lavf: make avio_read_partial() public

Main use-case is proxying avio through a foreign I/O layer and a custom
AVIO context, without losing latency and performance characteristics.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:     2017-03-23
 
 API changes, most recent first:
 
+2016-xx-xx - xxxxxxx - lavf 58.1.0 - avio.h
+  Add avio_read_partial().
+
 2017-xx-xx - xxxxxxx - lavu 56.4.0 - imgutils.h
   Add av_image_fill_black().
 

libavformat/avio.h

@@ -331,6 +331,15 @@ void avio_flush(AVIOContext *s);
  */
 int avio_read(AVIOContext *s, unsigned char *buf, int size);
 
+/**
+ * Read size bytes from AVIOContext into buf. Unlike avio_read(), this is allowed
+ * to read fewer bytes than requested. The missing bytes can be read in the next
+ * call. This always tries to read at least 1 byte.
+ * Useful to reduce latency in certain cases.
+ * @return number of bytes read or AVERROR
+ */
+int avio_read_partial(AVIOContext *s, unsigned char *buf, int size);
+
 /**
  * @name Functions for reading from AVIOContext
  * @{

libavformat/avio_internal.h

@@ -53,14 +53,6 @@ int ffio_init_context(AVIOContext *s,
  */
 int ffio_read_indirect(AVIOContext *s, unsigned char *buf, int size, const unsigned char **data);
 
-/**
- * Read size bytes from AVIOContext into buf.
- * This reads at most 1 packet. If that is not enough fewer bytes will be
- * returned.
- * @return number of bytes read or AVERROR
- */
-int ffio_read_partial(AVIOContext *s, unsigned char *buf, int size);
-
 void ffio_fill(AVIOContext *s, int b, int count);
 
 static av_always_inline void ffio_wfourcc(AVIOContext *pb, const uint8_t *s)

libavformat/aviobuf.c

@@ -621,7 +621,7 @@ int ffio_read_indirect(AVIOContext *s, unsigned char *buf, int size, const unsig
     }
 }
 
-int ffio_read_partial(AVIOContext *s, unsigned char *buf, int size)
+int avio_read_partial(AVIOContext *s, unsigned char *buf, int size)
 {
     int len;
 

libavformat/rawdec.c

@@ -42,7 +42,7 @@ int ff_raw_read_partial_packet(AVFormatContext *s, AVPacket *pkt)
 
     pkt->pos= avio_tell(s->pb);
     pkt->stream_index = 0;
-    ret = ffio_read_partial(s->pb, pkt->data, size);
+    ret = avio_read_partial(s->pb, pkt->data, size);
     if (ret < 0) {
         av_packet_unref(pkt);
         return ret;

libavformat/rtsp.c

@@ -2077,7 +2077,7 @@ static int read_packet(AVFormatContext *s,
             wait_end && wait_end < av_gettime_relative())
             len = AVERROR(EAGAIN);
         else
-            len = ffio_read_partial(s->pb, rt->recvbuf, RECVBUF_SIZE);
+            len = avio_read_partial(s->pb, rt->recvbuf, RECVBUF_SIZE);
         len = pick_stream(s, rtsp_st, rt->recvbuf, len);
         if (len > 0 && (*rtsp_st)->transport_priv && rt->transport == RTSP_TRANSPORT_RTP)
             ff_rtp_check_and_send_back_rr((*rtsp_st)->transport_priv, NULL, s->pb, len);

libavformat/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 58
-#define LIBAVFORMAT_VERSION_MINOR  0
+#define LIBAVFORMAT_VERSION_MINOR  1
 #define LIBAVFORMAT_VERSION_MICRO  0
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \