file_fill_buffer: set offset (bug fix) [patch from Harald Anlauf].

ChangeLog

@@ -3,6 +3,10 @@
         * using CGRIBEX library version 1.8.0
 	* Version 1.8.1 released
 
+2017-04-12  Uwe Schulzweida
+
+	* file_fill_buffer: set offset (bug fix) [patch from Harald Anlauf]
+
 2017-04-10  Uwe Schulzweida
 
 	* gribapi: use keys iScansNegatively and jScansPositively

src/file.c

@@ -945,6 +945,8 @@ int file_fill_buffer(bfile_t *fileptr)
 	SysError("lseek error at pos %ld file %s", (long) fileptr->bufferPos, fileptr->name);
 
       nread = read(fd, fileptr->buffer, fileptr->bufferSize);
+
+      if ( nread > 0 ) offset = fileptr->position - fileptr->bufferPos;
     }
 
   if ( nread <= 0 )