gecko-dev/xpcom/glue/PLDHashTable.cpp

801 строка
21 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */
#include <new>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "PLDHashTable.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/MathAlgorithms.h"
#include "nsAlgorithm.h"
#include "mozilla/Likely.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/ChaosMode.h"
using namespace mozilla;
#ifdef DEBUG
class AutoReadOp
{
Checker& mChk;
public:
explicit AutoReadOp(Checker& aChk) : mChk(aChk) { mChk.StartReadOp(); }
~AutoReadOp() { mChk.EndReadOp(); }
};
class AutoWriteOp
{
Checker& mChk;
public:
explicit AutoWriteOp(Checker& aChk) : mChk(aChk) { mChk.StartWriteOp(); }
~AutoWriteOp() { mChk.EndWriteOp(); }
};
class AutoIteratorRemovalOp
{
Checker& mChk;
public:
explicit AutoIteratorRemovalOp(Checker& aChk)
: mChk(aChk)
{
mChk.StartIteratorRemovalOp();
}
~AutoIteratorRemovalOp() { mChk.EndIteratorRemovalOp(); }
};
class AutoDestructorOp
{
Checker& mChk;
public:
explicit AutoDestructorOp(Checker& aChk)
: mChk(aChk)
{
mChk.StartDestructorOp();
}
~AutoDestructorOp() { mChk.EndDestructorOp(); }
};
#endif
/* static */ PLDHashNumber
PLDHashTable::HashStringKey(const void* aKey)
{
return HashString(static_cast<const char*>(aKey));
}
/* static */ PLDHashNumber
PLDHashTable::HashVoidPtrKeyStub(const void* aKey)
{
return (PLDHashNumber)(ptrdiff_t)aKey >> 2;
}
/* static */ bool
PLDHashTable::MatchEntryStub(const PLDHashEntryHdr* aEntry, const void* aKey)
{
const PLDHashEntryStub* stub = (const PLDHashEntryStub*)aEntry;
return stub->key == aKey;
}
/* static */ bool
PLDHashTable::MatchStringKey(const PLDHashEntryHdr* aEntry, const void* aKey)
{
const PLDHashEntryStub* stub = (const PLDHashEntryStub*)aEntry;
// XXX tolerate null keys on account of sloppy Mozilla callers.
return stub->key == aKey ||
(stub->key && aKey &&
strcmp((const char*)stub->key, (const char*)aKey) == 0);
}
/* static */ void
PLDHashTable::MoveEntryStub(PLDHashTable* aTable,
const PLDHashEntryHdr* aFrom,
PLDHashEntryHdr* aTo)
{
memcpy(aTo, aFrom, aTable->mEntrySize);
}
/* static */ void
PLDHashTable::ClearEntryStub(PLDHashTable* aTable, PLDHashEntryHdr* aEntry)
{
memset(aEntry, 0, aTable->mEntrySize);
}
static const PLDHashTableOps gStubOps = {
PLDHashTable::HashVoidPtrKeyStub,
PLDHashTable::MatchEntryStub,
PLDHashTable::MoveEntryStub,
PLDHashTable::ClearEntryStub,
nullptr
};
/* static */ const PLDHashTableOps*
PLDHashTable::StubOps()
{
return &gStubOps;
}
static bool
SizeOfEntryStore(uint32_t aCapacity, uint32_t aEntrySize, uint32_t* aNbytes)
{
uint64_t nbytes64 = uint64_t(aCapacity) * uint64_t(aEntrySize);
*aNbytes = aCapacity * aEntrySize;
return uint64_t(*aNbytes) == nbytes64; // returns false on overflow
}
// Compute max and min load numbers (entry counts). We have a secondary max
// that allows us to overload a table reasonably if it cannot be grown further
// (i.e. if ChangeTable() fails). The table slows down drastically if the
// secondary max is too close to 1, but 0.96875 gives only a slight slowdown
// while allowing 1.3x more elements.
static inline uint32_t
MaxLoad(uint32_t aCapacity)
{
return aCapacity - (aCapacity >> 2); // == aCapacity * 0.75
}
static inline uint32_t
MaxLoadOnGrowthFailure(uint32_t aCapacity)
{
return aCapacity - (aCapacity >> 5); // == aCapacity * 0.96875
}
static inline uint32_t
MinLoad(uint32_t aCapacity)
{
return aCapacity >> 2; // == aCapacity * 0.25
}
// Compute the minimum capacity (and the Log2 of that capacity) for a table
// containing |aLength| elements while respecting the following contraints:
// - table must be at most 75% full;
// - capacity must be a power of two;
// - capacity cannot be too small.
static inline void
BestCapacity(uint32_t aLength, uint32_t* aCapacityOut,
uint32_t* aLog2CapacityOut)
{
// Compute the smallest capacity allowing |aLength| elements to be inserted
// without rehashing.
uint32_t capacity = (aLength * 4 + (3 - 1)) / 3; // == ceil(aLength * 4 / 3)
if (capacity < PLDHashTable::kMinCapacity) {
capacity = PLDHashTable::kMinCapacity;
}
// Round up capacity to next power-of-two.
uint32_t log2 = CeilingLog2(capacity);
capacity = 1u << log2;
MOZ_ASSERT(capacity <= PLDHashTable::kMaxCapacity);
*aCapacityOut = capacity;
*aLog2CapacityOut = log2;
}
/* static */ MOZ_ALWAYS_INLINE uint32_t
PLDHashTable::HashShift(uint32_t aEntrySize, uint32_t aLength)
{
if (aLength > kMaxInitialLength) {
MOZ_CRASH("Initial length is too large");
}
uint32_t capacity, log2;
BestCapacity(aLength, &capacity, &log2);
uint32_t nbytes;
if (!SizeOfEntryStore(capacity, aEntrySize, &nbytes)) {
MOZ_CRASH("Initial entry store size is too large");
}
// Compute the hashShift value.
return kHashBits - log2;
}
PLDHashTable::PLDHashTable(const PLDHashTableOps* aOps, uint32_t aEntrySize,
uint32_t aLength)
: mOps(aOps)
, mHashShift(HashShift(aEntrySize, aLength))
, mEntrySize(aEntrySize)
, mEntryCount(0)
, mRemovedCount(0)
, mEntryStore()
#ifdef DEBUG
, mChecker()
#endif
{
}
PLDHashTable&
PLDHashTable::operator=(PLDHashTable&& aOther)
{
if (this == &aOther) {
return *this;
}
// Destruct |this|.
this->~PLDHashTable();
// |mOps| and |mEntrySize| are const so we can't assign them. Instead, we
// require that they are equal. The justification for this is that they're
// conceptually part of the type -- indeed, if PLDHashTable was a templated
// type like nsTHashtable, they *would* be part of the type -- so it only
// makes sense to assign in cases where they match.
MOZ_RELEASE_ASSERT(mOps == aOther.mOps);
MOZ_RELEASE_ASSERT(mEntrySize == aOther.mEntrySize);
// Move non-const pieces over.
mHashShift = Move(aOther.mHashShift);
mEntryCount = Move(aOther.mEntryCount);
mRemovedCount = Move(aOther.mRemovedCount);
mEntryStore = Move(aOther.mEntryStore);
#ifdef DEBUG
mChecker = Move(aOther.mChecker);
#endif
// Clear up |aOther| so its destruction will be a no-op.
{
#ifdef DEBUG
AutoDestructorOp op(mChecker);
#endif
aOther.mEntryStore.Set(nullptr);
}
return *this;
}
PLDHashNumber
PLDHashTable::Hash1(PLDHashNumber aHash0)
{
return aHash0 >> mHashShift;
}
// Double hashing needs the second hash code to be relatively prime to table
// size, so we simply make hash2 odd.
void
PLDHashTable::Hash2(PLDHashNumber aHash,
uint32_t& aHash2Out, uint32_t& aSizeMaskOut)
{
uint32_t sizeLog2 = kHashBits - mHashShift;
aHash2Out = ((aHash << sizeLog2) >> mHashShift) | 1;
aSizeMaskOut = (PLDHashNumber(1) << sizeLog2) - 1;
}
// Reserve mKeyHash 0 for free entries and 1 for removed-entry sentinels. Note
// that a removed-entry sentinel need be stored only if the removed entry had
// a colliding entry added after it. Therefore we can use 1 as the collision
// flag in addition to the removed-entry sentinel value. Multiplicative hash
// uses the high order bits of mKeyHash, so this least-significant reservation
// should not hurt the hash function's effectiveness much.
// Match an entry's mKeyHash against an unstored one computed from a key.
/* static */ bool
PLDHashTable::MatchEntryKeyhash(PLDHashEntryHdr* aEntry, PLDHashNumber aKeyHash)
{
return (aEntry->mKeyHash & ~kCollisionFlag) == aKeyHash;
}
// Compute the address of the indexed entry in table.
PLDHashEntryHdr*
PLDHashTable::AddressEntry(uint32_t aIndex)
{
return reinterpret_cast<PLDHashEntryHdr*>(
mEntryStore.Get() + aIndex * mEntrySize);
}
PLDHashTable::~PLDHashTable()
{
#ifdef DEBUG
AutoDestructorOp op(mChecker);
#endif
if (!mEntryStore.Get()) {
return;
}
// Clear any remaining live entries.
char* entryAddr = mEntryStore.Get();
char* entryLimit = entryAddr + Capacity() * mEntrySize;
while (entryAddr < entryLimit) {
PLDHashEntryHdr* entry = (PLDHashEntryHdr*)entryAddr;
if (EntryIsLive(entry)) {
mOps->clearEntry(this, entry);
}
entryAddr += mEntrySize;
}
// Entry storage is freed last, by ~EntryStore().
}
void
PLDHashTable::ClearAndPrepareForLength(uint32_t aLength)
{
// Get these values before the destructor clobbers them.
const PLDHashTableOps* ops = mOps;
uint32_t entrySize = mEntrySize;
this->~PLDHashTable();
new (this) PLDHashTable(ops, entrySize, aLength);
}
void
PLDHashTable::Clear()
{
ClearAndPrepareForLength(kDefaultInitialLength);
}
// If |IsAdd| is true, the return value is always non-null and it may be a
// previously-removed entry. If |IsAdd| is false, the return value is null on a
// miss, and will never be a previously-removed entry on a hit. This
// distinction is a bit grotty but this function is hot enough that these
// differences are worthwhile.
template <PLDHashTable::SearchReason Reason>
PLDHashEntryHdr* NS_FASTCALL
PLDHashTable::SearchTable(const void* aKey, PLDHashNumber aKeyHash)
{
MOZ_ASSERT(mEntryStore.Get());
NS_ASSERTION(!(aKeyHash & kCollisionFlag),
"!(aKeyHash & kCollisionFlag)");
// Compute the primary hash address.
PLDHashNumber hash1 = Hash1(aKeyHash);
PLDHashEntryHdr* entry = AddressEntry(hash1);
// Miss: return space for a new entry.
if (EntryIsFree(entry)) {
return (Reason == ForAdd) ? entry : nullptr;
}
// Hit: return entry.
PLDHashMatchEntry matchEntry = mOps->matchEntry;
if (MatchEntryKeyhash(entry, aKeyHash) &&
matchEntry(entry, aKey)) {
return entry;
}
// Collision: double hash.
PLDHashNumber hash2;
uint32_t sizeMask;
Hash2(aKeyHash, hash2, sizeMask);
// Save the first removed entry pointer so Add() can recycle it. (Only used
// if Reason==ForAdd.)
PLDHashEntryHdr* firstRemoved = nullptr;
for (;;) {
if (Reason == ForAdd) {
if (MOZ_UNLIKELY(EntryIsRemoved(entry))) {
if (!firstRemoved) {
firstRemoved = entry;
}
} else {
entry->mKeyHash |= kCollisionFlag;
}
}
hash1 -= hash2;
hash1 &= sizeMask;
entry = AddressEntry(hash1);
if (EntryIsFree(entry)) {
return (Reason == ForAdd) ? (firstRemoved ? firstRemoved : entry)
: nullptr;
}
if (MatchEntryKeyhash(entry, aKeyHash) &&
matchEntry(entry, aKey)) {
return entry;
}
}
// NOTREACHED
return nullptr;
}
// This is a copy of SearchTable(), used by ChangeTable(), hardcoded to
// 1. assume |aIsAdd| is true,
// 2. assume that |aKey| will never match an existing entry, and
// 3. assume that no entries have been removed from the current table
// structure.
// Avoiding the need for |aKey| means we can avoid needing a way to map entries
// to keys, which means callers can use complex key types more easily.
MOZ_ALWAYS_INLINE PLDHashEntryHdr*
PLDHashTable::FindFreeEntry(PLDHashNumber aKeyHash)
{
MOZ_ASSERT(mEntryStore.Get());
NS_ASSERTION(!(aKeyHash & kCollisionFlag),
"!(aKeyHash & kCollisionFlag)");
// Compute the primary hash address.
PLDHashNumber hash1 = Hash1(aKeyHash);
PLDHashEntryHdr* entry = AddressEntry(hash1);
// Miss: return space for a new entry.
if (EntryIsFree(entry)) {
return entry;
}
// Collision: double hash.
PLDHashNumber hash2;
uint32_t sizeMask;
Hash2(aKeyHash, hash2, sizeMask);
for (;;) {
NS_ASSERTION(!EntryIsRemoved(entry),
"!EntryIsRemoved(entry)");
entry->mKeyHash |= kCollisionFlag;
hash1 -= hash2;
hash1 &= sizeMask;
entry = AddressEntry(hash1);
if (EntryIsFree(entry)) {
return entry;
}
}
// NOTREACHED
}
bool
PLDHashTable::ChangeTable(int32_t aDeltaLog2)
{
MOZ_ASSERT(mEntryStore.Get());
// Look, but don't touch, until we succeed in getting new entry store.
int32_t oldLog2 = kHashBits - mHashShift;
int32_t newLog2 = oldLog2 + aDeltaLog2;
uint32_t newCapacity = 1u << newLog2;
if (newCapacity > kMaxCapacity) {
return false;
}
uint32_t nbytes;
if (!SizeOfEntryStore(newCapacity, mEntrySize, &nbytes)) {
return false; // overflowed
}
char* newEntryStore = (char*)malloc(nbytes);
if (!newEntryStore) {
return false;
}
// We can't fail from here on, so update table parameters.
mHashShift = kHashBits - newLog2;
mRemovedCount = 0;
// Assign the new entry store to table.
memset(newEntryStore, 0, nbytes);
char* oldEntryStore;
char* oldEntryAddr;
oldEntryAddr = oldEntryStore = mEntryStore.Get();
mEntryStore.Set(newEntryStore);
PLDHashMoveEntry moveEntry = mOps->moveEntry;
// Copy only live entries, leaving removed ones behind.
uint32_t oldCapacity = 1u << oldLog2;
for (uint32_t i = 0; i < oldCapacity; ++i) {
PLDHashEntryHdr* oldEntry = (PLDHashEntryHdr*)oldEntryAddr;
if (EntryIsLive(oldEntry)) {
oldEntry->mKeyHash &= ~kCollisionFlag;
PLDHashEntryHdr* newEntry = FindFreeEntry(oldEntry->mKeyHash);
NS_ASSERTION(EntryIsFree(newEntry), "EntryIsFree(newEntry)");
moveEntry(this, oldEntry, newEntry);
newEntry->mKeyHash = oldEntry->mKeyHash;
}
oldEntryAddr += mEntrySize;
}
free(oldEntryStore);
return true;
}
MOZ_ALWAYS_INLINE PLDHashNumber
PLDHashTable::ComputeKeyHash(const void* aKey)
{
MOZ_ASSERT(mEntryStore.Get());
PLDHashNumber keyHash = mOps->hashKey(aKey);
keyHash *= kGoldenRatio;
// Avoid 0 and 1 hash codes, they indicate free and removed entries.
if (keyHash < 2) {
keyHash -= 2;
}
keyHash &= ~kCollisionFlag;
return keyHash;
}
PLDHashEntryHdr*
PLDHashTable::Search(const void* aKey)
{
#ifdef DEBUG
AutoReadOp op(mChecker);
#endif
PLDHashEntryHdr* entry = mEntryStore.Get()
? SearchTable<ForSearchOrRemove>(aKey,
ComputeKeyHash(aKey))
: nullptr;
return entry;
}
PLDHashEntryHdr*
PLDHashTable::Add(const void* aKey, const mozilla::fallible_t&)
{
#ifdef DEBUG
AutoWriteOp op(mChecker);
#endif
// Allocate the entry storage if it hasn't already been allocated.
if (!mEntryStore.Get()) {
uint32_t nbytes;
// We already checked this in the constructor, so it must still be true.
MOZ_RELEASE_ASSERT(SizeOfEntryStore(CapacityFromHashShift(), mEntrySize,
&nbytes));
mEntryStore.Set((char*)malloc(nbytes));
if (!mEntryStore.Get()) {
return nullptr;
}
memset(mEntryStore.Get(), 0, nbytes);
}
// If alpha is >= .75, grow or compress the table. If aKey is already in the
// table, we may grow once more than necessary, but only if we are on the
// edge of being overloaded.
uint32_t capacity = Capacity();
if (mEntryCount + mRemovedCount >= MaxLoad(capacity)) {
// Compress if a quarter or more of all entries are removed.
int deltaLog2;
if (mRemovedCount >= capacity >> 2) {
deltaLog2 = 0;
} else {
deltaLog2 = 1;
}
// Grow or compress the table. If ChangeTable() fails, allow overloading up
// to the secondary max. Once we hit the secondary max, return null.
if (!ChangeTable(deltaLog2) &&
mEntryCount + mRemovedCount >= MaxLoadOnGrowthFailure(capacity)) {
return nullptr;
}
}
// Look for entry after possibly growing, so we don't have to add it,
// then skip it while growing the table and re-add it after.
PLDHashNumber keyHash = ComputeKeyHash(aKey);
PLDHashEntryHdr* entry = SearchTable<ForAdd>(aKey, keyHash);
if (!EntryIsLive(entry)) {
// Initialize the entry, indicating that it's no longer free.
if (EntryIsRemoved(entry)) {
mRemovedCount--;
keyHash |= kCollisionFlag;
}
if (mOps->initEntry) {
mOps->initEntry(entry, aKey);
}
entry->mKeyHash = keyHash;
mEntryCount++;
}
return entry;
}
PLDHashEntryHdr*
PLDHashTable::Add(const void* aKey)
{
PLDHashEntryHdr* entry = Add(aKey, fallible);
if (!entry) {
if (!mEntryStore.Get()) {
// We OOM'd while allocating the initial entry storage.
uint32_t nbytes;
(void) SizeOfEntryStore(CapacityFromHashShift(), mEntrySize, &nbytes);
NS_ABORT_OOM(nbytes);
} else {
// We failed to resize the existing entry storage, either due to OOM or
// because we exceeded the maximum table capacity or size; report it as
// an OOM. The multiplication by 2 gets us the size we tried to allocate,
// which is double the current size.
NS_ABORT_OOM(2 * EntrySize() * EntryCount());
}
}
return entry;
}
void
PLDHashTable::Remove(const void* aKey)
{
#ifdef DEBUG
AutoWriteOp op(mChecker);
#endif
PLDHashEntryHdr* entry = mEntryStore.Get()
? SearchTable<ForSearchOrRemove>(aKey,
ComputeKeyHash(aKey))
: nullptr;
if (entry) {
RawRemove(entry);
ShrinkIfAppropriate();
}
}
void
PLDHashTable::RemoveEntry(PLDHashEntryHdr* aEntry)
{
#ifdef DEBUG
AutoWriteOp op(mChecker);
#endif
RawRemove(aEntry);
ShrinkIfAppropriate();
}
void
PLDHashTable::RawRemove(PLDHashEntryHdr* aEntry)
{
// Unfortunately, we can only do weak checking here. That's because
// RawRemove() can be called legitimately while an Enumerate() call is
// active, which doesn't fit well into how Checker's mState variable works.
MOZ_ASSERT(mChecker.IsWritable());
MOZ_ASSERT(mEntryStore.Get());
MOZ_ASSERT(EntryIsLive(aEntry), "EntryIsLive(aEntry)");
// Load keyHash first in case clearEntry() goofs it.
PLDHashNumber keyHash = aEntry->mKeyHash;
mOps->clearEntry(this, aEntry);
if (keyHash & kCollisionFlag) {
MarkEntryRemoved(aEntry);
mRemovedCount++;
} else {
MarkEntryFree(aEntry);
}
mEntryCount--;
}
// Shrink or compress if a quarter or more of all entries are removed, or if the
// table is underloaded according to the minimum alpha, and is not minimal-size
// already.
void
PLDHashTable::ShrinkIfAppropriate()
{
uint32_t capacity = Capacity();
if (mRemovedCount >= capacity >> 2 ||
(capacity > kMinCapacity && mEntryCount <= MinLoad(capacity))) {
uint32_t log2;
BestCapacity(mEntryCount, &capacity, &log2);
int32_t deltaLog2 = log2 - (kHashBits - mHashShift);
MOZ_ASSERT(deltaLog2 <= 0);
(void) ChangeTable(deltaLog2);
}
}
size_t
PLDHashTable::ShallowSizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
{
#ifdef DEBUG
AutoReadOp op(mChecker);
#endif
return aMallocSizeOf(mEntryStore.Get());
}
size_t
PLDHashTable::ShallowSizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
{
return aMallocSizeOf(this) + ShallowSizeOfExcludingThis(aMallocSizeOf);
}
PLDHashTable::Iterator::Iterator(Iterator&& aOther)
: mTable(aOther.mTable)
, mStart(aOther.mStart)
, mLimit(aOther.mLimit)
, mCurrent(aOther.mCurrent)
, mNexts(aOther.mNexts)
, mNextsLimit(aOther.mNextsLimit)
, mHaveRemoved(aOther.mHaveRemoved)
{
// No need to change |mChecker| here.
aOther.mTable = nullptr;
aOther.mStart = nullptr;
aOther.mLimit = nullptr;
aOther.mCurrent = nullptr;
aOther.mNexts = 0;
aOther.mNextsLimit = 0;
aOther.mHaveRemoved = false;
}
PLDHashTable::Iterator::Iterator(PLDHashTable* aTable)
: mTable(aTable)
, mStart(mTable->mEntryStore.Get())
, mLimit(mTable->mEntryStore.Get() + mTable->Capacity() * mTable->mEntrySize)
, mCurrent(mTable->mEntryStore.Get())
, mNexts(0)
, mNextsLimit(mTable->EntryCount())
, mHaveRemoved(false)
{
#ifdef DEBUG
mTable->mChecker.StartReadOp();
#endif
if (ChaosMode::isActive(ChaosFeature::HashTableIteration) &&
mTable->Capacity() > 0) {
// Start iterating at a random entry. It would be even more chaotic to
// iterate in fully random order, but that's harder.
mCurrent += ChaosMode::randomUint32LessThan(mTable->Capacity()) *
mTable->mEntrySize;
}
// Advance to the first live entry, if there is one.
if (!Done()) {
while (IsOnNonLiveEntry()) {
MoveToNextEntry();
}
}
}
PLDHashTable::Iterator::~Iterator()
{
if (mTable) {
if (mHaveRemoved) {
mTable->ShrinkIfAppropriate();
}
#ifdef DEBUG
mTable->mChecker.EndReadOp();
#endif
}
}
MOZ_ALWAYS_INLINE bool
PLDHashTable::Iterator::IsOnNonLiveEntry() const
{
MOZ_ASSERT(!Done());
return !EntryIsLive(reinterpret_cast<PLDHashEntryHdr*>(mCurrent));
}
MOZ_ALWAYS_INLINE void
PLDHashTable::Iterator::MoveToNextEntry()
{
mCurrent += mTable->mEntrySize;
if (mCurrent == mLimit) {
mCurrent = mStart; // Wrap-around. Possible due to Chaos Mode.
}
}
void
PLDHashTable::Iterator::Next()
{
MOZ_ASSERT(!Done());
mNexts++;
// Advance to the next live entry, if there is one.
if (!Done()) {
do {
MoveToNextEntry();
} while (IsOnNonLiveEntry());
}
}
void
PLDHashTable::Iterator::Remove()
{
// This cast is needed for the same reason as the one in the destructor.
mTable->RawRemove(Get());
mHaveRemoved = true;
}
#ifdef DEBUG
void
PLDHashTable::MarkImmutable()
{
mChecker.SetNonWritable();
}
#endif