/* * $Id: linkhash.c,v 1.4 2006/01/26 02:16:28 mclark Exp $ * * Copyright (c) 2004, 2005 Metaparadigm Pte. Ltd. * Michael Clark * Copyright (c) 2009 Hewlett-Packard Development Company, L.P. * * This library is free software; you can redistribute it and/or modify * it under the terms of the MIT license. See COPYING for details. * */ #include #include #include #include #include #include #include #ifdef HAVE_ENDIAN_H # include /* attempt to define endianness */ #endif #include "random_seed.h" #include "linkhash.h" void lh_abort(const char *msg, ...) { va_list ap; va_start(ap, msg); vprintf(msg, ap); va_end(ap); exit(1); } unsigned long lh_ptr_hash(const void *k) { /* CAW: refactored to be 64bit nice */ return (unsigned long)((((ptrdiff_t)k * LH_PRIME) >> 4) & ULONG_MAX); } int lh_ptr_equal(const void *k1, const void *k2) { return (k1 == k2); } /* * hashlittle from lookup3.c, by Bob Jenkins, May 2006, Public Domain. * http://burtleburtle.net/bob/c/lookup3.c * minor modifications to make functions static so no symbols are exported * minor mofifications to compile with -Werror */ /* ------------------------------------------------------------------------------- lookup3.c, by Bob Jenkins, May 2006, Public Domain. 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. You probably want to use hashlittle(). hashlittle() and hashbig() hash byte arrays. hashlittle() is is faster than hashbig() on little-endian machines. Intel and AMD are little-endian machines. On second thought, you probably want hashlittle2(), which is identical to hashlittle() except it returns two 32-bit hashes for the price of one. You could implement hashbig2() if you wanted but I haven't bothered here. 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 hashword(). If you have a byte array (like a character string), use hashlittle(). If you have several byte arrays, or a mix of things, see the comments above hashlittle(). 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. ------------------------------------------------------------------------------- */ /* * My best guess at if you are big-endian or little-endian. This may * need adjustment. */ #if (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && \ __BYTE_ORDER == __LITTLE_ENDIAN) || \ (defined(i386) || defined(__i386__) || defined(__i486__) || \ defined(__i586__) || defined(__i686__) || defined(vax) || defined(MIPSEL)) # define HASH_LITTLE_ENDIAN 1 # define HASH_BIG_ENDIAN 0 #elif (defined(__BYTE_ORDER) && defined(__BIG_ENDIAN) && \ __BYTE_ORDER == __BIG_ENDIAN) || \ (defined(sparc) || defined(POWERPC) || defined(mc68000) || defined(sel)) # define HASH_LITTLE_ENDIAN 0 # define HASH_BIG_ENDIAN 1 #else # define HASH_LITTLE_ENDIAN 0 # define HASH_BIG_ENDIAN 0 #endif #define hashsize(n) ((uint32_t)1<<(n)) #define hashmask(n) (hashsize(n)-1) #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k)))) /* ------------------------------------------------------------------------------- mix -- mix 3 32-bit values reversibly. 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 -- final mixing of 3 32-bit values (a,b,c) into c 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); \ } /* ------------------------------------------------------------------------------- hashlittle() -- hash a variable-length key into a 32-bit value k : the key (the unaligned variable-length array of bytes) length : the length of the key, counting by bytes 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 12) { a += k[0]; b += k[1]; c += k[2]; mix(a,b,c); length -= 12; k += 3; } /*----------------------------- handle the last (probably partial) block */ /* * "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 : return c; /* zero length strings require no mixing */ } #else /* make valgrind happy */ const uint8_t *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; /* fall through */ case 10: c+=((uint32_t)k8[9])<<8; /* fall through */ case 9 : c+=k8[8]; /* fall through */ case 8 : b+=k[1]; a+=k[0]; break; case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */ case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */ case 5 : b+=k8[4]; /* fall through */ case 4 : a+=k[0]; break; case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */ case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */ case 1 : a+=k8[0]; break; case 0 : return c; } #endif /* !valgrind */ } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) { const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */ const uint8_t *k8; /*--------------- all but last block: aligned reads and different mixing */ 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; } /*----------------------------- handle the last (probably partial) block */ 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; /* fall through */ 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]; /* fall through */ 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; /* fall through */ case 6 : b+=k[2]; a+=k[0]+(((uint32_t)k[1])<<16); break; case 5 : b+=k8[4]; /* fall through */ case 4 : a+=k[0]+(((uint32_t)k[1])<<16); break; case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */ case 2 : a+=k[0]; break; case 1 : a+=k8[0]; break; case 0 : return c; /* zero length requires no mixing */ } } else { /* need to read the key one byte at a time */ const uint8_t *k = (const uint8_t *)key; /*--------------- all but the last block: affect some 32 bits of (a,b,c) */ 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; } /*-------------------------------- last block: affect all 32 bits of (c) */ switch(length) /* all the case statements fall through */ { 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; } unsigned long lh_char_hash(const void *k) { static volatile int random_seed = -1; if (random_seed == -1) { int seed; /* we can't use -1 as it is the unitialized sentinel */ while ((seed = json_c_get_random_seed()) == -1); #if defined __GNUC__ __sync_val_compare_and_swap(&random_seed, -1, seed); #elif defined _MSC_VER InterlockedCompareExchange(&random_seed, seed, -1); #else #warning "racy random seed initializtion if used by multiple threads" random_seed = seed; /* potentially racy */ #endif } return hashlittle((const char*)k, strlen((const char*)k), random_seed); } int lh_char_equal(const void *k1, const void *k2) { return (strcmp((const char*)k1, (const char*)k2) == 0); } struct lh_table* lh_table_new(int size, const char *name, lh_entry_free_fn *free_fn, lh_hash_fn *hash_fn, lh_equal_fn *equal_fn) { int i; struct lh_table *t; /* Allocate space for elements to avoid divisions by zero. */ assert(size > 0); t = (struct lh_table*)calloc(1, sizeof(struct lh_table)); if(!t) lh_abort("lh_table_new: calloc failed\n"); t->count = 0; t->size = size; t->name = name; t->table = (struct lh_entry*)calloc(size, sizeof(struct lh_entry)); if(!t->table) lh_abort("lh_table_new: calloc failed\n"); t->free_fn = free_fn; t->hash_fn = hash_fn; t->equal_fn = equal_fn; for(i = 0; i < size; i++) t->table[i].k = LH_EMPTY; return t; } struct lh_table* lh_kchar_table_new(int size, const char *name, lh_entry_free_fn *free_fn) { return lh_table_new(size, name, free_fn, lh_char_hash, lh_char_equal); } struct lh_table* lh_kptr_table_new(int size, const char *name, lh_entry_free_fn *free_fn) { return lh_table_new(size, name, free_fn, lh_ptr_hash, lh_ptr_equal); } void lh_table_resize(struct lh_table *t, int new_size) { struct lh_table *new_t; struct lh_entry *ent; new_t = lh_table_new(new_size, t->name, NULL, t->hash_fn, t->equal_fn); ent = t->head; while(ent) { lh_table_insert(new_t, ent->k, ent->v); ent = ent->next; } free(t->table); t->table = new_t->table; t->size = new_size; t->head = new_t->head; t->tail = new_t->tail; t->resizes++; free(new_t); } void lh_table_free(struct lh_table *t) { struct lh_entry *c; for(c = t->head; c != NULL; c = c->next) { if(t->free_fn) { t->free_fn(c); } } free(t->table); free(t); } int lh_table_insert(struct lh_table *t, void *k, const void *v) { unsigned long h, n; t->inserts++; if(t->count >= t->size * LH_LOAD_FACTOR) { /* Avoid signed integer overflow with large tables. */ int new_size = (t->size > INT_MAX / 2) ? INT_MAX : (t->size * 2); if (t->size != INT_MAX) lh_table_resize(t, new_size); } h = t->hash_fn(k); n = h % t->size; while( 1 ) { if(t->table[n].k == LH_EMPTY || t->table[n].k == LH_FREED) break; t->collisions++; if ((int)++n == t->size) n = 0; } t->table[n].k = k; t->table[n].v = v; t->count++; if(t->head == NULL) { t->head = t->tail = &t->table[n]; t->table[n].next = t->table[n].prev = NULL; } else { t->tail->next = &t->table[n]; t->table[n].prev = t->tail; t->table[n].next = NULL; t->tail = &t->table[n]; } return 0; } struct lh_entry* lh_table_lookup_entry(struct lh_table *t, const void *k) { unsigned long h = t->hash_fn(k); unsigned long n = h % t->size; int count = 0; t->lookups++; while( count < t->size ) { if(t->table[n].k == LH_EMPTY) return NULL; if(t->table[n].k != LH_FREED && t->equal_fn(t->table[n].k, k)) return &t->table[n]; if ((int)++n == t->size) n = 0; count++; } return NULL; } const void* lh_table_lookup(struct lh_table *t, const void *k) { void *result; lh_table_lookup_ex(t, k, &result); return result; } json_bool lh_table_lookup_ex(struct lh_table* t, const void* k, void **v) { struct lh_entry *e = lh_table_lookup_entry(t, k); if (e != NULL) { if (v != NULL) *v = (void *)e->v; return TRUE; /* key found */ } if (v != NULL) *v = NULL; return FALSE; /* key not found */ } int lh_table_delete_entry(struct lh_table *t, struct lh_entry *e) { ptrdiff_t n = (ptrdiff_t)(e - t->table); /* CAW: fixed to be 64bit nice, still need the crazy negative case... */ /* CAW: this is bad, really bad, maybe stack goes other direction on this machine... */ if(n < 0) { return -2; } if(t->table[n].k == LH_EMPTY || t->table[n].k == LH_FREED) return -1; t->count--; if(t->free_fn) t->free_fn(e); t->table[n].v = NULL; t->table[n].k = LH_FREED; if(t->tail == &t->table[n] && t->head == &t->table[n]) { t->head = t->tail = NULL; } else if (t->head == &t->table[n]) { t->head->next->prev = NULL; t->head = t->head->next; } else if (t->tail == &t->table[n]) { t->tail->prev->next = NULL; t->tail = t->tail->prev; } else { t->table[n].prev->next = t->table[n].next; t->table[n].next->prev = t->table[n].prev; } t->table[n].next = t->table[n].prev = NULL; return 0; } int lh_table_delete(struct lh_table *t, const void *k) { struct lh_entry *e = lh_table_lookup_entry(t, k); if(!e) return -1; return lh_table_delete_entry(t, e); } int lh_table_length(struct lh_table *t) { return t->count; }