88 lines
2.0 KiB
C
88 lines
2.0 KiB
C
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#include <tommath.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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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
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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, mp_int* op) {
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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 = {0x01020304};
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endian = (lint.c[0] == 4 ? -1 : 1);
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}
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odd_nails = (nails % 8);
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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 ^= (1 << (7 - i));
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}
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nail_bytes = nails / 8;
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bits = mp_count_bits(&t);
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count = bits / (size * 8 - nails) + (bits % (size * 8 - nails) ? 1 : 0);
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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 = (
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(unsigned char*)rop +
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(order == -1 ? i : count - 1 - i) * size +
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(endian == -1 ? j : size - 1 - j)
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);
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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 - 1 ? (t.dp[0] & odd_nail_mask) : t.dp[0] & 0xFF);
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if ((result = mp_div_2d(&t, (j == size - nail_bytes - 1 ? 8 - 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) {
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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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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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