+++ /dev/null
-/*
- * Copyright (c) 2008 Apple Inc. All rights reserved.
- *
- * @APPLE_LICENSE_HEADER_START@
- *
- * This file contains Original Code and/or Modifications of Original Code
- * as defined in and that are subject to the Apple Public Source License
- * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
- *
- * The Original Code and all software distributed under the License are
- * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- * Please see the License for the specific language governing rights and
- * limitations under the License.
- *
- * @APPLE_LICENSE_HEADER_END@
- */
-
-/*
-Portions derived from:
-
---------------------------------------------------------------------
-lookup8.c, by Bob Jenkins, January 4 1997, Public Domain.
-hash(), hash2(), hash3, and mix() 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 has no warranty.
---------------------------------------------------------------------
-
-------------------------------------------------------------------------------
-perfect.c: code to generate code for a hash for perfect hashing.
-(c) Bob Jenkins, September 1996, December 1999
-You may use this code in any way you wish, and it is free. No warranty.
-I hereby place this in the public domain.
-Source is http://burtleburtle.net/bob/c/perfect.c
-------------------------------------------------------------------------------
-*/
-
-/*
- * objc-selopt.h
- * Interface between libobjc and dyld
- * for selector uniquing in the dyld shared cache.
- *
- * When building the shared cache, dyld locates all selectors and selector
- * references in the cached images. It builds a perfect hash table out of
- * them and writes the table into the shared cache copy of libobjc.
- * libobjc then uses that table as the builtin selector list.
- *
- * Versioning
- * The table has a version number. dyld and objc can both ignore the table
- * if the other used the wrong version number.
- *
- * Completeness
- * Not all libraries are in the shared cache. Libraries that are in the
- * shared cache and were optimized are specially marked. Libraries on
- * disk never include those marks.
- *
- * Coherency
- * Libraries optimized in the shared cache can be replaced by unoptimized
- * copies from disk when loaded. The copy from disk is not marked and will
- * be fixed up by libobjc. The shared cache copy is still mapped into the
- * process, so the table can point to cstring data in that library's part
- * of the shared cache without trouble.
- *
- * Atomicity
- * dyld writes the table itself last. If dyld marks some metadata as
- * updated but then fails to write a table for some reason, libobjc
- * fixes up all metadata as if it were not marked.
- */
-
-#ifndef _OBJC_SELOPT_H
-#define _OBJC_SELOPT_H
-
-/*
- DO NOT INCLUDE ANY objc HEADERS HERE
- dyld USES THIS FILE AND CANNOT SEE THEM
-*/
-#include <stdint.h>
-#include <stdlib.h>
-#include <ext/hash_map>
-/*
- DO NOT INCLUDE ANY objc HEADERS HERE
- dyld USES THIS FILE AND CANNOT SEE THEM
-*/
-
-#ifndef STATIC_ASSERT
-# define STATIC_ASSERT(x) _STATIC_ASSERT2(x, __LINE__)
-# define _STATIC_ASSERT2(x, line) _STATIC_ASSERT3(x, line)
-# define _STATIC_ASSERT3(x, line) \
- typedef struct { \
- int _static_assert[(x) ? 0 : -1]; \
- } _static_assert_ ## line __attribute__((unavailable))
-#endif
-
-#define SELOPT_DEBUG 0
-
-namespace objc_opt {
-
- typedef int32_t objc_selopt_offset_t;
- typedef uint8_t objc_selopt_check_t;
-
-#ifdef SELOPT_WRITE
-
-// Perfect hash code is at the end of this file.
-
-struct perfect_hash {
- uint32_t capacity;
- uint32_t occupied;
- uint32_t shift;
- uint32_t mask;
- uint64_t salt;
-
- uint32_t scramble[256];
- uint8_t *tab; // count == mask+1; free with delete[]
-
- perfect_hash() : tab(0) { }
-
- ~perfect_hash() { if (tab) delete[] tab; }
-};
-
-struct eqstr {
- bool operator()(const char* s1, const char* s2) const {
- return strcmp(s1, s2) == 0;
- }
-};
-
-typedef __gnu_cxx::hash_map<const char *, uint64_t, __gnu_cxx::hash<const char *>, eqstr> string_map;
-
-static perfect_hash make_perfect(const string_map& strings);
-
-#endif
-
-static uint64_t lookup8( uint8_t *k, size_t length, uint64_t level);
-
-// Edit objc-sel-table.s and OPT_INITIALIZER if you change this structure.
-struct objc_selopt_t {
- uint32_t capacity;
- uint32_t occupied;
- uint32_t shift;
- uint32_t mask;
- uint32_t zero;
- uint32_t unused; // alignment pad
- uint64_t salt;
-
- uint32_t scramble[256];
- uint8_t tab[0]; /* tab[mask+1] (always power-of-2) */
- // int32_t offsets[capacity]; /* offsets from &capacity to cstrings */
- // uint8_t checkbytes[capacity]; /* check byte for each selector string */
-
- objc_selopt_offset_t *offsets() { return (objc_selopt_offset_t *)&tab[mask+1]; }
- const objc_selopt_offset_t *offsets() const { return (const objc_selopt_offset_t *)&tab[mask+1]; }
-
- objc_selopt_check_t *checkbytes() { return (objc_selopt_check_t *)&offsets()[capacity]; }
- const objc_selopt_check_t *checkbytes() const { return (const objc_selopt_check_t *)&offsets()[capacity]; }
-
- uint32_t hash(const char *key) const
- {
- uint64_t val = lookup8((uint8_t*)key, strlen(key), salt);
- uint32_t index = (uint32_t)(val>>shift) ^ scramble[tab[val&mask]];
- return index;
- }
-
- // The check bytes areused to reject strings that aren't in the table
- // without paging in the table's cstring data. This checkbyte calculation
- // catches 4785/4815 rejects when launching Safari; a perfect checkbyte
- // would catch 4796/4815.
- objc_selopt_check_t checkbyte(const char *key) const
- {
- return
- ((key[0] & 0x7) << 5)
- |
- (strlen(key) & 0x1f);
- }
-
- const char *get(const char *key) const
- {
- uint32_t h = hash(key);
-
- // Use check byte to reject without paging in the table's cstrings
- objc_selopt_check_t h_check = checkbytes()[h];
- objc_selopt_check_t key_check = checkbyte(key);
- bool check_fail = (h_check != key_check);
-#if ! SELOPT_DEBUG
- if (check_fail) return NULL;
-#endif
-
- const char *result = (const char *)this + offsets()[h];
- if (0 != strcmp(key, result)) return NULL;
-
-#if SELOPT_DEBUG
- if (check_fail) abort();
-#endif
-
- return result;
- }
-
-#ifdef SELOPT_WRITE
- void set(const char *key, objc_selopt_offset_t value)
- {
- uint32_t h = hash(key);
- offsets()[h] = value;
- checkbytes()[h] = checkbyte(key);
- }
-#endif
-};
-
-
-// Edit objc-sel-table.s if you change this value.
-enum { VERSION = 10 };
-
-// Edit objc-sel-table.s and OPT_INITIALIZER if you change this structure.
-struct objc_opt_t {
- uint32_t version;
- uint32_t selopt_offset;
-
- const objc_selopt_t* selopt() const {
- if (selopt_offset == 0) return NULL;
- return (objc_selopt_t *)((uint8_t *)this + selopt_offset);
- }
- objc_selopt_t* selopt() {
- if (selopt_offset == 0) return NULL;
- return (objc_selopt_t *)((uint8_t *)this + selopt_offset);
- }
-};
-
-// sizeof(objc_opt_t) must be pointer-aligned
-STATIC_ASSERT(sizeof(objc_opt_t) % sizeof(void*) == 0);
-
-// Initializer for empty opt of type uint32_t[].
-#define X8(x) x, x, x, x, x, x, x, x
-#define X64(x) X8(x), X8(x), X8(x), X8(x), X8(x), X8(x), X8(x), X8(x)
-#define X256(x) X64(x), X64(x), X64(x), X64(x)
-#define OPT_INITIALIZER { \
- /* objc_opt_t */ \
- objc_opt::VERSION, 8, \
- /* objc_selopt_t */ \
- 4, 4, 63, 3, 0, 0, 0,0, X256(0), 0, 16, 16, 16, 16, 0 \
-}
-
-
-/*
---------------------------------------------------------------------
-mix -- mix 3 64-bit values reversibly.
-mix() takes 48 machine instructions, but only 24 cycles on a superscalar
- machine (like Intel's new MMX architecture). It requires 4 64-bit
- registers for 4::2 parallelism.
-All 1-bit deltas, all 2-bit deltas, all deltas composed of top bits of
- (a,b,c), and all deltas of bottom bits were tested. All deltas were
- tested both on random keys and on keys that were nearly all zero.
- These deltas all cause every bit of c to change between 1/3 and 2/3
- of the time (well, only 113/400 to 287/400 of the time for some
- 2-bit delta). These deltas all cause at least 80 bits to change
- among (a,b,c) when the mix is run either forward or backward (yes it
- is reversible).
-This implies that a hash using mix64 has no funnels. There may be
- characteristics with 3-bit deltas or bigger, I didn't test for
- those.
---------------------------------------------------------------------
-*/
-#define mix64(a,b,c) \
-{ \
- a -= b; a -= c; a ^= (c>>43); \
- b -= c; b -= a; b ^= (a<<9); \
- c -= a; c -= b; c ^= (b>>8); \
- a -= b; a -= c; a ^= (c>>38); \
- b -= c; b -= a; b ^= (a<<23); \
- c -= a; c -= b; c ^= (b>>5); \
- a -= b; a -= c; a ^= (c>>35); \
- b -= c; b -= a; b ^= (a<<49); \
- c -= a; c -= b; c ^= (b>>11); \
- a -= b; a -= c; a ^= (c>>12); \
- b -= c; b -= a; b ^= (a<<18); \
- c -= a; c -= b; c ^= (b>>22); \
-}
-
-/*
---------------------------------------------------------------------
-hash() -- hash a variable-length key into a 64-bit value
- k : the key (the unaligned variable-length array of bytes)
- len : the length of the key, counting by bytes
- level : can be any 8-byte value
-Returns a 64-bit value. Every bit of the key affects every bit of
-the return value. No funnels. Every 1-bit and 2-bit delta achieves
-avalanche. About 41+5len instructions.
-
-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 64 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 = hash( k[i], len[i], h);
-
-By Bob Jenkins, Jan 4 1997. bob_jenkins@burtleburtle.net. You may
-use this code any way you wish, private, educational, or commercial,
-but I would appreciate if you give me credit.
-
-See http://burtleburtle.net/bob/hash/evahash.html
-Use for hash table lookup, or anything where one collision in 2^^64
-is acceptable. Do NOT use for cryptographic purposes.
---------------------------------------------------------------------
-*/
-
-static uint64_t lookup8( uint8_t *k, size_t length, uint64_t level)
-// uint8_t *k; /* the key */
-// uint64_t length; /* the length of the key */
-// uint64_t level; /* the previous hash, or an arbitrary value */
-{
- uint64_t a,b,c;
- size_t len;
-
- /* Set up the internal state */
- len = length;
- a = b = level; /* the previous hash value */
- c = 0x9e3779b97f4a7c13LL; /* the golden ratio; an arbitrary value */
-
- /*---------------------------------------- handle most of the key */
- while (len >= 24)
- {
- a += (k[0] +((uint64_t)k[ 1]<< 8)+((uint64_t)k[ 2]<<16)+((uint64_t)k[ 3]<<24)
- +((uint64_t)k[4 ]<<32)+((uint64_t)k[ 5]<<40)+((uint64_t)k[ 6]<<48)+((uint64_t)k[ 7]<<56));
- b += (k[8] +((uint64_t)k[ 9]<< 8)+((uint64_t)k[10]<<16)+((uint64_t)k[11]<<24)
- +((uint64_t)k[12]<<32)+((uint64_t)k[13]<<40)+((uint64_t)k[14]<<48)+((uint64_t)k[15]<<56));
- c += (k[16] +((uint64_t)k[17]<< 8)+((uint64_t)k[18]<<16)+((uint64_t)k[19]<<24)
- +((uint64_t)k[20]<<32)+((uint64_t)k[21]<<40)+((uint64_t)k[22]<<48)+((uint64_t)k[23]<<56));
- mix64(a,b,c);
- k += 24; len -= 24;
- }
-
- /*------------------------------------- handle the last 23 bytes */
- c += length;
- switch(len) /* all the case statements fall through */
- {
- case 23: c+=((uint64_t)k[22]<<56);
- case 22: c+=((uint64_t)k[21]<<48);
- case 21: c+=((uint64_t)k[20]<<40);
- case 20: c+=((uint64_t)k[19]<<32);
- case 19: c+=((uint64_t)k[18]<<24);
- case 18: c+=((uint64_t)k[17]<<16);
- case 17: c+=((uint64_t)k[16]<<8);
- /* the first byte of c is reserved for the length */
- case 16: b+=((uint64_t)k[15]<<56);
- case 15: b+=((uint64_t)k[14]<<48);
- case 14: b+=((uint64_t)k[13]<<40);
- case 13: b+=((uint64_t)k[12]<<32);
- case 12: b+=((uint64_t)k[11]<<24);
- case 11: b+=((uint64_t)k[10]<<16);
- case 10: b+=((uint64_t)k[ 9]<<8);
- case 9: b+=((uint64_t)k[ 8]);
- case 8: a+=((uint64_t)k[ 7]<<56);
- case 7: a+=((uint64_t)k[ 6]<<48);
- case 6: a+=((uint64_t)k[ 5]<<40);
- case 5: a+=((uint64_t)k[ 4]<<32);
- case 4: a+=((uint64_t)k[ 3]<<24);
- case 3: a+=((uint64_t)k[ 2]<<16);
- case 2: a+=((uint64_t)k[ 1]<<8);
- case 1: a+=((uint64_t)k[ 0]);
- /* case 0: nothing left to add */
- }
- mix64(a,b,c);
- /*-------------------------------------------- report the result */
- return c;
-}
-
-
-#ifdef SELOPT_WRITE
-
-static const char *
-write_selopt(void *dst, uint64_t base, size_t dstSize,
- string_map& strings, bool little_endian,
- size_t *outSize)
-{
- if (strings.size() == 0) return false;
-
- perfect_hash phash = make_perfect(strings);
- if (phash.capacity == 0) {
- return "perfect hash failed (selectors not optimized)";
- }
-
- size_t size = sizeof(objc_selopt_t)
- + phash.mask+1
- + phash.capacity * sizeof(objc_selopt_offset_t)
- + phash.capacity * sizeof(objc_selopt_check_t);
- if (size > dstSize) {
- return "selector section too small (selectors not optimized)";
- }
-
- uint8_t *buf = new uint8_t[size];
- objc_selopt_t *selopt = (objc_selopt_t *)buf;
-
- // Set header
- selopt->capacity = phash.capacity;
- selopt->occupied = phash.occupied;
- selopt->shift = phash.shift;
- selopt->mask = phash.mask;
- selopt->zero = 0;
- selopt->unused = 0;
- selopt->salt = phash.salt;
-
- // Set hash data
- for (uint32_t i = 0; i < 256; i++) {
- selopt->scramble[i] = phash.scramble[i];
- }
- for (uint32_t i = 0; i < phash.mask+1; i++) {
- selopt->tab[i] = phash.tab[i];
- }
-
- // Set offsets to ""
- for (uint32_t i = 0; i < phash.capacity; i++) {
- selopt->offsets()[i] =
- (objc_selopt_offset_t)offsetof(objc_selopt_t, zero);
- }
- // Set checkbytes to 0
- for (uint32_t i = 0; i < phash.capacity; i++) {
- selopt->checkbytes()[i] = 0;
- }
-
- // Set real string offsets and checkbytes
-# define SHIFT (64 - 8*sizeof(objc_selopt_offset_t))
- string_map::const_iterator s;
- for (s = strings.begin(); s != strings.end(); ++s) {
- int64_t offset = s->second - base;
- if ((offset<<SHIFT)>>SHIFT != offset) {
- delete[] buf;
- return "selector offset too big (selectors not optimized)";
- }
- selopt->set(s->first, (objc_selopt_offset_t)offset);
- }
-# undef SHIFT;
-
- // Byte-swap everything
-#define S32(x) x = little_endian ? OSSwapHostToLittleInt32(x) : OSSwapHostToBigInt32(x)
-#define S64(x) x = little_endian ? OSSwapHostToLittleInt64(x) : OSSwapHostToBigInt64(x)
- for (uint32_t i = 0; i < 256; i++) {
- S32(selopt->scramble[i]);
- }
- // tab is array of bytes, no swap needed
- for (uint32_t i = 0; i < phash.capacity; i++) {
- S32(selopt->offsets()[i]);
- }
-
- S32(selopt->capacity);
- S32(selopt->occupied);
- S32(selopt->shift);
- S32(selopt->mask);
- S32(selopt->zero);
- S64(selopt->salt);
-#undef S32
-#undef S64
-
- memcpy(dst, selopt, size);
- if (outSize) *outSize = size;
-
- delete[] buf;
- return NULL;
-}
-
-
-/*
-------------------------------------------------------------------------------
-This generates a minimal perfect hash function. That means, given a
-set of n keys, this determines a hash function that maps each of
-those keys into a value in 0..n-1 with no collisions.
-
-The perfect hash function first uses a normal hash function on the key
-to determine (a,b) such that the pair (a,b) is distinct for all
-keys, then it computes a^scramble[tab[b]] to get the final perfect hash.
-tab[] is an array of 1-byte values and scramble[] is a 256-term array of
-2-byte or 4-byte values. If there are n keys, the length of tab[] is a
-power of two between n/3 and n.
-
-I found the idea of computing distinct (a,b) values in "Practical minimal
-perfect hash functions for large databases", Fox, Heath, Chen, and Daoud,
-Communications of the ACM, January 1992. They found the idea in Chichelli
-(CACM Jan 1980). Beyond that, our methods differ.
-
-The key is hashed to a pair (a,b) where a in 0..*alen*-1 and b in
-0..*blen*-1. A fast hash function determines both a and b
-simultaneously. Any decent hash function is likely to produce
-hashes so that (a,b) is distinct for all pairs. I try the hash
-using different values of *salt* until all pairs are distinct.
-
-The final hash is (a XOR scramble[tab[b]]). *scramble* is a
-predetermined mapping of 0..255 into 0..smax-1. *tab* is an
-array that we fill in in such a way as to make the hash perfect.
-
-First we fill in all values of *tab* that are used by more than one
-key. We try all possible values for each position until one works.
-
-This leaves m unmapped keys and m values that something could hash to.
-If you treat unmapped keys as lefthand nodes and unused hash values
-as righthand nodes, and draw a line connecting each key to each hash
-value it could map to, you get a bipartite graph. We attempt to
-find a perfect matching in this graph. If we succeed, we have
-determined a perfect hash for the whole set of keys.
-
-*scramble* is used because (a^tab[i]) clusters keys around *a*.
-------------------------------------------------------------------------------
-*/
-
-typedef uint64_t ub8;
-#define UB8MAXVAL 0xffffffffffffffffLL
-#define UB8BITS 64
-typedef uint32_t ub4;
-#define UB4MAXVAL 0xffffffff
-#define UB4BITS 32
-typedef uint16_t ub2;
-#define UB2MAXVAL 0xffff
-#define UB2BITS 16
-typedef uint8_t ub1;
-#define UB1MAXVAL 0xff
-#define UB1BITS 8
-
-#define TRUE 1
-#define FALSE 0
-
-#define SCRAMBLE_LEN 256 // ((ub4)1<<16) /* length of *scramble* */
-#define RETRY_INITKEY 2048 /* number of times to try to find distinct (a,b) */
-#define RETRY_PERFECT 4 /* number of times to try to make a perfect hash */
-
-
-/* representation of a key */
-struct key
-{
- ub1 *name_k; /* the actual key */
- ub4 len_k; /* the length of the actual key */
- ub4 hash_k; /* the initial hash value for this key */
-/* beyond this point is mapping-dependent */
- ub4 a_k; /* a, of the key maps to (a,b) */
- ub4 b_k; /* b, of the key maps to (a,b) */
- struct key *nextb_k; /* next key with this b */
-};
-typedef struct key key;
-
-/* things indexed by b of original (a,b) pair */
-struct bstuff
-{
- ub2 val_b; /* hash=a^tabb[b].val_b */
- key *list_b; /* tabb[i].list_b is list of keys with b==i */
- ub4 listlen_b; /* length of list_b */
- ub4 water_b; /* high watermark of who has visited this map node */
-};
-typedef struct bstuff bstuff;
-
-/* things indexed by final hash value */
-struct hstuff
-{
- key *key_h; /* tabh[i].key_h is the key with a hash of i */
-};
-typedef struct hstuff hstuff;
-
-/* things indexed by queue position */
-struct qstuff
-{
- bstuff *b_q; /* b that currently occupies this hash */
- ub4 parent_q; /* queue position of parent that could use this hash */
- ub2 newval_q; /* what to change parent tab[b] to to use this hash */
- ub2 oldval_q; /* original value of tab[b] */
-};
-typedef struct qstuff qstuff;
-
-
-/*
-------------------------------------------------------------------------------
-Find the mapping that will produce a perfect hash
-------------------------------------------------------------------------------
-*/
-
-/* return the ceiling of the log (base 2) of val */
-static ub4 log2u(ub4 val)
-{
- ub4 i;
- for (i=0; ((ub4)1<<i) < val; ++i)
- ;
- return i;
-}
-
-/* compute p(x), where p is a permutation of 0..(1<<nbits)-1 */
-/* permute(0)=0. This is intended and useful. */
-static ub4 permute(ub4 x, ub4 nbits)
-// ub4 x; /* input, a value in some range */
-// ub4 nbits; /* input, number of bits in range */
-{
- int i;
- int mask = ((ub4)1<<nbits)-1; /* all ones */
- int const2 = 1+nbits/2;
- int const3 = 1+nbits/3;
- int const4 = 1+nbits/4;
- int const5 = 1+nbits/5;
- for (i=0; i<20; ++i)
- {
- x = (x+(x<<const2)) & mask;
- x = (x^(x>>const3));
- x = (x+(x<<const4)) & mask;
- x = (x^(x>>const5));
- }
- return x;
-}
-
-/* initialize scramble[] with distinct random values in 0..smax-1 */
-static void scrambleinit(ub4 *scramble, ub4 smax)
-// ub4 *scramble; /* hash is a^scramble[tab[b]] */
-// ub4 smax; /* scramble values should be in 0..smax-1 */
-{
- ub4 i;
-
- /* fill scramble[] with distinct random integers in 0..smax-1 */
- for (i=0; i<SCRAMBLE_LEN; ++i)
- {
- scramble[i] = permute(i, log2u(smax));
- }
-}
-
-
-/*
- * put keys in tabb according to key->b_k
- * check if the initial hash might work
- */
-static int inittab(bstuff *tabb, ub4 blen, key *keys, ub4 nkeys, int complete)
-// bstuff *tabb; /* output, list of keys with b for (a,b) */
-// ub4 blen; /* length of tabb */
-// key *keys; /* list of keys already hashed */
-// int complete; /* TRUE means to complete init despite collisions */
-{
- int nocollision = TRUE;
- ub4 i;
-
- memset((void *)tabb, 0, (size_t)(sizeof(bstuff)*blen));
-
- /* Two keys with the same (a,b) guarantees a collision */
- for (i = 0; i < nkeys; i++) {
- key *mykey = keys+i;
- key *otherkey;
-
- for (otherkey=tabb[mykey->b_k].list_b;
- otherkey;
- otherkey=otherkey->nextb_k)
- {
- if (mykey->a_k == otherkey->a_k)
- {
- nocollision = FALSE;
- if (!complete)
- return FALSE;
- }
- }
- ++tabb[mykey->b_k].listlen_b;
- mykey->nextb_k = tabb[mykey->b_k].list_b;
- tabb[mykey->b_k].list_b = mykey;
- }
-
- /* no two keys have the same (a,b) pair */
- return nocollision;
-}
-
-
-/* Do the initial hash for normal mode (use lookup and checksum) */
-static void initnorm(key *keys, ub4 nkeys, ub4 alen, ub4 blen, ub4 smax, ub8 salt)
-// key *keys; /* list of all keys */
-// ub4 alen; /* (a,b) has a in 0..alen-1, a power of 2 */
-// ub4 blen; /* (a,b) has b in 0..blen-1, a power of 2 */
-// ub4 smax; /* maximum range of computable hash values */
-// ub4 salt; /* used to initialize the hash function */
-// gencode *final; /* output, code for the final hash */
-{
- ub4 loga = log2u(alen); /* log based 2 of blen */
- ub4 i;
- for (i = 0; i < nkeys; i++) {
- key *mykey = keys+i;
- ub8 hash = lookup8(mykey->name_k, mykey->len_k, salt);
- mykey->a_k = (loga > 0) ? hash>>(UB8BITS-loga) : 0;
- mykey->b_k = (blen > 1) ? hash&(blen-1) : 0;
- }
-}
-
-
-/* Try to apply an augmenting list */
-static int apply(bstuff *tabb, hstuff *tabh, qstuff *tabq, ub4 blen, ub4 *scramble, ub4 tail, int rollback)
-// bstuff *tabb;
-// hstuff *tabh;
-// qstuff *tabq;
-// ub4 blen;
-// ub4 *scramble;
-// ub4 tail;
-// int rollback; /* FALSE applies augmenting path, TRUE rolls back */
-{
- ub4 hash;
- key *mykey;
- bstuff *pb;
- ub4 child;
- ub4 parent;
- ub4 stabb; /* scramble[tab[b]] */
-
- /* walk from child to parent */
- for (child=tail-1; child; child=parent)
- {
- parent = tabq[child].parent_q; /* find child's parent */
- pb = tabq[parent].b_q; /* find parent's list of siblings */
-
- /* erase old hash values */
- stabb = scramble[pb->val_b];
- for (mykey=pb->list_b; mykey; mykey=mykey->nextb_k)
- {
- hash = mykey->a_k^stabb;
- if (mykey == tabh[hash].key_h)
- { /* erase hash for all of child's siblings */
- tabh[hash].key_h = (key *)0;
- }
- }
-
- /* change pb->val_b, which will change the hashes of all parent siblings */
- pb->val_b = (rollback ? tabq[child].oldval_q : tabq[child].newval_q);
-
- /* set new hash values */
- stabb = scramble[pb->val_b];
- for (mykey=pb->list_b; mykey; mykey=mykey->nextb_k)
- {
- hash = mykey->a_k^stabb;
- if (rollback)
- {
- if (parent == 0) continue; /* root never had a hash */
- }
- else if (tabh[hash].key_h)
- {
- /* very rare: roll back any changes */
- apply(tabb, tabh, tabq, blen, scramble, tail, TRUE);
- return FALSE; /* failure, collision */
- }
- tabh[hash].key_h = mykey;
- }
- }
- return TRUE;
-}
-
-
-/*
--------------------------------------------------------------------------------
-augment(): Add item to the mapping.
-
-Construct a spanning tree of *b*s with *item* as root, where each
-parent can have all its hashes changed (by some new val_b) with
-at most one collision, and each child is the b of that collision.
-
-I got this from Tarjan's "Data Structures and Network Algorithms". The
-path from *item* to a *b* that can be remapped with no collision is
-an "augmenting path". Change values of tab[b] along the path so that
-the unmapped key gets mapped and the unused hash value gets used.
-
-Assuming 1 key per b, if m out of n hash values are still unused,
-you should expect the transitive closure to cover n/m nodes before
-an unused node is found. Sum(i=1..n)(n/i) is about nlogn, so expect
-this approach to take about nlogn time to map all single-key b's.
--------------------------------------------------------------------------------
-*/
-static int augment(bstuff *tabb, hstuff *tabh, qstuff *tabq, ub4 blen, ub4 *scramble, ub4 smax, bstuff *item, ub4 nkeys,
- ub4 highwater)
-// bstuff *tabb; /* stuff indexed by b */
-// hstuff *tabh; /* which key is associated with which hash, indexed by hash */
-// qstuff *tabq; /* queue of *b* values, this is the spanning tree */
-// ub4 blen; /* length of tabb */
-// ub4 *scramble; /* final hash is a^scramble[tab[b]] */
-// ub4 smax; /* highest value in scramble */
-// bstuff *item; /* &tabb[b] for the b to be mapped */
-// ub4 nkeys; /* final hash must be in 0..nkeys-1 */
-// ub4 highwater; /* a value higher than any now in tabb[].water_b */
-{
- ub4 q; /* current position walking through the queue */
- ub4 tail; /* tail of the queue. 0 is the head of the queue. */
- ub4 limit=UB1MAXVAL+1;
- ub4 highhash = smax;
-
- /* initialize the root of the spanning tree */
- tabq[0].b_q = item;
- tail = 1;
-
- /* construct the spanning tree by walking the queue, add children to tail */
- for (q=0; q<tail; ++q)
- {
- bstuff *myb = tabq[q].b_q; /* the b for this node */
- ub4 i; /* possible value for myb->val_b */
-
- if (q == 1)
- break; /* don't do transitive closure */
-
- for (i=0; i<limit; ++i)
- {
- bstuff *childb = (bstuff *)0; /* the b that this i maps to */
- key *mykey; /* for walking through myb's keys */
-
- for (mykey = myb->list_b; mykey; mykey=mykey->nextb_k)
- {
- key *childkey;
- ub4 hash = mykey->a_k^scramble[i];
-
- if (hash >= highhash) break; /* out of bounds */
- childkey = tabh[hash].key_h;
-
- if (childkey)
- {
- bstuff *hitb = &tabb[childkey->b_k];
-
- if (childb)
- {
- if (childb != hitb) break; /* hit at most one child b */
- }
- else
- {
- childb = hitb; /* remember this as childb */
- if (childb->water_b == highwater) break; /* already explored */
- }
- }
- }
- if (mykey) continue; /* myb with i has multiple collisions */
-
- /* add childb to the queue of reachable things */
- if (childb) childb->water_b = highwater;
- tabq[tail].b_q = childb;
- tabq[tail].newval_q = i; /* how to make parent (myb) use this hash */
- tabq[tail].oldval_q = myb->val_b; /* need this for rollback */
- tabq[tail].parent_q = q;
- ++tail;
-
- if (!childb)
- { /* found an *i* with no collisions? */
- /* try to apply the augmenting path */
- if (apply(tabb, tabh, tabq, blen, scramble, tail, FALSE))
- return TRUE; /* success, item was added to the perfect hash */
-
- --tail; /* don't know how to handle such a child! */
- }
- }
- }
- return FALSE;
-}
-
-
-/* find a mapping that makes this a perfect hash */
-static int perfect(bstuff *tabb, hstuff *tabh, qstuff *tabq, ub4 blen, ub4 smax, ub4 *scramble, ub4 nkeys)
-{
- ub4 maxkeys; /* maximum number of keys for any b */
- ub4 i, j;
-
-#if SELOPT_DEBUG
- fprintf(stderr, " blen %d smax %d nkeys %d\n", blen, smax, nkeys);
-#endif
-
- /* clear any state from previous attempts */
- memset((void *)tabh, 0, sizeof(hstuff)*smax);
- memset((void *)tabq, 0, sizeof(qstuff)*(blen+1));
-
- for (maxkeys=0,i=0; i<blen; ++i)
- if (tabb[i].listlen_b > maxkeys)
- maxkeys = tabb[i].listlen_b;
-
- /* In descending order by number of keys, map all *b*s */
- for (j=maxkeys; j>0; --j)
- for (i=0; i<blen; ++i)
- if (tabb[i].listlen_b == j)
- if (!augment(tabb, tabh, tabq, blen, scramble, smax, &tabb[i], nkeys,
- i+1))
- {
- return FALSE;
- }
-
- /* Success! We found a perfect hash of all keys into 0..nkeys-1. */
- return TRUE;
-}
-
-
-/* guess initial values for alen and blen */
-static void initalen(ub4 *alen, ub4 *blen, ub4 smax, ub4 nkeys)
-// ub4 *alen; /* output, initial alen */
-// ub4 *blen; /* output, initial blen */
-// ub4 smax; /* input, power of two greater or equal to max hash value */
-// ub4 nkeys; /* number of keys being hashed */
-{
- /*
- * Find initial *alen, *blen
- * Initial alen and blen values were found empirically. Some factors:
- *
- * If smax<256 there is no scramble, so tab[b] needs to cover 0..smax-1.
- *
- * alen and blen must be powers of 2 because the values in 0..alen-1 and
- * 0..blen-1 are produced by applying a bitmask to the initial hash function.
- *
- * alen must be less than smax, in fact less than nkeys, because otherwise
- * there would often be no i such that a^scramble[i] is in 0..nkeys-1 for
- * all the *a*s associated with a given *b*, so there would be no legal
- * value to assign to tab[b]. This only matters when we're doing a minimal
- * perfect hash.
- *
- * It takes around 800 trials to find distinct (a,b) with nkey=smax*(5/8)
- * and alen*blen = smax*smax/32.
- *
- * Values of blen less than smax/4 never work, and smax/2 always works.
- *
- * We want blen as small as possible because it is the number of bytes in
- * the huge array we must create for the perfect hash.
- *
- * When nkey <= smax*(5/8), blen=smax/4 works much more often with
- * alen=smax/8 than with alen=smax/4. Above smax*(5/8), blen=smax/4
- * doesn't seem to care whether alen=smax/8 or alen=smax/4. I think it
- * has something to do with 5/8 = 1/8 * 5. For example examine 80000,
- * 85000, and 90000 keys with different values of alen. This only matters
- * if we're doing a minimal perfect hash.
- *
- * When alen*blen <= 1<<UB4BITS, the initial hash must produce one integer.
- * Bigger than that it must produce two integers, which increases the
- * cost of the hash per character hashed.
- */
- *alen = smax; /* no reason to restrict alen to smax/2 */
- *blen = ((nkeys <= smax*0.6) ? smax/16 :
- (nkeys <= smax*0.8) ? smax/8 : smax/4);
-
- if (*alen < 1) *alen = 1;
- if (*blen < 1) *blen = 1;
-
-#if SELOPT_DEBUG
- fprintf(stderr, "alen %d blen %d smax %d nkeys %d\n", *alen, *blen, smax, nkeys);
-#endif
-}
-
-/*
-** Try to find a perfect hash function.
-** Return the successful initializer for the initial hash.
-** Return 0 if no perfect hash could be found.
-*/
-static int findhash(bstuff **tabb, ub4 *alen, ub4 *blen, ub8 *salt,
- ub4 *scramble, ub4 smax, key *keys, ub4 nkeys)
-// bstuff **tabb; /* output, tab[] of the perfect hash, length *blen */
-// ub4 *alen; /* output, 0..alen-1 is range for a of (a,b) */
-// ub4 *blen; /* output, 0..blen-1 is range for b of (a,b) */
-// ub4 *salt; /* output, initializes initial hash */
-// ub4 *scramble; /* input, hash = a^scramble[tab[b]] */
-// ub4 smax; /* input, scramble[i] in 0..smax-1 */
-// key *keys; /* input, keys to hash */
-// ub4 nkeys; /* input, number of keys being hashed */
-{
- ub4 bad_initkey; /* how many times did initkey fail? */
- ub4 bad_perfect; /* how many times did perfect fail? */
- ub4 si; /* trial initializer for initial hash */
- ub4 maxalen;
- hstuff *tabh; /* table of keys indexed by hash value */
- qstuff *tabq; /* table of stuff indexed by queue value, used by augment */
-
- /* guess initial values for alen and blen */
- initalen(alen, blen, smax, nkeys);
-
- scrambleinit(scramble, smax);
-
- maxalen = smax;
-
- /* allocate working memory */
- *tabb = new bstuff[*blen];
- tabq = new qstuff[*blen+1];
- tabh = new hstuff[smax];
-
- /* Actually find the perfect hash */
- *salt = 0;
- bad_initkey = 0;
- bad_perfect = 0;
- for (si=1; ; ++si)
- {
- ub4 rslinit;
- /* Try to find distinct (A,B) for all keys */
- *salt = si * 0x9e3779b97f4a7c13LL; /* golden ratio (arbitrary value) */
- initnorm(keys, nkeys, *alen, *blen, smax, *salt);
- rslinit = inittab(*tabb, *blen, keys, nkeys, FALSE);
- if (rslinit == 0)
- {
- /* didn't find distinct (a,b) */
- if (++bad_initkey >= RETRY_INITKEY)
- {
- /* Try to put more bits in (A,B) to make distinct (A,B) more likely */
- if (*alen < maxalen)
- {
- *alen *= 2;
- }
- else if (*blen < smax)
- {
- *blen *= 2;
- delete[] tabq;
- delete[] *tabb;
- *tabb = new bstuff[*blen];
- tabq = new qstuff[*blen+1];
- }
- bad_initkey = 0;
- bad_perfect = 0;
- }
- continue; /* two keys have same (a,b) pair */
- }
-
- /* Given distinct (A,B) for all keys, build a perfect hash */
- if (!perfect(*tabb, tabh, tabq, *blen, smax, scramble, nkeys))
- {
- if (++bad_perfect >= RETRY_PERFECT)
- {
- if (*blen < smax)
- {
- *blen *= 2;
- delete[] *tabb;
- delete[] tabq;
- *tabb = new bstuff[*blen];
- tabq = new qstuff[*blen+1];
- --si; /* we know this salt got distinct (A,B) */
- }
- else
- {
- return 0;
- }
- bad_perfect = 0;
- }
- continue;
- }
-
- break;
- }
-
- /* free working memory */
- delete[] tabh;
- delete[] tabq;
-
- return 1;
-}
-
-/*
-------------------------------------------------------------------------------
-Input/output type routines
-------------------------------------------------------------------------------
-*/
-
-/* get the list of keys */
-static void getkeys(key **keys, ub4 *nkeys, const string_map& strings)
-{
- key *buf = new key[strings.size()];
- size_t i;
- string_map::const_iterator s;
- for (i = 0, s = strings.begin(); s != strings.end(); ++s, ++i) {
- key *mykey = buf+i;
- mykey->name_k = (ub1 *)s->first;
- mykey->len_k = (ub4)strlen(s->first);
- }
- *keys = buf;
- *nkeys = strings.size();
-}
-
-
-static perfect_hash
-make_perfect(const string_map& strings)
-{
- ub4 nkeys; /* number of keys */
- key *keys; /* head of list of keys */
- bstuff *tab; /* table indexed by b */
- ub4 smax; /* scramble[] values in 0..smax-1, a power of 2 */
- ub4 alen; /* a in 0..alen-1, a power of 2 */
- ub4 blen; /* b in 0..blen-1, a power of 2 */
- ub8 salt; /* a parameter to the hash function */
- ub4 scramble[SCRAMBLE_LEN]; /* used in final hash function */
- int ok;
- int i;
- perfect_hash result;
-
- /* read in the list of keywords */
- getkeys(&keys, &nkeys, strings);
-
- /* find the hash */
- smax = ((ub4)1<<log2u(nkeys));
- ok = findhash(&tab, &alen, &blen, &salt,
- scramble, smax, keys, nkeys);
- if (!ok) {
- smax = 2 * ((ub4)1<<log2u(nkeys));
- ok = findhash(&tab, &alen, &blen, &salt,
- scramble, smax, keys, nkeys);
- }
- if (!ok) {
- bzero(&result, sizeof(result));
- } else {
- /* build the tables */
- result.capacity = smax;
- result.occupied = nkeys;
- result.shift = UB8BITS - log2u(alen);
- result.mask = blen - 1;
- result.salt = salt;
-
- result.tab = new uint8_t[blen];
- for (i = 0; i < blen; i++) {
- result.tab[i] = tab[i].val_b;
- }
- for (i = 0; i < 256; i++) {
- result.scramble[i] = scramble[i];
- }
- }
-
- delete[] keys;
- delete[] tab;
-
- return result;
-}
-
-// SELOPT_WRITE
-#endif
-
-// namespace objc_selopt
-};
-
-
-#endif
projects / apple / objc4.git / blobdiff