85 lines
2.2 KiB
C
85 lines
2.2 KiB
C
#include "tommath_private.h"
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#ifdef BN_MP_EXPORT_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is a library that provides multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library was designed directly after the MPI library by
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* Michael Fromberger but has been written from scratch with
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* additional optimizations in place.
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*
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* SPDX-License-Identifier: Unlicense
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*/
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/* based on gmp's mpz_export.
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* see http://gmplib.org/manual/Integer-Import-and-Export.html
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*/
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int mp_export(void *rop, size_t *countp, int order, size_t size,
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int endian, size_t nails, const mp_int *op)
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{
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int result;
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size_t odd_nails, nail_bytes, i, j, bits, count;
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unsigned char odd_nail_mask;
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mp_int t;
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if ((result = mp_init_copy(&t, op)) != MP_OKAY) {
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return result;
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}
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if (endian == 0) {
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union {
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unsigned int i;
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char c[4];
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} lint;
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lint.i = 0x01020304;
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endian = (lint.c[0] == '\x04') ? -1 : 1;
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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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bits = (size_t)mp_count_bits(&t);
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count = (bits / ((size * 8u) - nails)) + (((bits % ((size * 8u) - nails)) != 0u) ? 1u : 0u);
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for (i = 0; i < count; ++i) {
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for (j = 0; j < size; ++j) {
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unsigned char *byte = (unsigned char *)rop +
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(((order == -1) ? i : ((count - 1u) - i)) * size) +
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((endian == -1) ? j : ((size - 1u) - j));
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if (j >= (size - nail_bytes)) {
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*byte = 0;
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continue;
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}
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*byte = (unsigned char)((j == ((size - nail_bytes) - 1u)) ? (t.dp[0] & odd_nail_mask) : (t.dp[0] & 0xFFuL));
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if ((result = mp_div_2d(&t, (j == ((size - nail_bytes) - 1u)) ? (int)(8u - odd_nails) : 8, &t, NULL)) != MP_OKAY) {
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mp_clear(&t);
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return result;
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}
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}
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}
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mp_clear(&t);
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if (countp != NULL) {
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*countp = count;
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}
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return MP_OKAY;
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}
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#endif
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/* ref: $Format:%D$ */
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/* git commit: $Format:%H$ */
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/* commit time: $Format:%ai$ */
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