rs_client.py

#!/usr/bin/env python3
# Copyright (c) 2016 Remi Thebault <remi.thebault@gmail.com>
#
# Permission is hereby granted, free of charge, to any
# person obtaining a copy of this software and associated
# documentation files (the "Software"), to deal in the
# Software without restriction, including without
# limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of
# the Software, and to permit persons to whom the Software
# is furnished to do so, subject to the following
# conditions:
#
# The above copyright notice and this permission notice
# shall be included in all copies or substantial portions
# of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
# ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
# TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
# IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
# DEALINGS IN THE SOFTWARE.
'''
script that generates rust code from xcb xml definitions
Each invokation of this script generates one ffi file and one
rust file for an extension or the main X Protocol.

Usage: ./rs_client.py -o src xml/xproto.xml
'''

import sys
import os
import re



class SourceFile(object):
    '''
    buffer to append code in various sections of a file
    in any order
    '''

    _one_indent_level = '    '

    def __init__(self):
        self._section = 0
        self._lines = []
        self._indents = []

    def getsection(self):
        return self._section

    def section(self, section):
        '''
        Set the section of the file where to append code.
        Allows to make different sections in the file to append
        to in any order
        '''
        while len(self._lines) <= section:
            self._lines.append([])
        while len(self._indents) <= section:
            self._indents.append(0)
        self._section = section

    def getindent(self):
        '''
        returns indentation of the current section
        '''
        return self._indents[self._section]

    def setindent(self, indent):
        '''
        sets indentation of the current section
        '''
        self._indents[self._section] = indent;

    def indent_block(self):
        class Indenter(object):
            def __init__(self, sf):
                self.sf = sf
            def __enter__(self):
                self.sf.indent()
            def __exit__(self, type, value, traceback):
                self.sf.unindent()
        return Indenter(self)

    def indent(self):
        '''
        adds one level of indentation to the current section
        '''
        self._indents[self._section] += 1

    def unindent(self):
        '''
        removes one level of indentation to the current section
        '''
        assert self.getindent() > 0, "negative indent"
        self._indents[self._section] -= 1

    def __call__(self, fmt, *args):
        '''
        Append a line to the file at in its current section and
        indentation of the current section
        '''
        indent = SourceFile._one_indent_level * self._indents[self._section]
        self._lines[self._section].append(indent + (fmt % args))


    def writeout(self, path):
        with open(path, 'w') as f:
            for section in self._lines:
                for line in section:
                    print(line.rstrip(), file=f)


# FFI source file
_f = SourceFile()

# Rust interface file
_r = SourceFile()

# utility to add same code in both files
def _rf(fmt, *args):
    _f(fmt, *args)
    _r(fmt, *args)


_ns = None
_ext_names = {}

# global variable to keep track of serializers and
# switch data types due to weird dependencies
finished_serializers = []
finished_sizeof = []
finished_switch = []

_types_uneligible_to_copy = []

# current handler is used for error reporting
current_handler = None

# Keep tracks of types that have lifetime parameter
# Initialized with types that are defined in one module and used in other modules
types_with_lifetime = [
    "xcb_str_iterator_t",                   # defined in xproto, used in render
    "xcb_xv_image_format_info_iterator_t"   # defined in xv, used in xvmc
]

# link exceptions
link_exceptions = {
    "bigreq": "xcb",
    "xc_misc": "xcb"
}


#type translation
_ffi_type_translation = {
    'BOOL': 'u8'
}
_rs_type_translation = {
    'BOOL': 'bool'
}

# struct with only simple fields are defined as typedef to the ffi struct (issue #7)
# this list adds exception to this behavior
_rs_typedef_exceptions = [
    # not strictly necessary has Setup has complex fields
    # however intent is clear: 'xproto::Setup' MUST use StructPtr
    'xproto::Setup'
]

# exported functions to xcbgen start by 'rs_'

# starting with opening and closing

def rs_open(module):
    '''
    Handles module open.
    module is a xcbgen.state.Module object
    '''
    global _ns
    _ns = module.namespace

    linklib = "xcb"
    if _ns.is_ext:
        linklib = 'xcb-' + _ns.header
        _ext_names[_ns.ext_name.lower()] = _ns.header
        for (n, h) in module.direct_imports:
            if h != 'xproto':
                _ext_names[n.lower()] = h

    if _ns.header in link_exceptions:
        linklib = link_exceptions[_ns.header]

    ext_id_name = _ffi_name(_ns.prefix + ('id',))

    _r.section(0)
    _f.section(0)
    _rf('// Generated automatically from %s by rs_client.py version %s.',
            _ns.file, os.getenv('CARGO_PKG_VERSION', 'undefined'))
    _rf('// Do not edit!')
    _rf('')

    _f('')
    _f('#![allow(improper_ctypes)]')
    _f('')
    _f('use ffi::base::*;')

    if _ns.is_ext:
        for (n, h) in module.imports:
            _f('use ffi::%s::*;', _module_name(n))
        _f('')
    _f('use libc::{c_char, c_int, c_uint, c_void};')
    _f('use std;')
    _f('')

    _f.section(1)
    _f('')
    _f('')
    _f('#[link(name="%s")]', linklib)
    _f('extern {')
    _f.indent()
    if _ns.is_ext:
        _f('')
        _f('pub static mut %s: xcb_extension_t;', ext_id_name)


    _r('#![allow(unused_unsafe)]')
    _r('')
    _r('use base;')
    if _ns.is_ext:
        for (n, h) in module.imports:
            _r('use %s;', _module_name(n))
    _r('use ffi::base::*;')
    _r('use ffi::%s::*;', _module_name(_ns.ext_name))
    if _ns.is_ext:
        for (n, h) in module.imports:
            _r('use ffi::%s::*;', _module_name(n))
    _r('use libc::{self, c_char, c_int, c_uint, c_void};')
    _r('use std;')
    _r('use std::iter::Iterator;')
    _r('')
    if _ns.is_ext:
        _r('')
        _r("pub fn id() -> &'static mut base::Extension {")
        _r('    unsafe {')
        _r('        &mut %s', ext_id_name)
        _r('    }')
        _r('}')

    _r.section(1)
    _r('')
    _r('')



    if _ns.is_ext:
        _f.section(0)
        _f('')
        _f('pub const %s: u32 = %s;',
                    _ffi_const_name(('xcb', _ns.ext_name, 'major', 'version')),
                    _ns.major_version)
        _f('pub const %s: u32 = %s;',
                    _ffi_const_name(('xcb', _ns.ext_name, 'minor', 'version')),
                    _ns.minor_version)

        _r.section(0)
        _r('')
        _r('pub const MAJOR_VERSION: u32 = %s;', _ns.major_version)
        _r('pub const MINOR_VERSION: u32 = %s;', _ns.minor_version)



    EnumCodegen.build_collision_table(module)




def rs_close(module):
    '''
    Handles module close.
    module is a xcbgen.state.Module object.
    main task is to write the files out
    '''

    _f.section(1)

    _f('')
    _f.unindent()
    _f('} // extern')

    _f.writeout(os.path.join(module.rs_srcdir, "ffi", "%s.rs" % _module_name(_ns.ext_name)))
    _r.writeout(os.path.join(module.rs_srcdir, "%s.rs" % _module_name(_ns.ext_name)))



# transformation of name tuples

_cname_re = re.compile('([A-Z0-9][a-z]+|[A-Z0-9]+(?![a-z])|[a-z]+)')
_rs_keywords = ['type', 'str', 'match', 'new']


def _tit_split(string):
    '''
    splits string with '_' on each titlecase letter
    >>> _tit_split('SomeString')
    Some_String
    >>> _tit_split('WINDOW')
    WINDOW
    '''
    split = _cname_re.finditer(string)
    name_parts = [match.group(0) for match in split]
    return '_'.join(name_parts)

def _tit_cap(string):
    '''
    capitalize each substring beggining by a titlecase letter
    >>> _tit_cap('SomeString')
    SomeString
    >>> _tit_cap('WINDOW')
    Window
    '''
    split = _cname_re.finditer(string)
    name_parts = [match.group(0) for match in split]
    name_parts = [i[0].upper() + i[1:].lower() for i in name_parts]
    return ''.join(name_parts)


_extension_special_cases = ['XPrint', 'XCMisc', 'BigRequests']

def _module_name(name):
    if len(name):
        if name in _extension_special_cases:
            return _tit_split(name).lower()
        else:
            return name.lower()
    else:
        return 'xproto'


def _symbol(string):
    if string in _rs_keywords:
        string += '_'
    return string

def _upper_1st(string):
    '''
    return copy of string with first letter turned into upper.
    Other letters are untouched.
    '''
    if len(string) == 0:
        return ''
    if len(string) == 1:
        return string.upper()
    return string[0].upper() + string[1:]

def _upper_name(nametup):
    '''
    return a string made from a nametuple with all upper case
    joined with underscore
    >>> _upper_name(('xcb', 'constant', 'AwesomeValue'))
    XCB_CONSTANT_AWESOME_VALUE
    '''
    return '_'.join(tuple(_tit_split(name) for name in nametup)).upper()

def _cap_name(nametup):
    '''
    return a string made from a nametuple with joined title case
    >>> _cap_name(('xcb', 'Type', 'Name'))
    XcbTypeName
    >>> _cap_name(('xcb', 'TypeName'))
    XcbTypeName
    >>> _cap_name(('xcb', 'TYPENAME'))
    XcbTypename
    '''
    return ''.join(tuple(_upper_1st(name) for name in nametup))

def _lower_name(nametup):
    '''
    return a string made from a nametuple with all lower case
    joined with underscore
    >>> _upper_name(('xcb', 'Ext', 'RequestName'))
    xcb_ext_request_name
    '''
    return '_'.join(tuple(_tit_split(name) for name in nametup)).lower()


def _ext_nametup(nametup):
    '''
    return the nametup with 2nd name lowered if module is an extension
    >>> _ext_nametup(('u32',))
    ('u32',)
    >>> _ext_nametup(('xcb', 'XprotoType'))
    ('xcb', 'XprotoType')
    >>> _ext_nametup(('xcb', 'RandR', 'SuperType'))
    ('xcb', 'randr', 'SuperType')
    '''
    if len(nametup) > 2 and nametup[1].lower() in _ext_names:
        #nametup = tuple(_ext_names[name.lower()] if i == 1 else name
        #        for (i, name) in enumerate(nametup))
        # lowers extension to avoid '_' split with title letters
        nametup = tuple(_module_name(name) if i == 1 else name
                for (i, name) in enumerate(nametup))
    return nametup

def _ffi_type_name(nametup):
    '''
    turns the nametup into a FFI type
    >>> _ffi_type_name(('u32',))
    u32
    >>> _ffi_type_name(('xcb', 'XprotoType'))
    xcb_xproto_type_t
    >>> _ffi_type_name(('xcb', 'RandR', 'SuperType'))
    xcb_randr_super_type_t
    '''
    if len(nametup) == 1:
        # handles SimpleType
        if nametup[0] in _ffi_type_translation:
            return _ffi_type_translation[nametup[0]]
        return nametup[0]
    return _ffi_name(nametup + ('t',))


def _ffi_name(nametup):
    '''
    turns the nametup into a FFI name
    >>> _ffi_type_name(('u32',))
    u32
    >>> _ffi_type_name(('xcb', 'XprotoType', 't'))
    xcb_xproto_type_t
    >>> _ffi_type_name(('xcb', 'RandR', 'SuperType', 't'))
    xcb_randr_super_type_t
    '''
    secondIsExt = (len(nametup) > 2 and nametup[1].lower() in _ext_names)
    nametup = _ext_nametup(nametup)

    if secondIsExt:
        return '_'.join(tuple(name if i==1 else _tit_split(name)
                for (i, name) in enumerate(nametup))).lower()
    else:
        return '_'.join(tuple(_tit_split(name) for name in nametup)).lower()


def _ffi_const_name(nametup):
    return _ffi_name(_ext_nametup(nametup)).upper()


def _rs_extract_module(nametup):
    '''
    returns the module extracted from nametup
    along with the nametup without the module parts
    if module is local module, an empty module is returned
    >>> _rs_extract_module(('u32',))
    ("", "u32")
    >>> _rs_extract_module(('xcb', 'Type'))
    ("", ("Type"))
    >>> _rs_extract_module(('xcb', 'RandR', 'SuperType'))
    ("randr::", ("SuperType"))
    '''
    # handles SimpleType
    if len(nametup) == 1:
        return ("", nametup[0])

    # remove 'xcb'
    if nametup[0].lower() == 'xcb':
        nametup = nametup[1:]

    module = ''
    # handle extension type
    if nametup[0].lower() in _ext_names:
        ext = _ext_names[nametup[0].lower()]
        if (not _ns.is_ext or
                ext != _ns.header):
            module = ext + '::'
        nametup = nametup[1:]

    # handle xproto type for extensions
    else:
        if _ns.is_ext:
            module = 'xproto::'

    return (module, nametup)



def _rs_type_name(nametup):
    '''
    turns the nametup into a Rust type name
    foreign rust type names include module prefix
    >>> _rs_type_name(('u32',))
    u32
    >>> _rs_type_name(('xcb', 'Type'))
    xproto::Type
    >>> _rs_type_name(('xcb', 'RandR', 'SuperType'))
    randr::SuperType
    '''
    if len(nametup) == 1:
        if nametup[0] in _rs_type_translation:
            return _rs_type_translation[nametup[0]]
        return nametup[0]

    (module, nametup) = _rs_extract_module(nametup)

    return module + ''.join([_tit_cap(n) for n in nametup])


def _rs_name(nametup):

    (module, nametup) = _rs_extract_module(nametup)

    return module + '_'.join([_tit_split(n) for n in nametup]).lower()


def _rs_const_name(nametup):
    return _upper_name(_rs_extract_module(nametup)[1])

def _rs_field_name(string):
    res = ''
    for c in string:
        if c.isupper():
            res = res + '_' + c.lower()
        else:
            res = res + c
    return res


def _set_type_lifetime(typeobj, has_lifetime):
    typeobj.has_lifetime = has_lifetime

    # handle successive calls to _set_type_lifetime on the same object
    def ensure_in(val):
        if not val in types_with_lifetime:
            types_with_lifetime.append(val)

    def ensure_out(val):
        while val in types_with_lifetime:
            types_with_lifetime.remove(val)

    if has_lifetime:
        ensure_in(typeobj.ffi_iterator_type)
        ensure_in(typeobj.rs_type)
        ensure_in(typeobj.rs_iterator_type)
    else:
        ensure_out(typeobj.ffi_iterator_type)
        ensure_out(typeobj.rs_type)
        ensure_out(typeobj.rs_iterator_type)



# FFI codegen functions

def _ffi_type_setup(typeobj, nametup, suffix=()):
    '''
    Sets up all the C-related state by adding additional data fields to
    all Field and Type objects.  Here is where we figure out most of our
    variable and function names.

    Recurses into child fields and list member types.
    '''
    # Do all the various names in advance
    typeobj.ffi_type = _ffi_type_name(nametup + suffix)

    typeobj.ffi_iterator_type = _ffi_type_name(nametup + ('iterator',))
    typeobj.ffi_next_fn = _ffi_name(nametup + ('next',))
    typeobj.ffi_end_fn = _ffi_name(nametup + ('end',))

    typeobj.ffi_request_fn = _ffi_name(nametup)
    typeobj.ffi_checked_fn = _ffi_name(nametup + ('checked',))
    typeobj.ffi_unchecked_fn = _ffi_name(nametup + ('unchecked',))
    typeobj.ffi_reply_fn = _ffi_name(nametup + ('reply',))
    typeobj.ffi_reply_type = _ffi_type_name(nametup + ('reply',))
    typeobj.ffi_cookie_type = _ffi_type_name(nametup + ('cookie',))
    typeobj.ffi_reply_fds_fn = _ffi_name(nametup + ('reply_fds',))

    typeobj.ffi_need_aux = False
    typeobj.ffi_need_serialize = False
    typeobj.ffi_need_sizeof = False

    typeobj.ffi_aux_fn = _ffi_name(nametup + ('aux',))
    typeobj.ffi_aux_checked_fn = _ffi_name(nametup + ('aux', 'checked'))
    typeobj.ffi_aux_unchecked_fn = _ffi_name(nametup + ('aux', 'unchecked'))
    typeobj.ffi_serialize_fn = _ffi_name(nametup + ('serialize',))
    typeobj.ffi_unserialize_fn = _ffi_name(nametup + ('unserialize',))
    typeobj.ffi_unpack_fn = _ffi_name(nametup + ('unpack',))
    typeobj.ffi_sizeof_fn = _ffi_name(nametup + ('sizeof',))

    # special case: structs where variable size fields are followed
    # by fixed size fields
    typeobj.ffi_var_followed_by_fixed_fields = False

    if not typeobj.fixed_size():
        if not typeobj in _types_uneligible_to_copy:
            _types_uneligible_to_copy.append(typeobj)
        if hasattr(typeobj, 'parents'):
            for p in typeobj.parents:
                _types_uneligible_to_copy.append(p)


    if typeobj.is_container:

        prev_varsized_field = None
        prev_varsized_offset = 0
        first_field_after_varsized = None

        for field in typeobj.fields:
            _ffi_type_setup(field.type, field.field_type, ())
            if field.type.is_list:
                _ffi_type_setup(field.type.member, field.field_type, ())
                if (field.type.nmemb is None):
                    typeobj.ffi_need_sizeof = True

            field.ffi_field_type = _ffi_type_name(field.field_type)
            field.ffi_field_name = _symbol(field.field_name)
            field.has_subscript = (field.type.nmemb and
                            field.type.nmemb > 1)
            field.ffi_need_const = (field.type.nmemb != 1)
            field.ffi_need_pointer = (field.type.nmemb != 1)

            # correct the need_pointer field for variable size non-list types
            if not field.type.fixed_size():
                field.ffi_need_pointer = True
            if field.type.is_list and not field.type.member.fixed_size():
                field.ffi_need_pointer = True

            if field.type.is_switch:
                field.ffi_need_const = True
                field.ffi_need_pointer = True
                field.ffi_need_aux = True
            elif not field.type.fixed_size() and not field.type.is_bitcase:
                typeobj.ffi_need_sizeof = True

            field.ffi_iterator_type = _ffi_type_name(
                    field.field_type + ('iterator',))
            field.ffi_iterator_fn = _ffi_name(
                    nametup + (field.field_name, 'iterator'))
            field.ffi_accessor_fn = _ffi_name(
                    nametup + (field.field_name,))
            field.ffi_length_fn = _ffi_name(
                    nametup + (field.field_name, 'length'))
            field.ffi_end_fn = _ffi_name(
                    nametup + (field.field_name, 'end'))

            field.prev_varsized_field = prev_varsized_field
            field.prev_varsized_offset = prev_varsized_offset

            if prev_varsized_offset == 0:
                first_field_after_varsized = field
            field.first_field_after_varsized = first_field_after_varsized

            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 typeobj.is_union:
                        typeobj.ffi_need_serialize = True
                        typeobj.ffi_var_followed_by_fixed_fields = True
            else:
                typeobj.last_varsized_field = field
                prev_varsized_field = field
                prev_varsized_offset = 0

            if typeobj.ffi_var_followed_by_fixed_fields:
                if field.type.fixed_size():
                    field.prev_varsized_field = None

    if typeobj.ffi_need_serialize:
        # when _unserialize() is wanted, create _sizeof() as well
        # for consistency reasons
        typeobj.ffi_need_sizeof = True

    if not typeobj.is_bitcase:
        if typeobj.ffi_need_serialize:
            if typeobj.ffi_serialize_fn not in finished_serializers:
                finished_serializers.append(typeobj.ffi_serialize_fn)
                #_ffi_serialize('serialize', typeobj)

                # _unpack() and _unserialize() are only needed
                # for special cases:
                #   switch -> unpack
                #   special cases -> unserialize
                if (typeobj.is_switch or
                        typeobj.ffi_var_followed_by_fixed_fields):
                    pass
                    #_ffi_serialize('unserialize', typeobj)

        if typeobj.ffi_need_sizeof:
            if typeobj.ffi_sizeof_fn not in finished_sizeof:
                if not _ns.is_ext or typeobj.name[:2] == _ns.prefix:
                    finished_sizeof.append(typeobj.ffi_sizeof_fn)
                    #_ffi_serialize('sizeof', typeobj)




def _ffi_bitcase_name(switch, bitcase):
    assert switch.is_switch and bitcase.type.has_name
    switch_name = _lower_name(_ext_nametup(switch.name))
    return '_%s__%s' % (switch_name, bitcase.ffi_field_name)


def _ffi_struct(typeobj, must_pack=False):
    '''
    Helper function for handling all structure types.
    Called for structs, requests, replies, events, errors...
    '''

    struct_fields = []

    for field in typeobj.fields:
        if (not field.type.fixed_size()
            and not typeobj.is_switch
            and not typeobj.is_union):
            continue
        if field.wire:
            struct_fields.append(field)

    _f.section(0)
    _f('')
    _write_doc_brief_desc(_f, typeobj.doc)
    _f('#[repr(C%s)]', ', packed' if must_pack else '')
    _f('pub struct %s {', typeobj.ffi_type)
    _f.indent()

    maxfieldlen = 0
    if not typeobj.is_switch:
        for field in typeobj.fields:
            maxfieldlen = max(maxfieldlen, len(field.ffi_field_name))
    else:
        for b in typeobj.bitcases:
            if b.type.has_name:
                maxfieldlen = max(maxfieldlen, len(b.ffi_field_name))
            else:
                for field in b.type.fields:
                    maxfieldlen = max(maxfieldlen, len(field.ffi_field_name))



    def _ffi_struct_field(field):
        ftype = field.ffi_field_type
        space = ' '* (maxfieldlen - len(field.ffi_field_name))
        if (field.type.fixed_size() or typeobj.is_union or
            # in case of switch with switch children,
            # don't make the field a pointer
            # necessary for unserialize to work
            (typeobj.is_switch and field.type.is_switch)):
            if field.has_subscript:
                ftype = '[%s; %d]' % (ftype, field.type.nmemb)
            _f('pub %s: %s%s,', field.ffi_field_name, space, ftype)
        else:
            assert not field.has_subscript
            _f('pub %s: %s*mut %s,', field.ffi_field_name, space, ftype)

    named_bitcases = []

    if not typeobj.is_switch:
        for field in struct_fields:
            for d in typeobj.doc.fields[field.field_name]:
                _f('/// %s', d)
            _ffi_struct_field(field)
    else:
        for b in typeobj.bitcases:
            if b.type.has_name:
                named_bitcases.append(b)
                space = ' ' * (maxfieldlen - len(b.ffi_field_name))
                _f('pub %s: %s%s,', b.ffi_field_name, space,
                        _ffi_bitcase_name(typeobj, b))
            else:
                for field in b.type.fields:
                    _ffi_struct_field(field)

    _f.unindent()
    _f('}')
    if not typeobj in _types_uneligible_to_copy:
        _f('')
        _f('impl Copy for %s {}', typeobj.ffi_type)
        _f('impl Clone for %s {', typeobj.ffi_type)
        _f('    fn clone(&self) -> %s { *self }', typeobj.ffi_type)
        _f('}')

    for b in named_bitcases:
        _f('')
        _f('#[repr(C)]')
        _f('pub struct %s {', _ffi_bitcase_name(typeobj, b))
        _f.indent()
        maxfieldlen = 0
        for field in b.type.fields:
            maxfieldlen = max(maxfieldlen, len(field.ffi_field_name))
        for field in b.type.fields:
            _ffi_struct_field(field)
        _f.unindent()
        _f('}')



def _ffi_accessors_list(typeobj, field):
    '''
    Declares the accessor functions for a list field.
    Declares a direct-accessor function only if the list members
        are fixed size.
    Declares length and get-iterator functions always.
    '''

    list = field.type
    ffi_type = typeobj.ffi_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 = typeobj if typeobj.is_switch else None
    if typeobj.is_bitcase:
        switch_obj = typeobj.parents[-1]
    if switch_obj is not None:
        ffi_type = switch_obj.ffi_type

    params = []
    parents = typeobj.parents if hasattr(typeobj, 'parents') else [typeobj]
    # 'R': parents[0] is always the 'toplevel' container type
    params.append(('R: *const %s' % parents[0].ffi_type, parents[0]))
    # 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(('S: *const %s' % toplevel_switch.ffi_type,
                toplevel_switch))

        # auxiliary object for 'S' parameter
        S_obj = parents[1]

    _f.section(1)
    if list.member.fixed_size():
        idx = 1 if switch_obj is not None else 0
        _f('')
        _f('pub fn %s (%s)', field.ffi_accessor_fn, params[idx][0])
        _f('        -> *mut %s;', field.ffi_field_type)

    def _may_switch_fn(fn_name, return_type):
        _f('')
        has_lifetime = return_type in types_with_lifetime
        lifetime = "<'a>" if has_lifetime else ""
        if switch_obj is not None:
            fn_start = 'pub fn %s%s (' % (fn_name, lifetime)
            spacing = ' '*len(fn_start)
            _f('%sR: *const %s,', fn_start, R_obj.ffi_type)
            _f('%sS: *const %s)', spacing, S_obj.ffi_type)
            _f('        -> %s%s;', return_type, lifetime)
        else:
            _f('pub fn %s%s (R: *const %s)', fn_name, lifetime, ffi_type)
            _f('        -> %s%s;', return_type, lifetime)

    _may_switch_fn(field.ffi_length_fn, 'c_int')

    if field.type.member.is_simple:
        _may_switch_fn(field.ffi_end_fn, 'xcb_generic_iterator_t')
    else:
        _may_switch_fn(field.ffi_iterator_fn, field.ffi_iterator_type)



def _ffi_accessors_field(typeobj, field):
    '''
    Declares the accessor functions for a non-list field that follows
    a variable-length field.
    '''
    ffi_type = typeobj.ffi_type

    # special case: switch
    switch_obj = typeobj if typeobj.is_switch else None
    if typeobj.is_bitcase:
        switch_obj = typeobj.parents[-1]
    if switch_obj is not None:
        ffi_type = switch_obj.ffi_type

    _f.section(1)
    if field.type.is_simple:
        _f('')
        _f('pub fn %s (R: *const %s)', field.ffi_accessor_fn, ffi_type)
        _f('        -> %s;', field.ffi_field_type)
    else:
        if field.type.is_switch and switch_obj is None:
            return_type = '*mut c_void'
        else:
            return_type = '*mut %s' % field.ffi_field_type

        _f('')
        _f('pub fn %s (R: *const %s)', field.ffi_accessor_fn, ffi_type)
        _f('        -> %s;', return_type)


def _ffi_accessors(typeobj, nametup):
    for field in typeobj.fields:
        if not field.type.is_pad:
            if field.type.is_list and not field.type.fixed_size():
                _ffi_accessors_list(typeobj, field)
            elif (field.prev_varsized_field is not None
                    or not field.type.fixed_size()):
                _ffi_accessors_field(typeobj, field)


def _ffi_iterator(typeobj, nametup):

    has_lifetime = typeobj.ffi_iterator_type in types_with_lifetime
    lifetime = "<'a>" if has_lifetime else ""

    _f.section(0)
    _f('')
    _f('#[repr(C)]')
    _f("pub struct %s%s {", typeobj.ffi_iterator_type, lifetime)
    _f('    pub data:  *mut %s,', typeobj.ffi_type)
    _f('    pub rem:   c_int,')
    _f('    pub index: c_int,')
    if has_lifetime:
        _f("    _phantom:  std::marker::PhantomData<&'a %s>,", typeobj.ffi_type)
    _f('}')

    _f.section(1)
    _f('')
    _f('pub fn %s (i: *mut %s);', typeobj.ffi_next_fn,
            typeobj.ffi_iterator_type)

    _f('')
    _f('pub fn %s (i: *mut %s)', typeobj.ffi_end_fn,
            typeobj.ffi_iterator_type)
    _f('        -> xcb_generic_iterator_t;')




def _ffi_reply(request):
    '''
    Declares the function that returns the reply structure.
    '''
    _f.section(1)
    _f('')
    _f('/// the returned value must be freed by the caller using ' +
            'libc::free().')
    fn_start = 'pub fn %s (' % request.ffi_reply_fn
    spacing = ' ' * len(fn_start)
    _f('%sc:      *mut xcb_connection_t,', fn_start)
    _f('%scookie: %s,', spacing, request.ffi_cookie_type)
    _f('%serror:  *mut *mut xcb_generic_error_t)', spacing)
    _f('        -> *mut %s;', request.ffi_reply_type)


def _ffi_reply_has_fds(self):
    for field in self.fields:
        if field.isfd:
            return True
    return False


def _ffi_reply_fds(request, name):
    '''
    Declares the function that returns fds related to the reply.
    '''
    _f.section(1)
    _f('')
    _f('/// the returned value must be freed by the caller using ' +
            'libc::free().')
    fn_start = 'pub fn %s (' % request.ffi_reply_fds_fn
    spacing = ' ' * len(fn_start)
    _f('%sc:     *mut xcb_connection_t,', fn_start)
    _f('%sreply: *mut %s)', spacing, request.ffi_reply_type)
    _f('        -> *mut c_int;')



# Rust codegen function

def _rs_type_setup(typeobj, nametup, suffix=()):
    #assert typeobj.hasattr('ffi_type')

    typeobj.rs_type = _rs_type_name(nametup + suffix)

    if len(nametup) == 1:
        typeobj.rs_qualified_type = typeobj.rs_type
    else:
        module = _ns.ext_name.lower() if _ns.is_ext else 'xproto'
        typeobj.rs_qualified_type = '%s::%s' % (module, typeobj.rs_type)

    typeobj.rs_iterator_type = _rs_type_name(nametup+('iterator',))
    typeobj.rs_request_fn = _rs_name(nametup)
    typeobj.rs_checked_fn = _rs_name(nametup+('checked',))
    typeobj.rs_unchecked_fn = _rs_name(nametup+('unchecked',))

    typeobj.rs_aux_fn = _rs_name(nametup+('aux',))
    typeobj.rs_aux_checked_fn = _rs_name(nametup+('aux', 'checked'))
    typeobj.rs_aux_unchecked_fn = _rs_name(nametup+('aux', 'unchecked'))
    typeobj.rs_reply_type = _rs_type_name(nametup + ('reply',))
    typeobj.rs_cookie_type = _rs_type_name(nametup + ('cookie',))

    typeobj.rs_is_pod = False

    if typeobj.is_container:
        has_complex = False
        for field in typeobj.fields:
            _rs_type_setup(field.type, field.field_type)
            if field.type.is_list:
                _rs_type_setup(field.type.member, field.field_type)
            field.rs_field_name = _symbol(_rs_field_name(field.field_name))
            field.rs_field_type = _rs_type_name(field.field_type)

            field.rs_iterator_type = _rs_type_name(
                    field.field_type + ('iterator',))

            if not field.type.is_simple and not field.type.rs_is_pod \
                    and not field.type.is_pad:
                has_complex = True

        typeobj.rs_only_has_simple = not has_complex
        # we restrict POD a little
        typeobj.rs_is_pod = (
                (not has_complex) and
                (not typeobj.rs_qualified_type in _rs_typedef_exceptions) and
                (not typeobj.is_reply and not typeobj.is_union) and
                (not typeobj.is_switch))

        if typeobj.rs_is_pod:
            _set_type_lifetime(typeobj, False)



def _rs_struct(typeobj):
    _r.section(1)
    _r('')
    _write_doc_brief_desc(_r, typeobj.doc)
    if typeobj.rs_is_pod:
        _r('#[derive(Copy, Clone)]')
        _r('pub struct %s {', typeobj.rs_type)
        _r('    pub base: %s,', typeobj.ffi_type)
        _r('}')
    else:
        has_lifetime = typeobj.rs_type in types_with_lifetime
        lifetime1 = "<'a>" if has_lifetime else ""
        lifetime2 = "'a, " if has_lifetime else ""

        _r("pub type %s%s = base::StructPtr<%s%s>;", typeobj.rs_type, lifetime1,
                lifetime2, typeobj.ffi_type)


def _rs_accessors(typeobj):

    has_lifetime = typeobj.rs_type in types_with_lifetime
    lifetime = "<'a>" if has_lifetime else ""

    _r.section(1)
    _r('')
    _r('impl%s %s%s {', lifetime, typeobj.rs_type, lifetime)
    with _r.indent_block():
        if typeobj.rs_is_pod:
            # POD structs have a new method
            fnstart = 'pub fn new('
            fnspace = ' '*len(fnstart)
            argfields = []
            for f in typeobj.fields:
                if not f.type.is_pad:
                    argfields.append(f)
            maxfieldlen = 0
            for f in typeobj.fields:
                maxfieldlen = max(maxfieldlen, len(f.rs_field_name))
            if len(argfields):
                eol = ',' if len(argfields) > 1 else ')'
                f1 = argfields[0]
                space1 = ' '*(maxfieldlen - len(f1.rs_field_name))
                _r('#[allow(unused_unsafe)]')
                _r('%s%s: %s%s%s', fnstart, f1.rs_field_name, space1, f1.rs_field_type, eol)
                for (i, f) in enumerate(argfields[1:]):
                    argspace = ' '*(maxfieldlen-len(f.rs_field_name))
                    eol = ',' if i < len(argfields)-2 else ')'
                    _r('%s%s: %s%s%s', fnspace, f.rs_field_name, argspace, f.rs_field_type, eol)
                _r('        -> %s {', typeobj.rs_type)
            else:
                _r('#[allow(unused_unsafe)]')
                _r('%s) -> %s {', fnstart, typeobj.rs_type)

            with _r.indent_block():
                _r('unsafe {')
                with _r.indent_block():
                    _r('%s {', typeobj.rs_type)
                    with _r.indent_block():
                        _r('base: %s {', typeobj.ffi_type)
                        with _r.indent_block():
                            for f in typeobj.fields:
                                space = ' '*(maxfieldlen-len(f.rs_field_name))
                                if f.type.rs_is_pod:
                                    _r('%s: %sstd::mem::transmute(%s),', f.rs_field_name, space, f.rs_field_name)
                                elif f.type.is_pad:
                                    fval = '0'
                                    if f.has_subscript:
                                        fval = '[0; %d]' % f.type.nmemb
                                    _r('%s: %s%s,', f.rs_field_name, space, fval)
                                else:
                                    assignment = f.rs_field_name
                                    if f.rs_field_type == 'bool':
                                        assignment = 'if %s { 1 } else { 0 }' % f.rs_field_name
                                    _r('%s: %s%s,', f.ffi_field_name, space, assignment)
                        _r('}')
                    _r('}')
                _r('}')
            _r('}')

        for (i, field) in enumerate(typeobj.fields):
            if field.visible and not field.type.is_switch:
                for d in typeobj.doc.fields[field.field_name]:
                    _r('/// %s', d)
                if typeobj.is_union:
                    _rs_union_accessor(typeobj, field)
                else:
                    _rs_accessor(typeobj, field)
    _r('}')


def _rs_reply_accessors(reply):
    '''
    same as _rs_accessors but handles fds special case
    '''
    has_lifetime = reply.rs_type in types_with_lifetime
    lifetime = "<'a>" if has_lifetime else ""

    fd_field = None
    nfd_field = None
    for f in reply.fields:
        if f.rs_field_name == 'nfd':
            nfd_field = f
        if f.isfd:
            fd_field = f

    reply_fields = []
    for f in reply.fields:
        if f.rs_field_name == 'nfd':
            # writing nfd field only if fds is not written
            if not fd_field or not nfd_field:
                reply_fields.append(f)
        elif not f.isfd:
            reply_fields.append(f)


    _r.section(1)
    _r('')
    _r('impl%s %s%s {', lifetime, reply.rs_type, lifetime)
    with _r.indent_block():
        # regular fields
        for field in reply_fields:
            if field.visible and not field.type.is_switch:
                _rs_accessor(reply, field)

        # fds field if any
        if nfd_field and fd_field:
            getter = reply.request.ffi_reply_fds_fn
            # adding 's'
            fname = fd_field.rs_field_name
            if not fname.endswith('s'):
                fname += 's'
            _r('pub fn %s(&self, c: &base::Connection) -> &[i32] {', fname)
            with _r.indent_block():
                _r('unsafe {')
                with _r.indent_block():
                    _r('let nfd = (*self.ptr).nfd as usize;')
                    _r('let ptr = %s(c.get_raw_conn(), self.ptr);', getter)
                    _r('')
                    _r('std::slice::from_raw_parts(ptr, nfd)')
                _r('}')
            _r('}')
    _r('}')


def _rs_union_accessor(typeobj, field):
    if field.type.is_simple or field.type.rs_is_pod:
        _r('pub fn %s(&self) -> %s {', field.rs_field_name, field.rs_field_type)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                convert = ''
                if field.rs_field_type == 'bool':
                    convert = ' != 0'
                _r('let _ptr = self.data.as_ptr() as *const %s;', field.rs_field_type)
                _r('*_ptr%s', convert)
            _r('}')
        _r('}')
        _r('pub fn from_%s(%s: %s) -> %s {', field.rs_field_name,
                field.rs_field_name, field.rs_field_type, typeobj.rs_type)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                if field.rs_field_type == 'bool':
                    _r('let %s: %s = %s != 0;', field.rs_field_name,
                            field.ffi_field_type, field.rs_field_name)
                _r('let mut res = %s { data: [0; %d] };', typeobj.rs_type,
                        typeobj.union_num_bytes)
                _r('let res_ptr = res.data.as_mut_ptr() as *mut %s;', field.rs_field_type)
                _r('*res_ptr = %s;', field.rs_field_name)
                _r('res')
            _r('}')
        _r('}')


    elif field.type.is_list and field.type.fixed_size():
        assert (typeobj.union_num_bytes % field.type.size) == 0
        _r('pub fn %s(&self) -> &[%s] {',
                field.rs_field_name, field.rs_field_type)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                _r('let ptr = self.data.as_ptr() as *const %s;', field.rs_field_type)
                _r('std::slice::from_raw_parts(ptr, %d)',
                        typeobj.union_num_bytes / field.type.size)
            _r('}')
        _r('}')
        _r('pub fn from_%s(%s: [%s; %d]) -> %s {', field.rs_field_name,
                field.rs_field_name, field.rs_field_type,
                typeobj.union_num_bytes / field.type.size,
                typeobj.rs_type)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                _r('%s { data: std::mem::transmute(%s) }', typeobj.rs_type,
                        field.rs_field_name)
            _r('}')
        _r('}')


    elif field.type.is_container:
        if not field.type.rs_is_pod:
            _r('pub fn %s<\'a>(&\'a self) -> %s<\'a> {',
                    field.rs_field_name, field.rs_field_type)
        else:
            _r('pub fn %s(&self) -> %s {', field.rs_field_name, field.rs_field_type)

        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                if not field.type.rs_is_pod:
                    _r('std::mem::transmute(self)')
                else:
                    _r('let _ptr = self.data.as_ptr() as *const %s;', field.rs_field_type)
                    _r('*_ptr')
            _r('}')
        _r('}')



def _rs_accessor(typeobj, field, disable_pod_acc=False):
    if field.type.is_simple or field.type.rs_is_pod:
        _r('pub fn %s(&self) -> %s {', field.rs_field_name,
                field.rs_field_type)

        acc = '(*self.ptr)'
        if typeobj.rs_is_pod and not disable_pod_acc:
            acc = 'self.base'

        with _r.indent_block():
            convert = ''
            if field.rs_field_type == 'bool':
                convert = ' != 0'
            _r('unsafe {')
            with _r.indent_block():
                if field.type.rs_is_pod:
                    _r('std::mem::transmute(%s.%s)', acc, field.ffi_field_name)
                else:
                    _r('%s.%s%s', acc, field.ffi_field_name, convert)
            _r('}')
        _r('}')

    elif field.type.is_union:
        # do we already have a lifetime declared?
        has_lifetime = typeobj.rs_type in types_with_lifetime
        lifetime = "<'a>" if not has_lifetime else ""
        _r("pub fn %s%s(&'a self) -> &'a %s {", field.rs_field_name, lifetime,
                field.rs_field_type)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                _r('&(*self.ptr).%s', field.ffi_field_name)
            _r('}')
        _r('}')

    elif field.type.is_list and not field.type.fixed_size():
        if field.type.member.rs_type == 'bool':
            # special case for bool: we need to convert all elements into an owned vec
            _r('pub fn %s(&self) -> Vec<bool> {', field.rs_field_name)
            with _r.indent_block():
                _r('unsafe {')
                with _r.indent_block():
                    _r('let field = self.ptr;')
                    _r('let len = %s(field);', field.ffi_length_fn)
                    _r('let data = %s(field);', field.ffi_accessor_fn)
                    _r('let slice = std::slice::from_raw_parts(data, len as usize);')
                    _r('slice.iter().map(|el| if *el == 0 {false} else{true}).collect()')
                _r('}')
            _r('}')
        elif field.type.member.is_simple:
            field_type = field.type.member.rs_type
            is_template = False
            if field_type == 'c_char':
                return_type = '&str'
            elif field_type == 'c_void':
                is_template = True
                return_type = '&[T]'
            else:
                return_type = '&[%s]' % field_type
            _r('pub fn %s%s(&self) -> %s {', field.rs_field_name,
                    '<T>' if is_template else '', return_type)
            with _r.indent_block():
                _r('unsafe {')
                with _r.indent_block():
                    _r('let field = self.ptr;')
                    _r('let len = %s(field) as usize;', field.ffi_length_fn)
                    _r('let data = %s(field);', field.ffi_accessor_fn)
                    if field_type == 'c_char':
                        _r('let slice = ' +
                            'std::slice::from_raw_parts(' +
                                'data as *const u8, len);')
                        _r('// should we check what comes from X?')
                        _r('std::str::from_utf8_unchecked(&slice)')
                    elif is_template:
                        _r('debug_assert_eq!(len %% std::mem::size_of::<T>(), 0);')
                        _r('std::slice::from_raw_parts(data as *const T, ' +
                                'len / std::mem::size_of::<T>())')
                    else:
                        _r('std::slice::from_raw_parts(data, len)')
                _r('}')
            _r('}')
        else:
            lifetime = ""
            if field.rs_iterator_type in types_with_lifetime and \
                    typeobj.rs_type in types_with_lifetime:
                lifetime = "<'a>"
            _r('pub fn %s(&self) -> %s%s {',
                    field.rs_field_name, field.rs_iterator_type, lifetime)
            with _r.indent_block():
                _r('unsafe {')
                with _r.indent_block():
                    _r('%s(self.ptr)', field.ffi_iterator_fn)
                _r('}')
            _r('}')
            pass

    elif field.type.is_list:
        _r('pub fn %s(&self) -> &[%s] {',
                field.rs_field_name, field.rs_field_type)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                _r('&(*self.ptr).%s', field.ffi_field_name)
            _r('}')
        _r('}')

    elif field.type.is_container:
        _r('pub fn %s(&self) -> %s {',
                field.rs_field_name, field.rs_field_type)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                _r('std::mem::transmute(&(*self.ptr).%s)',
                        field.ffi_field_name)
            _r('}')
        _r('}')

    elif not field.type.is_pad:
        raise Exception('did not treat accessor %s.%s'
                % (typeobj.ffi_type, field.ffi_field_name))



def _rs_iterator(typeobj):

    has_lifetime = typeobj.rs_iterator_type in types_with_lifetime
    lifetime1 = "<'a>" if has_lifetime else ""
    lifetime2 = "'a, " if has_lifetime else ""
    return_expr = '*data'
    if typeobj.rs_is_pod:
        return_expr = 'std::mem::transmute(*data)'
    elif typeobj.is_container and not typeobj.is_union:
        return_expr = 'std::mem::transmute(data)'

    _r.section(1)
    _r('')
    _r("pub type %s%s = %s%s;",
            typeobj.rs_iterator_type, lifetime1, typeobj.ffi_iterator_type, lifetime1)

    _r('')
    _r("impl%s Iterator for %s%s {", lifetime1, typeobj.rs_iterator_type, lifetime1)
    _r("    type Item = %s%s;", typeobj.rs_type, lifetime1)
    _r("    fn next(&mut self) -> std::option::Option<%s%s> {",
            typeobj.rs_type, lifetime1)
    _r('        if self.rem == 0 { None }')
    _r('        else {')
    _r('            unsafe {')
    _r('                let iter = self as *mut %s;',
            typeobj.ffi_iterator_type)
    _r('                let data = (*iter).data;')
    _r('                %s(iter);', typeobj.ffi_next_fn)
    _r('                Some(%s)', return_expr)
    _r('            }')
    _r('        }')
    _r('    }')
    _r('}')



def _rs_reply(request):

    _r.section(1)
    _r('')
    _r('pub type %s = base::Reply<%s>;', request.rs_reply_type, request.ffi_reply_type);




# Common codegen utilities

def _prepare_doc(typeobj):
    # preparing doc for easier handling
    # each typeobj must have a doc attribute with brief, description and fields

    def rework_phrase(phrase):
        # having 'unknown start of token' error by rustdoc sometimes.
        # This silents it
        # return phrase.replace('`', '')
        # Edit: not necessary anymore
        return phrase

    if hasattr(typeobj, "doc_prepared"):
        assert typeobj.doc_prepared == True
        return
    if hasattr(typeobj, "doc") and typeobj.doc:
        if typeobj.doc.brief:
            typeobj.doc.brief = [rework_phrase(p) for p in typeobj.doc.brief.split('\n')]
        else:
            typeobj.doc.brief = []
        if typeobj.doc.description:
            typeobj.doc.description = [rework_phrase(p) for p in typeobj.doc.description.split('\n')]
        else:
            typeobj.doc.description = []
        if hasattr(typeobj, "fields"):
            if not hasattr(typeobj.doc, "fields"):
                typeobj.doc.fields = {}
            for f in typeobj.fields:
                if f.field_name in typeobj.doc.fields:
                    typeobj.doc.fields[f.field_name] = \
                            [rework_phrase(p) for p in typeobj.doc.fields[f.field_name].split('\n')]
                else:
                    typeobj.doc.fields[f.field_name] = []
    else:
        class Doc(object): pass
        typeobj.doc = Doc()
        typeobj.doc.brief = []
        typeobj.doc.description = []
        typeobj.doc.fields = {}
        if hasattr(typeobj, "fields"):
            for f in typeobj.fields:
                typeobj.doc.fields[f.field_name] = []

    typeobj.doc_prepared = True


def _write_docs(sf, doclist):
    for s in doclist:
        sf('/// %s', s)


def _write_doc_brief_desc(sf, doc):
    _write_docs(sf, doc.brief)
    if len(doc.brief) and len(doc.description):
        sf('///')
    _write_docs(sf, doc.description)


class EnumCodegen(object):

    namecount = {}

    def build_collision_table(module):
        for v in module.types.values():
            key = _ffi_type_name(v[0])
            EnumCodegen.namecount[key] = (
                (EnumCodegen.namecount.get(key) or 0) + 1
            )


    def __init__(self, nametup, doc):
        self._nametup = nametup
        self._doc = doc

        self.done_vals = {}
        self.unique_discriminants = []
        self.conflicts = []
        self.all_discriminants = []
        key = _ffi_type_name(nametup)
        if EnumCodegen.namecount[key] > 1:
            nametup = nametup + ('enum',)
        self.ffi_name = _ffi_type_name(nametup)
        self.rs_name = _rs_type_name(nametup)


    def add_discriminant(self, name, val):
        class Discriminant: pass
        d = Discriminant()
        #d.rs_name = name
        d.rs_name = _rs_const_name(self._nametup+(name,))
        d.ffi_name = _ffi_const_name(self._nametup+(name,))
        d.valstr = '0x%02x' % val
        d.val = val
        d.doc = None
        if self._doc and name in self._doc.fields:
            d.doc = self._doc.fields[name]
        self.all_discriminants.append(d)
        if val in self.done_vals:
            self.conflicts.append(d)
        else:
            self.done_vals[val] = d
            self.unique_discriminants.append(d)


    def maxlen(self, name_field):
        maxnamelen = 0
        maxvallen = 0
        for d in self.unique_discriminants:
            maxvallen = max(maxvallen, len(d.valstr))
            maxnamelen = max(maxnamelen, len(getattr(d, name_field)))
        return (maxnamelen, maxvallen)


    def write_ffi(self):
        (maxnamelen, maxvallen) = self.maxlen('ffi_name')
        type_name = self.ffi_name
        _f.section(0)
        _f('')
        _write_doc_brief_desc(_f, self._doc)
        _f('pub type %s = u32;', type_name)
        for d in self.all_discriminants:
            d_name = d.ffi_name
            namespace = ' ' * (maxnamelen-len(d_name))
            valspace = ' ' * (maxvallen-len(d.valstr))
            if d.doc:
                ddocs = d.doc.split('\n')
                for dd in ddocs:
                    _f('/// %s', dd)
            _f('pub const %s%s: %s =%s %s;', d_name, namespace, type_name,
                    valspace, d.valstr)

    def write_rs(self):
        (maxnamelen, maxvallen) = self.maxlen("rs_name")
        _r.section(0)
        _r('')
        _write_doc_brief_desc(_r, self._doc)
        _r('pub type %s = u32;', self.rs_name)
        for d in self.all_discriminants:
            namespace = ' ' * (maxnamelen-len(d.rs_name))
            valspace = ' ' * (maxvallen-len(d.valstr))
            if d.doc:
                ddocs = d.doc.split('\n')
                for dd in ddocs:
                    _r('/// %s', dd)
            _r('pub const %s%s: %s =%s %s;', d.rs_name, namespace, self.rs_name,
                    valspace, d.valstr)





class RequestCodegen(object):

    def __init__(self, request):
        self.request = request

        self.void = False if self.request.reply else True

        self.ffi_cookie_type = ('xcb_void_cookie_t' if self.void
                else self.request.ffi_cookie_type)
        self.rs_cookie_type = ('base::VoidCookie' if self.void
                else self.request.rs_cookie_type)

        self.visible_fields = []
        for field in self.request.fields:
            if field.visible:
                self.visible_fields.append(field)

        # for, we do not filter out any visible field,
        # but we must find out if it is pointer, const ...
        self.ffi_params = []
        for field in self.visible_fields:
            self.ffi_params.append(field)


        # Rust is more complicated because of lists
        # here we pack lists in slices

        # there's basically 3 cases:
        # 1. regular fields, passed as-is to the ffi func
        # 2. masked lists (such as create_window event mask)
        #    given to rs slice of tuple (mask, value) and unpacked
        #    into int and pointer to ffi func
        # 3. regular lists, for which a length and a pointer
        #    must be passed to the ffi_func. these are given to
        #    rs by a slice

        # it happens to have 2 or more lists for same length field.
        # in this case, we will make 2 slices and runtime assert same length
        # eg: take a look at render::create_conical_gradient

        rs_num_template = 0
        template_letters = ['T', 'U', 'V', 'W']

        # xproto::send_event is special.
        # the FFI takes an event argument casted to a char*
        # here we are going to require an &Event<T> for the rs func
        self.rs_send_event = False
        if _ns.header == "xproto" and \
                self.request.rs_request_fn.startswith("send_event"):
            self.rs_send_event = True

        for f in self.visible_fields:
            f.rs_is_slice = False
            f.rs_template_let = ''
            f.rs_lenfield = None
            f.rs_is_mask_slice = False
            f.rs_maskfield = None
            f.rs_skip = False

        for (ffi_index, field) in enumerate(self.visible_fields):
            field.ffi_index = ffi_index

            if self.rs_send_event and field.rs_field_name == "event":
                field.rs_template_let = template_letters[rs_num_template]
                rs_num_template += 1

            elif field.type.is_list:

                if field.type.expr.bitfield:
                    # field associated with a mask
                    # eg. create_window last field
                    field.rs_is_mask_slice = True
                else:
                    # regular list with length and ptr
                    field.rs_is_slice = True
                    if field.type.member.rs_type == 'c_void':
                        field.rs_template_let = template_letters[rs_num_template]
                        rs_num_template += 1
                field.rs_lenfield = field.type.expr.lenfield
                if not field.rs_lenfield:
                    len_name = field.type.expr.lenfield_name
                    for f in self.visible_fields:
                        if f.field_name == len_name:
                            field.rs_lenfield = f
                # the mask is mandatory, but not the length (eg c strings)
                if field.rs_is_mask_slice:
                    assert field.rs_lenfield
                if field.rs_lenfield:
                    field.rs_lenfield.rs_skip = True

        self.rs_params = []

        for field in self.visible_fields:
            if not field.rs_skip:
                self.rs_params.append(field)

        self.rs_template = "<'a>"
        if rs_num_template:
            self.rs_template = "<'a"
            for i in range(rs_num_template):
                self.rs_template += ', ' + template_letters[i]
            self.rs_template += '>'

    def ffi_func_name(self, regular, aux):
        checked = self.void and not regular
        unchecked = not self.void and not regular

        if checked:
            func_name = (self.request.ffi_checked_fn if not aux else
                    self.request.ffi_aux_checked_fn)
        elif unchecked:
            func_name = (self.request.ffi_unchecked_fn if not aux else
                    self.request.ffi_aux_unchecked_fn)
        else:
            func_name = (self.request.ffi_request_fn if not aux else
                    self.request.ffi_aux_fn)

        return func_name



    def rs_func_name(self, regular, aux):
        checked = self.void and not regular
        unchecked = not self.void and not regular

        if checked:
            func_name = (self.request.rs_checked_fn if not aux else
                    self.request.rs_aux_checked_fn)
        elif unchecked:
            func_name = (self.request.rs_unchecked_fn if not aux else
                    self.request.rs_aux_unchecked_fn)
        else:
            func_name = (self.request.rs_request_fn if not aux else
                    self.request.rs_aux_fn)

        return func_name

    def ffi_rq_type(self, field, aux):
        ffi_rq_type = field.ffi_field_type
        if field.ffi_need_pointer:
            pointer = '*const ' if field.ffi_need_const else '*mut '
            ffi_rq_type = pointer + ffi_rq_type
        if field.type.ffi_need_serialize and not aux:
            ffi_rq_type = '*const c_void'
        return ffi_rq_type



    def write_ffi_rs(self, regular, aux=False):
        self.write_ffi(regular, aux)
        self.write_rs(regular, aux)


    def write_ffi(self, regular, aux=False):

        ffi_func_name = self.ffi_func_name(regular, aux)

        maxnamelen = 1
        for p in self.ffi_params:
            maxnamelen = max(maxnamelen, len(p.ffi_field_name))

        _f.section(1)
        _f("")
        _write_doc_brief_desc(_f, self.request.doc)
        fn_start = "pub fn %s (" % ffi_func_name
        func_spacing = ' ' * len(fn_start)
        spacing = " " * (maxnamelen-len('c'))
        eol = ',' if len(self.ffi_params) else ')'
        _f("%sc: %s*mut xcb_connection_t%s", fn_start, spacing, eol)

        for (i, p) in enumerate(self.ffi_params):
            ffi_rq_type = self.ffi_rq_type(p, aux)

            spacing = ' '*(maxnamelen-len(p.ffi_field_name))
            eol = ')' if i == (len(self.ffi_params)-1) else ','
            _f('%s%s: %s%s%s', func_spacing, p.ffi_field_name, spacing,
                    ffi_rq_type, eol)

        _f("        -> %s;", self.ffi_cookie_type)


    def write_rs(self, regular, aux=False):
        checked = (self.void and not regular) \
                or ((not self.void) and regular)
        rs_func_name = self.rs_func_name(regular, aux)
        ffi_func_name = self.ffi_func_name(regular, aux)

        maxnamelen = len('c')
        for p in self.rs_params:
            maxnamelen = max(maxnamelen, len(p.rs_field_name))

        let_lines = []
        call_params = []

        _r.section(1)
        _r('')
        _write_doc_brief_desc(_r, self.request.doc)
        doc_params = False
        for f in self.rs_params:
            if len(self.request.doc.fields[f.field_name]):
                doc_params = True
                break
        if doc_params:
            _r('///')
            _r('/// parameters:')
            _r('///')
            _r('///   - __c__:')
            _r('///       The connection object to the server')
            for f in self.rs_params:
                _r('///')
                _r('///   - __%s__:', f.field_name)
                for fd in self.request.doc.fields[f.field_name]:
                    _r('///       %s', fd)
        fn_start = "pub fn %s%s(" % (rs_func_name, self.rs_template)
        func_spacing = ' ' * len(fn_start)
        eol = ',' if len(self.rs_params) else ')'
        spacing = ' ' * (maxnamelen-len('c'))
        _r("%sc%s: &'a base::Connection%s", fn_start, spacing, eol)

        for (i, p) in enumerate(self.rs_params):

            ffi_rq_type = self.ffi_rq_type(p, aux)
            rs_typestr = p.rs_field_type

            if self.rs_send_event and p.rs_field_name == "event":
                rs_typestr = "&base::Event<%s>" % p.rs_template_let
                let_lines.append("let event_ptr = " +
                    "std::mem::transmute(event.ptr);")
                call_params.append((p.ffi_index, "event_ptr"))
                pass
            elif p.rs_is_mask_slice:

                maskfield = p.rs_lenfield
                rs_typestr = '&[(%s, %s)]' % (maskfield.rs_field_type,
                    p.rs_field_type)

                let_lines.append('let mut %s_copy = %s.to_vec();' %
                        (p.rs_field_name, p.rs_field_name))
                let_lines.append(('let (%s_mask, %s_vec) = ' +
                        'base::pack_bitfield(&mut %s_copy);') %
                        (p.rs_field_name, p.rs_field_name, p.rs_field_name))
                let_lines.append("let %s_ptr = %s_vec.as_ptr();" %
                        (p.rs_field_name, p.rs_field_name))

                # adding mask field if not already done
                # (already done should not happen with masks)
                if not next((cp for cp in call_params
                            if cp[0] == maskfield.ffi_index), None):
                    call_params.append((maskfield.ffi_index, "%s_mask as %s" %
                        (p.rs_field_name, maskfield.ffi_field_type)))

                # adding actual field
                call_params.append((p.ffi_index, '%s_ptr as %s' %
                        (p.rs_field_name, ffi_rq_type)))

            elif p.rs_is_slice:

                if p.type.member.rs_type == 'c_char':
                    rs_typestr = '&str'
                    let_lines.append('let %s = %s.as_bytes();' %
                            (p.rs_field_name, p.rs_field_name))
                elif p.type.member.rs_type == 'c_void':
                    rs_typestr = '&[%s]' % p.rs_template_let
                else:
                    rs_typestr = '&[%s]' % rs_typestr

                if p.rs_lenfield:
                    lenfield = p.rs_lenfield
                    # adding len field if not already done
                    # (already done can happen with lists)
                    if not next((cp for cp in call_params
                            if cp[0] == lenfield.ffi_index), None):
                        let_lines.append('let %s_len = %s.len();' %
                                (p.rs_field_name, p.rs_field_name))
                        call_params.append((lenfield.ffi_index,
                                "%s_len as %s" %
                                (p.rs_field_name, lenfield.ffi_field_type)))

                let_lines.append('let %s_ptr = %s.as_ptr();' %
                        (p.rs_field_name, p.rs_field_name))
                # adding actual field
                call_params.append((p.ffi_index, '%s_ptr as %s' %
                        (p.rs_field_name, ffi_rq_type)))

            elif p.type.is_container and p.ffi_need_pointer:
                rs_typestr = 'std::option::Option<%s>' % rs_typestr
                let_lines.append('let %s_ptr = match %s {' % (p.rs_field_name,
                        p.rs_field_name))
                let_lines.append('    Some(p) => p.ptr as %s,' %
                        ffi_rq_type)
                let_lines.append('    None => std::ptr::null()')
                let_lines.append('};')
                call_params.append((p.ffi_index, '%s_ptr' % p.rs_field_name))

            elif p.type.is_container and not p.type.rs_is_pod:
                call_params.append((p.ffi_index, '*(%s.ptr)' %
                        p.rs_field_name))

            elif p.type.rs_is_pod:
                call_params.append((p.ffi_index, '%s.base' %
                        p.rs_field_name))
            else:
                call_params.append((p.ffi_index,
                        '%s as %s' % (p.rs_field_name, ffi_rq_type)))

            spacing = ' ' * (maxnamelen-len(p.rs_field_name))
            eol = ',' if i < (len(self.rs_params)-1) else ')'
            _r('%s%s%s: %s%s', func_spacing, p.rs_field_name,
                    spacing, rs_typestr, eol)

        _r("        -> %s<'a> {", self.rs_cookie_type)

        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                for l in let_lines:
                    _r(l)

                call_start = 'let cookie = %s(' % ffi_func_name
                eol = ',' if len(call_params) else ');'
                spacing = ' ' * len(call_start)
                _r('%sc.get_raw_conn()%s', call_start, eol)

                call_params.sort(key=lambda x: x[0])

                for (i, (ffi_ind, p)) in enumerate(call_params):
                    eol = ',' if i < (len(call_params)-1) else ');'
                    _r('%s%s%s  // %d', spacing, p, eol, ffi_ind)

                _r("%s {", self.rs_cookie_type)
                _r("    cookie:  cookie,")
                _r("    conn:    c,")
                _r("    checked: %s", 'true' if checked else 'false')
                _r("}")
            _r('}')
        _r('}')




def _opcode(nametup, opcode):
    # handle GLX with -1 opcode
    optype = 'u8' if int(opcode) >= 0 else 'i8'

    ffi_name = _ffi_const_name(nametup)
    _f.section(0)
    _f('')
    _f('pub const %s: %s = %s;', ffi_name, optype, opcode)

    rs_name = _rs_const_name(nametup)
    _r.section(1)
    _r('')
    _r('pub const %s: %s = %s;', rs_name, optype, opcode)



def _cookie(request):
    _f.section(0)
    _f('')
    _f('#[derive(Copy, Clone)]')
    _f('#[repr(C)]')
    _f('pub struct %s {', request.ffi_cookie_type)
    _f('    pub(crate) sequence: c_uint')
    _f('}')

    _r("impl base::CookieSeq for %s {", request.ffi_cookie_type)
    with _r.indent_block():
        _r("fn sequence(&self) -> c_uint { self.sequence }")
    _r("}")



    _r.section(1)
    _r("")
    _r("pub type %s<'a> = base::Cookie<'a, %s>;",
            request.rs_cookie_type, request.ffi_cookie_type)

    cookie = request.rs_cookie_type
    reply = request.rs_reply_type
    func = request.ffi_reply_fn

    _r.section(1)
    _r('')
    _r("impl<'a> %s<'a> {", cookie)
    with _r.indent_block():
        _r("pub fn get_reply(self) -> Result<%s, base::GenericError> {", reply)
        with _r.indent_block():
            _r('unsafe {')
            with _r.indent_block():
                _r("if self.checked {")
                _r("    let mut err: *mut xcb_generic_error_t = "
                        + "std::ptr::null_mut();")
                _r("    let reply = %s {", reply)
                _r("        ptr: %s (self.conn.get_raw_conn(), self.cookie, &mut err)", func)
                _r("    };")
                _r("    std::mem::forget(self);")
                _r("    if err.is_null() { Ok (reply) }")
                _r("    else { Err(base::GenericError { ptr: err }) }")
                _r("} else {")
                _r("    let res = %s {", reply)
                _r("        ptr: %s (self.conn.get_raw_conn(), self.cookie, ", func)
                _r("                std::ptr::null_mut())")
                _r("    };")
                _r("    std::mem::forget(self);")
                _r("    Ok(res)")
                _r("}")
            _r('}')
        _r('}')
    _r('}')




def _must_pack_event(event, nametup):
    # The generic event structure xcb_ge_event_t has the full_sequence field
    # at the 32byte boundary. That's why we've to inject this field into GE
    # events while generating the structure for them. Otherwise we would read
    # garbage (the internal full_sequence) when accessing normal event fields
    # there.
    must_pack = False
    if (hasattr(event, 'is_ge_event')
            and event.is_ge_event
            and event.name == nametup):
        event_size = 0
        for field in event.fields:
            if field.type.size != None and field.type.nmemb != None:
                event_size += field.type.size * field.type.nmemb
            if event_size == 32:
                full_sequence = Field(tcard32,
                        tcard32.name, 'full_sequence',
                        False, True, True)
                idx = event.fields.index(field)
                event.fields.insert(idx + 1, full_sequence)

                # If the event contains any 64-bit extended fields, they need
                # to remain aligned on a 64-bit boundary. Adding full_sequence
                # would normally break that; force the struct to be packed.
                must_pack = any(f.type.size == 8 and f.type.is_simple
                        for f in event.fields[(idx+1):])
                break

    return must_pack


def _handle_switch(typeobj, nametup):
    if typeobj.is_switch and typeobj.ffi_type not in finished_switch:
        finished_switch.append(typeobj.ffi_type)

        for bitcase in typeobj.bitcases:
            fname = _symbol(bitcase.field_name)
            bitcase.ffi_field_name = fname
            bitcase.rs_field_name = fname
            bitcase.nametup = (bitcase.field_type if bitcase.type.has_name
                    else nametup)
            _ffi_type_setup(bitcase.type, bitcase.nametup, ())
            _rs_type_setup(bitcase.type, bitcase.nametup, ())

        _set_type_lifetime(typeobj, True)

        _ffi_struct(typeobj)
        _rs_struct(typeobj)

        for bitcase in typeobj.bitcases:
            _ffi_accessors(bitcase.type, bitcase.nametup)
            # TODO: rs accessors

    if typeobj.is_container:
        for f in typeobj.fields:
            _prepare_doc(f.type)
            _handle_switch(f.type, f.field_type)


# codegen drivers

def rs_simple(simple, nametup):
    '''
    simple is SimpleType object
    nametup is a name tuple
    '''
    global current_handler
    current_handler = ('simple:  ', nametup)

    _prepare_doc(simple)

    simple.has_lifetime = False

    _ffi_type_setup(simple, nametup)
    _f.section(0)
    assert len(simple.name) == 1
    _f('')
    _write_doc_brief_desc(_f, simple.doc)
    _f('pub type %s = %s;', simple.ffi_type, simple.name[0])
    _ffi_iterator(simple, nametup)

    _rs_type_setup(simple, nametup)
    _r.section(0)
    _r('')
    _write_doc_brief_desc(_r, simple.doc)
    _r('pub type %s = %s;', simple.rs_type, simple.ffi_type)



def rs_enum(typeobj, nametup):
    '''
    typeobj is xcbgen.xtypes.Enum object
    nametup is a name tuple
    '''
    global current_handler
    current_handler = ('enum:    ', nametup)

    _prepare_doc(typeobj)

    ecg = EnumCodegen(nametup, typeobj.doc)

    val = -1
    for (enam, eval) in typeobj.values:
        val = int(eval) if eval != '' else val+1
        ecg.add_discriminant(enam, val)

    ecg.write_ffi()
    ecg.write_rs()




def rs_struct(struct, nametup):
    '''
    struct is Struct object
    nametup is a name tuple
    '''
    global current_handler
    current_handler = ('struct:  ', nametup)

    _prepare_doc(struct)

    struct.has_lifetime = True

    _ffi_type_setup(struct, nametup)
    _rs_type_setup(struct, nametup)
    _handle_switch(struct, nametup)

    _set_type_lifetime(struct, struct.has_lifetime)

    _ffi_struct(struct)
    _ffi_accessors(struct, nametup)
    _ffi_iterator(struct, nametup)

    _rs_struct(struct)
    _rs_accessors(struct)
    _rs_iterator(struct)



def rs_union(union, nametup):
    '''
    union is Union object
    nametup is a name tuple
    '''
    global current_handler
    current_handler = ('union:   ', nametup)

    _prepare_doc(union)

    union.has_lifetime = False

    _ffi_type_setup(union, nametup)
    _rs_type_setup(union, nametup)

    biggest = 1
    most_aligned = 1
    ptr_size = 8 if sys.maxsize > 2**32 else 4
    for field in union.fields:
        fs = ptr_size
        fa = ptr_size
        if field.type.size:
            fs = field.type.size
            fa = field.type.size
        if field.type.nmemb:
            fs = fa * field.type.nmemb
        biggest = max(biggest, fs)
        most_aligned = max(most_aligned, fa)

    assert biggest >= most_aligned

    num_aligned = int(biggest / most_aligned)
    if biggest % most_aligned:
        num_aligned += 1

    num_bytes = num_aligned * most_aligned
    union.union_num_bytes = num_bytes

    _f.section(0)
    _f('')
    _write_doc_brief_desc(_f, union.doc)
    _f('// union')
    _f('#[repr(C)]')
    _f('pub struct %s {', union.ffi_type)
    _f('    pub data: [u8; %d]', num_bytes)
    _f('}')

    _f('')
    _f('impl Copy for %s {}', union.ffi_type)
    _f('impl Clone for %s {', union.ffi_type)
    _f('    fn clone(&self) -> %s { *self }', union.ffi_type)
    _f('}')

    _ffi_iterator(union, nametup)

    _r.section(1)
    _r('')
    _r('pub type %s = %s;', union.rs_type, union.ffi_type)
    _rs_accessors(union)
    _rs_iterator(union)



def rs_request(request, nametup):
    '''
    request is Request object
    nametup is a name tuple
    '''
    global current_handler
    current_handler = ('request: ', nametup)

    _prepare_doc(request)

    request.has_lifetime = False

    _ffi_type_setup(request, nametup, ('request',))
    _rs_type_setup(request, nametup, ('request',))
    _handle_switch(request, nametup)

    _set_type_lifetime(request, request.has_lifetime)

    rcg = RequestCodegen(request)

    _opcode(nametup, request.opcode)
    _ffi_struct(request)

    if request.reply:
        _prepare_doc(request.reply)
        # enable getting the request from the reply
        request.reply.request = request
        request.reply.has_lifetime = False

        _cookie(request)

        _ffi_type_setup(request.reply, nametup, ('reply',))
        _rs_type_setup(request.reply, nametup, ('reply',))
        _handle_switch(request.reply, nametup)

        _set_type_lifetime(request.reply, request.reply.has_lifetime)

        _ffi_struct(request.reply)
        _ffi_accessors(request.reply, nametup + ('reply',))
        _ffi_reply(request)
        if _ffi_reply_has_fds(request.reply):
            _ffi_reply_fds(request, nametup)

        _rs_reply(request)
        _rs_reply_accessors(request.reply)

    # regular call 'request_name'
    rcg.write_ffi_rs(True, False)
    # unregular call 'request_name_checked' or 'request_name_unchecked'
    # depending on cookie type
    rcg.write_ffi_rs(False, False)

    if request.ffi_need_aux:
        rcg.write_ffi_rs(True, True)
        rcg.write_ffi_rs(False, True)


def rs_event(event, nametup):
    '''
    event is Event object
    nametup is a name tuple
    '''
    global current_handler
    current_handler = ('event:   ', nametup)

    must_pack = _must_pack_event(event, nametup)
    # _must_pack_event may insert fields,
    # therefore must be called before _prepare_doc
    _prepare_doc(event)

    if must_pack:
        print('event ', nametup, ' is packed')

    event.has_lifetime = False

    _ffi_type_setup(event, nametup, ('event',))
    _rs_type_setup(event, nametup, ('event',))

    _set_type_lifetime(event, event.has_lifetime)

    _opcode(nametup, event.opcodes[nametup])

    _r.section(1)
    _r('')
    _write_doc_brief_desc(_r, event.doc)
    _r('pub type %s = base::Event<%s>;', event.rs_type, event.ffi_type)

    if event.name == nametup:
        _ffi_struct(event, must_pack)

        accessor_fields = []
        for f in event.fields:
            if not f.visible: continue
            accessor_fields.append(f)
            if f.type.is_list or f.type.is_switch or f.type.is_bitcase:
                try:
                    accessor_fields.remove(f.type.expr.lenfield)
                except:
                    pass

        new_params = []
        if len(event.opcodes) > 1:
            new_params.append('response_type: u8')

        _r.section(1)
        _r('')
        _r('impl %s {', event.rs_type)
        with _r.indent_block():
            for f in accessor_fields:
                for fd in event.doc.fields[f.field_name]:
                    _r('/// %s', fd)
                _rs_accessor(event, f, True)

                rs_ftype = f.rs_field_type
                if f.has_subscript:
                    rs_ftype = "[%s; %d]" % (rs_ftype, f.type.nmemb)

                new_params.append("%s: %s" % (f.rs_field_name, rs_ftype))

            _r('/// Constructs a new %s', event.rs_type)
            if len(event.opcodes) > 1:
                _r('/// `response_type` must be set to one of:')
                for opname in event.opcodes:
                    _r('///     - `%s`', _rs_const_name(opname))
            else:
                _r('/// `response_type` will be set automatically to %s',
                        _rs_const_name(nametup))
            fn_start = "pub fn new("
            fn_space = ' ' * len(fn_start)
            p = new_params[0] if len(new_params) else ''
            eol = ',' if len(new_params)>1 else ')'
            _r('%s%s%s', fn_start, p, eol)
            for (i, p) in enumerate(new_params[1:]):
                eol = ',' if i != len(new_params)-2 else ')'
                _r("%s%s%s", fn_space, p, eol)

            _r('        -> %s {', event.rs_type)
            with _r.indent_block():
                _r('unsafe {')
                with _r.indent_block():
                    _r('let raw = libc::malloc(32 as usize) as *mut %s;',
                            event.ffi_type)
                    if len(event.opcodes) > 1:
                        # build list of possible opcodes
                        orlist = ' ||\n                    '.join(
                                [('response_type == %s' % _rs_const_name(opname))
                                    for opname in event.opcodes])
                        _r('assert!(%s,', orlist)
                        _r('        "wrong response_type supplied to %s::new");',
                                event.rs_type)
                        _r('(*raw).response_type = response_type;')
                    else:
                        _r('(*raw).response_type = %s;', _rs_const_name(nametup))
                    for f in event.fields:
                        if not f.visible: continue
                        if f.type.is_container and not f.type.is_union \
                                and not f.type.rs_is_pod:
                            _r('(*raw).%s = *%s.ptr;',
                                    f.ffi_field_name, f.rs_field_name)

                        elif f.type.rs_is_pod:
                            _r('(*raw).%s = %s.base;', f.ffi_field_name,
                                    f.rs_field_name)

                        else:
                            assignment = f.rs_field_name
                            if f.rs_field_type == 'bool':
                                assignment = ('if %s { 1 } else { 0 }' %
                                    f.rs_field_name)
                            _r('(*raw).%s = %s;', f.ffi_field_name, assignment)
                    _r('%s {', event.rs_type)
                    _r('    ptr: raw')
                    _r('}')
                _r('}')
            _r('}')
        _r('}')


    else:
        _f.section(0)
        _f('')
        _f('pub type %s = %s;', _ffi_type_name(nametup+('event',)),
                            _ffi_type_name(event.name+('event',)))



def rs_error(error, nametup):
    '''
    error is Error object
    nametup is a name tuple
    '''
    global current_handler
    current_handler = ('error:   ', nametup)

    _prepare_doc(error)

    _ffi_type_setup(error, nametup, ('error',))
    _opcode(nametup, error.opcodes[nametup])

    if error.name == nametup:
        _ffi_struct(error)
    else:
        _f.section(0)
        _f('')
        _f('pub type %s = %s;', _ffi_type_name(nametup+('error',)),
                            _ffi_type_name(error.name+('error',)))

    _rs_type_setup(error, nametup, ('error',))
    _r.section(0)
    _r('')
    _r('pub struct %s {', error.rs_type)
    _r('    pub base: base::Error<%s>', error.ffi_type)
    _r('}')


def usage(program):
    print('Usage: {} -o SRCDIR file.xml', program, file=sys.stderr)


if __name__ == '__main__':

    from optparse import OptionParser

    parser = OptionParser(usage="Usage: %prog -o SRCDIR file.xml")
    parser.add_option('-o', '--output', dest='srcdir', metavar='SRCDIR',
                help='specifies rust src dir where to generate files')

    (options, args) = parser.parse_args(sys.argv)

    if options.srcdir == None:
        parser.error('-o SRCDIR is mandatory')

    if not os.path.isdir(options.srcdir):
        parser.error('-o SRCDIR must be a directory')

    if len(args) < 2:
        parser.error('input XML file must be supplied')

    output = {  'open'      : rs_open,
                'close'     : rs_close,
                'simple'    : rs_simple,
                'enum'      : rs_enum,
                'struct'    : rs_struct,
                'union'     : rs_union,
                'request'   : rs_request,
                'event'     : rs_event,
                'error'     : rs_error }
    try:
        from xcbgen.state import Module
        from xcbgen.xtypes import *
    except ImportError:
        print('failed to load xcbgen', file=sys.stderr)
        raise

    # Parse the xml header
    module = Module(args[1], output)
    module.rs_srcdir = options.srcdir

    # Build type-registry and resolve type dependencies
    module.register()
    module.resolve()

    # Output the code
    try:
        module.generate()
    except:
        print('error occured in handler: ', current_handler, file=sys.stderr)
        raise