lavf/avio: add avio_accept and avio_handshake

Signed-off-by: Stephan Holljes <klaxa1337@googlemail.com>

libavformat/avio.h

@@ -648,4 +648,33 @@ struct AVBPrint;
  */
 int avio_read_to_bprint(AVIOContext *h, struct AVBPrint *pb, size_t max_size);
 
+/**
+ * Accept and allocate a client context on a server context.
+ * @param  s the server context
+ * @param  c the client context, must be unallocated
+ * @return   >= 0 on success or a negative value corresponding
+ *           to an AVERROR on failure
+ */
+int avio_accept(AVIOContext *s, AVIOContext **c);
+
+/**
+ * Perform one step of the protocol handshake to accept a new client.
+ * This function must be called on a client returned by avio_accept() before
+ * using it as a read/write context.
+ * It is separate from avio_accept() because it may block.
+ * A step of the handshake is defined by places where the application may
+ * decide to change the proceedings.
+ * For example, on a protocol with a request header and a reply header, each
+ * one can constitute a step because the application may use the parameters
+ * from the request to change parameters in the reply; or each individual
+ * chunk of the request can constitute a step.
+ * If the handshake is already finished, avio_handshake() does nothing and
+ * returns 0 immediately.
+ *
+ * @param  c the client context to perform the handshake on
+ * @return   0   on a complete and successful handshake
+ *           > 0 if the handshake progressed, but is not complete
+ *           < 0 for an AVERROR code
+ */
+int avio_handshake(AVIOContext *c);
 #endif /* AVFORMAT_AVIO_H */

libavformat/aviobuf.c

@@ -1021,6 +1021,23 @@ int avio_read_to_bprint(AVIOContext *h, AVBPrint *pb, size_t max_size)
     return 0;
 }
 
+int avio_accept(AVIOContext *s, AVIOContext **c)
+{
+    int ret;
+    URLContext *sc = s->opaque;
+    URLContext *cc = NULL;
+    ret = ffurl_accept(sc, &cc);
+    if (ret < 0)
+        return ret;
+    return ffio_fdopen(c, cc);
+}
+
+int avio_handshake(AVIOContext *c)
+{
+    URLContext *cc = c->opaque;
+    return ffurl_handshake(cc);
+}
+
 /* output in a dynamic buffer */
 
 typedef struct DynBuffer {