Diff: math/sqr/fp_sqr_comba_generic.c

Revision:

4:cbaf466d717d

Parent:

0:35aa5be3b78d

diff -r eb324ffffd2b -r cbaf466d717d math/sqr/fp_sqr_comba_generic.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/math/sqr/fp_sqr_comba_generic.c	Tue Jun 10 14:23:09 2014 +0000
@@ -0,0 +1,95 @@
+/* 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
+ */
+
+#define TFM_DEFINES
+#include "fp_sqr_comba.c"
+
+/* generic comba squarer */
+void fp_sqr_comba(fp_int *A, fp_int *B)
+{
+  int       pa, ix, iz;
+  fp_digit  c0, c1, c2;
+  fp_int    tmp, *dst;
+#ifdef TFM_ISO
+  fp_word   tt;
+#endif    
+
+  /* get size of output and trim */
+  pa = A->used + A->used;
+  if (pa >= FP_SIZE) {
+     pa = FP_SIZE-1;
+  }
+
+  /* number of output digits to produce */
+  COMBA_START;
+  CLEAR_CARRY;
+
+  if (A == B) {
+     fp_zero(&tmp);
+     dst = &tmp;
+  } else {
+     fp_zero(B);
+     dst = B;
+  }
+
+  for (ix = 0; ix < pa; ix++) { 
+      int      tx, ty, iy;
+      fp_digit *tmpy, *tmpx;
+
+      /* get offsets into the two bignums */
+      ty = MIN(A->used-1, ix);
+      tx = ix - ty;
+
+      /* setup temp aliases */
+      tmpx = A->dp + tx;
+      tmpy = A->dp + ty;
+
+      /* this is the number of times the loop will iterrate,
+         while (tx++ < a->used && ty-- >= 0) { ... }
+       */
+      iy = MIN(A->used-tx, ty+1);
+
+      /* now for squaring tx can never equal ty 
+       * we halve the distance since they approach 
+       * at a rate of 2x and we have to round because 
+       * odd cases need to be executed
+       */
+      iy = MIN(iy, (ty-tx+1)>>1);
+
+      /* forward carries */
+      CARRY_FORWARD;
+
+      /* execute loop */
+      for (iz = 0; iz < iy; iz++) {
+          SQRADD2(*tmpx++, *tmpy--);
+      }
+
+      /* even columns have the square term in them */
+      if ((ix&1) == 0) {
+          SQRADD(A->dp[ix>>1], A->dp[ix>>1]);
+      }
+
+      /* store it */
+      COMBA_STORE(dst->dp[ix]);
+  }
+
+  COMBA_FINI;
+
+  /* setup dest */
+  dst->used = pa;
+  fp_clamp (dst);
+  if (dst != B) {
+     fp_copy(dst, B);
+  }
+}
+
+/* $Source: /cvs/libtom/tomsfastmath/src/sqr/Attic/fp_sqr_comba_generic.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2007/02/15 00:31:32 $ */