1 files changed, 61 insertions, 0 deletions
diff --git a/hmap/hash.h b/hmap/hash.h
new file mode 100644
index 0000000..9d4d8dd
--- /dev/null
+++ b/hmap/hash.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: MIT */
+/**
+ * hash.h - implementations of the FNV1a hashing algorithm.
+ *
+ * Copyright (c) 2022-2023 - Yaroslav de la Peña Smirnov
+ */
+#ifndef HMAP_HASH_H
+#define HMAP_HASH_H
+
+#include <inttypes.h>
+#include <stdlib.h>
+
+#if SIZE_MAX == 0xFFFFFFFF
+/* size_t is 32bit */
+static const size_t fnv_prime	= 16777619u;
+static const size_t fnv_offsetb = 2166136261u;
+#elif SIZE_MAX == 0xFFFFFFFFFFFFFFFF
+/* size_t is 64bit */
+static const size_t fnv_prime	= 1099511628211u;
+static const size_t fnv_offsetb = 14695981039346656037u;
+#endif
+
+/**
+ * fnv1a_bytes_hash() - generic fnv1a hash function.
+ * @data:	pointer to data to hash.
+ * @len:	size of @data in bytes.
+ *
+ * Return:	hash value.
+ */
+static inline size_t fnv1a_bytes_hash(const void *data, size_t len)
+{
+	const char *bytes = (const char *)data;
+	size_t		hash  = fnv_offsetb;
+
+	for (size_t i = 0; i < len; i++) {
+		hash ^= bytes[i];
+		hash *= fnv_prime;
+	}
+
+	return hash;
+}
+
+/**
+ * fnv1a_str_hash() - fnv1a hash function for nul-terminated strings.
+ * @str:	nul-terminated string of characters to hash.
+ *
+ * Return:	hash value.
+ */
+static inline size_t fnv1a_str_hash(const char *str)
+{
+	size_t hash = fnv_offsetb;
+
+	for (size_t i = 0; str[i]; i++) {
+		hash ^= str[i];
+		hash *= fnv_prime;
+	}
+
+	return hash;
+}
+
+#endif /* HMAP_HASH_H */