stream: add effective_url, the url after redirects

stream_lavf takes it from the location option of the protocol and
stream_curl from CURLINFO_EFFECTIVE_URL.

stream/stream.h

@@ -243,6 +243,7 @@ typedef struct stream {
     void *priv; // used for DVD, TV, RTSP etc
     char *url;  // filename/url (possibly including protocol prefix)
     char *path; // filename (url without protocol prefix)
+    char *effective_url; // url after redirects, if known
     char *mime_type; // when HTTP streaming is used
     char *server_filename; // file name reported by the server, if any
     char *demuxer; // request demuxer to be used

stream/stream_curl.c

@@ -167,7 +167,6 @@ struct priv {
     CURL *curl;
     struct curl_slist *headers;
     char *url;
-    const char *effective_url;
     const struct curl_scheme *scheme;
 
     // Stream parameters
@@ -1191,7 +1190,7 @@ static int curl_open(stream_t *s, const struct stream_open_args *args)
 
     const char *effective_url = NULL;
     curl_easy_getinfo(p->curl, CURLINFO_EFFECTIVE_URL, &effective_url);
-    p->effective_url = effective_url ? effective_url : p->url;
+    s->effective_url = talloc_strdup(s, effective_url);
 
     s->seekable = p->seekable;
     s->is_network = true;
@@ -1387,7 +1386,7 @@ static int open_curl_transport(struct demuxer *demuxer, AVIOContext **pb_out,
     c->av_class = &curl_avio_cookie_class;
     c->stream = s;
     c->cancel = cancel;
-    c->location = ((struct priv *)s->priv)->effective_url;
+    c->location = s->effective_url ? s->effective_url : s->url;
 
     void *buffer = av_malloc(64 * 1024);
     if (!buffer) {

stream/stream_lavf.c

@@ -411,6 +411,12 @@ static int open_f(stream_t *stream)
             stream->mime_type = talloc_strdup(stream, mt);
             av_free(mt);
         }
+        uint8_t *location = NULL;
+        if (av_opt_get(avio, "location", AV_OPT_SEARCH_CHILDREN, &location) >= 0) {
+            if (*location)
+                stream->effective_url = talloc_strdup(stream, location);
+            av_free(location);
+        }
     }
 
     stream->priv = avio;