[Xcb] [PATCH libxcb 5/6] generator: sumof with nested expression

[Christian Linhart]

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);
---
 src/c_client.py | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/c_client.py b/src/c_client.py
index 6b694d5..6169175 100644
--- a/src/c_client.py
+++ b/src/c_client.py
@@ -4,14 +4,15 @@ from os.path import basename
 from functools import reduce
 import getopt
 import os
 import sys
 import errno
 import time
 import re
+import copy
 
 # Jump to the bottom of this file for the main routine
 
 # Some hacks to make the API more readable, and to keep backwards compability
 _cname_re = re.compile('([A-Z0-9][a-z]+|[A-Z0-9]+(?![a-z])|[a-z]+)')
 _cname_special_cases = {'DECnet':'decnet'}
 
@@ -1629,15 +1630,38 @@ def _c_accessor_get_expr(expr, field_mapping):
         _c_pre.code( "%s = %s;", lengthvar, c_length_func )
         _c_pre.code( "%s = 0;", sumvar )
         _c_pre.code( "%s = %s;", listvar, list_name )
         _c_pre.code(
             "for ( %s = 0; %s < %s; %s++) {",
            loopvar, loopvar, lengthvar, loopvar )
         _c_pre.indent()
-        _c_pre.code( "%s += *%s;", sumvar, listvar )
+
+        if expr.rhs == None:
+            _c_pre.code( "%s += *%s;", sumvar, listvar )
+        else:
+            #sumof has a nested expression which
+            #has to be evaluated in the context of this list element
+
+            #field mapping for the subexpression needs to include
+            #the fields of the list-member type
+            scoped_field_mapping = field_mapping.copy()
+            scoped_field_mapping.update(
+                _c_helper_field_mapping(
+                    field.type.member,
+                    [( listvar, '', field.type.member )] ) )
+
+            #cause pre-code of the subexpression be added right here
+            _c_pre.end()
+            #compute the subexpression
+            rhs_expr_str = _c_accessor_get_expr(expr.rhs, scoped_field_mapping)
+            #resume with our code
+            _c_pre.start()
+            #output the summation expression
+            _c_pre.code( "%s += %s;", sumvar, rhs_expr_str )
+
         _c_pre.code( "%s++;", listvar );
         _c_pre.pop_indent()
         _c_pre.code( "}" )
         _c_pre.code( "/* sumof end. Result is in %s */", sumvar )
         _c_pre.end()
         return sumvar;
         #return 'xcb_sumof(%s, %s)' % (list_name, c_length_func)
-- 
2.0.1