1 /* mpn_set_str (mp_ptr res_ptr, const char *str, size_t str_len, int base) --
2 Convert a STR_LEN long base BASE byte string pointed to by STR to a limb
3 vector pointed to by RES_PTR. Return the number of limbs in RES_PTR.
4
5 Contributed to the GNU project by Torbjorn Granlund.
6
7 THE FUNCTIONS IN THIS FILE, EXCEPT mpn_set_str, ARE INTERNAL WITH A MUTABLE
8 INTERFACE. IT IS ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN
9 FACT, IT IS ALMOST GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE
10 GNU MP RELEASE.
11
12 Copyright 1991-1994, 1996, 2000-2002, 2004, 2006-2008, 2012, 2013 Free
13 Software Foundation, Inc.
14
15 This file is part of the GNU MP Library.
16
17 The GNU MP Library is free software; you can redistribute it and/or modify
18 it under the terms of either:
19
20 * the GNU Lesser General Public License as published by the Free
21 Software Foundation; either version 3 of the License, or (at your
22 option) any later version.
23
24 or
25
26 * the GNU General Public License as published by the Free Software
27 Foundation; either version 2 of the License, or (at your option) any
28 later version.
29
30 or both in parallel, as here.
31
32 The GNU MP Library is distributed in the hope that it will be useful, but
33 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
34 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
35 for more details.
36
37 You should have received copies of the GNU General Public License and the
38 GNU Lesser General Public License along with the GNU MP Library. If not,
39 see https://www.gnu.org/licenses/. */
40
41
42 /* TODO:
43
44 Perhaps do not compute the highest power?
45 Instead, multiply twice by the 2nd highest power:
46
47 _______
48 |_______| hp
49 |_______| pow
50 _______________
51 |_______________| final result
52
53
54 _______
55 |_______| hp
56 |___| pow[-1]
57 ___________
58 |___________| intermediate result
59 |___| pow[-1]
60 _______________
61 |_______________| final result
62
63 Generalizing that idea, perhaps we should make powtab contain successive
64 cubes, not squares.
65 */
66
67 #include "gmp.h"
68 #include "gmp-impl.h"
69 #include "longlong.h"
70
71 mp_size_t
mpn_set_str(mp_ptr rp,const unsigned char * str,size_t str_len,int base)72 mpn_set_str (mp_ptr rp, const unsigned char *str, size_t str_len, int base)
73 {
74 if (POW2_P (base))
75 {
76 /* The base is a power of 2. Read the input string from least to most
77 significant character/digit. */
78
79 const unsigned char *s;
80 int next_bitpos;
81 mp_limb_t res_digit;
82 mp_size_t size;
83 int bits_per_indigit = mp_bases[base].big_base;
84
85 size = 0;
86 res_digit = 0;
87 next_bitpos = 0;
88
89 for (s = str + str_len - 1; s >= str; s--)
90 {
91 int inp_digit = *s;
92
93 res_digit |= ((mp_limb_t) inp_digit << next_bitpos) & GMP_NUMB_MASK;
94 next_bitpos += bits_per_indigit;
95 if (next_bitpos >= GMP_NUMB_BITS)
96 {
97 rp[size++] = res_digit;
98 next_bitpos -= GMP_NUMB_BITS;
99 res_digit = inp_digit >> (bits_per_indigit - next_bitpos);
100 }
101 }
102
103 if (res_digit != 0)
104 rp[size++] = res_digit;
105 return size;
106 }
107
108 if (BELOW_THRESHOLD (str_len, SET_STR_PRECOMPUTE_THRESHOLD))
109 return mpn_bc_set_str (rp, str, str_len, base);
110 else
111 {
112 mp_ptr powtab_mem, tp;
113 powers_t powtab[GMP_LIMB_BITS];
114 int chars_per_limb;
115 mp_size_t size;
116 mp_size_t un;
117 TMP_DECL;
118
119 TMP_MARK;
120
121 chars_per_limb = mp_bases[base].chars_per_limb;
122
123 un = str_len / chars_per_limb + 1;
124
125 /* Allocate one large block for the powers of big_base. */
126 powtab_mem = TMP_BALLOC_LIMBS (mpn_dc_set_str_powtab_alloc (un));
127
128 mpn_set_str_compute_powtab (powtab, powtab_mem, un, base);
129
130 tp = TMP_BALLOC_LIMBS (mpn_dc_set_str_itch (un));
131 size = mpn_dc_set_str (rp, str, str_len, powtab, tp);
132
133 TMP_FREE;
134 return size;
135 }
136 }
137
138 void
mpn_set_str_compute_powtab(powers_t * powtab,mp_ptr powtab_mem,mp_size_t un,int base)139 mpn_set_str_compute_powtab (powers_t *powtab, mp_ptr powtab_mem, mp_size_t un, int base)
140 {
141 mp_ptr powtab_mem_ptr;
142 long i, pi;
143 mp_size_t n;
144 mp_ptr p, t;
145 mp_limb_t big_base;
146 int chars_per_limb;
147 size_t digits_in_base;
148 mp_size_t shift;
149
150 powtab_mem_ptr = powtab_mem;
151
152 chars_per_limb = mp_bases[base].chars_per_limb;
153 big_base = mp_bases[base].big_base;
154
155 p = powtab_mem_ptr;
156 powtab_mem_ptr += 1;
157
158 digits_in_base = chars_per_limb;
159
160 p[0] = big_base;
161 n = 1;
162
163 count_leading_zeros (i, un - 1);
164 i = GMP_LIMB_BITS - 1 - i;
165
166 powtab[i].p = p;
167 powtab[i].n = n;
168 powtab[i].digits_in_base = digits_in_base;
169 powtab[i].base = base;
170 powtab[i].shift = 0;
171
172 shift = 0;
173 for (pi = i - 1; pi >= 0; pi--)
174 {
175 t = powtab_mem_ptr;
176 powtab_mem_ptr += 2 * n;
177
178 ASSERT_ALWAYS (powtab_mem_ptr < powtab_mem + mpn_dc_set_str_powtab_alloc (un));
179
180 mpn_sqr (t, p, n);
181 n = 2 * n - 1; n += t[n] != 0;
182 digits_in_base *= 2;
183 #if 1
184 if ((((un - 1) >> pi) & 2) == 0)
185 {
186 mpn_divexact_1 (t, t, n, big_base);
187 n -= t[n - 1] == 0;
188 digits_in_base -= chars_per_limb;
189 }
190 #else
191 if (CLEVER_CONDITION_1 ())
192 {
193 /* perform adjustment operation of previous */
194 cy = mpn_mul_1 (p, p, n, big_base);
195 }
196 if (CLEVER_CONDITION_2 ())
197 {
198 /* perform adjustment operation of new */
199 cy = mpn_mul_1 (t, t, n, big_base);
200 }
201 #endif
202 shift *= 2;
203 /* Strip low zero limbs, but be careful to keep the result divisible by
204 big_base. */
205 while (t[0] == 0 && (t[1] & ((big_base & -big_base) - 1)) == 0)
206 {
207 t++;
208 n--;
209 shift++;
210 }
211 p = t;
212 powtab[pi].p = p;
213 powtab[pi].n = n;
214 powtab[pi].digits_in_base = digits_in_base;
215 powtab[pi].base = base;
216 powtab[pi].shift = shift;
217 }
218 }
219
220 mp_size_t
mpn_dc_set_str(mp_ptr rp,const unsigned char * str,size_t str_len,const powers_t * powtab,mp_ptr tp)221 mpn_dc_set_str (mp_ptr rp, const unsigned char *str, size_t str_len,
222 const powers_t *powtab, mp_ptr tp)
223 {
224 size_t len_lo, len_hi;
225 mp_limb_t cy;
226 mp_size_t ln, hn, n, sn;
227
228 len_lo = powtab->digits_in_base;
229
230 if (str_len <= len_lo)
231 {
232 if (BELOW_THRESHOLD (str_len, SET_STR_DC_THRESHOLD))
233 return mpn_bc_set_str (rp, str, str_len, powtab->base);
234 else
235 return mpn_dc_set_str (rp, str, str_len, powtab + 1, tp);
236 }
237
238 len_hi = str_len - len_lo;
239 ASSERT (len_lo >= len_hi);
240
241 if (BELOW_THRESHOLD (len_hi, SET_STR_DC_THRESHOLD))
242 hn = mpn_bc_set_str (tp, str, len_hi, powtab->base);
243 else
244 hn = mpn_dc_set_str (tp, str, len_hi, powtab + 1, rp);
245
246 sn = powtab->shift;
247
248 if (hn == 0)
249 {
250 /* Zero +1 limb here, to avoid reading an allocated but uninitialised
251 limb in mpn_incr_u below. */
252 MPN_ZERO (rp, powtab->n + sn + 1);
253 }
254 else
255 {
256 if (powtab->n > hn)
257 mpn_mul (rp + sn, powtab->p, powtab->n, tp, hn);
258 else
259 mpn_mul (rp + sn, tp, hn, powtab->p, powtab->n);
260 MPN_ZERO (rp, sn);
261 }
262
263 str = str + str_len - len_lo;
264 if (BELOW_THRESHOLD (len_lo, SET_STR_DC_THRESHOLD))
265 ln = mpn_bc_set_str (tp, str, len_lo, powtab->base);
266 else
267 ln = mpn_dc_set_str (tp, str, len_lo, powtab + 1, tp + powtab->n + sn + 1);
268
269 if (ln != 0)
270 {
271 cy = mpn_add_n (rp, rp, tp, ln);
272 mpn_incr_u (rp + ln, cy);
273 }
274 n = hn + powtab->n + sn;
275 return n - (rp[n - 1] == 0);
276 }
277
278 mp_size_t
mpn_bc_set_str(mp_ptr rp,const unsigned char * str,size_t str_len,int base)279 mpn_bc_set_str (mp_ptr rp, const unsigned char *str, size_t str_len, int base)
280 {
281 mp_size_t size;
282 size_t i;
283 long j;
284 mp_limb_t cy_limb;
285
286 mp_limb_t big_base;
287 int chars_per_limb;
288 mp_limb_t res_digit;
289
290 ASSERT (base >= 2);
291 ASSERT (base < numberof (mp_bases));
292 ASSERT (str_len >= 1);
293
294 big_base = mp_bases[base].big_base;
295 chars_per_limb = mp_bases[base].chars_per_limb;
296
297 size = 0;
298 for (i = chars_per_limb; i < str_len; i += chars_per_limb)
299 {
300 res_digit = *str++;
301 if (base == 10)
302 { /* This is a common case.
303 Help the compiler to avoid multiplication. */
304 for (j = MP_BASES_CHARS_PER_LIMB_10 - 1; j != 0; j--)
305 res_digit = res_digit * 10 + *str++;
306 }
307 else
308 {
309 for (j = chars_per_limb - 1; j != 0; j--)
310 res_digit = res_digit * base + *str++;
311 }
312
313 if (size == 0)
314 {
315 if (res_digit != 0)
316 {
317 rp[0] = res_digit;
318 size = 1;
319 }
320 }
321 else
322 {
323 #if HAVE_NATIVE_mpn_mul_1c
324 cy_limb = mpn_mul_1c (rp, rp, size, big_base, res_digit);
325 #else
326 cy_limb = mpn_mul_1 (rp, rp, size, big_base);
327 cy_limb += mpn_add_1 (rp, rp, size, res_digit);
328 #endif
329 if (cy_limb != 0)
330 rp[size++] = cy_limb;
331 }
332 }
333
334 big_base = base;
335 res_digit = *str++;
336 if (base == 10)
337 { /* This is a common case.
338 Help the compiler to avoid multiplication. */
339 for (j = str_len - (i - MP_BASES_CHARS_PER_LIMB_10) - 1; j > 0; j--)
340 {
341 res_digit = res_digit * 10 + *str++;
342 big_base *= 10;
343 }
344 }
345 else
346 {
347 for (j = str_len - (i - chars_per_limb) - 1; j > 0; j--)
348 {
349 res_digit = res_digit * base + *str++;
350 big_base *= base;
351 }
352 }
353
354 if (size == 0)
355 {
356 if (res_digit != 0)
357 {
358 rp[0] = res_digit;
359 size = 1;
360 }
361 }
362 else
363 {
364 #if HAVE_NATIVE_mpn_mul_1c
365 cy_limb = mpn_mul_1c (rp, rp, size, big_base, res_digit);
366 #else
367 cy_limb = mpn_mul_1 (rp, rp, size, big_base);
368 cy_limb += mpn_add_1 (rp, rp, size, res_digit);
369 #endif
370 if (cy_limb != 0)
371 rp[size++] = cy_limb;
372 }
373 return size;
374 }
375