1 files changed, 90 insertions, 0 deletions
diff --git a/src/hash.c b/src/hash.c
new file mode 100644
index 0000000..4435900
--- /dev/null
+++ b/src/hash.c
@@ -0,0 +1,90 @@
+/**
+ * Seccomp Library hash code
+ *
+ */
+
+/*
+ * This code is based on MurmurHash3.cpp from Austin Appleby and is placed in
+ * the public domain.
+ *
+ * https://github.com/aappleby/smhasher
+ *
+ */
+
+#include <stdlib.h>
+#include <inttypes.h>
+
+#include "hash.h"
+
+static inline uint32_t getblock32(const uint32_t *p, int i)
+{
+	return p[i];
+}
+
+static inline uint32_t rotl32(uint32_t x, int8_t r)
+{
+	return (x << r) | (x >> (32 - r));
+}
+
+static inline uint32_t fmix32(uint32_t h)
+{
+	h ^= h >> 16;
+	h *= 0x85ebca6b;
+	h ^= h >> 13;
+	h *= 0xc2b2ae35;
+	h ^= h >> 16;
+
+	return h;
+}
+
+/* NOTE: this is an implementation of MurmurHash3_x86_32 */
+uint32_t hash(const void *key, size_t length)
+{
+	const uint8_t *data = (const uint8_t *)key;
+	const uint32_t *blocks;
+	const uint8_t *tail;
+	const int nblocks = length / 4;
+	const uint32_t c1 = 0xcc9e2d51;
+	const uint32_t c2 = 0x1b873593;
+	uint32_t k1;
+	uint32_t k2 = 0;
+	int i;
+
+	/* NOTE: we always force a seed of 0 */
+	uint32_t h1 = 0;
+
+	/* body */
+	blocks = (const uint32_t *)(data + nblocks * 4);
+	for(i = -nblocks; i; i++) {
+		k1 = getblock32(blocks, i);
+
+		k1 *= c1;
+		k1 = rotl32(k1, 15);
+		k1 *= c2;
+
+		h1 ^= k1;
+		h1 = rotl32(h1, 13);
+		h1 = h1 * 5 + 0xe6546b64;
+	}
+
+	/* tail */
+	tail = (const uint8_t *)(data + nblocks * 4);
+	switch(length & 3) {
+	case 3:
+		k2 ^= tail[2] << 16;
+	case 2:
+		k2 ^= tail[1] << 8;
+	case 1:
+		k2 ^= tail[0];
+		k2 *= c1;
+		k2 = rotl32(k2, 15);
+		k2 *= c2;
+		h1 ^= k2;
+	};
+
+	/* finalization */
+	h1 ^= length;
+	h1 = fmix32(h1);
+
+	return h1;
+}