winhttp: WinHttpQueryDataAvailable should do a blocking read if more data is expected.

dlls/winhttp/net.c

@@ -464,11 +464,7 @@ BOOL netconn_query_data_available( netconn_t *conn, DWORD *available )
         return TRUE;
     }
 #ifdef FIONREAD
-    if (!(ret = ioctl( conn->socket, FIONREAD, &unread )))
-    {
-        TRACE("%d bytes of queued, but unread data\n", unread);
-        *available += unread;
-    }
+    if (!(ret = ioctl( conn->socket, FIONREAD, &unread ))) *available = unread;
 #endif
     return TRUE;
 }

dlls/winhttp/request.c

@@ -1238,7 +1238,26 @@ static BOOL query_data( request_t *request, LPDWORD available, BOOL async )
     BOOL ret;
     DWORD num_bytes;
 
-    ret = netconn_query_data_available( &request->netconn, &num_bytes );
+    if ((ret = netconn_query_data_available( &request->netconn, &num_bytes )))
+    {
+        if (request->content_read < request->content_length)
+        {
+            if (!num_bytes)
+            {
+                char buffer[4096];
+                size_t to_read = min( sizeof(buffer), request->content_length - request->content_read );
+
+                ret = netconn_recv( &request->netconn, buffer, to_read, MSG_PEEK, (int *)&num_bytes );
+                if (ret && !num_bytes) WARN("expected more data to be available\n");
+            }
+        }
+        else if (num_bytes)
+        {
+            WARN("extra data available %u\n", num_bytes);
+            ret = FALSE;
+        }
+    }
+    TRACE("%u bytes available\n", num_bytes);
 
     if (async)
     {