/* An expandable hash tables datatype.
- Copyright (C) 1999, 2000 Free Software Foundation, Inc.
+ Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004
+ Free Software Foundation, Inc.
Contributed by Vladimir Makarov (vmakarov@cygnus.com).
This file is part of the libiberty library.
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
-
#ifdef HAVE_STRING_H
#include <string.h>
#endif
+#ifdef HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+#ifdef HAVE_LIMITS_H
+#include <limits.h>
+#endif
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
#include <stdio.h>
#include "libiberty.h"
+#include "ansidecl.h"
#include "hashtab.h"
+#ifndef CHAR_BIT
+#define CHAR_BIT 8
+#endif
+
/* This macro defines reserved value for empty table entry. */
#define EMPTY_ENTRY ((PTR) 0)
#define DELETED_ENTRY ((PTR) 1)
-static unsigned long higher_prime_number PARAMS ((unsigned long));
+static unsigned int higher_prime_index PARAMS ((unsigned long));
+static hashval_t htab_mod_1 PARAMS ((hashval_t, hashval_t, hashval_t, int));
+static hashval_t htab_mod PARAMS ((hashval_t, htab_t));
+static hashval_t htab_mod_m2 PARAMS ((hashval_t, htab_t));
static hashval_t hash_pointer PARAMS ((const void *));
static int eq_pointer PARAMS ((const void *, const void *));
static int htab_expand PARAMS ((htab_t));
htab_hash htab_hash_pointer = hash_pointer;
htab_eq htab_eq_pointer = eq_pointer;
-/* The following function returns a nearest prime number which is
- greater than N, and near a power of two. */
+/* Table of primes and multiplicative inverses.
+
+ Note that these are not minimally reduced inverses. Unlike when generating
+ code to divide by a constant, we want to be able to use the same algorithm
+ all the time. All of these inverses (are implied to) have bit 32 set.
+
+ For the record, here's the function that computed the table; it's a
+ vastly simplified version of the function of the same name from gcc. */
+
+#if 0
+unsigned int
+ceil_log2 (unsigned int x)
+{
+ int i;
+ for (i = 31; i >= 0 ; --i)
+ if (x > (1u << i))
+ return i+1;
+ abort ();
+}
+
+unsigned int
+choose_multiplier (unsigned int d, unsigned int *mlp, unsigned char *shiftp)
+{
+ unsigned long long mhigh;
+ double nx;
+ int lgup, post_shift;
+ int pow, pow2;
+ int n = 32, precision = 32;
+
+ lgup = ceil_log2 (d);
+ pow = n + lgup;
+ pow2 = n + lgup - precision;
+
+ nx = ldexp (1.0, pow) + ldexp (1.0, pow2);
+ mhigh = nx / d;
+
+ *shiftp = lgup - 1;
+ *mlp = mhigh;
+ return mhigh >> 32;
+}
+#endif
-static unsigned long
-higher_prime_number (n)
+struct prime_ent
+{
+ hashval_t prime;
+ hashval_t inv;
+ hashval_t inv_m2; /* inverse of prime-2 */
+ hashval_t shift;
+};
+
+static struct prime_ent const prime_tab[] = {
+ { 7, 0x24924925, 0x9999999b, 2 },
+ { 13, 0x3b13b13c, 0x745d1747, 3 },
+ { 31, 0x08421085, 0x1a7b9612, 4 },
+ { 61, 0x0c9714fc, 0x15b1e5f8, 5 },
+ { 127, 0x02040811, 0x0624dd30, 6 },
+ { 251, 0x05197f7e, 0x073260a5, 7 },
+ { 509, 0x01824366, 0x02864fc8, 8 },
+ { 1021, 0x00c0906d, 0x014191f7, 9 },
+ { 2039, 0x0121456f, 0x0161e69e, 10 },
+ { 4093, 0x00300902, 0x00501908, 11 },
+ { 8191, 0x00080041, 0x00180241, 12 },
+ { 16381, 0x000c0091, 0x00140191, 13 },
+ { 32749, 0x002605a5, 0x002a06e6, 14 },
+ { 65521, 0x000f00e2, 0x00110122, 15 },
+ { 131071, 0x00008001, 0x00018003, 16 },
+ { 262139, 0x00014002, 0x0001c004, 17 },
+ { 524287, 0x00002001, 0x00006001, 18 },
+ { 1048573, 0x00003001, 0x00005001, 19 },
+ { 2097143, 0x00004801, 0x00005801, 20 },
+ { 4194301, 0x00000c01, 0x00001401, 21 },
+ { 8388593, 0x00001e01, 0x00002201, 22 },
+ { 16777213, 0x00000301, 0x00000501, 23 },
+ { 33554393, 0x00001381, 0x00001481, 24 },
+ { 67108859, 0x00000141, 0x000001c1, 25 },
+ { 134217689, 0x000004e1, 0x00000521, 26 },
+ { 268435399, 0x00000391, 0x000003b1, 27 },
+ { 536870909, 0x00000019, 0x00000029, 28 },
+ { 1073741789, 0x0000008d, 0x00000095, 29 },
+ { 2147483647, 0x00000003, 0x00000007, 30 },
+ /* Avoid "decimal constant so large it is unsigned" for 4294967291. */
+ { 0xfffffffb, 0x00000006, 0x00000008, 31 }
+};
+
+/* The following function returns an index into the above table of the
+ nearest prime number which is greater than N, and near a power of two. */
+
+static unsigned int
+higher_prime_index (n)
unsigned long n;
{
- /* These are primes that are near, but slightly smaller than, a
- power of two. */
- static unsigned long primes[] = {
- 2,
- 7,
- 13,
- 31,
- 61,
- 127,
- 251,
- 509,
- 1021,
- 2039,
- 4093,
- 8191,
- 16381,
- 32749,
- 65521,
- 131071,
- 262139,
- 524287,
- 1048573,
- 2097143,
- 4194301,
- 8388593,
- 16777213,
- 33554393,
- 67108859,
- 134217689,
- 268435399,
- 536870909,
- 1073741789,
- 2147483647,
- 4294967291
- };
-
- unsigned long* low = &primes[0];
- unsigned long* high = &primes[sizeof(primes) / sizeof(primes[0])];
+ unsigned int low = 0;
+ unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]);
while (low != high)
{
- unsigned long* mid = low + (high - low) / 2;
- if (n > *mid)
+ unsigned int mid = low + (high - low) / 2;
+ if (n > prime_tab[mid].prime)
low = mid + 1;
else
high = mid;
}
/* If we've run out of primes, abort. */
- if (n > *low)
+ if (n > prime_tab[low].prime)
{
fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
abort ();
}
- return *low;
+ return low;
}
/* Returns a hash code for P. */
return p1 == p2;
}
+/* Return the current size of given hash table. */
+
+inline size_t
+htab_size (htab)
+ htab_t htab;
+{
+ return htab->size;
+}
+
+/* Return the current number of elements in given hash table. */
+
+inline size_t
+htab_elements (htab)
+ htab_t htab;
+{
+ return htab->n_elements - htab->n_deleted;
+}
+
+/* Return X % Y. */
+
+static inline hashval_t
+htab_mod_1 (x, y, inv, shift)
+ hashval_t x, y, inv;
+ int shift;
+{
+ /* The multiplicative inverses computed above are for 32-bit types, and
+ requires that we be able to compute a highpart multiply. */
+#ifdef UNSIGNED_64BIT_TYPE
+ __extension__ typedef UNSIGNED_64BIT_TYPE ull;
+ if (sizeof (hashval_t) * CHAR_BIT <= 32)
+ {
+ hashval_t t1, t2, t3, t4, q, r;
+
+ t1 = ((ull)x * inv) >> 32;
+ t2 = x - t1;
+ t3 = t2 >> 1;
+ t4 = t1 + t3;
+ q = t4 >> shift;
+ r = x - (q * y);
+
+ return r;
+ }
+#endif
+
+ /* Otherwise just use the native division routines. */
+ return x % y;
+}
+
+/* Compute the primary hash for HASH given HTAB's current size. */
+
+static inline hashval_t
+htab_mod (hash, htab)
+ hashval_t hash;
+ htab_t htab;
+{
+ const struct prime_ent *p = &prime_tab[htab->size_prime_index];
+ return htab_mod_1 (hash, p->prime, p->inv, p->shift);
+}
+
+/* Compute the secondary hash for HASH given HTAB's current size. */
+
+static inline hashval_t
+htab_mod_m2 (hash, htab)
+ hashval_t hash;
+ htab_t htab;
+{
+ const struct prime_ent *p = &prime_tab[htab->size_prime_index];
+ return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift);
+}
+
/* This function creates table with length slightly longer than given
source length. Created hash table is initiated as empty (all the
hash table entries are EMPTY_ENTRY). The function returns the
- created hash table. Memory allocation must not fail. */
+ created hash table, or NULL if memory allocation fails. */
htab_t
-htab_create (size, hash_f, eq_f, del_f)
+htab_create_alloc (size, hash_f, eq_f, del_f, alloc_f, free_f)
size_t size;
htab_hash hash_f;
htab_eq eq_f;
htab_del del_f;
+ htab_alloc alloc_f;
+ htab_free free_f;
{
htab_t result;
+ unsigned int size_prime_index;
+
+ size_prime_index = higher_prime_index (size);
+ size = prime_tab[size_prime_index].prime;
- size = higher_prime_number (size);
- result = (htab_t) xcalloc (1, sizeof (struct htab));
- result->entries = (PTR *) xcalloc (size, sizeof (PTR));
+ result = (htab_t) (*alloc_f) (1, sizeof (struct htab));
+ if (result == NULL)
+ return NULL;
+ result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR));
+ if (result->entries == NULL)
+ {
+ if (free_f != NULL)
+ (*free_f) (result);
+ return NULL;
+ }
result->size = size;
+ result->size_prime_index = size_prime_index;
result->hash_f = hash_f;
result->eq_f = eq_f;
result->del_f = del_f;
- result->return_allocation_failure = 0;
+ result->alloc_f = alloc_f;
+ result->free_f = free_f;
return result;
}
-/* This function creates table with length slightly longer than given
- source length. The created hash table is initiated as empty (all the
- hash table entries are EMPTY_ENTRY). The function returns the created
- hash table. Memory allocation may fail; it may return NULL. */
+/* As above, but use the variants of alloc_f and free_f which accept
+ an extra argument. */
htab_t
-htab_try_create (size, hash_f, eq_f, del_f)
+htab_create_alloc_ex (size, hash_f, eq_f, del_f, alloc_arg, alloc_f,
+ free_f)
size_t size;
htab_hash hash_f;
htab_eq eq_f;
htab_del del_f;
+ PTR alloc_arg;
+ htab_alloc_with_arg alloc_f;
+ htab_free_with_arg free_f;
{
htab_t result;
+ unsigned int size_prime_index;
+
+ size_prime_index = higher_prime_index (size);
+ size = prime_tab[size_prime_index].prime;
- size = higher_prime_number (size);
- result = (htab_t) calloc (1, sizeof (struct htab));
+ result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab));
if (result == NULL)
return NULL;
-
- result->entries = (PTR *) calloc (size, sizeof (PTR));
+ result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR));
if (result->entries == NULL)
{
- free (result);
+ if (free_f != NULL)
+ (*free_f) (alloc_arg, result);
return NULL;
}
-
result->size = size;
+ result->size_prime_index = size_prime_index;
result->hash_f = hash_f;
result->eq_f = eq_f;
result->del_f = del_f;
- result->return_allocation_failure = 1;
+ result->alloc_arg = alloc_arg;
+ result->alloc_with_arg_f = alloc_f;
+ result->free_with_arg_f = free_f;
return result;
}
+/* Update the function pointers and allocation parameter in the htab_t. */
+
+void
+htab_set_functions_ex (htab, hash_f, eq_f, del_f, alloc_arg, alloc_f, free_f)
+ htab_t htab;
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
+ PTR alloc_arg;
+ htab_alloc_with_arg alloc_f;
+ htab_free_with_arg free_f;
+{
+ htab->hash_f = hash_f;
+ htab->eq_f = eq_f;
+ htab->del_f = del_f;
+ htab->alloc_arg = alloc_arg;
+ htab->alloc_with_arg_f = alloc_f;
+ htab->free_with_arg_f = free_f;
+}
+
+/* These functions exist solely for backward compatibility. */
+
+#undef htab_create
+htab_t
+htab_create (size, hash_f, eq_f, del_f)
+ size_t size;
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
+{
+ return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free);
+}
+
+htab_t
+htab_try_create (size, hash_f, eq_f, del_f)
+ size_t size;
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
+{
+ return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free);
+}
+
/* This function frees all memory allocated for given hash table.
Naturally the hash table must already exist. */
htab_delete (htab)
htab_t htab;
{
+ size_t size = htab_size (htab);
+ PTR *entries = htab->entries;
int i;
if (htab->del_f)
- for (i = htab->size - 1; i >= 0; i--)
- if (htab->entries[i] != EMPTY_ENTRY
- && htab->entries[i] != DELETED_ENTRY)
- (*htab->del_f) (htab->entries[i]);
+ for (i = size - 1; i >= 0; i--)
+ if (entries[i] != EMPTY_ENTRY && entries[i] != DELETED_ENTRY)
+ (*htab->del_f) (entries[i]);
- free (htab->entries);
- free (htab);
+ if (htab->free_f != NULL)
+ {
+ (*htab->free_f) (entries);
+ (*htab->free_f) (htab);
+ }
+ else if (htab->free_with_arg_f != NULL)
+ {
+ (*htab->free_with_arg_f) (htab->alloc_arg, entries);
+ (*htab->free_with_arg_f) (htab->alloc_arg, htab);
+ }
}
/* This function clears all entries in the given hash table. */
htab_empty (htab)
htab_t htab;
{
+ size_t size = htab_size (htab);
+ PTR *entries = htab->entries;
int i;
if (htab->del_f)
- for (i = htab->size - 1; i >= 0; i--)
- if (htab->entries[i] != EMPTY_ENTRY
- && htab->entries[i] != DELETED_ENTRY)
- (*htab->del_f) (htab->entries[i]);
+ for (i = size - 1; i >= 0; i--)
+ if (entries[i] != EMPTY_ENTRY && entries[i] != DELETED_ENTRY)
+ (*htab->del_f) (entries[i]);
- memset (htab->entries, 0, htab->size * sizeof (PTR));
+ memset (entries, 0, size * sizeof (PTR));
}
/* Similar to htab_find_slot, but without several unwanted side effects:
htab_t htab;
hashval_t hash;
{
- size_t size = htab->size;
- hashval_t hash2 = 1 + hash % (size - 2);
- unsigned int index = hash % size;
+ hashval_t index = htab_mod (hash, htab);
+ size_t size = htab_size (htab);
+ PTR *slot = htab->entries + index;
+ hashval_t hash2;
+
+ if (*slot == EMPTY_ENTRY)
+ return slot;
+ else if (*slot == DELETED_ENTRY)
+ abort ();
+ hash2 = htab_mod_m2 (hash, htab);
for (;;)
{
- PTR *slot = htab->entries + index;
+ index += hash2;
+ if (index >= size)
+ index -= size;
+ slot = htab->entries + index;
if (*slot == EMPTY_ENTRY)
return slot;
else if (*slot == DELETED_ENTRY)
abort ();
-
- index += hash2;
- if (index >= size)
- index -= size;
}
}
PTR *oentries;
PTR *olimit;
PTR *p;
+ PTR *nentries;
+ size_t nsize, osize, elts;
+ unsigned int oindex, nindex;
oentries = htab->entries;
- olimit = oentries + htab->size;
-
- htab->size = higher_prime_number (htab->size * 2);
-
- if (htab->return_allocation_failure)
+ oindex = htab->size_prime_index;
+ osize = htab->size;
+ olimit = oentries + osize;
+ elts = htab_elements (htab);
+
+ /* Resize only when table after removal of unused elements is either
+ too full or too empty. */
+ if (elts * 2 > osize || (elts * 8 < osize && osize > 32))
{
- PTR *nentries = (PTR *) calloc (htab->size, sizeof (PTR *));
- if (nentries == NULL)
- return 0;
- htab->entries = nentries;
+ nindex = higher_prime_index (elts * 2);
+ nsize = prime_tab[nindex].prime;
}
else
- htab->entries = (PTR *) xcalloc (htab->size, sizeof (PTR *));
+ {
+ nindex = oindex;
+ nsize = osize;
+ }
+ if (htab->alloc_with_arg_f != NULL)
+ nentries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize,
+ sizeof (PTR *));
+ else
+ nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *));
+ if (nentries == NULL)
+ return 0;
+ htab->entries = nentries;
+ htab->size = nsize;
+ htab->size_prime_index = nindex;
htab->n_elements -= htab->n_deleted;
htab->n_deleted = 0;
}
while (p < olimit);
- free (oentries);
+ if (htab->free_f != NULL)
+ (*htab->free_f) (oentries);
+ else if (htab->free_with_arg_f != NULL)
+ (*htab->free_with_arg_f) (htab->alloc_arg, oentries);
return 1;
}
const PTR element;
hashval_t hash;
{
- unsigned int index;
- hashval_t hash2;
+ hashval_t index, hash2;
size_t size;
PTR entry;
htab->searches++;
- size = htab->size;
- index = hash % size;
+ size = htab_size (htab);
+ index = htab_mod (hash, htab);
entry = htab->entries[index];
if (entry == EMPTY_ENTRY
|| (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
return entry;
- hash2 = 1 + hash % (size - 2);
-
+ hash2 = htab_mod_m2 (hash, htab);
for (;;)
{
htab->collisions++;
enum insert_option insert;
{
PTR *first_deleted_slot;
- unsigned int index;
- hashval_t hash2;
+ hashval_t index, hash2;
size_t size;
+ PTR entry;
- if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4
- && htab_expand (htab) == 0)
- return NULL;
+ size = htab_size (htab);
+ if (insert == INSERT && size * 3 <= htab->n_elements * 4)
+ {
+ if (htab_expand (htab) == 0)
+ return NULL;
+ size = htab_size (htab);
+ }
- size = htab->size;
- hash2 = 1 + hash % (size - 2);
- index = hash % size;
+ index = htab_mod (hash, htab);
htab->searches++;
first_deleted_slot = NULL;
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY)
+ goto empty_entry;
+ else if (entry == DELETED_ENTRY)
+ first_deleted_slot = &htab->entries[index];
+ else if ((*htab->eq_f) (entry, element))
+ return &htab->entries[index];
+
+ hash2 = htab_mod_m2 (hash, htab);
for (;;)
{
- PTR entry = htab->entries[index];
+ htab->collisions++;
+ index += hash2;
+ if (index >= size)
+ index -= size;
+
+ entry = htab->entries[index];
if (entry == EMPTY_ENTRY)
- {
- if (insert == NO_INSERT)
- return NULL;
-
- htab->n_elements++;
-
- if (first_deleted_slot)
- {
- *first_deleted_slot = EMPTY_ENTRY;
- return first_deleted_slot;
- }
-
- return &htab->entries[index];
- }
-
- if (entry == DELETED_ENTRY)
+ goto empty_entry;
+ else if (entry == DELETED_ENTRY)
{
if (!first_deleted_slot)
first_deleted_slot = &htab->entries[index];
}
- else if ((*htab->eq_f) (entry, element))
+ else if ((*htab->eq_f) (entry, element))
return &htab->entries[index];
-
- htab->collisions++;
- index += hash2;
- if (index >= size)
- index -= size;
}
+
+ empty_entry:
+ if (insert == NO_INSERT)
+ return NULL;
+
+ if (first_deleted_slot)
+ {
+ htab->n_deleted--;
+ *first_deleted_slot = EMPTY_ENTRY;
+ return first_deleted_slot;
+ }
+
+ htab->n_elements++;
+ return &htab->entries[index];
}
/* Like htab_find_slot_with_hash, but compute the hash value from the
}
/* This function deletes an element with the given value from hash
+ table (the hash is computed from the element). If there is no matching
+ element in the hash table, this function does nothing. */
+
+void
+htab_remove_elt (htab, element)
+ htab_t htab;
+ PTR element;
+{
+ htab_remove_elt_with_hash (htab, element, (*htab->hash_f) (element));
+}
+
+
+/* This function deletes an element with the given value from hash
table. If there is no matching element in the hash table, this
function does nothing. */
void
-htab_remove_elt (htab, element)
+htab_remove_elt_with_hash (htab, element, hash)
htab_t htab;
PTR element;
+ hashval_t hash;
{
PTR *slot;
- slot = htab_find_slot (htab, element, NO_INSERT);
+ slot = htab_find_slot_with_hash (htab, element, hash, NO_INSERT);
if (*slot == EMPTY_ENTRY)
return;
htab_t htab;
PTR *slot;
{
- if (slot < htab->entries || slot >= htab->entries + htab->size
+ if (slot < htab->entries || slot >= htab->entries + htab_size (htab)
|| *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY)
abort ();
argument. */
void
-htab_traverse (htab, callback, info)
+htab_traverse_noresize (htab, callback, info)
htab_t htab;
htab_trav callback;
PTR info;
{
- PTR *slot = htab->entries;
- PTR *limit = slot + htab->size;
+ PTR *slot;
+ PTR *limit;
+
+ slot = htab->entries;
+ limit = slot + htab_size (htab);
do
{
while (++slot < limit);
}
-/* Return the current size of given hash table. */
+/* Like htab_traverse_noresize, but does resize the table when it is
+ too empty to improve effectivity of subsequent calls. */
-size_t
-htab_size (htab)
+void
+htab_traverse (htab, callback, info)
htab_t htab;
+ htab_trav callback;
+ PTR info;
{
- return htab->size;
-}
+ if (htab_elements (htab) * 8 < htab_size (htab))
+ htab_expand (htab);
-/* Return the current number of elements in given hash table. */
-
-size_t
-htab_elements (htab)
- htab_t htab;
-{
- return htab->n_elements - htab->n_deleted;
+ htab_traverse_noresize (htab, callback, info);
}
/* Return the fraction of fixed collisions during all work with given
return (double) htab->collisions / (double) htab->searches;
}
+
+/* Hash P as a null-terminated string.
+
+ Copied from gcc/hashtable.c. Zack had the following to say with respect
+ to applicability, though note that unlike hashtable.c, this hash table
+ implementation re-hashes rather than chain buckets.
+
+ http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html
+ From: Zack Weinberg <zackw@panix.com>
+ Date: Fri, 17 Aug 2001 02:15:56 -0400
+
+ I got it by extracting all the identifiers from all the source code
+ I had lying around in mid-1999, and testing many recurrences of
+ the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either
+ prime numbers or the appropriate identity. This was the best one.
+ I don't remember exactly what constituted "best", except I was
+ looking at bucket-length distributions mostly.
+
+ So it should be very good at hashing identifiers, but might not be
+ as good at arbitrary strings.
+
+ I'll add that it thoroughly trounces the hash functions recommended
+ for this use at http://burtleburtle.net/bob/hash/index.html, both
+ on speed and bucket distribution. I haven't tried it against the
+ function they just started using for Perl's hashes. */
+
+hashval_t
+htab_hash_string (p)
+ const PTR p;
+{
+ const unsigned char *str = (const unsigned char *) p;
+ hashval_t r = 0;
+ unsigned char c;
+
+ while ((c = *str++) != 0)
+ r = r * 67 + c - 113;
+
+ return r;
+}
+
+/* DERIVED FROM:
+--------------------------------------------------------------------
+lookup2.c, by Bob Jenkins, December 1996, 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.
+--------------------------------------------------------------------
+*/
+
+/*
+--------------------------------------------------------------------
+mix -- mix 3 32-bit values reversibly.
+For every delta with one or two bit set, and the deltas of all three
+ high bits or all three low bits, whether the original value of a,b,c
+ is almost all zero or is uniformly distributed,
+* If mix() is run forward or backward, at least 32 bits in a,b,c
+ have at least 1/4 probability of changing.
+* If mix() is run forward, every bit of c will change between 1/3 and
+ 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.)
+mix() was built out of 36 single-cycle latency instructions in a
+ structure that could supported 2x parallelism, like so:
+ a -= b;
+ a -= c; x = (c>>13);
+ b -= c; a ^= x;
+ b -= a; x = (a<<8);
+ c -= a; b ^= x;
+ c -= b; x = (b>>13);
+ ...
+ Unfortunately, superscalar Pentiums and Sparcs can't take advantage
+ of that parallelism. They've also turned some of those single-cycle
+ latency instructions into multi-cycle latency instructions. Still,
+ this is the fastest good hash I could find. There were about 2^^68
+ to choose from. I only looked at a billion or so.
+--------------------------------------------------------------------
+*/
+/* same, but slower, works on systems that might have 8 byte hashval_t's */
+#define mix(a,b,c) \
+{ \
+ a -= b; a -= c; a ^= (c>>13); \
+ b -= c; b -= a; b ^= (a<< 8); \
+ c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
+ a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
+ b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
+ c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
+ a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
+ b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
+ c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
+}
+
+/*
+--------------------------------------------------------------------
+hash() -- hash a variable-length key into a 32-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 4-byte value
+Returns a 32-bit value. Every bit of the key affects every bit of
+the return value. Every 1-bit and 2-bit delta achieves avalanche.
+About 36+6len 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 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 (ub1 **)k, do it like this:
+ for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);
+
+By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this
+code any way you wish, private, educational, or commercial. It's free.
+
+See http://burtleburtle.net/bob/hash/evahash.html
+Use for hash table lookup, or anything where one collision in 2^32 is
+acceptable. Do NOT use for cryptographic purposes.
+--------------------------------------------------------------------
+*/
+
+hashval_t iterative_hash (k_in, length, initval)
+ const PTR k_in; /* the key */
+ register size_t length; /* the length of the key */
+ register hashval_t initval; /* the previous hash, or an arbitrary value */
+{
+ register const unsigned char *k = (const unsigned char *)k_in;
+ register hashval_t a,b,c,len;
+
+ /* Set up the internal state */
+ len = length;
+ a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
+ c = initval; /* the previous hash value */
+
+ /*---------------------------------------- handle most of the key */
+#ifndef WORDS_BIGENDIAN
+ /* On a little-endian machine, if the data is 4-byte aligned we can hash
+ by word for better speed. This gives nondeterministic results on
+ big-endian machines. */
+ if (sizeof (hashval_t) == 4 && (((size_t)k)&3) == 0)
+ while (len >= 12) /* aligned */
+ {
+ a += *(hashval_t *)(k+0);
+ b += *(hashval_t *)(k+4);
+ c += *(hashval_t *)(k+8);
+ mix(a,b,c);
+ k += 12; len -= 12;
+ }
+ else /* unaligned */
+#endif
+ while (len >= 12)
+ {
+ a += (k[0] +((hashval_t)k[1]<<8) +((hashval_t)k[2]<<16) +((hashval_t)k[3]<<24));
+ b += (k[4] +((hashval_t)k[5]<<8) +((hashval_t)k[6]<<16) +((hashval_t)k[7]<<24));
+ c += (k[8] +((hashval_t)k[9]<<8) +((hashval_t)k[10]<<16)+((hashval_t)k[11]<<24));
+ mix(a,b,c);
+ k += 12; len -= 12;
+ }
+
+ /*------------------------------------- handle the last 11 bytes */
+ c += length;
+ switch(len) /* all the case statements fall through */
+ {
+ case 11: c+=((hashval_t)k[10]<<24);
+ case 10: c+=((hashval_t)k[9]<<16);
+ case 9 : c+=((hashval_t)k[8]<<8);
+ /* the first byte of c is reserved for the length */
+ case 8 : b+=((hashval_t)k[7]<<24);
+ case 7 : b+=((hashval_t)k[6]<<16);
+ case 6 : b+=((hashval_t)k[5]<<8);
+ case 5 : b+=k[4];
+ case 4 : a+=((hashval_t)k[3]<<24);
+ case 3 : a+=((hashval_t)k[2]<<16);
+ case 2 : a+=((hashval_t)k[1]<<8);
+ case 1 : a+=k[0];
+ /* case 0: nothing left to add */
+ }
+ mix(a,b,c);
+ /*-------------------------------------------- report the result */
+ return c;
+}
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