+++ /dev/null
-/**
- * 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.
- *
- * 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.
- *
- * 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 "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)
-{
- 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;
-}
-
-/**
- * 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)
-{
- 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;
-}
-
-/**
- * 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)
-{
- 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;
-
- 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;
-}
-
-/**
- * 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)
-{
- 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);
-}
projects / linux-seccomp.git / blobdiff