Start experimenting with full generation of all of the numeric types.

Previously, we used a little bit of generation to drive a lot of Rust
macros. This works, but it's a little confusing to read and write. In
addition, we used a lot of implementations with variable timings based
on their input, which isn't great for crypto. This is the start of an
attempt to just generate all of the relevant Rust code directly, and to
use timing-channel resistant implementations for most of the routines.

old/unsigned/mul.rs

@@ -0,0 +1,142 @@
+pub fn multiply(dest: &mut [u64], left: &[u64], right: &[u64])
+{
+    let len = right.len();
+    let mut i = 0;
+
+    assert_eq!(left.len(), len,   "Uneven argument lengths in multiply");
+    assert_eq!(dest.len(), len*2, "Bad destination size in multiply");
+
+    while i < len {
+        let mut carry = 0;
+        let mut j = 0;
+
+        while j < len {
+            let old = dest[i+j] as u128;
+            let l128 = left[j] as u128;
+            let r128 = right[i] as u128;
+            let uv = old + (l128 * r128) + carry;
+            dest[i+j] = uv as u64;
+            carry = uv >> 64;
+            j += 1;
+        }
+        dest[i+len] = carry as u64;
+        i += 1;
+    }
+}
+
+pub fn multiply_small(dest: &mut [u64], left: &[u64], right: &[u64])
+{
+    let len = right.len();
+
+    assert_eq!(dest.len(), len);
+    assert_eq!(left.len(), len);
+    for i in 0..len { dest[i] = 0; }
+    for i in 0..len {
+        let mut carry = 0;
+
+        for j in 0..len {
+            if i+j >= len {
+                carry = 0;
+                continue;
+            }
+            let old = dest[i+j] as u128;
+            let l128 = left[j] as u128;
+            let r128 = right[i] as u128;
+            let uv = old + (l128 * r128) + carry;
+            dest[i+j] = uv as u64;
+            carry = uv >> 64;
+        }
+    }
+}
+
+macro_rules! multiply_impls {
+    ($name: ident, $dbl: ident) => {
+        impl Mul<$name> for $name {
+            type Output = $dbl;
+
+            fn mul(self, rhs: $name) -> $dbl {
+                let mut res = $dbl::zero();
+                multiply(&mut res.value, &self.value, &rhs.value);
+                res
+            }
+        }
+
+        impl<'a> Mul<$name> for &'a $name {
+            type Output = $dbl;
+
+            fn mul(self, rhs: $name) -> $dbl {
+                let mut res = $dbl::zero();
+                multiply(&mut res.value, &self.value, &rhs.value);
+                res
+            }
+        }
+
+        impl<'a> Mul<&'a $name> for $name {
+            type Output = $dbl;
+
+            fn mul(self, rhs: &$name) -> $dbl {
+                let mut res = $dbl::zero();
+                multiply(&mut res.value, &self.value, &rhs.value);
+                res
+            }
+        }
+
+        impl<'a,'b> Mul<&'a $name> for &'b $name {
+            type Output = $dbl;
+
+            fn mul(self, rhs: &$name) -> $dbl {
+                let mut res = $dbl::zero();
+                multiply(&mut res.value, &self.value, &rhs.value);
+                res
+            }
+        }
+
+        impl MulAssign for $name {
+            fn mul_assign(&mut self, rhs: $name) {
+                let copy = self.value.clone();
+                multiply_small(&mut self.value, &copy, &rhs.value);
+            }
+        }
+
+        impl<'a> MulAssign<&'a $name> for $name {
+            fn mul_assign(&mut self, rhs: &$name) {
+                let copy = self.value.clone();
+                multiply_small(&mut self.value, &copy, &rhs.value);
+            }
+        }
+    };
+}
+
+#[cfg(test)]
+macro_rules! generate_mul_tests
+{
+    ($name: ident, $lname: ident, $dbl: ident) => {
+        #[test]
+        fn $lname() {
+            generate_mul_tests!(body $name, $lname, $dbl);
+        }
+    };
+    (ignore $name: ident, $lname: ident, $dbl: ident) => {
+        #[test]
+        #[ignore]
+        fn $lname() {
+            generate_mul_tests!(body $name, $lname, $dbl);
+        }
+    };
+    (body $name: ident, $lname: ident, $dbl: ident) => {
+        let fname = build_test_path("mul", stringify!($name));
+        run_test(fname.to_string(), 3, |case| {
+            let (neg0, abytes) = case.get("a").unwrap();
+            let (neg1, bbytes) = case.get("b").unwrap();
+            let (neg2, cbytes) = case.get("c").unwrap();
+            assert!(!neg0 && !neg1 && !neg2);
+
+            let mut a = $name::from_bytes(abytes);
+            let b = $name::from_bytes(bbytes);
+            let c = $dbl::from_bytes(cbytes);
+            assert_eq!(c, &a * &b, "standard multiplication");
+            a *= b;
+            assert_eq!($name::from(c), a);
+        });
+    };
+}