efl_io_copier: add flush method.

This method will force a read-write cycle and returns if it's fully
done or not. It may be used to force data to be written before a
handle is deleted (when one can't wait for the data to be written
asynchronously).

src/lib/ecore/efl_io_copier.c

@@ -704,6 +704,43 @@ _efl_io_copier_inactivity_timeout_get(Eo *o EINA_UNUSED, Efl_Io_Copier_Data *pd)
    return pd->inactivity_timeout;
 }
 
+EOLIAN static Eina_Bool
+_efl_io_copier_flush(Eo *o, Efl_Io_Copier_Data *pd)
+{
+   uint64_t old_read = pd->progress.read;
+   uint64_t old_written = pd->progress.written;
+   uint64_t old_total = pd->progress.total;
+
+   _COPIER_DBG(o, pd);
+
+   if (pd->source && !efl_io_reader_eos_get(pd->source))
+     _efl_io_copier_read(o, pd);
+
+   if (pd->destination)
+     _efl_io_copier_write(o, pd);
+
+   if ((old_read != pd->progress.read) ||
+       (old_written != pd->progress.written) ||
+       (old_total != pd->progress.total))
+     {
+        efl_event_callback_call(o, EFL_IO_COPIER_EVENT_PROGRESS, NULL);
+        _efl_io_copier_inactivity_timeout_reschedule(o, pd);
+     }
+
+   if (!pd->source || efl_io_reader_eos_get(pd->source))
+     {
+        if ((!pd->done) &&
+            ((!pd->destination) || (eina_binbuf_length_get(pd->buf) == 0)))
+          {
+             pd->done = EINA_TRUE;
+             if (pd->inactivity_timer) efl_future_cancel(pd->inactivity_timer);
+             efl_event_callback_call(o, EFL_IO_COPIER_EVENT_DONE, NULL);
+          }
+     }
+
+   return pd->done;
+}
+
 EOLIAN static Eo *
 _efl_io_copier_efl_object_constructor(Eo *o, Efl_Io_Copier_Data *pd)
 {

src/lib/ecore/efl_io_copier.eo

@@ -112,6 +112,31 @@ class Efl.Io.Copier (Efl.Loop_User, Efl.Io.Closer) {
            ]]
            return: free(own(ptr(Eina.Binbuf)), eina_binbuf_free) @warn_unused; [[Binbuf]]
         }
+
+        flush {
+            [[Forces reading from source and writing to destination.
+
+              This executes a single read->write cycle, if more data
+              could be read from source (ie: not EOS) or not all data
+              was written to destination, then $false is
+              returned. Then to forcefully drain source and write all
+              contents to destination, use in a loop until it returns
+              $true.
+
+              The return value matches "done" event, that is, when
+              $true is returned, the "done" event is emitted.
+
+              This function may also emit "progress" and "error"
+              events.
+
+              \@note this function may block the main loop execution
+              until operations complete! This is bad for usability, as
+              user interface or other operations may freeze. A better
+              approach is to operate asynchronously and wait for
+              "done" event.
+            ]]
+            return: bool(true);
+        }
     }
 
     events {