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annotate tomsfastmath/src/bin/fp_read_unsigned_bin.c @ 643:a362b62d38b2 dropbear-tfm

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Add tomsfastmath from git rev bfa4582842bc3bab42e4be4aed5703437049502a with Makefile.in renamed
author Matt Johnston <matt@ucc.asn.au>
date Wed, 23 Nov 2011 18:10:20 +0700
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a362b62d38b2 Add tomsfastmath from git rev bfa4582842bc3bab42e4be4aed5703437049502a
Matt Johnston <matt@ucc.asn.au>
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1 /* TomsFastMath, a fast ISO C bignum library.
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2 *
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3 * This project is meant to fill in where LibTomMath
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4 * falls short. That is speed ;-)
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5 *
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6 * This project is public domain and free for all purposes.
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7 *
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8 * Tom St Denis, [email protected]
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9 */
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10 #include <tfm.h>
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12 void fp_read_unsigned_bin(fp_int *a, unsigned char *b, int c)
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13 {
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14 /* zero the int */
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15 fp_zero (a);
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17 /* If we know the endianness of this architecture, and we're using
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18 32-bit fp_digits, we can optimize this */
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19 #if (defined(ENDIAN_LITTLE) || defined(ENDIAN_BIG)) && !defined(FP_64BIT)
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20 /* But not for both simultaneously */
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21 #if defined(ENDIAN_LITTLE) && defined(ENDIAN_BIG)
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22 #error Both ENDIAN_LITTLE and ENDIAN_BIG defined.
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23 #endif
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24 {
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25 unsigned char *pd = (unsigned char *)a->dp;
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26
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27 if ((unsigned)c > (FP_SIZE * sizeof(fp_digit))) {
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28 int excess = c - (FP_SIZE * sizeof(fp_digit));
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29 c -= excess;
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30 b += excess;
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31 }
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32 a->used = (c + sizeof(fp_digit) - 1)/sizeof(fp_digit);
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33 /* read the bytes in */
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34 #ifdef ENDIAN_BIG
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35 {
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36 /* Use Duff's device to unroll the loop. */
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37 int idx = (c - 1) & ~3;
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38 switch (c % 4) {
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39 case 0: do { pd[idx+0] = *b++;
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40 case 3: pd[idx+1] = *b++;
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41 case 2: pd[idx+2] = *b++;
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42 case 1: pd[idx+3] = *b++;
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43 idx -= 4;
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44 } while ((c -= 4) > 0);
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45 }
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46 }
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47 #else
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48 for (c -= 1; c >= 0; c -= 1) {
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49 pd[c] = *b++;
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50 }
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51 #endif
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52 }
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53 #else
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54 /* read the bytes in */
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55 for (; c > 0; c--) {
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56 fp_mul_2d (a, 8, a);
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57 a->dp[0] |= *b++;
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58 a->used += 1;
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59 }
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60 #endif
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61 fp_clamp (a);
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62 }
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63
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64 /* $Source$ */
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65 /* $Revision$ */
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66 /* $Date$ */