forked from ibphoenix/tomsfastmath
67 lines
1.6 KiB
C
67 lines
1.6 KiB
C
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/* TomsFastMath, a fast ISO C bignum library.
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*
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* This project is meant to fill in where LibTomMath
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* falls short. That is speed ;-)
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*
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* This project is public domain and free for all purposes.
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*
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* Tom St Denis, tomstdenis@gmail.com
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*/
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#include <tfm.h>
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void fp_read_unsigned_bin(fp_int *a, unsigned char *b, int c)
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{
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/* zero the int */
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fp_zero (a);
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/* If we know the endianness of this architecture, and we're using
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32-bit fp_digits, we can optimize this */
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#if (defined(ENDIAN_LITTLE) || defined(ENDIAN_BIG)) && !defined(FP_64BIT)
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/* But not for both simultaneously */
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#if defined(ENDIAN_LITTLE) && defined(ENDIAN_BIG)
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#error Both ENDIAN_LITTLE and ENDIAN_BIG defined.
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#endif
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{
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unsigned char *pd = (unsigned char *)a->dp;
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if ((unsigned)c > (FP_SIZE * sizeof(fp_digit))) {
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int excess = c - (FP_SIZE * sizeof(fp_digit));
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c -= excess;
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b += excess;
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}
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a->used = (c + sizeof(fp_digit) - 1)/sizeof(fp_digit);
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/* read the bytes in */
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#ifdef ENDIAN_BIG
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{
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/* Use Duff's device to unroll the loop. */
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int idx = (c - 1) & ~3;
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switch (c % 4) {
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case 0: do { pd[idx+0] = *b++;
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case 3: pd[idx+1] = *b++;
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case 2: pd[idx+2] = *b++;
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case 1: pd[idx+3] = *b++;
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idx -= 4;
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} while ((c -= 4) > 0);
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}
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}
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#else
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for (c -= 1; c >= 0; c -= 1) {
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pd[c] = *b++;
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}
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#endif
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}
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#else
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/* read the bytes in */
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for (; c > 0; c--) {
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fp_mul_2d (a, 8, a);
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a->dp[0] |= *b++;
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a->used += 1;
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}
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#endif
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fp_clamp (a);
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}
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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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