LCOV - app.info - objdir/dist/include/pldhash.h

LCOV - code coverage report
| Current view: | directory - objdir/dist/include - pldhash.h (source / functions) |  | Found | Hit | Coverage |
| Test: | app.info | Lines: | 2 | 2 | 100.0 %
| Date: | 2012-06-02 | Functions: | 2 | 2 | 100.0 %

           1                 : /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
           2                 : /* ***** BEGIN LICENSE BLOCK *****
           3                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
           4                 :  *
           5                 :  * The contents of this file are subject to the Mozilla Public License Version
           6                 :  * 1.1 (the "License"); you may not use this file except in compliance with
           7                 :  * the License. You may obtain a copy of the License at
           8                 :  * http://www.mozilla.org/MPL/
           9                 :  *
          10                 :  * Software distributed under the License is distributed on an "AS IS" basis,
          11                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
          12                 :  * for the specific language governing rights and limitations under the
          13                 :  * License.
          14                 :  *
          15                 :  * The Original Code is Mozilla JavaScript code.
          16                 :  *
          17                 :  * The Initial Developer of the Original Code is
          18                 :  * Netscape Communications Corporation.
          19                 :  * Portions created by the Initial Developer are Copyright (C) 1999-2001
          20                 :  * the Initial Developer. All Rights Reserved.
          21                 :  *
          22                 :  * Contributor(s):
          23                 :  *   Brendan Eich <brendan@mozilla.org> (Original Author)
          24                 :  *
          25                 :  * Alternatively, the contents of this file may be used under the terms of
          26                 :  * either of the GNU General Public License Version 2 or later (the "GPL"),
          27                 :  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
          28                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
          29                 :  * of those above. If you wish to allow use of your version of this file only
          30                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
          31                 :  * use your version of this file under the terms of the MPL, indicate your
          32                 :  * decision by deleting the provisions above and replace them with the notice
          33                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
          34                 :  * the provisions above, a recipient may use your version of this file under
          35                 :  * the terms of any one of the MPL, the GPL or the LGPL.
          36                 :  *
          37                 :  * ***** END LICENSE BLOCK ***** */
          38                 :
          39                 : #ifndef pldhash_h___
          40                 : #define pldhash_h___
          41                 : /*
          42                 :  * Double hashing, a la Knuth 6.
          43                 :  *
          44                 :  * Try to keep this file in sync with js/src/jsdhash.h.
          45                 :  */
          46                 : #include "nscore.h"
          47                 :
          48                 : PR_BEGIN_EXTERN_C
          49                 :
          50                 : #if defined(__GNUC__) && defined(__i386__) && (__GNUC__ >= 3) && !defined(XP_OS2)
          51                 : #define PL_DHASH_FASTCALL __attribute__ ((regparm (3),stdcall))
          52                 : #elif defined(XP_WIN)
          53                 : #define PL_DHASH_FASTCALL __fastcall
          54                 : #else
          55                 : #define PL_DHASH_FASTCALL
          56                 : #endif
          57                 :
          58                 : #ifdef DEBUG_XXXbrendan
          59                 : #define PL_DHASHMETER 1
          60                 : #endif
          61                 :
          62                 : /* Table size limit, do not equal or exceed (see min&maxAlphaFrac, below). */
          63                 : #undef PL_DHASH_SIZE_LIMIT
          64                 : #define PL_DHASH_SIZE_LIMIT     PR_BIT(24)
          65                 :
          66                 : /* Minimum table size, or gross entry count (net is at most .75 loaded). */
          67                 : #ifndef PL_DHASH_MIN_SIZE
          68                 : #define PL_DHASH_MIN_SIZE 16
          69                 : #elif (PL_DHASH_MIN_SIZE & (PL_DHASH_MIN_SIZE - 1)) != 0
          70                 : #error "PL_DHASH_MIN_SIZE must be a power of two!"
          71                 : #endif
          72                 :
          73                 : /*
          74                 :  * Multiplicative hash uses an unsigned 32 bit integer and the golden ratio,
          75                 :  * expressed as a fixed-point 32-bit fraction.
          76                 :  */
          77                 : #define PL_DHASH_BITS           32
          78                 : #define PL_DHASH_GOLDEN_RATIO   0x9E3779B9U
          79                 :
          80                 : /* Primitive and forward-struct typedefs. */
          81                 : typedef PRUint32                PLDHashNumber;
          82                 : typedef struct PLDHashEntryHdr  PLDHashEntryHdr;
          83                 : typedef struct PLDHashEntryStub PLDHashEntryStub;
          84                 : typedef struct PLDHashTable     PLDHashTable;
          85                 : typedef struct PLDHashTableOps  PLDHashTableOps;
          86                 :
          87                 : /*
          88                 :  * Table entry header structure.
          89                 :  *
          90                 :  * In order to allow in-line allocation of key and value, we do not declare
          91                 :  * either here.  Instead, the API uses const void *key as a formal parameter.
          92                 :  * The key need not be stored in the entry; it may be part of the value, but
          93                 :  * need not be stored at all.
          94                 :  *
          95                 :  * Callback types are defined below and grouped into the PLDHashTableOps
          96                 :  * structure, for single static initialization per hash table sub-type.
          97                 :  *
          98                 :  * Each hash table sub-type should nest the PLDHashEntryHdr structure at the
          99                 :  * front of its particular entry type.  The keyHash member contains the result
         100                 :  * of multiplying the hash code returned from the hashKey callback (see below)
         101                 :  * by PL_DHASH_GOLDEN_RATIO, then constraining the result to avoid the magic 0
         102                 :  * and 1 values.  The stored keyHash value is table size invariant, and it is
         103                 :  * maintained automatically by PL_DHashTableOperate -- users should never set
         104                 :  * it, and its only uses should be via the entry macros below.
         105                 :  *
         106                 :  * The PL_DHASH_ENTRY_IS_LIVE macro tests whether entry is neither free nor
         107                 :  * removed.  An entry may be either busy or free; if busy, it may be live or
         108                 :  * removed.  Consumers of this API should not access members of entries that
         109                 :  * are not live.
         110                 :  *
         111                 :  * However, use PL_DHASH_ENTRY_IS_BUSY for faster liveness testing of entries
         112                 :  * returned by PL_DHashTableOperate, as PL_DHashTableOperate never returns a
         113                 :  * non-live, busy (i.e., removed) entry pointer to its caller.  See below for
         114                 :  * more details on PL_DHashTableOperate's calling rules.
         115                 :  */
         116        13296681 : struct PLDHashEntryHdr {
         117                 :     PLDHashNumber       keyHash;        /* every entry must begin like this */
         118                 : };
         119                 :
         120                 : #define PL_DHASH_ENTRY_IS_FREE(entry)   ((entry)->keyHash == 0)
         121                 : #define PL_DHASH_ENTRY_IS_BUSY(entry)   (!PL_DHASH_ENTRY_IS_FREE(entry))
         122                 : #define PL_DHASH_ENTRY_IS_LIVE(entry)   ((entry)->keyHash >= 2)
         123                 :
         124                 : /*
         125                 :  * A PLDHashTable is currently 8 words (without the PL_DHASHMETER overhead)
         126                 :  * on most architectures, and may be allocated on the stack or within another
         127                 :  * structure or class (see below for the Init and Finish functions to use).
         128                 :  *
         129                 :  * To decide whether to use double hashing vs. chaining, we need to develop a
         130                 :  * trade-off relation, as follows:
         131                 :  *
         132                 :  * Let alpha be the load factor, esize the entry size in words, count the
         133                 :  * entry count, and pow2 the power-of-two table size in entries.
         134                 :  *
         135                 :  *   (PLDHashTable overhead)    > (PLHashTable overhead)
         136                 :  *   (unused table entry space) > (malloc and .next overhead per entry) +
         137                 :  *                                (buckets overhead)
         138                 :  *   (1 - alpha) * esize * pow2 > 2 * count + pow2
         139                 :  *
         140                 :  * Notice that alpha is by definition (count / pow2):
         141                 :  *
         142                 :  *   (1 - alpha) * esize * pow2 > 2 * alpha * pow2 + pow2
         143                 :  *   (1 - alpha) * esize        > 2 * alpha + 1
         144                 :  *
         145                 :  *   esize > (1 + 2 * alpha) / (1 - alpha)
         146                 :  *
         147                 :  * This assumes both tables must keep keyHash, key, and value for each entry,
         148                 :  * where key and value point to separately allocated strings or structures.
         149                 :  * If key and value can be combined into one pointer, then the trade-off is:
         150                 :  *
         151                 :  *   esize > (1 + 3 * alpha) / (1 - alpha)
         152                 :  *
         153                 :  * If the entry value can be a subtype of PLDHashEntryHdr, rather than a type
         154                 :  * that must be allocated separately and referenced by an entry.value pointer
         155                 :  * member, and provided key's allocation can be fused with its entry's, then
         156                 :  * k (the words wasted per entry with chaining) is 4.
         157                 :  *
         158                 :  * To see these curves, feed gnuplot input like so:
         159                 :  *
         160                 :  *   gnuplot> f(x,k) = (1 + k * x) / (1 - x)
         161                 :  *   gnuplot> plot [0:.75] f(x,2), f(x,3), f(x,4)
         162                 :  *
         163                 :  * For k of 2 and a well-loaded table (alpha > .5), esize must be more than 4
         164                 :  * words for chaining to be more space-efficient than double hashing.
         165                 :  *
         166                 :  * Solving for alpha helps us decide when to shrink an underloaded table:
         167                 :  *
         168                 :  *   esize                     > (1 + k * alpha) / (1 - alpha)
         169                 :  *   esize - alpha * esize     > 1 + k * alpha
         170                 :  *   esize - 1                 > (k + esize) * alpha
         171                 :  *   (esize - 1) / (k + esize) > alpha
         172                 :  *
         173                 :  *   alpha < (esize - 1) / (esize + k)
         174                 :  *
         175                 :  * Therefore double hashing should keep alpha >= (esize - 1) / (esize + k),
         176                 :  * assuming esize is not too large (in which case, chaining should probably be
         177                 :  * used for any alpha).  For esize=2 and k=3, we want alpha >= .2; for esize=3
         178                 :  * and k=2, we want alpha >= .4.  For k=4, esize could be 6, and alpha >= .5
         179                 :  * would still obtain.  See the PL_DHASH_MIN_ALPHA macro further below.
         180                 :  *
         181                 :  * The current implementation uses a configurable lower bound on alpha, which
         182                 :  * defaults to .25, when deciding to shrink the table (while still respecting
         183                 :  * PL_DHASH_MIN_SIZE).
         184                 :  *
         185                 :  * Note a qualitative difference between chaining and double hashing: under
         186                 :  * chaining, entry addresses are stable across table shrinks and grows.  With
         187                 :  * double hashing, you can't safely hold an entry pointer and use it after an
         188                 :  * ADD or REMOVE operation, unless you sample table->generation before adding
         189                 :  * or removing, and compare the sample after, dereferencing the entry pointer
         190                 :  * only if table->generation has not changed.
         191                 :  *
         192                 :  * The moral of this story: there is no one-size-fits-all hash table scheme,
         193                 :  * but for small table entry size, and assuming entry address stability is not
         194                 :  * required, double hashing wins.
         195                 :  */
         196               2 : struct PLDHashTable {
         197                 :     const PLDHashTableOps *ops;         /* virtual operations, see below */
         198                 :     void                *data;          /* ops- and instance-specific data */
         199                 :     PRInt16             hashShift;      /* multiplicative hash shift */
         200                 :     PRUint8             maxAlphaFrac;   /* 8-bit fixed point max alpha */
         201                 :     PRUint8             minAlphaFrac;   /* 8-bit fixed point min alpha */
         202                 :     PRUint32            entrySize;      /* number of bytes in an entry */
         203                 :     PRUint32            entryCount;     /* number of entries in table */
         204                 :     PRUint32            removedCount;   /* removed entry sentinels in table */
         205                 :     PRUint32            generation;     /* entry storage generation number */
         206                 :     char                *entryStore;    /* entry storage */
         207                 : #ifdef PL_DHASHMETER
         208                 :     struct PLDHashStats {
         209                 :         PRUint32        searches;       /* total number of table searches */
         210                 :         PRUint32        steps;          /* hash chain links traversed */
         211                 :         PRUint32        hits;           /* searches that found key */
         212                 :         PRUint32        misses;         /* searches that didn't find key */
         213                 :         PRUint32        lookups;        /* number of PL_DHASH_LOOKUPs */
         214                 :         PRUint32        addMisses;      /* adds that miss, and do work */
         215                 :         PRUint32        addOverRemoved; /* adds that recycled a removed entry */
         216                 :         PRUint32        addHits;        /* adds that hit an existing entry */
         217                 :         PRUint32        addFailures;    /* out-of-memory during add growth */
         218                 :         PRUint32        removeHits;     /* removes that hit, and do work */
         219                 :         PRUint32        removeMisses;   /* useless removes that miss */
         220                 :         PRUint32        removeFrees;    /* removes that freed entry directly */
         221                 :         PRUint32        removeEnums;    /* removes done by Enumerate */
         222                 :         PRUint32        grows;          /* table expansions */
         223                 :         PRUint32        shrinks;        /* table contractions */
         224                 :         PRUint32        compresses;     /* table compressions */
         225                 :         PRUint32        enumShrinks;    /* contractions after Enumerate */
         226                 :     } stats;
         227                 : #endif
         228                 : };
         229                 :
         230                 : /*
         231                 :  * Size in entries (gross, not net of free and removed sentinels) for table.
         232                 :  * We store hashShift rather than sizeLog2 to optimize the collision-free case
         233                 :  * in SearchTable.
         234                 :  */
         235                 : #define PL_DHASH_TABLE_SIZE(table)  PR_BIT(PL_DHASH_BITS - (table)->hashShift)
         236                 :
         237                 : /*
         238                 :  * Table space at entryStore is allocated and freed using these callbacks.
         239                 :  * The allocator should return null on error only (not if called with nbytes
         240                 :  * equal to 0; but note that pldhash.c code will never call with 0 nbytes).
         241                 :  */
         242                 : typedef void *
         243                 : (* PLDHashAllocTable)(PLDHashTable *table, PRUint32 nbytes);
         244                 :
         245                 : typedef void
         246                 : (* PLDHashFreeTable) (PLDHashTable *table, void *ptr);
         247                 :
         248                 : /*
         249                 :  * Compute the hash code for a given key to be looked up, added, or removed
         250                 :  * from table.  A hash code may have any PLDHashNumber value.
         251                 :  */
         252                 : typedef PLDHashNumber
         253                 : (* PLDHashHashKey)   (PLDHashTable *table, const void *key);
         254                 :
         255                 : /*
         256                 :  * Compare the key identifying entry in table with the provided key parameter.
         257                 :  * Return true if keys match, false otherwise.
         258                 :  */
         259                 : typedef bool
         260                 : (* PLDHashMatchEntry)(PLDHashTable *table, const PLDHashEntryHdr *entry,
         261                 :                       const void *key);
         262                 :
         263                 : /*
         264                 :  * Copy the data starting at from to the new entry storage at to.  Do not add
         265                 :  * reference counts for any strong references in the entry, however, as this
         266                 :  * is a "move" operation: the old entry storage at from will be freed without
         267                 :  * any reference-decrementing callback shortly.
         268                 :  */
         269                 : typedef void
         270                 : (* PLDHashMoveEntry)(PLDHashTable *table, const PLDHashEntryHdr *from,
         271                 :                      PLDHashEntryHdr *to);
         272                 :
         273                 : /*
         274                 :  * Clear the entry and drop any strong references it holds.  This callback is
         275                 :  * invoked during a PL_DHASH_REMOVE operation (see below for operation codes),
         276                 :  * but only if the given key is found in the table.
         277                 :  */
         278                 : typedef void
         279                 : (* PLDHashClearEntry)(PLDHashTable *table, PLDHashEntryHdr *entry);
         280                 :
         281                 : /*
         282                 :  * Called when a table (whether allocated dynamically by itself, or nested in
         283                 :  * a larger structure, or allocated on the stack) is finished.  This callback
         284                 :  * allows table->ops-specific code to finalize table->data.
         285                 :  */
         286                 : typedef void
         287                 : (* PLDHashFinalize)  (PLDHashTable *table);
         288                 :
         289                 : /*
         290                 :  * Initialize a new entry, apart from keyHash.  This function is called when
         291                 :  * PL_DHashTableOperate's PL_DHASH_ADD case finds no existing entry for the
         292                 :  * given key, and must add a new one.  At that point, entry->keyHash is not
         293                 :  * set yet, to avoid claiming the last free entry in a severely overloaded
         294                 :  * table.
         295                 :  */
         296                 : typedef bool
         297                 : (* PLDHashInitEntry)(PLDHashTable *table, PLDHashEntryHdr *entry,
         298                 :                      const void *key);
         299                 :
         300                 : /*
         301                 :  * Finally, the "vtable" structure for PLDHashTable.  The first eight hooks
         302                 :  * must be provided by implementations; they're called unconditionally by the
         303                 :  * generic pldhash.c code.  Hooks after these may be null.
         304                 :  *
         305                 :  * Summary of allocation-related hook usage with C++ placement new emphasis:
         306                 :  *  allocTable          Allocate raw bytes with malloc, no ctors run.
         307                 :  *  freeTable           Free raw bytes with free, no dtors run.
         308                 :  *  initEntry           Call placement new using default key-based ctor.
         309                 :  *                      Return true on success, false on error.
         310                 :  *  moveEntry           Call placement new using copy ctor, run dtor on old
         311                 :  *                      entry storage.
         312                 :  *  clearEntry          Run dtor on entry.
         313                 :  *  finalize            Stub unless table->data was initialized and needs to
         314                 :  *                      be finalized.
         315                 :  *
         316                 :  * Note the reason why initEntry is optional: the default hooks (stubs) clear
         317                 :  * entry storage:  On successful PL_DHashTableOperate(tbl, key, PL_DHASH_ADD),
         318                 :  * the returned entry pointer addresses an entry struct whose keyHash member
         319                 :  * has been set non-zero, but all other entry members are still clear (null).
         320                 :  * PL_DHASH_ADD callers can test such members to see whether the entry was
         321                 :  * newly created by the PL_DHASH_ADD call that just succeeded.  If placement
         322                 :  * new or similar initialization is required, define an initEntry hook.  Of
         323                 :  * course, the clearEntry hook must zero or null appropriately.
         324                 :  *
         325                 :  * XXX assumes 0 is null for pointer types.
         326                 :  */
         327                 : struct PLDHashTableOps {
         328                 :     /* Mandatory hooks.  All implementations must provide these. */
         329                 :     PLDHashAllocTable   allocTable;
         330                 :     PLDHashFreeTable    freeTable;
         331                 :     PLDHashHashKey      hashKey;
         332                 :     PLDHashMatchEntry   matchEntry;
         333                 :     PLDHashMoveEntry    moveEntry;
         334                 :     PLDHashClearEntry   clearEntry;
         335                 :     PLDHashFinalize     finalize;
         336                 :
         337                 :     /* Optional hooks start here.  If null, these are not called. */
         338                 :     PLDHashInitEntry    initEntry;
         339                 : };
         340                 :
         341                 : /*
         342                 :  * Default implementations for the above ops.
         343                 :  */
         344                 : NS_COM_GLUE void *
         345                 : PL_DHashAllocTable(PLDHashTable *table, PRUint32 nbytes);
         346                 :
         347                 : NS_COM_GLUE void
         348                 : PL_DHashFreeTable(PLDHashTable *table, void *ptr);
         349                 :
         350                 : NS_COM_GLUE PLDHashNumber
         351                 : PL_DHashStringKey(PLDHashTable *table, const void *key);
         352                 :
         353                 : /* A minimal entry contains a keyHash header and a void key pointer. */
         354                 : struct PLDHashEntryStub {
         355                 :     PLDHashEntryHdr hdr;
         356                 :     const void      *key;
         357                 : };
         358                 :
         359                 : NS_COM_GLUE PLDHashNumber
         360                 : PL_DHashVoidPtrKeyStub(PLDHashTable *table, const void *key);
         361                 :
         362                 : NS_COM_GLUE bool
         363                 : PL_DHashMatchEntryStub(PLDHashTable *table,
         364                 :                        const PLDHashEntryHdr *entry,
         365                 :                        const void *key);
         366                 :
         367                 : NS_COM_GLUE bool
         368                 : PL_DHashMatchStringKey(PLDHashTable *table,
         369                 :                        const PLDHashEntryHdr *entry,
         370                 :                        const void *key);
         371                 :
         372                 : NS_COM_GLUE void
         373                 : PL_DHashMoveEntryStub(PLDHashTable *table,
         374                 :                       const PLDHashEntryHdr *from,
         375                 :                       PLDHashEntryHdr *to);
         376                 :
         377                 : NS_COM_GLUE void
         378                 : PL_DHashClearEntryStub(PLDHashTable *table, PLDHashEntryHdr *entry);
         379                 :
         380                 : NS_COM_GLUE void
         381                 : PL_DHashFreeStringKey(PLDHashTable *table, PLDHashEntryHdr *entry);
         382                 :
         383                 : NS_COM_GLUE void
         384                 : PL_DHashFinalizeStub(PLDHashTable *table);
         385                 :
         386                 : /*
         387                 :  * If you use PLDHashEntryStub or a subclass of it as your entry struct, and
         388                 :  * if your entries move via memcpy and clear via memset(0), you can use these
         389                 :  * stub operations.
         390                 :  */
         391                 : NS_COM_GLUE const PLDHashTableOps *
         392                 : PL_DHashGetStubOps(void);
         393                 :
         394                 : /*
         395                 :  * Dynamically allocate a new PLDHashTable using malloc, initialize it using
         396                 :  * PL_DHashTableInit, and return its address.  Return null on malloc failure.
         397                 :  * Note that the entry storage at table->entryStore will be allocated using
         398                 :  * the ops->allocTable callback.
         399                 :  */
         400                 : NS_COM_GLUE PLDHashTable *
         401                 : PL_NewDHashTable(const PLDHashTableOps *ops, void *data, PRUint32 entrySize,
         402                 :                  PRUint32 capacity);
         403                 :
         404                 : /*
         405                 :  * Finalize table's data, free its entry storage (via table->ops->freeTable),
         406                 :  * and return the memory starting at table to the malloc heap.
         407                 :  */
         408                 : NS_COM_GLUE void
         409                 : PL_DHashTableDestroy(PLDHashTable *table);
         410                 :
         411                 : /*
         412                 :  * Initialize table with ops, data, entrySize, and capacity.  Capacity is a
         413                 :  * guess for the smallest table size at which the table will usually be less
         414                 :  * than 75% loaded (the table will grow or shrink as needed; capacity serves
         415                 :  * only to avoid inevitable early growth from PL_DHASH_MIN_SIZE).
         416                 :  */
         417                 : NS_COM_GLUE bool
         418                 : PL_DHashTableInit(PLDHashTable *table, const PLDHashTableOps *ops, void *data,
         419                 :                   PRUint32 entrySize, PRUint32 capacity);
         420                 :
         421                 : /*
         422                 :  * Set maximum and minimum alpha for table.  The defaults are 0.75 and .25.
         423                 :  * maxAlpha must be in [0.5, 0.9375] for the default PL_DHASH_MIN_SIZE; or if
         424                 :  * MinSize=PL_DHASH_MIN_SIZE <= 256, in [0.5, (float)(MinSize-1)/MinSize]; or
         425                 :  * else in [0.5, 255.0/256].  minAlpha must be in [0, maxAlpha / 2), so that
         426                 :  * we don't shrink on the very next remove after growing a table upon adding
         427                 :  * an entry that brings entryCount past maxAlpha * tableSize.
         428                 :  */
         429                 : NS_COM_GLUE void
         430                 : PL_DHashTableSetAlphaBounds(PLDHashTable *table,
         431                 :                             float maxAlpha,
         432                 :                             float minAlpha);
         433                 :
         434                 : /*
         435                 :  * Call this macro with k, the number of pointer-sized words wasted per entry
         436                 :  * under chaining, to compute the minimum alpha at which double hashing still
         437                 :  * beats chaining.
         438                 :  */
         439                 : #define PL_DHASH_MIN_ALPHA(table, k)                                          \
         440                 :     ((float)((table)->entrySize / sizeof(void *) - 1)                         \
         441                 :      / ((table)->entrySize / sizeof(void *) + (k)))
         442                 :
         443                 : /*
         444                 :  * Default max/min alpha, and macros to compute the value for the |capacity|
         445                 :  * parameter to PL_NewDHashTable and PL_DHashTableInit, given default or any
         446                 :  * max alpha, such that adding entryCount entries right after initializing the
         447                 :  * table will not require a reallocation (so PL_DHASH_ADD can't fail for those
         448                 :  * PL_DHashTableOperate calls).
         449                 :  *
         450                 :  * NB: PL_DHASH_CAP is a helper macro meant for use only in PL_DHASH_CAPACITY.
         451                 :  * Don't use it directly!
         452                 :  */
         453                 : #define PL_DHASH_DEFAULT_MAX_ALPHA 0.75
         454                 : #define PL_DHASH_DEFAULT_MIN_ALPHA 0.25
         455                 :
         456                 : #define PL_DHASH_CAP(entryCount, maxAlpha)                                    \
         457                 :     ((PRUint32)((double)(entryCount) / (maxAlpha)))
         458                 :
         459                 : #define PL_DHASH_CAPACITY(entryCount, maxAlpha)                               \
         460                 :     (PL_DHASH_CAP(entryCount, maxAlpha) +                                     \
         461                 :      (((PL_DHASH_CAP(entryCount, maxAlpha) * (PRUint8)(0x100 * (maxAlpha)))     \
         462                 :        >> 8) < (entryCount)))
         463                 :
         464                 : #define PL_DHASH_DEFAULT_CAPACITY(entryCount)                                 \
         465                 :     PL_DHASH_CAPACITY(entryCount, PL_DHASH_DEFAULT_MAX_ALPHA)
         466                 :
         467                 : /*
         468                 :  * Finalize table's data, free its entry storage using table->ops->freeTable,
         469                 :  * and leave its members unchanged from their last live values (which leaves
         470                 :  * pointers dangling).  If you want to burn cycles clearing table, it's up to
         471                 :  * your code to call memset.
         472                 :  */
         473                 : NS_COM_GLUE void
         474                 : PL_DHashTableFinish(PLDHashTable *table);
         475                 :
         476                 : /*
         477                 :  * To consolidate keyHash computation and table grow/shrink code, we use a
         478                 :  * single entry point for lookup, add, and remove operations.  The operation
         479                 :  * codes are declared here, along with codes returned by PLDHashEnumerator
         480                 :  * functions, which control PL_DHashTableEnumerate's behavior.
         481                 :  */
         482                 : typedef enum PLDHashOperator {
         483                 :     PL_DHASH_LOOKUP = 0,        /* lookup entry */
         484                 :     PL_DHASH_ADD = 1,           /* add entry */
         485                 :     PL_DHASH_REMOVE = 2,        /* remove entry, or enumerator says remove */
         486                 :     PL_DHASH_NEXT = 0,          /* enumerator says continue */
         487                 :     PL_DHASH_STOP = 1           /* enumerator says stop */
         488                 : } PLDHashOperator;
         489                 :
         490                 : /*
         491                 :  * To lookup a key in table, call:
         492                 :  *
         493                 :  *  entry = PL_DHashTableOperate(table, key, PL_DHASH_LOOKUP);
         494                 :  *
         495                 :  * If PL_DHASH_ENTRY_IS_BUSY(entry) is true, key was found and it identifies
         496                 :  * entry.  If PL_DHASH_ENTRY_IS_FREE(entry) is true, key was not found.
         497                 :  *
         498                 :  * To add an entry identified by key to table, call:
         499                 :  *
         500                 :  *  entry = PL_DHashTableOperate(table, key, PL_DHASH_ADD);
         501                 :  *
         502                 :  * If entry is null upon return, then either the table is severely overloaded,
         503                 :  * and memory can't be allocated for entry storage via table->ops->allocTable;
         504                 :  * Or if table->ops->initEntry is non-null, the table->ops->initEntry op may
         505                 :  * have returned false.
         506                 :  *
         507                 :  * Otherwise, entry->keyHash has been set so that PL_DHASH_ENTRY_IS_BUSY(entry)
         508                 :  * is true, and it is up to the caller to initialize the key and value parts
         509                 :  * of the entry sub-type, if they have not been set already (i.e. if entry was
         510                 :  * not already in the table, and if the optional initEntry hook was not used).
         511                 :  *
         512                 :  * To remove an entry identified by key from table, call:
         513                 :  *
         514                 :  *  (void) PL_DHashTableOperate(table, key, PL_DHASH_REMOVE);
         515                 :  *
         516                 :  * If key's entry is found, it is cleared (via table->ops->clearEntry) and
         517                 :  * the entry is marked so that PL_DHASH_ENTRY_IS_FREE(entry).  This operation
         518                 :  * returns null unconditionally; you should ignore its return value.
         519                 :  */
         520                 : NS_COM_GLUE PLDHashEntryHdr * PL_DHASH_FASTCALL
         521                 : PL_DHashTableOperate(PLDHashTable *table, const void *key, PLDHashOperator op);
         522                 :
         523                 : /*
         524                 :  * Remove an entry already accessed via LOOKUP or ADD.
         525                 :  *
         526                 :  * NB: this is a "raw" or low-level routine, intended to be used only where
         527                 :  * the inefficiency of a full PL_DHashTableOperate (which rehashes in order
         528                 :  * to find the entry given its key) is not tolerable.  This function does not
         529                 :  * shrink the table if it is underloaded.  It does not update stats #ifdef
         530                 :  * PL_DHASHMETER, either.
         531                 :  */
         532                 : NS_COM_GLUE void
         533                 : PL_DHashTableRawRemove(PLDHashTable *table, PLDHashEntryHdr *entry);
         534                 :
         535                 : /*
         536                 :  * Enumerate entries in table using etor:
         537                 :  *
         538                 :  *   count = PL_DHashTableEnumerate(table, etor, arg);
         539                 :  *
         540                 :  * PL_DHashTableEnumerate calls etor like so:
         541                 :  *
         542                 :  *   op = etor(table, entry, number, arg);
         543                 :  *
         544                 :  * where number is a zero-based ordinal assigned to live entries according to
         545                 :  * their order in table->entryStore.
         546                 :  *
         547                 :  * The return value, op, is treated as a set of flags.  If op is PL_DHASH_NEXT,
         548                 :  * then continue enumerating.  If op contains PL_DHASH_REMOVE, then clear (via
         549                 :  * table->ops->clearEntry) and free entry.  Then we check whether op contains
         550                 :  * PL_DHASH_STOP; if so, stop enumerating and return the number of live entries
         551                 :  * that were enumerated so far.  Return the total number of live entries when
         552                 :  * enumeration completes normally.
         553                 :  *
         554                 :  * If etor calls PL_DHashTableOperate on table with op != PL_DHASH_LOOKUP, it
         555                 :  * must return PL_DHASH_STOP; otherwise undefined behavior results.
         556                 :  *
         557                 :  * If any enumerator returns PL_DHASH_REMOVE, table->entryStore may be shrunk
         558                 :  * or compressed after enumeration, but before PL_DHashTableEnumerate returns.
         559                 :  * Such an enumerator therefore can't safely set aside entry pointers, but an
         560                 :  * enumerator that never returns PL_DHASH_REMOVE can set pointers to entries
         561                 :  * aside, e.g., to avoid copying live entries into an array of the entry type.
         562                 :  * Copying entry pointers is cheaper, and safe so long as the caller of such a
         563                 :  * "stable" Enumerate doesn't use the set-aside pointers after any call either
         564                 :  * to PL_DHashTableOperate, or to an "unstable" form of Enumerate, which might
         565                 :  * grow or shrink entryStore.
         566                 :  *
         567                 :  * If your enumerator wants to remove certain entries, but set aside pointers
         568                 :  * to other entries that it retains, it can use PL_DHashTableRawRemove on the
         569                 :  * entries to be removed, returning PL_DHASH_NEXT to skip them.  Likewise, if
         570                 :  * you want to remove entries, but for some reason you do not want entryStore
         571                 :  * to be shrunk or compressed, you can call PL_DHashTableRawRemove safely on
         572                 :  * the entry being enumerated, rather than returning PL_DHASH_REMOVE.
         573                 :  */
         574                 : typedef PLDHashOperator
         575                 : (* PLDHashEnumerator)(PLDHashTable *table, PLDHashEntryHdr *hdr, PRUint32 number,
         576                 :                       void *arg);
         577                 :
         578                 : NS_COM_GLUE PRUint32
         579                 : PL_DHashTableEnumerate(PLDHashTable *table, PLDHashEnumerator etor, void *arg);
         580                 :
         581                 : typedef size_t
         582                 : (* PLDHashSizeOfEntryExcludingThisFun)(PLDHashEntryHdr *hdr,
         583                 :                                        nsMallocSizeOfFun mallocSizeOf,
         584                 :                                        void *arg);
         585                 :
         586                 : /**
         587                 :  * Measure the size of the table's entry storage, and if
         588                 :  * |sizeOfEntryExcludingThis| is non-NULL, measure the size of things pointed
         589                 :  * to by entries.  Doesn't measure |ops| because it's often shared between
         590                 :  * tables, nor |data| because it's opaque.
         591                 :  */
         592                 : NS_COM_GLUE size_t
         593                 : PL_DHashTableSizeOfExcludingThis(const PLDHashTable *table,
         594                 :                                  PLDHashSizeOfEntryExcludingThisFun sizeOfEntryExcludingThis,
         595                 :                                  nsMallocSizeOfFun mallocSizeOf,
         596                 :                                  void *arg = NULL);
         597                 :
         598                 : /**
         599                 :  * Like PL_DHashTableSizeOfExcludingThis, but includes sizeof(*this).
         600                 :  */
         601                 : NS_COM_GLUE size_t
         602                 : PL_DHashTableSizeOfIncludingThis(const PLDHashTable *table,
         603                 :                                  PLDHashSizeOfEntryExcludingThisFun sizeOfEntryExcludingThis,
         604                 :                                  nsMallocSizeOfFun mallocSizeOf,
         605                 :                                  void *arg = NULL);
         606                 :
         607                 : #ifdef DEBUG
         608                 : /**
         609                 :  * Mark a table as immutable for the remainder of its lifetime.  This
         610                 :  * changes the implementation from ASSERTing one set of invariants to
         611                 :  * ASSERTing a different set.
         612                 :  *
         613                 :  * When a table is NOT marked as immutable, the table implementation
         614                 :  * asserts that the table is not mutated from its own callbacks.  It
         615                 :  * assumes the caller protects the table from being accessed on multiple
         616                 :  * threads simultaneously.
         617                 :  *
         618                 :  * When the table is marked as immutable, the re-entry assertions will
         619                 :  * no longer trigger erroneously due to multi-threaded access.  Instead,
         620                 :  * mutations will cause assertions.
         621                 :  */
         622                 : NS_COM_GLUE void
         623                 : PL_DHashMarkTableImmutable(PLDHashTable *table);
         624                 : #endif
         625                 :
         626                 : #ifdef PL_DHASHMETER
         627                 : #include <stdio.h>
         628                 :
         629                 : NS_COM_GLUE void
         630                 : PL_DHashTableDumpMeter(PLDHashTable *table, PLDHashEnumerator dump, FILE *fp);
         631                 : #endif
         632                 :
         633                 : PR_END_EXTERN_C
         634                 :
         635                 : #endif /* pldhash_h___ */

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