/gecko_api/include/pldhash.h
C Header | 593 lines | 183 code | 53 blank | 357 comment | 5 complexity | 50218bc8f7e62095be27ad6da6f87f3f MD5 | raw file
- /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
- /* ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is Mozilla JavaScript code.
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1999-2001
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- * Brendan Eich <brendan@mozilla.org> (Original Author)
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either of the GNU General Public License Version 2 or later (the "GPL"),
- * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
- #ifndef pldhash_h___
- #define pldhash_h___
- /*
- * Double hashing, a la Knuth 6.
- * GENERATED BY js/src/plify_jsdhash.sed -- DO NOT EDIT!!!
- */
- #include "nscore.h"
- PR_BEGIN_EXTERN_C
- #if defined(__GNUC__) && defined(__i386__) && (__GNUC__ >= 3) && !defined(XP_OS2)
- #define PL_DHASH_FASTCALL __attribute__ ((regparm (3),stdcall))
- #elif defined(XP_WIN)
- #define PL_DHASH_FASTCALL __fastcall
- #else
- #define PL_DHASH_FASTCALL
- #endif
- #ifdef DEBUG_XXXbrendan
- #define PL_DHASHMETER 1
- #endif
- /* Table size limit, do not equal or exceed (see min&maxAlphaFrac, below). */
- #undef PL_DHASH_SIZE_LIMIT
- #define PL_DHASH_SIZE_LIMIT PR_BIT(24)
- /* Minimum table size, or gross entry count (net is at most .75 loaded). */
- #ifndef PL_DHASH_MIN_SIZE
- #define PL_DHASH_MIN_SIZE 16
- #elif (PL_DHASH_MIN_SIZE & (PL_DHASH_MIN_SIZE - 1)) != 0
- #error "PL_DHASH_MIN_SIZE must be a power of two!"
- #endif
- /*
- * Multiplicative hash uses an unsigned 32 bit integer and the golden ratio,
- * expressed as a fixed-point 32-bit fraction.
- */
- #define PL_DHASH_BITS 32
- #define PL_DHASH_GOLDEN_RATIO 0x9E3779B9U
- /* Primitive and forward-struct typedefs. */
- typedef PRUint32 PLDHashNumber;
- typedef struct PLDHashEntryHdr PLDHashEntryHdr;
- typedef struct PLDHashEntryStub PLDHashEntryStub;
- typedef struct PLDHashTable PLDHashTable;
- typedef struct PLDHashTableOps PLDHashTableOps;
- /*
- * Table entry header structure.
- *
- * In order to allow in-line allocation of key and value, we do not declare
- * either here. Instead, the API uses const void *key as a formal parameter.
- * The key need not be stored in the entry; it may be part of the value, but
- * need not be stored at all.
- *
- * Callback types are defined below and grouped into the PLDHashTableOps
- * structure, for single static initialization per hash table sub-type.
- *
- * Each hash table sub-type should nest the PLDHashEntryHdr structure at the
- * front of its particular entry type. The keyHash member contains the result
- * of multiplying the hash code returned from the hashKey callback (see below)
- * by PL_DHASH_GOLDEN_RATIO, then constraining the result to avoid the magic 0
- * and 1 values. The stored keyHash value is table size invariant, and it is
- * maintained automatically by PL_DHashTableOperate -- users should never set
- * it, and its only uses should be via the entry macros below.
- *
- * The PL_DHASH_ENTRY_IS_LIVE macro tests whether entry is neither free nor
- * removed. An entry may be either busy or free; if busy, it may be live or
- * removed. Consumers of this API should not access members of entries that
- * are not live.
- *
- * However, use PL_DHASH_ENTRY_IS_BUSY for faster liveness testing of entries
- * returned by PL_DHashTableOperate, as PL_DHashTableOperate never returns a
- * non-live, busy (i.e., removed) entry pointer to its caller. See below for
- * more details on PL_DHashTableOperate's calling rules.
- */
- struct PLDHashEntryHdr {
- PLDHashNumber keyHash; /* every entry must begin like this */
- };
- #define PL_DHASH_ENTRY_IS_FREE(entry) ((entry)->keyHash == 0)
- #define PL_DHASH_ENTRY_IS_BUSY(entry) (!PL_DHASH_ENTRY_IS_FREE(entry))
- #define PL_DHASH_ENTRY_IS_LIVE(entry) ((entry)->keyHash >= 2)
- /*
- * A PLDHashTable is currently 8 words (without the PL_DHASHMETER overhead)
- * on most architectures, and may be allocated on the stack or within another
- * structure or class (see below for the Init and Finish functions to use).
- *
- * To decide whether to use double hashing vs. chaining, we need to develop a
- * trade-off relation, as follows:
- *
- * Let alpha be the load factor, esize the entry size in words, count the
- * entry count, and pow2 the power-of-two table size in entries.
- *
- * (PLDHashTable overhead) > (PLHashTable overhead)
- * (unused table entry space) > (malloc and .next overhead per entry) +
- * (buckets overhead)
- * (1 - alpha) * esize * pow2 > 2 * count + pow2
- *
- * Notice that alpha is by definition (count / pow2):
- *
- * (1 - alpha) * esize * pow2 > 2 * alpha * pow2 + pow2
- * (1 - alpha) * esize > 2 * alpha + 1
- *
- * esize > (1 + 2 * alpha) / (1 - alpha)
- *
- * This assumes both tables must keep keyHash, key, and value for each entry,
- * where key and value point to separately allocated strings or structures.
- * If key and value can be combined into one pointer, then the trade-off is:
- *
- * esize > (1 + 3 * alpha) / (1 - alpha)
- *
- * If the entry value can be a subtype of PLDHashEntryHdr, rather than a type
- * that must be allocated separately and referenced by an entry.value pointer
- * member, and provided key's allocation can be fused with its entry's, then
- * k (the words wasted per entry with chaining) is 4.
- *
- * To see these curves, feed gnuplot input like so:
- *
- * gnuplot> f(x,k) = (1 + k * x) / (1 - x)
- * gnuplot> plot [0:.75] f(x,2), f(x,3), f(x,4)
- *
- * For k of 2 and a well-loaded table (alpha > .5), esize must be more than 4
- * words for chaining to be more space-efficient than double hashing.
- *
- * Solving for alpha helps us decide when to shrink an underloaded table:
- *
- * esize > (1 + k * alpha) / (1 - alpha)
- * esize - alpha * esize > 1 + k * alpha
- * esize - 1 > (k + esize) * alpha
- * (esize - 1) / (k + esize) > alpha
- *
- * alpha < (esize - 1) / (esize + k)
- *
- * Therefore double hashing should keep alpha >= (esize - 1) / (esize + k),
- * assuming esize is not too large (in which case, chaining should probably be
- * used for any alpha). For esize=2 and k=3, we want alpha >= .2; for esize=3
- * and k=2, we want alpha >= .4. For k=4, esize could be 6, and alpha >= .5
- * would still obtain. See the PL_DHASH_MIN_ALPHA macro further below.
- *
- * The current implementation uses a configurable lower bound on alpha, which
- * defaults to .25, when deciding to shrink the table (while still respecting
- * PL_DHASH_MIN_SIZE).
- *
- * Note a qualitative difference between chaining and double hashing: under
- * chaining, entry addresses are stable across table shrinks and grows. With
- * double hashing, you can't safely hold an entry pointer and use it after an
- * ADD or REMOVE operation, unless you sample table->generation before adding
- * or removing, and compare the sample after, dereferencing the entry pointer
- * only if table->generation has not changed.
- *
- * The moral of this story: there is no one-size-fits-all hash table scheme,
- * but for small table entry size, and assuming entry address stability is not
- * required, double hashing wins.
- */
- struct PLDHashTable {
- const PLDHashTableOps *ops; /* virtual operations, see below */
- void *data; /* ops- and instance-specific data */
- PRInt16 hashShift; /* multiplicative hash shift */
- uint8 maxAlphaFrac; /* 8-bit fixed point max alpha */
- uint8 minAlphaFrac; /* 8-bit fixed point min alpha */
- PRUint32 entrySize; /* number of bytes in an entry */
- PRUint32 entryCount; /* number of entries in table */
- PRUint32 removedCount; /* removed entry sentinels in table */
- PRUint32 generation; /* entry storage generation number */
- char *entryStore; /* entry storage */
- #ifdef PL_DHASHMETER
- struct PLDHashStats {
- PRUint32 searches; /* total number of table searches */
- PRUint32 steps; /* hash chain links traversed */
- PRUint32 hits; /* searches that found key */
- PRUint32 misses; /* searches that didn't find key */
- PRUint32 lookups; /* number of PL_DHASH_LOOKUPs */
- PRUint32 addMisses; /* adds that miss, and do work */
- PRUint32 addOverRemoved; /* adds that recycled a removed entry */
- PRUint32 addHits; /* adds that hit an existing entry */
- PRUint32 addFailures; /* out-of-memory during add growth */
- PRUint32 removeHits; /* removes that hit, and do work */
- PRUint32 removeMisses; /* useless removes that miss */
- PRUint32 removeFrees; /* removes that freed entry directly */
- PRUint32 removeEnums; /* removes done by Enumerate */
- PRUint32 grows; /* table expansions */
- PRUint32 shrinks; /* table contractions */
- PRUint32 compresses; /* table compressions */
- PRUint32 enumShrinks; /* contractions after Enumerate */
- } stats;
- #endif
- };
- /*
- * Size in entries (gross, not net of free and removed sentinels) for table.
- * We store hashShift rather than sizeLog2 to optimize the collision-free case
- * in SearchTable.
- */
- #define PL_DHASH_TABLE_SIZE(table) PR_BIT(PL_DHASH_BITS - (table)->hashShift)
- /*
- * Table space at entryStore is allocated and freed using these callbacks.
- * The allocator should return null on error only (not if called with nbytes
- * equal to 0; but note that pldhash.c code will never call with 0 nbytes).
- */
- typedef void *
- (* PR_CALLBACK PLDHashAllocTable)(PLDHashTable *table, PRUint32 nbytes);
- typedef void
- (* PR_CALLBACK PLDHashFreeTable) (PLDHashTable *table, void *ptr);
- /*
- * Compute the hash code for a given key to be looked up, added, or removed
- * from table. A hash code may have any PLDHashNumber value.
- */
- typedef PLDHashNumber
- (* PR_CALLBACK PLDHashHashKey) (PLDHashTable *table, const void *key);
- /*
- * Compare the key identifying entry in table with the provided key parameter.
- * Return PR_TRUE if keys match, PR_FALSE otherwise.
- */
- typedef PRBool
- (* PR_CALLBACK PLDHashMatchEntry)(PLDHashTable *table,
- const PLDHashEntryHdr *entry,
- const void *key);
- /*
- * Copy the data starting at from to the new entry storage at to. Do not add
- * reference counts for any strong references in the entry, however, as this
- * is a "move" operation: the old entry storage at from will be freed without
- * any reference-decrementing callback shortly.
- */
- typedef void
- (* PR_CALLBACK PLDHashMoveEntry)(PLDHashTable *table,
- const PLDHashEntryHdr *from,
- PLDHashEntryHdr *to);
- /*
- * Clear the entry and drop any strong references it holds. This callback is
- * invoked during a PL_DHASH_REMOVE operation (see below for operation codes),
- * but only if the given key is found in the table.
- */
- typedef void
- (* PR_CALLBACK PLDHashClearEntry)(PLDHashTable *table,
- PLDHashEntryHdr *entry);
- /*
- * Called when a table (whether allocated dynamically by itself, or nested in
- * a larger structure, or allocated on the stack) is finished. This callback
- * allows table->ops-specific code to finalize table->data.
- */
- typedef void
- (* PR_CALLBACK PLDHashFinalize) (PLDHashTable *table);
- /*
- * Initialize a new entry, apart from keyHash. This function is called when
- * PL_DHashTableOperate's PL_DHASH_ADD case finds no existing entry for the
- * given key, and must add a new one. At that point, entry->keyHash is not
- * set yet, to avoid claiming the last free entry in a severely overloaded
- * table.
- */
- typedef PRBool
- (* PR_CALLBACK PLDHashInitEntry)(PLDHashTable *table,
- PLDHashEntryHdr *entry,
- const void *key);
- /*
- * Finally, the "vtable" structure for PLDHashTable. The first eight hooks
- * must be provided by implementations; they're called unconditionally by the
- * generic pldhash.c code. Hooks after these may be null.
- *
- * Summary of allocation-related hook usage with C++ placement new emphasis:
- * allocTable Allocate raw bytes with malloc, no ctors run.
- * freeTable Free raw bytes with free, no dtors run.
- * initEntry Call placement new using default key-based ctor.
- * Return PR_TRUE on success, PR_FALSE on error.
- * moveEntry Call placement new using copy ctor, run dtor on old
- * entry storage.
- * clearEntry Run dtor on entry.
- * finalize Stub unless table->data was initialized and needs to
- * be finalized.
- *
- * Note the reason why initEntry is optional: the default hooks (stubs) clear
- * entry storage: On successful PL_DHashTableOperate(tbl, key, PL_DHASH_ADD),
- * the returned entry pointer addresses an entry struct whose keyHash member
- * has been set non-zero, but all other entry members are still clear (null).
- * PL_DHASH_ADD callers can test such members to see whether the entry was
- * newly created by the PL_DHASH_ADD call that just succeeded. If placement
- * new or similar initialization is required, define an initEntry hook. Of
- * course, the clearEntry hook must zero or null appropriately.
- *
- * XXX assumes 0 is null for pointer types.
- */
- struct PLDHashTableOps {
- /* Mandatory hooks. All implementations must provide these. */
- PLDHashAllocTable allocTable;
- PLDHashFreeTable freeTable;
- PLDHashHashKey hashKey;
- PLDHashMatchEntry matchEntry;
- PLDHashMoveEntry moveEntry;
- PLDHashClearEntry clearEntry;
- PLDHashFinalize finalize;
- /* Optional hooks start here. If null, these are not called. */
- PLDHashInitEntry initEntry;
- };
- /*
- * Default implementations for the above ops.
- */
- NS_COM_GLUE void *
- PL_DHashAllocTable(PLDHashTable *table, PRUint32 nbytes);
- NS_COM_GLUE void
- PL_DHashFreeTable(PLDHashTable *table, void *ptr);
- NS_COM_GLUE PLDHashNumber
- PL_DHashStringKey(PLDHashTable *table, const void *key);
- /* A minimal entry contains a keyHash header and a void key pointer. */
- struct PLDHashEntryStub {
- PLDHashEntryHdr hdr;
- const void *key;
- };
- NS_COM_GLUE PLDHashNumber
- PL_DHashVoidPtrKeyStub(PLDHashTable *table, const void *key);
- NS_COM_GLUE PRBool
- PL_DHashMatchEntryStub(PLDHashTable *table,
- const PLDHashEntryHdr *entry,
- const void *key);
- NS_COM_GLUE PRBool
- PL_DHashMatchStringKey(PLDHashTable *table,
- const PLDHashEntryHdr *entry,
- const void *key);
- NS_COM_GLUE void
- PL_DHashMoveEntryStub(PLDHashTable *table,
- const PLDHashEntryHdr *from,
- PLDHashEntryHdr *to);
- NS_COM_GLUE void
- PL_DHashClearEntryStub(PLDHashTable *table, PLDHashEntryHdr *entry);
- NS_COM_GLUE void
- PL_DHashFreeStringKey(PLDHashTable *table, PLDHashEntryHdr *entry);
- NS_COM_GLUE void
- PL_DHashFinalizeStub(PLDHashTable *table);
- /*
- * If you use PLDHashEntryStub or a subclass of it as your entry struct, and
- * if your entries move via memcpy and clear via memset(0), you can use these
- * stub operations.
- */
- NS_COM_GLUE const PLDHashTableOps *
- PL_DHashGetStubOps(void);
- /*
- * Dynamically allocate a new PLDHashTable using malloc, initialize it using
- * PL_DHashTableInit, and return its address. Return null on malloc failure.
- * Note that the entry storage at table->entryStore will be allocated using
- * the ops->allocTable callback.
- */
- NS_COM_GLUE PLDHashTable *
- PL_NewDHashTable(const PLDHashTableOps *ops, void *data, PRUint32 entrySize,
- PRUint32 capacity);
- /*
- * Finalize table's data, free its entry storage (via table->ops->freeTable),
- * and return the memory starting at table to the malloc heap.
- */
- NS_COM_GLUE void
- PL_DHashTableDestroy(PLDHashTable *table);
- /*
- * Initialize table with ops, data, entrySize, and capacity. Capacity is a
- * guess for the smallest table size at which the table will usually be less
- * than 75% loaded (the table will grow or shrink as needed; capacity serves
- * only to avoid inevitable early growth from PL_DHASH_MIN_SIZE).
- */
- NS_COM_GLUE PRBool
- PL_DHashTableInit(PLDHashTable *table, const PLDHashTableOps *ops, void *data,
- PRUint32 entrySize, PRUint32 capacity);
- /*
- * Set maximum and minimum alpha for table. The defaults are 0.75 and .25.
- * maxAlpha must be in [0.5, 0.9375] for the default PL_DHASH_MIN_SIZE; or if
- * MinSize=PL_DHASH_MIN_SIZE <= 256, in [0.5, (float)(MinSize-1)/MinSize]; or
- * else in [0.5, 255.0/256]. minAlpha must be in [0, maxAlpha / 2), so that
- * we don't shrink on the very next remove after growing a table upon adding
- * an entry that brings entryCount past maxAlpha * tableSize.
- */
- NS_COM_GLUE void
- PL_DHashTableSetAlphaBounds(PLDHashTable *table,
- float maxAlpha,
- float minAlpha);
- /*
- * Call this macro with k, the number of pointer-sized words wasted per entry
- * under chaining, to compute the minimum alpha at which double hashing still
- * beats chaining.
- */
- #define PL_DHASH_MIN_ALPHA(table, k) \
- ((float)((table)->entrySize / sizeof(void *) - 1) \
- / ((table)->entrySize / sizeof(void *) + (k)))
- /*
- * Default max/min alpha, and macros to compute the value for the |capacity|
- * parameter to PL_NewDHashTable and PL_DHashTableInit, given default or any
- * max alpha, such that adding entryCount entries right after initializing the
- * table will not require a reallocation (so PL_DHASH_ADD can't fail for those
- * PL_DHashTableOperate calls).
- *
- * NB: PL_DHASH_CAP is a helper macro meant for use only in PL_DHASH_CAPACITY.
- * Don't use it directly!
- */
- #define PL_DHASH_DEFAULT_MAX_ALPHA 0.75
- #define PL_DHASH_DEFAULT_MIN_ALPHA 0.25
- #define PL_DHASH_CAP(entryCount, maxAlpha) \
- ((PRUint32)((double)(entryCount) / (maxAlpha)))
- #define PL_DHASH_CAPACITY(entryCount, maxAlpha) \
- (PL_DHASH_CAP(entryCount, maxAlpha) + \
- (((PL_DHASH_CAP(entryCount, maxAlpha) * (uint8)(0x100 * (maxAlpha))) \
- >> 8) < (entryCount)))
- #define PL_DHASH_DEFAULT_CAPACITY(entryCount) \
- PL_DHASH_CAPACITY(entryCount, PL_DHASH_DEFAULT_MAX_ALPHA)
- /*
- * Finalize table's data, free its entry storage using table->ops->freeTable,
- * and leave its members unchanged from their last live values (which leaves
- * pointers dangling). If you want to burn cycles clearing table, it's up to
- * your code to call memset.
- */
- NS_COM_GLUE void
- PL_DHashTableFinish(PLDHashTable *table);
- /*
- * To consolidate keyHash computation and table grow/shrink code, we use a
- * single entry point for lookup, add, and remove operations. The operation
- * codes are declared here, along with codes returned by PLDHashEnumerator
- * functions, which control PL_DHashTableEnumerate's behavior.
- */
- typedef enum PLDHashOperator {
- PL_DHASH_LOOKUP = 0, /* lookup entry */
- PL_DHASH_ADD = 1, /* add entry */
- PL_DHASH_REMOVE = 2, /* remove entry, or enumerator says remove */
- PL_DHASH_NEXT = 0, /* enumerator says continue */
- PL_DHASH_STOP = 1 /* enumerator says stop */
- } PLDHashOperator;
- /*
- * To lookup a key in table, call:
- *
- * entry = PL_DHashTableOperate(table, key, PL_DHASH_LOOKUP);
- *
- * If PL_DHASH_ENTRY_IS_BUSY(entry) is true, key was found and it identifies
- * entry. If PL_DHASH_ENTRY_IS_FREE(entry) is true, key was not found.
- *
- * To add an entry identified by key to table, call:
- *
- * entry = PL_DHashTableOperate(table, key, PL_DHASH_ADD);
- *
- * If entry is null upon return, then either the table is severely overloaded,
- * and memory can't be allocated for entry storage via table->ops->allocTable;
- * Or if table->ops->initEntry is non-null, the table->ops->initEntry op may
- * have returned false.
- *
- * Otherwise, entry->keyHash has been set so that PL_DHASH_ENTRY_IS_BUSY(entry)
- * is true, and it is up to the caller to initialize the key and value parts
- * of the entry sub-type, if they have not been set already (i.e. if entry was
- * not already in the table, and if the optional initEntry hook was not used).
- *
- * To remove an entry identified by key from table, call:
- *
- * (void) PL_DHashTableOperate(table, key, PL_DHASH_REMOVE);
- *
- * If key's entry is found, it is cleared (via table->ops->clearEntry) and
- * the entry is marked so that PL_DHASH_ENTRY_IS_FREE(entry). This operation
- * returns null unconditionally; you should ignore its return value.
- */
- NS_COM_GLUE PLDHashEntryHdr * PL_DHASH_FASTCALL
- PL_DHashTableOperate(PLDHashTable *table, const void *key, PLDHashOperator op);
- /*
- * Remove an entry already accessed via LOOKUP or ADD.
- *
- * NB: this is a "raw" or low-level routine, intended to be used only where
- * the inefficiency of a full PL_DHashTableOperate (which rehashes in order
- * to find the entry given its key) is not tolerable. This function does not
- * shrink the table if it is underloaded. It does not update stats #ifdef
- * PL_DHASHMETER, either.
- */
- NS_COM_GLUE void
- PL_DHashTableRawRemove(PLDHashTable *table, PLDHashEntryHdr *entry);
- /*
- * Enumerate entries in table using etor:
- *
- * count = PL_DHashTableEnumerate(table, etor, arg);
- *
- * PL_DHashTableEnumerate calls etor like so:
- *
- * op = etor(table, entry, number, arg);
- *
- * where number is a zero-based ordinal assigned to live entries according to
- * their order in table->entryStore.
- *
- * The return value, op, is treated as a set of flags. If op is PL_DHASH_NEXT,
- * then continue enumerating. If op contains PL_DHASH_REMOVE, then clear (via
- * table->ops->clearEntry) and free entry. Then we check whether op contains
- * PL_DHASH_STOP; if so, stop enumerating and return the number of live entries
- * that were enumerated so far. Return the total number of live entries when
- * enumeration completes normally.
- *
- * If etor calls PL_DHashTableOperate on table with op != PL_DHASH_LOOKUP, it
- * must return PL_DHASH_STOP; otherwise undefined behavior results.
- *
- * If any enumerator returns PL_DHASH_REMOVE, table->entryStore may be shrunk
- * or compressed after enumeration, but before PL_DHashTableEnumerate returns.
- * Such an enumerator therefore can't safely set aside entry pointers, but an
- * enumerator that never returns PL_DHASH_REMOVE can set pointers to entries
- * aside, e.g., to avoid copying live entries into an array of the entry type.
- * Copying entry pointers is cheaper, and safe so long as the caller of such a
- * "stable" Enumerate doesn't use the set-aside pointers after any call either
- * to PL_DHashTableOperate, or to an "unstable" form of Enumerate, which might
- * grow or shrink entryStore.
- *
- * If your enumerator wants to remove certain entries, but set aside pointers
- * to other entries that it retains, it can use PL_DHashTableRawRemove on the
- * entries to be removed, returning PL_DHASH_NEXT to skip them. Likewise, if
- * you want to remove entries, but for some reason you do not want entryStore
- * to be shrunk or compressed, you can call PL_DHashTableRawRemove safely on
- * the entry being enumerated, rather than returning PL_DHASH_REMOVE.
- */
- typedef PLDHashOperator
- (* PR_CALLBACK PLDHashEnumerator)(PLDHashTable *table, PLDHashEntryHdr *hdr,
- PRUint32 number, void *arg);
- NS_COM_GLUE PRUint32
- PL_DHashTableEnumerate(PLDHashTable *table, PLDHashEnumerator etor, void *arg);
- #ifdef PL_DHASHMETER
- #include <stdio.h>
- NS_COM_GLUE void
- PL_DHashTableDumpMeter(PLDHashTable *table, PLDHashEnumerator dump, FILE *fp);
- #endif
- PR_END_EXTERN_C
- #endif /* pldhash_h___ */