pub const fn murmur3_32(buf: &str) -> u32 {
const fn pre_mix(buf: [u8; 4]) -> u32 {
u32::from_le_bytes(buf)
.wrapping_mul(0xcc9e2d51)
.rotate_left(15)
.wrapping_mul(0x1b873593)
}
let mut hash = 0;
let mut i = 0;
let buf = buf.as_bytes();
while i < buf.len() / 4 {
let buf = [buf[i * 4], buf[i * 4 + 1], buf[i * 4 + 2], buf[i * 4 + 3]];
hash ^= pre_mix(buf);
hash = hash.rotate_left(13);
hash = hash.wrapping_mul(5).wrapping_add(0xe6546b64);
i += 1;
}
match buf.len() % 4 {
0 => {}
1 => {
hash = hash ^ pre_mix([buf[i * 4], 0, 0, 0]);
}
2 => {
hash = hash ^ pre_mix([buf[i * 4], buf[i * 4 + 1], 0, 0]);
}
3 => {
hash = hash ^ pre_mix([buf[i * 4], buf[i * 4 + 1], buf[i * 4 + 2], 0]);
}
_ => { }
}
hash = hash ^ buf.len() as u32;
hash = hash ^ (hash.wrapping_shr(16));
hash = hash.wrapping_mul(0x85ebca6b);
hash = hash ^ (hash.wrapping_shr(13));
hash = hash.wrapping_mul(0xc2b2ae35);
hash = hash ^ (hash.wrapping_shr(16));
hash
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_murmur3_hash() {
assert_eq!(murmur3_32("abort"), murmur3_32("abort"));
assert_ne!(murmur3_32("abort"), murmur3_32("sol_log_"));
}
#[test]
fn test_murmur3_known_values() {
const ABORT_HASH: u32 = murmur3_32("abort");
const SOL_LOG_HASH: u32 = murmur3_32("sol_log_");
assert_eq!(murmur3_32("abort"), ABORT_HASH);
assert_eq!(murmur3_32("sol_log_"), SOL_LOG_HASH);
}
}