ARM Shanghai IoT Team (Internal) / newMiniTLS-GPL

change some parameters in the library to meet the needs of the website httpbin.org

Fork of MiniTLS-GPL by Donatien Garnier

math/divide/fp_div_d.c@5:95f70ebfe61f, 2015-02-06 (annotated)

Committer:
shiyilei
Date:
Fri Feb 06 06:17:33 2015 +0000
Revision:
5:95f70ebfe61f
Parent:
0:35aa5be3b78d 
change some parameters in the library to meet the needs of httpbin.org

Who changed what in which revision?

UserRevisionLine numberNew contents of line
MiniTLS 0:35aa5be3b78d 1 /* TomsFastMath, a fast ISO C bignum library.
MiniTLS 0:35aa5be3b78d 2 *
MiniTLS 0:35aa5be3b78d 3 * This project is meant to fill in where LibTomMath
MiniTLS 0:35aa5be3b78d 4 * falls short. That is speed ;-)
MiniTLS 0:35aa5be3b78d 5 *
MiniTLS 0:35aa5be3b78d 6 * This project is public domain and free for all purposes.
MiniTLS 0:35aa5be3b78d 7 *
MiniTLS 0:35aa5be3b78d 8 * Tom St Denis, tomstdenis@gmail.com
MiniTLS 0:35aa5be3b78d 9 */
MiniTLS 0:35aa5be3b78d 10 #include <tfm.h>
MiniTLS 0:35aa5be3b78d 11
MiniTLS 0:35aa5be3b78d 12 static int s_is_power_of_two(fp_digit b, int *p)
MiniTLS 0:35aa5be3b78d 13 {
MiniTLS 0:35aa5be3b78d 14 int x;
MiniTLS 0:35aa5be3b78d 15
MiniTLS 0:35aa5be3b78d 16 /* fast return if no power of two */
MiniTLS 0:35aa5be3b78d 17 if ((b==0) || (b & (b-1))) {
MiniTLS 0:35aa5be3b78d 18 return 0;
MiniTLS 0:35aa5be3b78d 19 }
MiniTLS 0:35aa5be3b78d 20
MiniTLS 0:35aa5be3b78d 21 for (x = 0; x < DIGIT_BIT; x++) {
MiniTLS 0:35aa5be3b78d 22 if (b == (((fp_digit)1)<<x)) {
MiniTLS 0:35aa5be3b78d 23 *p = x;
MiniTLS 0:35aa5be3b78d 24 return 1;
MiniTLS 0:35aa5be3b78d 25 }
MiniTLS 0:35aa5be3b78d 26 }
MiniTLS 0:35aa5be3b78d 27 return 0;
MiniTLS 0:35aa5be3b78d 28 }
MiniTLS 0:35aa5be3b78d 29
MiniTLS 0:35aa5be3b78d 30 /* a/b => cb + d == a */
MiniTLS 0:35aa5be3b78d 31 int fp_div_d(fp_int *a, fp_digit b, fp_int *c, fp_digit *d)
MiniTLS 0:35aa5be3b78d 32 {
MiniTLS 0:35aa5be3b78d 33 fp_int q;
MiniTLS 0:35aa5be3b78d 34 fp_word w;
MiniTLS 0:35aa5be3b78d 35 fp_digit t;
MiniTLS 0:35aa5be3b78d 36 int ix;
MiniTLS 0:35aa5be3b78d 37
MiniTLS 0:35aa5be3b78d 38 /* cannot divide by zero */
MiniTLS 0:35aa5be3b78d 39 if (b == 0) {
MiniTLS 0:35aa5be3b78d 40 return FP_VAL;
MiniTLS 0:35aa5be3b78d 41 }
MiniTLS 0:35aa5be3b78d 42
MiniTLS 0:35aa5be3b78d 43 /* quick outs */
MiniTLS 0:35aa5be3b78d 44 if (b == 1 || fp_iszero(a) == 1) {
MiniTLS 0:35aa5be3b78d 45 if (d != NULL) {
MiniTLS 0:35aa5be3b78d 46 *d = 0;
MiniTLS 0:35aa5be3b78d 47 }
MiniTLS 0:35aa5be3b78d 48 if (c != NULL) {
MiniTLS 0:35aa5be3b78d 49 fp_copy(a, c);
MiniTLS 0:35aa5be3b78d 50 }
MiniTLS 0:35aa5be3b78d 51 return FP_OKAY;
MiniTLS 0:35aa5be3b78d 52 }
MiniTLS 0:35aa5be3b78d 53
MiniTLS 0:35aa5be3b78d 54 /* power of two ? */
MiniTLS 0:35aa5be3b78d 55 if (s_is_power_of_two(b, &ix) == 1) {
MiniTLS 0:35aa5be3b78d 56 if (d != NULL) {
MiniTLS 0:35aa5be3b78d 57 *d = a->dp[0] & ((((fp_digit)1)<<ix) - 1);
MiniTLS 0:35aa5be3b78d 58 }
MiniTLS 0:35aa5be3b78d 59 if (c != NULL) {
MiniTLS 0:35aa5be3b78d 60 fp_div_2d(a, ix, c, NULL);
MiniTLS 0:35aa5be3b78d 61 }
MiniTLS 0:35aa5be3b78d 62 return FP_OKAY;
MiniTLS 0:35aa5be3b78d 63 }
MiniTLS 0:35aa5be3b78d 64
MiniTLS 0:35aa5be3b78d 65 /* no easy answer [c'est la vie]. Just division */
MiniTLS 0:35aa5be3b78d 66 fp_init(&q);
MiniTLS 0:35aa5be3b78d 67
MiniTLS 0:35aa5be3b78d 68 q.used = a->used;
MiniTLS 0:35aa5be3b78d 69 q.sign = a->sign;
MiniTLS 0:35aa5be3b78d 70 w = 0;
MiniTLS 0:35aa5be3b78d 71 for (ix = a->used - 1; ix >= 0; ix--) {
MiniTLS 0:35aa5be3b78d 72 w = (w << ((fp_word)DIGIT_BIT)) | ((fp_word)a->dp[ix]);
MiniTLS 0:35aa5be3b78d 73
MiniTLS 0:35aa5be3b78d 74 if (w >= b) {
MiniTLS 0:35aa5be3b78d 75 t = (fp_digit)(w / b);
MiniTLS 0:35aa5be3b78d 76 w -= ((fp_word)t) * ((fp_word)b);
MiniTLS 0:35aa5be3b78d 77 } else {
MiniTLS 0:35aa5be3b78d 78 t = 0;
MiniTLS 0:35aa5be3b78d 79 }
MiniTLS 0:35aa5be3b78d 80 q.dp[ix] = (fp_digit)t;
MiniTLS 0:35aa5be3b78d 81 }
MiniTLS 0:35aa5be3b78d 82
MiniTLS 0:35aa5be3b78d 83 if (d != NULL) {
MiniTLS 0:35aa5be3b78d 84 *d = (fp_digit)w;
MiniTLS 0:35aa5be3b78d 85 }
MiniTLS 0:35aa5be3b78d 86
MiniTLS 0:35aa5be3b78d 87 if (c != NULL) {
MiniTLS 0:35aa5be3b78d 88 fp_clamp(&q);
MiniTLS 0:35aa5be3b78d 89 fp_copy(&q, c);
MiniTLS 0:35aa5be3b78d 90 }
MiniTLS 0:35aa5be3b78d 91
MiniTLS 0:35aa5be3b78d 92 return FP_OKAY;
MiniTLS 0:35aa5be3b78d 93 }
MiniTLS 0:35aa5be3b78d 94
MiniTLS 0:35aa5be3b78d 95
MiniTLS 0:35aa5be3b78d 96 /* $Source: /cvs/libtom/tomsfastmath/src/divide/fp_div_d.c,v $ */
MiniTLS 0:35aa5be3b78d 97 /* $Revision: 1.2 $ */
MiniTLS 0:35aa5be3b78d 98 /* $Date: 2007/01/12 15:13:54 $ */