010
 define('STREAM_WRAPPERS_HIDDEN', STREAM_WRAPPERS_READ | STREAM_WRAPPERS_WRITE);
 
 /**
+ * Stream wrapper type flag -- hidden, readable and writeable using local files.
+ */
+define('STREAM_WRAPPERS_LOCAL_HIDDEN', STREAM_WRAPPERS_LOCAL | STREAM_WRAPPERS_HIDDEN);
+
+/**
  * Stream wrapper type flag -- visible, readable and writeable.
  */
 define('STREAM_WRAPPERS_WRITE_VISIBLE', STREAM_WRAPPERS_READ | STREAM_WRAPPERS_WRITE | STREAM_WRAPPERS_VISIBLE);
@@ -75,9 +78,18 @@ define('STREAM_WRAPPERS_WRITE_VISIBLE', 
 define('STREAM_WRAPPERS_READ_VISIBLE', STREAM_WRAPPERS_READ | STREAM_WRAPPERS_VISIBLE);
 
 /**
+ * Stream wrapper type flag -- the default when 'type' is omitted from
+ * hook_stream_wrappers(). This does not include STREAM_WRAPPERS_LOCAL,
+ * because PHP grants a greater trust level to local files (for example, they
+ * can be used in an "include" statement, regardless of the "allow_url_include"
+ * setting), so stream wrappers need to explicitly opt-in to this.
+ */
+define('STREAM_WRAPPERS_NORMAL', STREAM_WRAPPERS_WRITE_VISIBLE);
+
+/**
  * Stream wrapper type flag -- visible, readable and writeable using local files.
  */
-define('STREAM_WRAPPERS_NORMAL', STREAM_WRAPPERS_LOCAL | STREAM_WRAPPERS_WRITE_VISIBLE);
+define('STREAM_WRAPPERS_LOCAL_NORMAL', STREAM_WRAPPERS_LOCAL | STREAM_WRAPPERS_NORMAL);
 
 /**
  * Generic PHP stream wrapper interface.
Index: modules/system/system.api.php
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.api.php,v
retrieving revision 1.201
diff -u -p -r1.201 system.api.php
--- modules/system/system.api.php	18 Oct 2010 01:13:07 -0000	1.201
+++ modules/system/system.api.php	18 Oct 2010 18:49:53 -0000
@@ -2296,9 +2296,13 @@ function hook_modules_uninstalled($modul
  *   - 'class' A string specifying the PHP class that implements the
  *     DrupalStreamWrapperInterface interface.
  *   - 'description' A string with a short description of what the wrapper does.
- *   - 'type' A bitmask of flags indicating what type of streams this wrapper
- *     will access - local or remote, readable and/or writeable, etc. Many
- *     shortcut constants are defined in stream_wrappers.inc.
+ *   - 'type' (Optional) A bitmask of flags indicating what type of streams this
+ *     wrapper will access - local or remote, readable and/or writeable, etc.
+ *     Many shortcut constants are defined in stream_wrappers.inc. Defaults to
+ *     STREAM_WRAPPERS_NORMAL which includes all of these bit flags:
+ *     - STREAM_WRAPPERS_READ
+ *     - STREAM_WRAPPERS_WRITE
+ *     - STREAM_WRAPPERS_VISIBLE
  *
  * @see file_get_stream_wrappers()
  * @see hook_stream_wrappers_alter()
@@ -2310,18 +2314,35 @@ function hook_stream_wrappers() {
       'name' => t('Public files'),
       'class' => 'DrupalPublicStreamWrapper',
       'description' => t('Public local files served by the webserver.'),
+      'type' => STREAM_WRAPPERS_LOCAL_NORMAL,
     ),
     'private' => array(
       'name' => t('Private files'),
       'class' => 'DrupalPrivateStreamWrapper',
       'description' => t('Private local files served by Drupal.'),
+      'type' => STREAM_WRAPPERS_LOCAL_NORMAL,
     ),
     'temp' => array(
       'name' => t('Temporary files'),
       'class' => 'DrupalTempStreamWrapper',
       'description' => t('Temporary local files for upload and previews.'),
-      'type' => STREAM_WRAPPERS_HIDDEN,
-    )
+      'type' => STREAM_WRAPPERS_LOCAL_HIDDEN,
+    ),
+    'cdn' => array(
+      'name' => t('Content delivery network files'),
+      'class' => 'MyModuleCDNStreamWrapper',
+      'description' => t('Files served by a content delivery network.'),
+      // 'type' can be omitted to use the default of STREAM_WRAPPERS_NORMAL
+    ),
+    'youtube' => array(
+      'name' => t('YouTube video'),
+      'class' => 'MyModuleYouTubeStreamWrapper',
+      'description' => t('Video streamed from YouTube.'),
+      // A module implementing YouTube integration may decide to support using
+      // the YouTube API for uploading video, but here, we assume that this
+      // particular module only supports playing YouTube video.
+      'type' => STREAM_WRAPPERS_READ_VISIBLE,
+    ),
   );
 }
 
Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.981
diff -u -p -r1.981 system.module
--- modules/system/system.module	15 Oct 2010 04:40:41 -0000	1.981
+++ modules/system/system.module	18 Oct 2010 18:49:53 -0000
@@ -1541,12 +1541,13 @@ function system_stream_wrappers() {
       'name' => t('Public files'),
       'class' => 'DrupalPublicStreamWrapper',
       'description' => t('Public local files served by the webserver.'),
+      'type' => STREAM_WRAPPERS_LOCAL_NORMAL,
     ),
     'temporary' => array(
       'name' => t('Temporary files'),
       'class' => 'DrupalTemporaryStreamWrapper',
       'description' => t('Temporary local files for upload and previews.'),
-      'type' => STREAM_WRAPPERS_HIDDEN,
+      'type' => STREAM_WRAPPERS_LOCAL_HIDDEN,
     ),
   );
 
@@ -1556,6 +1557,7 @@ function system_stream_wrappers() {
       'name' => t('Private files'),
       'class' => 'DrupalPrivateStreamWrapper',
       'description' => t('Private local files served by Drupal.'),
+      'type' => STREAM_WRAPPERS_LOCAL_NORMAL,
     );
   }