all: convert our hash from Lookup3 to MurmurHash3

The hash implementation was taken from the GitHub project below
where it was released into the public domain.  MurmurHash3 should be
faster and less complex than the Lookup3 hash it replaces.

 * https://github.com/aappleby/smhasher

Signed-off-by: Paul Moore <paul@paul-moore.com>

3 files changed, 69 insertions, 663 deletions

diff --git a/src/gen_bpf.c b/src/gen_bpf.c
index 0b6e95a..c919056 100644
--- a/src/gen_bpf.c
+++ b/src/gen_bpf.c
@@ -572,7 +572,7 @@ static int _hsh_add(struct bpf_state *state, struct bpf_blk **blk_p,
 		return -ENOMEM;
 
 	/* generate the hash */
-	h_val = jhash(blk->blks, _BLK_MSZE(blk), 0);
+	h_val = hash(blk->blks, _BLK_MSZE(blk));
 	blk->hash = h_val;
 	blk->flag_hash = true;
 	blk->node = NULL;
diff --git a/src/hash.c b/src/hash.c
index 1228307..4435900 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -1,674 +1,90 @@
 /**
  * Seccomp Library hash code
  *
- * Release under the Public Domain
- * Author: Bob Jenkins <bob_jenkins@burtleburtle.net>
  */
 
 /*
- * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
+ * This code is based on MurmurHash3.cpp from Austin Appleby and is placed in
+ * the public domain.
  *
- * These are functions for producing 32-bit hashes for hash table lookup.
- * jhash_word(), jhash_le(), jhash_be(), mix(), and final() are externally useful
- * functions.  Routines to test the hash are included if SELF_TEST is defined.
- * You can use this free for any purpose.  It's in the public domain.  It has
- * no warranty.
+ * https://github.com/aappleby/smhasher
  *
- * You probably want to use jhash_le().  jhash_le() and jhash_be() hash byte
- * arrays.  jhash_le() is is faster than jhash_be() on little-endian machines.
- * Intel and AMD are little-endian machines.
- *
- * If you want to find a hash of, say, exactly 7 integers, do
- *   a = i1;  b = i2;  c = i3;
- *   mix(a,b,c);
- *   a += i4; b += i5; c += i6;
- *   mix(a,b,c);
- *   a += i7;
- *   final(a,b,c);
- *
- * then use c as the hash value.  If you have a variable length array of
- * 4-byte integers to hash, use jhash_word().  If you have a byte array (like
- * a character string), use jhash_le().  If you have several byte arrays, or
- * a mix of things, see the comments above jhash_le().
- *
- * Why is this so big?  I read 12 bytes at a time into 3 4-byte integers, then
- * mix those integers.  This is fast (you can do a lot more thorough mixing
- * with 12*3 instructions on 3 integers than you can with 3 instructions on 1
- * byte), but shoehorning those bytes into integers efficiently is messy.
  */
 
-#include <stdint.h>
+#include <stdlib.h>
+#include <inttypes.h>
 
-#include "arch.h"
 #include "hash.h"
 
-#define hashsize(n)	((uint32_t)1<<(n))
-#define hashmask(n)	(hashsize(n)-1)
-#define rot(x,k)	(((x)<<(k)) | ((x)>>(32-(k))))
-
-/**
- * Mix 3 32-bit values reversibly
- * @param a 32-bit value
- * @param b 32-bit value
- * @param c 32-bit value
- *
- * This is reversible, so any information in (a,b,c) before mix() is still
- * in (a,b,c) after mix().
- *
- * If four pairs of (a,b,c) inputs are run through mix(), or through mix() in
- * reverse, there are at least 32 bits of the output that are sometimes the
- * same for one pair and different for another pair.
- *
- * This was tested for:
- * - pairs that differed by one bit, by two bits, in any combination of top
- *   bits of (a,b,c), or in any combination of bottom bits of (a,b,c).
- * - "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed the
- *   output delta to a Gray code (a^(a>>1)) so a string of 1's (as is commonly
- *   produced by subtraction) look like a single 1-bit difference.
- * - the base values were pseudorandom, all zero but one bit set, or all zero
- *   plus a counter that starts at zero.
- *
- * Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
- * satisfy this are
- *     4  6  8 16 19  4
- *     9 15  3 18 27 15
- *    14  9  3  7 17  3
- *
- * Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing for "differ"
- * defined as + with a one-bit base and a two-bit delta.  I used
- * http://burtleburtle.net/bob/hash/avalanche.html to choose the operations,
- * constants, and arrangements of the variables.
- *
- * This does not achieve avalanche.  There are input bits of (a,b,c) that fail
- * to affect some output bits of (a,b,c), especially of a.  The most thoroughly
- * mixed value is c, but it doesn't really even achieve avalanche in c.
- *
- * This allows some parallelism.  Read-after-writes are good at doubling the
- * number of bits affected, so the goal of mixing pulls in the opposite
- * direction as the goal of parallelism.  I did what I could.  Rotates seem to
- * cost as much as shifts on every machine I could lay my hands on, and rotates
- * are much kinder to the top and bottom bits, so I used rotates.
- *
- */
-#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; \
-	}
-
-/**
- * Final mixing of 3 32-bit values (a,b,c) into c
- * @param a 32-bit value
- * @param b 32-bit value
- * @param c 32-bit value
- *
- * Pairs of (a,b,c) values differing in only a few bits will usually produce
- * values of c that look totally different.  This was tested for:
- * - pairs that differed by one bit, by two bits, in any combination of top
- *   bits of (a,b,c), or in any combination of bottom bits of (a,b,c).
- * - "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed the
- *   output delta to a Gray code (a^(a>>1)) so a string of 1's (as is commonly
- *   produced by subtraction) look like a single 1-bit difference.
- * - the base values were pseudorandom, all zero but one bit set, or all zero
- *   plus a counter that starts at zero.
- *
- * These constants passed:
- *  14 11 25 16 4 14 24
- *  12 14 25 16 4 14 24
- * and these came close:
- *   4  8 15 26 3 22 24
- *  10  8 15 26 3 22 24
- *  11  8 15 26 3 22 24
- *
- */
-#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); \
-	}
-
-/**
- * Hash an array of 32-bit values
- * @param k the key, an array of uint32_t values
- * @param length the number of array elements
- * @param initval the previous hash, or an arbitrary value
- *
- * This works on all machines.  To be useful, it requires:
- * - that the key be an array of uint32_t's, and
- * - that the length be the number of uint32_t's in the key
- *
- * The function jhash_word() is identical to jhash_le() on little-endian
- * machines, and identical to jhash_be() on big-endian machines, except that
- * the length has to be measured in uint32_ts rather than in bytes.  jhash_le()
- * is more complicated than jhash_word() only because jhash_le() has to dance
- * around fitting the key bytes into registers.
- *
- */
-static uint32_t jhash_word(const uint32_t *k, size_t length, uint32_t initval)
+static inline uint32_t getblock32(const uint32_t *p, int i)
 {
-	uint32_t a, b, c;
-
-	/* set up the internal state */
-	a = b = c = 0xdeadbeef + (((uint32_t)length) << 2) + initval;
-
-	/* handle most of the key */
-	while (length > 3) {
-		a += k[0];
-		b += k[1];
-		c += k[2];
-		mix(a, b, c);
-		length -= 3;
-		k += 3;
-	}
-
-	/* handle the last 3 uint32_t's */
-	switch(length) {
-	case 3 :
-		c += k[2];
-	case 2 :
-		b += k[1];
-	case 1 :
-		a += k[0];
-		final(a, b, c);
-	case 0:
-		/* nothing left to add */
-		break;
-	}
-
-	return c;
+	return p[i];
 }
 
-/**
- * Hash a variable-length key into a 32-bit value
- * @param key the key (the unaligned variable-length array of bytes)
- * @param length the length of the key, counting by bytes
- * @param initval can be any 4-byte value
- *
- * Returns a 32-bit value.  Every bit of the key affects every bit of the
- * return value.  Two keys differing by one or two bits will have totally
- * different hash values.
- *
- * The best hash table sizes are powers of 2.  There is no need to do mod a
- * prime (mod is sooo slow!).  If you need less than 32 bits, use a bitmask.
- * For example, if you need only 10 bits, do:
- *   h = (h & hashmask(10));
- * In which case, the hash table should have hashsize(10) elements.
- *
- * If you are hashing n strings (uint8_t **)k, do it like this:
- *   for (i=0, h=0; i<n; ++i) h = jhash_le( k[i], len[i], h);
- *
- */
-static uint32_t jhash_le(const void *key, size_t length, uint32_t initval)
+static inline uint32_t rotl32(uint32_t x, int8_t r)
 {
-	uint32_t a, b, c;
-	union {
-		const void *ptr;
-		size_t i;
-	} u;     /* needed for Mac Powerbook G4 */
-
-	/* set up the internal state */
-	a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
-
-	u.ptr = key;
-	if ((arch_def_native->endian == ARCH_ENDIAN_LITTLE) &&
-	    ((u.i & 0x3) == 0)) {
-		/* read 32-bit chunks */
-		const uint32_t *k = (const uint32_t *)key;
-
-		while (length > 12) {
-			a += k[0];
-			b += k[1];
-			c += k[2];
-			mix(a, b, c);
-			length -= 12;
-			k += 3;
-		}
-
-		/* "k[2]&0xffffff" actually reads beyond the end of the string,
-		 * but then masks off the part it's not allowed to read.
-		 * Because the string is aligned, the masked-off tail is in the
-		 * same word as the rest of the string.  Every machine with
-		 * memory protection I've seen does it on word boundaries, so
-		 * is OK with this.  But VALGRIND will still catch it and
-		 * complain.  The masking trick does make the hash noticably
-		 * faster for short strings (like English words). */
-#ifndef VALGRIND
-
-		switch(length) {
-		case 12:
-			c += k[2];
-			b += k[1];
-			a += k[0];
-			break;
-		case 11:
-			c += k[2] & 0xffffff;
-			b += k[1];
-			a += k[0];
-			break;
-		case 10:
-			c += k[2] & 0xffff;
-			b += k[1];
-			a += k[0];
-			break;
-		case 9 :
-			c += k[2] & 0xff;
-			b += k[1];
-			a += k[0];
-			break;
-		case 8 :
-			b += k[1];
-			a += k[0];
-			break;
-		case 7 :
-			b += k[1] & 0xffffff;
-			a += k[0];
-			break;
-		case 6 :
-			b += k[1] & 0xffff;
-			a += k[0];
-			break;
-		case 5 :
-			b += k[1] & 0xff;
-			a += k[0];
-			break;
-		case 4 :
-			a += k[0];
-			break;
-		case 3 :
-			a += k[0] & 0xffffff;
-			break;
-		case 2 :
-			a += k[0] & 0xffff;
-			break;
-		case 1 :
-			a += k[0] & 0xff;
-			break;
-		case 0 :
-			/* zero length strings require no mixing */
-			return c;
-		}
-
-#else /* make valgrind happy */
-
-		k8 = (const uint8_t *)k;
-		switch(length) {
-		case 12:
-			c += k[2];
-			b += k[1];
-			a += k[0];
-			break;
-		case 11:
-			c += ((uint32_t)k8[10]) << 16;
-		case 10:
-			c += ((uint32_t)k8[9]) << 8;
-		case 9 :
-			c += k8[8];
-		case 8 :
-			b += k[1];
-			a += k[0];
-			break;
-		case 7 :
-			b += ((uint32_t)k8[6]) << 16;
-		case 6 :
-			b += ((uint32_t)k8[5]) << 8;
-		case 5 :
-			b += k8[4];
-		case 4 :
-			a += k[0];
-			break;
-		case 3 :
-			a += ((uint32_t)k8[2]) << 16;
-		case 2 :
-			a += ((uint32_t)k8[1]) << 8;
-		case 1 :
-			a += k8[0];
-			break;
-		case 0 :
-			return c;
-		}
-
-#endif /* !valgrind */
-
-	} else if ((arch_def_native->endian == ARCH_ENDIAN_LITTLE) &&
-		   ((u.i & 0x1) == 0)) {
-		/* read 16-bit chunks */
-		const uint16_t *k = (const uint16_t *)key;
-		const uint8_t  *k8;
-
-		while (length > 12) {
-			a += k[0] + (((uint32_t)k[1]) << 16);
-			b += k[2] + (((uint32_t)k[3]) << 16);
-			c += k[4] + (((uint32_t)k[5]) << 16);
-			mix(a, b, c);
-			length -= 12;
-			k += 6;
-		}
-
-		k8 = (const uint8_t *)k;
-		switch(length) {
-		case 12:
-			c += k[4] + (((uint32_t)k[5]) << 16);
-			b += k[2] + (((uint32_t)k[3]) << 16);
-			a += k[0] + (((uint32_t)k[1]) << 16);
-			break;
-		case 11:
-			c += ((uint32_t)k8[10]) << 16;
-		case 10:
-			c += k[4];
-			b += k[2] + (((uint32_t)k[3]) << 16);
-			a += k[0] + (((uint32_t)k[1]) << 16);
-			break;
-		case 9 :
-			c += k8[8];
-		case 8 :
-			b += k[2] + (((uint32_t)k[3]) << 16);
-			a += k[0] + (((uint32_t)k[1]) << 16);
-			break;
-		case 7 :
-			b += ((uint32_t)k8[6]) << 16;
-		case 6 :
-			b += k[2];
-			a += k[0] + (((uint32_t)k[1]) << 16);
-			break;
-		case 5 :
-			b += k8[4];
-		case 4 :
-			a += k[0] + (((uint32_t)k[1]) << 16);
-			break;
-		case 3 :
-			a += ((uint32_t)k8[2]) << 16;
-		case 2 :
-			a += k[0];
-			break;
-		case 1 :
-			a += k8[0];
-			break;
-		case 0 :
-			/* zero length requires no mixing */
-			return c;
-		}
-
-	} else {
-		/* need to read the key one byte at a time */
-		const uint8_t *k = (const uint8_t *)key;
-
-		while (length > 12) {
-			a += k[0];
-			a += ((uint32_t)k[1]) << 8;
-			a += ((uint32_t)k[2]) << 16;
-			a += ((uint32_t)k[3]) << 24;
-			b += k[4];
-			b += ((uint32_t)k[5]) << 8;
-			b += ((uint32_t)k[6]) << 16;
-			b += ((uint32_t)k[7]) << 24;
-			c += k[8];
-			c += ((uint32_t)k[9]) << 8;
-			c += ((uint32_t)k[10]) << 16;
-			c += ((uint32_t)k[11]) << 24;
-			mix(a, b, c);
-			length -= 12;
-			k += 12;
-		}
-
-		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;
+	return (x << r) | (x >> (32 - r));
 }
 
-/**
- * Hash a variable-length key into a 32-bit value
- * @param key the key (the unaligned variable-length array of bytes)
- * @param length the length of the key, counting by bytes
- * @param initval can be any 4-byte value
- *
- * This is the same as jhash_word() on big-endian machines.  It is different
- * from jhash_le() on all machines.  jhash_be() takes advantage of big-endian
- * byte ordering.
- *
- */
-static uint32_t jhash_be( const void *key, size_t length, uint32_t initval)
+static inline uint32_t fmix32(uint32_t h)
 {
-	uint32_t a, b, c;
-	union {
-		const void *ptr;
-		size_t i;
-	} u; /* to cast key to (size_t) happily */
-
-	/* set up the internal state */
-	a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
-
-	u.ptr = key;
-	if ((arch_def_native->endian == ARCH_ENDIAN_BIG) &&
-	    ((u.i & 0x3) == 0)) {
-		/* read 32-bit chunks */
-		const uint32_t *k = (const uint32_t *)key;
-
-		while (length > 12) {
-			a += k[0];
-			b += k[1];
-			c += k[2];
-			mix(a, b, c);
-			length -= 12;
-			k += 3;
-		}
-
-		/* "k[2]<<8" actually reads beyond the end of the string, but
-		 * then shifts out the part it's not allowed to read.  Because
-		 * the string is aligned, the illegal read is in the same word
-		 * as the rest of the string.  Every machine with memory
-		 * protection I've seen does it on word boundaries, so is OK
-		 * with this.  But VALGRIND will still catch it and complain.
-		 * The masking trick does make the hash noticably faster for
-		 * short strings (like English words). */
-#ifndef VALGRIND
-
-		switch(length) {
-		case 12:
-			c += k[2];
-			b += k[1];
-			a += k[0];
-			break;
-		case 11:
-			c += k[2] & 0xffffff00;
-			b += k[1];
-			a += k[0];
-			break;
-		case 10:
-			c += k[2] & 0xffff0000;
-			b += k[1];
-			a += k[0];
-			break;
-		case 9 :
-			c += k[2] & 0xff000000;
-			b += k[1];
-			a += k[0];
-			break;
-		case 8 :
-			b += k[1];
-			a += k[0];
-			break;
-		case 7 :
-			b += k[1] & 0xffffff00;
-			a += k[0];
-			break;
-		case 6 :
-			b += k[1] & 0xffff0000;
-			a += k[0];
-			break;
-		case 5 :
-			b += k[1] & 0xff000000;
-			a += k[0];
-			break;
-		case 4 :
-			a += k[0];
-			break;
-		case 3 :
-			a += k[0] & 0xffffff00;
-			break;
-		case 2 :
-			a += k[0] & 0xffff0000;
-			break;
-		case 1 :
-			a += k[0] & 0xff000000;
-			break;
-		case 0 :
-			/* zero length strings require no mixing */
-			return c;
-		}
-
-#else  /* make valgrind happy */
-
-		k8 = (const uint8_t *)k;
-		switch(length) {
-		case 12:
-			c += k[2];
-			b += k[1];
-			a += k[0];
-			break;
-		case 11:
-			c += ((uint32_t)k8[10]) << 8;
-		case 10:
-			c += ((uint32_t)k8[9]) << 16;
-		case 9 :
-			c += ((uint32_t)k8[8]) << 24;
-		case 8 :
-			b += k[1];
-			a += k[0];
-			break;
-		case 7 :
-			b += ((uint32_t)k8[6]) << 8;
-		case 6 :
-			b += ((uint32_t)k8[5]) << 16;
-		case 5 :
-			b += ((uint32_t)k8[4]) << 24;
-		case 4 :
-			a += k[0];
-			break;
-		case 3 :
-			a += ((uint32_t)k8[2]) << 8;
-		case 2 :
-			a += ((uint32_t)k8[1]) << 16;
-		case 1 :
-			a += ((uint32_t)k8[0]) << 24;
-			break;
-		case 0 :
-			return c;
-		}
-
-#endif /* !VALGRIND */
-
-	} else {
-		/* need to read the key one byte at a time */
-		const uint8_t *k = (const uint8_t *)key;
+	h ^= h >> 16;
+	h *= 0x85ebca6b;
+	h ^= h >> 13;
+	h *= 0xc2b2ae35;
+	h ^= h >> 16;
 
-		while (length > 12) {
-			a += ((uint32_t)k[0]) << 24;
-			a += ((uint32_t)k[1]) << 16;
-			a += ((uint32_t)k[2]) << 8;
-			a += ((uint32_t)k[3]);
-			b += ((uint32_t)k[4]) << 24;
-			b += ((uint32_t)k[5]) << 16;
-			b += ((uint32_t)k[6]) << 8;
-			b += ((uint32_t)k[7]);
-			c += ((uint32_t)k[8]) << 24;
-			c += ((uint32_t)k[9]) << 16;
-			c += ((uint32_t)k[10]) << 8;
-			c += ((uint32_t)k[11]);
-			mix(a, b, c);
-			length -= 12;
-			k += 12;
-		}
-
-		switch(length) {
-		case 12:
-			c += k[11];
-		case 11:
-			c += ((uint32_t)k[10]) << 8;
-		case 10:
-			c += ((uint32_t)k[9]) << 16;
-		case 9 :
-			c += ((uint32_t)k[8]) << 24;
-		case 8 :
-			b += k[7];
-		case 7 :
-			b += ((uint32_t)k[6]) << 8;
-		case 6 :
-			b += ((uint32_t)k[5]) << 16;
-		case 5 :
-			b += ((uint32_t)k[4]) << 24;
-		case 4 :
-			a += k[3];
-		case 3 :
-			a += ((uint32_t)k[2]) << 8;
-		case 2 :
-			a += ((uint32_t)k[1]) << 16;
-		case 1 :
-			a += ((uint32_t)k[0]) << 24;
-			break;
-		case 0 :
-			return c;
-		}
-	}
-
-	final(a, b, c);
-	return c;
+	return h;
 }
 
-/**
- * Hash a variable-length key into a 32-bit value
- * @param key the key (the unaligned variable-length array of bytes)
- * @param length the length of the key, counting by bytes
- * @param initval can be any 4-byte value
- *
- * A small wrapper function that selects the proper hash function based on the
- * native machine's byte-ordering.
- *
- */
-uint32_t jhash(const void *key, size_t length, uint32_t initval)
+/* NOTE: this is an implementation of MurmurHash3_x86_32 */
+uint32_t hash(const void *key, size_t length)
 {
-	if (length % sizeof(uint32_t) == 0)
-		return jhash_word(key, (length / sizeof(uint32_t)), initval);
-	else if (arch_def_native->endian == ARCH_ENDIAN_BIG)
-		return jhash_be(key, length, initval);
-	else
-		return jhash_le(key, length, initval);
+	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;
 }
diff --git a/src/hash.h b/src/hash.h
index efd252f..357131d 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -1,18 +1,8 @@
 /**
- * The "lookup3.c" Hash Implementation from Bob Jenkins
+ * Seccomp Library hash code
  *
- * Original Author: Bob Jenkins <bob_jenkins@burtleburtle.net>
- * Source: http://burtleburtle.net/bob/c/lookup3.c
- */
-
-/*
- * Original License:
+ * See hash.c for information on the implementation.
  *
- * These are functions for producing 32-bit hashes for hash table lookup.
- * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
- * are externally useful functions.  Routines to test the hash are included
- * if SELF_TEST is defined.  You can use this free for any purpose.  It's in
- * the public domain.  It has no warranty.
  */
 
 #ifndef _HASH_H
@@ -20,7 +10,7 @@
 
 #include <inttypes.h>
 
-uint32_t jhash(const void *key, size_t length, uint32_t initval);
+uint32_t hash(const void *key, size_t length);
 
 #endif