generator: sumof with nested expression

generator: sumof with nested expression

Support sumof with a nested expression.
The nested expression is computed for every list-element
and the result of the computation is added to the sum.

This way, sumof can be applied to a list of structs,
and, e.g., compute the sum of a specific field of that struct.

example:
<struct name="SumofTest_Element">
   <field type="CARD16" name="foo" />
   <field type="CARD16" name="bar" />
</struct>

<struct name="SumofTest_FieldAccess">
   <field type="CARD32" name="len" />
   <list type="SumofTest_Element" name="mylist1">
	   <fieldref>len</fieldref>
   </list>
   <list type="CARD16" name="mylist2">
	<sumof ref="mylist1">
		<fieldref>bar</fieldref>
	</sumof>
   </list>
</struct>

generated tmpvar:
    int xcb_pre_tmp_1; /* sumof length */
    int xcb_pre_tmp_2; /* sumof loop counter */
    int64_t xcb_pre_tmp_3; /* sumof sum */
    const xcb_input_sumof_test_element_t* xcb_pre_tmp_4; /* sumof list ptr */

generated code:
    /* mylist2 */
    /* sumof start */
    xcb_pre_tmp_1 = _aux->len;
    xcb_pre_tmp_3 = 0;
    xcb_pre_tmp_4 = xcb_input_sumof_test_field_access_mylist_1(_aux);
    for ( xcb_pre_tmp_2 = 0; xcb_pre_tmp_2 < xcb_pre_tmp_1; xcb_pre_tmp_2++) {
        xcb_pre_tmp_3 += xcb_pre_tmp_4->bar;
        xcb_pre_tmp_4++;
    }
    /* sumof end. Result is in xcb_pre_tmp_3 */
    xcb_block_len += xcb_pre_tmp_3 * sizeof(uint16_t);

changes for V2 of this patch:
* explicitely set the member access operator in the prefix-tuple
  passed to function _c_helper_field_mapping.
  This enables us to simplify function "_c_helper_absolute_name"
  (which will be renamed "_c_helper_fieldaccess_expr" soon)

V3: Changed style and formatting according to suggestions from Ran Benita

Signed-off-by: Christian Linhart <chris@DemoRecorder.com>
Reviewed-by: Ran Benita <ran234@gmail.com>
Message-ID: <54562798.8040500@DemoRecorder.com>
Patch-Thread-Subject: [Xcb] [PATCHSET] ListInputDevices revision 2
Patch-Set: ListInputDevices
Patch-Number: libxcb 5/9
Patch-Version: V3