--- /dev/null
+/* TomsFastMath, a fast ISO C bignum library.
+ *
+ * This project is meant to fill in where LibTomMath
+ * falls short. That is speed ;-)
+ *
+ * This project is public domain and free for all purposes.
+ *
+ * Tom St Denis, tomstdenis@gmail.com
+ */
+#include <tfm_private.h>
+
+/* c = a / 2**b */
+void fp_div_2d(fp_int *a, int b, fp_int *c, fp_int *d)
+{
+ fp_digit D, r, rr;
+ int x;
+ fp_int t;
+
+ /* if the shift count is <= 0 then we do no work */
+ if (b <= 0) {
+ fp_copy (a, c);
+ if (d != NULL) {
+ fp_zero (d);
+ }
+ return;
+ }
+
+ fp_init(&t);
+
+ /* get the remainder */
+ if (d != NULL) {
+ fp_mod_2d (a, b, &t);
+ }
+
+ /* copy */
+ fp_copy(a, c);
+
+ /* shift by as many digits in the bit count */
+ if (b >= (int)DIGIT_BIT) {
+ fp_rshd (c, b / DIGIT_BIT);
+ }
+
+ /* shift any bit count < DIGIT_BIT */
+ D = (fp_digit) (b % DIGIT_BIT);
+ if (D != 0) {
+ register fp_digit *tmpc, mask, shift;
+
+ /* mask */
+ mask = (((fp_digit)1) << D) - 1;
+
+ /* shift for lsb */
+ shift = DIGIT_BIT - D;
+
+ /* alias */
+ tmpc = c->dp + (c->used - 1);
+
+ /* carry */
+ r = 0;
+ for (x = c->used - 1; x >= 0; x--) {
+ /* get the lower bits of this word in a temp */
+ rr = *tmpc & mask;
+
+ /* shift the current word and mix in the carry bits from the previous word */
+ *tmpc = (*tmpc >> D) | (r << shift);
+ --tmpc;
+
+ /* set the carry to the carry bits of the current word found above */
+ r = rr;
+ }
+ }
+ fp_clamp (c);
+ if (d != NULL) {
+ fp_copy (&t, d);
+ }
+}
+
+/* $Source$ */
+/* $Revision$ */
+/* $Date$ */