summaryrefslogtreecommitdiffstats
path: root/src/mesa/main/imports.c
blob: c46e5beb918d072e35c444785e08b691f2da950c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
/**
 * \file imports.c
 * Standard C library function wrappers.
 * 
 * Imports are services which the device driver or window system or
 * operating system provides to the core renderer.  The core renderer (Mesa)
 * will call these functions in order to do memory allocation, simple I/O,
 * etc.
 *
 * Some drivers will want to override/replace this file with something
 * specialized, but that'll be rare.
 *
 * Eventually, I want to move roll the glheader.h file into this.
 *
 * \todo Functions still needed:
 * - scanf
 * - qsort
 * - rand and RAND_MAX
 */

/*
 * Mesa 3-D graphics library
 * Version:  7.1
 *
 * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL 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.
 */



#include "imports.h"
#include "context.h"
#include "version.h"


#define MAXSTRING 4000  /* for vsnprintf() */

#ifdef WIN32
#define vsnprintf _vsnprintf
#elif defined(__IBMC__) || defined(__IBMCPP__) || ( defined(__VMS) && __CRTL_VER < 70312000 )
extern int vsnprintf(char *str, size_t count, const char *fmt, va_list arg);
#ifdef __VMS
#include "vsnprintf.c"
#endif
#endif

/**********************************************************************/
/** \name Memory */
/*@{*/

/** Wrapper around malloc() */
void *
_mesa_malloc(size_t bytes)
{
   return malloc(bytes);
}

/** Wrapper around calloc() */
void *
_mesa_calloc(size_t bytes)
{
   return calloc(1, bytes);
}

/** Wrapper around free() */
void
_mesa_free(void *ptr)
{
   free(ptr);
}

/**
 * Allocate aligned memory.
 *
 * \param bytes number of bytes to allocate.
 * \param alignment alignment (must be greater than zero).
 * 
 * Allocates extra memory to accommodate rounding up the address for
 * alignment and to record the real malloc address.
 *
 * \sa _mesa_align_free().
 */
void *
_mesa_align_malloc(size_t bytes, unsigned long alignment)
{
#if defined(HAVE_POSIX_MEMALIGN)
   void *mem;

   (void) posix_memalign(& mem, alignment, bytes);
   return mem;
#else
   uintptr_t ptr, buf;

   ASSERT( alignment > 0 );

   ptr = (uintptr_t) _mesa_malloc(bytes + alignment + sizeof(void *));
   if (!ptr)
      return NULL;

   buf = (ptr + alignment + sizeof(void *)) & ~(uintptr_t)(alignment - 1);
   *(uintptr_t *)(buf - sizeof(void *)) = ptr;

#ifdef DEBUG
   /* mark the non-aligned area */
   while ( ptr < buf - sizeof(void *) ) {
      *(unsigned long *)ptr = 0xcdcdcdcd;
      ptr += sizeof(unsigned long);
   }
#endif

   return (void *) buf;
#endif /* defined(HAVE_POSIX_MEMALIGN) */
}

/**
 * Same as _mesa_align_malloc(), but using _mesa_calloc() instead of
 * _mesa_malloc()
 */
void *
_mesa_align_calloc(size_t bytes, unsigned long alignment)
{
#if defined(HAVE_POSIX_MEMALIGN)
   void *mem;
   
   mem = _mesa_align_malloc(bytes, alignment);
   if (mem != NULL) {
      (void) memset(mem, 0, bytes);
   }

   return mem;
#else
   uintptr_t ptr, buf;

   ASSERT( alignment > 0 );

   ptr = (uintptr_t) _mesa_calloc(bytes + alignment + sizeof(void *));
   if (!ptr)
      return NULL;

   buf = (ptr + alignment + sizeof(void *)) & ~(uintptr_t)(alignment - 1);
   *(uintptr_t *)(buf - sizeof(void *)) = ptr;

#ifdef DEBUG
   /* mark the non-aligned area */
   while ( ptr < buf - sizeof(void *) ) {
      *(unsigned long *)ptr = 0xcdcdcdcd;
      ptr += sizeof(unsigned long);
   }
#endif

   return (void *)buf;
#endif /* defined(HAVE_POSIX_MEMALIGN) */
}

/**
 * Free memory which was allocated with either _mesa_align_malloc()
 * or _mesa_align_calloc().
 * \param ptr pointer to the memory to be freed.
 * The actual address to free is stored in the word immediately before the
 * address the client sees.
 */
void
_mesa_align_free(void *ptr)
{
#if defined(HAVE_POSIX_MEMALIGN)
   free(ptr);
#else
   void **cubbyHole = (void **) ((char *) ptr - sizeof(void *));
   void *realAddr = *cubbyHole;
   _mesa_free(realAddr);
#endif /* defined(HAVE_POSIX_MEMALIGN) */
}

/**
 * Reallocate memory, with alignment.
 */
void *
_mesa_align_realloc(void *oldBuffer, size_t oldSize, size_t newSize,
                    unsigned long alignment)
{
   const size_t copySize = (oldSize < newSize) ? oldSize : newSize;
   void *newBuf = _mesa_align_malloc(newSize, alignment);
   if (newBuf && oldBuffer && copySize > 0) {
      _mesa_memcpy(newBuf, oldBuffer, copySize);
   }
   if (oldBuffer)
      _mesa_align_free(oldBuffer);
   return newBuf;
}



/** Reallocate memory */
void *
_mesa_realloc(void *oldBuffer, size_t oldSize, size_t newSize)
{
   const size_t copySize = (oldSize < newSize) ? oldSize : newSize;
   void *newBuffer = _mesa_malloc(newSize);
   if (newBuffer && oldBuffer && copySize > 0)
      _mesa_memcpy(newBuffer, oldBuffer, copySize);
   if (oldBuffer)
      _mesa_free(oldBuffer);
   return newBuffer;
}

/** memcpy wrapper */
void *
_mesa_memcpy(void *dest, const void *src, size_t n)
{
#if defined(SUNOS4)
   return memcpy((char *) dest, (char *) src, (int) n);
#else
   return memcpy(dest, src, n);
#endif
}

/** Wrapper around memset() */
void
_mesa_memset( void *dst, int val, size_t n )
{
#if defined(SUNOS4)
   memset( (char *) dst, (int) val, (int) n );
#else
   memset(dst, val, n);
#endif
}

/**
 * Fill memory with a constant 16bit word.
 * \param dst destination pointer.
 * \param val value.
 * \param n number of words.
 */
void
_mesa_memset16( unsigned short *dst, unsigned short val, size_t n )
{
   while (n-- > 0)
      *dst++ = val;
}

/** Wrapper around either memset() or bzero() */
void
_mesa_bzero( void *dst, size_t n )
{
#if defined(__FreeBSD__)
   bzero( dst, n );
#else
   memset( dst, 0, n );
#endif
}

/** Wrapper around memcmp() */
int
_mesa_memcmp( const void *s1, const void *s2, size_t n )
{
#if defined(SUNOS4)
   return memcmp( (char *) s1, (char *) s2, (int) n );
#else
   return memcmp(s1, s2, n);
#endif
}

/*@}*/


/**********************************************************************/
/** \name Math */
/*@{*/

/** Wrapper around sin() */
double
_mesa_sin(double a)
{
   return sin(a);
}

/** Single precision wrapper around sin() */
float
_mesa_sinf(float a)
{
   return (float) sin((double) a);
}

/** Wrapper around cos() */
double
_mesa_cos(double a)
{
   return cos(a);
}

/** Single precision wrapper around asin() */
float
_mesa_asinf(float x)
{
   return (float) asin((double) x);
}

/** Single precision wrapper around atan() */
float
_mesa_atanf(float x)
{
   return (float) atan((double) x);
}

/** Wrapper around sqrt() */
double
_mesa_sqrtd(double x)
{
   return sqrt(x);
}


/*
 * A High Speed, Low Precision Square Root
 * by Paul Lalonde and Robert Dawson
 * from "Graphics Gems", Academic Press, 1990
 *
 * SPARC implementation of a fast square root by table
 * lookup.
 * SPARC floating point format is as follows:
 *
 * BIT 31 	30 	23 	22 	0
 *     sign	exponent	mantissa
 */
static short sqrttab[0x100];    /* declare table of square roots */

void
_mesa_init_sqrt_table(void)
{
#if defined(USE_IEEE) && !defined(DEBUG)
   unsigned short i;
   fi_type fi;     /* to access the bits of a float in  C quickly  */
                   /* we use a union defined in glheader.h         */

   for(i=0; i<= 0x7f; i++) {
      fi.i = 0;

      /*
       * Build a float with the bit pattern i as mantissa
       * and an exponent of 0, stored as 127
       */

      fi.i = (i << 16) | (127 << 23);
      fi.f = _mesa_sqrtd(fi.f);

      /*
       * Take the square root then strip the first 7 bits of
       * the mantissa into the table
       */

      sqrttab[i] = (fi.i & 0x7fffff) >> 16;

      /*
       * Repeat the process, this time with an exponent of
       * 1, stored as 128
       */

      fi.i = 0;
      fi.i = (i << 16) | (128 << 23);
      fi.f = sqrt(fi.f);
      sqrttab[i+0x80] = (fi.i & 0x7fffff) >> 16;
   }
#else
   (void) sqrttab;  /* silence compiler warnings */
#endif /*HAVE_FAST_MATH*/
}


/**
 * Single precision square root.
 */
float
_mesa_sqrtf( float x )
{
#if defined(USE_IEEE) && !defined(DEBUG)
   fi_type num;
                                /* to access the bits of a float in C
                                 * we use a union from glheader.h     */

   short e;                     /* the exponent */
   if (x == 0.0F) return 0.0F;  /* check for square root of 0 */
   num.f = x;
   e = (num.i >> 23) - 127;     /* get the exponent - on a SPARC the */
                                /* exponent is stored with 127 added */
   num.i &= 0x7fffff;           /* leave only the mantissa */
   if (e & 0x01) num.i |= 0x800000;
                                /* the exponent is odd so we have to */
                                /* look it up in the second half of  */
                                /* the lookup table, so we set the   */
                                /* high bit                                */
   e >>= 1;                     /* divide the exponent by two */
                                /* note that in C the shift */
                                /* operators are sign preserving */
                                /* for signed operands */
   /* Do the table lookup, based on the quaternary mantissa,
    * then reconstruct the result back into a float
    */
   num.i = ((sqrttab[num.i >> 16]) << 16) | ((e + 127) << 23);

   return num.f;
#else
   return (float) _mesa_sqrtd((double) x);
#endif
}


/**
 inv_sqrt - A single precision 1/sqrt routine for IEEE format floats.
 written by Josh Vanderhoof, based on newsgroup posts by James Van Buskirk
 and Vesa Karvonen.
*/
float
_mesa_inv_sqrtf(float n)
{
#if defined(USE_IEEE) && !defined(DEBUG)
        float r0, x0, y0;
        float r1, x1, y1;
        float r2, x2, y2;
#if 0 /* not used, see below -BP */
        float r3, x3, y3;
#endif
        union { float f; unsigned int i; } u;
        unsigned int magic;

        /*
         Exponent part of the magic number -

         We want to:
         1. subtract the bias from the exponent,
         2. negate it
         3. divide by two (rounding towards -inf)
         4. add the bias back

         Which is the same as subtracting the exponent from 381 and dividing
         by 2.

         floor(-(x - 127) / 2) + 127 = floor((381 - x) / 2)
        */

        magic = 381 << 23;

        /*
         Significand part of magic number -

         With the current magic number, "(magic - u.i) >> 1" will give you:

         for 1 <= u.f <= 2: 1.25 - u.f / 4
         for 2 <= u.f <= 4: 1.00 - u.f / 8

         This isn't a bad approximation of 1/sqrt.  The maximum difference from
         1/sqrt will be around .06.  After three Newton-Raphson iterations, the
         maximum difference is less than 4.5e-8.  (Which is actually close
         enough to make the following bias academic...)

         To get a better approximation you can add a bias to the magic
         number.  For example, if you subtract 1/2 of the maximum difference in
         the first approximation (.03), you will get the following function:

         for 1 <= u.f <= 2:    1.22 - u.f / 4
         for 2 <= u.f <= 3.76: 0.97 - u.f / 8
         for 3.76 <= u.f <= 4: 0.72 - u.f / 16
         (The 3.76 to 4 range is where the result is < .5.)

         This is the closest possible initial approximation, but with a maximum
         error of 8e-11 after three NR iterations, it is still not perfect.  If
         you subtract 0.0332281 instead of .03, the maximum error will be
         2.5e-11 after three NR iterations, which should be about as close as
         is possible.

         for 1 <= u.f <= 2:    1.2167719 - u.f / 4
         for 2 <= u.f <= 3.73: 0.9667719 - u.f / 8
         for 3.73 <= u.f <= 4: 0.7167719 - u.f / 16

        */

        magic -= (int)(0.0332281 * (1 << 25));

        u.f = n;
        u.i = (magic - u.i) >> 1;

        /*
         Instead of Newton-Raphson, we use Goldschmidt's algorithm, which
         allows more parallelism.  From what I understand, the parallelism
         comes at the cost of less precision, because it lets error
         accumulate across iterations.
        */
        x0 = 1.0f;
        y0 = 0.5f * n;
        r0 = u.f;

        x1 = x0 * r0;
        y1 = y0 * r0 * r0;
        r1 = 1.5f - y1;

        x2 = x1 * r1;
        y2 = y1 * r1 * r1;
        r2 = 1.5f - y2;

#if 1
        return x2 * r2;  /* we can stop here, and be conformant -BP */
#else
        x3 = x2 * r2;
        y3 = y2 * r2 * r2;
        r3 = 1.5f - y3;

        return x3 * r3;
#endif
#else
        return (float) (1.0 / sqrt(n));
#endif
}


/** Wrapper around pow() */
double
_mesa_pow(double x, double y)
{
   return pow(x, y);
}


/**
 * Find the first bit set in a word.
 */
int
_mesa_ffs(int i)
{
#if (defined(_WIN32) && !defined(__MINGW32__) ) || defined(__IBMC__) || defined(__IBMCPP__)
   register int bit = 1;
   if ((i & 0xffff) == 0) {
      bit += 16;
      i >>= 16;
   }
   if ((i & 0xff) == 0) {
      bit += 8;
      i >>= 8;
   }
   if ((i & 0xf) == 0) {
      bit += 4;
      i >>= 4;
   }
   if ((i & 0x3) == 0) {
      bit += 2;
      i >>= 2;
   }
   return (i) ? (bit + ((i + 1) & 0x01)) : 0;
#else
   return ffs(i);
#endif
}


/**
 * Find position of first bit set in given value.
 * XXX Warning: this function can only be used on 64-bit systems!
 * \return  position of least-significant bit set, starting at 1, return zero
 *          if no bits set.
 */
int
#ifdef __MINGW32__
_mesa_ffsll(long val)
#else
_mesa_ffsll(long long val)
#endif
{
#ifdef ffsll
   return ffsll(val);
#else
   int bit;

   assert(sizeof(val) == 8);

   bit = _mesa_ffs(val);
   if (bit != 0)
      return bit;

   bit = _mesa_ffs(val >> 32);
   if (bit != 0)
      return 32 + bit;

   return 0;
#endif
}


/**
 * Return number of bits set in given GLuint.
 */
unsigned int
_mesa_bitcount(unsigned int n)
{
   unsigned int bits;
   for (bits = 0; n > 0; n = n >> 1) {
      bits += (n & 1);
   }
   return bits;
}


/**
 * Convert a 4-byte float to a 2-byte half float.
 * Based on code from:
 * http://www.opengl.org/discussion_boards/ubb/Forum3/HTML/008786.html
 */
GLhalfARB
_mesa_float_to_half(float val)
{
   const int flt = *((int *) (void *) &val);
   const int flt_m = flt & 0x7fffff;
   const int flt_e = (flt >> 23) & 0xff;
   const int flt_s = (flt >> 31) & 0x1;
   int s, e, m = 0;
   GLhalfARB result;
   
   /* sign bit */
   s = flt_s;

   /* handle special cases */
   if ((flt_e == 0) && (flt_m == 0)) {
      /* zero */
      /* m = 0; - already set */
      e = 0;
   }
   else if ((flt_e == 0) && (flt_m != 0)) {
      /* denorm -- denorm float maps to 0 half */
      /* m = 0; - already set */
      e = 0;
   }
   else if ((flt_e == 0xff) && (flt_m == 0)) {
      /* infinity */
      /* m = 0; - already set */
      e = 31;
   }
   else if ((flt_e == 0xff) && (flt_m != 0)) {
      /* NaN */
      m = 1;
      e = 31;
   }
   else {
      /* regular number */
      const int new_exp = flt_e - 127;
      if (new_exp < -24) {
         /* this maps to 0 */
         /* m = 0; - already set */
         e = 0;
      }
      else if (new_exp < -14) {
         /* this maps to a denorm */
         unsigned int exp_val = (unsigned int) (-14 - new_exp); /* 2^-exp_val*/
         e = 0;
         switch (exp_val) {
            case 0:
               _mesa_warning(NULL,
                   "float_to_half: logical error in denorm creation!\n");
               /* m = 0; - already set */
               break;
            case 1: m = 512 + (flt_m >> 14); break;
            case 2: m = 256 + (flt_m >> 15); break;
            case 3: m = 128 + (flt_m >> 16); break;
            case 4: m = 64 + (flt_m >> 17); break;
            case 5: m = 32 + (flt_m >> 18); break;
            case 6: m = 16 + (flt_m >> 19); break;
            case 7: m = 8 + (flt_m >> 20); break;
            case 8: m = 4 + (flt_m >> 21); break;
            case 9: m = 2 + (flt_m >> 22); break;
            case 10: m = 1; break;
         }
      }
      else if (new_exp > 15) {
         /* map this value to infinity */
         /* m = 0; - already set */
         e = 31;
      }
      else {
         /* regular */
         e = new_exp + 15;
         m = flt_m >> 13;
      }
   }

   result = (s << 15) | (e << 10) | m;
   return result;
}


/**
 * Convert a 2-byte half float to a 4-byte float.
 * Based on code from:
 * http://www.opengl.org/discussion_boards/ubb/Forum3/HTML/008786.html
 */
float
_mesa_half_to_float(GLhalfARB val)
{
   /* XXX could also use a 64K-entry lookup table */
   const int m = val & 0x3ff;
   const int e = (val >> 10) & 0x1f;
   const int s = (val >> 15) & 0x1;
   int flt_m, flt_e, flt_s, flt;
   float result;

   /* sign bit */
   flt_s = s;

   /* handle special cases */
   if ((e == 0) && (m == 0)) {
      /* zero */
      flt_m = 0;
      flt_e = 0;
   }
   else if ((e == 0) && (m != 0)) {
      /* denorm -- denorm half will fit in non-denorm single */
      const float half_denorm = 1.0f / 16384.0f; /* 2^-14 */
      float mantissa = ((float) (m)) / 1024.0f;
      float sign = s ? -1.0f : 1.0f;
      return sign * mantissa * half_denorm;
   }
   else if ((e == 31) && (m == 0)) {
      /* infinity */
      flt_e = 0xff;
      flt_m = 0;
   }
   else if ((e == 31) && (m != 0)) {
      /* NaN */
      flt_e = 0xff;
      flt_m = 1;
   }
   else {
      /* regular */
      flt_e = e + 112;
      flt_m = m << 13;
   }

   flt = (flt_s << 31) | (flt_e << 23) | flt_m;
   result = *((float *) (void *) &flt);
   return result;
}

/*@}*/


/**********************************************************************/
/** \name Sort & Search */
/*@{*/

/**
 * Wrapper for bsearch().
 */
void *
_mesa_bsearch( const void *key, const void *base, size_t nmemb, size_t size, 
               int (*compar)(const void *, const void *) )
{
#if defined(_WIN32_WCE)
   void *mid;
   int cmp;
   while (nmemb) {
      nmemb >>= 1;
      mid = (char *)base + nmemb * size;
      cmp = (*compar)(key, mid);
      if (cmp == 0)
	 return mid;
      if (cmp > 0) {
	 base = (char *)mid + size;
	 --nmemb;
      }
   }
   return NULL;
#else
   return bsearch(key, base, nmemb, size, compar);
#endif
}

/*@}*/


/**********************************************************************/
/** \name Environment vars */
/*@{*/

/**
 * Wrapper for getenv().
 */
char *
_mesa_getenv( const char *var )
{
#if defined(_XBOX) || defined(_WIN32_WCE)
   return NULL;
#else
   return getenv(var);
#endif
}

/*@}*/


/**********************************************************************/
/** \name String */
/*@{*/

/** Wrapper around strstr() */
char *
_mesa_strstr( const char *haystack, const char *needle )
{
   return strstr(haystack, needle);
}

/** Wrapper around strncat() */
char *
_mesa_strncat( char *dest, const char *src, size_t n )
{
   return strncat(dest, src, n);
}

/** Wrapper around strcpy() */
char *
_mesa_strcpy( char *dest, const char *src )
{
   return strcpy(dest, src);
}

/** Wrapper around strncpy() */
char *
_mesa_strncpy( char *dest, const char *src, size_t n )
{
   return strncpy(dest, src, n);
}

/** Wrapper around strlen() */
size_t
_mesa_strlen( const char *s )
{
   return strlen(s);
}

/** Wrapper around strcmp() */
int
_mesa_strcmp( const char *s1, const char *s2 )
{
   return strcmp(s1, s2);
}

/** Wrapper around strncmp() */
int
_mesa_strncmp( const char *s1, const char *s2, size_t n )
{
   return strncmp(s1, s2, n);
}

/**
 * Implemented using _mesa_malloc() and _mesa_strcpy.
 * Note that NULL is handled accordingly.
 */
char *
_mesa_strdup( const char *s )
{
   if (s) {
      size_t l = _mesa_strlen(s);
      char *s2 = (char *) _mesa_malloc(l + 1);
      if (s2)
         _mesa_strcpy(s2, s);
      return s2;
   }
   else {
      return NULL;
   }
}

/** Wrapper around atoi() */
int
_mesa_atoi(const char *s)
{
   return atoi(s);
}

/** Wrapper around strtod() */
double
_mesa_strtod( const char *s, char **end )
{
   return strtod(s, end);
}

/*@}*/


/**********************************************************************/
/** \name I/O */
/*@{*/

/** Wrapper around vsprintf() */
int
_mesa_sprintf( char *str, const char *fmt, ... )
{
   int r;
   va_list args;
   va_start( args, fmt );  
   r = vsprintf( str, fmt, args );
   va_end( args );
   return r;
}

/** Wrapper around printf(), using vsprintf() for the formatting. */
void
_mesa_printf( const char *fmtString, ... )
{
   va_list args;
   va_start( args, fmtString );  
   vfprintf(stderr, fmtString, args);
   va_end( args );
}

/** Wrapper around vsprintf() */
int
_mesa_vsprintf( char *str, const char *fmt, va_list args )
{
   return vsprintf( str, fmt, args );
}

/*@}*/


/**********************************************************************/
/** \name Diagnostics */
/*@{*/

/**
 * Report a warning (a recoverable error condition) to stderr if
 * either DEBUG is defined or the MESA_DEBUG env var is set.
 *
 * \param ctx GL context.
 * \param fmtString printf() alike format string.
 */
void
_mesa_warning( GLcontext *ctx, const char *fmtString, ... )
{
   GLboolean debug;
   char str[MAXSTRING];
   va_list args;
   (void) ctx;
   va_start( args, fmtString );  
   (void) vsnprintf( str, MAXSTRING, fmtString, args );
   va_end( args );
#ifdef DEBUG
   debug = GL_TRUE; /* always print warning */
#else
   debug = _mesa_getenv("MESA_DEBUG") ? GL_TRUE : GL_FALSE;
#endif
   if (debug) {
      fprintf(stderr, "Mesa warning: %s\n", str);
   }
}

/**
 * Report an internla implementation problem.
 * Prints the message to stderr via fprintf().
 *
 * \param ctx GL context.
 * \param s problem description string.
 */
void
_mesa_problem( const GLcontext *ctx, const char *fmtString, ... )
{
   va_list args;
   char str[MAXSTRING];
   (void) ctx;

   va_start( args, fmtString );  
   vsnprintf( str, MAXSTRING, fmtString, args );
   va_end( args );

   fprintf(stderr, "Mesa %s implementation error: %s\n", MESA_VERSION_STRING, str);
   fprintf(stderr, "Please report at bugzilla.freedesktop.org\n");
}

/**
 * Record an OpenGL state error.  These usually occur when the users
 * passes invalid parameters to a GL function.
 *
 * If debugging is enabled (either at compile-time via the DEBUG macro, or
 * run-time via the MESA_DEBUG environment variable), report the error with
 * _mesa_debug().
 * 
 * \param ctx the GL context.
 * \param error the error value.
 * \param fmtString printf() style format string, followed by optional args
 */
void
_mesa_error( GLcontext *ctx, GLenum error, const char *fmtString, ... )
{
   const char *debugEnv;
   GLboolean debug;

   debugEnv = _mesa_getenv("MESA_DEBUG");

#ifdef DEBUG
   if (debugEnv && _mesa_strstr(debugEnv, "silent"))
      debug = GL_FALSE;
   else
      debug = GL_TRUE;
#else
   if (debugEnv)
      debug = GL_TRUE;
   else
      debug = GL_FALSE;
#endif

   if (debug) {
      va_list args;
      char where[MAXSTRING];
      const char *errstr;

      va_start( args, fmtString );  
      vsnprintf( where, MAXSTRING, fmtString, args );
      va_end( args );

      switch (error) {
	 case GL_NO_ERROR:
	    errstr = "GL_NO_ERROR";
	    break;
	 case GL_INVALID_VALUE:
	    errstr = "GL_INVALID_VALUE";
	    break;
	 case GL_INVALID_ENUM:
	    errstr = "GL_INVALID_ENUM";
	    break;
	 case GL_INVALID_OPERATION:
	    errstr = "GL_INVALID_OPERATION";
	    break;
	 case GL_STACK_OVERFLOW:
	    errstr = "GL_STACK_OVERFLOW";
	    break;
	 case GL_STACK_UNDERFLOW:
	    errstr = "GL_STACK_UNDERFLOW";
	    break;
	 case GL_OUT_OF_MEMORY:
	    errstr = "GL_OUT_OF_MEMORY";
	    break;
         case GL_TABLE_TOO_LARGE:
            errstr = "GL_TABLE_TOO_LARGE";
            break;
         case GL_INVALID_FRAMEBUFFER_OPERATION_EXT:
            errstr = "GL_INVALID_FRAMEBUFFER_OPERATION";
            break;
	 default:
	    errstr = "unknown";
	    break;
      }
      _mesa_debug(ctx, "User error: %s in %s\n", errstr, where);
   }

   _mesa_record_error(ctx, error);
}  

/**
 * Report debug information.  Print error message to stderr via fprintf().
 * No-op if DEBUG mode not enabled.
 * 
 * \param ctx GL context.
 * \param fmtString printf()-style format string, followed by optional args.
 */
void
_mesa_debug( const GLcontext *ctx, const char *fmtString, ... )
{
#ifdef DEBUG
   char s[MAXSTRING];
   va_list args;
   va_start(args, fmtString);
   vsnprintf(s, MAXSTRING, fmtString, args);
   va_end(args);
   fprintf(stderr, "Mesa: %s", s);
#endif /* DEBUG */
   (void) ctx;
   (void) fmtString;
}

/*@}*/


/**
 * Wrapper for exit().
 */
void
_mesa_exit( int status )
{
   exit(status);
}