The Tor Browser: xpcom/glue/pldhash.h@97036ab72558 (annotated)

xpcom/glue/pldhash.h@97036ab72558 (annotated)

xpcom/glue/pldhash.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /* 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/. */
 #ifndef pldhash_h___
 #define pldhash_h___
 /*
  * Double hashing, a la Knuth 6.
  */
 #include "mozilla/fallible.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Types.h"
 #include "nscore.h"
 #if defined(__GNUC__) && defined(__i386__)
 #define PL_DHASH_FASTCALL __attribute__ ((regparm (3),stdcall))
 #elif defined(XP_WIN)
 #define PL_DHASH_FASTCALL __fastcall
 #else
 #define PL_DHASH_FASTCALL
 #endif
 /*
  * Table size limit; do not exceed.  The max capacity used to be 1<<23 but that
  * occasionally that wasn't enough.  Making it much bigger than 1<<26 probably
  * isn't worthwhile -- tables that big are kind of ridiculous.  Also, the
  * growth operation will (deliberately) fail if |capacity * entrySize|
  * overflows a uint32_t, and entrySize is always at least 8 bytes.
  */
 #undef PL_DHASH_MAX_SIZE
 #define PL_DHASH_MAX_SIZE     ((uint32_t)1 << 26)
 /* 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 uint32_t                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 function 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 */
 };
 MOZ_ALWAYS_INLINE bool
 PL_DHASH_ENTRY_IS_FREE(PLDHashEntryHdr* entry)
 {
     return entry->keyHash == 0;
 }
 MOZ_ALWAYS_INLINE bool
 PL_DHASH_ENTRY_IS_BUSY(PLDHashEntryHdr* entry)
 {
     return !PL_DHASH_ENTRY_IS_FREE(entry);
 }
 MOZ_ALWAYS_INLINE bool
 PL_DHASH_ENTRY_IS_LIVE(PLDHashEntryHdr* entry)
 {
     return 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.
  *
  * 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 */
     int16_t             hashShift;      /* multiplicative hash shift */
     /*
      * |recursionLevel| is only used in debug builds, but is present in opt
      * builds to avoid binary compatibility problems when mixing DEBUG and
      * non-DEBUG components.  (Actually, even if it were removed,
      * sizeof(PLDHashTable) wouldn't change, due to struct padding.)
      */
     uint16_t            recursionLevel; /* used to detect unsafe re-entry */
     uint32_t            entrySize;      /* number of bytes in an entry */
     uint32_t            entryCount;     /* number of entries in table */
     uint32_t            removedCount;   /* removed entry sentinels in table */
     uint32_t            generation;     /* entry storage generation number */
     char                *entryStore;    /* entry storage */
 #ifdef PL_DHASHMETER
     struct PLDHashStats {
         uint32_t        searches;       /* total number of table searches */
         uint32_t        steps;          /* hash chain links traversed */
         uint32_t        hits;           /* searches that found key */
         uint32_t        misses;         /* searches that didn't find key */
         uint32_t        lookups;        /* number of PL_DHASH_LOOKUPs */
         uint32_t        addMisses;      /* adds that miss, and do work */
         uint32_t        addOverRemoved; /* adds that recycled a removed entry */
         uint32_t        addHits;        /* adds that hit an existing entry */
         uint32_t        addFailures;    /* out-of-memory during add growth */
         uint32_t        removeHits;     /* removes that hit, and do work */
         uint32_t        removeMisses;   /* useless removes that miss */
         uint32_t        removeFrees;    /* removes that freed entry directly */
         uint32_t        removeEnums;    /* removes done by Enumerate */
         uint32_t        grows;          /* table expansions */
         uint32_t        shrinks;        /* table contractions */
         uint32_t        compresses;     /* table compressions */
         uint32_t        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) \
     ((uint32_t)1 << (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 *
 (* PLDHashAllocTable)(PLDHashTable *table, uint32_t nbytes);
 typedef void
 (* 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
 (* PLDHashHashKey)   (PLDHashTable *table, const void *key);
 /*
  * Compare the key identifying entry in table with the provided key parameter.
  * Return true if keys match, false otherwise.
  */
 typedef bool
 (* 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
 (* 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
 (* 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
 (* 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 bool
 (* 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 true on success, 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, uint32_t 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 bool
 PL_DHashMatchEntryStub(PLDHashTable *table,
                        const PLDHashEntryHdr *entry,
                        const void *key);
 NS_COM_GLUE bool
 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, uint32_t entrySize,
                  uint32_t 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).  This will
  * crash if it can't allocate enough memory, or if entrySize or capacity are
  * too large.
  */
 NS_COM_GLUE void
 PL_DHashTableInit(PLDHashTable *table, const PLDHashTableOps *ops, void *data,
                   uint32_t entrySize, uint32_t capacity);
 /*
  * Initialize table. This is the same as PL_DHashTableInit, except that it
  * returns a boolean indicating success, rather than crashing on failure.
  */
 NS_COM_GLUE bool
 PL_DHashTableInit(PLDHashTable *table, const PLDHashTableOps *ops, void *data,
                   uint32_t entrySize, uint32_t capacity,
                   const mozilla::fallible_t& ) MOZ_WARN_UNUSED_RESULT;
 /*
  * 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
 (* PLDHashEnumerator)(PLDHashTable *table, PLDHashEntryHdr *hdr, uint32_t number,
                       void *arg);
 NS_COM_GLUE uint32_t
 PL_DHashTableEnumerate(PLDHashTable *table, PLDHashEnumerator etor, void *arg);
 typedef size_t
 (* PLDHashSizeOfEntryExcludingThisFun)(PLDHashEntryHdr *hdr,
                                        mozilla::MallocSizeOf mallocSizeOf,
                                        void *arg);
 /**
  * Measure the size of the table's entry storage, and if
  * |sizeOfEntryExcludingThis| is non-nullptr, measure the size of things
  * pointed to by entries.  Doesn't measure |ops| because it's often shared
  * between tables, nor |data| because it's opaque.
  */
 NS_COM_GLUE size_t
 PL_DHashTableSizeOfExcludingThis(const PLDHashTable *table,
                                  PLDHashSizeOfEntryExcludingThisFun sizeOfEntryExcludingThis,
                                  mozilla::MallocSizeOf mallocSizeOf,
                                  void *arg = nullptr);
 /**
  * Like PL_DHashTableSizeOfExcludingThis, but includes sizeof(*this).
  */
 NS_COM_GLUE size_t
 PL_DHashTableSizeOfIncludingThis(const PLDHashTable *table,
                                  PLDHashSizeOfEntryExcludingThisFun sizeOfEntryExcludingThis,
                                  mozilla::MallocSizeOf mallocSizeOf,
                                  void *arg = nullptr);
 #ifdef DEBUG
 /**
  * Mark a table as immutable for the remainder of its lifetime.  This
  * changes the implementation from ASSERTing one set of invariants to
  * ASSERTing a different set.
  *
  * When a table is NOT marked as immutable, the table implementation
  * asserts that the table is not mutated from its own callbacks.  It
  * assumes the caller protects the table from being accessed on multiple
  * threads simultaneously.
  *
  * When the table is marked as immutable, the re-entry assertions will
  * no longer trigger erroneously due to multi-threaded access.  Instead,
  * mutations will cause assertions.
  */
 NS_COM_GLUE void
 PL_DHashMarkTableImmutable(PLDHashTable *table);
 #endif
 #ifdef PL_DHASHMETER
 #include <stdio.h>
 NS_COM_GLUE void
 PL_DHashTableDumpMeter(PLDHashTable *table, PLDHashEnumerator dump, FILE *fp);
 #endif
 #endif /* pldhash_h___ */

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xpcom/glue/pldhash.h@97036ab72558 (annotated)

xpcom/glue/pldhash.h