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gecko/js/src/jshashtable.h
Jeff Walden 53b100ce6f Typo fix, r=waylon
2010-02-22 19:43:41 -08:00

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sw=4 et tw=99 ft=cpp:
*
* ***** 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 SpiderMonkey JavaScript 1.9 code, released
* November 13, 2009.
*
* The Initial Developer of the Original Code is
* the Mozilla Corporation.
*
* Contributor(s):
* Brendan Eich <brendan@mozilla.org> (Original Author)
* Chris Waterson <waterson@netscape.com>
* L. David Baron <dbaron@dbaron.org>, Mozilla Corporation
* Luke Wagner <lw@mozilla.com>
*
* 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 jshashtable_h_
#define jshashtable_h_
#include "jstl.h"
namespace js {
/* Integral types for all hash functions. */
typedef uint32 HashNumber;
namespace detail {
/* Reusable implementation of HashMap and HashSet. */
template <class T, class HashPolicy, class AllocPolicy>
class HashTable : AllocPolicy
{
typedef typename tl::StripConst<T>::result NonConstT;
typedef typename HashPolicy::KeyType Key;
typedef typename HashPolicy::Lookup Lookup;
/*
* T::operator= is a private operation for HashMap::Entry. HashMap::Entry
* makes HashTable a friend, but MSVC does not allow HashMap::Entry to make
* HashTable::Entry a friend. So do assignment here:
*/
static void assignT(NonConstT &dst, const T &src) { dst = src; }
public:
class Entry {
HashNumber keyHash;
public:
Entry() : keyHash(0), t() {}
void operator=(const Entry &rhs) { keyHash = rhs.keyHash; assignT(t, rhs.t); }
NonConstT t;
bool isFree() const { return keyHash == 0; }
void setFree() { keyHash = 0; assignT(t, T()); }
bool isRemoved() const { return keyHash == 1; }
void setRemoved() { keyHash = 1; assignT(t, T()); }
bool isLive() const { return keyHash > 1; }
void setLive(HashNumber hn) { JS_ASSERT(hn > 1); keyHash = hn; }
void setCollision() { JS_ASSERT(keyHash > 1); keyHash |= sCollisionBit; }
void unsetCollision() { JS_ASSERT(keyHash > 1); keyHash &= ~sCollisionBit; }
bool hasCollision() const { JS_ASSERT(keyHash > 1); return keyHash & sCollisionBit; }
bool matchHash(HashNumber hn) { return (keyHash & ~sCollisionBit) == hn; }
HashNumber getKeyHash() const { JS_ASSERT(!hasCollision()); return keyHash; }
};
/*
* A nullable pointer to a hash table element. A Ptr |p| can be tested
* either explicitly |if (p.found()) p->...| or using boolean conversion
* |if (p) p->...|. Ptr objects must not be used after any mutating hash
* table operations unless |generation()| is tested.
*/
class Ptr
{
friend class HashTable;
typedef void (Ptr::* ConvertibleToBool)();
void nonNull() {}
Entry *entry;
protected:
Ptr(Entry &entry) : entry(&entry) {}
public:
bool found() const { return entry->isLive(); }
operator ConvertibleToBool() const { return found() ? &Ptr::nonNull : 0; }
bool operator==(const Ptr &rhs) const { JS_ASSERT(found() && rhs.found()); return entry == rhs.entry; }
bool operator!=(const Ptr &rhs) const { return !(*this == rhs); }
T &operator*() const { return entry->t; }
T *operator->() const { return &entry->t; }
};
/* A Ptr that can be used to add a key after a failed lookup. */
class AddPtr : public Ptr
{
friend class HashTable;
AddPtr(Entry &entry, HashNumber hn) : Ptr(entry), keyHash(hn) {}
HashNumber keyHash;
};
/*
* A collection of hash table entries. The collection is enumerated by
* calling |front()| followed by |popFront()| as long as |!empty()|. As
* with Ptr/AddPtr, Range objects must not be used after any mutating hash
* table operation unless the |generation()| is tested.
*/
class Range
{
protected:
friend class HashTable;
Range(Entry *c, Entry *e) : cur(c), end(e) {
while (cur != end && !cur->isLive())
++cur;
}
Entry *cur, *end;
public:
bool empty() const {
return cur == end;
}
const T &front() const {
JS_ASSERT(!empty());
return cur->t;
}
void popFront() {
JS_ASSERT(!empty());
while (++cur != end && !cur->isLive());
}
};
/*
* A Range whose lifetime delimits a mutating enumeration of a hash table.
* Since rehashing when elements were removed during enumeration would be
* bad, it is postponed until |endEnumeration()| is called. If
* |endEnumeration()| is not called before an Enum's constructor, it will
* be called automatically. Since |endEnumeration()| touches the hash
* table, the user must ensure that the hash table is still alive when this
* happens.
*/
class Enum : public Range
{
friend class HashTable;
HashTable &table;
bool removed;
/* Not copyable. */
Enum(const Enum &);
void operator=(const Enum &);
public:
template<class Map>
Enum(Map &map) : Range(map.all()), table(map.impl), removed(false) {}
/*
* Removes the |front()| element from the table, leaving |front()|
* invalid until the next call to |popFront()|. For example:
*
* HashSet<int> s;
* for (HashSet<int>::Enum e(s); !e.empty(); e.popFront())
* if (e.front() == 42)
* e.removeFront();
*/
void removeFront() {
table.remove(*this->cur);
removed = true;
}
/* Potentially rehashes the table. */
~Enum() {
if (removed)
table.checkUnderloaded();
}
/* Can be used to end the enumeration before the destructor. */
void endEnumeration() {
if (removed) {
table.checkUnderloaded();
removed = false;
}
}
};
private:
uint32 hashShift; /* multiplicative hash shift */
uint32 tableCapacity; /* = JS_BIT(sHashBits - hashShift) */
uint32 entryCount; /* number of entries in table */
uint32 gen; /* entry storage generation number */
uint32 removedCount; /* removed entry sentinels in table */
Entry *table; /* entry storage */
void setTableSizeLog2(unsigned sizeLog2) {
hashShift = sHashBits - sizeLog2;
tableCapacity = JS_BIT(sizeLog2);
}
#ifdef DEBUG
mutable struct Stats {
uint32 searches; /* total number of table searches */
uint32 steps; /* hash chain links traversed */
uint32 hits; /* searches that found key */
uint32 misses; /* searches that didn't find key */
uint32 addOverRemoved; /* adds that recycled a removed entry */
uint32 removes; /* calls to remove */
uint32 removeFrees; /* calls to remove that freed the entry */
uint32 grows; /* table expansions */
uint32 shrinks; /* table contractions */
uint32 compresses; /* table compressions */
} stats;
# define METER(x) x
#else
# define METER(x)
#endif
#ifdef DEBUG
friend class js::ReentrancyGuard;
mutable bool entered;
#endif
static const unsigned sMinSizeLog2 = 4;
static const unsigned sMinSize = 1 << sMinSizeLog2;
static const unsigned sSizeLimit = JS_BIT(24);
static const unsigned sHashBits = tl::BitSize<HashNumber>::result;
static const unsigned sGoldenRatio = 0x9E3779B9U; /* taken from jsdhash.h */
static const uint8 sMinAlphaFrac = 64; /* (0x100 * .25) taken from jsdhash.h */
static const uint8 sMaxAlphaFrac = 192; /* (0x100 * .75) taken from jsdhash.h */
static const unsigned sCollisionBit = 1;
static Entry *createTable(AllocPolicy &alloc, uint32 capacity)
{
Entry *newTable = (Entry *)alloc.malloc(capacity * sizeof(Entry));
if (!newTable)
return NULL;
for (Entry *e = newTable, *end = e + capacity; e != end; ++e)
new(e) Entry();
return newTable;
}
static void destroyTable(AllocPolicy &alloc, Entry *oldTable, uint32 capacity)
{
for (Entry *e = oldTable, *end = e + capacity; e != end; ++e)
e->~Entry();
alloc.free(oldTable);
}
public:
HashTable(AllocPolicy ap)
: AllocPolicy(ap),
entryCount(0),
gen(0),
removedCount(0),
table(NULL)
#ifdef DEBUG
, entered(false)
#endif
{}
bool init(uint32 capacity)
{
if (capacity < sMinSize)
capacity = sMinSize;
/* FIXME: use JS_CEILING_LOG2 when PGO stops crashing (bug 543034). */
JS_ASSERT(capacity < (uint32(1) << 31));
uint32 roundUp = sMinSize, roundUpLog2 = sMinSizeLog2;
while (roundUp < capacity) {
roundUp <<= 1;
++roundUpLog2;
}
capacity = roundUp;
if (capacity >= sSizeLimit)
return false;
table = createTable(*this, capacity);
if (!table)
return false;
setTableSizeLog2(roundUpLog2);
METER(memset(&stats, 0, sizeof(stats)));
return true;
}
~HashTable()
{
if (table)
destroyTable(*this, table, tableCapacity);
}
private:
static uint32 hash1(uint32 hash0, uint32 shift) {
return hash0 >> shift;
}
static uint32 hash2(uint32 hash0, uint32 log2, uint32 shift) {
return ((hash0 << log2) >> shift) | 1;
}
bool overloaded() {
return entryCount + removedCount >= ((sMaxAlphaFrac * tableCapacity) >> 8);
}
bool underloaded() {
return tableCapacity > sMinSize &&
entryCount <= ((sMinAlphaFrac * tableCapacity) >> 8);
}
static bool match(Entry &e, const Lookup &l) {
return HashPolicy::match(HashPolicy::getKey(e.t), l);
}
struct SetCollisions {
static void collide(Entry &e) { e.setCollision(); }
};
struct IgnoreCollisions {
static void collide(Entry &) {}
};
template <class Op>
AddPtr lookup(const Lookup &l, HashNumber keyHash) const
{
JS_ASSERT(table);
METER(stats.searches++);
/* Improve keyHash distribution. */
keyHash *= sGoldenRatio;
/* Avoid reserved hash codes. */
if (keyHash < 2)
keyHash -= 2;
keyHash &= ~sCollisionBit;
/* Compute the primary hash address. */
uint32 h1 = hash1(keyHash, hashShift);
Entry *entry = &table[h1];
/* Miss: return space for a new entry. */
if (entry->isFree()) {
METER(stats.misses++);
return AddPtr(*entry, keyHash);
}
/* Hit: return entry. */
if (entry->matchHash(keyHash) && match(*entry, l)) {
METER(stats.hits++);
return AddPtr(*entry, keyHash);
}
/* Collision: double hash. */
unsigned sizeLog2 = sHashBits - hashShift;
uint32 h2 = hash2(keyHash, sizeLog2, hashShift);
uint32 sizeMask = JS_BITMASK(sizeLog2);
/* Save the first removed entry pointer so we can recycle later. */
Entry *firstRemoved = NULL;
while(true) {
if (JS_UNLIKELY(entry->isRemoved())) {
if (!firstRemoved)
firstRemoved = entry;
} else {
Op::collide(*entry);
}
METER(stats.steps++);
h1 -= h2;
h1 &= sizeMask;
entry = &table[h1];
if (entry->isFree()) {
METER(stats.misses++);
return AddPtr(*(firstRemoved ? firstRemoved : entry), keyHash);
}
if (entry->matchHash(keyHash) && match(*entry, l)) {
METER(stats.hits++);
return AddPtr(*entry, keyHash);
}
}
}
/*
* This is a copy of lookup hardcoded to the assumptions:
* 1. the lookup is a lookupForAdd
* 2. the key, whose |keyHash| has been passed is not in the table,
* 3. no entries have been removed from the table.
* This specialized search avoids the need for recovering lookup values
* from entries, which allows more flexible Lookup/Key types.
*/
Entry &findFreeEntry(HashNumber keyHash)
{
METER(stats.searches++);
JS_ASSERT(!(keyHash & sCollisionBit));
/* N.B. the |keyHash| has already been distributed. */
/* Compute the primary hash address. */
uint32 h1 = hash1(keyHash, hashShift);
Entry *entry = &table[h1];
/* Miss: return space for a new entry. */
if (entry->isFree()) {
METER(stats.misses++);
return *entry;
}
/* Collision: double hash. */
unsigned sizeLog2 = sHashBits - hashShift;
uint32 h2 = hash2(keyHash, sizeLog2, hashShift);
uint32 sizeMask = JS_BITMASK(sizeLog2);
while(true) {
JS_ASSERT(!entry->isRemoved());
entry->setCollision();
METER(stats.steps++);
h1 -= h2;
h1 &= sizeMask;
entry = &table[h1];
if (entry->isFree()) {
METER(stats.misses++);
return *entry;
}
}
}
bool changeTableSize(int deltaLog2)
{
/* Look, but don't touch, until we succeed in getting new entry store. */
Entry *oldTable = table;
uint32 oldCap = tableCapacity;
uint32 newLog2 = sHashBits - hashShift + deltaLog2;
uint32 newCapacity = JS_BIT(newLog2);
if (newCapacity >= sSizeLimit)
return false;
Entry *newTable = createTable(*this, newCapacity);
if (!newTable)
return false;
/* We can't fail from here on, so update table parameters. */
setTableSizeLog2(newLog2);
removedCount = 0;
gen++;
table = newTable;
/* Copy only live entries, leaving removed ones behind. */
for (Entry *src = oldTable, *end = src + oldCap; src != end; ++src) {
if (src->isLive()) {
src->unsetCollision();
findFreeEntry(src->getKeyHash()) = *src;
}
}
destroyTable(*this, oldTable, oldCap);
return true;
}
void remove(Entry &e)
{
METER(stats.removes++);
if (e.hasCollision()) {
e.setRemoved();
removedCount++;
} else {
METER(stats.removeFrees++);
e.setFree();
}
entryCount--;
}
void checkUnderloaded()
{
if (underloaded()) {
METER(stats.shrinks++);
(void) changeTableSize(-1);
}
}
public:
void clear()
{
for (Entry *e = table, *end = table + tableCapacity; e != end; ++e)
*e = Entry();
removedCount = 0;
entryCount = 0;
}
Range all() const {
return Range(table, table + tableCapacity);
}
bool empty() const {
return !entryCount;
}
uint32 count() const{
return entryCount;
}
uint32 generation() const {
return gen;
}
Ptr lookup(const Lookup &l) const {
ReentrancyGuard g(*this);
return lookup<IgnoreCollisions>(l, HashPolicy::hash(l));
}
AddPtr lookupForAdd(const Lookup &l) const {
ReentrancyGuard g(*this);
return lookup<SetCollisions>(l, HashPolicy::hash(l));
}
bool add(AddPtr &p, const T &t)
{
ReentrancyGuard g(*this);
JS_ASSERT(table);
JS_ASSERT(!p.found());
JS_ASSERT(!(p.keyHash & sCollisionBit));
/*
* Changing an entry from removed to live does not affect whether we
* are overloaded and can be handled separately.
*/
if (p.entry->isRemoved()) {
METER(stats.addOverRemoved++);
removedCount--;
p.keyHash |= sCollisionBit;
} else {
/* If alpha is >= .75, grow or compress the table. */
if (overloaded()) {
/* Compress if a quarter or more of all entries are removed. */
int deltaLog2;
if (removedCount >= (tableCapacity >> 2)) {
METER(stats.compresses++);
deltaLog2 = 0;
} else {
METER(stats.grows++);
deltaLog2 = 1;
}
if (!changeTableSize(deltaLog2))
return false;
/* Preserve the validity of |p.entry|. */
p.entry = &findFreeEntry(p.keyHash);
}
}
p.entry->t = t;
p.entry->setLive(p.keyHash);
entryCount++;
return true;
}
void remove(Ptr p)
{
ReentrancyGuard g(*this);
JS_ASSERT(p.found());
remove(*p.entry);
checkUnderloaded();
}
#undef METER
};
}
/*
* Hash policy
*
* A hash policy P for a hash table with key-type Key must provide:
* - a type |P::Lookup| to use to lookup table entries;
* - a static member function |P::hash| with signature
*
* static js::HashNumber hash(Lookup)
*
* to use to hash the lookup type; and
* - a static member function |P::match| with signature
*
* static bool match(Key, Lookup)
*
* to use to test equality of key and lookup values.
*
* Normally, Lookup = Key. In general, though, different values and types of
* values can be used to lookup and store. If a Lookup value |l| is != to the
* added Key value |k|, the user must ensure that |P::match(k,l)|. E.g.:
*
* js::HashSet<Key, P>::AddPtr p = h.lookup(l);
* if (!p) {
* assert(P::match(k, l)); // must hold
* h.add(p, k);
* }
*/
/* Default hashing policies. */
template <class Key>
struct DefaultHasher
{
typedef Key Lookup;
static uint32 hash(const Lookup &l) {
/* Hash if can implicitly cast to hash number type. */
return l;
}
static bool match(const Key &k, const Lookup &l) {
/* Use builtin or overloaded operator==. */
return k == l;
}
};
/* Specialized hashing policy for pointer types. */
template <class T>
struct DefaultHasher<T *>
{
typedef T *Lookup;
static uint32 hash(T *l) {
/*
* Strip often-0 lower bits for better distribution after multiplying
* by the sGoldenRatio.
*/
return (uint32)(unsigned long)l >> 2;
}
static bool match(T *k, T *l) {
return k == l;
}
};
/*
* JS-friendly, STL-like container providing a hash-based map from keys to
* values. In particular, HashMap calls constructors and destructors of all
* objects added so non-PODs may be used safely.
*
* Key/Value requirements:
* - default constructible, copyable, destructible, assignable
* HashPolicy requirements:
* - see "Hash policy" above (default js::DefaultHasher<Key>)
* AllocPolicy:
* - see "Allocation policies" in jstl.h (default js::ContextAllocPolicy)
*
* N.B: HashMap is not reentrant: Key/Value/HashPolicy/AllocPolicy members
* called by HashMap must not call back into the same HashMap object.
* N.B: Due to the lack of exception handling, the user must call |init()|.
*/
template <class Key, class Value, class HashPolicy, class AllocPolicy>
class HashMap
{
public:
typedef typename HashPolicy::Lookup Lookup;
class Entry
{
template <class, class, class> friend class detail::HashTable;
void operator=(const Entry &rhs) {
const_cast<Key &>(key) = rhs.key;
value = rhs.value;
}
public:
Entry() : key(), value() {}
Entry(const Key &k, const Value &v) : key(k), value(v) {}
const Key key;
Value value;
};
private:
/* Implement HashMap using HashTable. Lift |Key| operations to |Entry|. */
struct MapHashPolicy : HashPolicy
{
typedef Key KeyType;
static const Key &getKey(Entry &e) { return e.key; }
};
typedef detail::HashTable<Entry, MapHashPolicy, AllocPolicy> Impl;
friend class Impl::Enum;
/* Not implicitly copyable (expensive). May add explicit |clone| later. */
HashMap(const HashMap &);
HashMap &operator=(const HashMap &);
Impl impl;
public:
/*
* HashMap construction is fallible (due to OOM); thus the user must call
* init after constructing a HashMap and check the return value.
*/
HashMap(AllocPolicy a = AllocPolicy()) : impl(a) {}
bool init(uint32 cap = 0) { return impl.init(cap); }
/*
* Return whether the given lookup value is present in the map. E.g.:
*
* typedef HashMap<int,char> HM;
* HM h;
* if (HM::Ptr p = h.lookup(3)) {
* const HM::Entry &e = *p; // p acts like a pointer to Entry
* assert(p->key == 3); // Entry contains the key
* char val = p->value; // and value
* }
*
* Also see the definition of Ptr in HashTable above (with T = Entry).
*/
typedef typename Impl::Ptr Ptr;
Ptr lookup(const Lookup &l) const { return impl.lookup(l); }
/* Assuming |p.found()|, remove |*p|. */
void remove(Ptr p) { impl.remove(p); }
/*
* Like |lookup(l)|, but on miss, |p = lookupForAdd(l)| allows efficient
* insertion of Key |k| (where |HashPolicy::match(k,l) == true|) using
* |add(p,k,v)|. After |add(p,k,v)|, |p| points to the new Entry. E.g.:
*
* typedef HashMap<int,char> HM;
* HM h;
* HM::AddPtr p = h.lookupForAdd(3);
* if (!p) {
* if (!h.add(p, 3, 'a'))
* return false;
* }
* const HM::Entry &e = *p; // p acts like a pointer to Entry
* assert(p->key == 3); // Entry contains the key
* char val = p->value; // and value
*
* Also see the definition of AddPtr in HashTable above (with T = Entry).
*/
typedef typename Impl::AddPtr AddPtr;
AddPtr lookupForAdd(const Lookup &l) const { return impl.lookupForAdd(l); }
bool add(AddPtr &p, const Key &k, const Value &v) { return impl.add(p,Entry(k,v)); }
/*
* |all()| returns a Range containing |count()| elements. E.g.:
*
* typedef HashMap<int,char> HM;
* HM h;
* for (HM::Range r = h.all(); !r.empty(); r.popFront())
* char c = r.front().value;
*
* Also see the definition of Range in HashTable above (with T = Entry).
*/
typedef typename Impl::Range Range;
Range all() const { return impl.all(); }
size_t count() const { return impl.count(); }
/*
* Typedef for the enumeration class. An Enum may be used to examine and
* remove table entries:
*
* typedef HashMap<int,char> HM;
* HM s;
* for (HM::Enum e(s); !e.empty(); e.popFront())
* if (e.front().value == 'l')
* e.removeFront();
*
* Table resize may occur in Enum's destructor. Also see the definition of
* Enum in HashTable above (with T = Entry).
*/
typedef typename Impl::Enum Enum;
/* Remove all entries. */
void clear() { impl.clear(); }
/* Does the table contain any entries? */
bool empty() const { return impl.empty(); }
/*
* If |generation()| is the same before and after a HashMap operation,
* pointers into the table remain valid.
*/
unsigned generation() const { return impl.generation(); }
/* Shorthand operations: */
bool has(const Lookup &l) const {
return impl.lookup(l) != NULL;
}
Entry *put(const Key &k, const Value &v) {
AddPtr p = lookupForAdd(k);
if (p) {
p->value = v;
return &*p;
}
return add(p, k, v) ? &*p : NULL;
}
void remove(const Lookup &l) {
if (Ptr p = lookup(l))
remove(p);
}
};
/*
* JS-friendly, STL-like container providing a hash-based set of values. In
* particular, HashSet calls constructors and destructors of all objects added
* so non-PODs may be used safely.
*
* T requirements:
* - default constructible, copyable, destructible, assignable
* HashPolicy requirements:
* - see "Hash policy" above (default js::DefaultHasher<Key>)
* AllocPolicy:
* - see "Allocation policies" in jstl.h (default js::ContextAllocPolicy)
*
* N.B: HashSet is not reentrant: T/HashPolicy/AllocPolicy members called by
* HashSet must not call back into the same HashSet object.
* N.B: Due to the lack of exception handling, the user must call |init()|.
*/
template <class T, class HashPolicy, class AllocPolicy>
class HashSet
{
typedef typename HashPolicy::Lookup Lookup;
/* Implement HashSet in terms of HashTable. */
struct SetOps : HashPolicy {
typedef T KeyType;
static const KeyType &getKey(const T &t) { return t; }
};
typedef detail::HashTable<const T, SetOps, AllocPolicy> Impl;
friend class Impl::Enum;
/* Not implicitly copyable (expensive). May add explicit |clone| later. */
HashSet(const HashSet &);
HashSet &operator=(const HashSet &);
Impl impl;
public:
/*
* HashSet construction is fallible (due to OOM); thus the user must call
* init after constructing a HashSet and check the return value.
*/
HashSet(AllocPolicy a = AllocPolicy()) : impl(a) {}
bool init(uint32 cap = 0) { return impl.init(cap); }
/*
* Return whether the given lookup value is present in the map. E.g.:
*
* typedef HashSet<int> HS;
* HS h;
* if (HS::Ptr p = h.lookup(3)) {
* assert(*p == 3); // p acts like a pointer to int
* }
*
* Also see the definition of Ptr in HashTable above.
*/
typedef typename Impl::Ptr Ptr;
Ptr lookup(const Lookup &l) const { return impl.lookup(l); }
/* Assuming |p.found()|, remove |*p|. */
void remove(Ptr p) { impl.remove(p); }
/*
* Like |lookup(l)|, but on miss, |p = lookupForAdd(l)| allows efficient
* insertion of T value |t| (where |HashPolicy::match(t,l) == true|) using
* |add(p,t)|. After |add(p,t)|, |p| points to the new element. E.g.:
*
* typedef HashSet<int> HS;
* HS h;
* HS::AddPtr p = h.lookupForAdd(3);
* if (!p) {
* if (!h.add(p, 3))
* return false;
* }
* assert(*p == 3); // p acts like a pointer to int
*
* Also see the definition of AddPtr in HashTable above.
*/
typedef typename Impl::AddPtr AddPtr;
AddPtr lookupForAdd(const Lookup &l) const { return impl.lookupForAdd(l); }
bool add(AddPtr &p, const T &t) { return impl.add(p,t); }
/*
* |all()| returns a Range containing |count()| elements:
*
* typedef HashSet<int> HS;
* HS h;
* for (HS::Range r = h.all(); !r.empty(); r.popFront())
* int i = r.front();
*
* Also see the definition of Range in HashTable above.
*/
typedef typename Impl::Range Range;
Range all() const { return impl.all(); }
size_t count() const { return impl.count(); }
/*
* Typedef for the enumeration class. An Enum may be used to examine and
* remove table entries:
*
* typedef HashSet<int> HS;
* HS s;
* for (HS::Enum e(s); !e.empty(); e.popFront())
* if (e.front() == 42)
* e.removeFront();
*
* Table resize may occur in Enum's destructor. Also see the definition of
* Enum in HashTable above.
*/
typedef typename Impl::Enum Enum;
/* Remove all entries. */
void clear() { impl.clear(); }
/* Does the table contain any entries? */
bool empty() const { return impl.empty(); }
/*
* If |generation()| is the same before and after a HashSet operation,
* pointers into the table remain valid.
*/
unsigned generation() const { return impl.generation(); }
/* Shorthand operations: */
bool has(const Lookup &l) const {
return impl.lookup(l) != NULL;
}
const T *put(const T &t) {
AddPtr p = lookupForAdd(t);
return p ? &*p : (add(p, t) ? &*p : NULL);
}
void remove(const Lookup &l) {
if (Ptr p = lookup(l))
remove(p);
}
};
} /* namespace js */
#endif
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