util Algorithm
The term was introduced initially as a measure of pleasure or satisfaction within the theory of utilitarianism by moral philosophers such as Jeremy Bentham and John Stuart Mill. The term has been adapted and reapplied within neoclassical economics, which dominates modern economic theory, as a utility function that represents a consumer's preference ordering over a choice set.
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use libc;
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
extern {
pub fn rust_crypto_util_supports_aesni() -> u32;
}
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
pub fn supports_aesni() -> bool {
unsafe {
rust_crypto_util_supports_aesni() != 0
}
}
extern {
pub fn rust_crypto_util_fixed_time_eq_asm(
lhsp: *const u8,
rhsp: *const u8,
count: libc::size_t) -> u32;
pub fn rust_crypto_util_secure_memset(
dst: *mut u8,
val: libc::uint8_t,
count: libc::size_t);
}
pub fn secure_memset(dst: &mut [u8], val: u8) {
unsafe {
rust_crypto_util_secure_memset(
dst.as_mut_ptr(),
val,
dst.len() as libc::size_t);
}
}
/// Compare two vectors using a fixed number of operations. If the two vectors are not of equal
/// length, the function returns false immediately.
pub fn fixed_time_eq(lhs: &[u8], rhs: &[u8]) -> bool {
if lhs.len() != rhs.len() {
false
} else {
let count = lhs.len() as libc::size_t;
unsafe {
let lhsp = lhs.get_unchecked(0);
let rhsp = rhs.get_unchecked(0);
rust_crypto_util_fixed_time_eq_asm(lhsp, rhsp, count) == 0
}
}
}
#[cfg(test)]
mod test {
use util::fixed_time_eq;
#[test]
pub fn test_fixed_time_eq() {
let a = [0, 1, 2];
let b = [0, 1, 2];
let c = [0, 1, 9];
let d = [9, 1, 2];
let e = [2, 1, 0];
let f = [2, 2, 2];
let g = [0, 0, 0];
assert!(fixed_time_eq(&a, &a));
assert!(fixed_time_eq(&a, &b));
assert!(!fixed_time_eq(&a, &c));
assert!(!fixed_time_eq(&a, &d));
assert!(!fixed_time_eq(&a, &e));
assert!(!fixed_time_eq(&a, &f));
assert!(!fixed_time_eq(&a, &g));
}
}
