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annotate libtommath/bn_mp_pack.c @ 1938:77bc00dcc19f default tip main master

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Bump version to 2022.82
author Matt Johnston <matt@ucc.asn.au>
date Fri, 01 Apr 2022 14:43:27 +0800
parents 1051e4eea25a
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
1692
1051e4eea25a Update LibTomMath to 1.2.0 (#84)
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_PACK_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
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4 /* SPDX-License-Identifier: Unlicense */
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5
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6 /* based on gmp's mpz_export.
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7 * see http://gmplib.org/manual/Integer-Import-and-Export.html
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8 */
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9 mp_err mp_pack(void *rop, size_t maxcount, size_t *written, mp_order order, size_t size,
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10 mp_endian endian, size_t nails, const mp_int *op)
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11 {
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12 mp_err err;
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13 size_t odd_nails, nail_bytes, i, j, count;
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14 unsigned char odd_nail_mask;
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15
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16 mp_int t;
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17
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18 count = mp_pack_count(op, nails, size);
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19
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20 if (count > maxcount) {
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21 return MP_BUF;
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22 }
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23
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24 if ((err = mp_init_copy(&t, op)) != MP_OKAY) {
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25 return err;
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26 }
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27
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28 if (endian == MP_NATIVE_ENDIAN) {
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29 MP_GET_ENDIANNESS(endian);
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30 }
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31
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32 odd_nails = (nails % 8u);
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33 odd_nail_mask = 0xff;
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34 for (i = 0u; i < odd_nails; ++i) {
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35 odd_nail_mask ^= (unsigned char)(1u << (7u - i));
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36 }
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37 nail_bytes = nails / 8u;
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38
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39 for (i = 0u; i < count; ++i) {
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40 for (j = 0u; j < size; ++j) {
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41 unsigned char *byte = (unsigned char *)rop +
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42 (((order == MP_LSB_FIRST) ? i : ((count - 1u) - i)) * size) +
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43 ((endian == MP_LITTLE_ENDIAN) ? j : ((size - 1u) - j));
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44
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45 if (j >= (size - nail_bytes)) {
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46 *byte = 0;
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47 continue;
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48 }
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49
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50 *byte = (unsigned char)((j == ((size - nail_bytes) - 1u)) ? (t.dp[0] & odd_nail_mask) : (t.dp[0] & 0xFFuL));
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51
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52 if ((err = mp_div_2d(&t, (j == ((size - nail_bytes) - 1u)) ? (int)(8u - odd_nails) : 8, &t, NULL)) != MP_OKAY) {
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53 goto LBL_ERR;
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54 }
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55
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56 }
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57 }
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58
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59 if (written != NULL) {
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60 *written = count;
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61 }
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62 err = MP_OKAY;
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63
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64 LBL_ERR:
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65 mp_clear(&t);
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66 return err;
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67 }
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68
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69 #endif