Make url_read_complete retry on EAGAIN and return how much data it read

if it reached EOF, making it useful in more cases.

Originally committed as revision 21393 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/avio.c

@@ -156,8 +156,10 @@ int url_read_complete(URLContext *h, unsigned char *buf, int size)
     len = 0;
     while (len < size) {
         ret = url_read(h, buf+len, size-len);
-        if (ret < 1)
+        if (ret == AVERROR(EAGAIN)) {
-            return ret;
+            ret = 0;
+        } else if (ret < 1)
+            return ret < 0 ? ret : len;
         len += ret;
     }
     return len;

libavformat/avio.h

@@ -69,6 +69,14 @@ int url_open_protocol (URLContext **puc, struct URLProtocol *up,
                        const char *filename, int flags);
 int url_open(URLContext **h, const char *filename, int flags);
 int url_read(URLContext *h, unsigned char *buf, int size);
+/**
+ * Read as many bytes as possible (up to size), calling the
+ * read function multiple times if necessary.
+ * Will also retry if the read function returns AVERROR(EAGAIN).
+ * This makes special short-read handling in applications
+ * unnecessary, if the return value is < size then it is
+ * certain there was either an error or the end of file was reached.
+ */
 int url_read_complete(URLContext *h, unsigned char *buf, int size);
 int url_write(URLContext *h, unsigned char *buf, int size);
 int64_t url_seek(URLContext *h, int64_t pos, int whence);