From ad3496a66d2810c2368bc86bd2904255d48e214e Mon Sep 17 00:00:00 2001
From: Dirk Engling <erdgeist@erdgeist.org>
Date: Mon, 15 Jul 2013 14:41:24 +0200
Subject: Stable version

---
 sqr.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 sqr.c

diff --git a/sqr.c b/sqr.c
new file mode 100644
index 0000000..f4826e7
--- /dev/null
+++ b/sqr.c
@@ -0,0 +1,96 @@
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+
+typedef uint8_t leg_t;
+typedef uint16_t dleg_t;
+
+#if 0
+static void mp_sqr( leg_t *result, leg_t const * a, int legs )
+{
+  while( legs-- ) {
+    leg_t *offs = result+2*legs+1;
+    leg_t fac = a[legs];
+    int leg = legs;
+    dleg_t acc = (dleg_t)*offs + (dleg_t)fac * fac;
+
+    *(offs--) = (leg_t)acc;
+    acc >>= 8*sizeof(leg_t);
+
+    while( leg-- )
+    {
+      dleg_t subresult = fac * a[leg];
+      int carry = !!(subresult & (1<<(8*sizeof(dleg_t)-1)));
+
+      subresult <<= 1;
+      acc += subresult + *offs;
+
+      *(offs--) = (leg_t)acc;
+      acc >>= 8*sizeof(leg_t);
+      acc += carry;
+    }
+
+    while( acc )
+    {
+      acc += *offs;
+      *(offs--) = (leg_t)acc;
+      acc >>= 8*sizeof(leg_t);
+    }
+  }
+}
+#else
+static void mp_sqr( leg_t *result, leg_t const * a, int legs )
+{
+int i;
+  while( legs-- ) {
+    leg_t *offs = result+2*legs+1;
+    leg_t fac = a[legs];
+    int leg = legs,i;
+    dleg_t acc = (dleg_t)*offs + (dleg_t)fac * (dleg_t)fac;
+
+    *(offs--) = (leg_t)acc;
+    acc >>= 8*sizeof(leg_t);
+
+    while( leg-- )
+    {
+      dleg_t subresult = (dleg_t)fac * (dleg_t)a[leg];
+      int carry = 1 & ( subresult >> (16*sizeof(leg_t)-1));
+
+      subresult ^= carry << (16*sizeof(leg_t)-1);
+
+      acc += 2 * subresult + (dleg_t)*offs;
+      *(offs--) = (leg_t)acc;
+
+      acc >>= 8*sizeof(leg_t);
+      acc += (dleg_t)carry << 8*sizeof(leg_t);
+
+printf( "%04X %04X %d\n", acc, subresult, carry );
+
+    }
+  for(i=0;i<6;++i)
+    printf( "%02X", result[i] );
+
+  putchar(10);
+    while( acc )
+    {
+      acc += (dleg_t)*offs;
+      *(offs--) = (leg_t)acc;
+      acc >>= 8*sizeof(leg_t);
+    }
+  }
+  for(i=0;i<6;++i)
+    printf( "%02X", result[i] );
+  putchar(10);
+ }
+#endif
+
+int main() {
+  leg_t a[3] = { 0xff, 0xff, 0xa1 };
+  leg_t r[6] = {0,0,0,0,0,0};
+  int i;
+
+  mp_sqr( r, a, 3 );
+  for(i=0;i<6;++i)
+    printf( "%02X", r[i] );
+  putchar(10);
+}
-- 
cgit v1.2.3