From 49d616dc9fe8469839c65157a3ffa3e662568d42 Mon Sep 17 00:00:00 2001
From: Imbus <>
Date: Sat, 27 Dec 2025 07:05:43 +0100
Subject: [PATCH] fnv1a

---
 fnv1a.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 fnv1a.c

diff --git a/fnv1a.c b/fnv1a.c
new file mode 100644
index 0000000..8156a91
--- /dev/null
+++ b/fnv1a.c
@@ -0,0 +1,49 @@
+/*
+ * Check wikipedia for details and pseudocode.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#define FNV1A64_BASIS 0XCBF29CE484222325
+#define FNV1A64_PRIME 0X00000100000001B3
+
+uint64_t fnv1a64(const char *data, size_t len) {
+    uint64_t hash = FNV1A64_BASIS;
+
+    for (size_t i = 0; i < len; i++) {
+        hash = (hash ^ (uint64_t)data[i]) * FNV1A64_PRIME;
+    }
+
+    return hash;
+}
+
+#define FNV1A32_BASIS 0x811c9dc5
+#define FNV1A32_PRIME 0x01000193
+
+uint32_t fnv1a32(const char *data, size_t len) {
+    uint32_t hash = FNV1A32_BASIS;
+
+    for (size_t i = 0; i < len; i++) {
+        hash = (hash ^ (uint32_t)data[i]) * FNV1A32_PRIME;
+    }
+
+    return hash;
+}
+
+int main(void) {
+    char    *str = "hello\0";
+    uint64_t h64 = fnv1a64(str, strnlen(str, 128));
+    uint32_t h32 = fnv1a32(str, strnlen(str, 128));
+
+    char    *str_2 = "Hello\0";
+    uint64_t h64_2 = fnv1a64(str_2, strnlen(str, 128));
+    uint32_t h32_2 = fnv1a32(str_2, strnlen(str, 128));
+
+    printf("FNV1a64 of \"hello\": %lX\n", h64);
+    printf("FNV1a32 of \"hello\": %X\n", h32);
+
+    printf("FNV1a64 of \"Hello\": %lX\n", h64_2);
+    printf("FNV1a32 of \"Hello\": %X\n", h32_2);
+}