stream: remove chaos related to writeable streams

For some reason, we support writeable streams. (Only encoding uses that,
and the use of it looks messy enough that I want to replace it with FILE
or avio today.)

It's a chaos: most streams do not actually check the mode parameter like
they should. Simplify it, and let streams signal availability of write
mode by setting a flag in the stream info struct.

1 files changed, 8 insertions, 2 deletions

diff --git a/stream/stream.c b/stream/stream.c
index 3ea4d475b7..baee62221f 100644
--- a/stream/stream.c
+++ b/stream/stream.c
@@ -289,6 +289,13 @@ static int open_internal(const stream_info_t *sinfo, struct stream *underlying,
     s->path = talloc_strdup(s, path);
     s->source = underlying;
     s->allow_caching = true;
+    s->mode = flags & (STREAM_READ | STREAM_WRITE);
+
+    if ((s->mode & STREAM_WRITE) && !sinfo->can_write) {
+        MP_ERR(s, "No write access implemented.\n");
+        talloc_free(s);
+        return STREAM_ERROR;
+    }
 
     // Parse options
     if (sinfo->priv_size) {
@@ -306,8 +313,7 @@ static int open_internal(const stream_info_t *sinfo, struct stream *underlying,
         }
     }
 
-    s->mode = flags & (STREAM_READ | STREAM_WRITE);
-    int r = sinfo->open(s, s->mode);
+    int r = sinfo->open(s);
     if (r != STREAM_OK) {
         talloc_free(s);
         return r;