feat: Implement xxHash32 and use it in stdlib (#1580)

Author: MaxGraey

std/assembly/util/hash.ts

@@ -1,5 +1,3 @@
-// @ts-ignore: decorator
-@inline
 export function HASH<T>(key: T): u32 {
   if (isString<T>()) {
     return hashStr(changetype<string>(key));
@@ -10,63 +8,110 @@ export function HASH<T>(key: T): u32 {
     if (sizeof<T>() == 4) return hash32(reinterpret<u32>(f32(key)));
     if (sizeof<T>() == 8) return hash64(reinterpret<u64>(f64(key)));
   } else {
-    if (sizeof<T>() == 1) return hash8 (u32(key));
-    if (sizeof<T>() == 2) return hash16(u32(key));
-    if (sizeof<T>() == 4) return hash32(u32(key));
+    if (sizeof<T>() <= 4) return hash32(u32(key), sizeof<T>());
     if (sizeof<T>() == 8) return hash64(u64(key));
   }
   return unreachable();
 }
 
-// FNV-1a 32-bit as a starting point, see: http://isthe.com/chongo/tech/comp/fnv/
+// XXHash 32-bit as a starting point, see: https://cyan4973.github.io/xxHash
 
+// primes
 // @ts-ignore: decorator
-@inline const FNV_OFFSET: u32 = 2166136261;
-
+@inline const XXH32_P1: u32 = 2654435761;
 // @ts-ignore: decorator
-@inline const FNV_PRIME: u32 = 16777619;
-
-function hash8(key: u32): u32 {
-  return (FNV_OFFSET ^ key) * FNV_PRIME;
-}
+@inline const XXH32_P2: u32 = 2246822519;
+// @ts-ignore: decorator
+@inline const XXH32_P3: u32 = 3266489917;
+// @ts-ignore: decorator
+@inline const XXH32_P4: u32 = 668265263;
+// @ts-ignore: decorator
+@inline const XXH32_P5: u32 = 374761393;
+// @ts-ignore: decorator
+@inline const XXH32_SEED: u32 = 0;
 
-function hash16(key: u32): u32 {
-  var v = FNV_OFFSET;
-  v = (v ^ ( key        & 0xff)) * FNV_PRIME;
-  v = (v ^ ( key >>  8        )) * FNV_PRIME;
-  return v;
+// @ts-ignore: decorator
+@inline
+function hash32(key: u32, len: u32 = 4): u32 {
+  var h: u32 = XXH32_SEED + XXH32_P5 + len;
+  h += key * XXH32_P3;
+  h  = rotl(h, 17) * XXH32_P4;
+  h ^= h >> 15;
+  h *= XXH32_P2;
+  h ^= h >> 13;
+  h *= XXH32_P3;
+  h ^= h >> 16;
+  return h;
 }
 
-function hash32(key: u32): u32 {
-  var v = FNV_OFFSET;
-  v = (v ^ ( key        & 0xff)) * FNV_PRIME;
-  v = (v ^ ((key >>  8) & 0xff)) * FNV_PRIME;
-  v = (v ^ ((key >> 16) & 0xff)) * FNV_PRIME;
-  v = (v ^ ( key >> 24        )) * FNV_PRIME;
-  return v;
+// @ts-ignore: decorator
+@inline
+function hash64(key: u64): u32 {
+  var h: u32 = XXH32_SEED + XXH32_P5 + 8;
+  h += <u32>key * XXH32_P3;
+  h  = rotl(h, 17) * XXH32_P4;
+  h += <u32>(key >> 32) * XXH32_P3;
+  h  = rotl(h, 17) * XXH32_P4;
+  h ^= h >> 15;
+  h *= XXH32_P2;
+  h ^= h >> 13;
+  h *= XXH32_P3;
+  h ^= h >> 16;
+  return h;
 }
 
-function hash64(key: u64): u32 {
-  var l = <u32> key;
-  var h = <u32>(key >>> 32);
-  var v = FNV_OFFSET;
-  v = (v ^ ( l        & 0xff)) * FNV_PRIME;
-  v = (v ^ ((l >>  8) & 0xff)) * FNV_PRIME;
-  v = (v ^ ((l >> 16) & 0xff)) * FNV_PRIME;
-  v = (v ^ ( l >> 24        )) * FNV_PRIME;
-  v = (v ^ ( h        & 0xff)) * FNV_PRIME;
-  v = (v ^ ((h >>  8) & 0xff)) * FNV_PRIME;
-  v = (v ^ ((h >> 16) & 0xff)) * FNV_PRIME;
-  v = (v ^ ( h >> 24        )) * FNV_PRIME;
-  return v;
+// @ts-ignore: decorator
+@inline
+function mix(h: u32, key: u32): u32 {
+  return rotl(h + key * XXH32_P2, 13) * XXH32_P1;
 }
 
+// @ts-ignore: decorator
+@inline
 function hashStr(key: string): u32 {
-  var v = FNV_OFFSET;
-  if (key !== null) {
-    for (let i: usize = 0, k: usize = key.length << 1; i < k; ++i) {
-      v = (v ^ <u32>load<u8>(changetype<usize>(key) + i)) * FNV_PRIME;
+  if (key === null) return XXH32_SEED;
+
+  var h: u32 = key.length << 1;
+  var len: usize = h;
+  var pos = changetype<usize>(key);
+
+  if (len >= 16) {
+    let s1 = XXH32_SEED + XXH32_P1 + XXH32_P2;
+    let s2 = XXH32_SEED + XXH32_P2;
+    let s3 = XXH32_SEED;
+    let s4 = XXH32_SEED - XXH32_P1;
+
+    let end = len + pos - 16;
+    while (pos <= end) {
+      s1 = mix(s1, load<u32>(pos    ));
+      s2 = mix(s2, load<u32>(pos,  4));
+      s3 = mix(s3, load<u32>(pos,  8));
+      s4 = mix(s4, load<u32>(pos, 12));
+      pos += 16;
     }
+    h += rotl(s1, 1) + rotl(s2, 7) + rotl(s3, 12) + rotl(s4, 18);
+  } else {
+    h += XXH32_SEED + XXH32_P5;
+  }
+
+  var end = changetype<usize>(key) + len - 4;
+  while (pos <= end) {
+    h += load<u32>(pos) * XXH32_P3;
+    h = rotl(h, 17) * XXH32_P4;
+    pos += 4;
   }
-  return v;
+
+  end = changetype<usize>(key) + len;
+  while (pos < end) {
+    h += <u32>load<u8>(pos) * XXH32_P5;
+    h = rotl(h, 11) * XXH32_P1;
+    pos++;
+  }
+
+  h ^= h >> 15;
+  h *= XXH32_P2;
+  h ^= h >> 13;
+  h *= XXH32_P3;
+  h ^= h >> 16;
+  return h;
 }