main/file: Add the ability to play media in the media cache

This patch allows applications/APIs that access media through the core file
APIs to play media in the media cache. Prior to determining if a 'filename'
exists, the filename is passed to the media cache's retrieve API call. If
that call succeeds, the local file specified passed back by the API is
opened for streaming. When used in this fashion, the 'filename' is actually
a URI that the media cache process and understand.

ASTERISK-25654 #close

Change-Id: I73b6e2e90c3e91b8500581c45cdf9c0dc785f5f0

CHANGES

@@ -31,6 +31,21 @@ ConfBridge
    - record_command: a command to execute when recording is finished
    Note that these options may also be with the CONFBRIDGE function.
 
+ControlPlayback
+------------------
+ * Remote files can now be retrieved and played back. See the Playback
+   dialplan application for more details.
+
+Playback
+------------------
+ * Remote files can now be retrieved and played back via the Playback and other
+   media playback dialplan applications. This is done by directly providing
+   the URL to play to the dialplan application:
+     same => n,Playback(http://1.1.1.1/howler-monkeys-fl.wav)
+   Note that unlike 'normal' media files, the entire URI to the file must be
+   provided, including the file extension. Currently, on HTTP and HTTPS URI
+   schemes are supported.
+
 SMS
 ------------------
  * Added the 'n' option, which prevents the SMS from being written to the log
@@ -132,6 +147,17 @@ Core
    of '[json]' can be set, e.g.,
       full => [json]debug,verbose,notice,warning,error
 
+ * The core now supports a 'media cache', which stores temporary media files
+   retrieved from external sources. CLI commands have been added to manipulate
+   and display the cached files, including:
+   - 'media cache show <all>' - show all cached media files, or details about
+     one particular cached media file
+   - 'media cache refresh <item>' - force a refresh of a particular media file
+     in the cache
+   - 'media cache delete <item>' - remove an item from the cache
+   - 'media cache create <uri>' - retrieve a URI and store it in the cache
+
+
 Functions
 ------------------
 

main/file.c

@@ -54,6 +54,7 @@ ASTERISK_REGISTER_FILE()
 #include "asterisk/stasis.h"
 #include "asterisk/json.h"
 #include "asterisk/stasis_system.h"
+#include "asterisk/media_cache.h"
 
 /*! \brief
  * The following variable controls the layout of localized sound files.
@@ -644,6 +645,10 @@ static int fileexists_test(const char *filename, const char *fmt, const char *la
 		return 0;
 	}
 
+	if (!ast_media_cache_retrieve(filename, NULL, buf, buflen)) {
+		return filehelper(buf, result_cap, NULL, ACTION_EXISTS);
+	}
+
 	if (ast_language_is_prefix && !is_absolute_path(filename)) { /* new layout */
 		if (lang) {
 			snprintf(buf, buflen, "%s/%s", lang, filename);