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+/* An expandable hash tables datatype.
+ Copyright (C) 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
+ Contributed by Vladimir Makarov (vmakarov@cygnus.com).
+
+This file is part of the libiberty library.
+Libiberty is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public
+License as published by the Free Software Foundation; either
+version 2 of the License, or (at your option) any later version.
+
+Libiberty is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with libiberty; see the file COPYING.LIB. If
+not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA. */
+
+/* This package implements basic hash table functionality. It is possible
+ to search for an entry, create an entry and destroy an entry.
+
+ Elements in the table are generic pointers.
+
+ The size of the table is not fixed; if the occupancy of the table
+ grows too high the hash table will be expanded.
+
+ The abstract data implementation is based on generalized Algorithm D
+ from Knuth's book "The art of computer programming". Hash table is
+ expanded by creation of new hash table and transferring elements from
+ the old table to the new table. */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <sys/types.h>
+
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif
+
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+
+#ifdef HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+
+#include <stdio.h>
+
+#include "libiberty.h"
+#include "hashtab.h"
+
+/* This macro defines reserved value for empty table entry. */
+
+#define EMPTY_ENTRY ((PTR) 0)
+
+/* This macro defines reserved value for table entry which contained
+ a deleted element. */
+
+#define DELETED_ENTRY ((PTR) 1)
+
+static unsigned long higher_prime_number PARAMS ((unsigned long));
+static hashval_t hash_pointer PARAMS ((const void *));
+static int eq_pointer PARAMS ((const void *, const void *));
+static int htab_expand PARAMS ((htab_t));
+static PTR *find_empty_slot_for_expand PARAMS ((htab_t, hashval_t));
+
+/* At some point, we could make these be NULL, and modify the
+ hash-table routines to handle NULL specially; that would avoid
+ function-call overhead for the common case of hashing pointers. */
+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. */
+
+static unsigned long
+higher_prime_number (n)
+ unsigned long n;
+{
+ /* These are primes that are near, but slightly smaller than, a
+ power of two. */
+ static const unsigned long primes[] = {
+ (unsigned long) 7,
+ (unsigned long) 13,
+ (unsigned long) 31,
+ (unsigned long) 61,
+ (unsigned long) 127,
+ (unsigned long) 251,
+ (unsigned long) 509,
+ (unsigned long) 1021,
+ (unsigned long) 2039,
+ (unsigned long) 4093,
+ (unsigned long) 8191,
+ (unsigned long) 16381,
+ (unsigned long) 32749,
+ (unsigned long) 65521,
+ (unsigned long) 131071,
+ (unsigned long) 262139,
+ (unsigned long) 524287,
+ (unsigned long) 1048573,
+ (unsigned long) 2097143,
+ (unsigned long) 4194301,
+ (unsigned long) 8388593,
+ (unsigned long) 16777213,
+ (unsigned long) 33554393,
+ (unsigned long) 67108859,
+ (unsigned long) 134217689,
+ (unsigned long) 268435399,
+ (unsigned long) 536870909,
+ (unsigned long) 1073741789,
+ (unsigned long) 2147483647,
+ /* 4294967291L */
+ ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
+ };
+
+ const unsigned long *low = &primes[0];
+ const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
+
+ while (low != high)
+ {
+ const unsigned long *mid = low + (high - low) / 2;
+ if (n > *mid)
+ low = mid + 1;
+ else
+ high = mid;
+ }
+
+ /* If we've run out of primes, abort. */
+ if (n > *low)
+ {
+ fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
+ abort ();
+ }
+
+ return *low;
+}
+
+/* Returns a hash code for P. */
+
+static hashval_t
+hash_pointer (p)
+ const PTR p;
+{
+ return (hashval_t) ((long)p >> 3);
+}
+
+/* Returns non-zero if P1 and P2 are equal. */
+
+static int
+eq_pointer (p1, p2)
+ const PTR p1;
+ const PTR p2;
+{
+ return p1 == p2;
+}
+
+/* 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, or NULL if memory allocation fails. */
+
+htab_t
+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;
+
+ size = higher_prime_number (size);
+ 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->hash_f = hash_f;
+ result->eq_f = eq_f;
+ result->del_f = del_f;
+ result->alloc_f = alloc_f;
+ result->free_f = free_f;
+ return result;
+}
+
+/* As above, but use the variants of alloc_f and free_f which accept
+ an extra argument. */
+
+htab_t
+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;
+
+ size = higher_prime_number (size);
+ result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab));
+ if (result == NULL)
+ return NULL;
+ result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR));
+ if (result->entries == NULL)
+ {
+ if (free_f != NULL)
+ (*free_f) (alloc_arg, result);
+ return NULL;
+ }
+ result->size = size;
+ result->hash_f = hash_f;
+ result->eq_f = eq_f;
+ result->del_f = del_f;
+ 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. */
+
+void
+htab_delete (htab)
+ htab_t htab;
+{
+ 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]);
+
+ if (htab->free_f != NULL)
+ {
+ (*htab->free_f) (htab->entries);
+ (*htab->free_f) (htab);
+ }
+ else if (htab->free_with_arg_f != NULL)
+ {
+ (*htab->free_with_arg_f) (htab->alloc_arg, htab->entries);
+ (*htab->free_with_arg_f) (htab->alloc_arg, htab);
+ }
+}
+
+/* This function clears all entries in the given hash table. */
+
+void
+htab_empty (htab)
+ htab_t htab;
+{
+ 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]);
+
+ memset (htab->entries, 0, htab->size * sizeof (PTR));
+}
+
+/* Similar to htab_find_slot, but without several unwanted side effects:
+ - Does not call htab->eq_f when it finds an existing entry.
+ - Does not change the count of elements/searches/collisions in the
+ hash table.
+ This function also assumes there are no deleted entries in the table.
+ HASH is the hash value for the element to be inserted. */
+
+static PTR *
+find_empty_slot_for_expand (htab, hash)
+ htab_t htab;
+ hashval_t hash;
+{
+ size_t size = htab->size;
+ unsigned int index = hash % size;
+ PTR *slot = htab->entries + index;
+ hashval_t hash2;
+
+ if (*slot == EMPTY_ENTRY)
+ return slot;
+ else if (*slot == DELETED_ENTRY)
+ abort ();
+
+ hash2 = 1 + hash % (size - 2);
+ for (;;)
+ {
+ index += hash2;
+ if (index >= size)
+ index -= size;
+
+ slot = htab->entries + index;
+ if (*slot == EMPTY_ENTRY)
+ return slot;
+ else if (*slot == DELETED_ENTRY)
+ abort ();
+ }
+}
+
+/* The following function changes size of memory allocated for the
+ entries and repeatedly inserts the table elements. The occupancy
+ of the table after the call will be about 50%. Naturally the hash
+ table must already exist. Remember also that the place of the
+ table entries is changed. If memory allocation failures are allowed,
+ this function will return zero, indicating that the table could not be
+ expanded. If all goes well, it will return a non-zero value. */
+
+static int
+htab_expand (htab)
+ htab_t htab;
+{
+ PTR *oentries;
+ PTR *olimit;
+ PTR *p;
+ PTR *nentries;
+ size_t nsize;
+
+ oentries = htab->entries;
+ olimit = oentries + htab->size;
+
+ /* Resize only when table after removal of unused elements is either
+ too full or too empty. */
+ if ((htab->n_elements - htab->n_deleted) * 2 > htab->size
+ || ((htab->n_elements - htab->n_deleted) * 8 < htab->size
+ && htab->size > 32))
+ nsize = higher_prime_number ((htab->n_elements - htab->n_deleted) * 2);
+ else
+ nsize = htab->size;
+
+ 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->n_elements -= htab->n_deleted;
+ htab->n_deleted = 0;
+
+ p = oentries;
+ do
+ {
+ PTR x = *p;
+
+ if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
+ {
+ PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x));
+
+ *q = x;
+ }
+
+ p++;
+ }
+ while (p < olimit);
+
+ 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;
+}
+
+/* This function searches for a hash table entry equal to the given
+ element. It cannot be used to insert or delete an element. */
+
+PTR
+htab_find_with_hash (htab, element, hash)
+ htab_t htab;
+ const PTR element;
+ hashval_t hash;
+{
+ unsigned int index;
+ hashval_t hash2;
+ size_t size;
+ PTR entry;
+
+ htab->searches++;
+ size = htab->size;
+ index = hash % size;
+
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY
+ || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
+ return entry;
+
+ hash2 = 1 + hash % (size - 2);
+
+ for (;;)
+ {
+ htab->collisions++;
+ index += hash2;
+ if (index >= size)
+ index -= size;
+
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY
+ || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
+ return entry;
+ }
+}
+
+/* Like htab_find_slot_with_hash, but compute the hash value from the
+ element. */
+
+PTR
+htab_find (htab, element)
+ htab_t htab;
+ const PTR element;
+{
+ return htab_find_with_hash (htab, element, (*htab->hash_f) (element));
+}
+
+/* This function searches for a hash table slot containing an entry
+ equal to the given element. To delete an entry, call this with
+ INSERT = 0, then call htab_clear_slot on the slot returned (possibly
+ after doing some checks). To insert an entry, call this with
+ INSERT = 1, then write the value you want into the returned slot.
+ When inserting an entry, NULL may be returned if memory allocation
+ fails. */
+
+PTR *
+htab_find_slot_with_hash (htab, element, hash, insert)
+ htab_t htab;
+ const PTR element;
+ hashval_t hash;
+ enum insert_option insert;
+{
+ PTR *first_deleted_slot;
+ unsigned int index;
+ hashval_t 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;
+ index = hash % size;
+
+ 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 = 1 + hash % (size - 2);
+ for (;;)
+ {
+ htab->collisions++;
+ index += hash2;
+ if (index >= size)
+ index -= size;
+
+ entry = htab->entries[index];
+ if (entry == EMPTY_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))
+ return &htab->entries[index];
+ }
+
+ 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
+ element. */
+
+PTR *
+htab_find_slot (htab, element, insert)
+ htab_t htab;
+ const PTR element;
+ enum insert_option insert;
+{
+ return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element),
+ insert);
+}
+
+/* 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_t htab;
+ PTR element;
+{
+ PTR *slot;
+
+ slot = htab_find_slot (htab, element, NO_INSERT);
+ if (*slot == EMPTY_ENTRY)
+ return;
+
+ if (htab->del_f)
+ (*htab->del_f) (*slot);
+
+ *slot = DELETED_ENTRY;
+ htab->n_deleted++;
+}
+
+/* This function clears a specified slot in a hash table. It is
+ useful when you've already done the lookup and don't want to do it
+ again. */
+
+void
+htab_clear_slot (htab, slot)
+ htab_t htab;
+ PTR *slot;
+{
+ if (slot < htab->entries || slot >= htab->entries + htab->size
+ || *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY)
+ abort ();
+
+ if (htab->del_f)
+ (*htab->del_f) (*slot);
+
+ *slot = DELETED_ENTRY;
+ htab->n_deleted++;
+}
+
+/* This function scans over the entire hash table calling
+ CALLBACK for each live entry. If CALLBACK returns false,
+ the iteration stops. INFO is passed as CALLBACK's second
+ argument. */
+
+void
+htab_traverse_noresize (htab, callback, info)
+ htab_t htab;
+ htab_trav callback;
+ PTR info;
+{
+ PTR *slot;
+ PTR *limit;
+
+ slot = htab->entries;
+ limit = slot + htab->size;
+
+ do
+ {
+ PTR x = *slot;
+
+ if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
+ if (!(*callback) (slot, info))
+ break;
+ }
+ while (++slot < limit);
+}
+
+/* Like htab_traverse_noresize, but does resize the table when it is
+ too empty to improve effectivity of subsequent calls. */
+
+void
+htab_traverse (htab, callback, info)
+ htab_t htab;
+ htab_trav callback;
+ PTR info;
+{
+ if ((htab->n_elements - htab->n_deleted) * 8 < htab->size)
+ htab_expand (htab);
+
+ htab_traverse_noresize (htab, callback, info);
+}
+
+/* Return the current size of given hash table. */
+
+size_t
+htab_size (htab)
+ htab_t htab;
+{
+ return htab->size;
+}
+
+/* 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;
+}
+
+/* Return the fraction of fixed collisions during all work with given
+ hash table. */
+
+double
+htab_collisions (htab)
+ htab_t htab;
+{
+ if (htab->searches == 0)
+ return 0.0;
+
+ 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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