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/scale.rs

@@ -0,0 +1,93 @@
+pub fn scale(dest: &mut [u64], bignum: &[u64], factor: u64)
+{
+    let len = bignum.len();
+    let factor128 = factor as u128;
+    let mut carry = 0;
+
+    assert_eq!(dest.len(), len+1, "Bad destination size in scale");
+    for i in 0..len {
+        let digit128 = bignum[i] as u128;
+        let res128 = carry + (digit128 * factor128);
+        dest[i] = res128 as u64;
+        carry = res128 >> 64;
+    }
+    dest[len] = carry as u64;
+}
+
+macro_rules! scale_impls
+{
+    ($base: ident, $big: ident) => {
+        scale_impls!($base, $big, u8);
+        scale_impls!($base, $big, u16);
+        scale_impls!($base, $big, u32);
+        scale_impls!($base, $big, u64);
+        scale_impls!($base, $big, usize);
+    };
+    ($base: ident, $big: ident, $prim: ident) => {
+        impl Mul<$prim> for $base {
+            type Output = $big;
+
+            fn mul(self, factor: $prim) -> $big {
+                &self * factor
+            }
+        }
+
+        impl<'a> Mul<$prim> for &'a $base {
+            type Output = $big;
+
+            fn mul(self, factor: $prim) -> $big {
+                let mut res = $big::zero();
+                scale(&mut res.value, &self.value, factor as u64);
+                res
+            }
+        }
+
+        impl Mul<$base> for $prim {
+            type Output = $big;
+
+            fn mul(self, rhs: $base) -> $big {
+                rhs.mul(self)
+            }
+        }
+
+        impl<'a> Mul<&'a $base> for $prim {
+            type Output = $big;
+
+            fn mul(self, rhs: &$base) -> $big {
+                rhs.mul(self)
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+macro_rules! generate_scale_tests
+{
+    ($name: ident, $lname: ident, $big: ident) => {
+        #[test]
+        fn $lname() {
+            generate_scale_tests!(body $name, $lname, $big);
+        }
+    };
+    (ignore $name: ident, $lname: ident, $big: ident) => {
+        #[test]
+        #[ignore]
+        fn $lname() {
+            generate_scale_tests!(body $name, $lname, $big);
+        }
+    };
+    (body $name: ident, $lname: ident, $big: ident) => {
+        let fname = build_test_path("scale", stringify!($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 a = $name::from_bytes(abytes);
+            let b = $name::from_bytes(bbytes);
+            let c = $big::from_bytes(cbytes);
+            assert_eq!(c, &a * b.value[0]);
+        });
+    };
+}