zig

commit d86cde575239d4e38631d562fba8b4001d436ebd (tree)
parent bcef123d902b9d1d8a27b0414932b1b92f6f1a7e
Author: Frank Denis <github@pureftpd.org>
Date:   Sat, 15 Aug 2020 11:11:33 +0200

Add comment, use @truncate

Diffstat:
M
lib/std/crypto/25519/curve25519.zig
 | 
2
+-
M
lib/std/crypto/25519/edwards25519.zig
 | 
4
++--

2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/lib/std/crypto/25519/curve25519.zig b/lib/std/crypto/25519/curve25519.zig
@@ -43,7 +43,7 @@ pub const Curve25519 = struct {
         var swap: u8 = 0;
         var pos: usize = bits - 1;
         while (true) : (pos -= 1) {
-            const b = (s[pos / 8] >> @intCast(u3, pos & 7)) & 1;
+            const b = (s[pos >> 3] >> @truncate(u3, pos)) & 1;
             swap ^= b;
             Fe.cSwap2(&x2, &x3, &z2, &z3, swap);
             swap = b;
diff --git a/lib/std/crypto/25519/edwards25519.zig b/lib/std/crypto/25519/edwards25519.zig
@@ -28,7 +28,7 @@ pub const Edwards25519 = struct {
         const vxx = x.sq().mul(v);
         const has_m_root = vxx.sub(u).isZero();
         const has_p_root = vxx.add(u).isZero();
-        if ((@boolToInt(has_m_root) | @boolToInt(has_p_root)) == 0) {
+        if ((@boolToInt(has_m_root) | @boolToInt(has_p_root)) == 0) { // best-effort to avoid two conditional branches
             return error.InvalidEncoding;
         }
         x.cMov(x.mul(Fe.sqrtm1), 1 - @boolToInt(has_m_root));
@@ -130,7 +130,7 @@ pub const Edwards25519 = struct {
         var pos: usize = 252;
         while (true) : (pos -= 4) {
             q = q.dbl().dbl().dbl().dbl();
-            const b = (s[pos / 8] >> @intCast(u3, pos & 7)) & 0xf;
+            const b = (s[pos >> 3] >> @truncate(u3, pos)) & 0xf;
             q = q.add(pcSelect(pc, b));
             if (pos == 0) break;
         }