From e0ea973df46c808417b5a6beb40e9e2e886b5182 Mon Sep 17 00:00:00 2001
From: Imbus <>
Date: Mon, 18 Aug 2025 11:19:37 +0200
Subject: [PATCH] Lookup3

---
 lookup3.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 lookup3.c

diff --git a/lookup3.c b/lookup3.c
new file mode 100644
index 0000000..959d7a6
--- /dev/null
+++ b/lookup3.c
@@ -0,0 +1,63 @@
+#include <stdint.h>
+#include <stdlib.h>
+
+#define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
+
+// clang-format off
+#define mix(a,b,c) \
+{ \
+  a -= c;  a ^= rot(c, 4);  c += b; \
+  b -= a;  b ^= rot(a, 6);  a += c; \
+  c -= b;  c ^= rot(b, 8);  b += a; \
+  a -= c;  a ^= rot(c,16);  c += b; \
+  b -= a;  b ^= rot(a,19);  a += c; \
+  c -= b;  c ^= rot(b, 4);  b += a; \
+}
+
+#define final(a,b,c) \
+{ \
+  c ^= b; c -= rot(b,14); \
+  a ^= c; a -= rot(c,11); \
+  b ^= a; b -= rot(a,25); \
+  c ^= b; c -= rot(b,16); \
+  a ^= c; a -= rot(c,4);  \
+  b ^= a; b -= rot(a,14); \
+  c ^= b; c -= rot(b,24); \
+}
+// clang-format on
+
+uint32_t lookup3(const void *key, size_t length, uint32_t initval) {
+    uint32_t        a, b, c;
+    const uint8_t  *k;
+    const uint32_t *data32Bit;
+
+    data32Bit = key;
+    a = b = c = 0xdeadbeef + (((uint32_t)length) << 2) + initval;
+
+    while (length > 12) {
+        a += *(data32Bit++);
+        b += *(data32Bit++);
+        c += *(data32Bit++);
+        mix(a, b, c);
+        length -= 12;
+    }
+
+    k = (const uint8_t *)data32Bit;
+    switch (length) {
+    case 12: c += ((uint32_t)k[11]) << 24;
+    case 11: c += ((uint32_t)k[10]) << 16;
+    case 10: c += ((uint32_t)k[9]) << 8;
+    case 9: c += k[8];
+    case 8: b += ((uint32_t)k[7]) << 24;
+    case 7: b += ((uint32_t)k[6]) << 16;
+    case 6: b += ((uint32_t)k[5]) << 8;
+    case 5: b += k[4];
+    case 4: a += ((uint32_t)k[3]) << 24;
+    case 3: a += ((uint32_t)k[2]) << 16;
+    case 2: a += ((uint32_t)k[1]) << 8;
+    case 1: a += k[0]; break;
+    case 0: return c;
+    }
+    final(a, b, c);
+    return c;
+}