/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*

 * PL hash table package.

 */

#include "plhash.h"

#include "prbit.h"

#include "prlog.h"

#include "prmem.h"

#include "prtypes.h"

#include <stdlib.h>

#include <string.h>

/* Compute the number of buckets in ht */

#define NBUCKETS(ht)    (1 << (PL_HASH_BITS - (ht)->shift))

/* The smallest table has 16 buckets */

#define MINBUCKETSLOG2  4

#define MINBUCKETS      (1 << MINBUCKETSLOG2)

/* Compute the maximum entries given n buckets that we will tolerate, ~90% */

#define OVERLOADED(n)   ((n) - ((n) >> 3))

/* Compute the number of entries below which we shrink the table by half */

#define UNDERLOADED(n)  (((n) > MINBUCKETS) ? ((n) >> 2) : 0)

/*

** Stubs for default hash allocator ops.

*/

static void * PR_CALLBACK

DefaultAllocTable(void *pool, PRSize size)

{

    return PR_MALLOC(size);

}

static void PR_CALLBACK

DefaultFreeTable(void *pool, void *item)

{

    PR_Free(item);

}

static PLHashEntry * PR_CALLBACK

DefaultAllocEntry(void *pool, const void *key)

{

    return PR_NEW(PLHashEntry);

}

static void PR_CALLBACK

DefaultFreeEntry(void *pool, PLHashEntry *he, PRUintn flag)

{

    if (flag == HT_FREE_ENTRY) {

        PR_Free(he);

    }

}

static PLHashAllocOps defaultHashAllocOps = {

    DefaultAllocTable, DefaultFreeTable,

    DefaultAllocEntry, DefaultFreeEntry

};

PR_IMPLEMENT(PLHashTable *)

PL_NewHashTable(PRUint32 n, PLHashFunction keyHash,

                PLHashComparator keyCompare, PLHashComparator valueCompare,

                const PLHashAllocOps *allocOps, void *allocPriv)

{

    PLHashTable *ht;

    PRSize nb;

    if (n <= MINBUCKETS) {

        n = MINBUCKETSLOG2;

    } else {

        n = PR_CeilingLog2(n);

        if ((PRInt32)n < 0) {

            return 0;

        }

    }

    if (!allocOps) {

        allocOps = &defaultHashAllocOps;

    }

    ht = (PLHashTable*)((*allocOps->allocTable)(allocPriv, sizeof *ht));

    if (!ht) {

        return 0;

    }

    memset(ht, 0, sizeof *ht);

    ht->shift = PL_HASH_BITS - n;

    n = 1 << n;

    nb = n * sizeof(PLHashEntry *);

    ht->buckets = (PLHashEntry**)((*allocOps->allocTable)(allocPriv, nb));

    if (!ht->buckets) {

        (*allocOps->freeTable)(allocPriv, ht);

        return 0;

    }

    memset(ht->buckets, 0, nb);

    ht->keyHash = keyHash;

    ht->keyCompare = keyCompare;

    ht->valueCompare = valueCompare;

    ht->allocOps = allocOps;

    ht->allocPriv = allocPriv;

    return ht;

}

PR_IMPLEMENT(void)

PL_HashTableDestroy(PLHashTable *ht)

{

    PRUint32 i, n;

    PLHashEntry *he, *next;

    const PLHashAllocOps *allocOps = ht->allocOps;

    void *allocPriv = ht->allocPriv;

    n = NBUCKETS(ht);

    for (i = 0; i < n; i++) {

        for (he = ht->buckets[i]; he; he = next) {

            next = he->next;

            (*allocOps->freeEntry)(allocPriv, he, HT_FREE_ENTRY);

        }

    }

#ifdef DEBUG

    memset(ht->buckets, 0xDB, n * sizeof ht->buckets[0]);

#endif

    (*allocOps->freeTable)(allocPriv, ht->buckets);

#ifdef DEBUG

    memset(ht, 0xDB, sizeof *ht);

#endif

    (*allocOps->freeTable)(allocPriv, ht);

}

/*

** Multiplicative hash, from Knuth 6.4.

*/

#define GOLDEN_RATIO    0x9E3779B9U  /* 2/(1+sqrt(5))*(2^32) */

PR_IMPLEMENT(PLHashEntry **)

PL_HashTableRawLookup(PLHashTable *ht, PLHashNumber keyHash, const void *key)

{

    PLHashEntry *he, **hep, **hep0;

    PLHashNumber h;

#ifdef HASHMETER

    ht->nlookups++;

#endif

    h = keyHash * GOLDEN_RATIO;

    h >>= ht->shift;

    hep = hep0 = &ht->buckets[h];

    while ((he = *hep) != 0) {

        if (he->keyHash == keyHash && (*ht->keyCompare)(key, he->key)) {

            /* Move to front of chain if not already there */

            if (hep != hep0) {

                *hep = he->next;

                he->next = *hep0;

                *hep0 = he;

            }

            return hep0;

        }

        hep = &he->next;

#ifdef HASHMETER

        ht->nsteps++;

#endif

    }

    return hep;

}

/*

** Same as PL_HashTableRawLookup but doesn't reorder the hash entries.

*/

PR_IMPLEMENT(PLHashEntry **)

PL_HashTableRawLookupConst(PLHashTable *ht, PLHashNumber keyHash,

                           const void *key)

{

    PLHashEntry *he, **hep;

    PLHashNumber h;

#ifdef HASHMETER

    ht->nlookups++;

#endif

    h = keyHash * GOLDEN_RATIO;

    h >>= ht->shift;

    hep = &ht->buckets[h];

    while ((he = *hep) != 0) {

        if (he->keyHash == keyHash && (*ht->keyCompare)(key, he->key)) {

            break;

        }

        hep = &he->next;

#ifdef HASHMETER

        ht->nsteps++;

#endif

    }

    return hep;

}

PR_IMPLEMENT(PLHashEntry *)

PL_HashTableRawAdd(PLHashTable *ht, PLHashEntry **hep,

                   PLHashNumber keyHash, const void *key, void *value)

{

    PRUint32 i, n;

    PLHashEntry *he, *next, **oldbuckets;

    PRSize nb;

    /* Grow the table if it is overloaded */

    n = NBUCKETS(ht);

    if (ht->nentries >= OVERLOADED(n)) {

        oldbuckets = ht->buckets;

        nb = 2 * n * sizeof(PLHashEntry *);

        ht->buckets = (PLHashEntry**)

                      ((*ht->allocOps->allocTable)(ht->allocPriv, nb));

        if (!ht->buckets) {

            ht->buckets = oldbuckets;

            return 0;

        }

        memset(ht->buckets, 0, nb);

#ifdef HASHMETER

        ht->ngrows++;

#endif

        ht->shift--;

        for (i = 0; i < n; i++) {

            for (he = oldbuckets[i]; he; he = next) {

                next = he->next;

                hep = PL_HashTableRawLookup(ht, he->keyHash, he->key);

                PR_ASSERT(*hep == 0);

                he->next = 0;

                *hep = he;

            }

        }

#ifdef DEBUG

        memset(oldbuckets, 0xDB, n * sizeof oldbuckets[0]);

#endif

        (*ht->allocOps->freeTable)(ht->allocPriv, oldbuckets);

        hep = PL_HashTableRawLookup(ht, keyHash, key);

    }

    /* Make a new key value entry */

    he = (*ht->allocOps->allocEntry)(ht->allocPriv, key);

    if (!he) {

        return 0;

    }

    he->keyHash = keyHash;

    he->key = key;

    he->value = value;

    he->next = *hep;

    *hep = he;

    ht->nentries++;

    return he;

}

PR_IMPLEMENT(PLHashEntry *)

PL_HashTableAdd(PLHashTable *ht, const void *key, void *value)

{

    PLHashNumber keyHash;

    PLHashEntry *he, **hep;

    keyHash = (*ht->keyHash)(key);

    hep = PL_HashTableRawLookup(ht, keyHash, key);

    if ((he = *hep) != 0) {

        /* Hit; see if values match */

        if ((*ht->valueCompare)(he->value, value)) {

            /* key,value pair is already present in table */

            return he;

        }

        if (he->value) {

            (*ht->allocOps->freeEntry)(ht->allocPriv, he, HT_FREE_VALUE);

        }

        he->value = value;

        return he;

    }

    return PL_HashTableRawAdd(ht, hep, keyHash, key, value);

}

PR_IMPLEMENT(void)

PL_HashTableRawRemove(PLHashTable *ht, PLHashEntry **hep, PLHashEntry *he)

{

    PRUint32 i, n;

    PLHashEntry *next, **oldbuckets;

    PRSize nb;

    *hep = he->next;

    (*ht->allocOps->freeEntry)(ht->allocPriv, he, HT_FREE_ENTRY);

    /* Shrink table if it's underloaded */

    n = NBUCKETS(ht);

    if (--ht->nentries < UNDERLOADED(n)) {

        oldbuckets = ht->buckets;

        nb = n * sizeof(PLHashEntry*) / 2;

        ht->buckets = (PLHashEntry**)(

                          (*ht->allocOps->allocTable)(ht->allocPriv, nb));

        if (!ht->buckets) {

            ht->buckets = oldbuckets;

            return;

        }

        memset(ht->buckets, 0, nb);

#ifdef HASHMETER

        ht->nshrinks++;

#endif

        ht->shift++;

        for (i = 0; i < n; i++) {

            for (he = oldbuckets[i]; he; he = next) {

                next = he->next;

                hep = PL_HashTableRawLookup(ht, he->keyHash, he->key);

                PR_ASSERT(*hep == 0);

                he->next = 0;

                *hep = he;

            }

        }

#ifdef DEBUG

        memset(oldbuckets, 0xDB, n * sizeof oldbuckets[0]);

#endif

        (*ht->allocOps->freeTable)(ht->allocPriv, oldbuckets);

    }

}

PR_IMPLEMENT(PRBool)

PL_HashTableRemove(PLHashTable *ht, const void *key)

{

    PLHashNumber keyHash;

    PLHashEntry *he, **hep;

    keyHash = (*ht->keyHash)(key);

    hep = PL_HashTableRawLookup(ht, keyHash, key);

    if ((he = *hep) == 0) {

        return PR_FALSE;

    }

    /* Hit; remove element */

    PL_HashTableRawRemove(ht, hep, he);

    return PR_TRUE;

}

PR_IMPLEMENT(void *)

PL_HashTableLookup(PLHashTable *ht, const void *key)

{

    PLHashNumber keyHash;

    PLHashEntry *he, **hep;

    keyHash = (*ht->keyHash)(key);

    hep = PL_HashTableRawLookup(ht, keyHash, key);

    if ((he = *hep) != 0) {

        return he->value;

    }

    return 0;

}

/*

** Same as PL_HashTableLookup but doesn't reorder the hash entries.

*/

PR_IMPLEMENT(void *)

PL_HashTableLookupConst(PLHashTable *ht, const void *key)

{

    PLHashNumber keyHash;

    PLHashEntry *he, **hep;

    keyHash = (*ht->keyHash)(key);

    hep = PL_HashTableRawLookupConst(ht, keyHash, key);

    if ((he = *hep) != 0) {

        return he->value;

    }

    return 0;

}

/*

** Iterate over the entries in the hash table calling func for each

** entry found. Stop if "f" says to (return value & PR_ENUMERATE_STOP).

** Return a count of the number of elements scanned.

*/

PR_IMPLEMENT(int)

PL_HashTableEnumerateEntries(PLHashTable *ht, PLHashEnumerator f, void *arg)

{

    PLHashEntry *he, **hep;

    PRUint32 i, nbuckets;

    int rv, n = 0;

    PLHashEntry *todo = 0;

    nbuckets = NBUCKETS(ht);

    for (i = 0; i < nbuckets; i++) {

        hep = &ht->buckets[i];

        while ((he = *hep) != 0) {

            rv = (*f)(he, n, arg);

            n++;

            if (rv & (HT_ENUMERATE_REMOVE | HT_ENUMERATE_UNHASH)) {

                *hep = he->next;

                if (rv & HT_ENUMERATE_REMOVE) {

                    he->next = todo;

                    todo = he;

                }

            } else {

                hep = &he->next;

            }

            if (rv & HT_ENUMERATE_STOP) {

                goto out;

            }

        }

    }

out:

    hep = &todo;

    while ((he = *hep) != 0) {

        PL_HashTableRawRemove(ht, hep, he);

    }

    return n;

}

#ifdef HASHMETER

#include <math.h>

#include <stdio.h>

PR_IMPLEMENT(void)

PL_HashTableDumpMeter(PLHashTable *ht, PLHashEnumerator dump, FILE *fp)

{

    double mean, variance;

    PRUint32 nchains, nbuckets;

    PRUint32 i, n, maxChain, maxChainLen;

    PLHashEntry *he;

    variance = 0;

    nchains = 0;

    maxChainLen = 0;

    nbuckets = NBUCKETS(ht);

    for (i = 0; i < nbuckets; i++) {

        he = ht->buckets[i];

        if (!he) {

            continue;

        }

        nchains++;

        for (n = 0; he; he = he->next) {

            n++;

        }

        variance += n * n;

        if (n > maxChainLen) {

            maxChainLen = n;

            maxChain = i;

        }

    }

    mean = (double)ht->nentries / nchains;

    variance = fabs(variance / nchains - mean * mean);

    fprintf(fp, "\nHash table statistics:\n");

    fprintf(fp, "     number of lookups: %u\n", ht->nlookups);

    fprintf(fp, "     number of entries: %u\n", ht->nentries);

    fprintf(fp, "       number of grows: %u\n", ht->ngrows);

    fprintf(fp, "     number of shrinks: %u\n", ht->nshrinks);

    fprintf(fp, "   mean steps per hash: %g\n", (double)ht->nsteps

            / ht->nlookups);

    fprintf(fp, "mean hash chain length: %g\n", mean);

    fprintf(fp, "    standard deviation: %g\n", sqrt(variance));

    fprintf(fp, " max hash chain length: %u\n", maxChainLen);

    fprintf(fp, "        max hash chain: [%u]\n", maxChain);

    for (he = ht->buckets[maxChain], i = 0; he; he = he->next, i++)

        if ((*dump)(he, i, fp) != HT_ENUMERATE_NEXT) {

            break;

        }

}

#endif /* HASHMETER */

PR_IMPLEMENT(int)

PL_HashTableDump(PLHashTable *ht, PLHashEnumerator dump, FILE *fp)

{

    int count;

    count = PL_HashTableEnumerateEntries(ht, dump, fp);

#ifdef HASHMETER

    PL_HashTableDumpMeter(ht, dump, fp);

#endif

    return count;

}

PR_IMPLEMENT(PLHashNumber)

PL_HashString(const void *key)

{

    PLHashNumber h;

    const PRUint8 *s;

    h = 0;

    for (s = (const PRUint8*)key; *s; s++) {

        h = PR_ROTATE_LEFT32(h, 4) ^ *s;

    }

    return h;

}

PR_IMPLEMENT(int)

PL_CompareStrings(const void *v1, const void *v2)

{

    return strcmp((const char*)v1, (const char*)v2) == 0;

}

PR_IMPLEMENT(int)

PL_CompareValues(const void *v1, const void *v2)

{

    return v1 == v2;

}