libepoxy/src/gen_dispatch.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Copyright © 2013 Intel Corporation
#
# 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 (including the next
# paragraph) 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.

import sys
import argparse
import xml.etree.ElementTree as ET
import re
import os

class GLProvider(object):
    def __init__(self, condition, condition_name, loader, name):
        # C code for determining if this function is available.
        # (e.g. epoxy_is_desktop_gl() && epoxy_gl_version() >= 20
        self.condition = condition

        # A string (possibly with spaces) describing the condition.
        self.condition_name = condition_name

        # The loader for getting the symbol -- either dlsym or
        # getprocaddress.  This is a python format string to generate
        # C code, given self.name.
        self.loader = loader

        # The name of the function to be loaded (possibly an
        # ARB/EXT/whatever-decorated variant).
        self.name = name

        # This is the C enum name we'll use for referring to this provider.
        self.enum = condition_name
        self.enum = self.enum.replace(' ', '_')
        self.enum = self.enum.replace('\\"', '')
        self.enum = self.enum.replace('.', '_')

class GLFunction(object):
    def __init__(self, ret_type, name):
        self.name = name
        self.ptr_type = 'PFN' + name.upper() + 'PROC'
        self.ret_type = ret_type
        self.providers = {}
        self.args = []

        # These are functions with hand-written wrapper code in
        # dispatch_common.c.  Their dispatch entries are replaced with
        # non-public symbols with a "_unwrapped" suffix.
        wrapped_functions = {
            'glBegin',
            'glEnd',
            'wglMakeCurrent',
            'wglMakeContextCurrentEXT',
            'wglMakeContextCurrentARB',
            'wglMakeAssociatedContextCurrentAMD',
        }

        if name in wrapped_functions:
            self.wrapped_name = name + '_unwrapped'
            self.public = ''
        else:
            self.wrapped_name = name
            self.public = 'PUBLIC '

        # This is the string of C code for passing through the
        # arguments to the function.
        self.args_list = ''

        # This is the string of C code for declaring the arguments
        # list.
        self.args_decl = 'void'

        # This is the string name of the function that this is an
        # alias of, or self.name.  This initially comes from the
        # registry, and may get updated if it turns out our alias is
        # itself an alias (for example glFramebufferTextureEXT ->
        # glFramebufferTextureARB -> glFramebufferTexture)
        self.alias_name = name

        # After alias resolution, this is the function that this is an
        # alias of.
        self.alias_func = None

        # For the root of an alias tree, this lists the functions that
        # are marked as aliases of it, so that it can write a resolver
        # for all of them.
        self.alias_exts = []

    def add_arg(self, type, name):
        # Reword glDepthRange() arguments to avoid clashing with the
        # "near" and "far" keywords on win32.
        if name == "near":
            name = "hither"
        elif name == "far":
            name = "yon"

        # Mac screwed up GLhandleARB and made it a void * instead of
        # uint32_t, despite it being specced as only necessarily 32
        # bits wide, causing portability problems all over.  There are
        # prototype conflicts between things like
        # glAttachShader(GLuint program, GLuint shader) and
        # glAttachObjectARB(GLhandleARB container, GLhandleARB obj),
        # even though they are marked as aliases in the XML (and being
        # aliases in Mesa).
        #
        # We retain those aliases.  In the x86_64 ABI, the first 6
        # args are stored in 64-bit registers, so the calls end up
        # being the same despite the different types.  We just need to
        # add a cast to uintptr_t to shut up the compiler.
        if type == 'GLhandleARB':
            assert(len(self.args) < 6)
            arg_list_name = '(uintptr_t)' + name
        else:
            arg_list_name = name

        self.args.append((type, name))
        if self.args_decl == 'void':
            self.args_list = arg_list_name
            self.args_decl = type + ' ' + name
        else:
            self.args_list += ', ' + arg_list_name
            self.args_decl += ', ' + type + ' ' + name

    def add_provider(self, condition, loader, condition_name):
        self.providers[condition_name] = GLProvider(condition, condition_name,
                                                    loader, self.name)

    def add_alias(self, ext):
        assert self.alias_func is None

        self.alias_exts.append(ext)
        ext.alias_func = self

class Generator(object):
    def __init__(self, target):
        self.target = target
        self.enums = {}
        self.functions = {}
        self.sorted_function = None
        self.max_enum_name_len = 1
        self.copyright_comment = None
        self.typedefs = ''
        self.out_file = None

        # GL versions named in the registry, which we should generate
        # #defines for.
        self.supported_versions = set()

        # Extensions named in the registry, which we should generate
        # #defines for.
        self.supported_extensions = set()

        # Dictionary mapping human-readable names of providers to a C
        # enum token that will be used to reference those names, to
        # reduce generated binary size.
        self.provider_enum = {}

        # Dictionary mapping human-readable names of providers to C
        # code to detect if it's present.
        self.provider_condition = {}

        # Dictionary mapping human-readable names of providers to
        # format strings for fetching the function pointer when
        # provided the name of the symbol to be requested.
        self.provider_loader = {}

    def all_text_until_element_name(self, element, element_name):
        text = ''

        if element.text is not None:
            text += element.text

        for child in element:
            if child.tag == element_name:
                break
            if child.text:
                text += child.text
            if child.tail:
                text += child.tail
        return text

    def out(self, text):
        self.out_file.write(text)

    def outln(self, text):
        self.out_file.write(text + '\n')

    def parse_typedefs(self, reg):
        for t in reg.findall('types/type'):
            if 'name' in t.attrib and t.attrib['name'] not in {'GLhandleARB'}:
                continue

            # The gles1/gles2-specific types are redundant
            # declarations, and the different types used for them (int
            # vs int32_t) caused problems on win32 builds.
            api = t.get('api')
            if api:
                continue

            if t.text is not None:
                self.typedefs += t.text

            for child in t:
                if child.text:
                    self.typedefs += child.text
                if child.tail:
                    self.typedefs += child.tail
            self.typedefs += '\n'

    def parse_enums(self, reg):
        for enum in reg.findall('enums/enum'):
            name = enum.get('name')

            # wgl.xml's 0xwhatever definitions end up colliding with
            # wingdi.h's decimal definitions of these.
            if ('WGL_SWAP_OVERLAY' in name or
                'WGL_SWAP_UNDERLAY' in name or
                'WGL_SWAP_MAIN_PLANE' in name):
                continue

            self.max_enum_name_len = max(self.max_enum_name_len, len(name))
            self.enums[name] = enum.get('value')

    def get_function_return_type(self, proto):
        # Everything up to the start of the name element is the return type.
        return self.all_text_until_element_name(proto, 'name').strip()

    def parse_function_definitions(self, reg):
        for command in reg.findall('commands/command'):
            proto = command.find('proto')
            name = proto.find('name').text
            ret_type = self.get_function_return_type(proto)

            func = GLFunction(ret_type, name)

            for arg in command.findall('param'):
                func.add_arg(self.all_text_until_element_name(arg, 'name').strip(),
                             arg.find('name').text)

            alias = command.find('alias')
            if alias is not None:
                # Note that some alias references appear before the
                # target command is defined (glAttachObjectARB() ->
                # glAttachShader(), for example).
                func.alias_name = alias.get('name')

            self.functions[name] = func

    def drop_weird_glx_functions(self):
        # Drop a few ancient SGIX GLX extensions that use types not defined
        # anywhere in Xlib.  In glxext.h, they're protected by #ifdefs for the
        # headers that defined them.
        weird_functions = [name for name, func in self.functions.items()
                           if 'VLServer' in func.args_decl
                           or 'DMparams' in func.args_decl]

        for name in weird_functions:
            del self.functions[name]

    def resolve_aliases(self):
        for func in self.functions.values():
            # Find the root of the alias tree, and add ourselves to it.
            if func.alias_name != func.name:
                alias_func = func
                while alias_func.alias_name != alias_func.name:
                    alias_func = self.functions[alias_func.alias_name]
                func.alias_name = alias_func.name
                func.alias_func = alias_func
                alias_func.alias_exts.append(func)

    def prepare_provider_enum(self):
        self.provider_enum = {}

        # We assume that for any given provider, all functions using
        # it will have the same loader.  This lets us generate a
        # general C function for detecting conditions and calling the
        # dlsym/getprocaddress, and have our many resolver stubs just
        # call it with a table of values.
        for func in self.functions.values():
            for provider in func.providers.values():
                if provider.condition_name in self.provider_enum:
                    assert(self.provider_condition[provider.condition_name] == provider.condition)
                    assert(self.provider_loader[provider.condition_name] == provider.loader)
                    continue

                self.provider_enum[provider.condition_name] = provider.enum;
                self.provider_condition[provider.condition_name] = provider.condition;
                self.provider_loader[provider.condition_name] = provider.loader;

    def sort_functions(self):
        self.sorted_functions = sorted(self.functions.values(), key=lambda func:func.name)

    def process_require_statements(self, feature, condition, loader, human_name):
        for command in feature.findall('require/command'):
            name = command.get('name')

            # wgl.xml describes 6 functions in WGL 1.0 that are in
            # gdi32.dll instead of opengl32.dll, and we would need to
            # change up our symbol loading to support that.  Just
            # don't wrap those functions.
            if self.target == 'wgl' and 'wgl' not in name:
                del self.functions[name]
                continue;

            func = self.functions[name]
            func.add_provider(condition, loader, human_name)

    def parse_function_providers(self, reg):
        for feature in reg.findall('feature'):
            api = feature.get('api') # string gl, gles1, gles2, glx
            m = re.match('([0-9])\.([0-9])', feature.get('number'))
            version = int(m.group(1)) * 10 + int(m.group(2))

            self.supported_versions.add(feature.get('name'))

            if api == 'gl':
                human_name = 'Desktop OpenGL {0}'.format(feature.get('number'))
                condition = 'epoxy_is_desktop_gl()'

                loader = 'epoxy_get_core_proc_address({0}, {1})'.format('{0}', version)
                if version >= 11:
                    condition += ' && epoxy_conservative_gl_version() >= {0}'.format(version)
            elif api == 'gles2':
                human_name = 'OpenGL ES {0}'.format(feature.get('number'))
                condition = '!epoxy_is_desktop_gl() && epoxy_gl_version() >= {0}'.format(version)

                if version <= 20:
                    loader = 'epoxy_gles2_dlsym({0})'
                else:
                    loader = 'epoxy_get_proc_address({0})'
            elif api == 'gles1':
                human_name = 'OpenGL ES 1.0'
                condition = '!epoxy_is_desktop_gl() && epoxy_gl_version() >= 10 && epoxy_gl_version() < 20'
                loader = 'epoxy_gles1_dlsym({0})'
            elif api == 'glx':
                human_name = 'GLX {0}'.format(version)
                # We could just always use GPA for loading everything
                # but glXGetProcAddress(), but dlsym() is a more
                # efficient lookup.
                if version > 13:
                    condition = 'epoxy_conservative_glx_version() >= {0}'.format(version)
                    loader = 'glXGetProcAddress((const GLubyte *){0})'
                else:
                    condition = 'true'
                    loader = 'epoxy_glx_dlsym({0})'
            elif api == 'egl':
                human_name = 'EGL {0}'.format(version)
                if version > 10:
                    condition = 'epoxy_conservative_egl_version() >= {0}'.format(version)
                else:
                    condition = 'true'
                # All EGL core entrypoints must be dlsym()ed out --
                # eglGetProcAdddress() will return NULL.
                loader = 'epoxy_egl_dlsym({0})'
            elif api == 'wgl':
                human_name = 'WGL {0}'.format(version)
                condition = 'true'
                loader = 'epoxy_gl_dlsym({0})'
            else:
                sys.exit('unknown API: "{0}"'.format(api))

            self.process_require_statements(feature, condition, loader, human_name)

        for extension in reg.findall('extensions/extension'):
            extname = extension.get('name')

            self.supported_extensions.add(extname)

            # 'supported' is a set of strings like gl, gles1, gles2,
            # or glx, which are separated by '|'
            apis = extension.get('supported').split('|')
            if 'glx' in apis:
                human_name = 'GLX extension \\"{0}\\"'.format(extname)
                condition = 'epoxy_conservative_has_glx_extension("{0}")'.format(extname)
                loader = 'glXGetProcAddress((const GLubyte *){0})'
                self.process_require_statements(extension, condition, loader, human_name)
            if 'egl' in apis:
                human_name = 'EGL extension \\"{0}\\"'.format(extname)
                condition = 'epoxy_conservative_has_egl_extension("{0}")'.format(extname)
                loader = 'eglGetProcAddress({0})'
                self.process_require_statements(extension, condition, loader, human_name)
            if 'wgl' in apis:
                human_name = 'WGL extension \\"{0}\\"'.format(extname)
                condition = 'epoxy_conservative_has_wgl_extension("{0}")'.format(extname)
                loader = 'wglGetProcAddress({0})'
                self.process_require_statements(extension, condition, loader, human_name)
            if {'gl', 'gles1', 'gles2'}.intersection(apis):
                human_name = 'GL extension \\"{0}\\"'.format(extname)
                condition = 'epoxy_conservative_has_gl_extension("{0}")'.format(extname)
                loader = 'epoxy_get_proc_address({0})'
                self.process_require_statements(extension, condition, loader, human_name)

    def fixup_bootstrap_function(self, name, loader):
        # We handle glGetString(), glGetIntegerv(), and
        # glXGetProcAddressARB() specially, because we need to use
        # them in the process of deciding on loaders for resolving,
        # and the naive code generation would result in their
        # resolvers calling their own resolvers.
        if name not in self.functions:
            return

        func = self.functions[name]
        func.providers = {}
        func.add_provider('true', loader, 'always present')

    def parse(self, file):
        reg = ET.parse(file)
        if reg.find('comment') != None:
            self.copyright_comment = reg.find('comment').text
        else:
            self.copyright_comment = ''
        self.parse_typedefs(reg)
        self.parse_enums(reg)
        self.parse_function_definitions(reg)
        self.parse_function_providers(reg)

    def write_copyright_comment_body(self):
        for line in self.copyright_comment.splitlines():
            if '-----' in line:
                break
            self.outln(' * ' + line)

    def write_enums(self):
        for name in sorted(self.supported_versions):
            self.outln('#define {0} 1'.format(name))
        self.outln('')

        for name in sorted(self.supported_extensions):
            self.outln('#define {0} 1'.format(name))
        self.outln('')

        # We want to sort by enum number (which puts a bunch of things
        # in a logical order), then by name after that, so we do those
        # sorts in reverse.  This is still way uglier than doing some
        # sort based on what version/extensions things are introduced
        # in, but we haven't paid any attention to those attributes
        # for enums yet.
        sorted_by_name = sorted(self.enums.keys())
        sorted_by_number = sorted(sorted_by_name, key=lambda name: self.enums[name])
        for name in sorted_by_number:
            self.outln('#define ' + name.ljust(self.max_enum_name_len + 3) + self.enums[name] + '')

    def write_function_ptr_typedefs(self):
        for func in self.sorted_functions:
            self.outln('typedef {0} (GLAPIENTRY *{1})({2});'.format(func.ret_type,
                                                                    func.ptr_type,
                                                                    func.args_decl))

    def write_header_header(self, file):
        self.out_file = open(file, 'w')

        self.outln('/* GL dispatch header.')
        self.outln(' * This is code-generated from the GL API XML files from Khronos.')
        self.write_copyright_comment_body()
        self.outln(' */')
        self.outln('')

        self.outln('#pragma once')

        self.outln('#include <inttypes.h>')
        self.outln('#include <stddef.h>')
        self.outln('')

    def write_header(self, file):
        self.write_header_header(file)

        if self.target != "gl":
            self.outln('#include "epoxy/gl.h"')
            if self.target == "egl":
                self.outln('#include "EGL/eglplatform.h"')
        else:
            # Add some ridiculous inttypes.h redefinitions that are
            # from khrplatform.h and not included in the XML.  We
            # don't directly include khrplatform.h because it's not
            # present on many systems, and coming up with #ifdefs to
            # decide when it's not present would be hard.
            self.outln('#define __khrplatform_h_ 1')
            self.outln('typedef int8_t khronos_int8_t;')
            self.outln('typedef int16_t khronos_int16_t;')
            self.outln('typedef int32_t khronos_int32_t;')
            self.outln('typedef int64_t khronos_int64_t;')
            self.outln('typedef uint8_t khronos_uint8_t;')
            self.outln('typedef uint16_t khronos_uint16_t;')
            self.outln('typedef uint32_t khronos_uint32_t;')
            self.outln('typedef uint64_t khronos_uint64_t;')
            self.outln('typedef float khronos_float_t;')
            self.outln('typedef intptr_t khronos_intptr_t;')
            self.outln('typedef ptrdiff_t khronos_ssize_t;')
            self.outln('typedef unsigned long khronos_usize_t;')
            self.outln('typedef uint64_t khronos_utime_nanoseconds_t;')
            self.outln('typedef int64_t khronos_stime_nanoseconds_t;')
            self.outln('#define KHRONOS_MAX_ENUM 0x7FFFFFFF')
            self.outln('typedef enum {')
            self.outln('    KHRONOS_FALSE = 0,')
            self.outln('    KHRONOS_TRUE  = 1,')
            self.outln('    KHRONOS_BOOLEAN_ENUM_FORCE_SIZE = KHRONOS_MAX_ENUM')
            self.outln('} khronos_boolean_enum_t;')
            self.outln('typedef uintptr_t khronos_uintptr_t;')

        if self.target == "glx":
            self.outln('#include <X11/Xlib.h>')
            self.outln('#include <X11/Xutil.h>')

        self.out(self.typedefs)
        self.outln('')
        self.write_enums()
        self.outln('')
        self.write_function_ptr_typedefs()

        for func in self.sorted_functions:
            self.outln('extern EPOXYAPIENTRY {0} (*epoxy_{1})({2});'.format(func.ret_type,
                                                                                     func.name,
                                                                                     func.args_decl))
            self.outln('')

        for func in self.sorted_functions:
            self.outln('#define {0} epoxy_{0}'.format(func.name))

    def write_function_ptr_resolver(self, func):
        self.outln('static {0}'.format(func.ptr_type))
        self.outln('epoxy_{0}_resolver(void)'.format(func.name))
        self.outln('{')

        providers = []
        # Make a local list of all the providers for this alias group
        for provider in func.providers.values():
            providers.append(provider)
        for alias_func in func.alias_exts:
            for provider in alias_func.providers.values():
                providers.append(provider)

        # Add some partial aliases of a few functions.  These are ones
        # that aren't quite aliases, because of some trivial behavior
        # difference (like whether to produce an error for a
        # non-Genned name), but where we'd like to fall back to the
        # similar function if the proper one isn't present.
        half_aliases = {
            'glBindVertexArray' : 'glBindVertexArrayAPPLE',
            'glBindVertexArrayAPPLE' : 'glBindVertexArray',
            'glBindFramebuffer' : 'glBindFramebufferEXT',
            'glBindFramebufferEXT' : 'glBindFramebuffer',
        }
        if func.name in half_aliases:
            alias_func = self.functions[half_aliases[func.name]]
            for provider in alias_func.providers.values():
                providers.append(provider)

        if len(providers) != 1:
            self.outln('    static const enum {0}_provider providers[] = {{'.format(self.target))
            for provider in providers:
                self.outln('        {0},'.format(provider.enum))
            self.outln('        {0}_provider_terminator'.format(self.target))
            self.outln('    };')

            self.outln('    static const uint16_t entrypoints[] = {')
            for provider in providers:
                self.outln('        {0} /* "{1}" */,'.format(self.entrypoint_string_offset[provider.name], provider.name))
            self.outln('    };')

            self.outln('    return {0}_provider_resolver(entrypoint_strings + {1} /* "{2}" */,'.format(self.target,
                                                                                                       self.entrypoint_string_offset[func.name],
                                                                                                       func.name))
            self.outln('                                providers, entrypoints);')
        else:
            assert(providers[0].name == func.name)
            self.outln('    return {0}_single_resolver({1}, {2} /* {3} */);'.format(self.target,
                                                                                    providers[0].enum,
                                                                                    self.entrypoint_string_offset[func.name],
                                                                                    func.name))
        self.outln('}')
        self.outln('')

    def write_dispatch_table_thunk(self, func):
        # Writes out the thunk that fetches the (win32) dispatch table
        # and calls through its entrypoint.

        dispatch_table_entry = 'dispatch_table->p{0}'.format(func.alias_name)

        self.outln('static __stdcall {0}'.format(func.ret_type))
        self.outln('epoxy_{0}_dispatch_table_thunk({1})'.format(func.wrapped_name, func.args_decl))
        self.outln('{')
        self.outln('    struct dispatch_table *dispatch_table = get_dispatch_table();')
        self.outln('')
        if func.ret_type == 'void':
            self.outln('    {0}({1});'.format(dispatch_table_entry, func.args_list))
        else:
            self.outln('    return {0}({1});'.format(dispatch_table_entry, func.args_list))
        self.outln('}')
        self.outln('')

    def write_dispatch_table_rewrite_stub(self, func):
        # Writes out the initial dispatch table function pointer value
        # that that resolves, writes the resolved value into the
        # dispatch table, and calls down to it.

        dispatch_table_entry = 'dispatch_table->p{0}'.format(func.name)

        self.outln('static GLAPIENTRY {0}'.format(func.ret_type))
        self.outln('epoxy_{0}_rewrite_stub({1})'.format(func.name, func.args_decl))
        self.outln('{')
        self.outln('    struct dispatch_table *dispatch_table = get_dispatch_table();')
        self.outln('')
        self.outln('    dispatch_table->p{0} = epoxy_{0}_resolver();'.format(func.name))
        self.outln('')

        if func.ret_type == 'void':
            self.outln('    dispatch_table->p{0}({1});'.format(func.name, func.args_list))
        else:
            self.outln('    return dispatch_table->p{0}({1});'.format(func.name, func.args_list))
        self.outln('}')
        self.outln('')

    def write_linux_function_pointer(self, func):
        # Writes out the function for resolving and updating the
        # global function pointer, plus the actual global function
        # pointer initializer.

        self.outln('static {0}'.format(func.ret_type))
        self.outln('epoxy_{0}_rewrite_ptr({1})'.format(func.wrapped_name,
                                                       func.args_decl))
        self.outln('{')
        self.outln('    epoxy_{0} = (void *)epoxy_{1}_resolver();'.format(func.wrapped_name,
                                                                          func.alias_name))

        if func.ret_type == 'void':
            self.outln('    epoxy_{0}({1});'.format(func.wrapped_name,
                                                    func.args_list))
        else:
            self.outln('    return epoxy_{0}({1});'.format(func.wrapped_name,
                                                           func.args_list))

        self.outln('}')

        self.outln('{0}{1} epoxy_{2} = epoxy_{2}_rewrite_ptr;'.format(func.public,
                                                                      func.ptr_type,
                                                                      func.wrapped_name))
        self.outln('')

    def write_win32_function_pointer(self, func):
        self.outln('{0}{1} epoxy_{2} = epoxy_{2}_dispatch_table_thunk;'.format(func.public,
                                                                               func.ptr_type,
                                                                               func.wrapped_name))
        self.outln('')

    def write_provider_enums(self):
        # Writes the enum declaration for the list of providers
        # supported by gl_provider_resolver()

        self.outln('enum {0}_provider {{'.format(self.target))

        sorted_providers = sorted(self.provider_enum.keys())

        # We always put a 0 enum first so that we can have a
        # terminator in our arrays
        self.outln('    {0}_provider_terminator = 0,'.format(self.target))

        for human_name in sorted_providers:
            enum = self.provider_enum[human_name]
            self.outln('    {0},'.format(enum))
        self.outln('};')
        self.outln('')

    def write_provider_enum_strings(self):
        # Writes the mapping from enums to the strings describing them
        # for epoxy_print_failure_reasons().

        self.outln('static const char *enum_strings[] = {')

        sorted_providers = sorted(self.provider_enum.keys())

        for human_name in sorted_providers:
            enum = self.provider_enum[human_name]
            self.outln('    [{0}] = "{1}",'.format(enum, human_name))
        self.outln('};')
        self.outln('')

    def write_entrypoint_strings(self):
        self.entrypoint_string_offset = {}

        self.outln('static const char entrypoint_strings[] = ')
        offset = 0
        for func in self.sorted_functions:
            if func.name not in self.entrypoint_string_offset:
                self.entrypoint_string_offset[func.name] = offset
                offset += len(func.name) + 1
                self.outln('   "{0}\\0"'.format(func.name))
        self.outln('    ;')
        # We're using uint16_t for the offsets.
        assert(offset < 65536)
        self.outln('')

    def write_provider_resolver(self):
        self.outln('static void *{0}_provider_resolver(const char *name,'.format(self.target))
        self.outln('                                   const enum {0}_provider *providers,'.format(self.target))
        self.outln('                                   const uint16_t *entrypoints)')
        self.outln('{')
        self.outln('    int i;')

        self.outln('    for (i = 0; providers[i] != {0}_provider_terminator; i++) {{'.format(self.target))
        self.outln('        switch (providers[i]) {')

        for human_name in sorted(self.provider_enum.keys()):
            enum = self.provider_enum[human_name]
            self.outln('        case {0}:'.format(enum))
            self.outln('            if ({0})'.format(self.provider_condition[human_name]))
            self.outln('                return {0};'.format(self.provider_loader[human_name]).format("entrypoint_strings + entrypoints[i]"))
            self.outln('            break;')

        self.outln('        case {0}_provider_terminator:'.format(self.target))
        self.outln('            abort(); /* Not reached */')
        self.outln('        }')
        self.outln('    }')
        self.outln('')

        # If the function isn't provided by any known extension, print
        # something useful for the poor application developer before
        # aborting.  (In non-epoxy GL usage, the app developer would
        # call into some blank stub function and segfault).
        self.outln('    epoxy_print_failure_reasons(name, enum_strings, (const int *)providers);')
        self.outln('    abort();')

        self.outln('}')
        self.outln('')

        single_resolver_proto = '{0}_single_resolver(enum {0}_provider provider, uint16_t entrypoint_offset)'.format(self.target)
        self.outln('static void *')
        self.outln('{0} __attribute__((noinline));'.format(single_resolver_proto))
        self.outln('')
        self.outln('static void *')
        self.outln('{0}'.format(single_resolver_proto))
        self.outln('{')
        self.outln('    enum {0}_provider providers[] = {{'.format(self.target))
        self.outln('        provider,')
        self.outln('        {0}_provider_terminator'.format(self.target))
        self.outln('    };')
        self.outln('    return {0}_provider_resolver(entrypoint_strings + entrypoint_offset,'.format(self.target))
        self.outln('                                providers, &entrypoint_offset);')
        self.outln('}')
        self.outln('')

    def write_source(self, file):
        self.out_file = open(file, 'w')

        self.outln('/* GL dispatch code.')
        self.outln(' * This is code-generated from the GL API XML files from Khronos.')
        self.write_copyright_comment_body()
        self.outln(' */')
        self.outln('')
        self.outln('#include <stdlib.h>')
        self.outln('#include <stdio.h>')
        self.outln('')
        self.outln('#include "dispatch_common.h"')
        self.outln('#include "epoxy/{0}.h"'.format(self.target))
        self.outln('')

        self.outln('struct dispatch_table {')
        for func in self.sorted_functions:
            # Aliases don't get their own slot, since they use a shared resolver.
            if func.alias_name == func.name:
                self.outln('    {0} p{1};'.format(func.ptr_type, func.name))
        self.outln('};')
        self.outln('')

        # Early declaration, so we can declare the real thing at the
        # bottom. (I want the function_ptr_resolver as the first
        # per-GL-call code, since it's the most interesting to see
        # when you search for the implementation of a call)
        self.outln('#if USING_DISPATCH_TABLE')
        self.outln('static inline struct dispatch_table *')
        self.outln('get_dispatch_table(void);')
        self.outln('')
        self.outln('#endif')

        self.write_provider_enums()
        self.write_provider_enum_strings()
        self.write_entrypoint_strings()
        self.write_provider_resolver()

        for func in self.sorted_functions:
            if not func.alias_func:
                self.write_function_ptr_resolver(func)

        self.outln('#if USING_DISPATCH_TABLE')

        for func in self.sorted_functions:
            if not func.alias_func:
                self.write_dispatch_table_rewrite_stub(func)

        for func in self.sorted_functions:
            self.write_dispatch_table_thunk(func)

        self.outln('static struct dispatch_table resolver_table = {')
        for func in self.sorted_functions:
            # Aliases don't get their own slot, since they use a shared resolver.
            if func.alias_name == func.name:
                self.outln('    .p{0} = epoxy_{0}_rewrite_stub,'.format(func.name))
        self.outln('};')
        self.outln('')

        self.outln('uint32_t {0}_tls_index;'.format(self.target))
        self.outln('uint32_t {0}_tls_size = sizeof(struct dispatch_table);'.format(self.target))
        self.outln('')

        self.outln('static inline struct dispatch_table *')
        self.outln('get_dispatch_table(void)')
        self.outln('{')
        self.outln('	return TlsGetValue({0}_tls_index);'.format(self.target))
        self.outln('}')
        self.outln('')

        self.outln('void')
        self.outln('{0}_init_dispatch_table(void)'.format(self.target))
        self.outln('{')
        self.outln('    struct dispatch_table *dispatch_table = get_dispatch_table();')
        self.outln('    memcpy(dispatch_table, &resolver_table, sizeof(resolver_table));')
        self.outln('}')
        self.outln('')

        for func in self.sorted_functions:
            self.write_win32_function_pointer(func)

        self.outln('#else /* !USING_DISPATCH_TABLE */')

        for func in self.sorted_functions:
            self.write_linux_function_pointer(func)

        self.outln('#endif /* !USING_DISPATCH_TABLE */')

argparser = argparse.ArgumentParser(description='Generate GL dispatch wrappers.')
argparser.add_argument('files', metavar='file.xml', nargs='+', help='GL API XML files to be parsed')
argparser.add_argument('--dir', metavar='dir', required=True, help='Destination directory')
args = argparser.parse_args()

srcdir = args.dir + '/src/'
incdir = args.dir + '/include/epoxy/'

for file in args.files:
    name = os.path.basename(file).split('.xml')[0]
    generator = Generator(name)
    generator.parse(file)
    generator.drop_weird_glx_functions()
    generator.sort_functions()
    generator.resolve_aliases()
    generator.fixup_bootstrap_function('glGetString',
                                       'epoxy_get_bootstrap_proc_address({0})')
    generator.fixup_bootstrap_function('glGetIntegerv',
                                       'epoxy_get_bootstrap_proc_address({0})')

    # While this is technically exposed as a GLX extension, it's
    # required to be present as a public symbol by the Linux OpenGL
    # ABI.
    generator.fixup_bootstrap_function('glXGetProcAddress',
                                       'epoxy_glx_dlsym({0})')

    generator.prepare_provider_enum()

    generator.write_header(incdir + name + '_generated.h')
    generator.write_source(srcdir + name + '_generated_dispatch.c')