Merge branch 'gsoc2010' of git://anongit.freedesktop.org/~chr/libxcb

9 files changed, 1491 insertions, 110 deletions

diff --git a/Makefile.am b/Makefile.am
index ff9dea1..1f88b72 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -58,6 +58,9 @@ endif
 if BUILD_XINPUT
 pkgconfig_DATA += xcb-xinput.pc
 endif
+if BUILD_XKB
+pkgconfig_DATA += xcb-xkb.pc
+endif
 if BUILD_XPRINT
 pkgconfig_DATA += xcb-xprint.pc
 endif
diff --git a/configure.ac b/configure.ac
index 4178989..848310e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -146,6 +146,7 @@ XCB_EXTENSION(XFixes, "yes")
 XCB_EXTENSION(XFree86-DRI, "yes")
 XCB_EXTENSION(Xinerama, "yes")
 XCB_EXTENSION(XInput, "no")
+XCB_EXTENSION(XKB, "no")
 XCB_EXTENSION(Xprint, "yes")
 XCB_EXTENSION(SELinux, "no")
 XCB_EXTENSION(XTest, "yes")
@@ -189,6 +190,7 @@ xcb-xf86dri.pc
 xcb-xfixes.pc
 xcb-xinerama.pc
 xcb-xinput.pc
+xcb-xkb.pc
 xcb-xprint.pc
 xcb-xselinux.pc
 xcb-xtest.pc
diff --git a/doc/xkb_internals b/doc/xkb_internals
new file mode 100644
index 0000000..93c6d01
--- /dev/null
+++ b/doc/xkb_internals
@@ -0,0 +1,49 @@
+
+XKB introduces several uncommon data structures:
+ - switch allows conditional inclusion of fields
+ - several complex objects intermix variable and fixed size fields
+ - lists with a variable number of variable size objects
+
+To handle these objects, a number of new functions is generated:
+ - _serialize() turns a structured object into a byte stream, 
+   (re)ordering or including fields according to the protocol
+ - _unserialize() rewrites data from a buffer into a structured object
+ - _unpack() expands a buffer representing a switch object into 
+   a special structured type, all flags needed to resolve the switch
+   expression have to given as parameters
+ - _sizeof() calculates the size of a serialized object, often by calling
+   _unserialize()/_unpack() internally
+
+The new structured data type for switch is special as it contains fixed 
+and variable size fields. Variable size fields can be accessed via pointers. 
+
+If switch appears in a request, an additional set of request helpers is 
+generated with the suffix _aux or _aux_(un)checked. While the 'common'
+request functions require that switch has been serialized before, the _aux
+variants take the structured data type. They are especially designed to 
+replace certain functions in xcb-util/aux. 
+
+Accessors for switch members need two parameters, where the first is usually
+a pointer to the respective request or reply structure, while the second 
+is a pointer to the unpacked switch data structure. 
+
+Functions from the serialize family that take a double pointer can allocate 
+memory on their own, which is useful if the size of a buffer has to be 
+calculated depending on the data within. These functions call malloc() when 
+the double pointer is given as the address of a pointer that has been 
+initialized to 0. It is the responsibility of the user to free any allocated
+memory. 
+
+Intermixed variable and fixed size fields are an important special case in XKB. 
+The current implementation resolves the issue by reordering the fields before
+sending them on the wire as well as before returning a reply. That means that 
+these objects look like 'common' XCB data types and they can be accessed as such 
+(i.e. fixed size fields directly via the structured type and variable size fields
+via accessors/iterators).  
+
+In case a list with variable size elements needs to be accessed, it is necessary 
+to use iterators. The iterator functions take care of determining the actual 
+object size for each element automatically. 
+
+A small and preliminary set of auxiliary functions is available in xkb_util.c 
+in the check_xkb module.  
diff --git a/doc/xkb_issues b/doc/xkb_issues
new file mode 100644
index 0000000..80efcc1
--- /dev/null
+++ b/doc/xkb_issues
@@ -0,0 +1,38 @@
+
+There are a number of problematic special cases in XKB. The issues 
+mentioned here are at most partly resolved.
+ 
+1. The are several XxxDoodad structures defined in xkb.xml. They are used
+   in a few lists, but in a rather special way: 
+   The struct "CommonDoodad" is supposed to be a rather generic data type, 
+   combining the most basic Doodad fields that are common in all these structures. 
+   All Doodads are encapsulated in a union type simply called "Doodad". 
+   Now this union is used in subsequent list definitions, aiming at a kind of 
+   'polymorphism': From inspection of the protocol and Xlib, the Doodads are to 
+   be discriminated based on their type field.
+   However the special meaning of the type field is not encoded in the protocol. 
+   Furthermore the TextDoodad and the LogoDoodad are variable size types due to
+   some fields of type CountedString16, thereby turning the union into a 
+   possibly variable size type as well. 
+   However, for lists with variable size elements, special sizeof functions are 
+   required. These cannot be autogenerated as it cannot be referred which 
+   Doodad type to use for the union. 
+   Therefore, the Doodad type structures are unsupported at the moment. 
+
+2. There are still some bugs in xkb.xml: Either certain fields are missing
+   that are required by the protocol, or Xlib simply has another understanding
+   of the protocol. 
+
+3. The interface for accessors should be reviewed. 
+
+4. Currently some bitcases carry 'name' attributes. These could be avoided if 
+   the data within would consist of a singe struct field only. 
+
+5. switch could get a 'fixed_size' attribute, so when rewriting valueparam to switch, 
+   an uint32_t * pointer could be used instead of void *. 
+
+6. The automatic inclusion of padding requires some complicated coding in the 
+   generator. This is errorprone and could be avoided if all padding is explicitly
+   given in the protocol definition. For variable size fields that require padding, 
+   the pad tag could get a 'fieldref' attribute. That way padding could be handled
+   a lot easier in the autogenerator. 
\ No newline at end of file
diff --git a/src/Makefile.am b/src/Makefile.am
index f0bdeaa..9b90914 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -168,6 +168,14 @@ libxcb_xinput_la_LIBADD = $(XCB_LIBS)
 nodist_libxcb_xinput_la_SOURCES = xinput.c xinput.h
 endif
 
+EXTSOURCES += xkb.c
+if BUILD_XKB
+lib_LTLIBRARIES += libxcb-xkb.la
+libxcb_xkb_la_LDFLAGS = -version-info 0:0:0 -no-undefined
+libxcb_xkb_la_LIBADD = $(XCB_LIBS)
+nodist_libxcb_xkb_la_SOURCES = xkb.c xkb.h
+endif
+
 EXTSOURCES += xprint.c
 if BUILD_XPRINT
 lib_LTLIBRARIES += libxcb-xprint.la
diff --git a/src/c_client.py b/src/c_client.py
index 4f3b089..26826e4 100755..100644
--- a/src/c_client.py
+++ b/src/c_client.py
@@ -16,6 +16,7 @@ _extension_special_cases = ['XPrint', 'XCMisc', 'BigRequests']
 _cplusplus_annoyances = {'class' : '_class',
                          'new'   : '_new',
                          'delete': '_delete'}
+_c_keywords = {'default' : '_default'}
 
 _hlines = []
 _hlevel = 0
@@ -23,6 +24,12 @@ _clines = []
 _clevel = 0
 _ns = None
 
+# global variable to keep track of serializers and 
+# switch data types due to weird dependencies
+finished_serializers = []
+finished_sizeof = []
+finished_switch = []
+
 def _h(fmt, *args):
     '''
     Writes the given line to the header file.
@@ -81,6 +88,8 @@ def _cpp(str):
     '''
     if str in _cplusplus_annoyances:
         return _cplusplus_annoyances[str]
+    elif str in _c_keywords:
+        return  _c_keywords[str]
     else:
         return str
 
@@ -158,6 +167,7 @@ def c_open(self):
     _h('')
     _h('#include "xcb.h"')
 
+    _c('#include <stdlib.h>')
     _c('#include <string.h>')
     _c('#include <assert.h>')
     _c('#include "xcbext.h"')
@@ -273,7 +283,30 @@ def _c_type_setup(self, name, postfix):
     self.c_reply_type = _t(name + ('reply',))
     self.c_cookie_type = _t(name + ('cookie',))
 
-    if self.is_container:
+    self.need_aux = False
+    self.need_serialize = False
+    self.need_sizeof = False
+
+    self.c_aux_name = _n(name + ('aux',))
+    self.c_aux_checked_name = _n(name + ('aux', 'checked'))
+    self.c_aux_unchecked_name = _n(name + ('aux', 'unchecked'))
+    self.c_serialize_name = _n(name + ('serialize',))
+    self.c_unserialize_name = _n(name + ('unserialize',))
+    self.c_unpack_name = _n(name + ('unpack',))
+    self.c_sizeof_name = _n(name + ('sizeof',))
+
+    # special case: structs where variable size fields are followed by fixed size fields
+    self.var_followed_by_fixed_fields = False
+
+    if self.is_switch:
+        self.need_serialize = True
+        self.c_container = 'struct'
+        for bitcase in self.bitcases:
+            bitcase.c_field_name = _cpp(bitcase.field_name)
+            bitcase_name = bitcase.field_type if bitcase.type.has_name else name
+            _c_type_setup(bitcase.type, bitcase_name, ())
+
+    elif self.is_container:
 
         self.c_container = 'union' if self.is_union else 'struct'
         prev_varsized_field = None
@@ -284,6 +317,8 @@ def _c_type_setup(self, name, postfix):
             _c_type_setup(field.type, field.field_type, ())
             if field.type.is_list:
                 _c_type_setup(field.type.member, field.field_type, ())
+                if (field.type.nmemb is None): 
+                    self.need_sizeof = True
 
             field.c_field_type = _t(field.field_type)
             field.c_field_const_type = ('' if field.type.nmemb == 1 else 'const ') + field.c_field_type
@@ -291,6 +326,19 @@ def _c_type_setup(self, name, postfix):
             field.c_subscript = '[%d]' % field.type.nmemb if (field.type.nmemb > 1) else ''
             field.c_pointer = ' ' if field.type.nmemb == 1 else '*'
 
+            # correct the c_pointer field for variable size non-list types
+            if not field.type.fixed_size() and field.c_pointer == ' ':
+                field.c_pointer = '*'
+            if field.type.is_list and not field.type.member.fixed_size():
+                field.c_pointer = '*'
+
+            if field.type.is_switch:
+                field.c_pointer = '*'
+                field.c_field_const_type = 'const ' + field.c_field_type
+                self.need_aux = True
+            elif not field.type.fixed_size() and not field.type.is_bitcase:
+                self.need_sizeof = True
+
             field.c_iterator_type = _t(field.field_type + ('iterator',))      # xcb_fieldtype_iterator_t
             field.c_iterator_name = _n(name + (field.field_name, 'iterator')) # xcb_container_field_iterator
             field.c_accessor_name = _n(name + (field.field_name,))            # xcb_container_field
@@ -306,10 +354,875 @@ def _c_type_setup(self, name, postfix):
 
             if field.type.fixed_size():
                 prev_varsized_offset += field.type.size
+                # special case: intermixed fixed and variable size fields
+                if prev_varsized_field is not None and not field.type.is_pad and field.wire:
+                    if not self.is_union:
+                        self.need_serialize = True
+                        self.var_followed_by_fixed_fields = True
             else:
                 self.last_varsized_field = field
                 prev_varsized_field = field
-                prev_varsized_offset = 0
+                prev_varsized_offset = 0                    
+
+            if self.var_followed_by_fixed_fields:
+                if field.type.fixed_size():
+                    field.prev_varsized_field = None
+                            
+    if self.need_serialize:
+        # when _unserialize() is wanted, create _sizeof() as well for consistency reasons 
+        self.need_sizeof = True
+
+    # as switch does never appear at toplevel, 
+    # continue here with type construction
+    if self.is_switch:
+        if self.c_type not in finished_switch:
+            finished_switch.append(self.c_type)
+            # special: switch C structs get pointer fields for variable-sized members
+            _c_complex(self)
+            for bitcase in self.bitcases:
+                bitcase_name = bitcase.type.name if bitcase.type.has_name else name
+                _c_accessors(bitcase.type, bitcase_name, bitcase_name)
+                # no list with switch as element, so no call to 
+                # _c_iterator(field.type, field_name) necessary
+
+    if not self.is_bitcase:
+        if self.need_serialize:
+            if self.c_serialize_name not in finished_serializers:
+                finished_serializers.append(self.c_serialize_name)
+                _c_serialize('serialize', self)
+
+                # _unpack() and _unserialize() are only needed for special cases:
+                #   switch -> unpack
+                #   special cases -> unserialize
+                if self.is_switch or self.var_followed_by_fixed_fields:
+                    _c_serialize('unserialize', self)
+                    
+        if self.need_sizeof:
+            if self.c_sizeof_name not in finished_sizeof:
+                finished_sizeof.append(self.c_sizeof_name)
+                _c_serialize('sizeof', self)
+# _c_type_setup()
+
+def _c_helper_absolute_name(prefix, field=None):
+    """
+    turn prefix, which is a list of tuples (name, separator, Type obj) into a string
+    representing a valid name in C (based on the context)
+    if field is not None, append the field name as well
+    """
+    prefix_str = ''
+    for name, sep, obj in prefix:
+        prefix_str += name
+        if '' == sep:
+            sep = '->'
+            if ((obj.is_bitcase and obj.has_name) or     # named bitcase
+                (obj.is_switch and len(obj.parents)>1)):
+                sep = '.'
+        prefix_str += sep
+    if field is not None:
+        prefix_str += _cpp(field.field_name)
+    return prefix_str
+# _c_absolute_name
+    
+def _c_helper_field_mapping(complex_type, prefix, flat=False):
+    """
+    generate absolute names, based on prefix, for all fields starting from complex_type
+    if flat == True, nested complex types are not taken into account
+    """
+    all_fields = {}
+    if complex_type.is_switch:
+        for b in complex_type.bitcases:
+            if b.type.has_name:
+                switch_name, switch_sep, switch_type = prefix[-1]
+                bitcase_prefix = prefix + [(b.type.name[-1], '.', b.type)]
+            else:
+                bitcase_prefix = prefix 
+
+            if (True==flat and not b.type.has_name) or False==flat:
+                all_fields.update(_c_helper_field_mapping(b.type, bitcase_prefix, flat))
+    else:
+        for f in complex_type.fields:
+            fname = _c_helper_absolute_name(prefix, f)
+            if all_fields.has_key(f.field_name):
+                raise Exception("field name %s has been registered before" % f.field_name)
+
+            all_fields[f.field_name] = (fname, f)
+            if f.type.is_container and flat==False:
+                if f.type.is_bitcase and not f.type.has_name:
+                    new_prefix = prefix
+                elif f.type.is_switch and len(f.type.parents)>1:
+                    # nested switch gets another separator
+                    new_prefix = prefix+[(f.c_field_name, '.', f.type)]
+                else:
+                    new_prefix = prefix+[(f.c_field_name, '->', f.type)]
+                all_fields.update(_c_helper_field_mapping(f.type, new_prefix, flat))
+
+    return all_fields
+# _c_field_mapping()
+
+def _c_helper_resolve_field_names (prefix):
+    """
+    get field names for all objects in the prefix array
+    """
+    all_fields = {}
+    tmp_prefix = []
+    # look for fields in the remaining containers
+    for idx, p in enumerate(prefix):
+        name, sep, obj = p
+        if ''==sep:
+            # sep can be preset in prefix, if not, make a sensible guess
+            sep = '.' if (obj.is_switch or obj.is_bitcase) else '->'
+            # exception: 'toplevel' object (switch as well!) always have sep '->'
+            sep = '->' if idx<1 else sep
+        if not obj.is_bitcase or (obj.is_bitcase and obj.has_name):
+            tmp_prefix.append((name, sep, obj))
+        all_fields.update(_c_helper_field_mapping(obj, tmp_prefix, flat=True))
+
+    return all_fields
+# _c_helper_resolve_field_names
+
+def get_expr_fields(self):
+    """
+    get the Fields referenced by switch or list expression 
+    """
+    def get_expr_field_names(expr):
+        if expr.op is None:
+            if expr.lenfield_name is not None:
+                return [expr.lenfield_name]
+            else:
+                # constant value expr
+                return []
+        else:
+            if expr.op == '~':
+                return get_expr_field_names(expr.rhs)
+            elif expr.op == 'popcount':
+                return get_expr_field_names(expr.rhs)
+            elif expr.op == 'sumof':
+                # sumof expr references another list, 
+                # we need that list's length field here
+                field = None
+                for f in expr.lenfield_parent.fields:
+                    if f.field_name == expr.lenfield_name:
+                        field = f
+                        break
+                if field is None:
+                    raise Exception("list field '%s' referenced by sumof not found" % expr.lenfield_name)
+                # referenced list + its length field
+                return [expr.lenfield_name] + get_expr_field_names(field.type.expr)
+            elif expr.op == 'enumref':
+                return []
+            else:
+                return get_expr_field_names(expr.lhs) + get_expr_field_names(expr.rhs)
+    # get_expr_field_names()
+    
+    # resolve the field names with the parent structure(s)
+    unresolved_fields_names = get_expr_field_names(self.expr)
+
+    # construct prefix from self
+    prefix = [('', '', p) for p in self.parents]
+    if self.is_container:
+        prefix.append(('', '', self))
+
+    all_fields = _c_helper_resolve_field_names (prefix)
+    resolved_fields_names = filter(lambda x: x in all_fields.keys(), unresolved_fields_names)
+    if len(unresolved_fields_names) != len(resolved_fields_names):
+        raise Exception("could not resolve all fields for %s" % self.name)
+    
+    resolved_fields = [all_fields[n][1] for n in resolved_fields_names]
+    return resolved_fields
+# get_expr_fields()
+
+def resolve_expr_fields(complex_obj):
+    """
+    find expr fields appearing in complex_obj and descendents that cannot be resolved within complex_obj
+    these are normally fields that need to be given as function parameters
+    """
+    all_fields = []
+    expr_fields = []
+    unresolved = []
+
+    for field in complex_obj.fields:
+        all_fields.append(field)
+        if field.type.is_switch or field.type.is_list:
+            expr_fields += get_expr_fields(field.type)
+        if field.type.is_container:
+            expr_fields += resolve_expr_fields(field.type)
+
+    # try to resolve expr fields
+    for e in expr_fields:
+        if e not in all_fields and e not in unresolved:
+            unresolved.append(e)
+    return unresolved
+# resolve_expr_fields()
+            
+def get_serialize_params(context, self, buffer_var='_buffer', aux_var='_aux'):
+    """
+    functions like _serialize(), _unserialize(), and _unpack() sometimes need additional parameters:
+    E.g. in order to unpack switch, extra parameters might be needed to evaluate the switch 
+    expression. This function tries to resolve all fields within a structure, and returns the 
+    unresolved fields as the list of external parameters. 
+    """
+    def add_param(params, param):
+        if param not in params:
+            params.append(param)
+
+    # collect all fields into param_fields
+    param_fields = []
+    wire_fields = []
+
+    for field in self.fields:
+        if field.visible:
+            # the field should appear as a parameter in the function call
+            param_fields.append(field)
+        if field.wire and not field.auto:
+            if field.type.fixed_size() and not self.is_switch:
+                # field in the xcb_out structure
+                wire_fields.append(field)
+        # fields like 'pad0' are skipped!
+               
+    # in case of switch, parameters always contain any fields referenced in the switch expr
+    # we do not need any variable size fields here, as the switch data type contains both 
+    # fixed and variable size fields
+    if self.is_switch:
+        param_fields = get_expr_fields(self)
+
+    # _serialize()/_unserialize()/_unpack() function parameters
+    # note: don't use set() for params, it is unsorted
+    params = []
+    
+    # 1. the parameter for the void * buffer
+    if  'serialize' == context:
+        params.append(('void', '**', buffer_var))
+    elif context in ('unserialize', 'unpack', 'sizeof'):
+        params.append(('const void', '*', buffer_var))
+
+    # 2. any expr fields that cannot be resolved within self and descendants
+    unresolved_fields = resolve_expr_fields(self)
+    for f in unresolved_fields:
+        add_param(params, (f.c_field_type, '', f.c_field_name))
+
+    # 3. param_fields contain the fields necessary to evaluate the switch expr or any other fields
+    #    that do not appear in the data type struct
+    for p in param_fields:
+        if self.is_switch:
+            typespec = p.c_field_const_type
+            pointerspec = p.c_pointer 
+            add_param(params, (typespec, pointerspec, p.c_field_name))
+        else:
+            if p.visible and not p.wire and not p.auto:
+                typespec = p.c_field_type
+                pointerspec = ''
+                add_param(params, (typespec, pointerspec, p.c_field_name))
+  
+    # 4. aux argument
+    if 'serialize' == context:
+        add_param(params, ('const %s' % self.c_type, '*', aux_var))
+    elif 'unserialize' == context: 
+        add_param(params, ('%s' % self.c_type, '**', aux_var))
+    elif 'unpack' == context:
+        add_param(params, ('%s' % self.c_type, '*', aux_var))
+
+    # 5. switch contains all variable size fields as struct members
+    #    for other data types though, these have to be supplied separately
+    #    this is important for the special case of intermixed fixed and 
+    #    variable size fields
+    if not self.is_switch and 'serialize' == context:
+        for p in param_fields:
+            if not p.type.fixed_size():
+                add_param(params, (p.c_field_const_type, '*', p.c_field_name))
+
+    return (param_fields, wire_fields, params)
+# get_serialize_params()
+
+def _c_serialize_helper_insert_padding(context, code_lines, space, postpone):
+    code_lines.append('%s    /* insert padding */' % space)
+    code_lines.append('%s    xcb_pad = -xcb_block_len & 3;' % space)
+#    code_lines.append('%s    printf("automatically inserting padding: %%%%d\\n", xcb_pad);' % space)
+    code_lines.append('%s    xcb_buffer_len += xcb_block_len + xcb_pad;' % space)
+
+    if not postpone:
+        code_lines.append('%s    if (0 != xcb_pad) {' % space)
+
+        if 'serialize' == context:
+            code_lines.append('%s        xcb_parts[xcb_parts_idx].iov_base = xcb_pad0;' % space)
+            code_lines.append('%s        xcb_parts[xcb_parts_idx].iov_len = xcb_pad;' % space)
+            code_lines.append('%s        xcb_parts_idx++;' % space)
+        elif context in ('unserialize', 'unpack', 'sizeof'):
+            code_lines.append('%s        xcb_tmp += xcb_pad;' % space)
+
+        code_lines.append('%s        xcb_pad = 0;' % space)
+        code_lines.append('%s    }' % space)
+        
+    code_lines.append('%s    xcb_block_len = 0;' % space)
+
+    # keep tracking of xcb_parts entries for serialize
+    return 1
+# _c_serialize_helper_insert_padding()
+
+def _c_serialize_helper_switch(context, self, complex_name, 
+                               code_lines, temp_vars, 
+                               space, prefix):
+    count = 0
+    switch_expr = _c_accessor_get_expr(self.expr, None)
+
+    for b in self.bitcases:            
+        bitcase_expr = _c_accessor_get_expr(b.type.expr, None)
+        code_lines.append('    if(%s & %s) {' % (switch_expr, bitcase_expr))
+#        code_lines.append('        printf("switch %s: entering bitcase section %s (mask=%%%%d)...\\n", %s);' % 
+#                          (self.name[-1], b.type.name[-1], bitcase_expr))
+        b_prefix = prefix
+        if b.type.has_name:
+            b_prefix = prefix + [(b.c_field_name, '.', b.type)]
+            
+        count += _c_serialize_helper_fields(context, b.type, 
+                                            code_lines, temp_vars, 
+                                            "%s    " % space, 
+                                            b_prefix, 
+                                            is_bitcase = True)
+        code_lines.append('    }')
+
+#    if 'serialize' == context:
+#        count += _c_serialize_helper_insert_padding(context, code_lines, space, False)
+#    elif context in ('unserialize', 'unpack', 'sizeof'):
+#        # padding
+#        code_lines.append('%s    xcb_pad = -xcb_block_len & 3;' % space)
+#        code_lines.append('%s    xcb_buffer_len += xcb_block_len + xcb_pad;' % space)
+   
+    return count
+# _c_serialize_helper_switch
+
+def _c_serialize_helper_switch_field(context, self, field, c_switch_variable, prefix):
+    """
+    handle switch by calling _serialize() or _unpack(), depending on context
+    """
+    # switch is handled by this function as a special case
+    param_fields, wire_fields, params = get_serialize_params(context, self)
+    field_mapping = _c_helper_field_mapping(self, prefix)
+    prefix_str = _c_helper_absolute_name(prefix)
+
+    # find the parameters that need to be passed to _serialize()/_unpack():
+    # all switch expr fields must be given as parameters
+    args = get_expr_fields(field.type)
+    # length fields for variable size types in switch, normally only some of need 
+    # need to be passed as parameters
+    switch_len_fields = resolve_expr_fields(field.type)
+
+    # a switch field at this point _must_ be a bitcase field
+    # we require that bitcases are "self-contiguous"
+    bitcase_unresolved = resolve_expr_fields(self)
+    if len(bitcase_unresolved) != 0:
+        raise Exception('unresolved fields within bitcase is not supported at this point')
+
+    # get the C names for the parameters  
+    c_field_names = ''
+    for a in switch_len_fields:
+        c_field_names += "%s, " % field_mapping[a.c_field_name][0]
+    for a in args:
+        c_field_names += "%s, " % field_mapping[a.c_field_name][0]
+
+    # call _serialize()/_unpack() to determine the actual size
+    if 'serialize' == context:
+        length = "%s(&%s, %s&%s%s)" % (field.type.c_serialize_name, c_switch_variable,
+                                       c_field_names, prefix_str, field.c_field_name) 
+    elif context in ('unserialize', 'unpack'):
+        length = "%s(xcb_tmp, %s&%s%s)" % (field.type.c_unpack_name, 
+                                           c_field_names, prefix_str, field.c_field_name)
+
+    return length
+# _c_serialize_helper_switch_field()
+
+def _c_serialize_helper_list_field(context, self, field, 
+                                   code_lines, temp_vars, 
+                                   space, prefix):
+    """
+    helper function to cope with lists of variable length
+    """
+    expr = field.type.expr
+    prefix_str = _c_helper_absolute_name(prefix)
+    param_fields, wire_fields, params = get_serialize_params('sizeof', self)
+    param_names = [p[2] for p in params]
+    
+    expr_fields_names = [f.field_name for f in get_expr_fields(field.type)]
+    resolved = filter(lambda x: x in param_names, expr_fields_names)
+    unresolved = filter(lambda x: x not in param_names, expr_fields_names)
+    
+    field_mapping = {}
+    for r in resolved:
+        field_mapping[r] = (r, None)
+    
+    if len(unresolved)>0:
+        tmp_prefix = prefix
+        if len(tmp_prefix)==0:
+            raise Exception("found an empty prefix while resolving expr field names for list %s", 
+                            field.c_field_name)        
+        
+        field_mapping.update(_c_helper_resolve_field_names(prefix))
+        resolved += filter(lambda x: x in field_mapping, unresolved)
+        unresolved = filter(lambda x: x not in field_mapping, unresolved)
+        if len(unresolved)>0:
+            raise Exception('could not resolve the length fields required for list %s' % field.c_field_name)
+
+    list_length = _c_accessor_get_expr(expr, field_mapping)
+
+    # default: list with fixed size elements
+    length = '%s * sizeof(%s)' % (list_length, field.type.member.c_wiretype)
+
+    # list with variable-sized elements 
+    if not field.type.member.fixed_size():
+        length = ''
+        if context in ('unserialize', 'sizeof', 'unpack'):
+            int_i = '    unsigned int i;'
+            xcb_tmp_len = '    unsigned int xcb_tmp_len;'
+            if int_i not in temp_vars:
+                temp_vars.append(int_i)
+            if xcb_tmp_len not in temp_vars:
+                temp_vars.append(xcb_tmp_len)
+            # loop over all list elements and call sizeof repeatedly
+            # this should be a bit faster than using the iterators
+            code_lines.append("%s    for(i=0; i<%s; i++) {" % (space, list_length))
+            code_lines.append("%s        xcb_tmp_len = %s(xcb_tmp);" % 
+                              (space, field.type.c_sizeof_name))
+            code_lines.append("%s        xcb_block_len += xcb_tmp_len;" % space)
+            code_lines.append("%s        xcb_tmp += xcb_tmp_len;" % space)
+            code_lines.append("%s    }" % space)                  
+      
+        elif 'serialize' == context:
+            code_lines.append('%s    xcb_parts[xcb_parts_idx].iov_len = 0;' % space)
+            code_lines.append('%s    xcb_tmp = (char *) %s%s;' % (space, prefix_str, field.c_field_name))
+            code_lines.append('%s    for(i=0; i<%s; i++) { ' % (space, list_length))
+            code_lines.append('%s        xcb_block_len = %s(xcb_tmp);' % (space, field.type.c_sizeof_name))
+            code_lines.append('%s        xcb_parts[xcb_parts_idx].iov_len += xcb_block_len;' % space)
+            code_lines.append('%s    }' % space)
+            code_lines.append('%s    xcb_block_len = xcb_parts[xcb_parts_idx].iov_len;' % space)
+            
+    return length
+# _c_serialize_helper_list_field()
+
+def _c_serialize_helper_fields_fixed_size(context, self, field, 
+                                          code_lines, temp_vars, 
+                                          space, prefix):
+    # keep the C code a bit more readable by giving the field name
+    if not self.is_bitcase:
+        code_lines.append('%s    /* %s.%s */' % (space, self.c_type, field.c_field_name))
+    else:
+        scoped_name = [p[2].c_type if idx==0 else p[0] for idx, p in enumerate(prefix)]
+        typename = reduce(lambda x,y: "%s.%s" % (x, y), scoped_name)
+        code_lines.append('%s    /* %s.%s */' % (space, typename, field.c_field_name))
+
+    abs_field_name = _c_helper_absolute_name(prefix, field)
+    # default for simple cases: call sizeof()
+    length = "sizeof(%s)" % field.c_field_type
+
+    if context in ('unserialize', 'unpack', 'sizeof'):
+        # default: simple cast
+        value = '    %s = *(%s *)xcb_tmp;' % (abs_field_name, field.c_field_type) 
+        
+        # padding - we could probably just ignore it
+        if field.type.is_pad and field.type.nmemb > 1:
+            value = ''
+            for i in range(field.type.nmemb):
+                code_lines.append('%s    %s[%d] = *(%s *)xcb_tmp;' % 
+                                  (space, abs_field_name, i, field.c_field_type)) 
+            # total padding = sizeof(pad0) * nmemb
+            length += " * %d" % field.type.nmemb
+
+        if field.type.is_list:
+            # no such case in the protocol, cannot be tested and therefore ignored for now
+            raise Exception('list with fixed number of elemens unhandled in _unserialize()')
+
+    elif 'serialize' == context:
+        value = '    xcb_parts[xcb_parts_idx].iov_base = (char *) ' 
+
+        if field.type.is_expr:
+            # need to register a temporary variable for the expression in case we know its type
+            if field.type.c_type is None:
+                raise Exception("type for field '%s' (expression '%s') unkown" % 
+                                (field.field_name, _c_accessor_get_expr(field.type.expr)))
+            
+            temp_vars.append('    %s xcb_expr_%s = %s;' % (field.type.c_type, _cpp(field.field_name), 
+                                                           _c_accessor_get_expr(field.type.expr, prefix)))
+            value += "&xcb_expr_%s;" % _cpp(field.field_name)
+
+        elif field.type.is_pad:
+            if field.type.nmemb == 1:
+                value += "&xcb_pad;"
+            else:
+                # we could also set it to 0, see definition of xcb_send_request()
+                value = '    xcb_parts[xcb_parts_idx].iov_base = xcb_pad0;'
+                length += "*%d" % field.type.nmemb
+
+        else:
+            # non-list type with fixed size
+            if field.type.nmemb == 1:
+                value += "&%s;" % (abs_field_name)
+
+            # list with nmemb (fixed size) elements
+            else:
+                value += '%s;' % (abs_field_name)
+                length = '%d' % field.type.nmemb
+
+    return (value, length)
+# _c_serialize_helper_fields_fixed_size()
+
+def _c_serialize_helper_fields_variable_size(context, self, field, 
+                                             code_lines, temp_vars, 
+                                             space, prefix):
+    prefix_str = _c_helper_absolute_name(prefix)
+
+    if context in ('unserialize', 'unpack', 'sizeof'):
+        value = ''
+        var_field_name = 'xcb_tmp'
+        
+        # special case: intermixed fixed and variable size fields
+        if self.var_followed_by_fixed_fields and 'unserialize' == context:
+            value = '    %s = xcb_tmp;' % field.c_field_name
+            temp_vars.append('    %s *%s;' % (field.type.c_type, field.c_field_name))
+        # special case: switch
+        if 'unpack' == context:
+            value = '    %s%s = (%s *)xcb_tmp;' % (prefix_str, field.c_field_name, field.c_field_type)
+            
+    elif 'serialize' == context:
+        # variable size fields appear as parameters to _serialize() if the 
+        # 'toplevel' container is not a switch
+        prefix_string = prefix_str if prefix[0][2].is_switch else ''
+        var_field_name = "%s%s" % (prefix_string, field.c_field_name)
+        value = '    xcb_parts[xcb_parts_idx].iov_base = (char *) %s;' % var_field_name
+
+    length = ''
+
+    code_lines.append('%s    /* %s */' % (space, field.c_field_name))
+
+    if field.type.is_list:
+        if value != '':
+            # in any context, list is already a pointer, so the default assignment is ok
+            code_lines.append("%s%s" % (space, value))
+            value = ''
+        length = _c_serialize_helper_list_field(context, self, field, 
+                                                code_lines, temp_vars, 
+                                                space, prefix)
+        
+    elif field.type.is_switch:
+        value = ''
+        if context == 'serialize':
+            # the _serialize() function allocates the correct amount memory if given a NULL pointer
+            value = '    xcb_parts[xcb_parts_idx].iov_base = (char *)0;'
+        length = _c_serialize_helper_switch_field(context, self, field, 
+                                                  'xcb_parts[xcb_parts_idx].iov_base', 
+                                                  prefix)
+        
+    else:
+        # in all remaining special cases - call _sizeof()
+        length = "%s(%s)" % (field.type.c_sizeof_name, var_field_name)
+
+    return (value, length)
+# _c_serialize_helper_fields_variable_size
+
+def _c_serialize_helper_fields(context, self, 
+                               code_lines, temp_vars, 
+                               space, prefix, is_bitcase):
+    count = 0
+    need_padding = False
+    prev_field_was_variable = False
+
+    for field in self.fields:
+        if not ((field.wire and not field.auto) or field.visible):
+            continue
+
+        # switch/bitcase: fixed size fields must be considered explicitly 
+        if field.type.fixed_size():
+            if self.is_bitcase or self.var_followed_by_fixed_fields:
+                if prev_field_was_variable and need_padding:
+                    # insert padding
+#                    count += _c_serialize_helper_insert_padding(context, code_lines, space, 
+#                                                                self.var_followed_by_fixed_fields)
+                    prev_field_was_variable = False
+
+                # prefix for fixed size fields
+                fixed_prefix = prefix
+
+                value, length = _c_serialize_helper_fields_fixed_size(context, self, field, 
+                                                                      code_lines, temp_vars, 
+                                                                      space, fixed_prefix)
+            else:
+                continue
+
+        # fields with variable size
+        else:
+            # switch/bitcase: always calculate padding before and after variable sized fields
+            if need_padding or is_bitcase:
+                count += _c_serialize_helper_insert_padding(context, code_lines, space, 
+                                                            self.var_followed_by_fixed_fields)
+
+            value, length = _c_serialize_helper_fields_variable_size(context, self, field, 
+                                                                     code_lines, temp_vars, 
+                                                                     space, prefix)
+            prev_field_was_variable = True
+        
+        # save (un)serialization C code
+        if '' != value:
+            code_lines.append('%s%s' % (space, value))    
+        
+        if field.type.fixed_size():
+            if is_bitcase or self.var_followed_by_fixed_fields:
+                # keep track of (un)serialized object's size
+                code_lines.append('%s    xcb_block_len += %s;' % (space, length))
+                if context in ('unserialize', 'unpack', 'sizeof'):
+                    code_lines.append('%s    xcb_tmp += %s;' % (space, length))
+        else: 
+            # variable size objects or bitcase:
+            #   value & length might have been inserted earlier for special cases
+            if '' != length:
+                # special case: intermixed fixed and variable size fields
+                if (not field.type.fixed_size() and 
+                    self.var_followed_by_fixed_fields and 'unserialize' == context):
+                    temp_vars.append('    int %s_len;' % field.c_field_name)
+                    code_lines.append('%s    %s_len = %s;' % (space, field.c_field_name, length))
+                    code_lines.append('%s    xcb_block_len += %s_len;' % (space, field.c_field_name))
+                    code_lines.append('%s    xcb_tmp += %s_len;' % (space, field.c_field_name))
+                else:
+                    code_lines.append('%s    xcb_block_len += %s;' % (space, length))
+                    # increase pointer into the byte stream accordingly
+                    if context in ('unserialize', 'sizeof', 'unpack'):
+                        code_lines.append('%s    xcb_tmp += xcb_block_len;' % space)
+                        
+        if 'serialize' == context:
+            if '' != length:
+                code_lines.append('%s    xcb_parts[xcb_parts_idx].iov_len = %s;' % (space, length))
+            code_lines.append('%s    xcb_parts_idx++;' % space)
+            count += 1
+
+        need_padding = True
+        if self.var_followed_by_fixed_fields:
+            need_padding = False
+        
+    return count
+# _c_serialize_helper_fields()    
+
+def _c_serialize_helper(context, complex_type, 
+                        code_lines, temp_vars, 
+                        space='', prefix=[]):
+    # count tracks the number of fields to serialize
+    count = 0
+
+    if hasattr(complex_type, 'type'):
+        self = complex_type.type
+        complex_name = complex_type.name
+    else:
+        self = complex_type
+        if self.var_followed_by_fixed_fields and 'unserialize' == context:
+            complex_name = 'xcb_out'
+        else:
+            complex_name = '_aux'
+    
+    # special case: switch is serialized by evaluating each bitcase separately
+    if self.is_switch:
+        count += _c_serialize_helper_switch(context, self, complex_name, 
+                                            code_lines, temp_vars, 
+                                            space, prefix)
+
+    # all other data types can be evaluated one field a time
+    else: 
+        # unserialize & fixed size fields: simply cast the buffer to the respective xcb_out type
+        if context in ('unserialize', 'unpack', 'sizeof') and not self.var_followed_by_fixed_fields:
+            code_lines.append('%s    xcb_block_len += sizeof(%s);' % (space, self.c_type))
+            code_lines.append('%s    xcb_tmp += xcb_block_len;' % space)
+            # probably not needed
+            #_c_serialize_helper_insert_padding(context, code_lines, space, False)
+
+        count += _c_serialize_helper_fields(context, self, 
+                                            code_lines, temp_vars, 
+                                            space, prefix, False)
+    # "final padding"
+    count += _c_serialize_helper_insert_padding(context, code_lines, space, False)
+
+    return count    
+# _c_serialize_helper()
+
+def _c_serialize(context, self):
+    """
+    depending on the context variable, generate _serialize(), _unserialize(), _unpack(), or _sizeof() 
+    for the ComplexType variable self
+    """
+    _h_setlevel(1)
+    _c_setlevel(1)
+
+    _hc('')
+    # _serialize() returns the buffer size
+    _hc('int')
+
+    if self.is_switch and 'unserialize' == context:
+        context = 'unpack'
+
+    cases = { 'serialize'   : self.c_serialize_name, 
+              'unserialize' : self.c_unserialize_name, 
+              'unpack'      : self.c_unpack_name, 
+              'sizeof'      : self.c_sizeof_name }
+    func_name = cases[context]
+            
+    param_fields, wire_fields, params = get_serialize_params(context, self)
+    variable_size_fields = 0
+    # maximum space required for type definition of function arguments
+    maxtypelen = 0
+
+    # determine N(variable_fields) 
+    for field in param_fields:
+        # if self.is_switch, treat all fields as if they are variable sized
+        if not field.type.fixed_size() or self.is_switch:
+            variable_size_fields += 1
+    # determine maxtypelen
+    for p in params:
+        maxtypelen = max(maxtypelen, len(p[0]) + len(p[1]))    
+
+    # write to .c/.h
+    indent = ' '*(len(func_name)+2)
+    param_str = []
+    for p in params:
+        typespec, pointerspec, field_name = p
+        spacing = ' '*(maxtypelen-len(typespec)-len(pointerspec))
+        param_str.append("%s%s%s  %s%s  /**< */" % (indent, typespec, spacing, pointerspec, field_name))
+    # insert function name
+    param_str[0] = "%s (%s" % (func_name, param_str[0].strip())
+    param_str = map(lambda x: "%s," % x, param_str)
+    for s in param_str[:-1]:
+        _hc(s)
+    _h("%s);" % param_str[-1].rstrip(','))
+    _c("%s)" % param_str[-1].rstrip(','))
+    _c('{')
+
+    code_lines = []
+    temp_vars = []
+    prefix = []
+
+    if 'serialize' == context:
+        if not self.is_switch and not self.var_followed_by_fixed_fields:
+            _c('    %s *xcb_out = *_buffer;', self.c_type)
+            _c('    unsigned int xcb_out_pad = -sizeof(%s) & 3;', self.c_type)
+            _c('    unsigned int xcb_buffer_len = sizeof(%s) + xcb_out_pad;', self.c_type)
+        else:
+            _c('    char *xcb_out = *_buffer;')
+            _c('    unsigned int xcb_buffer_len = 0;')
+        prefix = [('_aux', '->', self)]
+        aux_ptr = 'xcb_out'
+
+    elif context in ('unserialize', 'unpack'):
+        _c('    char *xcb_tmp = (char *)_buffer;')
+        if not self.is_switch:
+            if not self.var_followed_by_fixed_fields:
+                _c('    const %s *_aux = (%s *)_buffer;', self.c_type, self.c_type)
+                prefix = [('_aux', '->', self)]
+            else:
+                _c('    %s xcb_out;', self.c_type)
+                prefix = [('xcb_out', '.', self)]
+        else:
+            aux_var = '_aux' # default for unpack: single pointer
+            # note: unserialize not generated for switch
+            if 'unserialize' == context:
+                aux_var = '(*_aux)' # unserialize: double pointer (!)
+            prefix = [(aux_var, '->', self)]
+        aux_ptr = '*_aux'
+        _c('    unsigned int xcb_buffer_len = 0;')
+        _c('    unsigned int xcb_block_len = 0;')
+        _c('    unsigned int xcb_pad = 0;')
+
+    elif 'sizeof' == context:
+        param_names = [p[2] for p in params]
+        if self.is_switch:
+            # switch: call _unpack()
+            _c('    %s _aux;', self.c_type)
+            _c('    return %s(%s, &_aux);', self.c_unpack_name, reduce(lambda x,y: "%s, %s" % (x, y), param_names))
+            _c('}')
+            return
+        elif self.var_followed_by_fixed_fields:
+            # special case: call _unserialize()
+            _c('    %s *_aux = NULL;', self.c_type)
+            _c('    return %s(%s, &_aux);', self.c_unserialize_name, reduce(lambda x,y: "%s, %s" % (x, y), param_names))
+            _c('}')
+            return
+        else:
+            _c('    char *xcb_tmp = (char *)_buffer;')
+            prefix = [('_aux', '->', self)]
+
+    count = _c_serialize_helper(context, self, code_lines, temp_vars, prefix=prefix)
+    # update variable size fields (only important for context=='serialize'
+    variable_size_fields = count
+    if 'serialize' == context:
+        temp_vars.append('    unsigned int xcb_pad = 0;')
+        temp_vars.append('    char xcb_pad0[3] = {0, 0, 0};') 
+        temp_vars.append('    struct iovec xcb_parts[%d];' % count)
+        temp_vars.append('    unsigned int xcb_parts_idx = 0;')
+        temp_vars.append('    unsigned int xcb_block_len = 0;')
+        temp_vars.append('    unsigned int i;')
+        temp_vars.append('    char *xcb_tmp;')
+    elif 'sizeof' == context:
+        # neither switch nor intermixed fixed and variable size fields:
+        # evaluate parameters directly
+        if not (self.is_switch or self.var_followed_by_fixed_fields):
+
+            # look if we have to declare an '_aux' variable at all
+            if len(filter(lambda x: x.find('_aux')!=-1, code_lines))>0: 
+                if not self.var_followed_by_fixed_fields:
+                    _c('    const %s *_aux = (%s *)_buffer;', self.c_type, self.c_type)
+                else:
+                    _c('    %s *_aux = malloc(sizeof(%s));', self.c_type, self.c_type)
+
+            _c('    unsigned int xcb_buffer_len = 0;')
+            _c('    unsigned int xcb_block_len = 0;')
+            _c('    unsigned int xcb_pad = 0;')        
+
+    _c('')
+    for t in temp_vars:
+        _c(t)
+    _c('')
+    for l in code_lines:
+        _c(l)
+
+    # variable sized fields have been collected, now
+    # allocate memory and copy everything into a continuous memory area 
+    # note: this is not necessary in case of unpack
+    if context in ('serialize', 'unserialize'):
+        _c('')
+        _c('    if (NULL == %s) {', aux_ptr)
+        _c('        /* allocate memory */')
+        _c('        %s = malloc(xcb_buffer_len);', aux_ptr)
+        if 'serialize' == context:
+            _c('        *_buffer = xcb_out;')
+        _c('    }')
+        _c('')
+
+        # serialize: handle variable size fields in a loop
+        if 'serialize' == context:
+            if not self.is_switch and not self.var_followed_by_fixed_fields:
+                if len(wire_fields)>0:
+                    _c('    *xcb_out = *_aux;')
+            # copy variable size fields into the buffer
+            if variable_size_fields > 0:
+                # xcb_out padding
+                if not self.is_switch and not self.var_followed_by_fixed_fields:
+                    _c('    xcb_tmp = (char*)++xcb_out;')
+                    _c('    xcb_tmp += xcb_out_pad;')
+                else:
+                    _c('    xcb_tmp = xcb_out;')
+
+                # variable sized fields
+                _c('    for(i=0; i<xcb_parts_idx; i++) {')
+                _c('        if (0 != xcb_parts[i].iov_base && 0 != xcb_parts[i].iov_len)')
+                _c('            memcpy(xcb_tmp, xcb_parts[i].iov_base, xcb_parts[i].iov_len);')
+                _c('        if (0 != xcb_parts[i].iov_len)')
+                _c('            xcb_tmp += xcb_parts[i].iov_len;')
+                _c('    }')
+            
+        # unserialize: assign variable size fields individually
+        if 'unserialize' == context:
+            _c('    *%s = xcb_out;', aux_ptr)
+            _c('    xcb_tmp = (char *)(*_aux+1);')
+            for field in param_fields:
+                if not field.type.fixed_size():
+                    _c('    memcpy(xcb_tmp, %s, %s_len);', field.c_field_name, field.c_field_name)
+                    _c('    xcb_tmp += %s_len;', field.c_field_name)
+ 
+    _c('')
+    _c('    return xcb_buffer_len;')
+    _c('}')
+# _c_serialize()
 
 def _c_iterator_get_end(field, accum):
     '''
@@ -319,7 +1232,6 @@ def _c_iterator_get_end(field, accum):
     '''
     if field.type.is_container:
         accum = field.c_accessor_name + '(' + accum + ')'
-        # XXX there could be fixed-length fields at the end
         return _c_iterator_get_end(field.type.last_varsized_field, accum)
     if field.type.is_list:
         # XXX we can always use the first way
@@ -372,10 +1284,22 @@ def _c_iterator(self, name):
 
     if not self.fixed_size():
         _c('    %s *R = i->data;', self.c_type)
-        _c('    xcb_generic_iterator_t child = %s;', _c_iterator_get_end(self.last_varsized_field, 'R'))
-        _c('    --i->rem;')
-        _c('    i->data = (%s *) child.data;', self.c_type)
-        _c('    i->index = child.index;')
+
+        if self.is_union:
+            # FIXME - how to determine the size of a variable size union??
+            _c('    /* FIXME - determine the size of the union %s */', self.c_type)            
+        else:
+            if self.need_sizeof:
+                _c('    xcb_generic_iterator_t child;')
+                _c('    child.data = (%s *)(((char *)R) + %s(R));', 
+                   self.c_type, self.c_sizeof_name)
+                _c('    i->index = (char *) child.data - (char *) i->data;')
+            else:
+                _c('    xcb_generic_iterator_t child = %s;', _c_iterator_get_end(self.last_varsized_field, 'R'))
+                _c('    i->index = child.index;')
+            _c('    --i->rem;')
+            _c('    i->data = (%s *) child.data;', self.c_type)
+
     else:
         _c('    --i->rem;')
         _c('    ++i->data;')
@@ -424,34 +1348,68 @@ def _c_iterator(self, name):
     _c('    return ret;')
     _c('}')
 
-def _c_accessor_get_length(expr, prefix=''):
+def _c_accessor_get_length(expr, field_mapping=None):
     '''
     Figures out what C code is needed to get a length field.
+    The field_mapping parameter can be used to change the absolute name of a length field. 
     For fields that follow a variable-length field, use the accessor.
     Otherwise, just reference the structure field directly.
     '''
-    prefarrow = '' if prefix == '' else prefix + '->'
 
-    if expr.lenfield != None and expr.lenfield.prev_varsized_field != None:
-        return expr.lenfield.c_accessor_name + '(' + prefix + ')'
-    elif expr.lenfield_name != None:
-        return prefarrow + expr.lenfield_name
+    lenfield_name = expr.lenfield_name
+    if lenfield_name is not None:
+        if field_mapping is not None:
+            lenfield_name = field_mapping[lenfield_name][0]
+ 
+    if expr.lenfield is not None and expr.lenfield.prev_varsized_field is not None:
+        # special case: variable and fixed size fields are intermixed
+        # if the lenfield is among the fixed size fields, there is no need
+        # to call a special accessor function like <expr.lenfield.c_accessor_name + '(' + prefix + ')'>
+        return field_mapping(expr.lenfield_name)
+    elif expr.lenfield_name is not None:
+        return lenfield_name
     else:
         return str(expr.nmemb)
 
-def _c_accessor_get_expr(expr, prefix=''):
+def _c_accessor_get_expr(expr, field_mapping):
     '''
     Figures out what C code is needed to get the length of a list field.
+    The field_mapping parameter can be used to change the absolute name of a length field. 
     Recurses for math operations.
     Returns bitcount for value-mask fields.
     Otherwise, uses the value of the length field.
     '''
-    lenexp = _c_accessor_get_length(expr, prefix)
+    lenexp = _c_accessor_get_length(expr, field_mapping)
 
     if expr.op == '~':
-        return '(' + '~' + _c_accessor_get_expr(expr.rhs, prefix) + ')'
+        return '(' + '~' + _c_accessor_get_expr(expr.rhs, field_mapping) + ')'
+    elif expr.op == 'popcount':
+        return 'xcb_popcount(' + _c_accessor_get_expr(expr.rhs, field_mapping) + ')'
+    elif expr.op == 'enumref':
+        enum_name = expr.lenfield_type.name
+        constant_name = expr.lenfield_name
+        c_name = _n(enum_name + (constant_name,)).upper()
+        return c_name
+    elif expr.op == 'sumof':
+        # locate the referenced list object
+        list_obj = expr.lenfield_type
+        field = None
+        for f in expr.lenfield_parent.fields:
+            if f.field_name == expr.lenfield_name:
+                field = f
+                break
+
+        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)
     elif expr.op != None:
-        return '(' + _c_accessor_get_expr(expr.lhs, prefix) + ' ' + expr.op + ' ' + _c_accessor_get_expr(expr.rhs, prefix) + ')'
+        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:
@@ -461,24 +1419,37 @@ def _c_accessors_field(self, field):
     '''
     Declares the accessor functions for a non-list field that follows a variable-length field.
     '''
+    c_type = self.c_type
+
+    # special case: switch
+    switch_obj = self if self.is_switch else None
+    if self.is_bitcase:
+        switch_obj = self.parents[-1]
+    if switch_obj is not None:
+        c_type = switch_obj.c_type
+
     if field.type.is_simple:
         _hc('')
         _hc('')
         _hc('/*****************************************************************************')
-        _hc(' **')
+        _hc(' ** ')
         _hc(' ** %s %s', field.c_field_type, field.c_accessor_name)
         _hc(' ** ')
-        _hc(' ** @param const %s *R', self.c_type)
+        _hc(' ** @param const %s *R', c_type)
         _hc(' ** @returns %s', field.c_field_type)
         _hc(' **')
         _hc(' *****************************************************************************/')
         _hc(' ')
         _hc('%s', field.c_field_type)
-        _h('%s (const %s *R  /**< */);', field.c_accessor_name, self.c_type)
-        _c('%s (const %s *R  /**< */)', field.c_accessor_name, self.c_type)
+        _h('%s (const %s *R  /**< */);', field.c_accessor_name, c_type)
+        _c('%s (const %s *R  /**< */)', field.c_accessor_name, c_type)
         _c('{')
-        _c('    xcb_generic_iterator_t prev = %s;', _c_iterator_get_end(field.prev_varsized_field, 'R'))
-        _c('    return * (%s *) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index) + %d);', field.c_field_type, field.first_field_after_varsized.type.c_type, field.prev_varsized_offset)
+        if field.prev_varsized_field is None:
+            _c('    return (%s *) (R + 1);', field.c_field_type)
+        else:
+            _c('    xcb_generic_iterator_t prev = %s;', _c_iterator_get_end(field.prev_varsized_field, 'R'))
+            _c('    return * (%s *) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index) + %d);', 
+               field.c_field_type, field.first_field_after_varsized.type.c_type, field.prev_varsized_offset)
         _c('}')
     else:
         _hc('')
@@ -487,18 +1458,31 @@ def _c_accessors_field(self, field):
         _hc(' **')
         _hc(' ** %s * %s', field.c_field_type, field.c_accessor_name)
         _hc(' ** ')
-        _hc(' ** @param const %s *R', self.c_type)
+        _hc(' ** @param const %s *R', c_type)
         _hc(' ** @returns %s *', field.c_field_type)
         _hc(' **')
         _hc(' *****************************************************************************/')
         _hc(' ')
-        _hc('%s *', field.c_field_type)
-        _h('%s (const %s *R  /**< */);', field.c_accessor_name, self.c_type)
-        _c('%s (const %s *R  /**< */)', field.c_accessor_name, self.c_type)
+        if field.type.is_switch and switch_obj is None:
+            return_type = 'void *'
+        else:
+            return_type = '%s *' % field.c_field_type
+
+        _hc(return_type)
+        _h('%s (const %s *R  /**< */);', field.c_accessor_name, c_type)
+        _c('%s (const %s *R  /**< */)', field.c_accessor_name, c_type)
         _c('{')
-        _c('    xcb_generic_iterator_t prev = %s;', _c_iterator_get_end(field.prev_varsized_field, 'R'))
-        _c('    return (%s *) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index) + %d);', field.c_field_type, field.first_field_after_varsized.type.c_type, field.prev_varsized_offset)
+        if field.prev_varsized_field is None:
+            _c('    return (%s) (R + 1);', return_type)
+            # note: the special case 'variable fields followed by fixed size fields'
+            #       is not of any consequence here, since the ordering gets 
+            #       'corrected' in the reply function
+        else:
+            _c('    xcb_generic_iterator_t prev = %s;', _c_iterator_get_end(field.prev_varsized_field, 'R'))
+            _c('    return (%s) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index) + %d);', 
+               return_type, field.first_field_after_varsized.type.c_type, field.prev_varsized_offset)
         _c('}')
+
     
 def _c_accessors_list(self, field):
     '''
@@ -507,32 +1491,83 @@ def _c_accessors_list(self, field):
     Declares length and get-iterator functions always.
     '''
     list = field.type
+    c_type = self.c_type
+
+    # special case: switch
+    # in case of switch, 2 params have to be supplied to certain accessor functions:
+    #   1. the anchestor object (request or reply)
+    #   2. the (anchestor) switch object
+    # the reason is that switch is either a child of a request/reply or nested in another switch, 
+    # so whenever we need to access a length field, we might need to refer to some anchestor type
+    switch_obj = self if self.is_switch else None
+    if self.is_bitcase:
+        switch_obj = self.parents[-1]
+    if switch_obj is not None:
+        c_type = switch_obj.c_type
+
+    params = []
+    fields = {}
+    parents = self.parents if hasattr(self, 'parents') else [self]
+    # 'R': parents[0] is always the 'toplevel' container type 
+    params.append(('const %s *R' % parents[0].c_type, parents[0]))
+    fields.update(_c_helper_field_mapping(parents[0], [('R', '->', parents[0])], flat=True))
+    # auxiliary object for 'R' parameters
+    R_obj = parents[0]
+
+    if switch_obj is not None:
+        # now look where the fields are defined that are needed to evaluate 
+        # the switch expr, and store the parent objects in accessor_params and
+        # the fields in switch_fields
+
+        # 'S': name for the 'toplevel' switch
+        toplevel_switch = parents[1]
+        params.append(('const %s *S' % toplevel_switch.c_type, toplevel_switch))
+        fields.update(_c_helper_field_mapping(toplevel_switch, [('S', '->', toplevel_switch)], flat=True))
+
+        # initialize prefix for everything "below" S
+        prefix_str = '/* %s */ S' % toplevel_switch.name[-1]
+        prefix = [(prefix_str, '->', toplevel_switch)]
+
+        # look for fields in the remaining containers
+        for p in parents[2:] + [self]:
+            # the separator between parent and child is always '.' here, 
+            # because of nested switch statements
+            if not p.is_bitcase or (p.is_bitcase and p.has_name):
+                prefix.append((p.name[-1], '.', p))
+            fields.update(_c_helper_field_mapping(p, prefix, flat=True))
+
+        # auxiliary object for 'S' parameter
+        S_obj = parents[1]
 
     _h_setlevel(1)
     _c_setlevel(1)
     if list.member.fixed_size():
+        idx = 1 if switch_obj is not None else 0
         _hc('')
         _hc('')
         _hc('/*****************************************************************************')
         _hc(' **')
         _hc(' ** %s * %s', field.c_field_type, field.c_accessor_name)
         _hc(' ** ')
-        _hc(' ** @param const %s *R', self.c_type)
+        _hc(' ** @param %s', params[idx][0])
         _hc(' ** @returns %s *', field.c_field_type)
         _hc(' **')
         _hc(' *****************************************************************************/')
         _hc(' ')
         _hc('%s *', field.c_field_type)
-        _h('%s (const %s *R  /**< */);', field.c_accessor_name, self.c_type)
-        _c('%s (const %s *R  /**< */)', field.c_accessor_name, self.c_type)
-        _c('{')
 
-        if field.prev_varsized_field == None:
+        _h('%s (%s  /**< */);', field.c_accessor_name, params[idx][0])
+        _c('%s (%s  /**< */)', field.c_accessor_name, params[idx][0])
+
+        _c('{')
+        if switch_obj is not None:
+            _c('    return %s;', fields[field.c_field_name][0])
+        elif field.prev_varsized_field is None:
             _c('    return (%s *) (R + 1);', field.c_field_type)
         else:
             _c('    xcb_generic_iterator_t prev = %s;', _c_iterator_get_end(field.prev_varsized_field, 'R'))
-            _c('    return (%s *) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index) + %d);', field.c_field_type, field.first_field_after_varsized.type.c_type, field.prev_varsized_offset)
-
+            _c('    return (%s *) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index) + %d);', 
+               field.c_field_type, field.first_field_after_varsized.type.c_type, field.prev_varsized_offset)
         _c('}')
 
     _hc('')
@@ -541,16 +1576,24 @@ def _c_accessors_list(self, field):
     _hc(' **')
     _hc(' ** int %s', field.c_length_name)
     _hc(' ** ')
-    _hc(' ** @param const %s *R', self.c_type)
+    _hc(' ** @param const %s *R', c_type)
     _hc(' ** @returns int')
     _hc(' **')
     _hc(' *****************************************************************************/')
     _hc(' ')
     _hc('int')
-    _h('%s (const %s *R  /**< */);', field.c_length_name, self.c_type)
-    _c('%s (const %s *R  /**< */)', field.c_length_name, self.c_type)
+    if switch_obj is not None:
+        _hc('%s (const %s *R  /**< */,', field.c_length_name, R_obj.c_type)
+        spacing = ' '*(len(field.c_length_name)+2)
+        _h('%sconst %s *S /**< */);', spacing, S_obj.c_type)
+        _c('%sconst %s *S  /**< */)', spacing, S_obj.c_type)
+        length = _c_accessor_get_expr(field.type.expr, fields)
+    else:
+        _h('%s (const %s *R  /**< */);', field.c_length_name, c_type)
+        _c('%s (const %s *R  /**< */)', field.c_length_name, c_type)
+        length = _c_accessor_get_expr(field.type.expr, fields)
     _c('{')
-    _c('    return %s;', _c_accessor_get_expr(field.type.expr, 'R'))
+    _c('    return %s;', length)
     _c('}')
 
     if field.type.member.is_simple:
@@ -560,25 +1603,38 @@ def _c_accessors_list(self, field):
         _hc(' **')
         _hc(' ** xcb_generic_iterator_t %s', field.c_end_name)
         _hc(' ** ')
-        _hc(' ** @param const %s *R', self.c_type)
+        _hc(' ** @param const %s *R', c_type)
         _hc(' ** @returns xcb_generic_iterator_t')
         _hc(' **')
         _hc(' *****************************************************************************/')
         _hc(' ')
         _hc('xcb_generic_iterator_t')
-        _h('%s (const %s *R  /**< */);', field.c_end_name, self.c_type)
-        _c('%s (const %s *R  /**< */)', field.c_end_name, self.c_type)
+        if switch_obj is not None:
+            _hc('%s (const %s *R  /**< */,', field.c_end_name, R_obj.c_type)
+            spacing = ' '*(len(field.c_end_name)+2)
+            _h('%sconst %s *S /**< */);', spacing, S_obj.c_type)
+            _c('%sconst %s *S  /**< */)', spacing, S_obj.c_type)
+        else:
+            _h('%s (const %s *R  /**< */);', field.c_end_name, c_type)
+            _c('%s (const %s *R  /**< */)', field.c_end_name, c_type)
         _c('{')
         _c('    xcb_generic_iterator_t i;')
-
-        if field.prev_varsized_field == None:
-            _c('    i.data = ((%s *) (R + 1)) + (%s);', field.type.c_wiretype, _c_accessor_get_expr(field.type.expr, 'R'))
+        
+        param = 'R' if switch_obj is None else 'S'
+        if switch_obj is not None:
+            _c('    i.data = %s + %s;', fields[field.c_field_name][0], 
+               _c_accessor_get_expr(field.type.expr, fields))
+        elif field.prev_varsized_field == None:
+            _c('    i.data = ((%s *) (R + 1)) + (%s);', field.type.c_wiretype, 
+               _c_accessor_get_expr(field.type.expr, fields))
         else:
-            _c('    xcb_generic_iterator_t child = %s;', _c_iterator_get_end(field.prev_varsized_field, 'R'))
-            _c('    i.data = ((%s *) child.data) + (%s);', field.type.c_wiretype, _c_accessor_get_expr(field.type.expr, 'R'))
+            _c('    xcb_generic_iterator_t child = %s;', 
+               _c_iterator_get_end(field.prev_varsized_field, 'R'))
+            _c('    i.data = ((%s *) child.data) + (%s);', field.type.c_wiretype, 
+               _c_accessor_get_expr(field.type.expr, fields))
 
         _c('    i.rem = 0;')
-        _c('    i.index = (char *) i.data - (char *) R;')
+        _c('    i.index = (char *) i.data - (char *) %s;', param)
         _c('    return i;')
         _c('}')
 
@@ -589,25 +1645,36 @@ def _c_accessors_list(self, field):
         _hc(' **')
         _hc(' ** %s %s', field.c_iterator_type, field.c_iterator_name)
         _hc(' ** ')
-        _hc(' ** @param const %s *R', self.c_type)
+        _hc(' ** @param const %s *R', c_type)
         _hc(' ** @returns %s', field.c_iterator_type)
         _hc(' **')
         _hc(' *****************************************************************************/')
         _hc(' ')
+
         _hc('%s', field.c_iterator_type)
-        _h('%s (const %s *R  /**< */);', field.c_iterator_name, self.c_type)
-        _c('%s (const %s *R  /**< */)', field.c_iterator_name, self.c_type)
+        if switch_obj is not None:
+            _hc('%s (const %s *R  /**< */,', field.c_iterator_name, R_obj.c_type)
+            spacing = ' '*(len(field.c_iterator_name)+2)
+            _h('%sconst %s *S /**< */);', spacing, S_obj.c_type)
+            _c('%sconst %s *S  /**< */)', spacing, S_obj.c_type)
+        else:
+            _h('%s (const %s *R  /**< */);', field.c_iterator_name, c_type)
+            _c('%s (const %s *R  /**< */)', field.c_iterator_name, c_type)
         _c('{')
         _c('    %s i;', field.c_iterator_type)
 
-        if field.prev_varsized_field == None:
+        if switch_obj is not None:
+            _c('    i.data = %s;', fields[field.c_field_name][0])
+            _c('    i.rem = %s;', _c_accessor_get_expr(field.type.expr, fields))
+        elif field.prev_varsized_field == None:
             _c('    i.data = (%s *) (R + 1);', field.c_field_type)
         else:
             _c('    xcb_generic_iterator_t prev = %s;', _c_iterator_get_end(field.prev_varsized_field, 'R'))
-            _c('    i.data = (%s *) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index));', field.c_field_type, field.c_field_type)
-
-        _c('    i.rem = %s;', _c_accessor_get_expr(field.type.expr, 'R'))
-        _c('    i.index = (char *) i.data - (char *) R;')
+            _c('    i.data = (%s *) ((char *) prev.data + XCB_TYPE_PAD(%s, prev.index));', 
+               field.c_field_type, field.c_field_type)
+        if switch_obj is None:
+            _c('    i.rem = %s;', _c_accessor_get_expr(field.type.expr, fields))
+        _c('    i.index = (char *) i.data - (char *) %s;', 'R' if switch_obj is None else 'S' )
         _c('    return i;')
         _c('}')
 
@@ -615,11 +1682,17 @@ def _c_accessors(self, name, base):
     '''
     Declares the accessor functions for the fields of a structure.
     '''
-    for field in self.fields:
-        if field.type.is_list and not field.type.fixed_size():
-            _c_accessors_list(self, field)
-        elif field.prev_varsized_field != None:
-            _c_accessors_field(self, field)
+    # no accessors for switch itself - 
+    # switch always needs to be unpacked explicitly
+#    if self.is_switch:
+#        pass
+#    else:
+    if True:
+        for field in self.fields:
+            if field.type.is_list and not field.type.fixed_size():
+                _c_accessors_list(self, field)
+            elif field.prev_varsized_field is not None or not field.type.fixed_size():
+                _c_accessors_field(self, field)
 
 def c_simple(self, name):
     '''
@@ -655,23 +1728,43 @@ def _c_complex(self):
 
     varfield = None
     for field in self.fields:
-        if not field.type.fixed_size():
+        if not field.type.fixed_size() and not self.is_switch and not self.is_union:
             varfield = field.c_field_name
             continue
-        if varfield != None and not field.type.is_pad and field.wire:
-            errmsg = '%s: warning: variable field %s followed by fixed field %s\n' % (self.c_type, varfield, field.c_field_name)
-            sys.stderr.write(errmsg)
-            # sys.exit(1)
         if field.wire:
             struct_fields.append(field)
-        
+    
     for field in struct_fields:
-        if len(field.c_field_type) > maxtypelen:
-            maxtypelen = len(field.c_field_type)
+        length = len(field.c_field_type)
+        # account for '*' pointer_spec
+        if not field.type.fixed_size():
+            length += 1
+        maxtypelen = max(maxtypelen, length)
+
+    def _c_complex_field(self, field, space=''):
+        if (field.type.fixed_size() or 
+            # in case of switch with switch children, don't make the field a pointer
+            # necessary for unserialize to work
+            (self.is_switch and field.type.is_switch)):
+            spacing = ' ' * (maxtypelen - len(field.c_field_type))
+            _h('%s    %s%s %s%s; /**<  */', space, field.c_field_type, spacing, field.c_field_name, field.c_subscript)
+        else:
+            spacing = ' ' * (maxtypelen - (len(field.c_field_type) + 1))
+            _h('%s    %s%s *%s%s; /**<  */', space, field.c_field_type, spacing, field.c_field_name, field.c_subscript)
 
-    for field in struct_fields:
-        spacing = ' ' * (maxtypelen - len(field.c_field_type))
-        _h('    %s%s %s%s; /**<  */', field.c_field_type, spacing, field.c_field_name, field.c_subscript)
+    if not self.is_switch:
+        for field in struct_fields:
+            _c_complex_field(self, field)
+    else:
+        for b in self.bitcases:
+            space = ''
+            if b.type.has_name:
+                _h('    struct _%s {', b.c_field_name)
+                space = '    '
+            for field in b.type.fields:
+                _c_complex_field(self, field, space)
+            if b.type.has_name:
+                _h('    } %s;', b.c_field_name)
 
     _h('} %s;', self.c_type)
 
@@ -692,7 +1785,7 @@ def c_union(self, name):
     _c_complex(self)
     _c_iterator(self, name)
 
-def _c_request_helper(self, name, cookie_type, void, regular):
+def _c_request_helper(self, name, cookie_type, void, regular, aux=False):
     '''
     Declares a request function.
     '''
@@ -725,15 +1818,18 @@ def _c_request_helper(self, name, cookie_type, void, regular):
     func_ext_global = '&' + _ns.c_ext_global_name if _ns.is_ext else '0'
 
     # What our function name is
-    func_name = self.c_request_name
+    func_name = self.c_request_name if not aux else self.c_aux_name
     if checked:
-        func_name = self.c_checked_name
+        func_name = self.c_checked_name if not aux else self.c_aux_checked_name
     if unchecked:
-        func_name = self.c_unchecked_name
+        func_name = self.c_unchecked_name if not aux else self.c_aux_unchecked_name
 
     param_fields = []
     wire_fields = []
     maxtypelen = len('xcb_connection_t')
+    serial_fields = []
+    # special case: list with variable size elements
+    list_with_var_size_elems = False
 
     for field in self.fields:
         if field.visible:
@@ -742,10 +1838,17 @@ def _c_request_helper(self, name, cookie_type, void, regular):
         if field.wire and not field.auto:
             # We need to set the field up in the structure
             wire_fields.append(field)
+        if field.type.need_serialize or field.type.need_sizeof:
+            serial_fields.append(field)
         
     for field in param_fields:
-        if len(field.c_field_const_type) > maxtypelen:
-            maxtypelen = len(field.c_field_const_type)
+        c_field_const_type = field.c_field_const_type 
+        if field.type.need_serialize and not aux:
+            c_field_const_type = "const void"
+        if len(c_field_const_type) > maxtypelen:
+            maxtypelen = len(c_field_const_type)
+        if field.type.is_list and not field.type.member.fixed_size():
+            list_with_var_size_elems = True
 
     _h_setlevel(1)
     _c_setlevel(1)
@@ -777,8 +1880,11 @@ def _c_request_helper(self, name, cookie_type, void, regular):
     _hc(' ** @param xcb_connection_t%s *c', spacing)
 
     for field in param_fields:
-        spacing = ' ' * (maxtypelen - len(field.c_field_const_type))
-        _hc(' ** @param %s%s %s%s', field.c_field_const_type, spacing, field.c_pointer, field.c_field_name)
+        c_field_const_type = field.c_field_const_type 
+        if field.type.need_serialize and not aux:
+            c_field_const_type = "const void"
+        spacing = ' ' * (maxtypelen - len(c_field_const_type))
+        _hc(' ** @param %s%s %s%s', c_field_const_type, spacing, field.c_pointer, field.c_field_name)
 
     _hc(' ** @returns %s', cookie_type)
     _hc(' **')
@@ -796,16 +1902,28 @@ def _c_request_helper(self, name, cookie_type, void, regular):
     count = len(param_fields)
     for field in param_fields:
         count = count - 1
-        spacing = ' ' * (maxtypelen - len(field.c_field_const_type))
+        c_field_const_type = field.c_field_const_type 
+        c_pointer = field.c_pointer
+        if field.type.need_serialize and not aux:
+            c_field_const_type = "const void"
+            c_pointer = '*'
+        spacing = ' ' * (maxtypelen - len(c_field_const_type))
         comma = ',' if count else ');'
-        _h('%s%s%s %s%s  /**< */%s', func_spacing, field.c_field_const_type, spacing, field.c_pointer, field.c_field_name, comma)
+        _h('%s%s%s %s%s  /**< */%s', func_spacing, c_field_const_type, 
+           spacing, c_pointer, field.c_field_name, comma)
         comma = ',' if count else ')'
-        _c('%s%s%s %s%s  /**< */%s', func_spacing, field.c_field_const_type, spacing, field.c_pointer, field.c_field_name, comma)
+        _c('%s%s%s %s%s  /**< */%s', func_spacing, c_field_const_type, 
+           spacing, c_pointer, field.c_field_name, comma)
 
     count = 2
-    for field in param_fields:
-        if not field.type.fixed_size():
-            count = count + 2
+    if not self.var_followed_by_fixed_fields:
+        for field in param_fields:
+            if not field.type.fixed_size():
+                count = count + 2
+                if field.type.need_serialize:
+                    # _serialize() keeps track of padding automatically
+                    count -= 1
+    dimension = count + 2
 
     _c('{')
     _c('    static const xcb_protocol_request_t xcb_req = {')
@@ -815,16 +1933,31 @@ def _c_request_helper(self, name, cookie_type, void, regular):
     _c('        /* isvoid */ %d', 1 if void else 0)
     _c('    };')
     _c('    ')
-    _c('    struct iovec xcb_parts[%d];', count + 2)
+
+    _c('    struct iovec xcb_parts[%d];', dimension)
     _c('    %s xcb_ret;', func_cookie)
     _c('    %s xcb_out;', self.c_type)
-    _c('    ')
+    if self.var_followed_by_fixed_fields:
+        _c('    /* in the protocol description, variable size fields are followed by fixed size fields */')
+        _c('    void *xcb_aux = 0;')
+        
 
+    for idx, f in enumerate(serial_fields):
+        if aux:
+            _c('    void *xcb_aux%d = 0;' % (idx))
+    if list_with_var_size_elems:
+        _c('    unsigned int i;')
+        _c('    unsigned int xcb_tmp_len;')
+        _c('    char *xcb_tmp;')
+    _c('    ')
+    # simple request call tracing
+#    _c('    printf("in function %s\\n");' % func_name)     
+ 
+    # fixed size fields
     for field in wire_fields:
         if field.type.fixed_size():
             if field.type.is_expr:
-                _c('    xcb_out.%s = %s;', field.c_field_name, _c_accessor_get_expr(field.type.expr))
-
+                _c('    xcb_out.%s = %s;', field.c_field_name, _c_accessor_get_expr(field.type.expr, None))
             elif field.type.is_pad:
                 if field.type.nmemb == 1:
                     _c('    xcb_out.%s = 0;', field.c_field_name)
@@ -836,25 +1969,94 @@ def _c_request_helper(self, name, cookie_type, void, regular):
                 else:
                     _c('    memcpy(xcb_out.%s, %s, %d);', field.c_field_name, field.c_field_name, field.type.nmemb)
 
-    _c('    ')
-    _c('    xcb_parts[2].iov_base = (char *) &xcb_out;')
-    _c('    xcb_parts[2].iov_len = sizeof(xcb_out);')
-    _c('    xcb_parts[3].iov_base = 0;')
-    _c('    xcb_parts[3].iov_len = -xcb_parts[2].iov_len & 3;')
+    def get_serialize_args(type_obj, c_field_name, aux_var, context='serialize'):
+        serialize_args = get_serialize_params(context, type_obj, 
+                                              c_field_name, 
+                                              aux_var)[2]
+        return reduce(lambda x,y: "%s, %s" % (x,y), [a[2] for a in serialize_args])
 
-    count = 4
-    for field in param_fields:
-        if not field.type.fixed_size():
-            _c('    xcb_parts[%d].iov_base = (char *) %s;', count, field.c_field_name)
-            if field.type.is_list:
-                _c('    xcb_parts[%d].iov_len = %s * sizeof(%s);', count, _c_accessor_get_expr(field.type.expr), field.type.member.c_wiretype)
-            else:
-                _c('    xcb_parts[%d].iov_len = %s * sizeof(%s);', count, 'Uh oh', field.type.c_wiretype)
-            _c('    xcb_parts[%d].iov_base = 0;', count + 1)
-            _c('    xcb_parts[%d].iov_len = -xcb_parts[%d].iov_len & 3;', count + 1, count)
-            count = count + 2
+    # calls in order to free dyn. all. memory
+    free_calls = []
 
+    _c('    ')
+    if not self.var_followed_by_fixed_fields:
+        _c('    xcb_parts[2].iov_base = (char *) &xcb_out;')
+        _c('    xcb_parts[2].iov_len = sizeof(xcb_out);')
+        _c('    xcb_parts[3].iov_base = 0;')
+        _c('    xcb_parts[3].iov_len = -xcb_parts[2].iov_len & 3;')
+
+        count = 4
+
+        for field in param_fields:
+            if not field.type.fixed_size():
+                _c('    /* %s %s */', field.type.c_type, field.c_field_name)
+                # default: simple cast to char *
+                if not field.type.need_serialize and not field.type.need_sizeof:
+                    _c('    xcb_parts[%d].iov_base = (char *) %s;', count, field.c_field_name)
+                    if field.type.is_list:
+                        if field.type.member.fixed_size():
+                            _c('    xcb_parts[%d].iov_len = %s * sizeof(%s);', count, 
+                               _c_accessor_get_expr(field.type.expr, None), 
+                               field.type.member.c_wiretype)
+                        else:
+                            list_length = _c_accessor_get_expr(field.type.expr, None)
+    
+                            length = ''
+                            _c("    xcb_parts[%d].iov_len = 0;" % count)
+                            _c("    xcb_tmp = (char *)%s;", field.c_field_name)
+                            _c("    for(i=0; i<%s; i++) {" % list_length)
+                            _c("        xcb_tmp_len = %s(xcb_tmp);" % 
+                                              (field.type.c_sizeof_name))
+                            _c("        xcb_parts[%d].iov_len += xcb_tmp_len;" % count)
+                            _c("        xcb_tmp += xcb_tmp_len;")
+                            _c("    }")                        
+                    else:
+                        # not supposed to happen
+                        raise Exception("unhandled variable size field %s" % field.c_field_name)
+                else:
+                    if not aux:
+                        _c('    xcb_parts[%d].iov_base = (char *) %s;', count, field.c_field_name)
+                    idx = serial_fields.index(field)
+                    aux_var = '&xcb_aux%d' % idx
+                    context = 'serialize' if aux else 'sizeof'
+                    _c('    xcb_parts[%d].iov_len = ', count)
+                    if aux:
+                        serialize_args = get_serialize_args(field.type, aux_var, field.c_field_name, context)
+                        _c('      %s (%s);', field.type.c_serialize_name, serialize_args)
+                        _c('    xcb_parts[%d].iov_base = xcb_aux%d;' % (count, idx))
+                        free_calls.append('    free(xcb_aux%d);' % idx)
+                    else:
+                        serialize_args = get_serialize_args(field.type, field.c_field_name, aux_var, context)
+                        func_name = field.type.c_sizeof_name
+                        _c('      %s (%s);', func_name, serialize_args)
+
+                count += 1
+                if not (field.type.need_serialize or field.type.need_sizeof):
+                    # the _serialize() function keeps track of padding automatically
+                    _c('    xcb_parts[%d].iov_base = 0;', count)
+                    _c('    xcb_parts[%d].iov_len = -xcb_parts[%d].iov_len & 3;', count, count-1)
+                    count += 1
+
+    # elif self.var_followed_by_fixed_fields:
+    else:
+        _c('    xcb_parts[2].iov_base = (char *) &xcb_out;')
+        # request header: opcodes + length
+        _c('    xcb_parts[2].iov_len = 2*sizeof(uint8_t) + sizeof(uint16_t);') 
+        count += 1
+        # call _serialize()
+        buffer_var = '&xcb_aux'
+        serialize_args = get_serialize_args(self, buffer_var, '&xcb_out', 'serialize')
+        _c('    xcb_parts[%d].iov_len = %s (%s);', count, self.c_serialize_name, serialize_args)
+        _c('    xcb_parts[%d].iov_base = (char *) xcb_aux;', count)
+        free_calls.append('    free(xcb_aux);')
+        # no padding necessary - _serialize() keeps track of padding automatically
+
+    _c('    ')
     _c('    xcb_ret.sequence = xcb_send_request(c, %s, xcb_parts + 2, &xcb_req);', func_flags)
+    
+    # free dyn. all. data, if any
+    for f in free_calls:
+        _c(f)
     _c('    return xcb_ret;')
     _c('}')
 
@@ -865,7 +2067,29 @@ def _c_reply(self, name):
     spacing1 = ' ' * (len(self.c_cookie_type) - len('xcb_connection_t'))
     spacing2 = ' ' * (len(self.c_cookie_type) - len('xcb_generic_error_t'))
     spacing3 = ' ' * (len(self.c_reply_name) + 2)
-
+    
+    # check if _unserialize() has to be called for any field
+    def look_for_special_cases(complex_obj):
+        unserialize_fields = []
+        # no unserialize call in case of switch
+        if not complex_obj.is_switch:
+            for field in complex_obj.fields:
+                # three cases: 1. field with special case
+                #              2. container that contains special case field
+                #              3. list with special case elements
+                if field.type.var_followed_by_fixed_fields:
+                    unserialize_fields.append(field)
+                elif field.type.is_container:
+                    unserialize_fields += look_for_special_cases(field.type)
+                elif field.type.is_list:
+                    if field.type.member.var_followed_by_fixed_fields:
+                        unserialize_fields.append(field)
+                    if field.type.member.is_container:
+                        unserialize_fields += look_for_special_cases(field.type.member)
+        return unserialize_fields
+    
+    unserialize_fields = look_for_special_cases(self.reply)
+    
     _h('')
     _h('/**')
     _h(' * Return the reply')
@@ -900,7 +2124,35 @@ def _c_reply(self, name):
     _h('%sxcb_generic_error_t%s **e  /**< */);', spacing3, spacing2)
     _c('%sxcb_generic_error_t%s **e  /**< */)', spacing3, spacing2)
     _c('{')
-    _c('    return (%s *) xcb_wait_for_reply(c, cookie.sequence, e);', self.c_reply_type)
+    
+    if len(unserialize_fields)>0:
+        # certain variable size fields need to be unserialized explicitly
+        _c('    %s *reply = (%s *) xcb_wait_for_reply(c, cookie.sequence, e);', 
+           self.c_reply_type, self.c_reply_type)
+        _c('    int i;')
+        for field in unserialize_fields:
+            if field.type.is_list:
+                _c('    %s %s_iter = %s(reply);', field.c_iterator_type, field.c_field_name, field.c_iterator_name)
+                _c('    int %s_len = %s(reply);', field.c_field_name, field.c_length_name)
+                _c('    %s *%s_data;', field.c_field_type, field.c_field_name)
+            else:
+                raise Exception('not implemented: call _unserialize() in reply for non-list type %s', field.c_field_type)
+        # call _unserialize(), using the reply as source and target buffer
+        _c('    /* special cases: transform parts of the reply to match XCB data structures */')
+        for field in unserialize_fields:
+            if field.type.is_list:
+                _c('    for(i=0; i<%s_len; i++) {', field.c_field_name)
+                _c('        %s_data = %s_iter.data;', field.c_field_name, field.c_field_name)
+                _c('        %s((const void *)%s_data, &%s_data);', field.type.c_unserialize_name, 
+                   field.c_field_name, field.c_field_name)
+                _c('        %s(&%s_iter);', field.type.c_next_name, field.c_field_name)
+                _c('    }')
+        # return the transformed reply
+        _c('    return reply;')
+    
+    else:
+        _c('    return (%s *) xcb_wait_for_reply(c, cookie.sequence, e);', self.c_reply_type)
+
     _c('}')
 
 def _c_opcode(name, opcode):
@@ -948,6 +2200,9 @@ def c_request(self, name):
         # Request prototypes
         _c_request_helper(self, name, self.c_cookie_type, False, True)
         _c_request_helper(self, name, self.c_cookie_type, False, False)
+        if self.need_aux:
+            _c_request_helper(self, name, self.c_cookie_type, False, True, True)
+            _c_request_helper(self, name, self.c_cookie_type, False, False, True)
         # Reply accessors
         _c_accessors(self.reply, name + ('reply',), name)
         _c_reply(self, name)
@@ -955,6 +2210,10 @@ def c_request(self, name):
         # Request prototypes
         _c_request_helper(self, name, 'xcb_void_cookie_t', True, False)
         _c_request_helper(self, name, 'xcb_void_cookie_t', True, True)
+        if self.need_aux:
+            _c_request_helper(self, name, 'xcb_void_cookie_t', True, False, True)
+            _c_request_helper(self, name, 'xcb_void_cookie_t', True, True, True)
+
 
 def c_event(self, name):
     '''
@@ -1002,7 +2261,7 @@ output = {'open'    : c_open,
           'union'   : c_union,
           'request' : c_request,
           'event'   : c_event,
-          'error'   : c_error
+          'error'   : c_error, 
           }
 
 # Boilerplate below this point
diff --git a/src/xcb_util.c b/src/xcb_util.c
index 0e3728a..c14d9d5 100644
--- a/src/xcb_util.c
+++ b/src/xcb_util.c
@@ -64,6 +64,16 @@ int xcb_popcount(uint32_t mask)
     return ((y + (y >> 3)) & 030707070707) % 077;
 }
 
+int xcb_sumof(uint8_t *list, int len)
+{
+  int i, s = 0;
+  for(i=0; i<len; i++) {
+    s += *list;
+    list++;
+  }
+  return s;
+}
+
 static int _xcb_parse_display(const char *name, char **host, char **protocol,
                       int *displayp, int *screenp)
 {
diff --git a/src/xcbext.h b/src/xcbext.h
index 2e10ba2..eb69538 100644
--- a/src/xcbext.h
+++ b/src/xcbext.h
@@ -86,6 +86,7 @@ int xcb_poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply,
 /* xcb_util.c */
 
 int xcb_popcount(uint32_t mask);
+int xcb_sumof(uint8_t *list, int len);
 
 #ifdef __cplusplus
 }
diff --git a/xcb-xkb.pc.in b/xcb-xkb.pc.in
new file mode 100644
index 0000000..6ed0035
--- /dev/null
+++ b/xcb-xkb.pc.in
@@ -0,0 +1,11 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: XCB XKB
+Description: XCB Keyboard Extension (EXPERIMENTAL)
+Version: @PACKAGE_VERSION@
+Requires: xcb
+Libs: -L${libdir} -lxcb-xkb
+Cflags: -I${includedir}