src/mesa/main/extensions.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  5.1
   4  *
   5  * Copyright (C) 1999-2003  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 #include "glheader.h"
  27 #include "imports.h"
  28 #include "context.h"
  29 #include "extensions.h"
  30 #include "simple_list.h"
  31 #include "mtypes.h"
  32
  33
  34 #define F(x) (int)(unsigned long)&(((struct gl_extensions *)0)->x)
  35 #define ON GL_TRUE
  36 #define OFF GL_FALSE
  37
  38
  39 static const struct {
  40    GLboolean enabled;
  41    const char *name;
  42    int flag_offset;
  43 } default_extensions[] = {
  44    { OFF, "GL_ARB_depth_texture",              F(ARB_depth_texture) },
  45    { OFF, "GL_ARB_fragment_program",           F(ARB_fragment_program) },
  46    { OFF, "GL_ARB_imaging",                    F(ARB_imaging) },
  47    { OFF, "GL_ARB_multisample",                F(ARB_multisample) },
  48    { OFF, "GL_ARB_multitexture",               F(ARB_multitexture) },
  49    { OFF, "GL_ARB_occlusion_query",            F(ARB_occlusion_query) },
  50    { OFF, "GL_ARB_point_parameters",           F(EXT_point_parameters) },
  51    { OFF, "GL_ARB_point_sprite",               F(ARB_point_sprite) },
  52    { OFF, "GL_ARB_shadow",                     F(ARB_shadow) },
  53    { OFF, "GL_ARB_shadow_ambient",             F(SGIX_shadow_ambient) },
  54    { OFF, "GL_ARB_texture_border_clamp",       F(ARB_texture_border_clamp) },
  55    { OFF, "GL_ARB_texture_compression",        F(ARB_texture_compression) },
  56    { OFF, "GL_ARB_texture_cube_map",           F(ARB_texture_cube_map) },
  57    { OFF, "GL_ARB_texture_env_add",            F(EXT_texture_env_add) },
  58    { OFF, "GL_ARB_texture_env_combine",        F(ARB_texture_env_combine) },
  59    { OFF, "GL_ARB_texture_env_crossbar",       F(ARB_texture_env_crossbar) },
  60    { OFF, "GL_ARB_texture_env_dot3",           F(ARB_texture_env_dot3) },
  61    { OFF, "GL_ARB_texture_mirrored_repeat",    F(ARB_texture_mirrored_repeat)},
  62    { OFF, "GL_ARB_texture_non_power_of_two",   F(ARB_texture_non_power_of_two)},
  63    { ON,  "GL_ARB_transpose_matrix",           0 },
  64    { OFF, "GL_ARB_vertex_buffer_object",       F(ARB_vertex_buffer_object) },
  65    { OFF, "GL_ARB_vertex_program",             F(ARB_vertex_program) },
  66    { ON,  "GL_ARB_window_pos",                 F(ARB_window_pos) },
  67    { ON,  "GL_EXT_abgr",                       0 },
  68    { ON,  "GL_EXT_bgra",                       0 },
  69    { OFF, "GL_EXT_blend_color",                F(EXT_blend_color) },
  70    { OFF, "GL_EXT_blend_func_separate",        F(EXT_blend_func_separate) },
  71    { OFF, "GL_EXT_blend_logic_op",             F(EXT_blend_logic_op) },
  72    { OFF, "GL_EXT_blend_minmax",               F(EXT_blend_minmax) },
  73    { OFF, "GL_EXT_blend_subtract",             F(EXT_blend_subtract) },
  74    { ON,  "GL_EXT_clip_volume_hint",           0 },
  75    { ON,  "GL_EXT_compiled_vertex_array",      F(EXT_compiled_vertex_array) },
  76    { OFF, "GL_EXT_convolution",                F(EXT_convolution) },
  77    { ON,  "GL_EXT_copy_texture",               0 },
  78    { OFF, "GL_EXT_depth_bounds_test",          F(EXT_depth_bounds_test) },
  79    { ON,  "GL_EXT_draw_range_elements",        0 },
  80    { OFF, "GL_EXT_fog_coord",                  F(EXT_fog_coord) },
  81    { OFF, "GL_EXT_histogram",                  F(EXT_histogram) },
  82    { OFF, "GL_EXT_multi_draw_arrays",          F(EXT_multi_draw_arrays) },
  83    { ON,  "GL_EXT_packed_pixels",              0 },
  84    { OFF, "GL_EXT_paletted_texture",           F(EXT_paletted_texture) },
  85    { OFF, "GL_EXT_point_parameters",           F(EXT_point_parameters) },
  86    { ON,  "GL_EXT_polygon_offset",             0 },
  87    { ON,  "GL_EXT_rescale_normal",             0 },
  88    { OFF, "GL_EXT_secondary_color",            F(EXT_secondary_color) },
  89    { ON,  "GL_EXT_separate_specular_color",    0 },
  90    { OFF, "GL_EXT_shadow_funcs",               F(EXT_shadow_funcs) },
  91    { OFF, "GL_EXT_shared_texture_palette",     F(EXT_shared_texture_palette) },
  92    { OFF, "GL_EXT_stencil_two_side",           F(EXT_stencil_two_side) },
  93    { OFF, "GL_EXT_stencil_wrap",               F(EXT_stencil_wrap) },
  94    { ON,  "GL_EXT_subtexture",                 0 },
  95    { ON,  "GL_EXT_texture",                    0 },
  96    { ON,  "GL_EXT_texture3D",                  F(EXT_texture3D) },
  97    { OFF, "GL_EXT_texture_compression_s3tc",   F(EXT_texture_compression_s3tc) },
  98    { ON,  "GL_EXT_texture_edge_clamp",         F(SGIS_texture_edge_clamp) },
  99    { OFF, "GL_EXT_texture_env_add",            F(EXT_texture_env_add) },
 100    { OFF, "GL_EXT_texture_env_combine",        F(EXT_texture_env_combine) },
 101    { OFF, "GL_EXT_texture_env_dot3",           F(EXT_texture_env_dot3) },
 102    { OFF, "GL_EXT_texture_filter_anisotropic", F(EXT_texture_filter_anisotropic) },
 103    { OFF, "GL_EXT_texture_lod_bias",           F(EXT_texture_lod_bias) },
 104    { OFF, "GL_EXT_texture_mirror_clamp",       F(EXT_texture_mirror_clamp) },
 105    { ON,  "GL_EXT_texture_object",             0 },
 106    { OFF, "GL_EXT_texture_rectangle",          F(NV_texture_rectangle) },
 107    { ON,  "GL_EXT_vertex_array",               0 },
 108    { OFF, "GL_EXT_vertex_array_set",           F(EXT_vertex_array_set) },
 109    { OFF, "GL_3DFX_texture_compression_FXT1",  F(TDFX_texture_compression_FXT1) },
 110    { OFF, "GL_APPLE_client_storage",           F(APPLE_client_storage) },
 111    { ON,  "GL_APPLE_packed_pixels",            0 },
 112    { OFF, "GL_ATI_texture_env_combine3",       F(ATI_texture_env_combine3)},
 113    { OFF, "GL_ATI_texture_mirror_once",        F(ATI_texture_mirror_once)},
 114    { OFF, "GL_HP_occlusion_test",              F(HP_occlusion_test) },
 115    { OFF, "GL_IBM_multimode_draw_arrays",      F(IBM_multimode_draw_arrays) },
 116    { ON,  "GL_IBM_rasterpos_clip",             F(IBM_rasterpos_clip) },
 117    { OFF, "GL_IBM_texture_mirrored_repeat",    F(ARB_texture_mirrored_repeat)},
 118    { OFF, "GL_INGR_blend_func_separate",       F(EXT_blend_func_separate) },
 119    { OFF, "GL_MESA_pack_invert",               F(MESA_pack_invert) },
 120    { OFF, "GL_MESA_packed_depth_stencil",      F(MESA_packed_depth_stencil) },
 121    { OFF, "GL_MESA_program_debug",             F(MESA_program_debug) },
 122    { OFF, "GL_MESA_resize_buffers",            F(MESA_resize_buffers) },
 123    { OFF, "GL_MESA_ycbcr_texture",             F(MESA_ycbcr_texture) },
 124    { ON,  "GL_MESA_window_pos",                F(ARB_window_pos) },
 125    { OFF, "GL_NV_blend_square",                F(NV_blend_square) },
 126    { OFF, "GL_NV_fragment_program",            F(NV_fragment_program) },
 127    { ON,  "GL_NV_light_max_exponent",          0 },
 128    { OFF, "GL_NV_point_sprite",                F(NV_point_sprite) },
 129    { OFF, "GL_NV_texture_rectangle",           F(NV_texture_rectangle) },
 130    { ON,  "GL_NV_texgen_reflection",           0 },
 131    { OFF, "GL_NV_vertex_program",              F(NV_vertex_program) },
 132    { OFF, "GL_NV_vertex_program1_1",           F(NV_vertex_program1_1) },
 133    { OFF, "GL_SGI_color_matrix",               F(SGI_color_matrix) },
 134    { OFF, "GL_SGI_color_table",                F(SGI_color_table) },
 135    { OFF, "GL_SGI_texture_color_table",        F(SGI_texture_color_table) },
 136    { OFF, "GL_SGIS_generate_mipmap",           F(SGIS_generate_mipmap) },
 137    { OFF, "GL_SGIS_pixel_texture",             F(SGIS_pixel_texture) },
 138    { OFF, "GL_SGIS_texture_border_clamp",      F(ARB_texture_border_clamp) },
 139    { ON,  "GL_SGIS_texture_edge_clamp",        F(SGIS_texture_edge_clamp) },
 140    { ON,  "GL_SGIS_texture_lod",               0 },
 141    { OFF, "GL_SGIX_depth_texture",             F(SGIX_depth_texture) },
 142    { OFF, "GL_SGIX_pixel_texture",             F(SGIX_pixel_texture) },
 143    { OFF, "GL_SGIX_shadow",                    F(SGIX_shadow) },
 144    { OFF, "GL_SGIX_shadow_ambient",            F(SGIX_shadow_ambient) },
 145    { OFF, "GL_SUN_multi_draw_arrays",          F(EXT_multi_draw_arrays) },
 146    { OFF, "GL_S3_s3tc",                        F(S3_s3tc) },
 147 };
 148
 149
 150
 151 /**
 152  * Enable all extensions suitable for a software-only renderer.
 153  * This is a convenience function used by the XMesa, OSMesa, GGI drivers, etc.
 154  */
 155 void
 156 _mesa_enable_sw_extensions(GLcontext *ctx)
 157 {
 158    ctx->Extensions.ARB_depth_texture = GL_TRUE;
 159 #if FEATURE_ARB_fragment_program
 160    /*ctx->Extensions.ARB_fragment_program = GL_TRUE;*/
 161 #endif
 162    ctx->Extensions.ARB_imaging = GL_TRUE;
 163    ctx->Extensions.ARB_multitexture = GL_TRUE;
 164 #if FEATURE_ARB_occlusion_query
 165    ctx->Extensions.ARB_occlusion_query = GL_TRUE;
 166 #endif
 167    ctx->Extensions.ARB_point_sprite = GL_TRUE;
 168    ctx->Extensions.ARB_shadow = GL_TRUE;
 169    ctx->Extensions.ARB_texture_border_clamp = GL_TRUE;
 170    ctx->Extensions.ARB_texture_cube_map = GL_TRUE;
 171    ctx->Extensions.ARB_texture_env_combine = GL_TRUE;
 172    ctx->Extensions.ARB_texture_env_crossbar = GL_TRUE;
 173    ctx->Extensions.ARB_texture_env_dot3 = GL_TRUE;
 174    ctx->Extensions.ARB_texture_mirrored_repeat = GL_TRUE;
 175    ctx->Extensions.ARB_texture_non_power_of_two = GL_TRUE;
 176 #if FEATURE_ARB_vertex_program
 177    /*ctx->Extensions.ARB_vertex_program = GL_TRUE;*/
 178 #endif
 179 #if FEATURE_ARB_vertex_buffer_object
 180    ctx->Extensions.ARB_vertex_buffer_object = GL_TRUE;
 181 #endif
 182    ctx->Extensions.ATI_texture_env_combine3 = GL_TRUE;
 183    ctx->Extensions.ATI_texture_mirror_once = GL_TRUE;
 184    ctx->Extensions.EXT_blend_color = GL_TRUE;
 185    ctx->Extensions.EXT_blend_func_separate = GL_TRUE;
 186    ctx->Extensions.EXT_blend_logic_op = GL_TRUE;
 187    ctx->Extensions.EXT_blend_minmax = GL_TRUE;
 188    ctx->Extensions.EXT_blend_subtract = GL_TRUE;
 189    ctx->Extensions.EXT_convolution = GL_TRUE;
 190    ctx->Extensions.EXT_depth_bounds_test = GL_TRUE;
 191    ctx->Extensions.EXT_fog_coord = GL_TRUE;
 192    ctx->Extensions.EXT_histogram = GL_TRUE;
 193    ctx->Extensions.EXT_multi_draw_arrays = GL_TRUE;
 194    ctx->Extensions.EXT_paletted_texture = GL_TRUE;
 195    ctx->Extensions.EXT_point_parameters = GL_TRUE;
 196    ctx->Extensions.EXT_shadow_funcs = GL_TRUE;
 197    ctx->Extensions.EXT_secondary_color = GL_TRUE;
 198    ctx->Extensions.EXT_shared_texture_palette = GL_TRUE;
 199    ctx->Extensions.EXT_stencil_wrap = GL_TRUE;
 200    ctx->Extensions.EXT_stencil_two_side = GL_TRUE;
 201    ctx->Extensions.EXT_texture_env_add = GL_TRUE;
 202    ctx->Extensions.EXT_texture_env_combine = GL_TRUE;
 203    ctx->Extensions.EXT_texture_env_dot3 = GL_TRUE;
 204    ctx->Extensions.EXT_texture_mirror_clamp = GL_TRUE;
 205    ctx->Extensions.EXT_texture_lod_bias = GL_TRUE;
 206    ctx->Extensions.HP_occlusion_test = GL_TRUE;
 207    ctx->Extensions.IBM_multimode_draw_arrays = GL_TRUE;
 208    ctx->Extensions.MESA_pack_invert = GL_TRUE;
 209 #if FEATURE_MESA_program_debug
 210    ctx->Extensions.MESA_program_debug = GL_TRUE;
 211 #endif
 212    ctx->Extensions.MESA_resize_buffers = GL_TRUE;
 213    ctx->Extensions.MESA_ycbcr_texture = GL_TRUE;
 214    ctx->Extensions.NV_blend_square = GL_TRUE;
 215    /*ctx->Extensions.NV_light_max_exponent = GL_TRUE;*/
 216    ctx->Extensions.NV_point_sprite = GL_TRUE;
 217    ctx->Extensions.NV_texture_rectangle = GL_TRUE;
 218    /*ctx->Extensions.NV_texgen_reflection = GL_TRUE;*/
 219 #if FEATURE_NV_vertex_program
 220    ctx->Extensions.NV_vertex_program = GL_TRUE;
 221    ctx->Extensions.NV_vertex_program1_1 = GL_TRUE;
 222 #endif
 223 #if FEATURE_NV_fragment_program
 224    ctx->Extensions.NV_fragment_program = GL_TRUE;
 225 #endif
 226    ctx->Extensions.SGI_color_matrix = GL_TRUE;
 227    ctx->Extensions.SGI_color_table = GL_TRUE;
 228    ctx->Extensions.SGI_texture_color_table = GL_TRUE;
 229    ctx->Extensions.SGIS_generate_mipmap = GL_TRUE;
 230    ctx->Extensions.SGIS_pixel_texture = GL_TRUE;
 231    ctx->Extensions.SGIS_texture_edge_clamp = GL_TRUE;
 232    ctx->Extensions.SGIX_depth_texture = GL_TRUE;
 233    ctx->Extensions.SGIX_pixel_texture = GL_TRUE;
 234    ctx->Extensions.SGIX_shadow = GL_TRUE;
 235    ctx->Extensions.SGIX_shadow_ambient = GL_TRUE;
 236 }
 237
 238
 239 /**
 240  * Enable GL_ARB_imaging and all the EXT extensions that are subsets of it.
 241  */
 242 void
 243 _mesa_enable_imaging_extensions(GLcontext *ctx)
 244 {
 245    ctx->Extensions.ARB_imaging = GL_TRUE;
 246    ctx->Extensions.EXT_blend_color = GL_TRUE;
 247    ctx->Extensions.EXT_blend_minmax = GL_TRUE;
 248    ctx->Extensions.EXT_blend_subtract = GL_TRUE;
 249    ctx->Extensions.EXT_convolution = GL_TRUE;
 250    ctx->Extensions.EXT_histogram = GL_TRUE;
 251    ctx->Extensions.SGI_color_matrix = GL_TRUE;
 252    ctx->Extensions.SGI_color_table = GL_TRUE;
 253 }
 254
 255
 256
 257 /**
 258  * Enable all OpenGL 1.3 features and extensions.
 259  * A convenience function to be called by drivers.
 260  */
 261 void
 262 _mesa_enable_1_3_extensions(GLcontext *ctx)
 263 {
 264    ctx->Extensions.ARB_multisample = GL_TRUE;
 265    ctx->Extensions.ARB_multitexture = GL_TRUE;
 266    ctx->Extensions.ARB_texture_border_clamp = GL_TRUE;
 267    ctx->Extensions.ARB_texture_compression = GL_TRUE;
 268    ctx->Extensions.ARB_texture_cube_map = GL_TRUE;
 269    ctx->Extensions.ARB_texture_env_combine = GL_TRUE;
 270    ctx->Extensions.ARB_texture_env_dot3 = GL_TRUE;
 271    ctx->Extensions.EXT_texture_env_add = GL_TRUE;
 272    /*ctx->Extensions.ARB_transpose_matrix = GL_TRUE;*/
 273 }
 274
 275
 276
 277 /**
 278  * Enable all OpenGL 1.4 features and extensions.
 279  * A convenience function to be called by drivers.
 280  */
 281 void
 282 _mesa_enable_1_4_extensions(GLcontext *ctx)
 283 {
 284    ctx->Extensions.ARB_depth_texture = GL_TRUE;
 285    ctx->Extensions.ARB_fragment_program = GL_TRUE;
 286    ctx->Extensions.ARB_shadow = GL_TRUE;
 287    ctx->Extensions.ARB_texture_env_crossbar = GL_TRUE;
 288    ctx->Extensions.ARB_texture_mirrored_repeat = GL_TRUE;
 289    ctx->Extensions.ARB_vertex_program = GL_TRUE;
 290    ctx->Extensions.ARB_window_pos = GL_TRUE;
 291    ctx->Extensions.EXT_blend_color = GL_TRUE;
 292    ctx->Extensions.EXT_blend_func_separate = GL_TRUE;
 293    ctx->Extensions.EXT_blend_logic_op = GL_TRUE;
 294    ctx->Extensions.EXT_blend_minmax = GL_TRUE;
 295    ctx->Extensions.EXT_blend_subtract = GL_TRUE;
 296    ctx->Extensions.EXT_fog_coord = GL_TRUE;
 297    ctx->Extensions.EXT_multi_draw_arrays = GL_TRUE;
 298    ctx->Extensions.EXT_point_parameters = GL_TRUE;
 299    ctx->Extensions.EXT_secondary_color = GL_TRUE;
 300    ctx->Extensions.EXT_stencil_wrap = GL_TRUE;
 301    ctx->Extensions.EXT_texture_lod_bias = GL_TRUE;
 302    ctx->Extensions.SGIS_generate_mipmap = GL_TRUE;
 303 }
 304
 305
 306 /**
 307  * Enable all OpenGL 1.5 features and extensions.
 308  * A convenience function to be called by drivers.
 309  */
 310 void
 311 _mesa_enable_1_5_extensions(GLcontext *ctx)
 312 {
 313    ctx->Extensions.ARB_occlusion_query = GL_TRUE;
 314    ctx->Extensions.ARB_vertex_buffer_object = GL_TRUE;
 315    ctx->Extensions.ARB_texture_non_power_of_two = GL_TRUE;
 316    ctx->Extensions.EXT_shadow_funcs = GL_TRUE;
 317 }
 318
 319
 320 /**
 321  * Either enable or disable the named extension.
 322  */
 323 static void
 324 set_extension( GLcontext *ctx, const char *name, GLboolean state )
 325 {
 326    GLboolean *base = (GLboolean *) &ctx->Extensions;
 327    GLuint i;
 328
 329    if (ctx->Extensions.String) {
 330       /* The string was already queried - can't change it now! */
 331       _mesa_problem(ctx, "Trying to enable/disable extension after glGetString(GL_EXTENSIONS): %s", name);
 332       return;
 333    }
 334
 335    for (i = 0 ; i < Elements(default_extensions) ; i++) {
 336       if (_mesa_strcmp(default_extensions[i].name, name) == 0) {
 337          if (default_extensions[i].flag_offset) {
 338             GLboolean *enabled = base + default_extensions[i].flag_offset;
 339             *enabled = state;
 340          }
 341          return;
 342       }
 343    }
 344    _mesa_problem(ctx, "Trying to enable unknown extension: %s", name);
 345 }
 346
 347
 348 /**
 349  * Enable the named extension.
 350  * Typically called by drivers.
 351  */
 352 void
 353 _mesa_enable_extension( GLcontext *ctx, const char *name )
 354 {
 355    set_extension(ctx, name, GL_TRUE);
 356 }
 357
 358
 359 /**
 360  * Disable the named extension.
 361  * XXX is this really needed???
 362  */
 363 void
 364 _mesa_disable_extension( GLcontext *ctx, const char *name )
 365 {
 366    set_extension(ctx, name, GL_FALSE);
 367 }
 368
 369
 370 /**
 371  * Test if the named extension is enabled in this context.
 372  */
 373 GLboolean
 374 _mesa_extension_is_enabled( GLcontext *ctx, const char *name )
 375 {
 376    const GLboolean *base = (const GLboolean *) &ctx->Extensions;
 377    GLuint i;
 378
 379    for (i = 0 ; i < Elements(default_extensions) ; i++) {
 380       if (_mesa_strcmp(default_extensions[i].name, name) == 0) {
 381          if (!default_extensions[i].flag_offset)
 382             return GL_TRUE;
 383          return *(base + default_extensions[i].flag_offset);
 384       }
 385    }
 386    return GL_FALSE;
 387 }
 388
 389
 390 /**
 391  * Run through the default_extensions array above and set the
 392  * ctx->Extensions.ARB/EXT_* flags accordingly.
 393  * To be called during context initialization.
 394  */
 395 void
 396 _mesa_init_extensions( GLcontext *ctx )
 397 {
 398    GLboolean *base = (GLboolean *) &ctx->Extensions;
 399    GLuint i;
 400
 401    for (i = 0 ; i < Elements(default_extensions) ; i++) {
 402       if (default_extensions[i].enabled &&
 403           default_extensions[i].flag_offset) {
 404          *(base + default_extensions[i].flag_offset) = GL_TRUE;
 405       }
 406    }
 407 }
 408
 409
 410 /**
 411  * Construct the GL_EXTENSIONS string.  Called the first time that
 412  * glGetString(GL_EXTENSIONS) is called.
 413  */
 414 GLubyte *
 415 _mesa_make_extension_string( GLcontext *ctx )
 416 {
 417    const GLboolean *base = (const GLboolean *) &ctx->Extensions;
 418    GLuint extStrLen = 0;
 419    GLubyte *s;
 420    GLuint i;
 421
 422    /* first, compute length of the extension string */
 423    for (i = 0 ; i < Elements(default_extensions) ; i++) {
 424       if (!default_extensions[i].flag_offset ||
 425           *(base + default_extensions[i].flag_offset)) {
 426          extStrLen += _mesa_strlen(default_extensions[i].name) + 1;
 427       }
 428    }
 429    s = (GLubyte *) _mesa_malloc(extStrLen);
 430
 431    /* second, build the extension string */
 432    extStrLen = 0;
 433    for (i = 0 ; i < Elements(default_extensions) ; i++) {
 434       if (!default_extensions[i].flag_offset ||
 435           *(base + default_extensions[i].flag_offset)) {
 436          GLuint len = _mesa_strlen(default_extensions[i].name);
 437          _mesa_memcpy(s + extStrLen, default_extensions[i].name, len);
 438          extStrLen += len;
 439          s[extStrLen] = (GLubyte) ' ';
 440          extStrLen++;
 441       }
 442    }
 443    ASSERT(extStrLen > 0);
 444
 445    s[extStrLen - 1] = 0;
 446
 447    return s;
 448 }