/*      $NetBSD: hash.c,v 1.80 2025/04/22 19:28:50 rillig Exp $ */

/*
* Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Adam de Boor.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

/*
* Copyright (c) 1988, 1989 by Adam de Boor
* Copyright (c) 1989 by Berkeley Softworks
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Adam de Boor.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by the University of
*      California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

/* Hash tables with string keys and pointer values. */

#include "make.h"

/*      "@(#)hash.c     8.1 (Berkeley) 6/6/93"  */
MAKE_RCSID("$NetBSD: hash.c,v 1.80 2025/04/22 19:28:50 rillig Exp $");

/*
* The ratio of # entries to # buckets at which we rebuild the table to
* make it larger.
*/
#define rebuildLimit 3

/* This hash function matches Gosling's Emacs and java.lang.String. */
static unsigned
Hash_String(const char *key, const char **out_keyEnd)
{
       unsigned h;
       const char *p;

       h = 0;
       for (p = key; *p != '\0'; p++)
               h = 31 * h + (unsigned char)*p;

       *out_keyEnd = p;
       return h;
}

/* This hash function matches Gosling's Emacs and java.lang.String. */
unsigned
Hash_Substring(Substring key)
{
       unsigned h;
       const char *p;

       h = 0;
       for (p = key.start; p != key.end; p++)
               h = 31 * h + (unsigned char)*p;
       return h;
}

static HashEntry *
HashTable_Find(HashTable *t, Substring key, unsigned h)
{
       HashEntry *he;
       size_t keyLen = Substring_Length(key);

#ifdef DEBUG_HASH_LOOKUP
       DEBUG4(HASH, "HashTable_Find: %p h=%08x key=%.*s\n",
           t, h, (int)keyLen, key.start);
#endif

       for (he = t->buckets[h & t->bucketsMask]; he != NULL; he = he->next) {
               if (he->hash == h &&
                   strncmp(he->key, key.start, keyLen) == 0 &&
                   he->key[keyLen] == '\0')
                       break;
       }

       return he;
}

/* Set up the hash table. */
void
HashTable_Init(HashTable *t)
{
       unsigned n = 16, i;
       HashEntry **buckets = bmake_malloc(sizeof *buckets * n);
       for (i = 0; i < n; i++)
               buckets[i] = NULL;

       t->buckets = buckets;
       t->bucketsSize = n;
       t->numEntries = 0;
       t->bucketsMask = n - 1;
}

/*
* Remove everything from the hash table and free up the memory for the keys
* of the hash table, but not for the values associated to these keys.
*/
void
HashTable_Done(HashTable *t)
{
       HashEntry **buckets = t->buckets;
       size_t i, n = t->bucketsSize;

       for (i = 0; i < n; i++) {
               HashEntry *he = buckets[i];
               while (he != NULL) {
                       HashEntry *next = he->next;
                       free(he);
                       he = next;
               }
       }

       free(t->buckets);
#ifdef CLEANUP
       t->buckets = NULL;
#endif
}

/* Find the entry corresponding to the key, or return NULL. */
HashEntry *
HashTable_FindEntry(HashTable *t, const char *key)
{
       const char *keyEnd;
       unsigned h = Hash_String(key, &keyEnd);
       return HashTable_Find(t, Substring_Init(key, keyEnd), h);
}

/* Find the value corresponding to the key, or return NULL. */
void *
HashTable_FindValue(HashTable *t, const char *key)
{
       HashEntry *he = HashTable_FindEntry(t, key);
       return he != NULL ? he->value : NULL;
}

/*
* Find the value corresponding to the key and the precomputed hash,
* or return NULL.
*/
void *
HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned h)
{
       HashEntry *he = HashTable_Find(t, key, h);
       return he != NULL ? he->value : NULL;
}

static unsigned
HashTable_MaxChain(const HashTable *t)
{
       unsigned b, cl, max_cl = 0;
       for (b = 0; b < t->bucketsSize; b++) {
               const HashEntry *he = t->buckets[b];
               for (cl = 0; he != NULL; he = he->next)
                       cl++;
               if (cl > max_cl)
                       max_cl = cl;
       }
       return max_cl;
}

/*
* Make the hash table larger. Any bucket numbers from the old table become
* invalid; the hash values stay valid though.
*/
static void
HashTable_Enlarge(HashTable *t)
{
       unsigned oldSize = t->bucketsSize;
       HashEntry **oldBuckets = t->buckets;
       unsigned newSize = 2 * oldSize;
       unsigned newMask = newSize - 1;
       HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize);
       size_t i;

       for (i = 0; i < newSize; i++)
               newBuckets[i] = NULL;

       for (i = 0; i < oldSize; i++) {
               HashEntry *he = oldBuckets[i];
               while (he != NULL) {
                       HashEntry *next = he->next;
                       he->next = newBuckets[he->hash & newMask];
                       newBuckets[he->hash & newMask] = he;
                       he = next;
               }
       }

       free(oldBuckets);

       t->bucketsSize = newSize;
       t->bucketsMask = newMask;
       t->buckets = newBuckets;
       DEBUG4(HASH, "HashTable_Enlarge: %p size=%d entries=%d maxchain=%d\n",
           (void *)t, t->bucketsSize, t->numEntries, HashTable_MaxChain(t));
}

/*
* Find or create an entry corresponding to the key.
* Return in out_isNew whether a new entry has been created.
*/
HashEntry *
HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew)
{
       const char *keyEnd;
       unsigned h = Hash_String(key, &keyEnd);
       HashEntry *he = HashTable_Find(t, Substring_Init(key, keyEnd), h);

       if (he != NULL) {
               if (out_isNew != NULL)
                       *out_isNew = false;
               return he;
       }

       if (t->numEntries >= rebuildLimit * t->bucketsSize)
               HashTable_Enlarge(t);

       he = bmake_malloc(sizeof *he + (size_t)(keyEnd - key));
       he->value = NULL;
       he->hash = h;
       memcpy(he->key, key, (size_t)(keyEnd - key) + 1);

       he->next = t->buckets[h & t->bucketsMask];
       t->buckets[h & t->bucketsMask] = he;
       t->numEntries++;

       if (out_isNew != NULL)
               *out_isNew = true;
       return he;
}

void
HashTable_Set(HashTable *t, const char *key, void *value)
{
       HashEntry *he = HashTable_CreateEntry(t, key, NULL);
       HashEntry_Set(he, value);
}

/* Delete the entry from the table, don't free the value of the entry. */
void
HashTable_DeleteEntry(HashTable *t, HashEntry *he)
{
       HashEntry **ref = &t->buckets[he->hash & t->bucketsMask];

       for (; *ref != he; ref = &(*ref)->next)
               continue;
       *ref = he->next;
       free(he);
       t->numEntries--;
}

/*
* Place the next entry from the hash table in hi->entry, or return false if
* the end of the table is reached.
*/
bool
HashIter_Next(HashIter *hi)
{
       HashTable *t = hi->table;
       HashEntry *he = hi->entry;
       HashEntry **buckets = t->buckets;
       unsigned bucketsSize = t->bucketsSize;

       if (he != NULL)
               he = he->next;  /* skip the most recently returned entry */

       while (he == NULL) {    /* find the next nonempty chain */
               if (hi->nextBucket >= bucketsSize)
                       return false;
               he = buckets[hi->nextBucket++];
       }
       hi->entry = he;
       return true;
}

void
HashTable_DebugStats(const HashTable *t, const char *name)
{
       DEBUG4(HASH, "HashTable \"%s\": size=%u entries=%u maxchain=%u\n",
           name, t->bucketsSize, t->numEntries, HashTable_MaxChain(t));
}

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