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/signed/moddiv.rs

@@ -0,0 +1,54 @@
+/// Computations of the modular inverse.
+pub trait ModDiv: Sized {
+    /// Compute the modular division of the number by the given number and
+    /// modulus. The divisor *must* have a modular inverse for this function
+    /// to succeed.
+    fn moddiv(&self, divisor: &Self, phi: &Self) -> Self;
+}
+
+macro_rules! moddiv_impls {
+    ($sname: ident, $dbl: ident) => {
+        impl ModDiv for $sname {
+            fn moddiv(&self, divisor: &Self, phi: &Self) -> Self
+            {
+                let safe_divisor = divisor % phi;
+                let i = safe_divisor.modinv(&phi).expect("no modular inverse of moddiv divisor");
+                let selfi = i * self;
+                $sname::from( selfi % $dbl::from(phi) )
+            }
+        }
+    };
+}
+
+#[cfg(test)]
+macro_rules! generate_moddiv_tests {
+    ($sname: ident, $tname: ident, $mname: ident) => {
+        #[test]
+        fn $mname() {
+            generate_moddiv_tests!(body $sname, $tname, $mname);
+        }
+    };
+    (ignore $sname: ident, $tname: ident, $mname: ident) => {
+        #[test]
+        #[ignore]
+        fn $mname() {
+            generate_moddiv_tests!(body $sname, $tname, $mname);
+        }
+    };
+    (body $sname: ident, $tname: ident, $mname: ident) => {
+        let fname = build_test_path("moddiv", stringify!($sname));
+        run_test(fname.to_string(), 4, |case| {
+            let (nega, abytes) = case.get("a").unwrap();
+            let (negb, bbytes) = case.get("b").unwrap();
+            let (negm, mbytes) = case.get("m").unwrap();
+            let (negc, cbytes) = case.get("c").unwrap();
+
+            let a = $sname::new(*nega, $tname::from_bytes(abytes));
+            let b = $sname::new(*negb, $tname::from_bytes(bbytes));
+            let m = $sname::new(*negm, $tname::from_bytes(mbytes));
+            let c = $sname::new(*negc, $tname::from_bytes(cbytes));
+            let res = a.moddiv(&b, &m);
+            assert_eq!(c, res);
+        });
+    };
+}