70 lines
1.7 KiB
C
70 lines
1.7 KiB
C
#include "tommath_private.h"
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#ifdef BN_MP_PACK_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_export.
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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_pack(void *rop, size_t maxcount, size_t *written, mp_order order, size_t size,
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mp_endian endian, size_t nails, const mp_int *op)
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{
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mp_err err;
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size_t odd_nails, nail_bytes, i, j, count;
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unsigned char odd_nail_mask;
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mp_int t;
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count = mp_pack_count(op, nails, size);
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if (count > maxcount) {
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return MP_BUF;
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}
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if ((err = mp_init_copy(&t, op)) != MP_OKAY) {
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return err;
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}
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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 = 0u; 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 = 0u; i < count; ++i) {
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for (j = 0u; j < size; ++j) {
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unsigned char *byte = (unsigned char *)rop +
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(((order == MP_LSB_FIRST) ? i : ((count - 1u) - i)) * size) +
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((endian == MP_LITTLE_ENDIAN) ? 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 ((err = mp_div_2d(&t, (j == ((size - nail_bytes) - 1u)) ? (int)(8u - odd_nails) : 8, &t, NULL)) != MP_OKAY) {
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goto LBL_ERR;
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}
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}
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}
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if (written != NULL) {
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*written = count;
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}
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err = MP_OKAY;
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LBL_ERR:
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mp_clear(&t);
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return err;
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}
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#endif
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