demux: stop setting dummy stream on demux_close_stream()

Demuxers can call demux_close_stream() to close the underlying stream if
it's not needed anymore. (Useful to release "heavy" resources like FDs
and sockets. Plus merely keeping a file open can have visible side
effects such as inability to unmount a filesystem or, on Windows, to do
anything with the file.)

Until now, this set demuxer->stream to a dummy stream, because most code
used to assume that the stream field is non-NULL. But this requirement
disappeared (in some cases, the stream field is already NULL), so stop
doing that. demux_lavf.c, one of the demuxers which calls this function,
still had some of this, though.

2 files changed, 9 insertions, 7 deletions

diff --git a/demux/demux.c b/demux/demux.c
index 1bf0277873..c0b0c2fb65 100644
--- a/demux/demux.c
+++ b/demux/demux.c
@@ -3104,7 +3104,6 @@ static void demux_init_cuesheet(struct demuxer *demuxer)
 // Calling this after opening was completed is not allowed. Also, if opening
 // failed, this must not be called (or trying another demuxer would fail).
 // Useful so that e.g. subtitles don't keep the file or socket open.
-// Replaces it with a dummy stream for dumb reasons.
 // If there's ever the situation where we can't allow the demuxer to close
 // the stream, this function could ignore the request.
 void demux_close_stream(struct demuxer *demuxer)
@@ -3117,9 +3116,8 @@ void demux_close_stream(struct demuxer *demuxer)
 
     MP_VERBOSE(demuxer, "demuxer read all data; closing stream\n");
     free_stream(demuxer->stream);
-    demuxer->stream = stream_memory_open(demuxer->global, NULL, 0); // dummy
-    demuxer->stream->cancel = demuxer->cancel;
-    in->d_user->stream = demuxer->stream;
+    demuxer->stream = NULL;
+    in->d_user->stream = NULL;
 }
 
 static void demux_init_ccs(struct demuxer *demuxer, struct demux_opts *opts)
diff --git a/demux/demux_lavf.c b/demux/demux_lavf.c
index 374714b769..c2f6a65395 100644
--- a/demux/demux_lavf.c
+++ b/demux/demux_lavf.c
@@ -290,6 +290,8 @@ static int mp_read(void *opaque, uint8_t *buf, int size)
     struct demuxer *demuxer = opaque;
     lavf_priv_t *priv = demuxer->priv;
     struct stream *stream = priv->stream;
+    if (!stream)
+        return 0;
 
     int ret = stream_read_partial(stream, buf, size);
 
@@ -303,6 +305,8 @@ static int64_t mp_seek(void *opaque, int64_t pos, int whence)
     struct demuxer *demuxer = opaque;
     lavf_priv_t *priv = demuxer->priv;
     struct stream *stream = priv->stream;
+    if (!stream)
+        return -1;
 
     MP_TRACE(demuxer, "mp_seek(%p, %"PRId64", %s)\n", stream, pos,
              whence == SEEK_END ? "end" :
@@ -345,7 +349,7 @@ static int64_t mp_read_seek(void *opaque, int stream_idx, int64_t ts, int flags)
         .flags = flags,
     };
 
-    if (stream_control(stream, STREAM_CTRL_AVSEEK, &cmd) == STREAM_OK) {
+    if (stream && stream_control(stream, STREAM_CTRL_AVSEEK, &cmd) == STREAM_OK) {
         stream_drop_buffers(stream);
         return 0;
     }
@@ -1106,7 +1110,7 @@ static int demux_open_lavf(demuxer_t *demuxer, enum demux_check check)
         if (priv->own_stream)
             free_stream(priv->stream);
         priv->own_stream = false;
-        priv->stream = demuxer->stream;
+        priv->stream = NULL;
     }
 
     return 0;
@@ -1227,7 +1231,7 @@ static void demux_seek_lavf(demuxer_t *demuxer, double seek_pts, int flags)
 
     if (flags & SEEK_FACTOR) {
         struct stream *s = priv->stream;
-        int64_t end = stream_get_size(s);
+        int64_t end = s ? stream_get_size(s) : -1;
         if (end > 0 && demuxer->ts_resets_possible &&
             !(priv->avif_flags & AVFMT_NO_BYTE_SEEK))
         {