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[eos/base.git] / util / src / TclTk / tcl8.6.12 / libtommath / bn_mp_div_2d.c

diff --git a/util/src/TclTk/tcl8.6.12/libtommath/bn_mp_div_2d.c b/util/src/TclTk/tcl8.6.12/libtommath/bn_mp_div_2d.c
new file mode 100644 (file)
index 0000000..c47d5ce
--- /dev/null
+++ b/util/src/TclTk/tcl8.6.12/libtommath/bn_mp_div_2d.c
@@ -0,0 +1,71 @@
+#include "tommath_private.h"
+#ifdef BN_MP_DIV_2D_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* shift right by a certain bit count (store quotient in c, optional remainder in d) */
+mp_err mp_div_2d(const mp_int *a, int b, mp_int *c, mp_int *d)
+{
+   mp_digit D, r, rr;
+   int     x;
+   mp_err err;
+
+   /* if the shift count is <= 0 then we do no work */
+   if (b <= 0) {
+      err = mp_copy(a, c);
+      if (d != NULL) {
+         mp_zero(d);
+      }
+      return err;
+   }
+
+   /* copy */
+   if ((err = mp_copy(a, c)) != MP_OKAY) {
+      return err;
+   }
+   /* 'a' should not be used after here - it might be the same as d */
+
+   /* get the remainder */
+   if (d != NULL) {
+      if ((err = mp_mod_2d(a, b, d)) != MP_OKAY) {
+         return err;
+      }
+   }
+
+   /* shift by as many digits in the bit count */
+   if (b >= MP_DIGIT_BIT) {
+      mp_rshd(c, b / MP_DIGIT_BIT);
+   }
+
+   /* shift any bit count < MP_DIGIT_BIT */
+   D = (mp_digit)(b % MP_DIGIT_BIT);
+   if (D != 0u) {
+      mp_digit *tmpc, mask, shift;
+
+      /* mask */
+      mask = ((mp_digit)1 << D) - 1uL;
+
+      /* shift for lsb */
+      shift = (mp_digit)MP_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;
+      }
+   }
+   mp_clamp(c);
+   return MP_OKAY;
+}
+#endif