1/*
2 * Mesa 3-D graphics library
3 * Version:  7.6
4 *
5 * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
6 * Copyright (C) 2009  VMware, Inc.  All Rights Reserved.
7 *
8 * Permission is hereby granted, free of charge, to any person obtaining a
9 * copy of this software and associated documentation files (the "Software"),
10 * to deal in the Software without restriction, including without limitation
11 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
12 * and/or sell copies of the Software, and to permit persons to whom the
13 * Software is furnished to do so, subject to the following conditions:
14 *
15 * The above copyright notice and this permission notice shall be included
16 * in all copies or substantial portions of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
21 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
22 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
23 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24 */
25
26
27/**
28 * \file
29 * \brief Extension handling
30 */
31
32
33#include "glheader.h"
34#include "imports.h"
35#include "context.h"
36#include "extensions.h"
37#include "mfeatures.h"
38#include "mtypes.h"
39
40#define ALIGN(value, alignment)  (((value) + alignment - 1) & ~(alignment - 1))
41
42enum {
43   DISABLE = 0,
44   GLL = 1 << API_OPENGL,       /* GL Legacy / Compatibility */
45   GLC = 1 << API_OPENGL_CORE,  /* GL Core */
46   GL  = (1 << API_OPENGL) | (1 << API_OPENGL_CORE),
47   ES1 = 1 << API_OPENGLES,
48   ES2 = 1 << API_OPENGLES2,
49};
50
51/**
52 * \brief An element of the \c extension_table.
53 */
54struct extension {
55   /** Name of extension, such as "GL_ARB_depth_clamp". */
56   const char *name;
57
58   /** Offset (in bytes) of the corresponding member in struct gl_extensions. */
59   size_t offset;
60
61   /** Set of API's in which the extension exists, as a bitset. */
62   uint8_t api_set;
63
64   /** Year the extension was proposed or approved.  Used to sort the
65    * extension string chronologically. */
66   uint16_t year;
67};
68
69
70/**
71 * Given a member \c x of struct gl_extensions, return offset of
72 * \c x in bytes.
73 */
74#define o(x) offsetof(struct gl_extensions, x)
75
76
77/**
78 * \brief Table of supported OpenGL extensions for all API's.
79 */
80static const struct extension extension_table[] = {
81   /* ARB Extensions */
82   { "GL_ARB_ES2_compatibility",                   o(ARB_ES2_compatibility),                   GL,             2009 },
83   { "GL_ARB_base_instance",                       o(ARB_base_instance),                       GL,             2011 },
84   { "GL_ARB_blend_func_extended",                 o(ARB_blend_func_extended),                 GL,             2009 },
85   { "GL_ARB_color_buffer_float",                  o(ARB_color_buffer_float),                  GL,             2004 },
86   { "GL_ARB_copy_buffer",                         o(ARB_copy_buffer),                         GL,             2008 },
87   { "GL_ARB_conservative_depth",                  o(ARB_conservative_depth),                  GL,             2011 },
88   { "GL_ARB_debug_output",                        o(dummy_true),                              GL,             2009 },
89   { "GL_ARB_depth_buffer_float",                  o(ARB_depth_buffer_float),                  GL,             2008 },
90   { "GL_ARB_depth_clamp",                         o(ARB_depth_clamp),                         GL,             2003 },
91   { "GL_ARB_depth_texture",                       o(ARB_depth_texture),                       GLL,            2001 },
92   { "GL_ARB_draw_buffers",                        o(dummy_true),                              GL,             2002 },
93   { "GL_ARB_draw_buffers_blend",                  o(ARB_draw_buffers_blend),                  GL,             2009 },
94   { "GL_ARB_draw_elements_base_vertex",           o(ARB_draw_elements_base_vertex),           GL,             2009 },
95   { "GL_ARB_draw_instanced",                      o(ARB_draw_instanced),                      GL,             2008 },
96   { "GL_ARB_explicit_attrib_location",            o(ARB_explicit_attrib_location),            GL,             2009 },
97   { "GL_ARB_fragment_coord_conventions",          o(ARB_fragment_coord_conventions),          GL,             2009 },
98   { "GL_ARB_fragment_program",                    o(ARB_fragment_program),                    GLL,            2002 },
99   { "GL_ARB_fragment_program_shadow",             o(ARB_fragment_program_shadow),             GLL,            2003 },
100   { "GL_ARB_fragment_shader",                     o(ARB_fragment_shader),                     GL,             2002 },
101   { "GL_ARB_framebuffer_object",                  o(ARB_framebuffer_object),                  GL,             2005 },
102   { "GL_ARB_framebuffer_sRGB",                    o(EXT_framebuffer_sRGB),                    GL,             1998 },
103   { "GL_ARB_half_float_pixel",                    o(ARB_half_float_pixel),                    GL,             2003 },
104   { "GL_ARB_half_float_vertex",                   o(ARB_half_float_vertex),                   GL,             2008 },
105   { "GL_ARB_instanced_arrays",                    o(ARB_instanced_arrays),                    GL,             2008 },
106   { "GL_ARB_invalidate_subdata",                  o(dummy_true),                              GL,             2012 },
107   { "GL_ARB_map_buffer_range",                    o(ARB_map_buffer_range),                    GL,             2008 },
108   { "GL_ARB_multisample",                         o(dummy_true),                              GLL,            1994 },
109   { "GL_ARB_multitexture",                        o(dummy_true),                              GLL,            1998 },
110   { "GL_ARB_occlusion_query2",                    o(ARB_occlusion_query2),                    GL,             2003 },
111   { "GL_ARB_occlusion_query",                     o(ARB_occlusion_query),                     GLL,            2001 },
112   { "GL_ARB_pixel_buffer_object",                 o(EXT_pixel_buffer_object),                 GL,             2004 },
113   { "GL_ARB_point_parameters",                    o(EXT_point_parameters),                    GLL,            1997 },
114   { "GL_ARB_point_sprite",                        o(ARB_point_sprite),                        GL,             2003 },
115   { "GL_ARB_provoking_vertex",                    o(EXT_provoking_vertex),                    GL,             2009 },
116   { "GL_ARB_robustness",                          o(dummy_true),                              GL,             2010 },
117   { "GL_ARB_sampler_objects",                     o(dummy_true),                              GL,             2009 },
118   { "GL_ARB_seamless_cube_map",                   o(ARB_seamless_cube_map),                   GL,             2009 },
119   { "GL_ARB_shader_bit_encoding",                 o(ARB_shader_bit_encoding),                 GL,             2010 },
120   { "GL_ARB_shader_objects",                      o(ARB_shader_objects),                      GL,             2002 },
121   { "GL_ARB_shader_stencil_export",               o(ARB_shader_stencil_export),               GL,             2009 },
122   { "GL_ARB_shader_texture_lod",                  o(ARB_shader_texture_lod),                  GL,             2009 },
123   { "GL_ARB_shading_language_100",                o(ARB_shading_language_100),                GLL,            2003 },
124   { "GL_ARB_shadow",                              o(ARB_shadow),                              GLL,            2001 },
125   { "GL_ARB_sync",                                o(ARB_sync),                                GL,             2003 },
126   { "GL_ARB_texture_border_clamp",                o(ARB_texture_border_clamp),                GLL,            2000 },
127   { "GL_ARB_texture_buffer_object",               o(ARB_texture_buffer_object),               GL,             2008 },
128   { "GL_ARB_texture_compression",                 o(dummy_true),                              GLL,            2000 },
129   { "GL_ARB_texture_compression_rgtc",            o(ARB_texture_compression_rgtc),            GL,             2004 },
130   { "GL_ARB_texture_cube_map",                    o(ARB_texture_cube_map),                    GLL,            1999 },
131   { "GL_ARB_texture_env_add",                     o(dummy_true),                              GLL,            1999 },
132   { "GL_ARB_texture_env_combine",                 o(ARB_texture_env_combine),                 GLL,            2001 },
133   { "GL_ARB_texture_env_crossbar",                o(ARB_texture_env_crossbar),                GLL,            2001 },
134   { "GL_ARB_texture_env_dot3",                    o(ARB_texture_env_dot3),                    GLL,            2001 },
135   { "GL_ARB_texture_float",                       o(ARB_texture_float),                       GL,             2004 },
136   { "GL_ARB_texture_mirrored_repeat",             o(dummy_true),                              GLL,            2001 },
137   { "GL_ARB_texture_multisample",                 o(ARB_texture_multisample),                 GL,             2009 },
138   { "GL_ARB_texture_non_power_of_two",            o(ARB_texture_non_power_of_two),            GL,             2003 },
139   { "GL_ARB_texture_rectangle",                   o(NV_texture_rectangle),                    GL,             2004 },
140   { "GL_ARB_texture_rgb10_a2ui",                  o(ARB_texture_rgb10_a2ui),                  GL,             2009 },
141   { "GL_ARB_texture_rg",                          o(ARB_texture_rg),                          GL,             2008 },
142   { "GL_ARB_texture_storage",                     o(ARB_texture_storage),                     GL,             2011 },
143   { "GL_ARB_texture_swizzle",                     o(EXT_texture_swizzle),                     GL,             2008 },
144   { "GL_ARB_timer_query",                         o(ARB_timer_query),                         GL,             2010 },
145   { "GL_ARB_transform_feedback2",                 o(ARB_transform_feedback2),                 GL,             2010 },
146   { "GL_ARB_transform_feedback3",                 o(ARB_transform_feedback3),                 GL,             2010 },
147   { "GL_ARB_transform_feedback_instanced",        o(ARB_transform_feedback_instanced),        GL,             2011 },
148   { "GL_ARB_transpose_matrix",                    o(ARB_transpose_matrix),                    GLL,            1999 },
149   { "GL_ARB_uniform_buffer_object",               o(ARB_uniform_buffer_object),               GL,             2009 },
150   { "GL_ARB_vertex_array_bgra",                   o(EXT_vertex_array_bgra),                   GL,             2008 },
151   { "GL_ARB_vertex_array_object",                 o(dummy_true),                              GL,             2006 },
152   { "GL_ARB_vertex_buffer_object",                o(dummy_true),                              GLL,            2003 },
153   { "GL_ARB_vertex_program",                      o(ARB_vertex_program),                      GLL,            2002 },
154   { "GL_ARB_vertex_shader",                       o(ARB_vertex_shader),                       GL,             2002 },
155   { "GL_ARB_vertex_type_2_10_10_10_rev",          o(ARB_vertex_type_2_10_10_10_rev),          GL,             2009 },
156   { "GL_ARB_window_pos",                          o(ARB_window_pos),                          GLL,            2001 },
157   /* EXT extensions */
158   { "GL_EXT_abgr",                                o(dummy_true),                              GL,             1995 },
159   { "GL_EXT_bgra",                                o(dummy_true),                              GLL,            1995 },
160   { "GL_EXT_blend_color",                         o(EXT_blend_color),                         GLL,            1995 },
161   { "GL_EXT_blend_equation_separate",             o(EXT_blend_equation_separate),             GL,             2003 },
162   { "GL_EXT_blend_func_separate",                 o(EXT_blend_func_separate),                 GLL,            1999 },
163   { "GL_EXT_blend_minmax",                        o(EXT_blend_minmax),                        GLL | ES1 | ES2, 1995 },
164   { "GL_EXT_blend_subtract",                      o(dummy_true),                              GLL,            1995 },
165   { "GL_EXT_clip_volume_hint",                    o(EXT_clip_volume_hint),                    GL,             1996 },
166   { "GL_EXT_compiled_vertex_array",               o(EXT_compiled_vertex_array),               GLL,            1996 },
167   { "GL_EXT_copy_texture",                        o(dummy_true),                              GLL,            1995 },
168   { "GL_EXT_depth_bounds_test",                   o(EXT_depth_bounds_test),                   GL,             2002 },
169   { "GL_EXT_draw_buffers2",                       o(EXT_draw_buffers2),                       GL,             2006 },
170   { "GL_EXT_draw_instanced",                      o(ARB_draw_instanced),                      GL,             2006 },
171   { "GL_EXT_draw_range_elements",                 o(EXT_draw_range_elements),                 GLL,            1997 },
172   { "GL_EXT_fog_coord",                           o(EXT_fog_coord),                           GLL,            1999 },
173   { "GL_EXT_framebuffer_blit",                    o(EXT_framebuffer_blit),                    GL,             2005 },
174   { "GL_EXT_framebuffer_multisample",             o(EXT_framebuffer_multisample),             GL,             2005 },
175   { "GL_EXT_framebuffer_object",                  o(EXT_framebuffer_object),                  GL,             2000 },
176   { "GL_EXT_framebuffer_sRGB",                    o(EXT_framebuffer_sRGB),                    GL,             1998 },
177   { "GL_EXT_gpu_program_parameters",              o(EXT_gpu_program_parameters),              GLL,            2006 },
178   { "GL_EXT_gpu_shader4",                         o(EXT_gpu_shader4),                         GL,             2006 },
179   { "GL_EXT_multi_draw_arrays",                   o(dummy_true),                              GLL | ES1 | ES2, 1999 },
180   { "GL_EXT_packed_depth_stencil",                o(EXT_packed_depth_stencil),                GL,             2005 },
181   { "GL_EXT_packed_float",                        o(EXT_packed_float),                        GL,             2004 },
182   { "GL_EXT_packed_pixels",                       o(EXT_packed_pixels),                       GLL,            1997 },
183   { "GL_EXT_pixel_buffer_object",                 o(EXT_pixel_buffer_object),                 GL,             2004 },
184   { "GL_EXT_point_parameters",                    o(EXT_point_parameters),                    GLL,            1997 },
185   { "GL_EXT_polygon_offset",                      o(dummy_true),                              GLL,            1995 },
186   { "GL_EXT_provoking_vertex",                    o(EXT_provoking_vertex),                    GL,             2009 },
187   { "GL_EXT_rescale_normal",                      o(EXT_rescale_normal),                      GLL,            1997 },
188   { "GL_EXT_secondary_color",                     o(EXT_secondary_color),                     GLL,            1999 },
189   { "GL_EXT_separate_shader_objects",             o(EXT_separate_shader_objects),             GLL,            2008 },
190   { "GL_EXT_separate_specular_color",             o(EXT_separate_specular_color),             GLL,            1997 },
191   { "GL_EXT_shadow_funcs",                        o(EXT_shadow_funcs),                        GLL,            2002 },
192   { "GL_EXT_stencil_two_side",                    o(EXT_stencil_two_side),                    GLL,            2001 },
193   { "GL_EXT_stencil_wrap",                        o(dummy_true),                              GLL,            2002 },
194   { "GL_EXT_subtexture",                          o(dummy_true),                              GLL,            1995 },
195   { "GL_EXT_texture3D",                           o(EXT_texture3D),                           GLL,            1996 },
196   { "GL_EXT_texture_array",                       o(EXT_texture_array),                       GL,             2006 },
197   { "GL_EXT_texture_compression_dxt1",            o(EXT_texture_compression_s3tc),            GL | ES1 | ES2, 2004 },
198   { "GL_EXT_texture_compression_latc",            o(EXT_texture_compression_latc),            GL,             2006 },
199   { "GL_EXT_texture_compression_rgtc",            o(ARB_texture_compression_rgtc),            GL,             2004 },
200   { "GL_EXT_texture_compression_s3tc",            o(EXT_texture_compression_s3tc),            GL,             2000 },
201   { "GL_EXT_texture_cube_map",                    o(ARB_texture_cube_map),                    GLL,            2001 },
202   { "GL_EXT_texture_edge_clamp",                  o(dummy_true),                              GLL,            1997 },
203   { "GL_EXT_texture_env_add",                     o(dummy_true),                              GLL,            1999 },
204   { "GL_EXT_texture_env_combine",                 o(dummy_true),                              GLL,            2000 },
205   { "GL_EXT_texture_env_dot3",                    o(EXT_texture_env_dot3),                    GLL,            2000 },
206   { "GL_EXT_texture_filter_anisotropic",          o(EXT_texture_filter_anisotropic),          GL | ES1 | ES2, 1999 },
207   { "GL_EXT_texture_format_BGRA8888",             o(dummy_true),                                   ES1 | ES2, 2005 },
208   { "GL_EXT_texture_rg",                          o(ARB_texture_rg),                                     ES2, 2011 },
209   { "GL_EXT_read_format_bgra",                    o(dummy_true),                                   ES1 | ES2, 2009 },
210   { "GL_EXT_texture_integer",                     o(EXT_texture_integer),                     GL,             2006 },
211   { "GL_EXT_texture_lod_bias",                    o(dummy_true),                              GLL | ES1,      1999 },
212   { "GL_EXT_texture_mirror_clamp",                o(EXT_texture_mirror_clamp),                GL,             2004 },
213   { "GL_EXT_texture_object",                      o(dummy_true),                              GLL,            1995 },
214   { "GL_EXT_texture",                             o(dummy_true),                              GLL,            1996 },
215   { "GL_EXT_texture_rectangle",                   o(NV_texture_rectangle),                    GLL,            2004 },
216   { "GL_EXT_texture_shared_exponent",             o(EXT_texture_shared_exponent),             GL,             2004 },
217   { "GL_EXT_texture_snorm",                       o(EXT_texture_snorm),                       GL,             2009 },
218   { "GL_EXT_texture_sRGB",                        o(EXT_texture_sRGB),                        GL,             2004 },
219   { "GL_EXT_texture_sRGB_decode",                 o(EXT_texture_sRGB_decode),                        GL,      2006 },
220   { "GL_EXT_texture_swizzle",                     o(EXT_texture_swizzle),                     GL,             2008 },
221   { "GL_EXT_texture_type_2_10_10_10_REV",         o(dummy_true),                                         ES2, 2008 },
222   { "GL_EXT_timer_query",                         o(EXT_timer_query),                         GL,             2006 },
223   { "GL_EXT_transform_feedback",                  o(EXT_transform_feedback),                  GL,             2011 },
224   { "GL_EXT_unpack_subimage",                     o(dummy_true),                                         ES2, 2011 },
225   { "GL_EXT_vertex_array_bgra",                   o(EXT_vertex_array_bgra),                   GL,             2008 },
226   { "GL_EXT_vertex_array",                        o(dummy_true),                              GLL,            1995 },
227
228   /* OES extensions */
229   { "GL_OES_blend_equation_separate",             o(EXT_blend_equation_separate),                  ES1,       2009 },
230   { "GL_OES_blend_func_separate",                 o(EXT_blend_func_separate),                      ES1,       2009 },
231   { "GL_OES_blend_subtract",                      o(dummy_true),                                   ES1,       2009 },
232   { "GL_OES_byte_coordinates",                    o(dummy_true),                                   ES1,       2002 },
233   { "GL_OES_compressed_ETC1_RGB8_texture",        o(OES_compressed_ETC1_RGB8_texture),             ES1 | ES2, 2005 },
234   { "GL_OES_compressed_paletted_texture",         o(dummy_true),                                   ES1,       2003 },
235   { "GL_OES_depth24",                             o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
236   { "GL_OES_depth32",                             o(dummy_false),                     DISABLE,                2005 },
237   { "GL_OES_depth_texture",                       o(ARB_depth_texture),                                  ES2, 2006 },
238#if FEATURE_OES_draw_texture
239   { "GL_OES_draw_texture",                        o(OES_draw_texture),                             ES1,       2004 },
240#endif
241#if FEATURE_OES_EGL_image
242   /*  FIXME: Mesa expects GL_OES_EGL_image to be available in OpenGL contexts. */
243   { "GL_OES_EGL_image",                           o(OES_EGL_image),                           GL | ES1 | ES2, 2006 },
244   { "GL_OES_EGL_image_external",                  o(OES_EGL_image_external),                       ES1 | ES2, 2010 },
245#endif
246   { "GL_OES_element_index_uint",                  o(dummy_true),                                   ES1 | ES2, 2005 },
247   { "GL_OES_fbo_render_mipmap",                   o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
248   { "GL_OES_fixed_point",                         o(dummy_true),                                   ES1,       2002 },
249   { "GL_OES_framebuffer_object",                  o(EXT_framebuffer_object),                       ES1,       2005 },
250   { "GL_OES_mapbuffer",                           o(dummy_true),                                   ES1 | ES2, 2005 },
251   { "GL_OES_matrix_get",                          o(dummy_true),                                   ES1,       2004 },
252   { "GL_OES_packed_depth_stencil",                o(EXT_packed_depth_stencil),                     ES1 | ES2, 2007 },
253   { "GL_OES_point_size_array",                    o(dummy_true),                                   ES1,       2004 },
254   { "GL_OES_point_sprite",                        o(ARB_point_sprite),                             ES1,       2004 },
255   { "GL_OES_query_matrix",                        o(dummy_true),                                   ES1,       2003 },
256   { "GL_OES_read_format",                         o(dummy_true),                              GL | ES1,       2003 },
257   { "GL_OES_rgb8_rgba8",                          o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
258   { "GL_OES_single_precision",                    o(dummy_true),                                   ES1,       2003 },
259   { "GL_OES_standard_derivatives",                o(OES_standard_derivatives),                           ES2, 2005 },
260   { "GL_OES_stencil1",                            o(dummy_false),                     DISABLE,                2005 },
261   { "GL_OES_stencil4",                            o(dummy_false),                     DISABLE,                2005 },
262   { "GL_OES_stencil8",                            o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
263   { "GL_OES_stencil_wrap",                        o(dummy_true),                                   ES1,       2002 },
264   { "GL_OES_texture_3D",                          o(EXT_texture3D),                                      ES2, 2005 },
265   { "GL_OES_texture_cube_map",                    o(ARB_texture_cube_map),                         ES1,       2007 },
266   { "GL_OES_texture_env_crossbar",                o(ARB_texture_env_crossbar),                     ES1,       2005 },
267   { "GL_OES_texture_mirrored_repeat",             o(dummy_true),                                   ES1,       2005 },
268   { "GL_OES_texture_npot",                        o(ARB_texture_non_power_of_two),                       ES2, 2005 },
269   { "GL_OES_vertex_array_object",                 o(dummy_true),                                   ES1 | ES2, 2010 },
270
271   /* Vendor extensions */
272   { "GL_3DFX_texture_compression_FXT1",           o(TDFX_texture_compression_FXT1),           GL,             1999 },
273   { "GL_AMD_conservative_depth",                  o(ARB_conservative_depth),                  GL,             2009 },
274   { "GL_AMD_draw_buffers_blend",                  o(ARB_draw_buffers_blend),                  GL,             2009 },
275   { "GL_AMD_seamless_cubemap_per_texture",        o(AMD_seamless_cubemap_per_texture),        GL,             2009 },
276   { "GL_AMD_shader_stencil_export",               o(ARB_shader_stencil_export),               GL,             2009 },
277   { "GL_APPLE_object_purgeable",                  o(APPLE_object_purgeable),                  GL,             2006 },
278   { "GL_APPLE_packed_pixels",                     o(APPLE_packed_pixels),                     GLL,            2002 },
279   { "GL_APPLE_texture_max_level",                 o(dummy_true),                                   ES1 | ES2, 2009 },
280   { "GL_APPLE_vertex_array_object",               o(dummy_true),                              GLL,            2002 },
281   { "GL_ATI_blend_equation_separate",             o(EXT_blend_equation_separate),             GL,             2003 },
282   { "GL_ATI_draw_buffers",                        o(dummy_true),                              GLL,            2002 },
283   { "GL_ATI_envmap_bumpmap",                      o(ATI_envmap_bumpmap),                      GLL,            2001 },
284   { "GL_ATI_fragment_shader",                     o(ATI_fragment_shader),                     GLL,            2001 },
285   { "GL_ATI_separate_stencil",                    o(ATI_separate_stencil),                    GLL,            2006 },
286   { "GL_ATI_texture_compression_3dc",             o(ATI_texture_compression_3dc),             GL,             2004 },
287   { "GL_ATI_texture_env_combine3",                o(ATI_texture_env_combine3),                GLL,            2002 },
288   { "GL_ATI_texture_float",                       o(ARB_texture_float),                       GL,             2002 },
289   { "GL_ATI_texture_mirror_once",                 o(ATI_texture_mirror_once),                 GL,             2006 },
290   { "GL_IBM_multimode_draw_arrays",               o(IBM_multimode_draw_arrays),               GL,             1998 },
291   { "GL_IBM_rasterpos_clip",                      o(IBM_rasterpos_clip),                      GLL,            1996 },
292   { "GL_IBM_texture_mirrored_repeat",             o(dummy_true),                              GLL,            1998 },
293   { "GL_INGR_blend_func_separate",                o(EXT_blend_func_separate),                 GLL,            1999 },
294   { "GL_MESA_pack_invert",                        o(MESA_pack_invert),                        GL,             2002 },
295   { "GL_MESA_resize_buffers",                     o(MESA_resize_buffers),                     GL,             1999 },
296   { "GL_MESA_texture_array",                      o(MESA_texture_array),                      GLL,            2007 },
297   { "GL_MESA_texture_signed_rgba",                o(EXT_texture_snorm),                       GL,             2009 },
298   { "GL_MESA_window_pos",                         o(ARB_window_pos),                          GLL,            2000 },
299   { "GL_MESA_ycbcr_texture",                      o(MESA_ycbcr_texture),                      GL,             2002 },
300   { "GL_NV_blend_square",                         o(NV_blend_square),                         GLL,            1999 },
301   { "GL_NV_conditional_render",                   o(NV_conditional_render),                   GL,             2008 },
302   { "GL_NV_depth_clamp",                          o(ARB_depth_clamp),                         GL,             2001 },
303   { "GL_NV_draw_buffers",                         o(dummy_true),                                         ES2, 2011 },
304   { "GL_NV_fbo_color_attachments",                o(EXT_framebuffer_object),                             ES2, 2010 },
305   { "GL_NV_fog_distance",                         o(NV_fog_distance),                         GLL,            2001 },
306   { "GL_NV_fragment_program",                     o(NV_fragment_program),                     GLL,            2001 },
307   { "GL_NV_fragment_program_option",              o(NV_fragment_program_option),              GLL,            2005 },
308   { "GL_NV_light_max_exponent",                   o(NV_light_max_exponent),                   GLL,            1999 },
309   { "GL_NV_packed_depth_stencil",                 o(EXT_packed_depth_stencil),                GL,             2000 },
310   { "GL_NV_point_sprite",                         o(NV_point_sprite),                         GL,             2001 },
311   { "GL_NV_primitive_restart",                    o(NV_primitive_restart),                    GLL,            2002 },
312   { "GL_NV_read_buffer",                          o(dummy_true),                              ES2,            2011 },
313   { "GL_NV_texgen_reflection",                    o(NV_texgen_reflection),                    GLL,            1999 },
314   { "GL_NV_texture_barrier",                      o(NV_texture_barrier),                      GL,             2009 },
315   { "GL_NV_texture_env_combine4",                 o(NV_texture_env_combine4),                 GLL,            1999 },
316   { "GL_NV_texture_rectangle",                    o(NV_texture_rectangle),                    GLL,            2000 },
317   { "GL_NV_vertex_program1_1",                    o(NV_vertex_program1_1),                    GLL,            2001 },
318   { "GL_NV_vertex_program",                       o(NV_vertex_program),                       GLL,            2000 },
319   { "GL_S3_s3tc",                                 o(S3_s3tc),                                 GL,             1999 },
320   { "GL_SGIS_generate_mipmap",                    o(dummy_true),                              GLL,            1997 },
321   { "GL_SGIS_texture_border_clamp",               o(ARB_texture_border_clamp),                GLL,            1997 },
322   { "GL_SGIS_texture_edge_clamp",                 o(dummy_true),                              GLL,            1997 },
323   { "GL_SGIS_texture_lod",                        o(SGIS_texture_lod),                        GLL,            1997 },
324   { "GL_SUN_multi_draw_arrays",                   o(dummy_true),                              GLL,            1999 },
325
326   { 0, 0, 0, 0 },
327};
328
329
330/**
331 * Given an extension name, lookup up the corresponding member of struct
332 * gl_extensions and return that member's offset (in bytes).  If the name is
333 * not found in the \c extension_table, return 0.
334 *
335 * \param name Name of extension.
336 * \return Offset of member in struct gl_extensions.
337 */
338static size_t
339name_to_offset(const char* name)
340{
341   const struct extension *i;
342
343   if (name == 0)
344      return 0;
345
346   for (i = extension_table; i->name != 0; ++i) {
347      if (strcmp(name, i->name) == 0)
348	 return i->offset;
349   }
350
351   return 0;
352}
353
354
355/**
356 * \brief Extensions enabled by default.
357 *
358 * These extensions are enabled by _mesa_init_extensions().
359 *
360 * XXX: Should these defaults also apply to GLES?
361 */
362static const size_t default_extensions[] = {
363   o(ARB_copy_buffer),
364   o(ARB_transpose_matrix),
365   o(ARB_window_pos),
366
367   o(EXT_compiled_vertex_array),
368   o(EXT_draw_range_elements),
369   o(EXT_packed_pixels),
370   o(EXT_rescale_normal),
371   o(EXT_separate_specular_color),
372   o(EXT_texture3D),
373
374   o(OES_standard_derivatives),
375
376   /* Vendor Extensions */
377   o(APPLE_packed_pixels),
378   o(IBM_multimode_draw_arrays),
379   o(IBM_rasterpos_clip),
380   o(NV_light_max_exponent),
381   o(NV_texgen_reflection),
382   o(SGIS_texture_lod),
383
384   0,
385};
386
387
388/**
389 * Enable all extensions suitable for a software-only renderer.
390 * This is a convenience function used by the XMesa, OSMesa, GGI drivers, etc.
391 */
392void
393_mesa_enable_sw_extensions(struct gl_context *ctx)
394{
395   /*ctx->Extensions.ARB_copy_buffer = GL_TRUE;*/
396   ctx->Extensions.ARB_depth_clamp = GL_TRUE;
397   ctx->Extensions.ARB_depth_texture = GL_TRUE;
398   ctx->Extensions.ARB_draw_elements_base_vertex = GL_TRUE;
399   ctx->Extensions.ARB_draw_instanced = GL_TRUE;
400   ctx->Extensions.ARB_explicit_attrib_location = GL_TRUE;
401   ctx->Extensions.ARB_fragment_coord_conventions = GL_TRUE;
402#if FEATURE_ARB_fragment_program
403   ctx->Extensions.ARB_fragment_program = GL_TRUE;
404   ctx->Extensions.ARB_fragment_program_shadow = GL_TRUE;
405#endif
406#if FEATURE_ARB_fragment_shader
407   ctx->Extensions.ARB_fragment_shader = GL_TRUE;
408#endif
409#if FEATURE_ARB_framebuffer_object
410   ctx->Extensions.ARB_framebuffer_object = GL_TRUE;
411#endif
412#if FEATURE_ARB_geometry_shader4 && 0
413   /* XXX re-enable when GLSL compiler again supports geometry shaders */
414   ctx->Extensions.ARB_geometry_shader4 = GL_TRUE;
415#endif
416   ctx->Extensions.ARB_half_float_pixel = GL_TRUE;
417   ctx->Extensions.ARB_half_float_vertex = GL_TRUE;
418   ctx->Extensions.ARB_map_buffer_range = GL_TRUE;
419#if FEATURE_queryobj
420   ctx->Extensions.ARB_occlusion_query = GL_TRUE;
421   ctx->Extensions.ARB_occlusion_query2 = GL_TRUE;
422#endif
423   ctx->Extensions.ARB_point_sprite = GL_TRUE;
424#if FEATURE_ARB_shader_objects
425   ctx->Extensions.ARB_shader_objects = GL_TRUE;
426   ctx->Extensions.EXT_separate_shader_objects = GL_TRUE;
427#endif
428#if FEATURE_ARB_shading_language_100
429   ctx->Extensions.ARB_shading_language_100 = GL_TRUE;
430#endif
431   ctx->Extensions.ARB_shadow = GL_TRUE;
432   ctx->Extensions.ARB_texture_border_clamp = GL_TRUE;
433   ctx->Extensions.ARB_texture_cube_map = GL_TRUE;
434   ctx->Extensions.ARB_texture_env_combine = GL_TRUE;
435   ctx->Extensions.ARB_texture_env_crossbar = GL_TRUE;
436   ctx->Extensions.ARB_texture_env_dot3 = GL_TRUE;
437   /*ctx->Extensions.ARB_texture_float = GL_TRUE;*/
438   ctx->Extensions.ARB_texture_non_power_of_two = GL_TRUE;
439   ctx->Extensions.ARB_texture_rg = GL_TRUE;
440   ctx->Extensions.ARB_texture_compression_rgtc = GL_TRUE;
441   ctx->Extensions.ARB_texture_storage = GL_TRUE;
442#if FEATURE_ARB_vertex_program
443   ctx->Extensions.ARB_vertex_program = GL_TRUE;
444#endif
445#if FEATURE_ARB_vertex_shader
446   ctx->Extensions.ARB_vertex_shader = GL_TRUE;
447#endif
448#if FEATURE_ARB_sync
449   ctx->Extensions.ARB_sync = GL_TRUE;
450#endif
451#if FEATURE_APPLE_object_purgeable
452   ctx->Extensions.APPLE_object_purgeable = GL_TRUE;
453#endif
454   ctx->Extensions.ATI_envmap_bumpmap = GL_TRUE;
455#if FEATURE_ATI_fragment_shader
456   ctx->Extensions.ATI_fragment_shader = GL_TRUE;
457#endif
458   ctx->Extensions.ATI_texture_compression_3dc = GL_TRUE;
459   ctx->Extensions.ATI_texture_env_combine3 = GL_TRUE;
460   ctx->Extensions.ATI_texture_mirror_once = GL_TRUE;
461   ctx->Extensions.ATI_separate_stencil = GL_TRUE;
462   ctx->Extensions.EXT_blend_color = GL_TRUE;
463   ctx->Extensions.EXT_blend_equation_separate = GL_TRUE;
464   ctx->Extensions.EXT_blend_func_separate = GL_TRUE;
465   ctx->Extensions.EXT_blend_minmax = GL_TRUE;
466   ctx->Extensions.EXT_depth_bounds_test = GL_TRUE;
467   ctx->Extensions.EXT_draw_buffers2 = GL_TRUE;
468   ctx->Extensions.EXT_fog_coord = GL_TRUE;
469#if FEATURE_EXT_framebuffer_object
470   ctx->Extensions.EXT_framebuffer_object = GL_TRUE;
471#endif
472#if FEATURE_EXT_framebuffer_blit
473   ctx->Extensions.EXT_framebuffer_blit = GL_TRUE;
474#endif
475   ctx->Extensions.EXT_packed_depth_stencil = GL_TRUE;
476#if FEATURE_EXT_pixel_buffer_object
477   ctx->Extensions.EXT_pixel_buffer_object = GL_TRUE;
478#endif
479   ctx->Extensions.EXT_point_parameters = GL_TRUE;
480   ctx->Extensions.EXT_provoking_vertex = GL_TRUE;
481   ctx->Extensions.EXT_shadow_funcs = GL_TRUE;
482   ctx->Extensions.EXT_secondary_color = GL_TRUE;
483   ctx->Extensions.EXT_stencil_two_side = GL_TRUE;
484   ctx->Extensions.EXT_texture_array = GL_TRUE;
485   ctx->Extensions.EXT_texture_compression_latc = GL_TRUE;
486   ctx->Extensions.EXT_texture_env_dot3 = GL_TRUE;
487   ctx->Extensions.EXT_texture_filter_anisotropic = GL_TRUE;
488   ctx->Extensions.EXT_texture_mirror_clamp = GL_TRUE;
489   ctx->Extensions.EXT_texture_shared_exponent = GL_TRUE;
490#if FEATURE_EXT_texture_sRGB
491   ctx->Extensions.EXT_texture_sRGB = GL_TRUE;
492   ctx->Extensions.EXT_texture_sRGB_decode = GL_TRUE;
493#endif
494   ctx->Extensions.EXT_texture_swizzle = GL_TRUE;
495#if FEATURE_EXT_transform_feedback
496   /*ctx->Extensions.EXT_transform_feedback = GL_TRUE;*/
497#endif
498   ctx->Extensions.EXT_vertex_array_bgra = GL_TRUE;
499   /*ctx->Extensions.IBM_multimode_draw_arrays = GL_TRUE;*/
500   ctx->Extensions.MESA_pack_invert = GL_TRUE;
501   ctx->Extensions.MESA_resize_buffers = GL_TRUE;
502   ctx->Extensions.MESA_texture_array = GL_TRUE;
503   ctx->Extensions.MESA_ycbcr_texture = GL_TRUE;
504   ctx->Extensions.NV_blend_square = GL_TRUE;
505   ctx->Extensions.NV_conditional_render = GL_TRUE;
506   /*ctx->Extensions.NV_light_max_exponent = GL_TRUE;*/
507   ctx->Extensions.NV_point_sprite = GL_TRUE;
508   ctx->Extensions.NV_texture_env_combine4 = GL_TRUE;
509   ctx->Extensions.NV_texture_rectangle = GL_TRUE;
510   /*ctx->Extensions.NV_texgen_reflection = GL_TRUE;*/
511#if FEATURE_NV_vertex_program
512   ctx->Extensions.NV_vertex_program = GL_TRUE;
513   ctx->Extensions.NV_vertex_program1_1 = GL_TRUE;
514#endif
515#if FEATURE_NV_fragment_program
516   ctx->Extensions.NV_fragment_program = GL_TRUE;
517#endif
518#if FEATURE_NV_fragment_program && FEATURE_ARB_fragment_program
519   ctx->Extensions.NV_fragment_program_option = GL_TRUE;
520#endif
521#if FEATURE_ARB_vertex_program || FEATURE_ARB_fragment_program
522   ctx->Extensions.EXT_gpu_program_parameters = GL_TRUE;
523#endif
524#if FEATURE_texture_fxt1
525   _mesa_enable_extension(ctx, "GL_3DFX_texture_compression_FXT1");
526#endif
527#if FEATURE_texture_s3tc
528   if (ctx->Mesa_DXTn) {
529      _mesa_enable_extension(ctx, "GL_EXT_texture_compression_s3tc");
530      _mesa_enable_extension(ctx, "GL_S3_s3tc");
531   }
532#endif
533}
534
535
536/**
537 * Enable all OpenGL 1.3 features and extensions.
538 * A convenience function to be called by drivers.
539 */
540void
541_mesa_enable_1_3_extensions(struct gl_context *ctx)
542{
543   ctx->Extensions.ARB_texture_border_clamp = GL_TRUE;
544   ctx->Extensions.ARB_texture_cube_map = GL_TRUE;
545   ctx->Extensions.ARB_texture_env_combine = GL_TRUE;
546   ctx->Extensions.ARB_texture_env_dot3 = GL_TRUE;
547   /*ctx->Extensions.ARB_transpose_matrix = GL_TRUE;*/
548}
549
550
551
552/**
553 * Enable all OpenGL 1.4 features and extensions.
554 * A convenience function to be called by drivers.
555 */
556void
557_mesa_enable_1_4_extensions(struct gl_context *ctx)
558{
559   ctx->Extensions.ARB_depth_texture = GL_TRUE;
560   ctx->Extensions.ARB_shadow = GL_TRUE;
561   ctx->Extensions.ARB_texture_env_crossbar = GL_TRUE;
562   ctx->Extensions.ARB_window_pos = GL_TRUE;
563   ctx->Extensions.EXT_blend_color = GL_TRUE;
564   ctx->Extensions.EXT_blend_func_separate = GL_TRUE;
565   ctx->Extensions.EXT_blend_minmax = GL_TRUE;
566   ctx->Extensions.EXT_fog_coord = GL_TRUE;
567   ctx->Extensions.EXT_point_parameters = GL_TRUE;
568   ctx->Extensions.EXT_secondary_color = GL_TRUE;
569}
570
571
572/**
573 * Enable all OpenGL 1.5 features and extensions.
574 * A convenience function to be called by drivers.
575 */
576void
577_mesa_enable_1_5_extensions(struct gl_context *ctx)
578{
579   ctx->Extensions.ARB_occlusion_query = GL_TRUE;
580   ctx->Extensions.EXT_shadow_funcs = GL_TRUE;
581}
582
583
584/**
585 * Enable all OpenGL 2.0 features and extensions.
586 * A convenience function to be called by drivers.
587 */
588void
589_mesa_enable_2_0_extensions(struct gl_context *ctx)
590{
591#if FEATURE_ARB_fragment_shader
592   ctx->Extensions.ARB_fragment_shader = GL_TRUE;
593#endif
594   ctx->Extensions.ARB_point_sprite = GL_TRUE;
595   ctx->Extensions.EXT_blend_equation_separate = GL_TRUE;
596   ctx->Extensions.ARB_texture_non_power_of_two = GL_TRUE;
597#if FEATURE_ARB_shader_objects
598   ctx->Extensions.ARB_shader_objects = GL_TRUE;
599#endif
600#if FEATURE_ARB_shading_language_100
601   ctx->Extensions.ARB_shading_language_100 = GL_TRUE;
602#endif
603   ctx->Extensions.EXT_stencil_two_side = GL_TRUE;
604#if FEATURE_ARB_vertex_shader
605   ctx->Extensions.ARB_vertex_shader = GL_TRUE;
606#endif
607}
608
609
610/**
611 * Enable all OpenGL 2.1 features and extensions.
612 * A convenience function to be called by drivers.
613 */
614void
615_mesa_enable_2_1_extensions(struct gl_context *ctx)
616{
617#if FEATURE_EXT_pixel_buffer_object
618   ctx->Extensions.EXT_pixel_buffer_object = GL_TRUE;
619#endif
620#if FEATURE_EXT_texture_sRGB
621   ctx->Extensions.EXT_texture_sRGB = GL_TRUE;
622#endif
623}
624
625
626/**
627 * Either enable or disable the named extension.
628 * \return GL_TRUE for success, GL_FALSE if invalid extension name
629 */
630static GLboolean
631set_extension( struct gl_context *ctx, const char *name, GLboolean state )
632{
633   size_t offset;
634
635   if (ctx->Extensions.String) {
636      /* The string was already queried - can't change it now! */
637      _mesa_problem(ctx, "Trying to enable/disable extension after glGetString(GL_EXTENSIONS): %s", name);
638      return GL_FALSE;
639   }
640
641   offset = name_to_offset(name);
642   if (offset == 0) {
643      _mesa_problem(ctx, "Trying to enable/disable unknown extension %s",
644	            name);
645      return GL_FALSE;
646   } else if (offset == o(dummy_true) && state == GL_FALSE) {
647      _mesa_problem(ctx, "Trying to disable a permanently enabled extension: "
648	                  "%s", name);
649      return GL_FALSE;
650   } else {
651      GLboolean *base = (GLboolean *) &ctx->Extensions;
652      base[offset] = state;
653      return GL_TRUE;
654   }
655}
656
657
658/**
659 * Enable the named extension.
660 * Typically called by drivers.
661 */
662void
663_mesa_enable_extension( struct gl_context *ctx, const char *name )
664{
665   if (!set_extension(ctx, name, GL_TRUE))
666      _mesa_problem(ctx, "Trying to enable unknown extension: %s", name);
667}
668
669
670/**
671 * Disable the named extension.
672 * XXX is this really needed???
673 */
674void
675_mesa_disable_extension( struct gl_context *ctx, const char *name )
676{
677   if (!set_extension(ctx, name, GL_FALSE))
678      _mesa_problem(ctx, "Trying to disable unknown extension: %s", name);
679}
680
681
682/**
683 * Test if the named extension is enabled in this context.
684 */
685GLboolean
686_mesa_extension_is_enabled( struct gl_context *ctx, const char *name )
687{
688   size_t offset;
689   GLboolean *base;
690
691   if (name == 0)
692      return GL_FALSE;
693
694   offset = name_to_offset(name);
695   if (offset == 0)
696      return GL_FALSE;
697   base = (GLboolean *) &ctx->Extensions;
698   return base[offset];
699}
700
701
702/**
703 * \brief Apply the \c MESA_EXTENSION_OVERRIDE environment variable.
704 *
705 * \c MESA_EXTENSION_OVERRIDE is a space-separated list of extensions to
706 * enable or disable. The list is processed thus:
707 *    - Enable recognized extension names that are prefixed with '+'.
708 *    - Disable recognized extension names that are prefixed with '-'.
709 *    - Enable recognized extension names that are not prefixed.
710 *    - Collect unrecognized extension names in a new string.
711 *
712 * \return Space-separated list of unrecognized extension names (which must
713 *    be freed). Does not return \c NULL.
714 */
715static char *
716get_extension_override( struct gl_context *ctx )
717{
718   const char *env_const = _mesa_getenv("MESA_EXTENSION_OVERRIDE");
719   char *env;
720   char *ext;
721   char *extra_exts;
722   int len;
723
724   if (env_const == NULL) {
725      /* Return the empty string rather than NULL. This simplifies the logic
726       * of client functions. */
727      return calloc(4, sizeof(char));
728   }
729
730   /* extra_exts: List of unrecognized extensions. */
731   extra_exts = calloc(ALIGN(strlen(env_const) + 2, 4), sizeof(char));
732
733   /* Copy env_const because strtok() is destructive. */
734   env = strdup(env_const);
735   for (ext = strtok(env, " "); ext != NULL; ext = strtok(NULL, " ")) {
736      int enable;
737      int recognized;
738      switch (ext[0]) {
739      case '+':
740         enable = 1;
741         ++ext;
742         break;
743      case '-':
744         enable = 0;
745         ++ext;
746         break;
747      default:
748         enable = 1;
749         break;
750      }
751      recognized = set_extension(ctx, ext, enable);
752      if (!recognized) {
753         strcat(extra_exts, ext);
754         strcat(extra_exts, " ");
755      }
756   }
757
758   free(env);
759
760   /* Remove trailing space. */
761   len = strlen(extra_exts);
762   if (len > 0 && extra_exts[len - 1] == ' ')
763      extra_exts[len - 1] = '\0';
764
765   return extra_exts;
766}
767
768
769/**
770 * \brief Initialize extension tables and enable default extensions.
771 *
772 * This should be called during context initialization.
773 * Note: Sets gl_extensions.dummy_true to true.
774 */
775void
776_mesa_init_extensions( struct gl_context *ctx )
777{
778   GLboolean *base = (GLboolean *) &ctx->Extensions;
779   GLboolean *sentinel = base + o(extension_sentinel);
780   GLboolean *i;
781   const size_t *j;
782
783   /* First, turn all extensions off. */
784   for (i = base; i != sentinel; ++i)
785      *i = GL_FALSE;
786
787   /* Then, selectively turn default extensions on. */
788   ctx->Extensions.dummy_true = GL_TRUE;
789   for (j = default_extensions; *j != 0; ++j)
790      base[*j] = GL_TRUE;
791}
792
793
794typedef unsigned short extension_index;
795
796
797/**
798 * Compare two entries of the extensions table.  Sorts first by year,
799 * then by name.
800 *
801 * Arguments are indices into extension_table.
802 */
803static int
804extension_compare(const void *p1, const void *p2)
805{
806   extension_index i1 = * (const extension_index *) p1;
807   extension_index i2 = * (const extension_index *) p2;
808   const struct extension *e1 = &extension_table[i1];
809   const struct extension *e2 = &extension_table[i2];
810   int res;
811
812   res = (int)e1->year - (int)e2->year;
813
814   if (res == 0) {
815      res = strcmp(e1->name, e2->name);
816   }
817
818   return res;
819}
820
821
822/**
823 * Construct the GL_EXTENSIONS string.  Called the first time that
824 * glGetString(GL_EXTENSIONS) is called.
825 */
826GLubyte*
827_mesa_make_extension_string(struct gl_context *ctx)
828{
829   /* The extension string. */
830   char *exts = 0;
831   /* Length of extension string. */
832   size_t length = 0;
833   /* Number of extensions */
834   unsigned count;
835   /* Indices of the extensions sorted by year */
836   extension_index *extension_indices;
837   /* String of extra extensions. */
838   char *extra_extensions = get_extension_override(ctx);
839   GLboolean *base = (GLboolean *) &ctx->Extensions;
840   const struct extension *i;
841   unsigned j;
842   unsigned maxYear = ~0;
843
844   /* Check if the MESA_EXTENSION_MAX_YEAR env var is set */
845   {
846      const char *env = getenv("MESA_EXTENSION_MAX_YEAR");
847      if (env) {
848         maxYear = atoi(env);
849         _mesa_debug(ctx, "Note: limiting GL extensions to %u or earlier\n",
850                     maxYear);
851      }
852   }
853
854   /* Compute length of the extension string. */
855   count = 0;
856   for (i = extension_table; i->name != 0; ++i) {
857      if (base[i->offset] &&
858          i->year <= maxYear &&
859          (i->api_set & (1 << ctx->API))) {
860	 length += strlen(i->name) + 1; /* +1 for space */
861	 ++count;
862      }
863   }
864   if (extra_extensions != NULL)
865      length += 1 + strlen(extra_extensions); /* +1 for space */
866
867   exts = (char *) calloc(ALIGN(length + 1, 4), sizeof(char));
868   if (exts == NULL) {
869      free(extra_extensions);
870      return NULL;
871   }
872
873   extension_indices = malloc(count * sizeof(extension_index));
874   if (extension_indices == NULL) {
875      free(exts);
876      free(extra_extensions);
877      return NULL;
878   }
879
880   /* Sort extensions in chronological order because certain old applications (e.g.,
881    * Quake3 demo) store the extension list in a static size buffer so chronologically
882    * order ensure that the extensions that such applications expect will fit into
883    * that buffer.
884    */
885   j = 0;
886   for (i = extension_table; i->name != 0; ++i) {
887      if (base[i->offset] &&
888          i->year <= maxYear &&
889          (i->api_set & (1 << ctx->API))) {
890         extension_indices[j++] = i - extension_table;
891      }
892   }
893   assert(j == count);
894   qsort(extension_indices, count, sizeof *extension_indices, extension_compare);
895
896   /* Build the extension string.*/
897   for (j = 0; j < count; ++j) {
898      i = &extension_table[extension_indices[j]];
899      assert(base[i->offset] && (i->api_set & (1 << ctx->API)));
900      strcat(exts, i->name);
901      strcat(exts, " ");
902   }
903   free(extension_indices);
904   if (extra_extensions != 0) {
905      strcat(exts, extra_extensions);
906      free(extra_extensions);
907   }
908
909   return (GLubyte *) exts;
910}
911
912/**
913 * Return number of enabled extensions.
914 */
915GLuint
916_mesa_get_extension_count(struct gl_context *ctx)
917{
918   GLboolean *base;
919   const struct extension *i;
920
921   /* only count once */
922   if (ctx->Extensions.Count != 0)
923      return ctx->Extensions.Count;
924
925   base = (GLboolean *) &ctx->Extensions;
926   for (i = extension_table; i->name != 0; ++i) {
927      if (base[i->offset] && (i->api_set & (1 << ctx->API))) {
928	 ctx->Extensions.Count++;
929      }
930   }
931   return ctx->Extensions.Count;
932}
933
934/**
935 * Return name of i-th enabled extension
936 */
937const GLubyte *
938_mesa_get_enabled_extension(struct gl_context *ctx, GLuint index)
939{
940   const GLboolean *base;
941   size_t n;
942   const struct extension *i;
943
944   base = (GLboolean*) &ctx->Extensions;
945   n = 0;
946   for (i = extension_table; i->name != 0; ++i) {
947      if (base[i->offset] && (i->api_set & (1 << ctx->API))) {
948         if (n == index)
949            return (const GLubyte*) i->name;
950         else
951            ++n;
952      }
953   }
954
955   return NULL;
956}
957