50 lines
1.4 KiB
C
50 lines
1.4 KiB
C
#include "tommath_private.h"
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#ifdef BN_MP_UNPACK_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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/* based on gmp's mpz_import.
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* see http://gmplib.org/manual/Integer-Import-and-Export.html
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*/
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mp_err mp_unpack(mp_int *rop, size_t count, mp_order order, size_t size,
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mp_endian endian, size_t nails, const void *op)
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{
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mp_err err;
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size_t odd_nails, nail_bytes, i, j;
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unsigned char odd_nail_mask;
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mp_zero(rop);
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if (endian == MP_NATIVE_ENDIAN) {
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MP_GET_ENDIANNESS(endian);
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}
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odd_nails = (nails % 8u);
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odd_nail_mask = 0xff;
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for (i = 0; i < odd_nails; ++i) {
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odd_nail_mask ^= (unsigned char)(1u << (7u - i));
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}
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nail_bytes = nails / 8u;
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for (i = 0; i < count; ++i) {
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for (j = 0; j < (size - nail_bytes); ++j) {
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unsigned char byte = *((const unsigned char *)op +
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(((order == MP_MSB_FIRST) ? i : ((count - 1u) - i)) * size) +
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((endian == MP_BIG_ENDIAN) ? (j + nail_bytes) : (((size - 1u) - j) - nail_bytes)));
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if ((err = mp_mul_2d(rop, (j == 0u) ? (int)(8u - odd_nails) : 8, rop)) != MP_OKAY) {
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return err;
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}
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rop->dp[0] |= (j == 0u) ? (mp_digit)(byte & odd_nail_mask) : (mp_digit)byte;
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rop->used += 1;
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}
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}
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mp_clamp(rop);
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return MP_OKAY;
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}
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#endif
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