hare

commit 51a5967b76054aaec20930d0d03c575ff8d22d24
parent 1c1287bd183027172b7d7ccebd5cb5c55c4309b6
Author: Drew DeVault <sir@cmpwn.com>
Date:   Fri, 26 Feb 2021 12:28:47 -0500

crypto::math: new module (WIP)

Diffstat:
A
crypto/math/bits.ha
 | 
22
++++++++++++++++++++++

1 file changed, 22 insertions(+), 0 deletions(-)
diff --git a/crypto/math/bits.ha b/crypto/math/bits.ha
@@ -0,0 +1,22 @@
+// crypto::math provides constant-time mathematical operations useful for
+// cryptographic algorithms.
+
+// Rotates a 32-bit unsigned integer left by k bits. k may be negative to rotate
+// right instead, or see [rotr32].
+export fn rotl32(x: u32, k: int) u32 = {
+	const n = 32u32;
+	const s = k: u32 & (n - 1);
+	return x << s | x >> (n - s);
+};
+
+// Rotates a 32-bit unsigned integer right by k bits. k may be negative to
+// rotate left instead, or see [rotl32].
+export fn rotr32(x: u32, k: int) u32 = rotl32(x, -k);
+
+@test fn lrot32() void = {
+	let a = 0b11110000111100001111000011110000u32;
+	assert(rotl32(a, 2) == 0b11000011110000111100001111000011u32);
+	assert(rotl32(a, -2) == 0b00111100001111000011110000111100u32);
+	assert(rotl32(a, 32) == 0b11110000111100001111000011110000u32);
+	assert(rotl32(a, 64) == 0b11110000111100001111000011110000u32);
+};