[Xcb] [PATCH libxcb 4/6] generator: sumof: support any type, generate explicit code

[Christian Linhart]

A sumof-expression now generates explicit code ( for-loop etc )
instead of calling xcb_sumof.

This way, it supports any type which can be added.
Previously, only uint_8 was supported.

Here's an example and the generated code:

xml:
<struct name="SumofTest">
   <field type="CARD32" name="len" />
   <list type="CARD16" name="mylist1">
	   <fieldref>len</fieldref>
   </list>
   <list type="CARD8" name="mylist2">
	   <sumof ref="mylist1"/>
   </list>
</struct>

declaration of tempvars at the start of enclosing function:
    int xcb_pre_tmp_1; /* sumof length */
    int xcb_pre_tmp_2; /* sumof loop counter */
    int64_t xcb_pre_tmp_3; /* sumof sum */
    const uint16_t* xcb_pre_tmp_4; /* sumof list ptr */

code:
    /* mylist2 */
    /* sumof start */
    xcb_pre_tmp_1 = _aux->len;
    xcb_pre_tmp_3 = 0;
    xcb_pre_tmp_4 = xcb_input_sumof_test_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;
        xcb_pre_tmp_4++;
    }
    /* sumof end. Result is in xcb_pre_tmp_3 */
    xcb_block_len += xcb_pre_tmp_3 * sizeof(uint8_t);

This patch is also a preparation for sumof which can access
fields of lists of struct, etc.
---
 src/c_client.py | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/c_client.py b/src/c_client.py
index 193e050..6b694d5 100644
--- a/src/c_client.py
+++ b/src/c_client.py
@@ -1609,15 +1609,42 @@ def _c_accessor_get_expr(expr, field_mapping):
 
         if field is None:
             raise Exception("list field '%s' referenced by sumof not found" % expr.lenfield_name)
         list_name = field_mapping[field.c_field_name][0]
         c_length_func = "%s(%s)" % (field.c_length_name, list_name)
         # note: xcb_sumof() has only been defined for integers
         c_length_func = _c_accessor_get_expr(field.type.expr, field_mapping)
-        return 'xcb_sumof(%s, %s)' % (list_name, c_length_func)
+        #create explicit code for computing the sum.
+        #This works for all C-types which can be added to int64_t with +=
+        _c_pre.start()
+        lengthvar = _c_pre.get_tempvarname()
+        loopvar = _c_pre.get_tempvarname()
+        sumvar = _c_pre.get_tempvarname()
+        listvar = _c_pre.get_tempvarname()
+        _c_pre.tempvar( "int %s; /* sumof length */", lengthvar )
+        _c_pre.tempvar( "int %s; /* sumof loop counter */", loopvar )
+        _c_pre.tempvar( "int64_t %s; /* sumof sum */", sumvar )
+        _c_pre.tempvar(
+             "const %s* %s; /* sumof list ptr */", field.c_field_type, listvar )
+        _c_pre.code( "/* sumof start */" )
+        _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 )
+        _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)
     elif expr.op != None:
         return ('(' + _c_accessor_get_expr(expr.lhs, field_mapping) +
                 ' ' + expr.op + ' ' +
                 _c_accessor_get_expr(expr.rhs, field_mapping) + ')')
     elif expr.bitfield:
         return 'xcb_popcount(' + lenexp + ')'
     else:
-- 
2.0.1