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comparison libtommath/mtest/mpi.c @ 284:eed26cff980b

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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583) to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:49 +0000
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children 5ff8218bcee9
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1 /*
2 mpi.c
3
4 by Michael J. Fromberger <[email protected]>
5 Copyright (C) 1998 Michael J. Fromberger, All Rights Reserved
6
7 Arbitrary precision integer arithmetic library
8
9 $Id: mpi.c,v 1.22 2001/09/14 15:11:20 sting Exp sting $
10 */
11
12 #include "mpi.h"
13 #include <stdlib.h>
14 #include <string.h>
15 #include <ctype.h>
16
17 #if MP_DEBUG
18 #include <stdio.h>
19
20 #define DIAG(T,V) {fprintf(stderr,T);mp_print(V,stderr);fputc('\n',stderr);}
21 #else
22 #define DIAG(T,V)
23 #endif
24
25 /*
26 If MP_LOGTAB is not defined, use the math library to compute the
27 logarithms on the fly. Otherwise, use the static table below.
28 Pick which works best for your system.
29 */
30 #if MP_LOGTAB
31
32 /* {{{ s_logv_2[] - log table for 2 in various bases */
33
34 /*
35 A table of the logs of 2 for various bases (the 0 and 1 entries of
36 this table are meaningless and should not be referenced).
37
38 This table is used to compute output lengths for the mp_toradix()
39 function. Since a number n in radix r takes up about log_r(n)
40 digits, we estimate the output size by taking the least integer
41 greater than log_r(n), where:
42
43 log_r(n) = log_2(n) * log_r(2)
44
45 This table, therefore, is a table of log_r(2) for 2 <= r <= 36,
46 which are the output bases supported.
47 */
48
49 #include "logtab.h"
50
51 /* }}} */
52 #define LOG_V_2(R) s_logv_2[(R)]
53
54 #else
55
56 #include <math.h>
57 #define LOG_V_2(R) (log(2.0)/log(R))
58
59 #endif
60
61 /* Default precision for newly created mp_int's */
62 static unsigned int s_mp_defprec = MP_DEFPREC;
63
64 /* {{{ Digit arithmetic macros */
65
66 /*
67 When adding and multiplying digits, the results can be larger than
68 can be contained in an mp_digit. Thus, an mp_word is used. These
69 macros mask off the upper and lower digits of the mp_word (the
70 mp_word may be more than 2 mp_digits wide, but we only concern
71 ourselves with the low-order 2 mp_digits)
72
73 If your mp_word DOES have more than 2 mp_digits, you need to
74 uncomment the first line, and comment out the second.
75 */
76
77 /* #define CARRYOUT(W) (((W)>>DIGIT_BIT)&MP_DIGIT_MAX) */
78 #define CARRYOUT(W) ((W)>>DIGIT_BIT)
79 #define ACCUM(W) ((W)&MP_DIGIT_MAX)
80
81 /* }}} */
82
83 /* {{{ Comparison constants */
84
85 #define MP_LT -1
86 #define MP_EQ 0
87 #define MP_GT 1
88
89 /* }}} */
90
91 /* {{{ Constant strings */
92
93 /* Constant strings returned by mp_strerror() */
94 static const char *mp_err_string[] = {
95 "unknown result code", /* say what? */
96 "boolean true", /* MP_OKAY, MP_YES */
97 "boolean false", /* MP_NO */
98 "out of memory", /* MP_MEM */
99 "argument out of range", /* MP_RANGE */
100 "invalid input parameter", /* MP_BADARG */
101 "result is undefined" /* MP_UNDEF */
102 };
103
104 /* Value to digit maps for radix conversion */
105
106 /* s_dmap_1 - standard digits and letters */
107 static const char *s_dmap_1 =
108 "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/";
109
110 #if 0
111 /* s_dmap_2 - base64 ordering for digits */
112 static const char *s_dmap_2 =
113 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
114 #endif
115
116 /* }}} */
117
118 /* {{{ Static function declarations */
119
120 /*
121 If MP_MACRO is false, these will be defined as actual functions;
122 otherwise, suitable macro definitions will be used. This works
123 around the fact that ANSI C89 doesn't support an 'inline' keyword
124 (although I hear C9x will ... about bloody time). At present, the
125 macro definitions are identical to the function bodies, but they'll
126 expand in place, instead of generating a function call.
127
128 I chose these particular functions to be made into macros because
129 some profiling showed they are called a lot on a typical workload,
130 and yet they are primarily housekeeping.
131 */
132 #if MP_MACRO == 0
133 void s_mp_setz(mp_digit *dp, mp_size count); /* zero digits */
134 void s_mp_copy(mp_digit *sp, mp_digit *dp, mp_size count); /* copy */
135 void *s_mp_alloc(size_t nb, size_t ni); /* general allocator */
136 void s_mp_free(void *ptr); /* general free function */
137 #else
138
139 /* Even if these are defined as macros, we need to respect the settings
140 of the MP_MEMSET and MP_MEMCPY configuration options...
141 */
142 #if MP_MEMSET == 0
143 #define s_mp_setz(dp, count) \
144 {int ix;for(ix=0;ix<(count);ix++)(dp)[ix]=0;}
145 #else
146 #define s_mp_setz(dp, count) memset(dp, 0, (count) * sizeof(mp_digit))
147 #endif /* MP_MEMSET */
148
149 #if MP_MEMCPY == 0
150 #define s_mp_copy(sp, dp, count) \
151 {int ix;for(ix=0;ix<(count);ix++)(dp)[ix]=(sp)[ix];}
152 #else
153 #define s_mp_copy(sp, dp, count) memcpy(dp, sp, (count) * sizeof(mp_digit))
154 #endif /* MP_MEMCPY */
155
156 #define s_mp_alloc(nb, ni) calloc(nb, ni)
157 #define s_mp_free(ptr) {if(ptr) free(ptr);}
158 #endif /* MP_MACRO */
159
160 mp_err s_mp_grow(mp_int *mp, mp_size min); /* increase allocated size */
161 mp_err s_mp_pad(mp_int *mp, mp_size min); /* left pad with zeroes */
162
163 void s_mp_clamp(mp_int *mp); /* clip leading zeroes */
164
165 void s_mp_exch(mp_int *a, mp_int *b); /* swap a and b in place */
166
167 mp_err s_mp_lshd(mp_int *mp, mp_size p); /* left-shift by p digits */
168 void s_mp_rshd(mp_int *mp, mp_size p); /* right-shift by p digits */
169 void s_mp_div_2d(mp_int *mp, mp_digit d); /* divide by 2^d in place */
170 void s_mp_mod_2d(mp_int *mp, mp_digit d); /* modulo 2^d in place */
171 mp_err s_mp_mul_2d(mp_int *mp, mp_digit d); /* multiply by 2^d in place*/
172 void s_mp_div_2(mp_int *mp); /* divide by 2 in place */
173 mp_err s_mp_mul_2(mp_int *mp); /* multiply by 2 in place */
174 mp_digit s_mp_norm(mp_int *a, mp_int *b); /* normalize for division */
175 mp_err s_mp_add_d(mp_int *mp, mp_digit d); /* unsigned digit addition */
176 mp_err s_mp_sub_d(mp_int *mp, mp_digit d); /* unsigned digit subtract */
177 mp_err s_mp_mul_d(mp_int *mp, mp_digit d); /* unsigned digit multiply */
178 mp_err s_mp_div_d(mp_int *mp, mp_digit d, mp_digit *r);
179 /* unsigned digit divide */
180 mp_err s_mp_reduce(mp_int *x, mp_int *m, mp_int *mu);
181 /* Barrett reduction */
182 mp_err s_mp_add(mp_int *a, mp_int *b); /* magnitude addition */
183 mp_err s_mp_sub(mp_int *a, mp_int *b); /* magnitude subtract */
184 mp_err s_mp_mul(mp_int *a, mp_int *b); /* magnitude multiply */
185 #if 0
186 void s_mp_kmul(mp_digit *a, mp_digit *b, mp_digit *out, mp_size len);
187 /* multiply buffers in place */
188 #endif
189 #if MP_SQUARE
190 mp_err s_mp_sqr(mp_int *a); /* magnitude square */
191 #else
192 #define s_mp_sqr(a) s_mp_mul(a, a)
193 #endif
194 mp_err s_mp_div(mp_int *a, mp_int *b); /* magnitude divide */
195 mp_err s_mp_2expt(mp_int *a, mp_digit k); /* a = 2^k */
196 int s_mp_cmp(mp_int *a, mp_int *b); /* magnitude comparison */
197 int s_mp_cmp_d(mp_int *a, mp_digit d); /* magnitude digit compare */
198 int s_mp_ispow2(mp_int *v); /* is v a power of 2? */
199 int s_mp_ispow2d(mp_digit d); /* is d a power of 2? */
200
201 int s_mp_tovalue(char ch, int r); /* convert ch to value */
202 char s_mp_todigit(int val, int r, int low); /* convert val to digit */
203 int s_mp_outlen(int bits, int r); /* output length in bytes */
204
205 /* }}} */
206
207 /* {{{ Default precision manipulation */
208
209 unsigned int mp_get_prec(void)
210 {
211 return s_mp_defprec;
212
213 } /* end mp_get_prec() */
214
215 void mp_set_prec(unsigned int prec)
216 {
217 if(prec == 0)
218 s_mp_defprec = MP_DEFPREC;
219 else
220 s_mp_defprec = prec;
221
222 } /* end mp_set_prec() */
223
224 /* }}} */
225
226 /*------------------------------------------------------------------------*/
227 /* {{{ mp_init(mp) */
228
229 /*
230 mp_init(mp)
231
232 Initialize a new zero-valued mp_int. Returns MP_OKAY if successful,
233 MP_MEM if memory could not be allocated for the structure.
234 */
235
236 mp_err mp_init(mp_int *mp)
237 {
238 return mp_init_size(mp, s_mp_defprec);
239
240 } /* end mp_init() */
241
242 /* }}} */
243
244 /* {{{ mp_init_array(mp[], count) */
245
246 mp_err mp_init_array(mp_int mp[], int count)
247 {
248 mp_err res;
249 int pos;
250
251 ARGCHK(mp !=NULL && count > 0, MP_BADARG);
252
253 for(pos = 0; pos < count; ++pos) {
254 if((res = mp_init(&mp[pos])) != MP_OKAY)
255 goto CLEANUP;
256 }
257
258 return MP_OKAY;
259
260 CLEANUP:
261 while(--pos >= 0)
262 mp_clear(&mp[pos]);
263
264 return res;
265
266 } /* end mp_init_array() */
267
268 /* }}} */
269
270 /* {{{ mp_init_size(mp, prec) */
271
272 /*
273 mp_init_size(mp, prec)
274
275 Initialize a new zero-valued mp_int with at least the given
276 precision; returns MP_OKAY if successful, or MP_MEM if memory could
277 not be allocated for the structure.
278 */
279
280 mp_err mp_init_size(mp_int *mp, mp_size prec)
281 {
282 ARGCHK(mp != NULL && prec > 0, MP_BADARG);
283
284 if((DIGITS(mp) = s_mp_alloc(prec, sizeof(mp_digit))) == NULL)
285 return MP_MEM;
286
287 SIGN(mp) = MP_ZPOS;
288 USED(mp) = 1;
289 ALLOC(mp) = prec;
290
291 return MP_OKAY;
292
293 } /* end mp_init_size() */
294
295 /* }}} */
296
297 /* {{{ mp_init_copy(mp, from) */
298
299 /*
300 mp_init_copy(mp, from)
301
302 Initialize mp as an exact copy of from. Returns MP_OKAY if
303 successful, MP_MEM if memory could not be allocated for the new
304 structure.
305 */
306
307 mp_err mp_init_copy(mp_int *mp, mp_int *from)
308 {
309 ARGCHK(mp != NULL && from != NULL, MP_BADARG);
310
311 if(mp == from)
312 return MP_OKAY;
313
314 if((DIGITS(mp) = s_mp_alloc(USED(from), sizeof(mp_digit))) == NULL)
315 return MP_MEM;
316
317 s_mp_copy(DIGITS(from), DIGITS(mp), USED(from));
318 USED(mp) = USED(from);
319 ALLOC(mp) = USED(from);
320 SIGN(mp) = SIGN(from);
321
322 return MP_OKAY;
323
324 } /* end mp_init_copy() */
325
326 /* }}} */
327
328 /* {{{ mp_copy(from, to) */
329
330 /*
331 mp_copy(from, to)
332
333 Copies the mp_int 'from' to the mp_int 'to'. It is presumed that
334 'to' has already been initialized (if not, use mp_init_copy()
335 instead). If 'from' and 'to' are identical, nothing happens.
336 */
337
338 mp_err mp_copy(mp_int *from, mp_int *to)
339 {
340 ARGCHK(from != NULL && to != NULL, MP_BADARG);
341
342 if(from == to)
343 return MP_OKAY;
344
345 { /* copy */
346 mp_digit *tmp;
347
348 /*
349 If the allocated buffer in 'to' already has enough space to hold
350 all the used digits of 'from', we'll re-use it to avoid hitting
351 the memory allocater more than necessary; otherwise, we'd have
352 to grow anyway, so we just allocate a hunk and make the copy as
353 usual
354 */
355 if(ALLOC(to) >= USED(from)) {
356 s_mp_setz(DIGITS(to) + USED(from), ALLOC(to) - USED(from));
357 s_mp_copy(DIGITS(from), DIGITS(to), USED(from));
358
359 } else {
360 if((tmp = s_mp_alloc(USED(from), sizeof(mp_digit))) == NULL)
361 return MP_MEM;
362
363 s_mp_copy(DIGITS(from), tmp, USED(from));
364
365 if(DIGITS(to) != NULL) {
366 #if MP_CRYPTO
367 s_mp_setz(DIGITS(to), ALLOC(to));
368 #endif
369 s_mp_free(DIGITS(to));
370 }
371
372 DIGITS(to) = tmp;
373 ALLOC(to) = USED(from);
374 }
375
376 /* Copy the precision and sign from the original */
377 USED(to) = USED(from);
378 SIGN(to) = SIGN(from);
379 } /* end copy */
380
381 return MP_OKAY;
382
383 } /* end mp_copy() */
384
385 /* }}} */
386
387 /* {{{ mp_exch(mp1, mp2) */
388
389 /*
390 mp_exch(mp1, mp2)
391
392 Exchange mp1 and mp2 without allocating any intermediate memory
393 (well, unless you count the stack space needed for this call and the
394 locals it creates...). This cannot fail.
395 */
396
397 void mp_exch(mp_int *mp1, mp_int *mp2)
398 {
399 #if MP_ARGCHK == 2
400 assert(mp1 != NULL && mp2 != NULL);
401 #else
402 if(mp1 == NULL || mp2 == NULL)
403 return;
404 #endif
405
406 s_mp_exch(mp1, mp2);
407
408 } /* end mp_exch() */
409
410 /* }}} */
411
412 /* {{{ mp_clear(mp) */
413
414 /*
415 mp_clear(mp)
416
417 Release the storage used by an mp_int, and void its fields so that
418 if someone calls mp_clear() again for the same int later, we won't
419 get tollchocked.
420 */
421
422 void mp_clear(mp_int *mp)
423 {
424 if(mp == NULL)
425 return;
426
427 if(DIGITS(mp) != NULL) {
428 #if MP_CRYPTO
429 s_mp_setz(DIGITS(mp), ALLOC(mp));
430 #endif
431 s_mp_free(DIGITS(mp));
432 DIGITS(mp) = NULL;
433 }
434
435 USED(mp) = 0;
436 ALLOC(mp) = 0;
437
438 } /* end mp_clear() */
439
440 /* }}} */
441
442 /* {{{ mp_clear_array(mp[], count) */
443
444 void mp_clear_array(mp_int mp[], int count)
445 {
446 ARGCHK(mp != NULL && count > 0, MP_BADARG);
447
448 while(--count >= 0)
449 mp_clear(&mp[count]);
450
451 } /* end mp_clear_array() */
452
453 /* }}} */
454
455 /* {{{ mp_zero(mp) */
456
457 /*
458 mp_zero(mp)
459
460 Set mp to zero. Does not change the allocated size of the structure,
461 and therefore cannot fail (except on a bad argument, which we ignore)
462 */
463 void mp_zero(mp_int *mp)
464 {
465 if(mp == NULL)
466 return;
467
468 s_mp_setz(DIGITS(mp), ALLOC(mp));
469 USED(mp) = 1;
470 SIGN(mp) = MP_ZPOS;
471
472 } /* end mp_zero() */
473
474 /* }}} */
475
476 /* {{{ mp_set(mp, d) */
477
478 void mp_set(mp_int *mp, mp_digit d)
479 {
480 if(mp == NULL)
481 return;
482
483 mp_zero(mp);
484 DIGIT(mp, 0) = d;
485
486 } /* end mp_set() */
487
488 /* }}} */
489
490 /* {{{ mp_set_int(mp, z) */
491
492 mp_err mp_set_int(mp_int *mp, long z)
493 {
494 int ix;
495 unsigned long v = abs(z);
496 mp_err res;
497
498 ARGCHK(mp != NULL, MP_BADARG);
499
500 mp_zero(mp);
501 if(z == 0)
502 return MP_OKAY; /* shortcut for zero */
503
504 for(ix = sizeof(long) - 1; ix >= 0; ix--) {
505
506 if((res = s_mp_mul_2d(mp, CHAR_BIT)) != MP_OKAY)
507 return res;
508
509 res = s_mp_add_d(mp,
510 (mp_digit)((v >> (ix * CHAR_BIT)) & UCHAR_MAX));
511 if(res != MP_OKAY)
512 return res;
513
514 }
515
516 if(z < 0)
517 SIGN(mp) = MP_NEG;
518
519 return MP_OKAY;
520
521 } /* end mp_set_int() */
522
523 /* }}} */
524
525 /*------------------------------------------------------------------------*/
526 /* {{{ Digit arithmetic */
527
528 /* {{{ mp_add_d(a, d, b) */
529
530 /*
531 mp_add_d(a, d, b)
532
533 Compute the sum b = a + d, for a single digit d. Respects the sign of
534 its primary addend (single digits are unsigned anyway).
535 */
536
537 mp_err mp_add_d(mp_int *a, mp_digit d, mp_int *b)
538 {
539 mp_err res = MP_OKAY;
540
541 ARGCHK(a != NULL && b != NULL, MP_BADARG);
542
543 if((res = mp_copy(a, b)) != MP_OKAY)
544 return res;
545
546 if(SIGN(b) == MP_ZPOS) {
547 res = s_mp_add_d(b, d);
548 } else if(s_mp_cmp_d(b, d) >= 0) {
549 res = s_mp_sub_d(b, d);
550 } else {
551 SIGN(b) = MP_ZPOS;
552
553 DIGIT(b, 0) = d - DIGIT(b, 0);
554 }
555
556 return res;
557
558 } /* end mp_add_d() */
559
560 /* }}} */
561
562 /* {{{ mp_sub_d(a, d, b) */
563
564 /*
565 mp_sub_d(a, d, b)
566
567 Compute the difference b = a - d, for a single digit d. Respects the
568 sign of its subtrahend (single digits are unsigned anyway).
569 */
570
571 mp_err mp_sub_d(mp_int *a, mp_digit d, mp_int *b)
572 {
573 mp_err res;
574
575 ARGCHK(a != NULL && b != NULL, MP_BADARG);
576
577 if((res = mp_copy(a, b)) != MP_OKAY)
578 return res;
579
580 if(SIGN(b) == MP_NEG) {
581 if((res = s_mp_add_d(b, d)) != MP_OKAY)
582 return res;
583
584 } else if(s_mp_cmp_d(b, d) >= 0) {
585 if((res = s_mp_sub_d(b, d)) != MP_OKAY)
586 return res;
587
588 } else {
589 mp_neg(b, b);
590
591 DIGIT(b, 0) = d - DIGIT(b, 0);
592 SIGN(b) = MP_NEG;
593 }
594
595 if(s_mp_cmp_d(b, 0) == 0)
596 SIGN(b) = MP_ZPOS;
597
598 return MP_OKAY;
599
600 } /* end mp_sub_d() */
601
602 /* }}} */
603
604 /* {{{ mp_mul_d(a, d, b) */
605
606 /*
607 mp_mul_d(a, d, b)
608
609 Compute the product b = a * d, for a single digit d. Respects the sign
610 of its multiplicand (single digits are unsigned anyway)
611 */
612
613 mp_err mp_mul_d(mp_int *a, mp_digit d, mp_int *b)
614 {
615 mp_err res;
616
617 ARGCHK(a != NULL && b != NULL, MP_BADARG);
618
619 if(d == 0) {
620 mp_zero(b);
621 return MP_OKAY;
622 }
623
624 if((res = mp_copy(a, b)) != MP_OKAY)
625 return res;
626
627 res = s_mp_mul_d(b, d);
628
629 return res;
630
631 } /* end mp_mul_d() */
632
633 /* }}} */
634
635 /* {{{ mp_mul_2(a, c) */
636
637 mp_err mp_mul_2(mp_int *a, mp_int *c)
638 {
639 mp_err res;
640
641 ARGCHK(a != NULL && c != NULL, MP_BADARG);
642
643 if((res = mp_copy(a, c)) != MP_OKAY)
644 return res;
645
646 return s_mp_mul_2(c);
647
648 } /* end mp_mul_2() */
649
650 /* }}} */
651
652 /* {{{ mp_div_d(a, d, q, r) */
653
654 /*
655 mp_div_d(a, d, q, r)
656
657 Compute the quotient q = a / d and remainder r = a mod d, for a
658 single digit d. Respects the sign of its divisor (single digits are
659 unsigned anyway).
660 */
661
662 mp_err mp_div_d(mp_int *a, mp_digit d, mp_int *q, mp_digit *r)
663 {
664 mp_err res;
665 mp_digit rem;
666 int pow;
667
668 ARGCHK(a != NULL, MP_BADARG);
669
670 if(d == 0)
671 return MP_RANGE;
672
673 /* Shortcut for powers of two ... */
674 if((pow = s_mp_ispow2d(d)) >= 0) {
675 mp_digit mask;
676
677 mask = (1 << pow) - 1;
678 rem = DIGIT(a, 0) & mask;
679
680 if(q) {
681 mp_copy(a, q);
682 s_mp_div_2d(q, pow);
683 }
684
685 if(r)
686 *r = rem;
687
688 return MP_OKAY;
689 }
690
691 /*
692 If the quotient is actually going to be returned, we'll try to
693 avoid hitting the memory allocator by copying the dividend into it
694 and doing the division there. This can't be any _worse_ than
695 always copying, and will sometimes be better (since it won't make
696 another copy)
697
698 If it's not going to be returned, we need to allocate a temporary
699 to hold the quotient, which will just be discarded.
700 */
701 if(q) {
702 if((res = mp_copy(a, q)) != MP_OKAY)
703 return res;
704
705 res = s_mp_div_d(q, d, &rem);
706 if(s_mp_cmp_d(q, 0) == MP_EQ)
707 SIGN(q) = MP_ZPOS;
708
709 } else {
710 mp_int qp;
711
712 if((res = mp_init_copy(&qp, a)) != MP_OKAY)
713 return res;
714
715 res = s_mp_div_d(&qp, d, &rem);
716 if(s_mp_cmp_d(&qp, 0) == 0)
717 SIGN(&qp) = MP_ZPOS;
718
719 mp_clear(&qp);
720 }
721
722 if(r)
723 *r = rem;
724
725 return res;
726
727 } /* end mp_div_d() */
728
729 /* }}} */
730
731 /* {{{ mp_div_2(a, c) */
732
733 /*
734 mp_div_2(a, c)
735
736 Compute c = a / 2, disregarding the remainder.
737 */
738
739 mp_err mp_div_2(mp_int *a, mp_int *c)
740 {
741 mp_err res;
742
743 ARGCHK(a != NULL && c != NULL, MP_BADARG);
744
745 if((res = mp_copy(a, c)) != MP_OKAY)
746 return res;
747
748 s_mp_div_2(c);
749
750 return MP_OKAY;
751
752 } /* end mp_div_2() */
753
754 /* }}} */
755
756 /* {{{ mp_expt_d(a, d, b) */
757
758 mp_err mp_expt_d(mp_int *a, mp_digit d, mp_int *c)
759 {
760 mp_int s, x;
761 mp_err res;
762
763 ARGCHK(a != NULL && c != NULL, MP_BADARG);
764
765 if((res = mp_init(&s)) != MP_OKAY)
766 return res;
767 if((res = mp_init_copy(&x, a)) != MP_OKAY)
768 goto X;
769
770 DIGIT(&s, 0) = 1;
771
772 while(d != 0) {
773 if(d & 1) {
774 if((res = s_mp_mul(&s, &x)) != MP_OKAY)
775 goto CLEANUP;
776 }
777
778 d >>= 1;
779
780 if((res = s_mp_sqr(&x)) != MP_OKAY)
781 goto CLEANUP;
782 }
783
784 s_mp_exch(&s, c);
785
786 CLEANUP:
787 mp_clear(&x);
788 X:
789 mp_clear(&s);
790
791 return res;
792
793 } /* end mp_expt_d() */
794
795 /* }}} */
796
797 /* }}} */
798
799 /*------------------------------------------------------------------------*/
800 /* {{{ Full arithmetic */
801
802 /* {{{ mp_abs(a, b) */
803
804 /*
805 mp_abs(a, b)
806
807 Compute b = |a|. 'a' and 'b' may be identical.
808 */
809
810 mp_err mp_abs(mp_int *a, mp_int *b)
811 {
812 mp_err res;
813
814 ARGCHK(a != NULL && b != NULL, MP_BADARG);
815
816 if((res = mp_copy(a, b)) != MP_OKAY)
817 return res;
818
819 SIGN(b) = MP_ZPOS;
820
821 return MP_OKAY;
822
823 } /* end mp_abs() */
824
825 /* }}} */
826
827 /* {{{ mp_neg(a, b) */
828
829 /*
830 mp_neg(a, b)
831
832 Compute b = -a. 'a' and 'b' may be identical.
833 */
834
835 mp_err mp_neg(mp_int *a, mp_int *b)
836 {
837 mp_err res;
838
839 ARGCHK(a != NULL && b != NULL, MP_BADARG);
840
841 if((res = mp_copy(a, b)) != MP_OKAY)
842 return res;
843
844 if(s_mp_cmp_d(b, 0) == MP_EQ)
845 SIGN(b) = MP_ZPOS;
846 else
847 SIGN(b) = (SIGN(b) == MP_NEG) ? MP_ZPOS : MP_NEG;
848
849 return MP_OKAY;
850
851 } /* end mp_neg() */
852
853 /* }}} */
854
855 /* {{{ mp_add(a, b, c) */
856
857 /*
858 mp_add(a, b, c)
859
860 Compute c = a + b. All parameters may be identical.
861 */
862
863 mp_err mp_add(mp_int *a, mp_int *b, mp_int *c)
864 {
865 mp_err res;
866 int cmp;
867
868 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
869
870 if(SIGN(a) == SIGN(b)) { /* same sign: add values, keep sign */
871
872 /* Commutativity of addition lets us do this in either order,
873 so we avoid having to use a temporary even if the result
874 is supposed to replace the output
875 */
876 if(c == b) {
877 if((res = s_mp_add(c, a)) != MP_OKAY)
878 return res;
879 } else {
880 if(c != a && (res = mp_copy(a, c)) != MP_OKAY)
881 return res;
882
883 if((res = s_mp_add(c, b)) != MP_OKAY)
884 return res;
885 }
886
887 } else if((cmp = s_mp_cmp(a, b)) > 0) { /* different sign: a > b */
888
889 /* If the output is going to be clobbered, we will use a temporary
890 variable; otherwise, we'll do it without touching the memory
891 allocator at all, if possible
892 */
893 if(c == b) {
894 mp_int tmp;
895
896 if((res = mp_init_copy(&tmp, a)) != MP_OKAY)
897 return res;
898 if((res = s_mp_sub(&tmp, b)) != MP_OKAY) {
899 mp_clear(&tmp);
900 return res;
901 }
902
903 s_mp_exch(&tmp, c);
904 mp_clear(&tmp);
905
906 } else {
907
908 if(c != a && (res = mp_copy(a, c)) != MP_OKAY)
909 return res;
910 if((res = s_mp_sub(c, b)) != MP_OKAY)
911 return res;
912
913 }
914
915 } else if(cmp == 0) { /* different sign, a == b */
916
917 mp_zero(c);
918 return MP_OKAY;
919
920 } else { /* different sign: a < b */
921
922 /* See above... */
923 if(c == a) {
924 mp_int tmp;
925
926 if((res = mp_init_copy(&tmp, b)) != MP_OKAY)
927 return res;
928 if((res = s_mp_sub(&tmp, a)) != MP_OKAY) {
929 mp_clear(&tmp);
930 return res;
931 }
932
933 s_mp_exch(&tmp, c);
934 mp_clear(&tmp);
935
936 } else {
937
938 if(c != b && (res = mp_copy(b, c)) != MP_OKAY)
939 return res;
940 if((res = s_mp_sub(c, a)) != MP_OKAY)
941 return res;
942
943 }
944 }
945
946 if(USED(c) == 1 && DIGIT(c, 0) == 0)
947 SIGN(c) = MP_ZPOS;
948
949 return MP_OKAY;
950
951 } /* end mp_add() */
952
953 /* }}} */
954
955 /* {{{ mp_sub(a, b, c) */
956
957 /*
958 mp_sub(a, b, c)
959
960 Compute c = a - b. All parameters may be identical.
961 */
962
963 mp_err mp_sub(mp_int *a, mp_int *b, mp_int *c)
964 {
965 mp_err res;
966 int cmp;
967
968 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
969
970 if(SIGN(a) != SIGN(b)) {
971 if(c == a) {
972 if((res = s_mp_add(c, b)) != MP_OKAY)
973 return res;
974 } else {
975 if(c != b && ((res = mp_copy(b, c)) != MP_OKAY))
976 return res;
977 if((res = s_mp_add(c, a)) != MP_OKAY)
978 return res;
979 SIGN(c) = SIGN(a);
980 }
981
982 } else if((cmp = s_mp_cmp(a, b)) > 0) { /* Same sign, a > b */
983 if(c == b) {
984 mp_int tmp;
985
986 if((res = mp_init_copy(&tmp, a)) != MP_OKAY)
987 return res;
988 if((res = s_mp_sub(&tmp, b)) != MP_OKAY) {
989 mp_clear(&tmp);
990 return res;
991 }
992 s_mp_exch(&tmp, c);
993 mp_clear(&tmp);
994
995 } else {
996 if(c != a && ((res = mp_copy(a, c)) != MP_OKAY))
997 return res;
998
999 if((res = s_mp_sub(c, b)) != MP_OKAY)
1000 return res;
1001 }
1002
1003 } else if(cmp == 0) { /* Same sign, equal magnitude */
1004 mp_zero(c);
1005 return MP_OKAY;
1006
1007 } else { /* Same sign, b > a */
1008 if(c == a) {
1009 mp_int tmp;
1010
1011 if((res = mp_init_copy(&tmp, b)) != MP_OKAY)
1012 return res;
1013
1014 if((res = s_mp_sub(&tmp, a)) != MP_OKAY) {
1015 mp_clear(&tmp);
1016 return res;
1017 }
1018 s_mp_exch(&tmp, c);
1019 mp_clear(&tmp);
1020
1021 } else {
1022 if(c != b && ((res = mp_copy(b, c)) != MP_OKAY))
1023 return res;
1024
1025 if((res = s_mp_sub(c, a)) != MP_OKAY)
1026 return res;
1027 }
1028
1029 SIGN(c) = !SIGN(b);
1030 }
1031
1032 if(USED(c) == 1 && DIGIT(c, 0) == 0)
1033 SIGN(c) = MP_ZPOS;
1034
1035 return MP_OKAY;
1036
1037 } /* end mp_sub() */
1038
1039 /* }}} */
1040
1041 /* {{{ mp_mul(a, b, c) */
1042
1043 /*
1044 mp_mul(a, b, c)
1045
1046 Compute c = a * b. All parameters may be identical.
1047 */
1048
1049 mp_err mp_mul(mp_int *a, mp_int *b, mp_int *c)
1050 {
1051 mp_err res;
1052 mp_sign sgn;
1053
1054 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
1055
1056 sgn = (SIGN(a) == SIGN(b)) ? MP_ZPOS : MP_NEG;
1057
1058 if(c == b) {
1059 if((res = s_mp_mul(c, a)) != MP_OKAY)
1060 return res;
1061
1062 } else {
1063 if((res = mp_copy(a, c)) != MP_OKAY)
1064 return res;
1065
1066 if((res = s_mp_mul(c, b)) != MP_OKAY)
1067 return res;
1068 }
1069
1070 if(sgn == MP_ZPOS || s_mp_cmp_d(c, 0) == MP_EQ)
1071 SIGN(c) = MP_ZPOS;
1072 else
1073 SIGN(c) = sgn;
1074
1075 return MP_OKAY;
1076
1077 } /* end mp_mul() */
1078
1079 /* }}} */
1080
1081 /* {{{ mp_mul_2d(a, d, c) */
1082
1083 /*
1084 mp_mul_2d(a, d, c)
1085
1086 Compute c = a * 2^d. a may be the same as c.
1087 */
1088
1089 mp_err mp_mul_2d(mp_int *a, mp_digit d, mp_int *c)
1090 {
1091 mp_err res;
1092
1093 ARGCHK(a != NULL && c != NULL, MP_BADARG);
1094
1095 if((res = mp_copy(a, c)) != MP_OKAY)
1096 return res;
1097
1098 if(d == 0)
1099 return MP_OKAY;
1100
1101 return s_mp_mul_2d(c, d);
1102
1103 } /* end mp_mul() */
1104
1105 /* }}} */
1106
1107 /* {{{ mp_sqr(a, b) */
1108
1109 #if MP_SQUARE
1110 mp_err mp_sqr(mp_int *a, mp_int *b)
1111 {
1112 mp_err res;
1113
1114 ARGCHK(a != NULL && b != NULL, MP_BADARG);
1115
1116 if((res = mp_copy(a, b)) != MP_OKAY)
1117 return res;
1118
1119 if((res = s_mp_sqr(b)) != MP_OKAY)
1120 return res;
1121
1122 SIGN(b) = MP_ZPOS;
1123
1124 return MP_OKAY;
1125
1126 } /* end mp_sqr() */
1127 #endif
1128
1129 /* }}} */
1130
1131 /* {{{ mp_div(a, b, q, r) */
1132
1133 /*
1134 mp_div(a, b, q, r)
1135
1136 Compute q = a / b and r = a mod b. Input parameters may be re-used
1137 as output parameters. If q or r is NULL, that portion of the
1138 computation will be discarded (although it will still be computed)
1139
1140 Pay no attention to the hacker behind the curtain.
1141 */
1142
1143 mp_err mp_div(mp_int *a, mp_int *b, mp_int *q, mp_int *r)
1144 {
1145 mp_err res;
1146 mp_int qtmp, rtmp;
1147 int cmp;
1148
1149 ARGCHK(a != NULL && b != NULL, MP_BADARG);
1150
1151 if(mp_cmp_z(b) == MP_EQ)
1152 return MP_RANGE;
1153
1154 /* If a <= b, we can compute the solution without division, and
1155 avoid any memory allocation
1156 */
1157 if((cmp = s_mp_cmp(a, b)) < 0) {
1158 if(r) {
1159 if((res = mp_copy(a, r)) != MP_OKAY)
1160 return res;
1161 }
1162
1163 if(q)
1164 mp_zero(q);
1165
1166 return MP_OKAY;
1167
1168 } else if(cmp == 0) {
1169
1170 /* Set quotient to 1, with appropriate sign */
1171 if(q) {
1172 int qneg = (SIGN(a) != SIGN(b));
1173
1174 mp_set(q, 1);
1175 if(qneg)
1176 SIGN(q) = MP_NEG;
1177 }
1178
1179 if(r)
1180 mp_zero(r);
1181
1182 return MP_OKAY;
1183 }
1184
1185 /* If we get here, it means we actually have to do some division */
1186
1187 /* Set up some temporaries... */
1188 if((res = mp_init_copy(&qtmp, a)) != MP_OKAY)
1189 return res;
1190 if((res = mp_init_copy(&rtmp, b)) != MP_OKAY)
1191 goto CLEANUP;
1192
1193 if((res = s_mp_div(&qtmp, &rtmp)) != MP_OKAY)
1194 goto CLEANUP;
1195
1196 /* Compute the signs for the output */
1197 SIGN(&rtmp) = SIGN(a); /* Sr = Sa */
1198 if(SIGN(a) == SIGN(b))
1199 SIGN(&qtmp) = MP_ZPOS; /* Sq = MP_ZPOS if Sa = Sb */
1200 else
1201 SIGN(&qtmp) = MP_NEG; /* Sq = MP_NEG if Sa != Sb */
1202
1203 if(s_mp_cmp_d(&qtmp, 0) == MP_EQ)
1204 SIGN(&qtmp) = MP_ZPOS;
1205 if(s_mp_cmp_d(&rtmp, 0) == MP_EQ)
1206 SIGN(&rtmp) = MP_ZPOS;
1207
1208 /* Copy output, if it is needed */
1209 if(q)
1210 s_mp_exch(&qtmp, q);
1211
1212 if(r)
1213 s_mp_exch(&rtmp, r);
1214
1215 CLEANUP:
1216 mp_clear(&rtmp);
1217 mp_clear(&qtmp);
1218
1219 return res;
1220
1221 } /* end mp_div() */
1222
1223 /* }}} */
1224
1225 /* {{{ mp_div_2d(a, d, q, r) */
1226
1227 mp_err mp_div_2d(mp_int *a, mp_digit d, mp_int *q, mp_int *r)
1228 {
1229 mp_err res;
1230
1231 ARGCHK(a != NULL, MP_BADARG);
1232
1233 if(q) {
1234 if((res = mp_copy(a, q)) != MP_OKAY)
1235 return res;
1236
1237 s_mp_div_2d(q, d);
1238 }
1239
1240 if(r) {
1241 if((res = mp_copy(a, r)) != MP_OKAY)
1242 return res;
1243
1244 s_mp_mod_2d(r, d);
1245 }
1246
1247 return MP_OKAY;
1248
1249 } /* end mp_div_2d() */
1250
1251 /* }}} */
1252
1253 /* {{{ mp_expt(a, b, c) */
1254
1255 /*
1256 mp_expt(a, b, c)
1257
1258 Compute c = a ** b, that is, raise a to the b power. Uses a
1259 standard iterative square-and-multiply technique.
1260 */
1261
1262 mp_err mp_expt(mp_int *a, mp_int *b, mp_int *c)
1263 {
1264 mp_int s, x;
1265 mp_err res;
1266 mp_digit d;
1267 int dig, bit;
1268
1269 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
1270
1271 if(mp_cmp_z(b) < 0)
1272 return MP_RANGE;
1273
1274 if((res = mp_init(&s)) != MP_OKAY)
1275 return res;
1276
1277 mp_set(&s, 1);
1278
1279 if((res = mp_init_copy(&x, a)) != MP_OKAY)
1280 goto X;
1281
1282 /* Loop over low-order digits in ascending order */
1283 for(dig = 0; dig < (USED(b) - 1); dig++) {
1284 d = DIGIT(b, dig);
1285
1286 /* Loop over bits of each non-maximal digit */
1287 for(bit = 0; bit < DIGIT_BIT; bit++) {
1288 if(d & 1) {
1289 if((res = s_mp_mul(&s, &x)) != MP_OKAY)
1290 goto CLEANUP;
1291 }
1292
1293 d >>= 1;
1294
1295 if((res = s_mp_sqr(&x)) != MP_OKAY)
1296 goto CLEANUP;
1297 }
1298 }
1299
1300 /* Consider now the last digit... */
1301 d = DIGIT(b, dig);
1302
1303 while(d) {
1304 if(d & 1) {
1305 if((res = s_mp_mul(&s, &x)) != MP_OKAY)
1306 goto CLEANUP;
1307 }
1308
1309 d >>= 1;
1310
1311 if((res = s_mp_sqr(&x)) != MP_OKAY)
1312 goto CLEANUP;
1313 }
1314
1315 if(mp_iseven(b))
1316 SIGN(&s) = SIGN(a);
1317
1318 res = mp_copy(&s, c);
1319
1320 CLEANUP:
1321 mp_clear(&x);
1322 X:
1323 mp_clear(&s);
1324
1325 return res;
1326
1327 } /* end mp_expt() */
1328
1329 /* }}} */
1330
1331 /* {{{ mp_2expt(a, k) */
1332
1333 /* Compute a = 2^k */
1334
1335 mp_err mp_2expt(mp_int *a, mp_digit k)
1336 {
1337 ARGCHK(a != NULL, MP_BADARG);
1338
1339 return s_mp_2expt(a, k);
1340
1341 } /* end mp_2expt() */
1342
1343 /* }}} */
1344
1345 /* {{{ mp_mod(a, m, c) */
1346
1347 /*
1348 mp_mod(a, m, c)
1349
1350 Compute c = a (mod m). Result will always be 0 <= c < m.
1351 */
1352
1353 mp_err mp_mod(mp_int *a, mp_int *m, mp_int *c)
1354 {
1355 mp_err res;
1356 int mag;
1357
1358 ARGCHK(a != NULL && m != NULL && c != NULL, MP_BADARG);
1359
1360 if(SIGN(m) == MP_NEG)
1361 return MP_RANGE;
1362
1363 /*
1364 If |a| > m, we need to divide to get the remainder and take the
1365 absolute value.
1366
1367 If |a| < m, we don't need to do any division, just copy and adjust
1368 the sign (if a is negative).
1369
1370 If |a| == m, we can simply set the result to zero.
1371
1372 This order is intended to minimize the average path length of the
1373 comparison chain on common workloads -- the most frequent cases are
1374 that |a| != m, so we do those first.
1375 */
1376 if((mag = s_mp_cmp(a, m)) > 0) {
1377 if((res = mp_div(a, m, NULL, c)) != MP_OKAY)
1378 return res;
1379
1380 if(SIGN(c) == MP_NEG) {
1381 if((res = mp_add(c, m, c)) != MP_OKAY)
1382 return res;
1383 }
1384
1385 } else if(mag < 0) {
1386 if((res = mp_copy(a, c)) != MP_OKAY)
1387 return res;
1388
1389 if(mp_cmp_z(a) < 0) {
1390 if((res = mp_add(c, m, c)) != MP_OKAY)
1391 return res;
1392
1393 }
1394
1395 } else {
1396 mp_zero(c);
1397
1398 }
1399
1400 return MP_OKAY;
1401
1402 } /* end mp_mod() */
1403
1404 /* }}} */
1405
1406 /* {{{ mp_mod_d(a, d, c) */
1407
1408 /*
1409 mp_mod_d(a, d, c)
1410
1411 Compute c = a (mod d). Result will always be 0 <= c < d
1412 */
1413 mp_err mp_mod_d(mp_int *a, mp_digit d, mp_digit *c)
1414 {
1415 mp_err res;
1416 mp_digit rem;
1417
1418 ARGCHK(a != NULL && c != NULL, MP_BADARG);
1419
1420 if(s_mp_cmp_d(a, d) > 0) {
1421 if((res = mp_div_d(a, d, NULL, &rem)) != MP_OKAY)
1422 return res;
1423
1424 } else {
1425 if(SIGN(a) == MP_NEG)
1426 rem = d - DIGIT(a, 0);
1427 else
1428 rem = DIGIT(a, 0);
1429 }
1430
1431 if(c)
1432 *c = rem;
1433
1434 return MP_OKAY;
1435
1436 } /* end mp_mod_d() */
1437
1438 /* }}} */
1439
1440 /* {{{ mp_sqrt(a, b) */
1441
1442 /*
1443 mp_sqrt(a, b)
1444
1445 Compute the integer square root of a, and store the result in b.
1446 Uses an integer-arithmetic version of Newton's iterative linear
1447 approximation technique to determine this value; the result has the
1448 following two properties:
1449
1450 b^2 <= a
1451 (b+1)^2 >= a
1452
1453 It is a range error to pass a negative value.
1454 */
1455 mp_err mp_sqrt(mp_int *a, mp_int *b)
1456 {
1457 mp_int x, t;
1458 mp_err res;
1459
1460 ARGCHK(a != NULL && b != NULL, MP_BADARG);
1461
1462 /* Cannot take square root of a negative value */
1463 if(SIGN(a) == MP_NEG)
1464 return MP_RANGE;
1465
1466 /* Special cases for zero and one, trivial */
1467 if(mp_cmp_d(a, 0) == MP_EQ || mp_cmp_d(a, 1) == MP_EQ)
1468 return mp_copy(a, b);
1469
1470 /* Initialize the temporaries we'll use below */
1471 if((res = mp_init_size(&t, USED(a))) != MP_OKAY)
1472 return res;
1473
1474 /* Compute an initial guess for the iteration as a itself */
1475 if((res = mp_init_copy(&x, a)) != MP_OKAY)
1476 goto X;
1477
1478 s_mp_rshd(&x, (USED(&x)/2)+1);
1479 mp_add_d(&x, 1, &x);
1480
1481 for(;;) {
1482 /* t = (x * x) - a */
1483 mp_copy(&x, &t); /* can't fail, t is big enough for original x */
1484 if((res = mp_sqr(&t, &t)) != MP_OKAY ||
1485 (res = mp_sub(&t, a, &t)) != MP_OKAY)
1486 goto CLEANUP;
1487
1488 /* t = t / 2x */
1489 s_mp_mul_2(&x);
1490 if((res = mp_div(&t, &x, &t, NULL)) != MP_OKAY)
1491 goto CLEANUP;
1492 s_mp_div_2(&x);
1493
1494 /* Terminate the loop, if the quotient is zero */
1495 if(mp_cmp_z(&t) == MP_EQ)
1496 break;
1497
1498 /* x = x - t */
1499 if((res = mp_sub(&x, &t, &x)) != MP_OKAY)
1500 goto CLEANUP;
1501
1502 }
1503
1504 /* Copy result to output parameter */
1505 mp_sub_d(&x, 1, &x);
1506 s_mp_exch(&x, b);
1507
1508 CLEANUP:
1509 mp_clear(&x);
1510 X:
1511 mp_clear(&t);
1512
1513 return res;
1514
1515 } /* end mp_sqrt() */
1516
1517 /* }}} */
1518
1519 /* }}} */
1520
1521 /*------------------------------------------------------------------------*/
1522 /* {{{ Modular arithmetic */
1523
1524 #if MP_MODARITH
1525 /* {{{ mp_addmod(a, b, m, c) */
1526
1527 /*
1528 mp_addmod(a, b, m, c)
1529
1530 Compute c = (a + b) mod m
1531 */
1532
1533 mp_err mp_addmod(mp_int *a, mp_int *b, mp_int *m, mp_int *c)
1534 {
1535 mp_err res;
1536
1537 ARGCHK(a != NULL && b != NULL && m != NULL && c != NULL, MP_BADARG);
1538
1539 if((res = mp_add(a, b, c)) != MP_OKAY)
1540 return res;
1541 if((res = mp_mod(c, m, c)) != MP_OKAY)
1542 return res;
1543
1544 return MP_OKAY;
1545
1546 }
1547
1548 /* }}} */
1549
1550 /* {{{ mp_submod(a, b, m, c) */
1551
1552 /*
1553 mp_submod(a, b, m, c)
1554
1555 Compute c = (a - b) mod m
1556 */
1557
1558 mp_err mp_submod(mp_int *a, mp_int *b, mp_int *m, mp_int *c)
1559 {
1560 mp_err res;
1561
1562 ARGCHK(a != NULL && b != NULL && m != NULL && c != NULL, MP_BADARG);
1563
1564 if((res = mp_sub(a, b, c)) != MP_OKAY)
1565 return res;
1566 if((res = mp_mod(c, m, c)) != MP_OKAY)
1567 return res;
1568
1569 return MP_OKAY;
1570
1571 }
1572
1573 /* }}} */
1574
1575 /* {{{ mp_mulmod(a, b, m, c) */
1576
1577 /*
1578 mp_mulmod(a, b, m, c)
1579
1580 Compute c = (a * b) mod m
1581 */
1582
1583 mp_err mp_mulmod(mp_int *a, mp_int *b, mp_int *m, mp_int *c)
1584 {
1585 mp_err res;
1586
1587 ARGCHK(a != NULL && b != NULL && m != NULL && c != NULL, MP_BADARG);
1588
1589 if((res = mp_mul(a, b, c)) != MP_OKAY)
1590 return res;
1591 if((res = mp_mod(c, m, c)) != MP_OKAY)
1592 return res;
1593
1594 return MP_OKAY;
1595
1596 }
1597
1598 /* }}} */
1599
1600 /* {{{ mp_sqrmod(a, m, c) */
1601
1602 #if MP_SQUARE
1603 mp_err mp_sqrmod(mp_int *a, mp_int *m, mp_int *c)
1604 {
1605 mp_err res;
1606
1607 ARGCHK(a != NULL && m != NULL && c != NULL, MP_BADARG);
1608
1609 if((res = mp_sqr(a, c)) != MP_OKAY)
1610 return res;
1611 if((res = mp_mod(c, m, c)) != MP_OKAY)
1612 return res;
1613
1614 return MP_OKAY;
1615
1616 } /* end mp_sqrmod() */
1617 #endif
1618
1619 /* }}} */
1620
1621 /* {{{ mp_exptmod(a, b, m, c) */
1622
1623 /*
1624 mp_exptmod(a, b, m, c)
1625
1626 Compute c = (a ** b) mod m. Uses a standard square-and-multiply
1627 method with modular reductions at each step. (This is basically the
1628 same code as mp_expt(), except for the addition of the reductions)
1629
1630 The modular reductions are done using Barrett's algorithm (see
1631 s_mp_reduce() below for details)
1632 */
1633
1634 mp_err mp_exptmod(mp_int *a, mp_int *b, mp_int *m, mp_int *c)
1635 {
1636 mp_int s, x, mu;
1637 mp_err res;
1638 mp_digit d, *db = DIGITS(b);
1639 mp_size ub = USED(b);
1640 int dig, bit;
1641
1642 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
1643
1644 if(mp_cmp_z(b) < 0 || mp_cmp_z(m) <= 0)
1645 return MP_RANGE;
1646
1647 if((res = mp_init(&s)) != MP_OKAY)
1648 return res;
1649 if((res = mp_init_copy(&x, a)) != MP_OKAY)
1650 goto X;
1651 if((res = mp_mod(&x, m, &x)) != MP_OKAY ||
1652 (res = mp_init(&mu)) != MP_OKAY)
1653 goto MU;
1654
1655 mp_set(&s, 1);
1656
1657 /* mu = b^2k / m */
1658 s_mp_add_d(&mu, 1);
1659 s_mp_lshd(&mu, 2 * USED(m));
1660 if((res = mp_div(&mu, m, &mu, NULL)) != MP_OKAY)
1661 goto CLEANUP;
1662
1663 /* Loop over digits of b in ascending order, except highest order */
1664 for(dig = 0; dig < (ub - 1); dig++) {
1665 d = *db++;
1666
1667 /* Loop over the bits of the lower-order digits */
1668 for(bit = 0; bit < DIGIT_BIT; bit++) {
1669 if(d & 1) {
1670 if((res = s_mp_mul(&s, &x)) != MP_OKAY)
1671 goto CLEANUP;
1672 if((res = s_mp_reduce(&s, m, &mu)) != MP_OKAY)
1673 goto CLEANUP;
1674 }
1675
1676 d >>= 1;
1677
1678 if((res = s_mp_sqr(&x)) != MP_OKAY)
1679 goto CLEANUP;
1680 if((res = s_mp_reduce(&x, m, &mu)) != MP_OKAY)
1681 goto CLEANUP;
1682 }
1683 }
1684
1685 /* Now do the last digit... */
1686 d = *db;
1687
1688 while(d) {
1689 if(d & 1) {
1690 if((res = s_mp_mul(&s, &x)) != MP_OKAY)
1691 goto CLEANUP;
1692 if((res = s_mp_reduce(&s, m, &mu)) != MP_OKAY)
1693 goto CLEANUP;
1694 }
1695
1696 d >>= 1;
1697
1698 if((res = s_mp_sqr(&x)) != MP_OKAY)
1699 goto CLEANUP;
1700 if((res = s_mp_reduce(&x, m, &mu)) != MP_OKAY)
1701 goto CLEANUP;
1702 }
1703
1704 s_mp_exch(&s, c);
1705
1706 CLEANUP:
1707 mp_clear(&mu);
1708 MU:
1709 mp_clear(&x);
1710 X:
1711 mp_clear(&s);
1712
1713 return res;
1714
1715 } /* end mp_exptmod() */
1716
1717 /* }}} */
1718
1719 /* {{{ mp_exptmod_d(a, d, m, c) */
1720
1721 mp_err mp_exptmod_d(mp_int *a, mp_digit d, mp_int *m, mp_int *c)
1722 {
1723 mp_int s, x;
1724 mp_err res;
1725
1726 ARGCHK(a != NULL && c != NULL, MP_BADARG);
1727
1728 if((res = mp_init(&s)) != MP_OKAY)
1729 return res;
1730 if((res = mp_init_copy(&x, a)) != MP_OKAY)
1731 goto X;
1732
1733 mp_set(&s, 1);
1734
1735 while(d != 0) {
1736 if(d & 1) {
1737 if((res = s_mp_mul(&s, &x)) != MP_OKAY ||
1738 (res = mp_mod(&s, m, &s)) != MP_OKAY)
1739 goto CLEANUP;
1740 }
1741
1742 d /= 2;
1743
1744 if((res = s_mp_sqr(&x)) != MP_OKAY ||
1745 (res = mp_mod(&x, m, &x)) != MP_OKAY)
1746 goto CLEANUP;
1747 }
1748
1749 s_mp_exch(&s, c);
1750
1751 CLEANUP:
1752 mp_clear(&x);
1753 X:
1754 mp_clear(&s);
1755
1756 return res;
1757
1758 } /* end mp_exptmod_d() */
1759
1760 /* }}} */
1761 #endif /* if MP_MODARITH */
1762
1763 /* }}} */
1764
1765 /*------------------------------------------------------------------------*/
1766 /* {{{ Comparison functions */
1767
1768 /* {{{ mp_cmp_z(a) */
1769
1770 /*
1771 mp_cmp_z(a)
1772
1773 Compare a <=> 0. Returns <0 if a<0, 0 if a=0, >0 if a>0.
1774 */
1775
1776 int mp_cmp_z(mp_int *a)
1777 {
1778 if(SIGN(a) == MP_NEG)
1779 return MP_LT;
1780 else if(USED(a) == 1 && DIGIT(a, 0) == 0)
1781 return MP_EQ;
1782 else
1783 return MP_GT;
1784
1785 } /* end mp_cmp_z() */
1786
1787 /* }}} */
1788
1789 /* {{{ mp_cmp_d(a, d) */
1790
1791 /*
1792 mp_cmp_d(a, d)
1793
1794 Compare a <=> d. Returns <0 if a<d, 0 if a=d, >0 if a>d
1795 */
1796
1797 int mp_cmp_d(mp_int *a, mp_digit d)
1798 {
1799 ARGCHK(a != NULL, MP_EQ);
1800
1801 if(SIGN(a) == MP_NEG)
1802 return MP_LT;
1803
1804 return s_mp_cmp_d(a, d);
1805
1806 } /* end mp_cmp_d() */
1807
1808 /* }}} */
1809
1810 /* {{{ mp_cmp(a, b) */
1811
1812 int mp_cmp(mp_int *a, mp_int *b)
1813 {
1814 ARGCHK(a != NULL && b != NULL, MP_EQ);
1815
1816 if(SIGN(a) == SIGN(b)) {
1817 int mag;
1818
1819 if((mag = s_mp_cmp(a, b)) == MP_EQ)
1820 return MP_EQ;
1821
1822 if(SIGN(a) == MP_ZPOS)
1823 return mag;
1824 else
1825 return -mag;
1826
1827 } else if(SIGN(a) == MP_ZPOS) {
1828 return MP_GT;
1829 } else {
1830 return MP_LT;
1831 }
1832
1833 } /* end mp_cmp() */
1834
1835 /* }}} */
1836
1837 /* {{{ mp_cmp_mag(a, b) */
1838
1839 /*
1840 mp_cmp_mag(a, b)
1841
1842 Compares |a| <=> |b|, and returns an appropriate comparison result
1843 */
1844
1845 int mp_cmp_mag(mp_int *a, mp_int *b)
1846 {
1847 ARGCHK(a != NULL && b != NULL, MP_EQ);
1848
1849 return s_mp_cmp(a, b);
1850
1851 } /* end mp_cmp_mag() */
1852
1853 /* }}} */
1854
1855 /* {{{ mp_cmp_int(a, z) */
1856
1857 /*
1858 This just converts z to an mp_int, and uses the existing comparison
1859 routines. This is sort of inefficient, but it's not clear to me how
1860 frequently this wil get used anyway. For small positive constants,
1861 you can always use mp_cmp_d(), and for zero, there is mp_cmp_z().
1862 */
1863 int mp_cmp_int(mp_int *a, long z)
1864 {
1865 mp_int tmp;
1866 int out;
1867
1868 ARGCHK(a != NULL, MP_EQ);
1869
1870 mp_init(&tmp); mp_set_int(&tmp, z);
1871 out = mp_cmp(a, &tmp);
1872 mp_clear(&tmp);
1873
1874 return out;
1875
1876 } /* end mp_cmp_int() */
1877
1878 /* }}} */
1879
1880 /* {{{ mp_isodd(a) */
1881
1882 /*
1883 mp_isodd(a)
1884
1885 Returns a true (non-zero) value if a is odd, false (zero) otherwise.
1886 */
1887 int mp_isodd(mp_int *a)
1888 {
1889 ARGCHK(a != NULL, 0);
1890
1891 return (DIGIT(a, 0) & 1);
1892
1893 } /* end mp_isodd() */
1894
1895 /* }}} */
1896
1897 /* {{{ mp_iseven(a) */
1898
1899 int mp_iseven(mp_int *a)
1900 {
1901 return !mp_isodd(a);
1902
1903 } /* end mp_iseven() */
1904
1905 /* }}} */
1906
1907 /* }}} */
1908
1909 /*------------------------------------------------------------------------*/
1910 /* {{{ Number theoretic functions */
1911
1912 #if MP_NUMTH
1913 /* {{{ mp_gcd(a, b, c) */
1914
1915 /*
1916 Like the old mp_gcd() function, except computes the GCD using the
1917 binary algorithm due to Josef Stein in 1961 (via Knuth).
1918 */
1919 mp_err mp_gcd(mp_int *a, mp_int *b, mp_int *c)
1920 {
1921 mp_err res;
1922 mp_int u, v, t;
1923 mp_size k = 0;
1924
1925 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
1926
1927 if(mp_cmp_z(a) == MP_EQ && mp_cmp_z(b) == MP_EQ)
1928 return MP_RANGE;
1929 if(mp_cmp_z(a) == MP_EQ) {
1930 return mp_copy(b, c);
1931 } else if(mp_cmp_z(b) == MP_EQ) {
1932 return mp_copy(a, c);
1933 }
1934
1935 if((res = mp_init(&t)) != MP_OKAY)
1936 return res;
1937 if((res = mp_init_copy(&u, a)) != MP_OKAY)
1938 goto U;
1939 if((res = mp_init_copy(&v, b)) != MP_OKAY)
1940 goto V;
1941
1942 SIGN(&u) = MP_ZPOS;
1943 SIGN(&v) = MP_ZPOS;
1944
1945 /* Divide out common factors of 2 until at least 1 of a, b is even */
1946 while(mp_iseven(&u) && mp_iseven(&v)) {
1947 s_mp_div_2(&u);
1948 s_mp_div_2(&v);
1949 ++k;
1950 }
1951
1952 /* Initialize t */
1953 if(mp_isodd(&u)) {
1954 if((res = mp_copy(&v, &t)) != MP_OKAY)
1955 goto CLEANUP;
1956
1957 /* t = -v */
1958 if(SIGN(&v) == MP_ZPOS)
1959 SIGN(&t) = MP_NEG;
1960 else
1961 SIGN(&t) = MP_ZPOS;
1962
1963 } else {
1964 if((res = mp_copy(&u, &t)) != MP_OKAY)
1965 goto CLEANUP;
1966
1967 }
1968
1969 for(;;) {
1970 while(mp_iseven(&t)) {
1971 s_mp_div_2(&t);
1972 }
1973
1974 if(mp_cmp_z(&t) == MP_GT) {
1975 if((res = mp_copy(&t, &u)) != MP_OKAY)
1976 goto CLEANUP;
1977
1978 } else {
1979 if((res = mp_copy(&t, &v)) != MP_OKAY)
1980 goto CLEANUP;
1981
1982 /* v = -t */
1983 if(SIGN(&t) == MP_ZPOS)
1984 SIGN(&v) = MP_NEG;
1985 else
1986 SIGN(&v) = MP_ZPOS;
1987 }
1988
1989 if((res = mp_sub(&u, &v, &t)) != MP_OKAY)
1990 goto CLEANUP;
1991
1992 if(s_mp_cmp_d(&t, 0) == MP_EQ)
1993 break;
1994 }
1995
1996 s_mp_2expt(&v, k); /* v = 2^k */
1997 res = mp_mul(&u, &v, c); /* c = u * v */
1998
1999 CLEANUP:
2000 mp_clear(&v);
2001 V:
2002 mp_clear(&u);
2003 U:
2004 mp_clear(&t);
2005
2006 return res;
2007
2008 } /* end mp_bgcd() */
2009
2010 /* }}} */
2011
2012 /* {{{ mp_lcm(a, b, c) */
2013
2014 /* We compute the least common multiple using the rule:
2015
2016 ab = [a, b](a, b)
2017
2018 ... by computing the product, and dividing out the gcd.
2019 */
2020
2021 mp_err mp_lcm(mp_int *a, mp_int *b, mp_int *c)
2022 {
2023 mp_int gcd, prod;
2024 mp_err res;
2025
2026 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
2027
2028 /* Set up temporaries */
2029 if((res = mp_init(&gcd)) != MP_OKAY)
2030 return res;
2031 if((res = mp_init(&prod)) != MP_OKAY)
2032 goto GCD;
2033
2034 if((res = mp_mul(a, b, &prod)) != MP_OKAY)
2035 goto CLEANUP;
2036 if((res = mp_gcd(a, b, &gcd)) != MP_OKAY)
2037 goto CLEANUP;
2038
2039 res = mp_div(&prod, &gcd, c, NULL);
2040
2041 CLEANUP:
2042 mp_clear(&prod);
2043 GCD:
2044 mp_clear(&gcd);
2045
2046 return res;
2047
2048 } /* end mp_lcm() */
2049
2050 /* }}} */
2051
2052 /* {{{ mp_xgcd(a, b, g, x, y) */
2053
2054 /*
2055 mp_xgcd(a, b, g, x, y)
2056
2057 Compute g = (a, b) and values x and y satisfying Bezout's identity
2058 (that is, ax + by = g). This uses the extended binary GCD algorithm
2059 based on the Stein algorithm used for mp_gcd()
2060 */
2061
2062 mp_err mp_xgcd(mp_int *a, mp_int *b, mp_int *g, mp_int *x, mp_int *y)
2063 {
2064 mp_int gx, xc, yc, u, v, A, B, C, D;
2065 mp_int *clean[9];
2066 mp_err res;
2067 int last = -1;
2068
2069 if(mp_cmp_z(b) == 0)
2070 return MP_RANGE;
2071
2072 /* Initialize all these variables we need */
2073 if((res = mp_init(&u)) != MP_OKAY) goto CLEANUP;
2074 clean[++last] = &u;
2075 if((res = mp_init(&v)) != MP_OKAY) goto CLEANUP;
2076 clean[++last] = &v;
2077 if((res = mp_init(&gx)) != MP_OKAY) goto CLEANUP;
2078 clean[++last] = &gx;
2079 if((res = mp_init(&A)) != MP_OKAY) goto CLEANUP;
2080 clean[++last] = &A;
2081 if((res = mp_init(&B)) != MP_OKAY) goto CLEANUP;
2082 clean[++last] = &B;
2083 if((res = mp_init(&C)) != MP_OKAY) goto CLEANUP;
2084 clean[++last] = &C;
2085 if((res = mp_init(&D)) != MP_OKAY) goto CLEANUP;
2086 clean[++last] = &D;
2087 if((res = mp_init_copy(&xc, a)) != MP_OKAY) goto CLEANUP;
2088 clean[++last] = &xc;
2089 mp_abs(&xc, &xc);
2090 if((res = mp_init_copy(&yc, b)) != MP_OKAY) goto CLEANUP;
2091 clean[++last] = &yc;
2092 mp_abs(&yc, &yc);
2093
2094 mp_set(&gx, 1);
2095
2096 /* Divide by two until at least one of them is even */
2097 while(mp_iseven(&xc) && mp_iseven(&yc)) {
2098 s_mp_div_2(&xc);
2099 s_mp_div_2(&yc);
2100 if((res = s_mp_mul_2(&gx)) != MP_OKAY)
2101 goto CLEANUP;
2102 }
2103
2104 mp_copy(&xc, &u);
2105 mp_copy(&yc, &v);
2106 mp_set(&A, 1); mp_set(&D, 1);
2107
2108 /* Loop through binary GCD algorithm */
2109 for(;;) {
2110 while(mp_iseven(&u)) {
2111 s_mp_div_2(&u);
2112
2113 if(mp_iseven(&A) && mp_iseven(&B)) {
2114 s_mp_div_2(&A); s_mp_div_2(&B);
2115 } else {
2116 if((res = mp_add(&A, &yc, &A)) != MP_OKAY) goto CLEANUP;
2117 s_mp_div_2(&A);
2118 if((res = mp_sub(&B, &xc, &B)) != MP_OKAY) goto CLEANUP;
2119 s_mp_div_2(&B);
2120 }
2121 }
2122
2123 while(mp_iseven(&v)) {
2124 s_mp_div_2(&v);
2125
2126 if(mp_iseven(&C) && mp_iseven(&D)) {
2127 s_mp_div_2(&C); s_mp_div_2(&D);
2128 } else {
2129 if((res = mp_add(&C, &yc, &C)) != MP_OKAY) goto CLEANUP;
2130 s_mp_div_2(&C);
2131 if((res = mp_sub(&D, &xc, &D)) != MP_OKAY) goto CLEANUP;
2132 s_mp_div_2(&D);
2133 }
2134 }
2135
2136 if(mp_cmp(&u, &v) >= 0) {
2137 if((res = mp_sub(&u, &v, &u)) != MP_OKAY) goto CLEANUP;
2138 if((res = mp_sub(&A, &C, &A)) != MP_OKAY) goto CLEANUP;
2139 if((res = mp_sub(&B, &D, &B)) != MP_OKAY) goto CLEANUP;
2140
2141 } else {
2142 if((res = mp_sub(&v, &u, &v)) != MP_OKAY) goto CLEANUP;
2143 if((res = mp_sub(&C, &A, &C)) != MP_OKAY) goto CLEANUP;
2144 if((res = mp_sub(&D, &B, &D)) != MP_OKAY) goto CLEANUP;
2145
2146 }
2147
2148 /* If we're done, copy results to output */
2149 if(mp_cmp_z(&u) == 0) {
2150 if(x)
2151 if((res = mp_copy(&C, x)) != MP_OKAY) goto CLEANUP;
2152
2153 if(y)
2154 if((res = mp_copy(&D, y)) != MP_OKAY) goto CLEANUP;
2155
2156 if(g)
2157 if((res = mp_mul(&gx, &v, g)) != MP_OKAY) goto CLEANUP;
2158
2159 break;
2160 }
2161 }
2162
2163 CLEANUP:
2164 while(last >= 0)
2165 mp_clear(clean[last--]);
2166
2167 return res;
2168
2169 } /* end mp_xgcd() */
2170
2171 /* }}} */
2172
2173 /* {{{ mp_invmod(a, m, c) */
2174
2175 /*
2176 mp_invmod(a, m, c)
2177
2178 Compute c = a^-1 (mod m), if there is an inverse for a (mod m).
2179 This is equivalent to the question of whether (a, m) = 1. If not,
2180 MP_UNDEF is returned, and there is no inverse.
2181 */
2182
2183 mp_err mp_invmod(mp_int *a, mp_int *m, mp_int *c)
2184 {
2185 mp_int g, x;
2186 mp_err res;
2187
2188 ARGCHK(a && m && c, MP_BADARG);
2189
2190 if(mp_cmp_z(a) == 0 || mp_cmp_z(m) == 0)
2191 return MP_RANGE;
2192
2193 if((res = mp_init(&g)) != MP_OKAY)
2194 return res;
2195 if((res = mp_init(&x)) != MP_OKAY)
2196 goto X;
2197
2198 if((res = mp_xgcd(a, m, &g, &x, NULL)) != MP_OKAY)
2199 goto CLEANUP;
2200
2201 if(mp_cmp_d(&g, 1) != MP_EQ) {
2202 res = MP_UNDEF;
2203 goto CLEANUP;
2204 }
2205
2206 res = mp_mod(&x, m, c);
2207 SIGN(c) = SIGN(a);
2208
2209 CLEANUP:
2210 mp_clear(&x);
2211 X:
2212 mp_clear(&g);
2213
2214 return res;
2215
2216 } /* end mp_invmod() */
2217
2218 /* }}} */
2219 #endif /* if MP_NUMTH */
2220
2221 /* }}} */
2222
2223 /*------------------------------------------------------------------------*/
2224 /* {{{ mp_print(mp, ofp) */
2225
2226 #if MP_IOFUNC
2227 /*
2228 mp_print(mp, ofp)
2229
2230 Print a textual representation of the given mp_int on the output
2231 stream 'ofp'. Output is generated using the internal radix.
2232 */
2233
2234 void mp_print(mp_int *mp, FILE *ofp)
2235 {
2236 int ix;
2237
2238 if(mp == NULL || ofp == NULL)
2239 return;
2240
2241 fputc((SIGN(mp) == MP_NEG) ? '-' : '+', ofp);
2242
2243 for(ix = USED(mp) - 1; ix >= 0; ix--) {
2244 fprintf(ofp, DIGIT_FMT, DIGIT(mp, ix));
2245 }
2246
2247 } /* end mp_print() */
2248
2249 #endif /* if MP_IOFUNC */
2250
2251 /* }}} */
2252
2253 /*------------------------------------------------------------------------*/
2254 /* {{{ More I/O Functions */
2255
2256 /* {{{ mp_read_signed_bin(mp, str, len) */
2257
2258 /*
2259 mp_read_signed_bin(mp, str, len)
2260
2261 Read in a raw value (base 256) into the given mp_int
2262 */
2263
2264 mp_err mp_read_signed_bin(mp_int *mp, unsigned char *str, int len)
2265 {
2266 mp_err res;
2267
2268 ARGCHK(mp != NULL && str != NULL && len > 0, MP_BADARG);
2269
2270 if((res = mp_read_unsigned_bin(mp, str + 1, len - 1)) == MP_OKAY) {
2271 /* Get sign from first byte */
2272 if(str[0])
2273 SIGN(mp) = MP_NEG;
2274 else
2275 SIGN(mp) = MP_ZPOS;
2276 }
2277
2278 return res;
2279
2280 } /* end mp_read_signed_bin() */
2281
2282 /* }}} */
2283
2284 /* {{{ mp_signed_bin_size(mp) */
2285
2286 int mp_signed_bin_size(mp_int *mp)
2287 {
2288 ARGCHK(mp != NULL, 0);
2289
2290 return mp_unsigned_bin_size(mp) + 1;
2291
2292 } /* end mp_signed_bin_size() */
2293
2294 /* }}} */
2295
2296 /* {{{ mp_to_signed_bin(mp, str) */
2297
2298 mp_err mp_to_signed_bin(mp_int *mp, unsigned char *str)
2299 {
2300 ARGCHK(mp != NULL && str != NULL, MP_BADARG);
2301
2302 /* Caller responsible for allocating enough memory (use mp_raw_size(mp)) */
2303 str[0] = (char)SIGN(mp);
2304
2305 return mp_to_unsigned_bin(mp, str + 1);
2306
2307 } /* end mp_to_signed_bin() */
2308
2309 /* }}} */
2310
2311 /* {{{ mp_read_unsigned_bin(mp, str, len) */
2312
2313 /*
2314 mp_read_unsigned_bin(mp, str, len)
2315
2316 Read in an unsigned value (base 256) into the given mp_int
2317 */
2318
2319 mp_err mp_read_unsigned_bin(mp_int *mp, unsigned char *str, int len)
2320 {
2321 int ix;
2322 mp_err res;
2323
2324 ARGCHK(mp != NULL && str != NULL && len > 0, MP_BADARG);
2325
2326 mp_zero(mp);
2327
2328 for(ix = 0; ix < len; ix++) {
2329 if((res = s_mp_mul_2d(mp, CHAR_BIT)) != MP_OKAY)
2330 return res;
2331
2332 if((res = mp_add_d(mp, str[ix], mp)) != MP_OKAY)
2333 return res;
2334 }
2335
2336 return MP_OKAY;
2337
2338 } /* end mp_read_unsigned_bin() */
2339
2340 /* }}} */
2341
2342 /* {{{ mp_unsigned_bin_size(mp) */
2343
2344 int mp_unsigned_bin_size(mp_int *mp)
2345 {
2346 mp_digit topdig;
2347 int count;
2348
2349 ARGCHK(mp != NULL, 0);
2350
2351 /* Special case for the value zero */
2352 if(USED(mp) == 1 && DIGIT(mp, 0) == 0)
2353 return 1;
2354
2355 count = (USED(mp) - 1) * sizeof(mp_digit);
2356 topdig = DIGIT(mp, USED(mp) - 1);
2357
2358 while(topdig != 0) {
2359 ++count;
2360 topdig >>= CHAR_BIT;
2361 }
2362
2363 return count;
2364
2365 } /* end mp_unsigned_bin_size() */
2366
2367 /* }}} */
2368
2369 /* {{{ mp_to_unsigned_bin(mp, str) */
2370
2371 mp_err mp_to_unsigned_bin(mp_int *mp, unsigned char *str)
2372 {
2373 mp_digit *dp, *end, d;
2374 unsigned char *spos;
2375
2376 ARGCHK(mp != NULL && str != NULL, MP_BADARG);
2377
2378 dp = DIGITS(mp);
2379 end = dp + USED(mp) - 1;
2380 spos = str;
2381
2382 /* Special case for zero, quick test */
2383 if(dp == end && *dp == 0) {
2384 *str = '\0';
2385 return MP_OKAY;
2386 }
2387
2388 /* Generate digits in reverse order */
2389 while(dp < end) {
2390 int ix;
2391
2392 d = *dp;
2393 for(ix = 0; ix < sizeof(mp_digit); ++ix) {
2394 *spos = d & UCHAR_MAX;
2395 d >>= CHAR_BIT;
2396 ++spos;
2397 }
2398
2399 ++dp;
2400 }
2401
2402 /* Now handle last digit specially, high order zeroes are not written */
2403 d = *end;
2404 while(d != 0) {
2405 *spos = d & UCHAR_MAX;
2406 d >>= CHAR_BIT;
2407 ++spos;
2408 }
2409
2410 /* Reverse everything to get digits in the correct order */
2411 while(--spos > str) {
2412 unsigned char t = *str;
2413 *str = *spos;
2414 *spos = t;
2415
2416 ++str;
2417 }
2418
2419 return MP_OKAY;
2420
2421 } /* end mp_to_unsigned_bin() */
2422
2423 /* }}} */
2424
2425 /* {{{ mp_count_bits(mp) */
2426
2427 int mp_count_bits(mp_int *mp)
2428 {
2429 int len;
2430 mp_digit d;
2431
2432 ARGCHK(mp != NULL, MP_BADARG);
2433
2434 len = DIGIT_BIT * (USED(mp) - 1);
2435 d = DIGIT(mp, USED(mp) - 1);
2436
2437 while(d != 0) {
2438 ++len;
2439 d >>= 1;
2440 }
2441
2442 return len;
2443
2444 } /* end mp_count_bits() */
2445
2446 /* }}} */
2447
2448 /* {{{ mp_read_radix(mp, str, radix) */
2449
2450 /*
2451 mp_read_radix(mp, str, radix)
2452
2453 Read an integer from the given string, and set mp to the resulting
2454 value. The input is presumed to be in base 10. Leading non-digit
2455 characters are ignored, and the function reads until a non-digit
2456 character or the end of the string.
2457 */
2458
2459 mp_err mp_read_radix(mp_int *mp, unsigned char *str, int radix)
2460 {
2461 int ix = 0, val = 0;
2462 mp_err res;
2463 mp_sign sig = MP_ZPOS;
2464
2465 ARGCHK(mp != NULL && str != NULL && radix >= 2 && radix <= MAX_RADIX,
2466 MP_BADARG);
2467
2468 mp_zero(mp);
2469
2470 /* Skip leading non-digit characters until a digit or '-' or '+' */
2471 while(str[ix] &&
2472 (s_mp_tovalue(str[ix], radix) < 0) &&
2473 str[ix] != '-' &&
2474 str[ix] != '+') {
2475 ++ix;
2476 }
2477
2478 if(str[ix] == '-') {
2479 sig = MP_NEG;
2480 ++ix;
2481 } else if(str[ix] == '+') {
2482 sig = MP_ZPOS; /* this is the default anyway... */
2483 ++ix;
2484 }
2485
2486 while((val = s_mp_tovalue(str[ix], radix)) >= 0) {
2487 if((res = s_mp_mul_d(mp, radix)) != MP_OKAY)
2488 return res;
2489 if((res = s_mp_add_d(mp, val)) != MP_OKAY)
2490 return res;
2491 ++ix;
2492 }
2493
2494 if(s_mp_cmp_d(mp, 0) == MP_EQ)
2495 SIGN(mp) = MP_ZPOS;
2496 else
2497 SIGN(mp) = sig;
2498
2499 return MP_OKAY;
2500
2501 } /* end mp_read_radix() */
2502
2503 /* }}} */
2504
2505 /* {{{ mp_radix_size(mp, radix) */
2506
2507 int mp_radix_size(mp_int *mp, int radix)
2508 {
2509 int len;
2510 ARGCHK(mp != NULL, 0);
2511
2512 len = s_mp_outlen(mp_count_bits(mp), radix) + 1; /* for NUL terminator */
2513
2514 if(mp_cmp_z(mp) < 0)
2515 ++len; /* for sign */
2516
2517 return len;
2518
2519 } /* end mp_radix_size() */
2520
2521 /* }}} */
2522
2523 /* {{{ mp_value_radix_size(num, qty, radix) */
2524
2525 /* num = number of digits
2526 qty = number of bits per digit
2527 radix = target base
2528
2529 Return the number of digits in the specified radix that would be
2530 needed to express 'num' digits of 'qty' bits each.
2531 */
2532 int mp_value_radix_size(int num, int qty, int radix)
2533 {
2534 ARGCHK(num >= 0 && qty > 0 && radix >= 2 && radix <= MAX_RADIX, 0);
2535
2536 return s_mp_outlen(num * qty, radix);
2537
2538 } /* end mp_value_radix_size() */
2539
2540 /* }}} */
2541
2542 /* {{{ mp_toradix(mp, str, radix) */
2543
2544 mp_err mp_toradix(mp_int *mp, unsigned char *str, int radix)
2545 {
2546 int ix, pos = 0;
2547
2548 ARGCHK(mp != NULL && str != NULL, MP_BADARG);
2549 ARGCHK(radix > 1 && radix <= MAX_RADIX, MP_RANGE);
2550
2551 if(mp_cmp_z(mp) == MP_EQ) {
2552 str[0] = '0';
2553 str[1] = '\0';
2554 } else {
2555 mp_err res;
2556 mp_int tmp;
2557 mp_sign sgn;
2558 mp_digit rem, rdx = (mp_digit)radix;
2559 char ch;
2560
2561 if((res = mp_init_copy(&tmp, mp)) != MP_OKAY)
2562 return res;
2563
2564 /* Save sign for later, and take absolute value */
2565 sgn = SIGN(&tmp); SIGN(&tmp) = MP_ZPOS;
2566
2567 /* Generate output digits in reverse order */
2568 while(mp_cmp_z(&tmp) != 0) {
2569 if((res = s_mp_div_d(&tmp, rdx, &rem)) != MP_OKAY) {
2570 mp_clear(&tmp);
2571 return res;
2572 }
2573
2574 /* Generate digits, use capital letters */
2575 ch = s_mp_todigit(rem, radix, 0);
2576
2577 str[pos++] = ch;
2578 }
2579
2580 /* Add - sign if original value was negative */
2581 if(sgn == MP_NEG)
2582 str[pos++] = '-';
2583
2584 /* Add trailing NUL to end the string */
2585 str[pos--] = '\0';
2586
2587 /* Reverse the digits and sign indicator */
2588 ix = 0;
2589 while(ix < pos) {
2590 char tmp = str[ix];
2591
2592 str[ix] = str[pos];
2593 str[pos] = tmp;
2594 ++ix;
2595 --pos;
2596 }
2597
2598 mp_clear(&tmp);
2599 }
2600
2601 return MP_OKAY;
2602
2603 } /* end mp_toradix() */
2604
2605 /* }}} */
2606
2607 /* {{{ mp_char2value(ch, r) */
2608
2609 int mp_char2value(char ch, int r)
2610 {
2611 return s_mp_tovalue(ch, r);
2612
2613 } /* end mp_tovalue() */
2614
2615 /* }}} */
2616
2617 /* }}} */
2618
2619 /* {{{ mp_strerror(ec) */
2620
2621 /*
2622 mp_strerror(ec)
2623
2624 Return a string describing the meaning of error code 'ec'. The
2625 string returned is allocated in static memory, so the caller should
2626 not attempt to modify or free the memory associated with this
2627 string.
2628 */
2629 const char *mp_strerror(mp_err ec)
2630 {
2631 int aec = (ec < 0) ? -ec : ec;
2632
2633 /* Code values are negative, so the senses of these comparisons
2634 are accurate */
2635 if(ec < MP_LAST_CODE || ec > MP_OKAY) {
2636 return mp_err_string[0]; /* unknown error code */
2637 } else {
2638 return mp_err_string[aec + 1];
2639 }
2640
2641 } /* end mp_strerror() */
2642
2643 /* }}} */
2644
2645 /*========================================================================*/
2646 /*------------------------------------------------------------------------*/
2647 /* Static function definitions (internal use only) */
2648
2649 /* {{{ Memory management */
2650
2651 /* {{{ s_mp_grow(mp, min) */
2652
2653 /* Make sure there are at least 'min' digits allocated to mp */
2654 mp_err s_mp_grow(mp_int *mp, mp_size min)
2655 {
2656 if(min > ALLOC(mp)) {
2657 mp_digit *tmp;
2658
2659 /* Set min to next nearest default precision block size */
2660 min = ((min + (s_mp_defprec - 1)) / s_mp_defprec) * s_mp_defprec;
2661
2662 if((tmp = s_mp_alloc(min, sizeof(mp_digit))) == NULL)
2663 return MP_MEM;
2664
2665 s_mp_copy(DIGITS(mp), tmp, USED(mp));
2666
2667 #if MP_CRYPTO
2668 s_mp_setz(DIGITS(mp), ALLOC(mp));
2669 #endif
2670 s_mp_free(DIGITS(mp));
2671 DIGITS(mp) = tmp;
2672 ALLOC(mp) = min;
2673 }
2674
2675 return MP_OKAY;
2676
2677 } /* end s_mp_grow() */
2678
2679 /* }}} */
2680
2681 /* {{{ s_mp_pad(mp, min) */
2682
2683 /* Make sure the used size of mp is at least 'min', growing if needed */
2684 mp_err s_mp_pad(mp_int *mp, mp_size min)
2685 {
2686 if(min > USED(mp)) {
2687 mp_err res;
2688
2689 /* Make sure there is room to increase precision */
2690 if(min > ALLOC(mp) && (res = s_mp_grow(mp, min)) != MP_OKAY)
2691 return res;
2692
2693 /* Increase precision; should already be 0-filled */
2694 USED(mp) = min;
2695 }
2696
2697 return MP_OKAY;
2698
2699 } /* end s_mp_pad() */
2700
2701 /* }}} */
2702
2703 /* {{{ s_mp_setz(dp, count) */
2704
2705 #if MP_MACRO == 0
2706 /* Set 'count' digits pointed to by dp to be zeroes */
2707 void s_mp_setz(mp_digit *dp, mp_size count)
2708 {
2709 #if MP_MEMSET == 0
2710 int ix;
2711
2712 for(ix = 0; ix < count; ix++)
2713 dp[ix] = 0;
2714 #else
2715 memset(dp, 0, count * sizeof(mp_digit));
2716 #endif
2717
2718 } /* end s_mp_setz() */
2719 #endif
2720
2721 /* }}} */
2722
2723 /* {{{ s_mp_copy(sp, dp, count) */
2724
2725 #if MP_MACRO == 0
2726 /* Copy 'count' digits from sp to dp */
2727 void s_mp_copy(mp_digit *sp, mp_digit *dp, mp_size count)
2728 {
2729 #if MP_MEMCPY == 0
2730 int ix;
2731
2732 for(ix = 0; ix < count; ix++)
2733 dp[ix] = sp[ix];
2734 #else
2735 memcpy(dp, sp, count * sizeof(mp_digit));
2736 #endif
2737
2738 } /* end s_mp_copy() */
2739 #endif
2740
2741 /* }}} */
2742
2743 /* {{{ s_mp_alloc(nb, ni) */
2744
2745 #if MP_MACRO == 0
2746 /* Allocate ni records of nb bytes each, and return a pointer to that */
2747 void *s_mp_alloc(size_t nb, size_t ni)
2748 {
2749 return calloc(nb, ni);
2750
2751 } /* end s_mp_alloc() */
2752 #endif
2753
2754 /* }}} */
2755
2756 /* {{{ s_mp_free(ptr) */
2757
2758 #if MP_MACRO == 0
2759 /* Free the memory pointed to by ptr */
2760 void s_mp_free(void *ptr)
2761 {
2762 if(ptr)
2763 free(ptr);
2764
2765 } /* end s_mp_free() */
2766 #endif
2767
2768 /* }}} */
2769
2770 /* {{{ s_mp_clamp(mp) */
2771
2772 /* Remove leading zeroes from the given value */
2773 void s_mp_clamp(mp_int *mp)
2774 {
2775 mp_size du = USED(mp);
2776 mp_digit *zp = DIGITS(mp) + du - 1;
2777
2778 while(du > 1 && !*zp--)
2779 --du;
2780
2781 USED(mp) = du;
2782
2783 } /* end s_mp_clamp() */
2784
2785
2786 /* }}} */
2787
2788 /* {{{ s_mp_exch(a, b) */
2789
2790 /* Exchange the data for a and b; (b, a) = (a, b) */
2791 void s_mp_exch(mp_int *a, mp_int *b)
2792 {
2793 mp_int tmp;
2794
2795 tmp = *a;
2796 *a = *b;
2797 *b = tmp;
2798
2799 } /* end s_mp_exch() */
2800
2801 /* }}} */
2802
2803 /* }}} */
2804
2805 /* {{{ Arithmetic helpers */
2806
2807 /* {{{ s_mp_lshd(mp, p) */
2808
2809 /*
2810 Shift mp leftward by p digits, growing if needed, and zero-filling
2811 the in-shifted digits at the right end. This is a convenient
2812 alternative to multiplication by powers of the radix
2813 */
2814
2815 mp_err s_mp_lshd(mp_int *mp, mp_size p)
2816 {
2817 mp_err res;
2818 mp_size pos;
2819 mp_digit *dp;
2820 int ix;
2821
2822 if(p == 0)
2823 return MP_OKAY;
2824
2825 if((res = s_mp_pad(mp, USED(mp) + p)) != MP_OKAY)
2826 return res;
2827
2828 pos = USED(mp) - 1;
2829 dp = DIGITS(mp);
2830
2831 /* Shift all the significant figures over as needed */
2832 for(ix = pos - p; ix >= 0; ix--)
2833 dp[ix + p] = dp[ix];
2834
2835 /* Fill the bottom digits with zeroes */
2836 for(ix = 0; ix < p; ix++)
2837 dp[ix] = 0;
2838
2839 return MP_OKAY;
2840
2841 } /* end s_mp_lshd() */
2842
2843 /* }}} */
2844
2845 /* {{{ s_mp_rshd(mp, p) */
2846
2847 /*
2848 Shift mp rightward by p digits. Maintains the invariant that
2849 digits above the precision are all zero. Digits shifted off the
2850 end are lost. Cannot fail.
2851 */
2852
2853 void s_mp_rshd(mp_int *mp, mp_size p)
2854 {
2855 mp_size ix;
2856 mp_digit *dp;
2857
2858 if(p == 0)
2859 return;
2860
2861 /* Shortcut when all digits are to be shifted off */
2862 if(p >= USED(mp)) {
2863 s_mp_setz(DIGITS(mp), ALLOC(mp));
2864 USED(mp) = 1;
2865 SIGN(mp) = MP_ZPOS;
2866 return;
2867 }
2868
2869 /* Shift all the significant figures over as needed */
2870 dp = DIGITS(mp);
2871 for(ix = p; ix < USED(mp); ix++)
2872 dp[ix - p] = dp[ix];
2873
2874 /* Fill the top digits with zeroes */
2875 ix -= p;
2876 while(ix < USED(mp))
2877 dp[ix++] = 0;
2878
2879 /* Strip off any leading zeroes */
2880 s_mp_clamp(mp);
2881
2882 } /* end s_mp_rshd() */
2883
2884 /* }}} */
2885
2886 /* {{{ s_mp_div_2(mp) */
2887
2888 /* Divide by two -- take advantage of radix properties to do it fast */
2889 void s_mp_div_2(mp_int *mp)
2890 {
2891 s_mp_div_2d(mp, 1);
2892
2893 } /* end s_mp_div_2() */
2894
2895 /* }}} */
2896
2897 /* {{{ s_mp_mul_2(mp) */
2898
2899 mp_err s_mp_mul_2(mp_int *mp)
2900 {
2901 int ix;
2902 mp_digit kin = 0, kout, *dp = DIGITS(mp);
2903 mp_err res;
2904
2905 /* Shift digits leftward by 1 bit */
2906 for(ix = 0; ix < USED(mp); ix++) {
2907 kout = (dp[ix] >> (DIGIT_BIT - 1)) & 1;
2908 dp[ix] = (dp[ix] << 1) | kin;
2909
2910 kin = kout;
2911 }
2912
2913 /* Deal with rollover from last digit */
2914 if(kin) {
2915 if(ix >= ALLOC(mp)) {
2916 if((res = s_mp_grow(mp, ALLOC(mp) + 1)) != MP_OKAY)
2917 return res;
2918 dp = DIGITS(mp);
2919 }
2920
2921 dp[ix] = kin;
2922 USED(mp) += 1;
2923 }
2924
2925 return MP_OKAY;
2926
2927 } /* end s_mp_mul_2() */
2928
2929 /* }}} */
2930
2931 /* {{{ s_mp_mod_2d(mp, d) */
2932
2933 /*
2934 Remainder the integer by 2^d, where d is a number of bits. This
2935 amounts to a bitwise AND of the value, and does not require the full
2936 division code
2937 */
2938 void s_mp_mod_2d(mp_int *mp, mp_digit d)
2939 {
2940 unsigned int ndig = (d / DIGIT_BIT), nbit = (d % DIGIT_BIT);
2941 unsigned int ix;
2942 mp_digit dmask, *dp = DIGITS(mp);
2943
2944 if(ndig >= USED(mp))
2945 return;
2946
2947 /* Flush all the bits above 2^d in its digit */
2948 dmask = (1 << nbit) - 1;
2949 dp[ndig] &= dmask;
2950
2951 /* Flush all digits above the one with 2^d in it */
2952 for(ix = ndig + 1; ix < USED(mp); ix++)
2953 dp[ix] = 0;
2954
2955 s_mp_clamp(mp);
2956
2957 } /* end s_mp_mod_2d() */
2958
2959 /* }}} */
2960
2961 /* {{{ s_mp_mul_2d(mp, d) */
2962
2963 /*
2964 Multiply by the integer 2^d, where d is a number of bits. This
2965 amounts to a bitwise shift of the value, and does not require the
2966 full multiplication code.
2967 */
2968 mp_err s_mp_mul_2d(mp_int *mp, mp_digit d)
2969 {
2970 mp_err res;
2971 mp_digit save, next, mask, *dp;
2972 mp_size used;
2973 int ix;
2974
2975 if((res = s_mp_lshd(mp, d / DIGIT_BIT)) != MP_OKAY)
2976 return res;
2977
2978 dp = DIGITS(mp); used = USED(mp);
2979 d %= DIGIT_BIT;
2980
2981 mask = (1 << d) - 1;
2982
2983 /* If the shift requires another digit, make sure we've got one to
2984 work with */
2985 if((dp[used - 1] >> (DIGIT_BIT - d)) & mask) {
2986 if((res = s_mp_grow(mp, used + 1)) != MP_OKAY)
2987 return res;
2988 dp = DIGITS(mp);
2989 }
2990
2991 /* Do the shifting... */
2992 save = 0;
2993 for(ix = 0; ix < used; ix++) {
2994 next = (dp[ix] >> (DIGIT_BIT - d)) & mask;
2995 dp[ix] = (dp[ix] << d) | save;
2996 save = next;
2997 }
2998
2999 /* If, at this point, we have a nonzero carryout into the next
3000 digit, we'll increase the size by one digit, and store it...
3001 */
3002 if(save) {
3003 dp[used] = save;
3004 USED(mp) += 1;
3005 }
3006
3007 s_mp_clamp(mp);
3008 return MP_OKAY;
3009
3010 } /* end s_mp_mul_2d() */
3011
3012 /* }}} */
3013
3014 /* {{{ s_mp_div_2d(mp, d) */
3015
3016 /*
3017 Divide the integer by 2^d, where d is a number of bits. This
3018 amounts to a bitwise shift of the value, and does not require the
3019 full division code (used in Barrett reduction, see below)
3020 */
3021 void s_mp_div_2d(mp_int *mp, mp_digit d)
3022 {
3023 int ix;
3024 mp_digit save, next, mask, *dp = DIGITS(mp);
3025
3026 s_mp_rshd(mp, d / DIGIT_BIT);
3027 d %= DIGIT_BIT;
3028
3029 mask = (1 << d) - 1;
3030
3031 save = 0;
3032 for(ix = USED(mp) - 1; ix >= 0; ix--) {
3033 next = dp[ix] & mask;
3034 dp[ix] = (dp[ix] >> d) | (save << (DIGIT_BIT - d));
3035 save = next;
3036 }
3037
3038 s_mp_clamp(mp);
3039
3040 } /* end s_mp_div_2d() */
3041
3042 /* }}} */
3043
3044 /* {{{ s_mp_norm(a, b) */
3045
3046 /*
3047 s_mp_norm(a, b)
3048
3049 Normalize a and b for division, where b is the divisor. In order
3050 that we might make good guesses for quotient digits, we want the
3051 leading digit of b to be at least half the radix, which we
3052 accomplish by multiplying a and b by a constant. This constant is
3053 returned (so that it can be divided back out of the remainder at the
3054 end of the division process).
3055
3056 We multiply by the smallest power of 2 that gives us a leading digit
3057 at least half the radix. By choosing a power of 2, we simplify the
3058 multiplication and division steps to simple shifts.
3059 */
3060 mp_digit s_mp_norm(mp_int *a, mp_int *b)
3061 {
3062 mp_digit t, d = 0;
3063
3064 t = DIGIT(b, USED(b) - 1);
3065 while(t < (RADIX / 2)) {
3066 t <<= 1;
3067 ++d;
3068 }
3069
3070 if(d != 0) {
3071 s_mp_mul_2d(a, d);
3072 s_mp_mul_2d(b, d);
3073 }
3074
3075 return d;
3076
3077 } /* end s_mp_norm() */
3078
3079 /* }}} */
3080
3081 /* }}} */
3082
3083 /* {{{ Primitive digit arithmetic */
3084
3085 /* {{{ s_mp_add_d(mp, d) */
3086
3087 /* Add d to |mp| in place */
3088 mp_err s_mp_add_d(mp_int *mp, mp_digit d) /* unsigned digit addition */
3089 {
3090 mp_word w, k = 0;
3091 mp_size ix = 1, used = USED(mp);
3092 mp_digit *dp = DIGITS(mp);
3093
3094 w = dp[0] + d;
3095 dp[0] = ACCUM(w);
3096 k = CARRYOUT(w);
3097
3098 while(ix < used && k) {
3099 w = dp[ix] + k;
3100 dp[ix] = ACCUM(w);
3101 k = CARRYOUT(w);
3102 ++ix;
3103 }
3104
3105 if(k != 0) {
3106 mp_err res;
3107
3108 if((res = s_mp_pad(mp, USED(mp) + 1)) != MP_OKAY)
3109 return res;
3110
3111 DIGIT(mp, ix) = k;
3112 }
3113
3114 return MP_OKAY;
3115
3116 } /* end s_mp_add_d() */
3117
3118 /* }}} */
3119
3120 /* {{{ s_mp_sub_d(mp, d) */
3121
3122 /* Subtract d from |mp| in place, assumes |mp| > d */
3123 mp_err s_mp_sub_d(mp_int *mp, mp_digit d) /* unsigned digit subtract */
3124 {
3125 mp_word w, b = 0;
3126 mp_size ix = 1, used = USED(mp);
3127 mp_digit *dp = DIGITS(mp);
3128
3129 /* Compute initial subtraction */
3130 w = (RADIX + dp[0]) - d;
3131 b = CARRYOUT(w) ? 0 : 1;
3132 dp[0] = ACCUM(w);
3133
3134 /* Propagate borrows leftward */
3135 while(b && ix < used) {
3136 w = (RADIX + dp[ix]) - b;
3137 b = CARRYOUT(w) ? 0 : 1;
3138 dp[ix] = ACCUM(w);
3139 ++ix;
3140 }
3141
3142 /* Remove leading zeroes */
3143 s_mp_clamp(mp);
3144
3145 /* If we have a borrow out, it's a violation of the input invariant */
3146 if(b)
3147 return MP_RANGE;
3148 else
3149 return MP_OKAY;
3150
3151 } /* end s_mp_sub_d() */
3152
3153 /* }}} */
3154
3155 /* {{{ s_mp_mul_d(a, d) */
3156
3157 /* Compute a = a * d, single digit multiplication */
3158 mp_err s_mp_mul_d(mp_int *a, mp_digit d)
3159 {
3160 mp_word w, k = 0;
3161 mp_size ix, max;
3162 mp_err res;
3163 mp_digit *dp = DIGITS(a);
3164
3165 /*
3166 Single-digit multiplication will increase the precision of the
3167 output by at most one digit. However, we can detect when this
3168 will happen -- if the high-order digit of a, times d, gives a
3169 two-digit result, then the precision of the result will increase;
3170 otherwise it won't. We use this fact to avoid calling s_mp_pad()
3171 unless absolutely necessary.
3172 */
3173 max = USED(a);
3174 w = dp[max - 1] * d;
3175 if(CARRYOUT(w) != 0) {
3176 if((res = s_mp_pad(a, max + 1)) != MP_OKAY)
3177 return res;
3178 dp = DIGITS(a);
3179 }
3180
3181 for(ix = 0; ix < max; ix++) {
3182 w = (dp[ix] * d) + k;
3183 dp[ix] = ACCUM(w);
3184 k = CARRYOUT(w);
3185 }
3186
3187 /* If there is a precision increase, take care of it here; the above
3188 test guarantees we have enough storage to do this safely.
3189 */
3190 if(k) {
3191 dp[max] = k;
3192 USED(a) = max + 1;
3193 }
3194
3195 s_mp_clamp(a);
3196
3197 return MP_OKAY;
3198
3199 } /* end s_mp_mul_d() */
3200
3201 /* }}} */
3202
3203 /* {{{ s_mp_div_d(mp, d, r) */
3204
3205 /*
3206 s_mp_div_d(mp, d, r)
3207
3208 Compute the quotient mp = mp / d and remainder r = mp mod d, for a
3209 single digit d. If r is null, the remainder will be discarded.
3210 */
3211
3212 mp_err s_mp_div_d(mp_int *mp, mp_digit d, mp_digit *r)
3213 {
3214 mp_word w = 0, t;
3215 mp_int quot;
3216 mp_err res;
3217 mp_digit *dp = DIGITS(mp), *qp;
3218 int ix;
3219
3220 if(d == 0)
3221 return MP_RANGE;
3222
3223 /* Make room for the quotient */
3224 if((res = mp_init_size(&quot, USED(mp))) != MP_OKAY)
3225 return res;
3226
3227 USED(&quot) = USED(mp); /* so clamping will work below */
3228 qp = DIGITS(&quot);
3229
3230 /* Divide without subtraction */
3231 for(ix = USED(mp) - 1; ix >= 0; ix--) {
3232 w = (w << DIGIT_BIT) | dp[ix];
3233
3234 if(w >= d) {
3235 t = w / d;
3236 w = w % d;
3237 } else {
3238 t = 0;
3239 }
3240
3241 qp[ix] = t;
3242 }
3243
3244 /* Deliver the remainder, if desired */
3245 if(r)
3246 *r = w;
3247
3248 s_mp_clamp(&quot);
3249 mp_exch(&quot, mp);
3250 mp_clear(&quot);
3251
3252 return MP_OKAY;
3253
3254 } /* end s_mp_div_d() */
3255
3256 /* }}} */
3257
3258 /* }}} */
3259
3260 /* {{{ Primitive full arithmetic */
3261
3262 /* {{{ s_mp_add(a, b) */
3263
3264 /* Compute a = |a| + |b| */
3265 mp_err s_mp_add(mp_int *a, mp_int *b) /* magnitude addition */
3266 {
3267 mp_word w = 0;
3268 mp_digit *pa, *pb;
3269 mp_size ix, used = USED(b);
3270 mp_err res;
3271
3272 /* Make sure a has enough precision for the output value */
3273 if((used > USED(a)) && (res = s_mp_pad(a, used)) != MP_OKAY)
3274 return res;
3275
3276 /*
3277 Add up all digits up to the precision of b. If b had initially
3278 the same precision as a, or greater, we took care of it by the
3279 padding step above, so there is no problem. If b had initially
3280 less precision, we'll have to make sure the carry out is duly
3281 propagated upward among the higher-order digits of the sum.
3282 */
3283 pa = DIGITS(a);
3284 pb = DIGITS(b);
3285 for(ix = 0; ix < used; ++ix) {
3286 w += *pa + *pb++;
3287 *pa++ = ACCUM(w);
3288 w = CARRYOUT(w);
3289 }
3290
3291 /* If we run out of 'b' digits before we're actually done, make
3292 sure the carries get propagated upward...
3293 */
3294 used = USED(a);
3295 while(w && ix < used) {
3296 w += *pa;
3297 *pa++ = ACCUM(w);
3298 w = CARRYOUT(w);
3299 ++ix;
3300 }
3301
3302 /* If there's an overall carry out, increase precision and include
3303 it. We could have done this initially, but why touch the memory
3304 allocator unless we're sure we have to?
3305 */
3306 if(w) {
3307 if((res = s_mp_pad(a, used + 1)) != MP_OKAY)
3308 return res;
3309
3310 DIGIT(a, ix) = w; /* pa may not be valid after s_mp_pad() call */
3311 }
3312
3313 return MP_OKAY;
3314
3315 } /* end s_mp_add() */
3316
3317 /* }}} */
3318
3319 /* {{{ s_mp_sub(a, b) */
3320
3321 /* Compute a = |a| - |b|, assumes |a| >= |b| */
3322 mp_err s_mp_sub(mp_int *a, mp_int *b) /* magnitude subtract */
3323 {
3324 mp_word w = 0;
3325 mp_digit *pa, *pb;
3326 mp_size ix, used = USED(b);
3327
3328 /*
3329 Subtract and propagate borrow. Up to the precision of b, this
3330 accounts for the digits of b; after that, we just make sure the
3331 carries get to the right place. This saves having to pad b out to
3332 the precision of a just to make the loops work right...
3333 */
3334 pa = DIGITS(a);
3335 pb = DIGITS(b);
3336
3337 for(ix = 0; ix < used; ++ix) {
3338 w = (RADIX + *pa) - w - *pb++;
3339 *pa++ = ACCUM(w);
3340 w = CARRYOUT(w) ? 0 : 1;
3341 }
3342
3343 used = USED(a);
3344 while(ix < used) {
3345 w = RADIX + *pa - w;
3346 *pa++ = ACCUM(w);
3347 w = CARRYOUT(w) ? 0 : 1;
3348 ++ix;
3349 }
3350
3351 /* Clobber any leading zeroes we created */
3352 s_mp_clamp(a);
3353
3354 /*
3355 If there was a borrow out, then |b| > |a| in violation
3356 of our input invariant. We've already done the work,
3357 but we'll at least complain about it...
3358 */
3359 if(w)
3360 return MP_RANGE;
3361 else
3362 return MP_OKAY;
3363
3364 } /* end s_mp_sub() */
3365
3366 /* }}} */
3367
3368 mp_err s_mp_reduce(mp_int *x, mp_int *m, mp_int *mu)
3369 {
3370 mp_int q;
3371 mp_err res;
3372 mp_size um = USED(m);
3373
3374 if((res = mp_init_copy(&q, x)) != MP_OKAY)
3375 return res;
3376
3377 s_mp_rshd(&q, um - 1); /* q1 = x / b^(k-1) */
3378 s_mp_mul(&q, mu); /* q2 = q1 * mu */
3379 s_mp_rshd(&q, um + 1); /* q3 = q2 / b^(k+1) */
3380
3381 /* x = x mod b^(k+1), quick (no division) */
3382 s_mp_mod_2d(x, (mp_digit)(DIGIT_BIT * (um + 1)));
3383
3384 /* q = q * m mod b^(k+1), quick (no division), uses the short multiplier */
3385 #ifndef SHRT_MUL
3386 s_mp_mul(&q, m);
3387 s_mp_mod_2d(&q, (mp_digit)(DIGIT_BIT * (um + 1)));
3388 #else
3389 s_mp_mul_dig(&q, m, um + 1);
3390 #endif
3391
3392 /* x = x - q */
3393 if((res = mp_sub(x, &q, x)) != MP_OKAY)
3394 goto CLEANUP;
3395
3396 /* If x < 0, add b^(k+1) to it */
3397 if(mp_cmp_z(x) < 0) {
3398 mp_set(&q, 1);
3399 if((res = s_mp_lshd(&q, um + 1)) != MP_OKAY)
3400 goto CLEANUP;
3401 if((res = mp_add(x, &q, x)) != MP_OKAY)
3402 goto CLEANUP;
3403 }
3404
3405 /* Back off if it's too big */
3406 while(mp_cmp(x, m) >= 0) {
3407 if((res = s_mp_sub(x, m)) != MP_OKAY)
3408 break;
3409 }
3410
3411 CLEANUP:
3412 mp_clear(&q);
3413
3414 return res;
3415
3416 } /* end s_mp_reduce() */
3417
3418
3419
3420 /* {{{ s_mp_mul(a, b) */
3421
3422 /* Compute a = |a| * |b| */
3423 mp_err s_mp_mul(mp_int *a, mp_int *b)
3424 {
3425 mp_word w, k = 0;
3426 mp_int tmp;
3427 mp_err res;
3428 mp_size ix, jx, ua = USED(a), ub = USED(b);
3429 mp_digit *pa, *pb, *pt, *pbt;
3430
3431 if((res = mp_init_size(&tmp, ua + ub)) != MP_OKAY)
3432 return res;
3433
3434 /* This has the effect of left-padding with zeroes... */
3435 USED(&tmp) = ua + ub;
3436
3437 /* We're going to need the base value each iteration */
3438 pbt = DIGITS(&tmp);
3439
3440 /* Outer loop: Digits of b */
3441
3442 pb = DIGITS(b);
3443 for(ix = 0; ix < ub; ++ix, ++pb) {
3444 if(*pb == 0)
3445 continue;
3446
3447 /* Inner product: Digits of a */
3448 pa = DIGITS(a);
3449 for(jx = 0; jx < ua; ++jx, ++pa) {
3450 pt = pbt + ix + jx;
3451 w = *pb * *pa + k + *pt;
3452 *pt = ACCUM(w);
3453 k = CARRYOUT(w);
3454 }
3455
3456 pbt[ix + jx] = k;
3457 k = 0;
3458 }
3459
3460 s_mp_clamp(&tmp);
3461 s_mp_exch(&tmp, a);
3462
3463 mp_clear(&tmp);
3464
3465 return MP_OKAY;
3466
3467 } /* end s_mp_mul() */
3468
3469 /* }}} */
3470
3471 /* {{{ s_mp_kmul(a, b, out, len) */
3472
3473 #if 0
3474 void s_mp_kmul(mp_digit *a, mp_digit *b, mp_digit *out, mp_size len)
3475 {
3476 mp_word w, k = 0;
3477 mp_size ix, jx;
3478 mp_digit *pa, *pt;
3479
3480 for(ix = 0; ix < len; ++ix, ++b) {
3481 if(*b == 0)
3482 continue;
3483
3484 pa = a;
3485 for(jx = 0; jx < len; ++jx, ++pa) {
3486 pt = out + ix + jx;
3487 w = *b * *pa + k + *pt;
3488 *pt = ACCUM(w);
3489 k = CARRYOUT(w);
3490 }
3491
3492 out[ix + jx] = k;
3493 k = 0;
3494 }
3495
3496 } /* end s_mp_kmul() */
3497 #endif
3498
3499 /* }}} */
3500
3501 /* {{{ s_mp_sqr(a) */
3502
3503 /*
3504 Computes the square of a, in place. This can be done more
3505 efficiently than a general multiplication, because many of the
3506 computation steps are redundant when squaring. The inner product
3507 step is a bit more complicated, but we save a fair number of
3508 iterations of the multiplication loop.
3509 */
3510 #if MP_SQUARE
3511 mp_err s_mp_sqr(mp_int *a)
3512 {
3513 mp_word w, k = 0;
3514 mp_int tmp;
3515 mp_err res;
3516 mp_size ix, jx, kx, used = USED(a);
3517 mp_digit *pa1, *pa2, *pt, *pbt;
3518
3519 if((res = mp_init_size(&tmp, 2 * used)) != MP_OKAY)
3520 return res;
3521
3522 /* Left-pad with zeroes */
3523 USED(&tmp) = 2 * used;
3524
3525 /* We need the base value each time through the loop */
3526 pbt = DIGITS(&tmp);
3527
3528 pa1 = DIGITS(a);
3529 for(ix = 0; ix < used; ++ix, ++pa1) {
3530 if(*pa1 == 0)
3531 continue;
3532
3533 w = DIGIT(&tmp, ix + ix) + (*pa1 * *pa1);
3534
3535 pbt[ix + ix] = ACCUM(w);
3536 k = CARRYOUT(w);
3537
3538 /*
3539 The inner product is computed as:
3540
3541 (C, S) = t[i,j] + 2 a[i] a[j] + C
3542
3543 This can overflow what can be represented in an mp_word, and
3544 since C arithmetic does not provide any way to check for
3545 overflow, we have to check explicitly for overflow conditions
3546 before they happen.
3547 */
3548 for(jx = ix + 1, pa2 = DIGITS(a) + jx; jx < used; ++jx, ++pa2) {
3549 mp_word u = 0, v;
3550
3551 /* Store this in a temporary to avoid indirections later */
3552 pt = pbt + ix + jx;
3553
3554 /* Compute the multiplicative step */
3555 w = *pa1 * *pa2;
3556
3557 /* If w is more than half MP_WORD_MAX, the doubling will
3558 overflow, and we need to record a carry out into the next
3559 word */
3560 u = (w >> (MP_WORD_BIT - 1)) & 1;
3561
3562 /* Double what we've got, overflow will be ignored as defined
3563 for C arithmetic (we've already noted if it is to occur)
3564 */
3565 w *= 2;
3566
3567 /* Compute the additive step */
3568 v = *pt + k;
3569
3570 /* If we do not already have an overflow carry, check to see
3571 if the addition will cause one, and set the carry out if so
3572 */
3573 u |= ((MP_WORD_MAX - v) < w);
3574
3575 /* Add in the rest, again ignoring overflow */
3576 w += v;
3577
3578 /* Set the i,j digit of the output */
3579 *pt = ACCUM(w);
3580
3581 /* Save carry information for the next iteration of the loop.
3582 This is why k must be an mp_word, instead of an mp_digit */
3583 k = CARRYOUT(w) | (u << DIGIT_BIT);
3584
3585 } /* for(jx ...) */
3586
3587 /* Set the last digit in the cycle and reset the carry */
3588 k = DIGIT(&tmp, ix + jx) + k;
3589 pbt[ix + jx] = ACCUM(k);
3590 k = CARRYOUT(k);
3591
3592 /* If we are carrying out, propagate the carry to the next digit
3593 in the output. This may cascade, so we have to be somewhat
3594 circumspect -- but we will have enough precision in the output
3595 that we won't overflow
3596 */
3597 kx = 1;
3598 while(k) {
3599 k = pbt[ix + jx + kx] + 1;
3600 pbt[ix + jx + kx] = ACCUM(k);
3601 k = CARRYOUT(k);
3602 ++kx;
3603 }
3604 } /* for(ix ...) */
3605
3606 s_mp_clamp(&tmp);
3607 s_mp_exch(&tmp, a);
3608
3609 mp_clear(&tmp);
3610
3611 return MP_OKAY;
3612
3613 } /* end s_mp_sqr() */
3614 #endif
3615
3616 /* }}} */
3617
3618 /* {{{ s_mp_div(a, b) */
3619
3620 /*
3621 s_mp_div(a, b)
3622
3623 Compute a = a / b and b = a mod b. Assumes b > a.
3624 */
3625
3626 mp_err s_mp_div(mp_int *a, mp_int *b)
3627 {
3628 mp_int quot, rem, t;
3629 mp_word q;
3630 mp_err res;
3631 mp_digit d;
3632 int ix;
3633
3634 if(mp_cmp_z(b) == 0)
3635 return MP_RANGE;
3636
3637 /* Shortcut if b is power of two */
3638 if((ix = s_mp_ispow2(b)) >= 0) {
3639 mp_copy(a, b); /* need this for remainder */
3640 s_mp_div_2d(a, (mp_digit)ix);
3641 s_mp_mod_2d(b, (mp_digit)ix);
3642
3643 return MP_OKAY;
3644 }
3645
3646 /* Allocate space to store the quotient */
3647 if((res = mp_init_size(&quot, USED(a))) != MP_OKAY)
3648 return res;
3649
3650 /* A working temporary for division */
3651 if((res = mp_init_size(&t, USED(a))) != MP_OKAY)
3652 goto T;
3653
3654 /* Allocate space for the remainder */
3655 if((res = mp_init_size(&rem, USED(a))) != MP_OKAY)
3656 goto REM;
3657
3658 /* Normalize to optimize guessing */
3659 d = s_mp_norm(a, b);
3660
3661 /* Perform the division itself...woo! */
3662 ix = USED(a) - 1;
3663
3664 while(ix >= 0) {
3665 /* Find a partial substring of a which is at least b */
3666 while(s_mp_cmp(&rem, b) < 0 && ix >= 0) {
3667 if((res = s_mp_lshd(&rem, 1)) != MP_OKAY)
3668 goto CLEANUP;
3669
3670 if((res = s_mp_lshd(&quot, 1)) != MP_OKAY)
3671 goto CLEANUP;
3672
3673 DIGIT(&rem, 0) = DIGIT(a, ix);
3674 s_mp_clamp(&rem);
3675 --ix;
3676 }
3677
3678 /* If we didn't find one, we're finished dividing */
3679 if(s_mp_cmp(&rem, b) < 0)
3680 break;
3681
3682 /* Compute a guess for the next quotient digit */
3683 q = DIGIT(&rem, USED(&rem) - 1);
3684 if(q <= DIGIT(b, USED(b) - 1) && USED(&rem) > 1)
3685 q = (q << DIGIT_BIT) | DIGIT(&rem, USED(&rem) - 2);
3686
3687 q /= DIGIT(b, USED(b) - 1);
3688
3689 /* The guess can be as much as RADIX + 1 */
3690 if(q >= RADIX)
3691 q = RADIX - 1;
3692
3693 /* See what that multiplies out to */
3694 mp_copy(b, &t);
3695 if((res = s_mp_mul_d(&t, q)) != MP_OKAY)
3696 goto CLEANUP;
3697
3698 /*
3699 If it's too big, back it off. We should not have to do this
3700 more than once, or, in rare cases, twice. Knuth describes a
3701 method by which this could be reduced to a maximum of once, but
3702 I didn't implement that here.
3703 */
3704 while(s_mp_cmp(&t, &rem) > 0) {
3705 --q;
3706 s_mp_sub(&t, b);
3707 }
3708
3709 /* At this point, q should be the right next digit */
3710 if((res = s_mp_sub(&rem, &t)) != MP_OKAY)
3711 goto CLEANUP;
3712
3713 /*
3714 Include the digit in the quotient. We allocated enough memory
3715 for any quotient we could ever possibly get, so we should not
3716 have to check for failures here
3717 */
3718 DIGIT(&quot, 0) = q;
3719 }
3720
3721 /* Denormalize remainder */
3722 if(d != 0)
3723 s_mp_div_2d(&rem, d);
3724
3725 s_mp_clamp(&quot);
3726 s_mp_clamp(&rem);
3727
3728 /* Copy quotient back to output */
3729 s_mp_exch(&quot, a);
3730
3731 /* Copy remainder back to output */
3732 s_mp_exch(&rem, b);
3733
3734 CLEANUP:
3735 mp_clear(&rem);
3736 REM:
3737 mp_clear(&t);
3738 T:
3739 mp_clear(&quot);
3740
3741 return res;
3742
3743 } /* end s_mp_div() */
3744
3745 /* }}} */
3746
3747 /* {{{ s_mp_2expt(a, k) */
3748
3749 mp_err s_mp_2expt(mp_int *a, mp_digit k)
3750 {
3751 mp_err res;
3752 mp_size dig, bit;
3753
3754 dig = k / DIGIT_BIT;
3755 bit = k % DIGIT_BIT;
3756
3757 mp_zero(a);
3758 if((res = s_mp_pad(a, dig + 1)) != MP_OKAY)
3759 return res;
3760
3761 DIGIT(a, dig) |= (1 << bit);
3762
3763 return MP_OKAY;
3764
3765 } /* end s_mp_2expt() */
3766
3767 /* }}} */
3768
3769
3770 /* }}} */
3771
3772 /* }}} */
3773
3774 /* {{{ Primitive comparisons */
3775
3776 /* {{{ s_mp_cmp(a, b) */
3777
3778 /* Compare |a| <=> |b|, return 0 if equal, <0 if a<b, >0 if a>b */
3779 int s_mp_cmp(mp_int *a, mp_int *b)
3780 {
3781 mp_size ua = USED(a), ub = USED(b);
3782
3783 if(ua > ub)
3784 return MP_GT;
3785 else if(ua < ub)
3786 return MP_LT;
3787 else {
3788 int ix = ua - 1;
3789 mp_digit *ap = DIGITS(a) + ix, *bp = DIGITS(b) + ix;
3790
3791 while(ix >= 0) {
3792 if(*ap > *bp)
3793 return MP_GT;
3794 else if(*ap < *bp)
3795 return MP_LT;
3796
3797 --ap; --bp; --ix;
3798 }
3799
3800 return MP_EQ;
3801 }
3802
3803 } /* end s_mp_cmp() */
3804
3805 /* }}} */
3806
3807 /* {{{ s_mp_cmp_d(a, d) */
3808
3809 /* Compare |a| <=> d, return 0 if equal, <0 if a<d, >0 if a>d */
3810 int s_mp_cmp_d(mp_int *a, mp_digit d)
3811 {
3812 mp_size ua = USED(a);
3813 mp_digit *ap = DIGITS(a);
3814
3815 if(ua > 1)
3816 return MP_GT;
3817
3818 if(*ap < d)
3819 return MP_LT;
3820 else if(*ap > d)
3821 return MP_GT;
3822 else
3823 return MP_EQ;
3824
3825 } /* end s_mp_cmp_d() */
3826
3827 /* }}} */
3828
3829 /* {{{ s_mp_ispow2(v) */
3830
3831 /*
3832 Returns -1 if the value is not a power of two; otherwise, it returns
3833 k such that v = 2^k, i.e. lg(v).
3834 */
3835 int s_mp_ispow2(mp_int *v)
3836 {
3837 mp_digit d, *dp;
3838 mp_size uv = USED(v);
3839 int extra = 0, ix;
3840
3841 d = DIGIT(v, uv - 1); /* most significant digit of v */
3842
3843 while(d && ((d & 1) == 0)) {
3844 d >>= 1;
3845 ++extra;
3846 }
3847
3848 if(d == 1) {
3849 ix = uv - 2;
3850 dp = DIGITS(v) + ix;
3851
3852 while(ix >= 0) {
3853 if(*dp)
3854 return -1; /* not a power of two */
3855
3856 --dp; --ix;
3857 }
3858
3859 return ((uv - 1) * DIGIT_BIT) + extra;
3860 }
3861
3862 return -1;
3863
3864 } /* end s_mp_ispow2() */
3865
3866 /* }}} */
3867
3868 /* {{{ s_mp_ispow2d(d) */
3869
3870 int s_mp_ispow2d(mp_digit d)
3871 {
3872 int pow = 0;
3873
3874 while((d & 1) == 0) {
3875 ++pow; d >>= 1;
3876 }
3877
3878 if(d == 1)
3879 return pow;
3880
3881 return -1;
3882
3883 } /* end s_mp_ispow2d() */
3884
3885 /* }}} */
3886
3887 /* }}} */
3888
3889 /* {{{ Primitive I/O helpers */
3890
3891 /* {{{ s_mp_tovalue(ch, r) */
3892
3893 /*
3894 Convert the given character to its digit value, in the given radix.
3895 If the given character is not understood in the given radix, -1 is
3896 returned. Otherwise the digit's numeric value is returned.
3897
3898 The results will be odd if you use a radix < 2 or > 62, you are
3899 expected to know what you're up to.
3900 */
3901 int s_mp_tovalue(char ch, int r)
3902 {
3903 int val, xch;
3904
3905 if(r > 36)
3906 xch = ch;
3907 else
3908 xch = toupper(ch);
3909
3910 if(isdigit(xch))
3911 val = xch - '0';
3912 else if(isupper(xch))
3913 val = xch - 'A' + 10;
3914 else if(islower(xch))
3915 val = xch - 'a' + 36;
3916 else if(xch == '+')
3917 val = 62;
3918 else if(xch == '/')
3919 val = 63;
3920 else
3921 return -1;
3922
3923 if(val < 0 || val >= r)
3924 return -1;
3925
3926 return val;
3927
3928 } /* end s_mp_tovalue() */
3929
3930 /* }}} */
3931
3932 /* {{{ s_mp_todigit(val, r, low) */
3933
3934 /*
3935 Convert val to a radix-r digit, if possible. If val is out of range
3936 for r, returns zero. Otherwise, returns an ASCII character denoting
3937 the value in the given radix.
3938
3939 The results may be odd if you use a radix < 2 or > 64, you are
3940 expected to know what you're doing.
3941 */
3942
3943 char s_mp_todigit(int val, int r, int low)
3944 {
3945 char ch;
3946
3947 if(val < 0 || val >= r)
3948 return 0;
3949
3950 ch = s_dmap_1[val];
3951
3952 if(r <= 36 && low)
3953 ch = tolower(ch);
3954
3955 return ch;
3956
3957 } /* end s_mp_todigit() */
3958
3959 /* }}} */
3960
3961 /* {{{ s_mp_outlen(bits, radix) */
3962
3963 /*
3964 Return an estimate for how long a string is needed to hold a radix
3965 r representation of a number with 'bits' significant bits.
3966
3967 Does not include space for a sign or a NUL terminator.
3968 */
3969 int s_mp_outlen(int bits, int r)
3970 {
3971 return (int)((double)bits * LOG_V_2(r));
3972
3973 } /* end s_mp_outlen() */
3974
3975 /* }}} */
3976
3977 /* }}} */
3978
3979 /*------------------------------------------------------------------------*/
3980 /* HERE THERE BE DRAGONS */
3981 /* crc==4242132123, version==2, Sat Feb 02 06:43:52 2002 */