unofficial mirror of emacs-devel@gnu.org 
 help / color / mirror / code / Atom feed
blob 330fdf4324c0fd09220dbf4127ca31a123e25baa 16092 bytes (raw)
name: src/bignum.c 	 # note: path name is non-authoritative(*)

  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
 
/* Big numbers for Emacs.

Copyright 2018-2024 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

#include "bignum.h"
#include "lisp.h"

#include <math.h>
#include <stdlib.h>

#include "igc.h"

/* mpz global temporaries.  Making them global saves the trouble of
   properly using mpz_init and mpz_clear on temporaries even when
   storage is exhausted.  Admittedly this is not ideal.  An mpz value
   in a temporary is made permanent by mpz_swapping it with a bignum's
   value.  Although typically at most two temporaries are needed,
   rounddiv_q and rounding_driver both need four and time_arith needs
   five.  */

mpz_t mpz[5] = { 0, };

static void *
xmalloc_for_gmp (size_t size)
{
  return igc_alloc_bytes (size);
}

static void *
xrealloc_for_gmp (void *ptr, size_t ignore, size_t size)
{
  if (size > ignore)
    {
      void *ret = xmalloc_for_gmp (size);
      memcpy (ret, ptr, ignore);
      return ret;
    }
  return ptr;
}

static void
xfree_for_gmp (void *ptr, size_t ignore)
{
}

void
init_bignum (void)
{
  eassert (mp_bits_per_limb == GMP_NUMB_BITS);
  integer_width = 1 << 16;

  /* FIXME: The Info node `(gmp) Custom Allocation' states: "No error
     return is allowed from any of these functions, if they return
     then they must have performed the specified operation. [...]
     There's currently no defined way for the allocation functions to
     recover from an error such as out of memory, they must terminate
     program execution.  A 'longjmp' or throwing a C++ exception will
     have undefined results."  But xmalloc and xrealloc do call
     'longjmp'.  */
  mp_set_memory_functions (xmalloc_for_gmp, xrealloc_for_gmp, xfree_for_gmp);

  for (int i = 0; i < ARRAYELTS (mpz); i++)
    igc_root_create_exact_ptr (&mpz[i][0]._mp_d);
  for (int i = 0; i < ARRAYELTS (mpz); i++)
    mpz_init (mpz[i]);
}

/* Return the value of the Lisp bignum N, as a double.  */
double
bignum_to_double (Lisp_Object n)
{
  return mpz_get_d_rounded (*xbignum_val (n));
}

/* Return D, converted to a Lisp integer.  Discard any fraction.
   Signal an error if D cannot be converted.  */
Lisp_Object
double_to_integer (double d)
{
  if (!isfinite (d))
    overflow_error ();
  mpz_set_d (mpz[0], d);
  return make_integer_mpz ();
}

/* Return a Lisp integer equal to mpz[0], which has BITS bits and which
   must not be in fixnum range.  Set mpz[0] to a junk value.  */
static Lisp_Object
make_bignum_bits (size_t bits)
{
  /* The documentation says integer-width should be nonnegative, so
     comparing it to BITS works even though BITS is unsigned.  Treat
     integer-width as if it were at least twice the machine integer width,
     so that timefns.c can safely use bignums for double-precision
     timestamps.  */
  if (integer_width < bits && 2 * max (INTMAX_WIDTH, UINTMAX_WIDTH) < bits)
    overflow_error ();

  struct Lisp_Bignum *b = ALLOCATE_PLAIN_PSEUDOVECTOR (struct Lisp_Bignum,
						       PVEC_BIGNUM);
  mpz_init (b->value);
  mpz_swap (b->value, mpz[0]);
  return make_lisp_ptr (b, Lisp_Vectorlike);
}

/* Return a Lisp integer equal to mpz[0], which must not be in fixnum range.
   Set mpz[0] to a junk value.  */
static Lisp_Object
make_bignum (void)
{
  return make_bignum_bits (mpz_sizeinbase (mpz[0], 2));
}

/* Return a Lisp integer equal to N, which must not be in fixnum range.  */
Lisp_Object
make_bigint (intmax_t n)
{
  eassert (FIXNUM_OVERFLOW_P (n));
  mpz_set_intmax (mpz[0], n);
  return make_bignum ();
}
Lisp_Object
make_biguint (uintmax_t n)
{
  eassert (FIXNUM_OVERFLOW_P (n));
  mpz_set_uintmax (mpz[0], n);
  return make_bignum ();
}

/* Return a Lisp integer equal to -N, which must not be in fixnum range.  */
Lisp_Object
make_neg_biguint (uintmax_t n)
{
  eassert (-MOST_NEGATIVE_FIXNUM < n);
  mpz_set_uintmax (mpz[0], n);
  mpz_neg (mpz[0], mpz[0]);
  return make_bignum ();
}

/* Return a Lisp integer with value taken from mpz[0].
   Set mpz[0] to a junk value.  */
Lisp_Object
make_integer_mpz (void)
{
  size_t bits = mpz_sizeinbase (mpz[0], 2);

  if (bits <= FIXNUM_BITS)
    {
      EMACS_INT v = 0;
      int i = 0, shift = 0;

      do
	{
	  EMACS_INT limb = mpz_getlimbn (mpz[0], i++);
	  v += limb << shift;
	  shift += GMP_NUMB_BITS;
	}
      while (shift < bits);

      if (mpz_sgn (mpz[0]) < 0)
	v = -v;

      if (!FIXNUM_OVERFLOW_P (v))
	return make_fixnum (v);
    }

  return make_bignum_bits (bits);
}

/* Set RESULT to V.  This code is for when intmax_t is wider than long.  */
void
mpz_set_intmax_slow (mpz_t result, intmax_t v)
{
  int maxlimbs = (INTMAX_WIDTH + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS;
  mp_limb_t *limb = mpz_limbs_write (result, maxlimbs);
  int n = 0;
  uintmax_t u = v;
  bool negative = v < 0;
  if (negative)
    {
      uintmax_t two = 2;
      u = -u & ((two << (UINTMAX_WIDTH - 1)) - 1);
    }

  do
    {
      limb[n++] = u;
      u = GMP_NUMB_BITS < UINTMAX_WIDTH ? u >> GMP_NUMB_BITS : 0;
    }
  while (u != 0);

  mpz_limbs_finish (result, negative ? -n : n);
}
void
mpz_set_uintmax_slow (mpz_t result, uintmax_t v)
{
  int maxlimbs = (UINTMAX_WIDTH + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS;
  mp_limb_t *limb = mpz_limbs_write (result, maxlimbs);
  int n = 0;

  do
    {
      limb[n++] = v;
      v = GMP_NUMB_BITS < INTMAX_WIDTH ? v >> GMP_NUMB_BITS : 0;
    }
  while (v != 0);

  mpz_limbs_finish (result, n);
}

/* If Z fits into *PI, store its value there and return true.
   Return false otherwise.  */
bool
mpz_to_intmax (mpz_t const z, intmax_t *pi)
{
  ptrdiff_t bits = mpz_sizeinbase (z, 2);
  bool negative = mpz_sgn (z) < 0;

  if (bits < INTMAX_WIDTH)
    {
      intmax_t v = 0;
      int i = 0, shift = 0;

      do
	{
	  intmax_t limb = mpz_getlimbn (z, i++);
	  v += limb << shift;
	  shift += GMP_NUMB_BITS;
	}
      while (shift < bits);

      *pi = negative ? -v : v;
      return true;
    }
  if (bits == INTMAX_WIDTH && INTMAX_MIN < -INTMAX_MAX && negative
      && mpz_scan1 (z, 0) == INTMAX_WIDTH - 1)
    {
      *pi = INTMAX_MIN;
      return true;
    }
  return false;
}
bool
mpz_to_uintmax (mpz_t const z, uintmax_t *pi)
{
  if (mpz_sgn (z) < 0)
    return false;
  ptrdiff_t bits = mpz_sizeinbase (z, 2);
  if (UINTMAX_WIDTH < bits)
    return false;

  uintmax_t v = 0;
  int i = 0, shift = 0;

  do
    {
      uintmax_t limb = mpz_getlimbn (z, i++);
      v += limb << shift;
      shift += GMP_NUMB_BITS;
    }
  while (shift < bits);

  *pi = v;
  return true;
}

/* Return the value of the bignum X if it fits, 0 otherwise.
   A bignum cannot be zero, so 0 indicates failure reliably.  */
intmax_t
bignum_to_intmax (Lisp_Object x)
{
  intmax_t i;
  return mpz_to_intmax (*xbignum_val (x), &i) ? i : 0;
}
uintmax_t
bignum_to_uintmax (Lisp_Object x)
{
  uintmax_t i;
  return mpz_to_uintmax (*xbignum_val (x), &i) ? i : 0;
}


/* Multiply and exponentiate mpz_t values without aborting due to size
   limits.  */

/* GMP tests for this value and aborts (!) if it is exceeded.
   This is as of GMP 6.1.2 (2016); perhaps future versions will differ.  */
enum { GMP_NLIMBS_MAX = min (INT_MAX, ULONG_MAX / GMP_NUMB_BITS) };

/* An upper bound on limb counts, needed to prevent libgmp and/or
   Emacs from aborting or otherwise misbehaving.  This bound applies
   to estimates of mpz_t sizes before the mpz_t objects are created,
   as opposed to integer-width which operates on mpz_t values after
   creation and before conversion to Lisp bignums.  */
enum
  {
   NLIMBS_LIMIT = min (min (/* libgmp needs to store limb counts.  */
			    GMP_NLIMBS_MAX,

			    /* Size calculations need to work.  */
			    min (PTRDIFF_MAX, SIZE_MAX) / sizeof (mp_limb_t)),

		       /* Emacs puts bit counts into fixnums.  */
		       MOST_POSITIVE_FIXNUM / GMP_NUMB_BITS)
  };

/* Like mpz_size, but tell the compiler the result is a nonnegative int.  */

static int
emacs_mpz_size (mpz_t const op)
{
  mp_size_t size = mpz_size (op);
  eassume (0 <= size && size <= INT_MAX);
  return size;
}

/* Wrappers to work around GMP limitations.  As of GMP 6.1.2 (2016),
   the library code aborts when a number is too large.  These wrappers
   avoid the problem for functions that can return numbers much larger
   than their arguments.  For slowly-growing numbers, the integer
   width checks in bignum.c should suffice.  */

void
emacs_mpz_mul (mpz_t rop, mpz_t const op1, mpz_t const op2)
{
  if (NLIMBS_LIMIT - emacs_mpz_size (op1) < emacs_mpz_size (op2))
    overflow_error ();
  mpz_mul (rop, op1, op2);
}

void
emacs_mpz_mul_2exp (mpz_t rop, mpz_t const op1, EMACS_INT op2)
{
  /* Fudge factor derived from GMP 6.1.2, to avoid an abort in
     mpz_mul_2exp (look for the '+ 1' in its source code).  */
  enum { mul_2exp_extra_limbs = 1 };
  enum { lim = min (NLIMBS_LIMIT, GMP_NLIMBS_MAX - mul_2exp_extra_limbs) };

  EMACS_INT op2limbs = op2 / GMP_NUMB_BITS;
  if (lim - emacs_mpz_size (op1) < op2limbs)
    overflow_error ();
  mpz_mul_2exp (rop, op1, op2);
}

void
emacs_mpz_pow_ui (mpz_t rop, mpz_t const base, unsigned long exp)
{
  /* This fudge factor is derived from GMP 6.1.2, to avoid an abort in
     mpz_n_pow_ui (look for the '5' in its source code).  */
  enum { pow_ui_extra_limbs = 5 };
  enum { lim = min (NLIMBS_LIMIT, GMP_NLIMBS_MAX - pow_ui_extra_limbs) };

  int nbase = emacs_mpz_size (base), n;
  if (ckd_mul (&n, nbase, exp) || lim < n)
    overflow_error ();
  mpz_pow_ui (rop, base, exp);
}


/* Yield an upper bound on the buffer size needed to contain a C
   string representing the NUM in base BASE.  This includes any
   preceding '-' and the terminating null.  */
static ptrdiff_t
mpz_bufsize (mpz_t const num, int base)
{
  return mpz_sizeinbase (num, base) + 2;
}
ptrdiff_t
bignum_bufsize (Lisp_Object num, int base)
{
  return mpz_bufsize (*xbignum_val (num), base);
}

/* Convert NUM to a nearest double, as opposed to mpz_get_d which
   truncates toward zero.  */
double
mpz_get_d_rounded (mpz_t const num)
{
  ptrdiff_t size = mpz_bufsize (num, 10);

  /* Use mpz_get_d as a shortcut for a bignum so small that rounding
     errors cannot occur, which is possible if EMACS_INT (not counting
     sign) has fewer bits than a double significand.  */
  if (! ((FLT_RADIX == 2 && DBL_MANT_DIG <= FIXNUM_BITS - 1)
	 || (FLT_RADIX == 16 && DBL_MANT_DIG * 4 <= FIXNUM_BITS - 1))
      && size <= DBL_DIG + 2)
    return mpz_get_d (num);

  USE_SAFE_ALLOCA;
  char *buf = SAFE_ALLOCA (size);
  mpz_get_str (buf, 10, num);
  double result = strtod (buf, NULL);
  SAFE_FREE ();
  return result;
}

/* Store into BUF (of size SIZE) the value of NUM as a base-BASE string.
   If BASE is negative, use upper-case digits in base -BASE.
   Return the string's length.
   SIZE must equal bignum_bufsize (NUM, abs (BASE)).  */
ptrdiff_t
bignum_to_c_string (char *buf, ptrdiff_t size, Lisp_Object num, int base)
{
  eassert (bignum_bufsize (num, abs (base)) == size);
  mpz_get_str (buf, base, *xbignum_val (num));
  ptrdiff_t n = size - 2;
  return !buf[n - 1] ? n - 1 : n + !!buf[n];
}

/* Convert NUM to a base-BASE Lisp string.
   If BASE is negative, use upper-case digits in base -BASE.  */

Lisp_Object
bignum_to_string (Lisp_Object num, int base)
{
  ptrdiff_t size = bignum_bufsize (num, abs (base));
  USE_SAFE_ALLOCA;
  char *str = SAFE_ALLOCA (size);
  ptrdiff_t len = bignum_to_c_string (str, size, num, base);
  Lisp_Object result = make_unibyte_string (str, len);
  SAFE_FREE ();
  return result;
}

/* Create a bignum by scanning NUM, with digits in BASE.
   NUM must consist of an optional '-', a nonempty sequence
   of base-BASE digits, and a terminating null byte, and
   the represented number must not be in fixnum range.  */

Lisp_Object
make_bignum_str (char const *num, int base)
{
  struct Lisp_Bignum *b = ALLOCATE_PLAIN_PSEUDOVECTOR (struct Lisp_Bignum,
						       PVEC_BIGNUM);
  mpz_init (b->value);
  int check = mpz_set_str (b->value, num, base);
  eassert (check == 0);
  return make_lisp_ptr (b, Lisp_Vectorlike);
}

/* Check that X is a Lisp integer in the range LO..HI.
   Return X's value as an intmax_t.  */

intmax_t
check_integer_range (Lisp_Object x, intmax_t lo, intmax_t hi)
{
  CHECK_INTEGER (x);
  intmax_t i;
  if (! (integer_to_intmax (x, &i) && lo <= i && i <= hi))
    args_out_of_range_3 (x, make_int (lo), make_int (hi));
  return i;
}

/* Check that X is a Lisp integer in the range 0..HI.
   Return X's value as an uintmax_t.  */

uintmax_t
check_uinteger_max (Lisp_Object x, uintmax_t hi)
{
  CHECK_INTEGER (x);
  uintmax_t i;
  if (! (integer_to_uintmax (x, &i) && i <= hi))
    args_out_of_range_3 (x, make_fixnum (0), make_uint (hi));
  return i;
}

/* Check that X is a Lisp integer no greater than INT_MAX,
   and return its value or zero, whichever is greater.  */

int
check_int_nonnegative (Lisp_Object x)
{
  CHECK_INTEGER (x);
  return NILP (Fnatnump (x)) ? 0 : check_integer_range (x, 0, INT_MAX);
}

/* Return a random mp_limb_t.  */

static mp_limb_t
get_random_limb (void)
{
  if (GMP_NUMB_BITS <= ULONG_WIDTH)
    return get_random_ulong ();

  /* Work around GCC -Wshift-count-overflow false alarm.  */
  int shift = GMP_NUMB_BITS <= ULONG_WIDTH ? 0 : ULONG_WIDTH;

  /* This is in case someone builds GMP with unusual definitions for
     MINI_GMP_LIMB_TYPE or _LONG_LONG_LIMB.  */
  mp_limb_t r = 0;
  for (int i = 0; i < GMP_NUMB_BITS; i += ULONG_WIDTH)
    r = (r << shift) | get_random_ulong ();
  return r;
}

/* Return a random mp_limb_t I in the range 0 <= I < LIM.
   If LIM is zero, simply return a random mp_limb_t.  */

static mp_limb_t
get_random_limb_lim (mp_limb_t lim)
{
  /* Return the remainder of a random mp_limb_t R divided by LIM,
     except reject the rare case where R is so close to the maximum
     mp_limb_t that the remainder isn't random.  */
  mp_limb_t difflim = - lim, diff, remainder;
  do
    {
      mp_limb_t r = get_random_limb ();
      if (lim == 0)
	return r;
      remainder = r % lim;
      diff = r - remainder;
    }
  while (difflim < diff);

  return remainder;
}

/* Return a random Lisp integer I in the range 0 <= I < LIMIT,
   where LIMIT is a positive bignum.  */

Lisp_Object
get_random_bignum (struct Lisp_Bignum const *limit)
{
  mpz_t const *lim = bignum_val (limit);
  mp_size_t nlimbs = mpz_size (*lim);
  eassume (0 < nlimbs);
  mp_limb_t *r_limb = mpz_limbs_write (mpz[0], nlimbs);
  mp_limb_t const *lim_limb = mpz_limbs_read (*lim);
  mp_limb_t limhi = lim_limb[nlimbs - 1];
  eassert (limhi);
  bool edgy;

  do
    {
      /* Generate the result one limb at a time, most significant first.
	 Choose the most significant limb RHI randomly from 0..LIMHI,
	 where LIMHI is the LIM's first limb, except choose from
	 0..(LIMHI-1) if there is just one limb.  RHI == LIMHI is an
	 unlucky edge case as later limbs might cause the result to be
	 exceed or equal LIM; if this happens, it causes another
	 iteration in the outer loop.  */

      mp_limb_t rhi = get_random_limb_lim (limhi + (1 < nlimbs));
      edgy = rhi == limhi;
      r_limb[nlimbs - 1] = rhi;

      for (mp_size_t i = nlimbs - 1; 0 < i--; )
	{
	  /* get_random_limb_lim (edgy ? limb_lim[i] + 1 : 0)
	     would be wrong here, as the full mp_limb_t range is
	     needed in later limbs for the edge case to have the
	     proper weighting.  */
	  mp_limb_t ri = get_random_limb ();
	  if (edgy)
	    {
	      if (lim_limb[i] < ri)
		break;
	      edgy = lim_limb[i] == ri;
	    }
	  r_limb[i] = ri;
	}
    }
  while (edgy);

  mpz_limbs_finish (mpz[0], nlimbs);
  return make_integer_mpz ();
}

debug log:

solving 330fdf4324c ...
found 330fdf4324c in https://yhetil.org/emacs-devel/p-W0YoiRjQW21JD6a3-xWurdrTQ_D7cfmZfKnr0PY95h2xd6w3Wg0Knk_m49zqRUeVjW3kO-6YPVOfEWjQGOzDKzxPIOJUXiGxBa8a0JzJk=@protonmail.com/
found 1fe195d78ea in https://git.savannah.gnu.org/cgit/emacs.git
preparing index
index prepared:
100644 1fe195d78ea5fefc485d0d17b497177cc2b11e7b	src/bignum.c

applying [1/1] https://yhetil.org/emacs-devel/p-W0YoiRjQW21JD6a3-xWurdrTQ_D7cfmZfKnr0PY95h2xd6w3Wg0Knk_m49zqRUeVjW3kO-6YPVOfEWjQGOzDKzxPIOJUXiGxBa8a0JzJk=@protonmail.com/
diff --git a/src/bignum.c b/src/bignum.c
index 1fe195d78ea..330fdf4324c 100644

Checking patch src/bignum.c...
Applied patch src/bignum.c cleanly.

index at:
100644 330fdf4324c0fd09220dbf4127ca31a123e25baa	src/bignum.c

(*) Git path names are given by the tree(s) the blob belongs to.
    Blobs themselves have no identifier aside from the hash of its contents.^

Code repositories for project(s) associated with this public inbox

	https://git.savannah.gnu.org/cgit/emacs.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).