/* -*- 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; }