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gecko-dev/xpcom/glue/pldhash.cpp

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/* -*- 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/. */
/*
* Double hashing implementation.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pldhash.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/MathAlgorithms.h"
#include "nsDebug.h" /* for PR_ASSERT */
#include "nsAlgorithm.h"
#include "mozilla/Likely.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/ChaosMode.h"
#ifdef PL_DHASHMETER
# define METER(x) x
#else
# define METER(x) /* nothing */
#endif
/*
* The following DEBUG-only code is used to assert that calls to one of
* table->mOps or to an enumerator do not cause re-entry into a call that
* can mutate the table.
*/
#ifdef DEBUG
/*
* Most callers that assert about the recursion level don't care about
* this magical value because they are asserting that mutation is
* allowed (and therefore the level is 0 or 1, depending on whether they
* incremented it).
*
* Only PL_DHashTableFinish needs to allow this special value.
*/
#define IMMUTABLE_RECURSION_LEVEL UINT32_MAX
#define RECURSION_LEVEL_SAFE_TO_FINISH(table_) \
(table_->mRecursionLevel == 0 || \
table_->mRecursionLevel == IMMUTABLE_RECURSION_LEVEL)
#define INCREMENT_RECURSION_LEVEL(table_) \
do { \
if (table_->mRecursionLevel != IMMUTABLE_RECURSION_LEVEL) { \
const uint32_t oldRecursionLevel = table_->mRecursionLevel++; \
MOZ_ASSERT(oldRecursionLevel < IMMUTABLE_RECURSION_LEVEL - 1); \
} \
} while(0)
#define DECREMENT_RECURSION_LEVEL(table_) \
do { \
if (table_->mRecursionLevel != IMMUTABLE_RECURSION_LEVEL) { \
const uint32_t oldRecursionLevel = table_->mRecursionLevel--; \
MOZ_ASSERT(oldRecursionLevel > 0); \
} \
} while(0)
#else
#define INCREMENT_RECURSION_LEVEL(table_) do { } while(0)
#define DECREMENT_RECURSION_LEVEL(table_) do { } while(0)
#endif /* defined(DEBUG) */
using namespace mozilla;
PLDHashNumber
PL_DHashStringKey(PLDHashTable* aTable, const void* aKey)
{
return HashString(static_cast<const char*>(aKey));
}
PLDHashNumber
PL_DHashVoidPtrKeyStub(PLDHashTable* aTable, const void* aKey)
{
return (PLDHashNumber)(ptrdiff_t)aKey >> 2;
}
bool
PL_DHashMatchEntryStub(PLDHashTable* aTable,
const PLDHashEntryHdr* aEntry,
const void* aKey)
{
const PLDHashEntryStub* stub = (const PLDHashEntryStub*)aEntry;
return stub->key == aKey;
}
bool
PL_DHashMatchStringKey(PLDHashTable* aTable,
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);
}
MOZ_ALWAYS_INLINE void
PLDHashTable::MoveEntryStub(const PLDHashEntryHdr* aFrom,
PLDHashEntryHdr* aTo)
{
memcpy(aTo, aFrom, mEntrySize);
}
void
PL_DHashMoveEntryStub(PLDHashTable* aTable,
const PLDHashEntryHdr* aFrom,
PLDHashEntryHdr* aTo)
{
aTable->MoveEntryStub(aFrom, aTo);
}
MOZ_ALWAYS_INLINE void
PLDHashTable::ClearEntryStub(PLDHashEntryHdr* aEntry)
{
memset(aEntry, 0, mEntrySize);
}
void
PL_DHashClearEntryStub(PLDHashTable* aTable, PLDHashEntryHdr* aEntry)
{
aTable->ClearEntryStub(aEntry);
}
MOZ_ALWAYS_INLINE void
PLDHashTable::FreeStringKey(PLDHashEntryHdr* aEntry)
{
const PLDHashEntryStub* stub = (const PLDHashEntryStub*)aEntry;
free((void*)stub->key);
memset(aEntry, 0, mEntrySize);
}
void
PL_DHashFreeStringKey(PLDHashTable* aTable, PLDHashEntryHdr* aEntry)
{
aTable->FreeStringKey(aEntry);
}
static const PLDHashTableOps stub_ops = {
PL_DHashVoidPtrKeyStub,
PL_DHashMatchEntryStub,
PL_DHashMoveEntryStub,
PL_DHashClearEntryStub,
nullptr
};
const PLDHashTableOps*
PL_DHashGetStubOps(void)
{
return &stub_ops;
}
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
}
static inline uint32_t
MinCapacity(uint32_t aLength)
{
return (aLength * 4 + (3 - 1)) / 3; // == ceil(aLength * 4 / 3)
}
MOZ_ALWAYS_INLINE void
PLDHashTable::Init(const PLDHashTableOps* aOps,
uint32_t aEntrySize, uint32_t aLength)
{
MOZ_ASSERT(!mAutoFinish);
MOZ_ASSERT(!IsInitialized());
// Check that the important fields have been set by the constructor.
MOZ_ASSERT(mOps == nullptr);
MOZ_ASSERT(mRecursionLevel == 0);
MOZ_ASSERT(mEntryStore == nullptr);
if (aLength > PL_DHASH_MAX_INITIAL_LENGTH) {
MOZ_CRASH("Initial length is too large");
}
// Compute the smallest capacity allowing |aLength| elements to be inserted
// without rehashing.
uint32_t capacity = MinCapacity(aLength);
if (capacity < PL_DHASH_MIN_CAPACITY) {
capacity = PL_DHASH_MIN_CAPACITY;
}
int log2 = CeilingLog2(capacity);
capacity = 1u << log2;
MOZ_ASSERT(capacity <= PL_DHASH_MAX_CAPACITY);
mOps = aOps;
mHashShift = PL_DHASH_BITS - log2;
mEntrySize = aEntrySize;
mEntryCount = mRemovedCount = 0;
mGeneration = 0;
uint32_t nbytes;
if (!SizeOfEntryStore(capacity, aEntrySize, &nbytes)) {
MOZ_CRASH("Initial entry store size is too large");
}
mEntryStore = nullptr;
METER(memset(&mStats, 0, sizeof(mStats)));
#ifdef DEBUG
mRecursionLevel = 0;
#endif
}
void
PL_DHashTableInit(PLDHashTable* aTable, const PLDHashTableOps* aOps,
uint32_t aEntrySize, uint32_t aLength)
{
aTable->Init(aOps, aEntrySize, aLength);
}
PLDHashTable::PLDHashTable(const PLDHashTableOps* aOps, uint32_t aEntrySize,
uint32_t aLength)
: mOps(nullptr)
, mAutoFinish(0)
, mEntryStore(nullptr)
#ifdef DEBUG
, mRecursionLevel()
#endif
{
Init(aOps, aEntrySize, aLength);
mAutoFinish = 1;
}
PLDHashTable& PLDHashTable::operator=(PLDHashTable&& aOther)
{
if (this == &aOther) {
return *this;
}
// Destruct |this|.
mAutoFinish = 0;
Finish();
// Move pieces over.
mOps = Move(aOther.mOps);
mHashShift = Move(aOther.mHashShift);
mEntrySize = Move(aOther.mEntrySize);
mEntryCount = Move(aOther.mEntryCount);
mRemovedCount = Move(aOther.mRemovedCount);
// We can't use Move() on bitfields. Fortunately, '=' suffices.
mGeneration = aOther.mGeneration;
mAutoFinish = aOther.mAutoFinish;
mEntryStore = Move(aOther.mEntryStore);
#ifdef PL_DHASHMETER
mStats = Move(aOther.mStats);
#endif
#ifdef DEBUG
// Atomic<> doesn't have an |operator=(Atomic<>&&)|.
mRecursionLevel = uint32_t(aOther.mRecursionLevel);
#endif
// Clear up |aOther| so its destruction will be a no-op.
aOther.mOps = nullptr;
aOther.mEntryStore = nullptr;
#ifdef DEBUG
aOther.mRecursionLevel = 0;
#endif
return *this;
}
/*
* Double hashing needs the second hash code to be relatively prime to table
* size, so we simply make hash2 odd.
*/
#define HASH1(hash0, shift) ((hash0) >> (shift))
#define HASH2(hash0,log2,shift) ((((hash0) << (log2)) >> (shift)) | 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.
*/
#define COLLISION_FLAG ((PLDHashNumber) 1)
#define MARK_ENTRY_FREE(entry) ((entry)->mKeyHash = 0)
#define MARK_ENTRY_REMOVED(entry) ((entry)->mKeyHash = 1)
#define ENTRY_IS_REMOVED(entry) ((entry)->mKeyHash == 1)
#define ENTRY_IS_LIVE(entry) ((entry)->mKeyHash >= 2)
#define ENSURE_LIVE_KEYHASH(hash0) if (hash0 < 2) hash0 -= 2; else (void)0
/* Match an entry's mKeyHash against an unstored one computed from a key. */
#define MATCH_ENTRY_KEYHASH(entry,hash0) \
(((entry)->mKeyHash & ~COLLISION_FLAG) == (hash0))
/* Compute the address of the indexed entry in table. */
#define ADDRESS_ENTRY(table, index) \
((PLDHashEntryHdr *)((table)->mEntryStore + (index) * (table)->mEntrySize))
/* static */ MOZ_ALWAYS_INLINE bool
PLDHashTable::EntryIsFree(PLDHashEntryHdr* aEntry)
{
return aEntry->mKeyHash == 0;
}
MOZ_ALWAYS_INLINE void
PLDHashTable::Finish()
{
MOZ_ASSERT(!mAutoFinish);
if (!IsInitialized()) {
MOZ_ASSERT(!mEntryStore);
return;
}
INCREMENT_RECURSION_LEVEL(this);
/* Clear any remaining live entries. */
char* entryAddr = mEntryStore;
char* entryLimit = entryAddr + Capacity() * mEntrySize;
while (entryAddr < entryLimit) {
PLDHashEntryHdr* entry = (PLDHashEntryHdr*)entryAddr;
if (ENTRY_IS_LIVE(entry)) {
METER(mStats.mRemoveEnums++);
mOps->clearEntry(this, entry);
}
entryAddr += mEntrySize;
}
mOps = nullptr;
DECREMENT_RECURSION_LEVEL(this);
MOZ_ASSERT(RECURSION_LEVEL_SAFE_TO_FINISH(this));
/* Free entry storage last. */
free(mEntryStore);
mEntryStore = nullptr;
}
void
PL_DHashTableFinish(PLDHashTable* aTable)
{
aTable->Finish();
}
PLDHashTable::~PLDHashTable()
{
// If we used automatic initialization, then finalize the table here.
// Otherwise, Finish() should have already been called manually.
if (mAutoFinish) {
mAutoFinish = 0;
Finish();
} else {
// XXX: actually, we can't assert this here because some tables never get
// finalized.
//MOZ_ASSERT(!IsInitialized());
}
}
// 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* PL_DHASH_FASTCALL
PLDHashTable::SearchTable(const void* aKey, PLDHashNumber aKeyHash)
{
MOZ_ASSERT(mEntryStore);
METER(mStats.mSearches++);
NS_ASSERTION(!(aKeyHash & COLLISION_FLAG),
"!(aKeyHash & COLLISION_FLAG)");
/* Compute the primary hash address. */
PLDHashNumber hash1 = HASH1(aKeyHash, mHashShift);
PLDHashEntryHdr* entry = ADDRESS_ENTRY(this, hash1);
/* Miss: return space for a new entry. */
if (EntryIsFree(entry)) {
METER(mStats.mMisses++);
return (Reason == ForAdd) ? entry : nullptr;
}
/* Hit: return entry. */
PLDHashMatchEntry matchEntry = mOps->matchEntry;
if (MATCH_ENTRY_KEYHASH(entry, aKeyHash) &&
matchEntry(this, entry, aKey)) {
METER(mStats.mHits++);
return entry;
}
/* Collision: double hash. */
int sizeLog2 = PL_DHASH_BITS - mHashShift;
PLDHashNumber hash2 = HASH2(aKeyHash, sizeLog2, mHashShift);
uint32_t sizeMask = (1u << sizeLog2) - 1;
/*
* 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(ENTRY_IS_REMOVED(entry))) {
if (!firstRemoved) {
firstRemoved = entry;
}
} else {
entry->mKeyHash |= COLLISION_FLAG;
}
}
METER(mStats.mSteps++);
hash1 -= hash2;
hash1 &= sizeMask;
entry = ADDRESS_ENTRY(this, hash1);
if (EntryIsFree(entry)) {
METER(mStats.mMisses++);
return (Reason == ForAdd) ? (firstRemoved ? firstRemoved : entry)
: nullptr;
}
if (MATCH_ENTRY_KEYHASH(entry, aKeyHash) &&
matchEntry(this, entry, aKey)) {
METER(mStats.mHits++);
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.
*/
PLDHashEntryHdr* PL_DHASH_FASTCALL
PLDHashTable::FindFreeEntry(PLDHashNumber aKeyHash)
{
METER(mStats.mSearches++);
MOZ_ASSERT(mEntryStore);
NS_ASSERTION(!(aKeyHash & COLLISION_FLAG),
"!(aKeyHash & COLLISION_FLAG)");
/* Compute the primary hash address. */
PLDHashNumber hash1 = HASH1(aKeyHash, mHashShift);
PLDHashEntryHdr* entry = ADDRESS_ENTRY(this, hash1);
/* Miss: return space for a new entry. */
if (EntryIsFree(entry)) {
METER(mStats.mMisses++);
return entry;
}
/* Collision: double hash. */
int sizeLog2 = PL_DHASH_BITS - mHashShift;
PLDHashNumber hash2 = HASH2(aKeyHash, sizeLog2, mHashShift);
uint32_t sizeMask = (1u << sizeLog2) - 1;
for (;;) {
NS_ASSERTION(!ENTRY_IS_REMOVED(entry),
"!ENTRY_IS_REMOVED(entry)");
entry->mKeyHash |= COLLISION_FLAG;
METER(mStats.mSteps++);
hash1 -= hash2;
hash1 &= sizeMask;
entry = ADDRESS_ENTRY(this, hash1);
if (EntryIsFree(entry)) {
METER(mStats.mMisses++);
return entry;
}
}
/* NOTREACHED */
return nullptr;
}
bool
PLDHashTable::ChangeTable(int aDeltaLog2)
{
MOZ_ASSERT(mEntryStore);
/* Look, but don't touch, until we succeed in getting new entry store. */
int oldLog2 = PL_DHASH_BITS - mHashShift;
int newLog2 = oldLog2 + aDeltaLog2;
uint32_t newCapacity = 1u << newLog2;
if (newCapacity > PL_DHASH_MAX_CAPACITY) {
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 = PL_DHASH_BITS - newLog2;
mRemovedCount = 0;
mGeneration++;
/* Assign the new entry store to table. */
memset(newEntryStore, 0, nbytes);
char* oldEntryStore;
char* oldEntryAddr;
oldEntryAddr = oldEntryStore = mEntryStore;
mEntryStore = 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 (ENTRY_IS_LIVE(oldEntry)) {
oldEntry->mKeyHash &= ~COLLISION_FLAG;
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);
PLDHashNumber keyHash = mOps->hashKey(this, aKey);
keyHash *= PL_DHASH_GOLDEN_RATIO;
/* Avoid 0 and 1 hash codes, they indicate free and removed entries. */
ENSURE_LIVE_KEYHASH(keyHash);
keyHash &= ~COLLISION_FLAG;
return keyHash;
}
MOZ_ALWAYS_INLINE PLDHashEntryHdr*
PLDHashTable::Search(const void* aKey)
{
MOZ_ASSERT(IsInitialized());
INCREMENT_RECURSION_LEVEL(this);
METER(mStats.mSearches++);
PLDHashEntryHdr* entry =
mEntryStore ? SearchTable<ForSearchOrRemove>(aKey, ComputeKeyHash(aKey))
: nullptr;
DECREMENT_RECURSION_LEVEL(this);
return entry;
}
MOZ_ALWAYS_INLINE PLDHashEntryHdr*
PLDHashTable::Add(const void* aKey, const mozilla::fallible_t&)
{
MOZ_ASSERT(IsInitialized());
PLDHashNumber keyHash;
PLDHashEntryHdr* entry;
uint32_t capacity;
MOZ_ASSERT(mRecursionLevel == 0);
INCREMENT_RECURSION_LEVEL(this);
// Allocate the entry storage if it hasn't already been allocated.
if (!mEntryStore) {
uint32_t nbytes;
// We already checked this in Init(), so it must still be true.
MOZ_RELEASE_ASSERT(SizeOfEntryStore(CapacityFromHashShift(), mEntrySize,
&nbytes));
mEntryStore = (char*)malloc(nbytes);
if (!mEntryStore) {
METER(mStats.mAddFailures++);
entry = nullptr;
goto exit;
}
memset(mEntryStore, 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.
*/
capacity = Capacity();
if (mEntryCount + mRemovedCount >= MaxLoad(capacity)) {
/* Compress if a quarter or more of all entries are removed. */
int deltaLog2;
if (mRemovedCount >= capacity >> 2) {
METER(mStats.mCompresses++);
deltaLog2 = 0;
} else {
METER(mStats.mGrows++);
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)) {
METER(mStats.mAddFailures++);
entry = nullptr;
goto exit;
}
}
/*
* 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.
*/
keyHash = ComputeKeyHash(aKey);
entry = SearchTable<ForAdd>(aKey, keyHash);
if (!ENTRY_IS_LIVE(entry)) {
/* Initialize the entry, indicating that it's no longer free. */
METER(mStats.mAddMisses++);
if (ENTRY_IS_REMOVED(entry)) {
METER(mStats.mAddOverRemoved++);
mRemovedCount--;
keyHash |= COLLISION_FLAG;
}
if (mOps->initEntry) {
mOps->initEntry(entry, aKey);
}
entry->mKeyHash = keyHash;
mEntryCount++;
}
METER(else {
mStats.mAddHits++;
});
exit:
DECREMENT_RECURSION_LEVEL(this);
return entry;
}
MOZ_ALWAYS_INLINE PLDHashEntryHdr*
PLDHashTable::Add(const void* aKey)
{
PLDHashEntryHdr* entry = Add(aKey, fallible);
if (!entry) {
if (!mEntryStore) {
// 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;
}
MOZ_ALWAYS_INLINE void
PLDHashTable::Remove(const void* aKey)
{
MOZ_ASSERT(IsInitialized());
MOZ_ASSERT(mRecursionLevel == 0);
INCREMENT_RECURSION_LEVEL(this);
PLDHashEntryHdr* entry =
mEntryStore ? SearchTable<ForSearchOrRemove>(aKey, ComputeKeyHash(aKey))
: nullptr;
if (entry) {
/* Clear this entry and mark it as "removed". */
METER(mStats.mRemoveHits++);
PL_DHashTableRawRemove(this, entry);
/* Shrink if alpha is <= .25 and the table isn't too small already. */
uint32_t capacity = Capacity();
if (capacity > PL_DHASH_MIN_CAPACITY &&
mEntryCount <= MinLoad(capacity)) {
METER(mStats.mShrinks++);
(void) ChangeTable(-1);
}
}
METER(else {
mStats.mRemoveMisses++;
});
DECREMENT_RECURSION_LEVEL(this);
}
PLDHashEntryHdr* PL_DHASH_FASTCALL
PL_DHashTableSearch(PLDHashTable* aTable, const void* aKey)
{
return aTable->Search(aKey);
}
PLDHashEntryHdr* PL_DHASH_FASTCALL
PL_DHashTableAdd(PLDHashTable* aTable, const void* aKey,
const fallible_t& aFallible)
{
return aTable->Add(aKey, aFallible);
}
PLDHashEntryHdr* PL_DHASH_FASTCALL
PL_DHashTableAdd(PLDHashTable* aTable, const void* aKey)
{
return aTable->Add(aKey);
}
void PL_DHASH_FASTCALL
PL_DHashTableRemove(PLDHashTable* aTable, const void* aKey)
{
aTable->Remove(aKey);
}
MOZ_ALWAYS_INLINE void
PLDHashTable::RawRemove(PLDHashEntryHdr* aEntry)
{
MOZ_ASSERT(IsInitialized());
MOZ_ASSERT(mEntryStore);
MOZ_ASSERT(mRecursionLevel != IMMUTABLE_RECURSION_LEVEL);
NS_ASSERTION(ENTRY_IS_LIVE(aEntry), "ENTRY_IS_LIVE(aEntry)");
/* Load keyHash first in case clearEntry() goofs it. */
PLDHashNumber keyHash = aEntry->mKeyHash;
mOps->clearEntry(this, aEntry);
if (keyHash & COLLISION_FLAG) {
MARK_ENTRY_REMOVED(aEntry);
mRemovedCount++;
} else {
METER(mStats.mRemoveFrees++);
MARK_ENTRY_FREE(aEntry);
}
mEntryCount--;
}
void
PL_DHashTableRawRemove(PLDHashTable* aTable, PLDHashEntryHdr* aEntry)
{
aTable->RawRemove(aEntry);
}
MOZ_ALWAYS_INLINE uint32_t
PLDHashTable::Enumerate(PLDHashEnumerator aEtor, void* aArg)
{
MOZ_ASSERT(IsInitialized());
if (!mEntryStore) {
return 0;
}
INCREMENT_RECURSION_LEVEL(this);
// Please keep this method in sync with the PLDHashTable::Iterator constructor
// and ::NextEntry methods below in this file.
char* entryAddr = mEntryStore;
uint32_t capacity = Capacity();
uint32_t tableSize = capacity * mEntrySize;
char* entryLimit = entryAddr + tableSize;
uint32_t i = 0;
bool didRemove = false;
if (ChaosMode::isActive(ChaosMode::HashTableIteration)) {
// Start iterating at a random point in the hashtable. It would be
// even more chaotic to iterate in fully random order, but that's a lot
// more work.
entryAddr += ChaosMode::randomUint32LessThan(capacity) * mEntrySize;
if (entryAddr >= entryLimit) {
entryAddr -= tableSize;
}
}
for (uint32_t e = 0; e < capacity; ++e) {
PLDHashEntryHdr* entry = (PLDHashEntryHdr*)entryAddr;
if (ENTRY_IS_LIVE(entry)) {
PLDHashOperator op = aEtor(this, entry, i++, aArg);
if (op & PL_DHASH_REMOVE) {
METER(mStats.mRemoveEnums++);
PL_DHashTableRawRemove(this, entry);
didRemove = true;
}
if (op & PL_DHASH_STOP) {
break;
}
}
entryAddr += mEntrySize;
if (entryAddr >= entryLimit) {
entryAddr -= tableSize;
}
}
MOZ_ASSERT(!didRemove || mRecursionLevel == 1);
/*
* 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. Do this only if we removed above, so non-removing
* enumerations can count on stable |mEntryStore| until the next
* Add, Remove, or removing-Enumerate.
*/
if (didRemove &&
(mRemovedCount >= capacity >> 2 ||
(capacity > PL_DHASH_MIN_CAPACITY &&
mEntryCount <= MinLoad(capacity)))) {
METER(mStats.mEnumShrinks++);
capacity = mEntryCount;
capacity += capacity >> 1;
if (capacity < PL_DHASH_MIN_CAPACITY) {
capacity = PL_DHASH_MIN_CAPACITY;
}
uint32_t ceiling = CeilingLog2(capacity);
ceiling -= PL_DHASH_BITS - mHashShift;
(void) ChangeTable(ceiling);
}
DECREMENT_RECURSION_LEVEL(this);
return i;
}
uint32_t
PL_DHashTableEnumerate(PLDHashTable* aTable, PLDHashEnumerator aEtor,
void* aArg)
{
return aTable->Enumerate(aEtor, aArg);
}
struct SizeOfEntryExcludingThisArg
{
size_t total;
PLDHashSizeOfEntryExcludingThisFun sizeOfEntryExcludingThis;
MallocSizeOf mallocSizeOf;
void* arg; // the arg passed by the user
};
static PLDHashOperator
SizeOfEntryExcludingThisEnumerator(PLDHashTable* aTable, PLDHashEntryHdr* aHdr,
uint32_t aNumber, void* aArg)
{
SizeOfEntryExcludingThisArg* e = (SizeOfEntryExcludingThisArg*)aArg;
e->total += e->sizeOfEntryExcludingThis(aHdr, e->mallocSizeOf, e->arg);
return PL_DHASH_NEXT;
}
MOZ_ALWAYS_INLINE size_t
PLDHashTable::SizeOfExcludingThis(
PLDHashSizeOfEntryExcludingThisFun aSizeOfEntryExcludingThis,
MallocSizeOf aMallocSizeOf, void* aArg /* = nullptr */) const
{
MOZ_ASSERT(IsInitialized());
if (!mEntryStore) {
return 0;
}
size_t n = 0;
n += aMallocSizeOf(mEntryStore);
if (aSizeOfEntryExcludingThis) {
SizeOfEntryExcludingThisArg arg2 = {
0, aSizeOfEntryExcludingThis, aMallocSizeOf, aArg
};
PL_DHashTableEnumerate(const_cast<PLDHashTable*>(this),
SizeOfEntryExcludingThisEnumerator, &arg2);
n += arg2.total;
}
return n;
}
MOZ_ALWAYS_INLINE size_t
PLDHashTable::SizeOfIncludingThis(
PLDHashSizeOfEntryExcludingThisFun aSizeOfEntryExcludingThis,
MallocSizeOf aMallocSizeOf, void* aArg /* = nullptr */) const
{
MOZ_ASSERT(IsInitialized());
return aMallocSizeOf(this) +
SizeOfExcludingThis(aSizeOfEntryExcludingThis, aMallocSizeOf, aArg);
}
size_t
PL_DHashTableSizeOfExcludingThis(
const PLDHashTable* aTable,
PLDHashSizeOfEntryExcludingThisFun aSizeOfEntryExcludingThis,
MallocSizeOf aMallocSizeOf, void* aArg /* = nullptr */)
{
return aTable->SizeOfExcludingThis(aSizeOfEntryExcludingThis,
aMallocSizeOf, aArg);
}
size_t
PL_DHashTableSizeOfIncludingThis(
const PLDHashTable* aTable,
PLDHashSizeOfEntryExcludingThisFun aSizeOfEntryExcludingThis,
MallocSizeOf aMallocSizeOf, void* aArg /* = nullptr */)
{
return aTable->SizeOfIncludingThis(aSizeOfEntryExcludingThis,
aMallocSizeOf, aArg);
}
PLDHashTable::Iterator::Iterator(const PLDHashTable* aTable)
: mTable(aTable),
mEntryAddr(mTable->mEntryStore),
mEntryOffset(0)
{
MOZ_ASSERT(mTable->IsInitialized());
// Make sure that modifications can't simultaneously happen while the iterator
// is active.
INCREMENT_RECURSION_LEVEL(mTable);
// The following code is taken from, and should be kept in sync with, the
// PLDHashTable::Enumerate method above. The variables i and entryAddr (which
// vary over the course of the for loop) are converted into mEntryOffset and
// mEntryAddr, respectively.
uint32_t capacity = mTable->Capacity();
uint32_t tableSize = capacity * mTable->EntrySize();
char* entryLimit = mEntryAddr + tableSize;
if (ChaosMode::isActive(ChaosMode::HashTableIteration)) {
// Start iterating at a random point in the hashtable. It would be
// even more chaotic to iterate in fully random order, but that's a lot
// more work.
mEntryAddr += ChaosMode::randomUint32LessThan(capacity) * mTable->mEntrySize;
if (mEntryAddr >= entryLimit) {
mEntryAddr -= tableSize;
}
}
}
PLDHashTable::Iterator::Iterator(const Iterator& aIterator)
: mTable(aIterator.mTable),
mEntryAddr(aIterator.mEntryAddr),
mEntryOffset(aIterator.mEntryOffset)
{
MOZ_ASSERT(mTable->IsInitialized());
// We need the copy constructor only so that we can keep the recursion level
// consistent.
INCREMENT_RECURSION_LEVEL(mTable);
}
PLDHashTable::Iterator::~Iterator()
{
MOZ_ASSERT(mTable->IsInitialized());
DECREMENT_RECURSION_LEVEL(mTable);
}
bool PLDHashTable::Iterator::HasMoreEntries() const
{
MOZ_ASSERT(mTable->IsInitialized());
// Check the number of live entries seen, not the total number of entries
// seen. To see why, consider what happens if the last entry is not live: we
// would have to iterate after returning an entry to see if more live entries
// exist.
return mEntryOffset < mTable->EntryCount();
}
PLDHashEntryHdr* PLDHashTable::Iterator::NextEntry()
{
MOZ_ASSERT(HasMoreEntries());
// The following code is taken from, and should be kept in sync with, the
// PLDHashTable::Enumerate method above. The variables i and entryAddr (which
// vary over the course of the for loop) are converted into mEntryOffset and
// mEntryAddr, respectively.
uint32_t capacity = mTable->Capacity();
uint32_t tableSize = capacity * mTable->mEntrySize;
char* entryLimit = mEntryAddr + tableSize;
// Strictly speaking, we don't need to iterate over the full capacity each
// time. However, it is simpler to do so rather than unnecessarily track the
// current number of entries checked as opposed to only live entries. If debug
// checks pass, then this method will only iterate through the full capacity
// once. If they fail, then this loop may end up returning the early entries
// more than once.
MOZ_ASSERT_IF(capacity > 0, mTable->mEntryStore);
for (uint32_t e = 0; e < capacity; ++e) {
PLDHashEntryHdr* entry = (PLDHashEntryHdr*)mEntryAddr;
// Increment the count before returning so we don't keep returning the same
// address. This may wrap around if ChaosMode is enabled.
mEntryAddr += mTable->mEntrySize;
if (mEntryAddr >= entryLimit) {
mEntryAddr -= tableSize;
}
if (ENTRY_IS_LIVE(entry)) {
++mEntryOffset;
return entry;
}
}
// If the debug checks pass, then the above loop should always find a live
// entry. If those checks are disabled, then it may be possible to reach this
// if the table is empty and this method is called.
MOZ_CRASH("Flagrant misuse of hashtable iterators not caught by checks.");
}
#ifdef DEBUG
MOZ_ALWAYS_INLINE void
PLDHashTable::MarkImmutable()
{
MOZ_ASSERT(IsInitialized());
mRecursionLevel = IMMUTABLE_RECURSION_LEVEL;
}
void
PL_DHashMarkTableImmutable(PLDHashTable* aTable)
{
aTable->MarkImmutable();
}
#endif
#ifdef PL_DHASHMETER
#include <math.h>
void
PLDHashTable::DumpMeter(PLDHashEnumerator aDump, FILE* aFp)
{
MOZ_ASSERT(IsInitialized());
PLDHashNumber hash1, hash2, maxChainHash1, maxChainHash2;
double sqsum, mean, variance, sigma;
PLDHashEntryHdr* entry;
char* entryAddr = mEntryStore;
int sizeLog2 = PL_DHASH_BITS - mHashShift;
uint32_t capacity = Capacity();
uint32_t sizeMask = (1u << sizeLog2) - 1;
uint32_t chainCount = 0, maxChainLen = 0;
hash2 = 0;
sqsum = 0;
MOZ_ASSERT_IF(capacity > 0, mEntryStore);
for (uint32_t i = 0; i < capacity; i++) {
entry = (PLDHashEntryHdr*)entryAddr;
entryAddr += mEntrySize;
if (!ENTRY_IS_LIVE(entry)) {
continue;
}
hash1 = HASH1(entry->mKeyHash & ~COLLISION_FLAG, mHashShift);
PLDHashNumber saveHash1 = hash1;
PLDHashEntryHdr* probe = ADDRESS_ENTRY(this, hash1);
uint32_t chainLen = 1;
if (probe == entry) {
/* Start of a (possibly unit-length) chain. */
chainCount++;
} else {
hash2 = HASH2(entry->mKeyHash & ~COLLISION_FLAG, sizeLog2, mHashShift);
do {
chainLen++;
hash1 -= hash2;
hash1 &= sizeMask;
probe = ADDRESS_ENTRY(this, hash1);
} while (probe != entry);
}
sqsum += chainLen * chainLen;
if (chainLen > maxChainLen) {
maxChainLen = chainLen;
maxChainHash1 = saveHash1;
maxChainHash2 = hash2;
}
}
if (mEntryCount && chainCount) {
mean = (double)mEntryCount / chainCount;
variance = chainCount * sqsum - mEntryCount * mEntryCount;
if (variance < 0 || chainCount == 1) {
variance = 0;
} else {
variance /= chainCount * (chainCount - 1);
}
sigma = sqrt(variance);
} else {
mean = sigma = 0;
}
fprintf(aFp, "Double hashing statistics:\n");
fprintf(aFp, " capacity (in entries): %u\n", Capacity());
fprintf(aFp, " number of entries: %u\n", mEntryCount);
fprintf(aFp, " number of removed entries: %u\n", mRemovedCount);
fprintf(aFp, " number of searches: %u\n", mStats.mSearches);
fprintf(aFp, " number of hits: %u\n", mStats.mHits);
fprintf(aFp, " number of misses: %u\n", mStats.mMisses);
fprintf(aFp, " mean steps per search: %g\n",
mStats.mSearches ? (double)mStats.mSteps / mStats.mSearches : 0.);
fprintf(aFp, " mean hash chain length: %g\n", mean);
fprintf(aFp, " standard deviation: %g\n", sigma);
fprintf(aFp, " maximum hash chain length: %u\n", maxChainLen);
fprintf(aFp, " number of searches: %u\n", mStats.mSearches);
fprintf(aFp, " adds that made a new entry: %u\n", mStats.mAddMisses);
fprintf(aFp, "adds that recycled removeds: %u\n", mStats.mAddOverRemoved);
fprintf(aFp, " adds that found an entry: %u\n", mStats.mAddHits);
fprintf(aFp, " add failures: %u\n", mStats.mAddFailures);
fprintf(aFp, " useful removes: %u\n", mStats.mRemoveHits);
fprintf(aFp, " useless removes: %u\n", mStats.mRemoveMisses);
fprintf(aFp, "removes that freed an entry: %u\n", mStats.mRemoveFrees);
fprintf(aFp, " removes while enumerating: %u\n", mStats.mRemoveEnums);
fprintf(aFp, " number of grows: %u\n", mStats.mGrows);
fprintf(aFp, " number of shrinks: %u\n", mStats.mShrinks);
fprintf(aFp, " number of compresses: %u\n", mStats.mCompresses);
fprintf(aFp, "number of enumerate shrinks: %u\n", mStats.mEnumShrinks);
if (aDump && maxChainLen && hash2) {
fputs("Maximum hash chain:\n", aFp);
hash1 = maxChainHash1;
hash2 = maxChainHash2;
entry = ADDRESS_ENTRY(this, hash1);
uint32_t i = 0;
do {
if (aDump(this, entry, i++, aFp) != PL_DHASH_NEXT) {
break;
}
hash1 -= hash2;
hash1 &= sizeMask;
entry = ADDRESS_ENTRY(this, hash1);
} while (!EntryIsFree(entry));
}
}
void
PL_DHashTableDumpMeter(PLDHashTable* aTable, PLDHashEnumerator aDump, FILE* aFp)
{
aTable->DumpMeter(aDump, aFp);
}
#endif /* PL_DHASHMETER */
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