mirror of
https://github.com/mozilla/gecko-dev.git
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2255 lines
71 KiB
C++
2255 lines
71 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//---------------------------------------------------------------------------
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// Overview
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//---------------------------------------------------------------------------
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//
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// This file defines HashMap<Key, Value> and HashSet<T>, hash tables that are
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// fast and have a nice API.
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//
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// Both hash tables have two optional template parameters.
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//
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// - HashPolicy. This defines the operations for hashing and matching keys. The
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// default HashPolicy is appropriate when both of the following two
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// conditions are true.
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//
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// - The key type stored in the table (|Key| for |HashMap<Key, Value>|, |T|
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// for |HashSet<T>|) is an integer, pointer, UniquePtr, float, or double.
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//
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// - The type used for lookups (|Lookup|) is the same as the key type. This
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// is usually the case, but not always.
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//
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// There is also a |CStringHasher| policy for |char*| keys. If your keys
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// don't match any of the above cases, you must provide your own hash policy;
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// see the "Hash Policy" section below.
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//
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// - AllocPolicy. This defines how allocations are done by the table.
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//
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// - |MallocAllocPolicy| is the default and is usually appropriate; note that
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// operations (such as insertions) that might cause allocations are
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// fallible and must be checked for OOM. These checks are enforced by the
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// use of [[nodiscard]].
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//
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// - |InfallibleAllocPolicy| is another possibility; it allows the
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// abovementioned OOM checks to be done with MOZ_ALWAYS_TRUE().
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//
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// Note that entry storage allocation is lazy, and not done until the first
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// lookupForAdd(), put(), or putNew() is performed.
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//
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// See AllocPolicy.h for more details.
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//
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// Documentation on how to use HashMap and HashSet, including examples, is
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// present within those classes. Search for "class HashMap" and "class
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// HashSet".
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//
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// Both HashMap and HashSet are implemented on top of a third class, HashTable.
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// You only need to look at HashTable if you want to understand the
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// implementation.
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//
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// How does mozilla::HashTable (this file) compare with PLDHashTable (and its
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// subclasses, such as nsTHashtable)?
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//
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// - mozilla::HashTable is a lot faster, largely because it uses templates
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// throughout *and* inlines everything. PLDHashTable inlines operations much
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// less aggressively, and also uses "virtual ops" for operations like hashing
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// and matching entries that require function calls.
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//
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// - Correspondingly, mozilla::HashTable use is likely to increase executable
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// size much more than PLDHashTable.
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//
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// - mozilla::HashTable has a nicer API, with a proper HashSet vs. HashMap
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// distinction.
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//
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// - mozilla::HashTable requires more explicit OOM checking. As mentioned
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// above, the use of |InfallibleAllocPolicy| can simplify things.
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//
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// - mozilla::HashTable has a default capacity on creation of 32 and a minimum
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// capacity of 4. PLDHashTable has a default capacity on creation of 8 and a
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// minimum capacity of 8.
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#ifndef mozilla_HashTable_h
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#define mozilla_HashTable_h
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#include <utility>
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#include <type_traits>
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#include "mozilla/AllocPolicy.h"
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#include "mozilla/Assertions.h"
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#include "mozilla/Attributes.h"
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#include "mozilla/Casting.h"
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#include "mozilla/HashFunctions.h"
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#include "mozilla/MathAlgorithms.h"
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#include "mozilla/Maybe.h"
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#include "mozilla/MemoryChecking.h"
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#include "mozilla/MemoryReporting.h"
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#include "mozilla/Opaque.h"
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#include "mozilla/OperatorNewExtensions.h"
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#include "mozilla/ReentrancyGuard.h"
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#include "mozilla/UniquePtr.h"
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#include "mozilla/WrappingOperations.h"
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namespace mozilla {
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template <class, class = void>
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struct DefaultHasher;
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template <class, class>
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class HashMapEntry;
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namespace detail {
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template <typename T>
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class HashTableEntry;
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template <class T, class HashPolicy, class AllocPolicy>
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class HashTable;
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} // namespace detail
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// The "generation" of a hash table is an opaque value indicating the state of
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// modification of the hash table through its lifetime. If the generation of
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// a hash table compares equal at times T1 and T2, then lookups in the hash
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// table, pointers to (or into) hash table entries, etc. at time T1 are valid
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// at time T2. If the generation compares unequal, these computations are all
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// invalid and must be performed again to be used.
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//
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// Generations are meaningfully comparable only with respect to a single hash
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// table. It's always nonsensical to compare the generation of distinct hash
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// tables H1 and H2.
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using Generation = Opaque<uint64_t>;
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//---------------------------------------------------------------------------
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// HashMap
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//---------------------------------------------------------------------------
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// HashMap is a fast hash-based map from keys to values.
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//
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// Template parameter requirements:
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// - Key/Value: movable, destructible, assignable.
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// - HashPolicy: see the "Hash Policy" section below.
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// - AllocPolicy: see AllocPolicy.h.
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//
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// Note:
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// - HashMap is not reentrant: Key/Value/HashPolicy/AllocPolicy members
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// called by HashMap must not call back into the same HashMap object.
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//
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template <class Key, class Value, class HashPolicy = DefaultHasher<Key>,
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class AllocPolicy = MallocAllocPolicy>
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class HashMap {
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// -- Implementation details -----------------------------------------------
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// HashMap is not copyable or assignable.
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HashMap(const HashMap& hm) = delete;
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HashMap& operator=(const HashMap& hm) = delete;
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using TableEntry = HashMapEntry<Key, Value>;
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struct MapHashPolicy : HashPolicy {
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using Base = HashPolicy;
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using KeyType = Key;
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static const Key& getKey(TableEntry& aEntry) { return aEntry.key(); }
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static void setKey(TableEntry& aEntry, Key& aKey) {
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HashPolicy::rekey(aEntry.mutableKey(), aKey);
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}
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};
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using Impl = detail::HashTable<TableEntry, MapHashPolicy, AllocPolicy>;
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Impl mImpl;
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friend class Impl::Enum;
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public:
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using Lookup = typename HashPolicy::Lookup;
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using Entry = TableEntry;
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// -- Initialization -------------------------------------------------------
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explicit HashMap(AllocPolicy aAllocPolicy = AllocPolicy(),
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uint32_t aLen = Impl::sDefaultLen)
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: mImpl(std::move(aAllocPolicy), aLen) {}
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explicit HashMap(uint32_t aLen) : mImpl(AllocPolicy(), aLen) {}
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// HashMap is movable.
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HashMap(HashMap&& aRhs) = default;
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HashMap& operator=(HashMap&& aRhs) = default;
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// -- Status and sizing ----------------------------------------------------
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// The map's current generation.
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Generation generation() const { return mImpl.generation(); }
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// Is the map empty?
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bool empty() const { return mImpl.empty(); }
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// Number of keys/values in the map.
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uint32_t count() const { return mImpl.count(); }
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// Number of key/value slots in the map. Note: resize will happen well before
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// count() == capacity().
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uint32_t capacity() const { return mImpl.capacity(); }
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// The size of the map's entry storage, in bytes. If the keys/values contain
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// pointers to other heap blocks, you must iterate over the map and measure
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// them separately; hence the "shallow" prefix.
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size_t shallowSizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
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return mImpl.shallowSizeOfExcludingThis(aMallocSizeOf);
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}
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size_t shallowSizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
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return aMallocSizeOf(this) +
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mImpl.shallowSizeOfExcludingThis(aMallocSizeOf);
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}
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// Attempt to minimize the capacity(). If the table is empty, this will free
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// the empty storage and upon regrowth it will be given the minimum capacity.
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void compact() { mImpl.compact(); }
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// Attempt to reserve enough space to fit at least |aLen| elements. This is
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// total capacity, including elements already present. Does nothing if the
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// map already has sufficient capacity.
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[[nodiscard]] bool reserve(uint32_t aLen) { return mImpl.reserve(aLen); }
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// -- Lookups --------------------------------------------------------------
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// Does the map contain a key/value matching |aLookup|?
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bool has(const Lookup& aLookup) const {
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return mImpl.lookup(aLookup).found();
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}
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// Return a Ptr indicating whether a key/value matching |aLookup| is
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// present in the map. E.g.:
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//
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// using HM = HashMap<int,char>;
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// HM h;
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// if (HM::Ptr p = h.lookup(3)) {
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// assert(p->key() == 3);
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// char val = p->value();
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// }
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//
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using Ptr = typename Impl::Ptr;
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MOZ_ALWAYS_INLINE Ptr lookup(const Lookup& aLookup) const {
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return mImpl.lookup(aLookup);
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}
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// Like lookup(), but does not assert if two threads call it at the same
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// time. Only use this method when none of the threads will modify the map.
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MOZ_ALWAYS_INLINE Ptr readonlyThreadsafeLookup(const Lookup& aLookup) const {
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return mImpl.readonlyThreadsafeLookup(aLookup);
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}
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// -- Insertions -----------------------------------------------------------
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// Overwrite existing value with |aValue|, or add it if not present. Returns
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// false on OOM.
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template <typename KeyInput, typename ValueInput>
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[[nodiscard]] bool put(KeyInput&& aKey, ValueInput&& aValue) {
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return put(aKey, std::forward<KeyInput>(aKey),
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std::forward<ValueInput>(aValue));
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}
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template <typename KeyInput, typename ValueInput>
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[[nodiscard]] bool put(const Lookup& aLookup, KeyInput&& aKey,
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ValueInput&& aValue) {
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AddPtr p = lookupForAdd(aLookup);
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if (p) {
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p->value() = std::forward<ValueInput>(aValue);
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return true;
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}
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return add(p, std::forward<KeyInput>(aKey),
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std::forward<ValueInput>(aValue));
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}
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// Like put(), but slightly faster. Must only be used when the given key is
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// not already present. (In debug builds, assertions check this.)
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template <typename KeyInput, typename ValueInput>
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[[nodiscard]] bool putNew(KeyInput&& aKey, ValueInput&& aValue) {
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return mImpl.putNew(aKey, std::forward<KeyInput>(aKey),
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std::forward<ValueInput>(aValue));
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}
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template <typename KeyInput, typename ValueInput>
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[[nodiscard]] bool putNew(const Lookup& aLookup, KeyInput&& aKey,
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ValueInput&& aValue) {
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return mImpl.putNew(aLookup, std::forward<KeyInput>(aKey),
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std::forward<ValueInput>(aValue));
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}
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// Like putNew(), but should be only used when the table is known to be big
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// enough for the insertion, and hashing cannot fail. Typically this is used
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// to populate an empty map with known-unique keys after reserving space with
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// reserve(), e.g.
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//
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// using HM = HashMap<int,char>;
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// HM h;
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// if (!h.reserve(3)) {
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// MOZ_CRASH("OOM");
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// }
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// h.putNewInfallible(1, 'a'); // unique key
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// h.putNewInfallible(2, 'b'); // unique key
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// h.putNewInfallible(3, 'c'); // unique key
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//
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template <typename KeyInput, typename ValueInput>
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void putNewInfallible(KeyInput&& aKey, ValueInput&& aValue) {
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mImpl.putNewInfallible(aKey, std::forward<KeyInput>(aKey),
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std::forward<ValueInput>(aValue));
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}
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// Like |lookup(l)|, but on miss, |p = lookupForAdd(l)| allows efficient
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// insertion of Key |k| (where |HashPolicy::match(k,l) == true|) using
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// |add(p,k,v)|. After |add(p,k,v)|, |p| points to the new key/value. E.g.:
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//
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// using HM = HashMap<int,char>;
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// HM h;
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// HM::AddPtr p = h.lookupForAdd(3);
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// if (!p) {
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// if (!h.add(p, 3, 'a')) {
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// return false;
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// }
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// }
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// assert(p->key() == 3);
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// char val = p->value();
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//
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// N.B. The caller must ensure that no mutating hash table operations occur
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// between a pair of lookupForAdd() and add() calls. To avoid looking up the
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// key a second time, the caller may use the more efficient relookupOrAdd()
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// method. This method reuses part of the hashing computation to more
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// efficiently insert the key if it has not been added. For example, a
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// mutation-handling version of the previous example:
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//
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// HM::AddPtr p = h.lookupForAdd(3);
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// if (!p) {
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// call_that_may_mutate_h();
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// if (!h.relookupOrAdd(p, 3, 'a')) {
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// return false;
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// }
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// }
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// assert(p->key() == 3);
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// char val = p->value();
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//
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using AddPtr = typename Impl::AddPtr;
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MOZ_ALWAYS_INLINE AddPtr lookupForAdd(const Lookup& aLookup) {
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return mImpl.lookupForAdd(aLookup);
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}
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// Add a key/value. Returns false on OOM.
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template <typename KeyInput, typename ValueInput>
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[[nodiscard]] bool add(AddPtr& aPtr, KeyInput&& aKey, ValueInput&& aValue) {
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return mImpl.add(aPtr, std::forward<KeyInput>(aKey),
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std::forward<ValueInput>(aValue));
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}
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// See the comment above lookupForAdd() for details.
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template <typename KeyInput, typename ValueInput>
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[[nodiscard]] bool relookupOrAdd(AddPtr& aPtr, KeyInput&& aKey,
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ValueInput&& aValue) {
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return mImpl.relookupOrAdd(aPtr, aKey, std::forward<KeyInput>(aKey),
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std::forward<ValueInput>(aValue));
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}
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// -- Removal --------------------------------------------------------------
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// Lookup and remove the key/value matching |aLookup|, if present.
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void remove(const Lookup& aLookup) {
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if (Ptr p = lookup(aLookup)) {
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remove(p);
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}
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}
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// Remove a previously found key/value (assuming aPtr.found()). The map must
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// not have been mutated in the interim.
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void remove(Ptr aPtr) { mImpl.remove(aPtr); }
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// Remove all keys/values without changing the capacity.
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void clear() { mImpl.clear(); }
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// Like clear() followed by compact().
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void clearAndCompact() { mImpl.clearAndCompact(); }
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// -- Rekeying -------------------------------------------------------------
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// Infallibly rekey one entry, if necessary. Requires that template
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// parameters Key and HashPolicy::Lookup are the same type.
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void rekeyIfMoved(const Key& aOldKey, const Key& aNewKey) {
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if (aOldKey != aNewKey) {
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rekeyAs(aOldKey, aNewKey, aNewKey);
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}
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}
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// Infallibly rekey one entry if present, and return whether that happened.
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bool rekeyAs(const Lookup& aOldLookup, const Lookup& aNewLookup,
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const Key& aNewKey) {
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if (Ptr p = lookup(aOldLookup)) {
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mImpl.rekeyAndMaybeRehash(p, aNewLookup, aNewKey);
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return true;
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}
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return false;
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}
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// -- Iteration ------------------------------------------------------------
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// |iter()| returns an Iterator:
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//
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// HashMap<int, char> h;
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// for (auto iter = h.iter(); !iter.done(); iter.next()) {
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// char c = iter.get().value();
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// }
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//
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using Iterator = typename Impl::Iterator;
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Iterator iter() const { return mImpl.iter(); }
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// |modIter()| returns a ModIterator:
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//
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// HashMap<int, char> h;
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// for (auto iter = h.modIter(); !iter.done(); iter.next()) {
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// if (iter.get().value() == 'l') {
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// iter.remove();
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// }
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// }
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//
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// Table resize may occur in ModIterator's destructor.
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using ModIterator = typename Impl::ModIterator;
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ModIterator modIter() { return mImpl.modIter(); }
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// These are similar to Iterator/ModIterator/iter(), but use different
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// terminology.
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using Range = typename Impl::Range;
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using Enum = typename Impl::Enum;
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Range all() const { return mImpl.all(); }
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};
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//---------------------------------------------------------------------------
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// HashSet
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//---------------------------------------------------------------------------
|
|
|
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// HashSet is a fast hash-based set of values.
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//
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// Template parameter requirements:
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// - T: movable, destructible, assignable.
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// - HashPolicy: see the "Hash Policy" section below.
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// - AllocPolicy: see AllocPolicy.h
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//
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// Note:
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// - HashSet is not reentrant: T/HashPolicy/AllocPolicy members called by
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// HashSet must not call back into the same HashSet object.
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//
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template <class T, class HashPolicy = DefaultHasher<T>,
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class AllocPolicy = MallocAllocPolicy>
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class HashSet {
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// -- Implementation details -----------------------------------------------
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|
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// HashSet is not copyable or assignable.
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HashSet(const HashSet& hs) = delete;
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HashSet& operator=(const HashSet& hs) = delete;
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struct SetHashPolicy : HashPolicy {
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using Base = HashPolicy;
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using KeyType = T;
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static const KeyType& getKey(const T& aT) { return aT; }
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static void setKey(T& aT, KeyType& aKey) { HashPolicy::rekey(aT, aKey); }
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};
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using Impl = detail::HashTable<const T, SetHashPolicy, AllocPolicy>;
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Impl mImpl;
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|
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friend class Impl::Enum;
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|
|
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public:
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using Lookup = typename HashPolicy::Lookup;
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using Entry = T;
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|
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// -- Initialization -------------------------------------------------------
|
|
|
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explicit HashSet(AllocPolicy aAllocPolicy = AllocPolicy(),
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uint32_t aLen = Impl::sDefaultLen)
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: mImpl(std::move(aAllocPolicy), aLen) {}
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|
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explicit HashSet(uint32_t aLen) : mImpl(AllocPolicy(), aLen) {}
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|
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// HashSet is movable.
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HashSet(HashSet&& aRhs) = default;
|
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HashSet& operator=(HashSet&& aRhs) = default;
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|
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// -- Status and sizing ----------------------------------------------------
|
|
|
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// The set's current generation.
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Generation generation() const { return mImpl.generation(); }
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|
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// Is the set empty?
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bool empty() const { return mImpl.empty(); }
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|
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// Number of elements in the set.
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uint32_t count() const { return mImpl.count(); }
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|
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// Number of element slots in the set. Note: resize will happen well before
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// count() == capacity().
|
|
uint32_t capacity() const { return mImpl.capacity(); }
|
|
|
|
// The size of the set's entry storage, in bytes. If the elements contain
|
|
// pointers to other heap blocks, you must iterate over the set and measure
|
|
// them separately; hence the "shallow" prefix.
|
|
size_t shallowSizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
|
|
return mImpl.shallowSizeOfExcludingThis(aMallocSizeOf);
|
|
}
|
|
size_t shallowSizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
|
|
return aMallocSizeOf(this) +
|
|
mImpl.shallowSizeOfExcludingThis(aMallocSizeOf);
|
|
}
|
|
|
|
// Attempt to minimize the capacity(). If the table is empty, this will free
|
|
// the empty storage and upon regrowth it will be given the minimum capacity.
|
|
void compact() { mImpl.compact(); }
|
|
|
|
// Attempt to reserve enough space to fit at least |aLen| elements. This is
|
|
// total capacity, including elements already present. Does nothing if the
|
|
// map already has sufficient capacity.
|
|
[[nodiscard]] bool reserve(uint32_t aLen) { return mImpl.reserve(aLen); }
|
|
|
|
// -- Lookups --------------------------------------------------------------
|
|
|
|
// Does the set contain an element matching |aLookup|?
|
|
bool has(const Lookup& aLookup) const {
|
|
return mImpl.lookup(aLookup).found();
|
|
}
|
|
|
|
// Return a Ptr indicating whether an element matching |aLookup| is present
|
|
// in the set. E.g.:
|
|
//
|
|
// using HS = HashSet<int>;
|
|
// HS h;
|
|
// if (HS::Ptr p = h.lookup(3)) {
|
|
// assert(*p == 3); // p acts like a pointer to int
|
|
// }
|
|
//
|
|
using Ptr = typename Impl::Ptr;
|
|
MOZ_ALWAYS_INLINE Ptr lookup(const Lookup& aLookup) const {
|
|
return mImpl.lookup(aLookup);
|
|
}
|
|
|
|
// Like lookup(), but does not assert if two threads call it at the same
|
|
// time. Only use this method when none of the threads will modify the set.
|
|
MOZ_ALWAYS_INLINE Ptr readonlyThreadsafeLookup(const Lookup& aLookup) const {
|
|
return mImpl.readonlyThreadsafeLookup(aLookup);
|
|
}
|
|
|
|
// -- Insertions -----------------------------------------------------------
|
|
|
|
// Add |aU| if it is not present already. Returns false on OOM.
|
|
template <typename U>
|
|
[[nodiscard]] bool put(U&& aU) {
|
|
AddPtr p = lookupForAdd(aU);
|
|
return p ? true : add(p, std::forward<U>(aU));
|
|
}
|
|
|
|
// Like put(), but slightly faster. Must only be used when the given element
|
|
// is not already present. (In debug builds, assertions check this.)
|
|
template <typename U>
|
|
[[nodiscard]] bool putNew(U&& aU) {
|
|
return mImpl.putNew(aU, std::forward<U>(aU));
|
|
}
|
|
|
|
// Like the other putNew(), but for when |Lookup| is different to |T|.
|
|
template <typename U>
|
|
[[nodiscard]] bool putNew(const Lookup& aLookup, U&& aU) {
|
|
return mImpl.putNew(aLookup, std::forward<U>(aU));
|
|
}
|
|
|
|
// Like putNew(), but should be only used when the table is known to be big
|
|
// enough for the insertion, and hashing cannot fail. Typically this is used
|
|
// to populate an empty set with known-unique elements after reserving space
|
|
// with reserve(), e.g.
|
|
//
|
|
// using HS = HashMap<int>;
|
|
// HS h;
|
|
// if (!h.reserve(3)) {
|
|
// MOZ_CRASH("OOM");
|
|
// }
|
|
// h.putNewInfallible(1); // unique element
|
|
// h.putNewInfallible(2); // unique element
|
|
// h.putNewInfallible(3); // unique element
|
|
//
|
|
template <typename U>
|
|
void putNewInfallible(const Lookup& aLookup, U&& aU) {
|
|
mImpl.putNewInfallible(aLookup, std::forward<U>(aU));
|
|
}
|
|
|
|
// 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.:
|
|
//
|
|
// using HS = HashSet<int>;
|
|
// 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
|
|
//
|
|
// N.B. The caller must ensure that no mutating hash table operations occur
|
|
// between a pair of lookupForAdd() and add() calls. To avoid looking up the
|
|
// key a second time, the caller may use the more efficient relookupOrAdd()
|
|
// method. This method reuses part of the hashing computation to more
|
|
// efficiently insert the key if it has not been added. For example, a
|
|
// mutation-handling version of the previous example:
|
|
//
|
|
// HS::AddPtr p = h.lookupForAdd(3);
|
|
// if (!p) {
|
|
// call_that_may_mutate_h();
|
|
// if (!h.relookupOrAdd(p, 3, 3)) {
|
|
// return false;
|
|
// }
|
|
// }
|
|
// assert(*p == 3);
|
|
//
|
|
// Note that relookupOrAdd(p,l,t) performs Lookup using |l| and adds the
|
|
// entry |t|, where the caller ensures match(l,t).
|
|
using AddPtr = typename Impl::AddPtr;
|
|
MOZ_ALWAYS_INLINE AddPtr lookupForAdd(const Lookup& aLookup) {
|
|
return mImpl.lookupForAdd(aLookup);
|
|
}
|
|
|
|
// Add an element. Returns false on OOM.
|
|
template <typename U>
|
|
[[nodiscard]] bool add(AddPtr& aPtr, U&& aU) {
|
|
return mImpl.add(aPtr, std::forward<U>(aU));
|
|
}
|
|
|
|
// See the comment above lookupForAdd() for details.
|
|
template <typename U>
|
|
[[nodiscard]] bool relookupOrAdd(AddPtr& aPtr, const Lookup& aLookup,
|
|
U&& aU) {
|
|
return mImpl.relookupOrAdd(aPtr, aLookup, std::forward<U>(aU));
|
|
}
|
|
|
|
// -- Removal --------------------------------------------------------------
|
|
|
|
// Lookup and remove the element matching |aLookup|, if present.
|
|
void remove(const Lookup& aLookup) {
|
|
if (Ptr p = lookup(aLookup)) {
|
|
remove(p);
|
|
}
|
|
}
|
|
|
|
// Remove a previously found element (assuming aPtr.found()). The set must
|
|
// not have been mutated in the interim.
|
|
void remove(Ptr aPtr) { mImpl.remove(aPtr); }
|
|
|
|
// Remove all keys/values without changing the capacity.
|
|
void clear() { mImpl.clear(); }
|
|
|
|
// Like clear() followed by compact().
|
|
void clearAndCompact() { mImpl.clearAndCompact(); }
|
|
|
|
// -- Rekeying -------------------------------------------------------------
|
|
|
|
// Infallibly rekey one entry, if present. Requires that template parameters
|
|
// T and HashPolicy::Lookup are the same type.
|
|
void rekeyIfMoved(const Lookup& aOldValue, const T& aNewValue) {
|
|
if (aOldValue != aNewValue) {
|
|
rekeyAs(aOldValue, aNewValue, aNewValue);
|
|
}
|
|
}
|
|
|
|
// Infallibly rekey one entry if present, and return whether that happened.
|
|
bool rekeyAs(const Lookup& aOldLookup, const Lookup& aNewLookup,
|
|
const T& aNewValue) {
|
|
if (Ptr p = lookup(aOldLookup)) {
|
|
mImpl.rekeyAndMaybeRehash(p, aNewLookup, aNewValue);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Infallibly replace the current key at |aPtr| with an equivalent key.
|
|
// Specifically, both HashPolicy::hash and HashPolicy::match must return
|
|
// identical results for the new and old key when applied against all
|
|
// possible matching values.
|
|
void replaceKey(Ptr aPtr, const Lookup& aLookup, const T& aNewValue) {
|
|
MOZ_ASSERT(aPtr.found());
|
|
MOZ_ASSERT(*aPtr != aNewValue);
|
|
MOZ_ASSERT(HashPolicy::match(*aPtr, aLookup));
|
|
MOZ_ASSERT(HashPolicy::match(aNewValue, aLookup));
|
|
const_cast<T&>(*aPtr) = aNewValue;
|
|
MOZ_ASSERT(*lookup(aLookup) == aNewValue);
|
|
}
|
|
void replaceKey(Ptr aPtr, const T& aNewValue) {
|
|
replaceKey(aPtr, aNewValue, aNewValue);
|
|
}
|
|
|
|
// -- Iteration ------------------------------------------------------------
|
|
|
|
// |iter()| returns an Iterator:
|
|
//
|
|
// HashSet<int> h;
|
|
// for (auto iter = h.iter(); !iter.done(); iter.next()) {
|
|
// int i = iter.get();
|
|
// }
|
|
//
|
|
using Iterator = typename Impl::Iterator;
|
|
Iterator iter() const { return mImpl.iter(); }
|
|
|
|
// |modIter()| returns a ModIterator:
|
|
//
|
|
// HashSet<int> h;
|
|
// for (auto iter = h.modIter(); !iter.done(); iter.next()) {
|
|
// if (iter.get() == 42) {
|
|
// iter.remove();
|
|
// }
|
|
// }
|
|
//
|
|
// Table resize may occur in ModIterator's destructor.
|
|
using ModIterator = typename Impl::ModIterator;
|
|
ModIterator modIter() { return mImpl.modIter(); }
|
|
|
|
// These are similar to Iterator/ModIterator/iter(), but use different
|
|
// terminology.
|
|
using Range = typename Impl::Range;
|
|
using Enum = typename Impl::Enum;
|
|
Range all() const { return mImpl.all(); }
|
|
};
|
|
|
|
//---------------------------------------------------------------------------
|
|
// Hash Policy
|
|
//---------------------------------------------------------------------------
|
|
|
|
// A hash policy |HP| for a hash table with key-type |Key| must provide:
|
|
//
|
|
// - a type |HP::Lookup| to use to lookup table entries;
|
|
//
|
|
// - a static member function |HP::hash| that hashes lookup values:
|
|
//
|
|
// static mozilla::HashNumber hash(const Lookup&);
|
|
//
|
|
// - a static member function |HP::match| that tests equality of key and
|
|
// lookup values:
|
|
//
|
|
// static bool match(const Key&, const Lookup&);
|
|
//
|
|
// 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 not equal
|
|
// to the added Key value |k|, the user must ensure that |HP::match(k,l)| is
|
|
// true. E.g.:
|
|
//
|
|
// mozilla::HashSet<Key, HP>::AddPtr p = h.lookup(l);
|
|
// if (!p) {
|
|
// assert(HP::match(k, l)); // must hold
|
|
// h.add(p, k);
|
|
// }
|
|
|
|
// A pointer hashing policy that uses HashGeneric() to create good hashes for
|
|
// pointers. Note that we don't shift out the lowest k bits because we don't
|
|
// want to assume anything about the alignment of the pointers.
|
|
template <typename Key>
|
|
struct PointerHasher {
|
|
using Lookup = Key;
|
|
|
|
static HashNumber hash(const Lookup& aLookup) {
|
|
size_t word = reinterpret_cast<size_t>(aLookup);
|
|
return HashGeneric(word);
|
|
}
|
|
|
|
static bool match(const Key& aKey, const Lookup& aLookup) {
|
|
return aKey == aLookup;
|
|
}
|
|
|
|
static void rekey(Key& aKey, const Key& aNewKey) { aKey = aNewKey; }
|
|
};
|
|
|
|
// The default hash policy, which only works with integers.
|
|
template <class Key, typename>
|
|
struct DefaultHasher {
|
|
using Lookup = Key;
|
|
|
|
static HashNumber hash(const Lookup& aLookup) {
|
|
// Just convert the integer to a HashNumber and use that as is. (This
|
|
// discards the high 32-bits of 64-bit integers!) ScrambleHashCode() is
|
|
// subsequently called on the value to improve the distribution.
|
|
return aLookup;
|
|
}
|
|
|
|
static bool match(const Key& aKey, const Lookup& aLookup) {
|
|
// Use builtin or overloaded operator==.
|
|
return aKey == aLookup;
|
|
}
|
|
|
|
static void rekey(Key& aKey, const Key& aNewKey) { aKey = aNewKey; }
|
|
};
|
|
|
|
// A DefaultHasher specialization for enums.
|
|
template <class T>
|
|
struct DefaultHasher<T, std::enable_if_t<std::is_enum_v<T>>> {
|
|
using Key = T;
|
|
using Lookup = Key;
|
|
|
|
static HashNumber hash(const Lookup& aLookup) { return HashGeneric(aLookup); }
|
|
|
|
static bool match(const Key& aKey, const Lookup& aLookup) {
|
|
// Use builtin or overloaded operator==.
|
|
return aKey == static_cast<Key>(aLookup);
|
|
}
|
|
|
|
static void rekey(Key& aKey, const Key& aNewKey) { aKey = aNewKey; }
|
|
};
|
|
|
|
// A DefaultHasher specialization for pointers.
|
|
template <class T>
|
|
struct DefaultHasher<T*> : PointerHasher<T*> {};
|
|
|
|
// A DefaultHasher specialization for mozilla::UniquePtr.
|
|
template <class T, class D>
|
|
struct DefaultHasher<UniquePtr<T, D>> {
|
|
using Key = UniquePtr<T, D>;
|
|
using Lookup = Key;
|
|
using PtrHasher = PointerHasher<T*>;
|
|
|
|
static HashNumber hash(const Lookup& aLookup) {
|
|
return PtrHasher::hash(aLookup.get());
|
|
}
|
|
|
|
static bool match(const Key& aKey, const Lookup& aLookup) {
|
|
return PtrHasher::match(aKey.get(), aLookup.get());
|
|
}
|
|
|
|
static void rekey(UniquePtr<T, D>& aKey, UniquePtr<T, D>&& aNewKey) {
|
|
aKey = std::move(aNewKey);
|
|
}
|
|
};
|
|
|
|
// A DefaultHasher specialization for doubles.
|
|
template <>
|
|
struct DefaultHasher<double> {
|
|
using Key = double;
|
|
using Lookup = Key;
|
|
|
|
static HashNumber hash(const Lookup& aLookup) {
|
|
// Just xor the high bits with the low bits, and then treat the bits of the
|
|
// result as a uint32_t.
|
|
static_assert(sizeof(HashNumber) == 4,
|
|
"subsequent code assumes a four-byte hash");
|
|
uint64_t u = BitwiseCast<uint64_t>(aLookup);
|
|
return HashNumber(u ^ (u >> 32));
|
|
}
|
|
|
|
static bool match(const Key& aKey, const Lookup& aLookup) {
|
|
return BitwiseCast<uint64_t>(aKey) == BitwiseCast<uint64_t>(aLookup);
|
|
}
|
|
};
|
|
|
|
// A DefaultHasher specialization for floats.
|
|
template <>
|
|
struct DefaultHasher<float> {
|
|
using Key = float;
|
|
using Lookup = Key;
|
|
|
|
static HashNumber hash(const Lookup& aLookup) {
|
|
// Just use the value as if its bits form an integer. ScrambleHashCode() is
|
|
// subsequently called on the value to improve the distribution.
|
|
static_assert(sizeof(HashNumber) == 4,
|
|
"subsequent code assumes a four-byte hash");
|
|
return HashNumber(BitwiseCast<uint32_t>(aLookup));
|
|
}
|
|
|
|
static bool match(const Key& aKey, const Lookup& aLookup) {
|
|
return BitwiseCast<uint32_t>(aKey) == BitwiseCast<uint32_t>(aLookup);
|
|
}
|
|
};
|
|
|
|
// A hash policy for C strings.
|
|
struct CStringHasher {
|
|
using Key = const char*;
|
|
using Lookup = const char*;
|
|
|
|
static HashNumber hash(const Lookup& aLookup) { return HashString(aLookup); }
|
|
|
|
static bool match(const Key& aKey, const Lookup& aLookup) {
|
|
return strcmp(aKey, aLookup) == 0;
|
|
}
|
|
};
|
|
|
|
//---------------------------------------------------------------------------
|
|
// Fallible Hashing Interface
|
|
//---------------------------------------------------------------------------
|
|
|
|
// Most of the time generating a hash code is infallible so this class provides
|
|
// default methods that always succeed. Specialize this class for your own hash
|
|
// policy to provide fallible hashing.
|
|
//
|
|
// This is used by MovableCellHasher to handle the fact that generating a unique
|
|
// ID for cell pointer may fail due to OOM.
|
|
template <typename HashPolicy>
|
|
struct FallibleHashMethods {
|
|
// Return true if a hashcode is already available for its argument. Once
|
|
// this returns true for a specific argument it must continue to do so.
|
|
template <typename Lookup>
|
|
static bool hasHash(Lookup&& aLookup) {
|
|
return true;
|
|
}
|
|
|
|
// Fallible method to ensure a hashcode exists for its argument and create
|
|
// one if not. Returns false on error, e.g. out of memory.
|
|
template <typename Lookup>
|
|
static bool ensureHash(Lookup&& aLookup) {
|
|
return true;
|
|
}
|
|
};
|
|
|
|
template <typename HashPolicy, typename Lookup>
|
|
static bool HasHash(Lookup&& aLookup) {
|
|
return FallibleHashMethods<typename HashPolicy::Base>::hasHash(
|
|
std::forward<Lookup>(aLookup));
|
|
}
|
|
|
|
template <typename HashPolicy, typename Lookup>
|
|
static bool EnsureHash(Lookup&& aLookup) {
|
|
return FallibleHashMethods<typename HashPolicy::Base>::ensureHash(
|
|
std::forward<Lookup>(aLookup));
|
|
}
|
|
|
|
//---------------------------------------------------------------------------
|
|
// Implementation Details (HashMapEntry, HashTableEntry, HashTable)
|
|
//---------------------------------------------------------------------------
|
|
|
|
// Both HashMap and HashSet are implemented by a single HashTable that is even
|
|
// more heavily parameterized than the other two. This leaves HashTable gnarly
|
|
// and extremely coupled to HashMap and HashSet; thus code should not use
|
|
// HashTable directly.
|
|
|
|
template <class Key, class Value>
|
|
class HashMapEntry {
|
|
Key key_;
|
|
Value value_;
|
|
|
|
template <class, class, class>
|
|
friend class detail::HashTable;
|
|
template <class>
|
|
friend class detail::HashTableEntry;
|
|
template <class, class, class, class>
|
|
friend class HashMap;
|
|
|
|
public:
|
|
template <typename KeyInput, typename ValueInput>
|
|
HashMapEntry(KeyInput&& aKey, ValueInput&& aValue)
|
|
: key_(std::forward<KeyInput>(aKey)),
|
|
value_(std::forward<ValueInput>(aValue)) {}
|
|
|
|
HashMapEntry(HashMapEntry&& aRhs) = default;
|
|
HashMapEntry& operator=(HashMapEntry&& aRhs) = default;
|
|
|
|
using KeyType = Key;
|
|
using ValueType = Value;
|
|
|
|
const Key& key() const { return key_; }
|
|
|
|
// Use this method with caution! If the key is changed such that its hash
|
|
// value also changes, the map will be left in an invalid state.
|
|
Key& mutableKey() { return key_; }
|
|
|
|
const Value& value() const { return value_; }
|
|
Value& value() { return value_; }
|
|
|
|
private:
|
|
HashMapEntry(const HashMapEntry&) = delete;
|
|
void operator=(const HashMapEntry&) = delete;
|
|
};
|
|
|
|
namespace detail {
|
|
|
|
template <class T, class HashPolicy, class AllocPolicy>
|
|
class HashTable;
|
|
|
|
template <typename T>
|
|
class EntrySlot;
|
|
|
|
template <typename T>
|
|
class HashTableEntry {
|
|
private:
|
|
using NonConstT = std::remove_const_t<T>;
|
|
|
|
// Instead of having a hash table entry store that looks like this:
|
|
//
|
|
// +--------+--------+--------+--------+
|
|
// | entry0 | entry1 | .... | entryN |
|
|
// +--------+--------+--------+--------+
|
|
//
|
|
// where the entries contained their cached hash code, we're going to lay out
|
|
// the entry store thusly:
|
|
//
|
|
// +-------+-------+-------+-------+--------+--------+--------+--------+
|
|
// | hash0 | hash1 | ... | hashN | entry0 | entry1 | .... | entryN |
|
|
// +-------+-------+-------+-------+--------+--------+--------+--------+
|
|
//
|
|
// with all the cached hashes prior to the actual entries themselves.
|
|
//
|
|
// We do this because implementing the first strategy requires us to make
|
|
// HashTableEntry look roughly like:
|
|
//
|
|
// template <typename T>
|
|
// class HashTableEntry {
|
|
// HashNumber mKeyHash;
|
|
// T mValue;
|
|
// };
|
|
//
|
|
// The problem with this setup is that, depending on the layout of `T`, there
|
|
// may be platform ABI-mandated padding between `mKeyHash` and the first
|
|
// member of `T`. This ABI-mandated padding is wasted space, and can be
|
|
// surprisingly common, e.g. when `T` is a single pointer on 64-bit platforms.
|
|
// In such cases, we're throwing away a quarter of our entry store on padding,
|
|
// which is undesirable.
|
|
//
|
|
// The second layout above, namely:
|
|
//
|
|
// +-------+-------+-------+-------+--------+--------+--------+--------+
|
|
// | hash0 | hash1 | ... | hashN | entry0 | entry1 | .... | entryN |
|
|
// +-------+-------+-------+-------+--------+--------+--------+--------+
|
|
//
|
|
// means there is no wasted space between the hashes themselves, and no wasted
|
|
// space between the entries themselves. However, we would also like there to
|
|
// be no gap between the last hash and the first entry. The memory allocator
|
|
// guarantees the alignment of the start of the hashes. The use of a
|
|
// power-of-two capacity of at least 4 guarantees that the alignment of the
|
|
// *end* of the hash array is no less than the alignment of the start.
|
|
// Finally, the static_asserts here guarantee that the entries themselves
|
|
// don't need to be any more aligned than the alignment of the entry store
|
|
// itself.
|
|
//
|
|
// This assertion is safe for 32-bit builds because on both Windows and Linux
|
|
// (including Android), the minimum alignment for allocations larger than 8
|
|
// bytes is 8 bytes, and the actual data for entries in our entry store is
|
|
// guaranteed to have that alignment as well, thanks to the power-of-two
|
|
// number of cached hash values stored prior to the entry data.
|
|
|
|
// The allocation policy must allocate a table with at least this much
|
|
// alignment.
|
|
static constexpr size_t kMinimumAlignment = 8;
|
|
|
|
static_assert(alignof(HashNumber) <= kMinimumAlignment,
|
|
"[N*2 hashes, N*2 T values] allocation's alignment must be "
|
|
"enough to align each hash");
|
|
static_assert(alignof(NonConstT) <= 2 * sizeof(HashNumber),
|
|
"subsequent N*2 T values must not require more than an even "
|
|
"number of HashNumbers provides");
|
|
|
|
static const HashNumber sFreeKey = 0;
|
|
static const HashNumber sRemovedKey = 1;
|
|
static const HashNumber sCollisionBit = 1;
|
|
|
|
alignas(NonConstT) unsigned char mValueData[sizeof(NonConstT)];
|
|
|
|
private:
|
|
template <class, class, class>
|
|
friend class HashTable;
|
|
template <typename>
|
|
friend class EntrySlot;
|
|
|
|
// Some versions of GCC treat it as a -Wstrict-aliasing violation (ergo a
|
|
// -Werror compile error) to reinterpret_cast<> |mValueData| to |T*|, even
|
|
// through |void*|. Placing the latter cast in these separate functions
|
|
// breaks the chain such that affected GCC versions no longer warn/error.
|
|
void* rawValuePtr() { return mValueData; }
|
|
|
|
static bool isLiveHash(HashNumber hash) { return hash > sRemovedKey; }
|
|
|
|
HashTableEntry(const HashTableEntry&) = delete;
|
|
void operator=(const HashTableEntry&) = delete;
|
|
|
|
NonConstT* valuePtr() { return reinterpret_cast<NonConstT*>(rawValuePtr()); }
|
|
|
|
void destroyStoredT() {
|
|
NonConstT* ptr = valuePtr();
|
|
ptr->~T();
|
|
MOZ_MAKE_MEM_UNDEFINED(ptr, sizeof(*ptr));
|
|
}
|
|
|
|
public:
|
|
HashTableEntry() = default;
|
|
|
|
~HashTableEntry() { MOZ_MAKE_MEM_UNDEFINED(this, sizeof(*this)); }
|
|
|
|
void destroy() { destroyStoredT(); }
|
|
|
|
void swap(HashTableEntry* aOther, bool aIsLive) {
|
|
// This allows types to use Argument-Dependent-Lookup, and thus use a custom
|
|
// std::swap, which is needed by types like JS::Heap and such.
|
|
using std::swap;
|
|
|
|
if (this == aOther) {
|
|
return;
|
|
}
|
|
if (aIsLive) {
|
|
swap(*valuePtr(), *aOther->valuePtr());
|
|
} else {
|
|
*aOther->valuePtr() = std::move(*valuePtr());
|
|
destroy();
|
|
}
|
|
}
|
|
|
|
T& get() { return *valuePtr(); }
|
|
|
|
NonConstT& getMutable() { return *valuePtr(); }
|
|
};
|
|
|
|
// A slot represents a cached hash value and its associated entry stored
|
|
// in the hash table. These two things are not stored in contiguous memory.
|
|
template <class T>
|
|
class EntrySlot {
|
|
using NonConstT = std::remove_const_t<T>;
|
|
|
|
using Entry = HashTableEntry<T>;
|
|
|
|
Entry* mEntry;
|
|
HashNumber* mKeyHash;
|
|
|
|
template <class, class, class>
|
|
friend class HashTable;
|
|
|
|
EntrySlot(Entry* aEntry, HashNumber* aKeyHash)
|
|
: mEntry(aEntry), mKeyHash(aKeyHash) {}
|
|
|
|
public:
|
|
static bool isLiveHash(HashNumber hash) { return hash > Entry::sRemovedKey; }
|
|
|
|
EntrySlot(const EntrySlot&) = default;
|
|
EntrySlot(EntrySlot&& aOther) = default;
|
|
|
|
EntrySlot& operator=(const EntrySlot&) = default;
|
|
EntrySlot& operator=(EntrySlot&&) = default;
|
|
|
|
bool operator==(const EntrySlot& aRhs) const { return mEntry == aRhs.mEntry; }
|
|
|
|
bool operator<(const EntrySlot& aRhs) const { return mEntry < aRhs.mEntry; }
|
|
|
|
EntrySlot& operator++() {
|
|
++mEntry;
|
|
++mKeyHash;
|
|
return *this;
|
|
}
|
|
|
|
void destroy() { mEntry->destroy(); }
|
|
|
|
void swap(EntrySlot& aOther) {
|
|
mEntry->swap(aOther.mEntry, aOther.isLive());
|
|
std::swap(*mKeyHash, *aOther.mKeyHash);
|
|
}
|
|
|
|
T& get() const { return mEntry->get(); }
|
|
|
|
NonConstT& getMutable() { return mEntry->getMutable(); }
|
|
|
|
bool isFree() const { return *mKeyHash == Entry::sFreeKey; }
|
|
|
|
void clearLive() {
|
|
MOZ_ASSERT(isLive());
|
|
*mKeyHash = Entry::sFreeKey;
|
|
mEntry->destroyStoredT();
|
|
}
|
|
|
|
void clear() {
|
|
if (isLive()) {
|
|
mEntry->destroyStoredT();
|
|
}
|
|
MOZ_MAKE_MEM_UNDEFINED(mEntry, sizeof(*mEntry));
|
|
*mKeyHash = Entry::sFreeKey;
|
|
}
|
|
|
|
bool isRemoved() const { return *mKeyHash == Entry::sRemovedKey; }
|
|
|
|
void removeLive() {
|
|
MOZ_ASSERT(isLive());
|
|
*mKeyHash = Entry::sRemovedKey;
|
|
mEntry->destroyStoredT();
|
|
}
|
|
|
|
bool isLive() const { return isLiveHash(*mKeyHash); }
|
|
|
|
void setCollision() {
|
|
MOZ_ASSERT(isLive());
|
|
*mKeyHash |= Entry::sCollisionBit;
|
|
}
|
|
void unsetCollision() { *mKeyHash &= ~Entry::sCollisionBit; }
|
|
bool hasCollision() const { return *mKeyHash & Entry::sCollisionBit; }
|
|
bool matchHash(HashNumber hn) {
|
|
return (*mKeyHash & ~Entry::sCollisionBit) == hn;
|
|
}
|
|
HashNumber getKeyHash() const { return *mKeyHash & ~Entry::sCollisionBit; }
|
|
|
|
template <typename... Args>
|
|
void setLive(HashNumber aHashNumber, Args&&... aArgs) {
|
|
MOZ_ASSERT(!isLive());
|
|
*mKeyHash = aHashNumber;
|
|
new (KnownNotNull, mEntry->valuePtr()) T(std::forward<Args>(aArgs)...);
|
|
MOZ_ASSERT(isLive());
|
|
}
|
|
|
|
Entry* toEntry() const { return mEntry; }
|
|
};
|
|
|
|
template <class T, class HashPolicy, class AllocPolicy>
|
|
class HashTable : private AllocPolicy {
|
|
friend class mozilla::ReentrancyGuard;
|
|
|
|
using NonConstT = std::remove_const_t<T>;
|
|
using Key = typename HashPolicy::KeyType;
|
|
using Lookup = typename HashPolicy::Lookup;
|
|
|
|
public:
|
|
using Entry = HashTableEntry<T>;
|
|
using Slot = EntrySlot<T>;
|
|
|
|
template <typename F>
|
|
static void forEachSlot(char* aTable, uint32_t aCapacity, F&& f) {
|
|
auto hashes = reinterpret_cast<HashNumber*>(aTable);
|
|
auto entries = reinterpret_cast<Entry*>(&hashes[aCapacity]);
|
|
Slot slot(entries, hashes);
|
|
for (size_t i = 0; i < size_t(aCapacity); ++i) {
|
|
f(slot);
|
|
++slot;
|
|
}
|
|
}
|
|
|
|
// 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;
|
|
|
|
Slot mSlot;
|
|
#ifdef DEBUG
|
|
const HashTable* mTable;
|
|
Generation mGeneration;
|
|
#endif
|
|
|
|
protected:
|
|
Ptr(Slot aSlot, const HashTable& aTable)
|
|
: mSlot(aSlot)
|
|
#ifdef DEBUG
|
|
,
|
|
mTable(&aTable),
|
|
mGeneration(aTable.generation())
|
|
#endif
|
|
{
|
|
}
|
|
|
|
// This constructor is used only by AddPtr() within lookupForAdd().
|
|
explicit Ptr(const HashTable& aTable)
|
|
: mSlot(nullptr, nullptr)
|
|
#ifdef DEBUG
|
|
,
|
|
mTable(&aTable),
|
|
mGeneration(aTable.generation())
|
|
#endif
|
|
{
|
|
}
|
|
|
|
bool isValid() const { return !!mSlot.toEntry(); }
|
|
|
|
public:
|
|
Ptr()
|
|
: mSlot(nullptr, nullptr)
|
|
#ifdef DEBUG
|
|
,
|
|
mTable(nullptr),
|
|
mGeneration(0)
|
|
#endif
|
|
{
|
|
}
|
|
|
|
bool found() const {
|
|
if (!isValid()) {
|
|
return false;
|
|
}
|
|
#ifdef DEBUG
|
|
MOZ_ASSERT(mGeneration == mTable->generation());
|
|
#endif
|
|
return mSlot.isLive();
|
|
}
|
|
|
|
explicit operator bool() const { return found(); }
|
|
|
|
bool operator==(const Ptr& aRhs) const {
|
|
MOZ_ASSERT(found() && aRhs.found());
|
|
return mSlot == aRhs.mSlot;
|
|
}
|
|
|
|
bool operator!=(const Ptr& aRhs) const {
|
|
#ifdef DEBUG
|
|
MOZ_ASSERT(mGeneration == mTable->generation());
|
|
#endif
|
|
return !(*this == aRhs);
|
|
}
|
|
|
|
T& operator*() const {
|
|
#ifdef DEBUG
|
|
MOZ_ASSERT(found());
|
|
MOZ_ASSERT(mGeneration == mTable->generation());
|
|
#endif
|
|
return mSlot.get();
|
|
}
|
|
|
|
T* operator->() const {
|
|
#ifdef DEBUG
|
|
MOZ_ASSERT(found());
|
|
MOZ_ASSERT(mGeneration == mTable->generation());
|
|
#endif
|
|
return &mSlot.get();
|
|
}
|
|
};
|
|
|
|
// A Ptr that can be used to add a key after a failed lookup.
|
|
class AddPtr : public Ptr {
|
|
friend class HashTable;
|
|
|
|
HashNumber mKeyHash;
|
|
#ifdef DEBUG
|
|
uint64_t mMutationCount;
|
|
#endif
|
|
|
|
AddPtr(Slot aSlot, const HashTable& aTable, HashNumber aHashNumber)
|
|
: Ptr(aSlot, aTable),
|
|
mKeyHash(aHashNumber)
|
|
#ifdef DEBUG
|
|
,
|
|
mMutationCount(aTable.mMutationCount)
|
|
#endif
|
|
{
|
|
}
|
|
|
|
// This constructor is used when lookupForAdd() is performed on a table
|
|
// lacking entry storage; it leaves mSlot null but initializes everything
|
|
// else.
|
|
AddPtr(const HashTable& aTable, HashNumber aHashNumber)
|
|
: Ptr(aTable),
|
|
mKeyHash(aHashNumber)
|
|
#ifdef DEBUG
|
|
,
|
|
mMutationCount(aTable.mMutationCount)
|
|
#endif
|
|
{
|
|
MOZ_ASSERT(isLive());
|
|
}
|
|
|
|
bool isLive() const { return isLiveHash(mKeyHash); }
|
|
|
|
public:
|
|
AddPtr() : mKeyHash(0) {}
|
|
};
|
|
|
|
// A hash table iterator that (mostly) doesn't allow table modifications.
|
|
// As with Ptr/AddPtr, Iterator objects must not be used after any mutating
|
|
// hash table operation unless the |generation()| is tested.
|
|
class Iterator {
|
|
void moveToNextLiveEntry() {
|
|
while (++mCur < mEnd && !mCur.isLive()) {
|
|
continue;
|
|
}
|
|
}
|
|
|
|
protected:
|
|
friend class HashTable;
|
|
|
|
explicit Iterator(const HashTable& aTable)
|
|
: mCur(aTable.slotForIndex(0)),
|
|
mEnd(aTable.slotForIndex(aTable.capacity()))
|
|
#ifdef DEBUG
|
|
,
|
|
mTable(aTable),
|
|
mMutationCount(aTable.mMutationCount),
|
|
mGeneration(aTable.generation()),
|
|
mValidEntry(true)
|
|
#endif
|
|
{
|
|
if (!done() && !mCur.isLive()) {
|
|
moveToNextLiveEntry();
|
|
}
|
|
}
|
|
|
|
Slot mCur;
|
|
Slot mEnd;
|
|
#ifdef DEBUG
|
|
const HashTable& mTable;
|
|
uint64_t mMutationCount;
|
|
Generation mGeneration;
|
|
bool mValidEntry;
|
|
#endif
|
|
|
|
public:
|
|
bool done() const {
|
|
MOZ_ASSERT(mGeneration == mTable.generation());
|
|
MOZ_ASSERT(mMutationCount == mTable.mMutationCount);
|
|
return mCur == mEnd;
|
|
}
|
|
|
|
T& get() const {
|
|
MOZ_ASSERT(!done());
|
|
MOZ_ASSERT(mValidEntry);
|
|
MOZ_ASSERT(mGeneration == mTable.generation());
|
|
MOZ_ASSERT(mMutationCount == mTable.mMutationCount);
|
|
return mCur.get();
|
|
}
|
|
|
|
void next() {
|
|
MOZ_ASSERT(!done());
|
|
MOZ_ASSERT(mGeneration == mTable.generation());
|
|
MOZ_ASSERT(mMutationCount == mTable.mMutationCount);
|
|
moveToNextLiveEntry();
|
|
#ifdef DEBUG
|
|
mValidEntry = true;
|
|
#endif
|
|
}
|
|
};
|
|
|
|
// A hash table iterator that permits modification, removal and rekeying.
|
|
// Since rehashing when elements were removed during enumeration would be
|
|
// bad, it is postponed until the ModIterator is destructed. Since the
|
|
// ModIterator's destructor touches the hash table, the user must ensure
|
|
// that the hash table is still alive when the destructor runs.
|
|
class ModIterator : public Iterator {
|
|
friend class HashTable;
|
|
|
|
HashTable& mTable;
|
|
bool mRekeyed;
|
|
bool mRemoved;
|
|
|
|
// ModIterator is movable but not copyable.
|
|
ModIterator(const ModIterator&) = delete;
|
|
void operator=(const ModIterator&) = delete;
|
|
|
|
protected:
|
|
explicit ModIterator(HashTable& aTable)
|
|
: Iterator(aTable), mTable(aTable), mRekeyed(false), mRemoved(false) {}
|
|
|
|
public:
|
|
MOZ_IMPLICIT ModIterator(ModIterator&& aOther)
|
|
: Iterator(aOther),
|
|
mTable(aOther.mTable),
|
|
mRekeyed(aOther.mRekeyed),
|
|
mRemoved(aOther.mRemoved) {
|
|
aOther.mRekeyed = false;
|
|
aOther.mRemoved = false;
|
|
}
|
|
|
|
// Removes the current element from the table, leaving |get()|
|
|
// invalid until the next call to |next()|.
|
|
void remove() {
|
|
mTable.remove(this->mCur);
|
|
mRemoved = true;
|
|
#ifdef DEBUG
|
|
this->mValidEntry = false;
|
|
this->mMutationCount = mTable.mMutationCount;
|
|
#endif
|
|
}
|
|
|
|
NonConstT& getMutable() {
|
|
MOZ_ASSERT(!this->done());
|
|
MOZ_ASSERT(this->mValidEntry);
|
|
MOZ_ASSERT(this->mGeneration == this->Iterator::mTable.generation());
|
|
MOZ_ASSERT(this->mMutationCount == this->Iterator::mTable.mMutationCount);
|
|
return this->mCur.getMutable();
|
|
}
|
|
|
|
// Removes the current element and re-inserts it into the table with
|
|
// a new key at the new Lookup position. |get()| is invalid after
|
|
// this operation until the next call to |next()|.
|
|
void rekey(const Lookup& l, const Key& k) {
|
|
MOZ_ASSERT(&k != &HashPolicy::getKey(this->mCur.get()));
|
|
Ptr p(this->mCur, mTable);
|
|
mTable.rekeyWithoutRehash(p, l, k);
|
|
mRekeyed = true;
|
|
#ifdef DEBUG
|
|
this->mValidEntry = false;
|
|
this->mMutationCount = mTable.mMutationCount;
|
|
#endif
|
|
}
|
|
|
|
void rekey(const Key& k) { rekey(k, k); }
|
|
|
|
// Potentially rehashes the table.
|
|
~ModIterator() {
|
|
if (mRekeyed) {
|
|
mTable.mGen++;
|
|
mTable.infallibleRehashIfOverloaded();
|
|
}
|
|
|
|
if (mRemoved) {
|
|
mTable.compact();
|
|
}
|
|
}
|
|
};
|
|
|
|
// Range is similar to Iterator, but uses different terminology.
|
|
class Range {
|
|
friend class HashTable;
|
|
|
|
Iterator mIter;
|
|
|
|
protected:
|
|
explicit Range(const HashTable& table) : mIter(table) {}
|
|
|
|
public:
|
|
bool empty() const { return mIter.done(); }
|
|
|
|
T& front() const { return mIter.get(); }
|
|
|
|
void popFront() { return mIter.next(); }
|
|
};
|
|
|
|
// Enum is similar to ModIterator, but uses different terminology.
|
|
class Enum {
|
|
ModIterator mIter;
|
|
|
|
// Enum is movable but not copyable.
|
|
Enum(const Enum&) = delete;
|
|
void operator=(const Enum&) = delete;
|
|
|
|
public:
|
|
template <class Map>
|
|
explicit Enum(Map& map) : mIter(map.mImpl) {}
|
|
|
|
MOZ_IMPLICIT Enum(Enum&& other) : mIter(std::move(other.mIter)) {}
|
|
|
|
bool empty() const { return mIter.done(); }
|
|
|
|
T& front() const { return mIter.get(); }
|
|
|
|
void popFront() { return mIter.next(); }
|
|
|
|
void removeFront() { mIter.remove(); }
|
|
|
|
NonConstT& mutableFront() { return mIter.getMutable(); }
|
|
|
|
void rekeyFront(const Lookup& aLookup, const Key& aKey) {
|
|
mIter.rekey(aLookup, aKey);
|
|
}
|
|
|
|
void rekeyFront(const Key& aKey) { mIter.rekey(aKey); }
|
|
};
|
|
|
|
// HashTable is movable
|
|
HashTable(HashTable&& aRhs) : AllocPolicy(std::move(aRhs)) { moveFrom(aRhs); }
|
|
HashTable& operator=(HashTable&& aRhs) {
|
|
MOZ_ASSERT(this != &aRhs, "self-move assignment is prohibited");
|
|
if (mTable) {
|
|
destroyTable(*this, mTable, capacity());
|
|
}
|
|
AllocPolicy::operator=(std::move(aRhs));
|
|
moveFrom(aRhs);
|
|
return *this;
|
|
}
|
|
|
|
private:
|
|
void moveFrom(HashTable& aRhs) {
|
|
mGen = aRhs.mGen;
|
|
mHashShift = aRhs.mHashShift;
|
|
mTable = aRhs.mTable;
|
|
mEntryCount = aRhs.mEntryCount;
|
|
mRemovedCount = aRhs.mRemovedCount;
|
|
#ifdef DEBUG
|
|
mMutationCount = aRhs.mMutationCount;
|
|
mEntered = aRhs.mEntered;
|
|
#endif
|
|
aRhs.mTable = nullptr;
|
|
aRhs.clearAndCompact();
|
|
}
|
|
|
|
// HashTable is not copyable or assignable
|
|
HashTable(const HashTable&) = delete;
|
|
void operator=(const HashTable&) = delete;
|
|
|
|
static const uint32_t CAP_BITS = 30;
|
|
|
|
public:
|
|
uint64_t mGen : 56; // entry storage generation number
|
|
uint64_t mHashShift : 8; // multiplicative hash shift
|
|
char* mTable; // entry storage
|
|
uint32_t mEntryCount; // number of entries in mTable
|
|
uint32_t mRemovedCount; // removed entry sentinels in mTable
|
|
|
|
#ifdef DEBUG
|
|
uint64_t mMutationCount;
|
|
mutable bool mEntered;
|
|
#endif
|
|
|
|
// The default initial capacity is 32 (enough to hold 16 elements), but it
|
|
// can be as low as 4.
|
|
static const uint32_t sDefaultLen = 16;
|
|
static const uint32_t sMinCapacity = 4;
|
|
// See the comments in HashTableEntry about this value.
|
|
static_assert(sMinCapacity >= 4, "too-small sMinCapacity breaks assumptions");
|
|
static const uint32_t sMaxInit = 1u << (CAP_BITS - 1);
|
|
static const uint32_t sMaxCapacity = 1u << CAP_BITS;
|
|
|
|
// Hash-table alpha is conceptually a fraction, but to avoid floating-point
|
|
// math we implement it as a ratio of integers.
|
|
static const uint8_t sAlphaDenominator = 4;
|
|
static const uint8_t sMinAlphaNumerator = 1; // min alpha: 1/4
|
|
static const uint8_t sMaxAlphaNumerator = 3; // max alpha: 3/4
|
|
|
|
static const HashNumber sFreeKey = Entry::sFreeKey;
|
|
static const HashNumber sRemovedKey = Entry::sRemovedKey;
|
|
static const HashNumber sCollisionBit = Entry::sCollisionBit;
|
|
|
|
static uint32_t bestCapacity(uint32_t aLen) {
|
|
static_assert(
|
|
(sMaxInit * sAlphaDenominator) / sAlphaDenominator == sMaxInit,
|
|
"multiplication in numerator below could overflow");
|
|
static_assert(
|
|
sMaxInit * sAlphaDenominator <= UINT32_MAX - sMaxAlphaNumerator,
|
|
"numerator calculation below could potentially overflow");
|
|
|
|
// Callers should ensure this is true.
|
|
MOZ_ASSERT(aLen <= sMaxInit);
|
|
|
|
// Compute the smallest capacity allowing |aLen| elements to be
|
|
// inserted without rehashing: ceil(aLen / max-alpha). (Ceiling
|
|
// integral division: <http://stackoverflow.com/a/2745086>.)
|
|
uint32_t capacity = (aLen * sAlphaDenominator + sMaxAlphaNumerator - 1) /
|
|
sMaxAlphaNumerator;
|
|
capacity = (capacity < sMinCapacity) ? sMinCapacity : RoundUpPow2(capacity);
|
|
|
|
MOZ_ASSERT(capacity >= aLen);
|
|
MOZ_ASSERT(capacity <= sMaxCapacity);
|
|
|
|
return capacity;
|
|
}
|
|
|
|
static uint32_t hashShift(uint32_t aLen) {
|
|
// Reject all lengths whose initial computed capacity would exceed
|
|
// sMaxCapacity. Round that maximum aLen down to the nearest power of two
|
|
// for speedier code.
|
|
if (MOZ_UNLIKELY(aLen > sMaxInit)) {
|
|
MOZ_CRASH("initial length is too large");
|
|
}
|
|
|
|
return kHashNumberBits - mozilla::CeilingLog2(bestCapacity(aLen));
|
|
}
|
|
|
|
static bool isLiveHash(HashNumber aHash) { return Entry::isLiveHash(aHash); }
|
|
|
|
static HashNumber prepareHash(const Lookup& aLookup) {
|
|
HashNumber keyHash = ScrambleHashCode(HashPolicy::hash(aLookup));
|
|
|
|
// Avoid reserved hash codes.
|
|
if (!isLiveHash(keyHash)) {
|
|
keyHash -= (sRemovedKey + 1);
|
|
}
|
|
return keyHash & ~sCollisionBit;
|
|
}
|
|
|
|
enum FailureBehavior { DontReportFailure = false, ReportFailure = true };
|
|
|
|
// Fake a struct that we're going to alloc. See the comments in
|
|
// HashTableEntry about how the table is laid out, and why it's safe.
|
|
struct FakeSlot {
|
|
unsigned char c[sizeof(HashNumber) + sizeof(typename Entry::NonConstT)];
|
|
};
|
|
|
|
static char* createTable(AllocPolicy& aAllocPolicy, uint32_t aCapacity,
|
|
FailureBehavior aReportFailure = ReportFailure) {
|
|
FakeSlot* fake =
|
|
aReportFailure
|
|
? aAllocPolicy.template pod_malloc<FakeSlot>(aCapacity)
|
|
: aAllocPolicy.template maybe_pod_malloc<FakeSlot>(aCapacity);
|
|
|
|
MOZ_ASSERT((reinterpret_cast<uintptr_t>(fake) % Entry::kMinimumAlignment) ==
|
|
0);
|
|
|
|
char* table = reinterpret_cast<char*>(fake);
|
|
if (table) {
|
|
forEachSlot(table, aCapacity, [&](Slot& slot) {
|
|
*slot.mKeyHash = sFreeKey;
|
|
new (KnownNotNull, slot.toEntry()) Entry();
|
|
});
|
|
}
|
|
return table;
|
|
}
|
|
|
|
static void destroyTable(AllocPolicy& aAllocPolicy, char* aOldTable,
|
|
uint32_t aCapacity) {
|
|
forEachSlot(aOldTable, aCapacity, [&](const Slot& slot) {
|
|
if (slot.isLive()) {
|
|
slot.toEntry()->destroyStoredT();
|
|
}
|
|
});
|
|
freeTable(aAllocPolicy, aOldTable, aCapacity);
|
|
}
|
|
|
|
static void freeTable(AllocPolicy& aAllocPolicy, char* aOldTable,
|
|
uint32_t aCapacity) {
|
|
FakeSlot* fake = reinterpret_cast<FakeSlot*>(aOldTable);
|
|
aAllocPolicy.free_(fake, aCapacity);
|
|
}
|
|
|
|
public:
|
|
HashTable(AllocPolicy aAllocPolicy, uint32_t aLen)
|
|
: AllocPolicy(std::move(aAllocPolicy)),
|
|
mGen(0),
|
|
mHashShift(hashShift(aLen)),
|
|
mTable(nullptr),
|
|
mEntryCount(0),
|
|
mRemovedCount(0)
|
|
#ifdef DEBUG
|
|
,
|
|
mMutationCount(0),
|
|
mEntered(false)
|
|
#endif
|
|
{
|
|
}
|
|
|
|
explicit HashTable(AllocPolicy aAllocPolicy)
|
|
: HashTable(aAllocPolicy, sDefaultLen) {}
|
|
|
|
~HashTable() {
|
|
if (mTable) {
|
|
destroyTable(*this, mTable, capacity());
|
|
}
|
|
}
|
|
|
|
private:
|
|
HashNumber hash1(HashNumber aHash0) const { return aHash0 >> mHashShift; }
|
|
|
|
struct DoubleHash {
|
|
HashNumber mHash2;
|
|
HashNumber mSizeMask;
|
|
};
|
|
|
|
DoubleHash hash2(HashNumber aCurKeyHash) const {
|
|
uint32_t sizeLog2 = kHashNumberBits - mHashShift;
|
|
DoubleHash dh = {((aCurKeyHash << sizeLog2) >> mHashShift) | 1,
|
|
(HashNumber(1) << sizeLog2) - 1};
|
|
return dh;
|
|
}
|
|
|
|
static HashNumber applyDoubleHash(HashNumber aHash1,
|
|
const DoubleHash& aDoubleHash) {
|
|
return WrappingSubtract(aHash1, aDoubleHash.mHash2) & aDoubleHash.mSizeMask;
|
|
}
|
|
|
|
static MOZ_ALWAYS_INLINE bool match(T& aEntry, const Lookup& aLookup) {
|
|
return HashPolicy::match(HashPolicy::getKey(aEntry), aLookup);
|
|
}
|
|
|
|
enum LookupReason { ForNonAdd, ForAdd };
|
|
|
|
Slot slotForIndex(HashNumber aIndex) const {
|
|
auto hashes = reinterpret_cast<HashNumber*>(mTable);
|
|
auto entries = reinterpret_cast<Entry*>(&hashes[capacity()]);
|
|
return Slot(&entries[aIndex], &hashes[aIndex]);
|
|
}
|
|
|
|
// Warning: in order for readonlyThreadsafeLookup() to be safe this
|
|
// function must not modify the table in any way when Reason==ForNonAdd.
|
|
template <LookupReason Reason>
|
|
MOZ_ALWAYS_INLINE Slot lookup(const Lookup& aLookup,
|
|
HashNumber aKeyHash) const {
|
|
MOZ_ASSERT(isLiveHash(aKeyHash));
|
|
MOZ_ASSERT(!(aKeyHash & sCollisionBit));
|
|
MOZ_ASSERT(mTable);
|
|
|
|
// Compute the primary hash address.
|
|
HashNumber h1 = hash1(aKeyHash);
|
|
Slot slot = slotForIndex(h1);
|
|
|
|
// Miss: return space for a new entry.
|
|
if (slot.isFree()) {
|
|
return slot;
|
|
}
|
|
|
|
// Hit: return entry.
|
|
if (slot.matchHash(aKeyHash) && match(slot.get(), aLookup)) {
|
|
return slot;
|
|
}
|
|
|
|
// Collision: double hash.
|
|
DoubleHash dh = hash2(aKeyHash);
|
|
|
|
// Save the first removed entry pointer so we can recycle later.
|
|
Maybe<Slot> firstRemoved;
|
|
|
|
while (true) {
|
|
if (Reason == ForAdd && !firstRemoved) {
|
|
if (MOZ_UNLIKELY(slot.isRemoved())) {
|
|
firstRemoved.emplace(slot);
|
|
} else {
|
|
slot.setCollision();
|
|
}
|
|
}
|
|
|
|
h1 = applyDoubleHash(h1, dh);
|
|
|
|
slot = slotForIndex(h1);
|
|
if (slot.isFree()) {
|
|
return firstRemoved.refOr(slot);
|
|
}
|
|
|
|
if (slot.matchHash(aKeyHash) && match(slot.get(), aLookup)) {
|
|
return slot;
|
|
}
|
|
}
|
|
}
|
|
|
|
// This is a copy of lookup() hardcoded to the assumptions:
|
|
// 1. the lookup is for an add;
|
|
// 2. the key, whose |keyHash| has been passed, is not in the table.
|
|
Slot findNonLiveSlot(HashNumber aKeyHash) {
|
|
MOZ_ASSERT(!(aKeyHash & sCollisionBit));
|
|
MOZ_ASSERT(mTable);
|
|
|
|
// We assume 'aKeyHash' has already been distributed.
|
|
|
|
// Compute the primary hash address.
|
|
HashNumber h1 = hash1(aKeyHash);
|
|
Slot slot = slotForIndex(h1);
|
|
|
|
// Miss: return space for a new entry.
|
|
if (!slot.isLive()) {
|
|
return slot;
|
|
}
|
|
|
|
// Collision: double hash.
|
|
DoubleHash dh = hash2(aKeyHash);
|
|
|
|
while (true) {
|
|
slot.setCollision();
|
|
|
|
h1 = applyDoubleHash(h1, dh);
|
|
|
|
slot = slotForIndex(h1);
|
|
if (!slot.isLive()) {
|
|
return slot;
|
|
}
|
|
}
|
|
}
|
|
|
|
enum RebuildStatus { NotOverloaded, Rehashed, RehashFailed };
|
|
|
|
RebuildStatus changeTableSize(
|
|
uint32_t newCapacity, FailureBehavior aReportFailure = ReportFailure) {
|
|
MOZ_ASSERT(IsPowerOfTwo(newCapacity));
|
|
MOZ_ASSERT(!!mTable == !!capacity());
|
|
|
|
// Look, but don't touch, until we succeed in getting new entry store.
|
|
char* oldTable = mTable;
|
|
uint32_t oldCapacity = capacity();
|
|
uint32_t newLog2 = mozilla::CeilingLog2(newCapacity);
|
|
|
|
if (MOZ_UNLIKELY(newCapacity > sMaxCapacity)) {
|
|
if (aReportFailure) {
|
|
this->reportAllocOverflow();
|
|
}
|
|
return RehashFailed;
|
|
}
|
|
|
|
char* newTable = createTable(*this, newCapacity, aReportFailure);
|
|
if (!newTable) {
|
|
return RehashFailed;
|
|
}
|
|
|
|
// We can't fail from here on, so update table parameters.
|
|
mHashShift = kHashNumberBits - newLog2;
|
|
mRemovedCount = 0;
|
|
mGen++;
|
|
mTable = newTable;
|
|
|
|
// Copy only live entries, leaving removed ones behind.
|
|
forEachSlot(oldTable, oldCapacity, [&](Slot& slot) {
|
|
if (slot.isLive()) {
|
|
HashNumber hn = slot.getKeyHash();
|
|
findNonLiveSlot(hn).setLive(
|
|
hn, std::move(const_cast<typename Entry::NonConstT&>(slot.get())));
|
|
}
|
|
|
|
slot.clear();
|
|
});
|
|
|
|
// All entries have been destroyed, no need to destroyTable.
|
|
freeTable(*this, oldTable, oldCapacity);
|
|
return Rehashed;
|
|
}
|
|
|
|
RebuildStatus rehashIfOverloaded(
|
|
FailureBehavior aReportFailure = ReportFailure) {
|
|
static_assert(sMaxCapacity <= UINT32_MAX / sMaxAlphaNumerator,
|
|
"multiplication below could overflow");
|
|
|
|
// Note: if capacity() is zero, this will always succeed, which is
|
|
// what we want.
|
|
bool overloaded = mEntryCount + mRemovedCount >=
|
|
capacity() * sMaxAlphaNumerator / sAlphaDenominator;
|
|
|
|
if (!overloaded) {
|
|
return NotOverloaded;
|
|
}
|
|
|
|
// Succeed if a quarter or more of all entries are removed. Note that this
|
|
// always succeeds if capacity() == 0 (i.e. entry storage has not been
|
|
// allocated), which is what we want, because it means changeTableSize()
|
|
// will allocate the requested capacity rather than doubling it.
|
|
bool manyRemoved = mRemovedCount >= (capacity() >> 2);
|
|
uint32_t newCapacity = manyRemoved ? rawCapacity() : rawCapacity() * 2;
|
|
return changeTableSize(newCapacity, aReportFailure);
|
|
}
|
|
|
|
void infallibleRehashIfOverloaded() {
|
|
if (rehashIfOverloaded(DontReportFailure) == RehashFailed) {
|
|
rehashTableInPlace();
|
|
}
|
|
}
|
|
|
|
void remove(Slot& aSlot) {
|
|
MOZ_ASSERT(mTable);
|
|
|
|
if (aSlot.hasCollision()) {
|
|
aSlot.removeLive();
|
|
mRemovedCount++;
|
|
} else {
|
|
aSlot.clearLive();
|
|
}
|
|
mEntryCount--;
|
|
#ifdef DEBUG
|
|
mMutationCount++;
|
|
#endif
|
|
}
|
|
|
|
void shrinkIfUnderloaded() {
|
|
static_assert(sMaxCapacity <= UINT32_MAX / sMinAlphaNumerator,
|
|
"multiplication below could overflow");
|
|
bool underloaded =
|
|
capacity() > sMinCapacity &&
|
|
mEntryCount <= capacity() * sMinAlphaNumerator / sAlphaDenominator;
|
|
|
|
if (underloaded) {
|
|
(void)changeTableSize(capacity() / 2, DontReportFailure);
|
|
}
|
|
}
|
|
|
|
// This is identical to changeTableSize(currentSize), but without requiring
|
|
// a second table. We do this by recycling the collision bits to tell us if
|
|
// the element is already inserted or still waiting to be inserted. Since
|
|
// already-inserted elements win any conflicts, we get the same table as we
|
|
// would have gotten through random insertion order.
|
|
void rehashTableInPlace() {
|
|
mRemovedCount = 0;
|
|
mGen++;
|
|
forEachSlot(mTable, capacity(), [&](Slot& slot) { slot.unsetCollision(); });
|
|
for (uint32_t i = 0; i < capacity();) {
|
|
Slot src = slotForIndex(i);
|
|
|
|
if (!src.isLive() || src.hasCollision()) {
|
|
++i;
|
|
continue;
|
|
}
|
|
|
|
HashNumber keyHash = src.getKeyHash();
|
|
HashNumber h1 = hash1(keyHash);
|
|
DoubleHash dh = hash2(keyHash);
|
|
Slot tgt = slotForIndex(h1);
|
|
while (true) {
|
|
if (!tgt.hasCollision()) {
|
|
src.swap(tgt);
|
|
tgt.setCollision();
|
|
break;
|
|
}
|
|
|
|
h1 = applyDoubleHash(h1, dh);
|
|
tgt = slotForIndex(h1);
|
|
}
|
|
}
|
|
|
|
// TODO: this algorithm leaves collision bits on *all* elements, even if
|
|
// they are on no collision path. We have the option of setting the
|
|
// collision bits correctly on a subsequent pass or skipping the rehash
|
|
// unless we are totally filled with tombstones: benchmark to find out
|
|
// which approach is best.
|
|
}
|
|
|
|
// Note: |aLookup| may be a reference to a piece of |u|, so this function
|
|
// must take care not to use |aLookup| after moving |u|.
|
|
//
|
|
// Prefer to use putNewInfallible; this function does not check
|
|
// invariants.
|
|
template <typename... Args>
|
|
void putNewInfallibleInternal(const Lookup& aLookup, Args&&... aArgs) {
|
|
MOZ_ASSERT(mTable);
|
|
|
|
HashNumber keyHash = prepareHash(aLookup);
|
|
Slot slot = findNonLiveSlot(keyHash);
|
|
|
|
if (slot.isRemoved()) {
|
|
mRemovedCount--;
|
|
keyHash |= sCollisionBit;
|
|
}
|
|
|
|
slot.setLive(keyHash, std::forward<Args>(aArgs)...);
|
|
mEntryCount++;
|
|
#ifdef DEBUG
|
|
mMutationCount++;
|
|
#endif
|
|
}
|
|
|
|
public:
|
|
void clear() {
|
|
forEachSlot(mTable, capacity(), [&](Slot& slot) { slot.clear(); });
|
|
mRemovedCount = 0;
|
|
mEntryCount = 0;
|
|
#ifdef DEBUG
|
|
mMutationCount++;
|
|
#endif
|
|
}
|
|
|
|
// Resize the table down to the smallest capacity that doesn't overload the
|
|
// table. Since we call shrinkIfUnderloaded() on every remove, you only need
|
|
// to call this after a bulk removal of items done without calling remove().
|
|
void compact() {
|
|
if (empty()) {
|
|
// Free the entry storage.
|
|
freeTable(*this, mTable, capacity());
|
|
mGen++;
|
|
mHashShift = hashShift(0); // gives minimum capacity on regrowth
|
|
mTable = nullptr;
|
|
mRemovedCount = 0;
|
|
return;
|
|
}
|
|
|
|
uint32_t bestCapacity = this->bestCapacity(mEntryCount);
|
|
MOZ_ASSERT(bestCapacity <= capacity());
|
|
|
|
if (bestCapacity < capacity()) {
|
|
(void)changeTableSize(bestCapacity, DontReportFailure);
|
|
}
|
|
}
|
|
|
|
void clearAndCompact() {
|
|
clear();
|
|
compact();
|
|
}
|
|
|
|
[[nodiscard]] bool reserve(uint32_t aLen) {
|
|
if (aLen == 0) {
|
|
return true;
|
|
}
|
|
|
|
if (MOZ_UNLIKELY(aLen > sMaxInit)) {
|
|
return false;
|
|
}
|
|
|
|
uint32_t bestCapacity = this->bestCapacity(aLen);
|
|
if (bestCapacity <= capacity()) {
|
|
return true; // Capacity is already sufficient.
|
|
}
|
|
|
|
RebuildStatus status = changeTableSize(bestCapacity, ReportFailure);
|
|
MOZ_ASSERT(status != NotOverloaded);
|
|
return status != RehashFailed;
|
|
}
|
|
|
|
Iterator iter() const { return Iterator(*this); }
|
|
|
|
ModIterator modIter() { return ModIterator(*this); }
|
|
|
|
Range all() const { return Range(*this); }
|
|
|
|
bool empty() const { return mEntryCount == 0; }
|
|
|
|
uint32_t count() const { return mEntryCount; }
|
|
|
|
uint32_t rawCapacity() const { return 1u << (kHashNumberBits - mHashShift); }
|
|
|
|
uint32_t capacity() const { return mTable ? rawCapacity() : 0; }
|
|
|
|
Generation generation() const { return Generation(mGen); }
|
|
|
|
size_t shallowSizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
|
|
return aMallocSizeOf(mTable);
|
|
}
|
|
|
|
size_t shallowSizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
|
|
return aMallocSizeOf(this) + shallowSizeOfExcludingThis(aMallocSizeOf);
|
|
}
|
|
|
|
MOZ_ALWAYS_INLINE Ptr readonlyThreadsafeLookup(const Lookup& aLookup) const {
|
|
if (empty() || !HasHash<HashPolicy>(aLookup)) {
|
|
return Ptr();
|
|
}
|
|
HashNumber keyHash = prepareHash(aLookup);
|
|
return Ptr(lookup<ForNonAdd>(aLookup, keyHash), *this);
|
|
}
|
|
|
|
MOZ_ALWAYS_INLINE Ptr lookup(const Lookup& aLookup) const {
|
|
ReentrancyGuard g(*this);
|
|
return readonlyThreadsafeLookup(aLookup);
|
|
}
|
|
|
|
MOZ_ALWAYS_INLINE AddPtr lookupForAdd(const Lookup& aLookup) {
|
|
ReentrancyGuard g(*this);
|
|
if (!EnsureHash<HashPolicy>(aLookup)) {
|
|
return AddPtr();
|
|
}
|
|
|
|
HashNumber keyHash = prepareHash(aLookup);
|
|
|
|
if (!mTable) {
|
|
return AddPtr(*this, keyHash);
|
|
}
|
|
|
|
// Directly call the constructor in the return statement to avoid
|
|
// excess copying when building with Visual Studio 2017.
|
|
// See bug 1385181.
|
|
return AddPtr(lookup<ForAdd>(aLookup, keyHash), *this, keyHash);
|
|
}
|
|
|
|
template <typename... Args>
|
|
[[nodiscard]] bool add(AddPtr& aPtr, Args&&... aArgs) {
|
|
ReentrancyGuard g(*this);
|
|
MOZ_ASSERT_IF(aPtr.isValid(), mTable);
|
|
MOZ_ASSERT_IF(aPtr.isValid(), aPtr.mTable == this);
|
|
MOZ_ASSERT(!aPtr.found());
|
|
MOZ_ASSERT(!(aPtr.mKeyHash & sCollisionBit));
|
|
|
|
// Check for error from ensureHash() here.
|
|
if (!aPtr.isLive()) {
|
|
return false;
|
|
}
|
|
|
|
MOZ_ASSERT(aPtr.mGeneration == generation());
|
|
#ifdef DEBUG
|
|
MOZ_ASSERT(aPtr.mMutationCount == mMutationCount);
|
|
#endif
|
|
|
|
if (!aPtr.isValid()) {
|
|
MOZ_ASSERT(!mTable && mEntryCount == 0);
|
|
uint32_t newCapacity = rawCapacity();
|
|
RebuildStatus status = changeTableSize(newCapacity, ReportFailure);
|
|
MOZ_ASSERT(status != NotOverloaded);
|
|
if (status == RehashFailed) {
|
|
return false;
|
|
}
|
|
aPtr.mSlot = findNonLiveSlot(aPtr.mKeyHash);
|
|
|
|
} else if (aPtr.mSlot.isRemoved()) {
|
|
// Changing an entry from removed to live does not affect whether we are
|
|
// overloaded and can be handled separately.
|
|
if (!this->checkSimulatedOOM()) {
|
|
return false;
|
|
}
|
|
mRemovedCount--;
|
|
aPtr.mKeyHash |= sCollisionBit;
|
|
|
|
} else {
|
|
// Preserve the validity of |aPtr.mSlot|.
|
|
RebuildStatus status = rehashIfOverloaded();
|
|
if (status == RehashFailed) {
|
|
return false;
|
|
}
|
|
if (status == NotOverloaded && !this->checkSimulatedOOM()) {
|
|
return false;
|
|
}
|
|
if (status == Rehashed) {
|
|
aPtr.mSlot = findNonLiveSlot(aPtr.mKeyHash);
|
|
}
|
|
}
|
|
|
|
aPtr.mSlot.setLive(aPtr.mKeyHash, std::forward<Args>(aArgs)...);
|
|
mEntryCount++;
|
|
#ifdef DEBUG
|
|
mMutationCount++;
|
|
aPtr.mGeneration = generation();
|
|
aPtr.mMutationCount = mMutationCount;
|
|
#endif
|
|
return true;
|
|
}
|
|
|
|
// Note: |aLookup| may be a reference to a piece of |u|, so this function
|
|
// must take care not to use |aLookup| after moving |u|.
|
|
template <typename... Args>
|
|
void putNewInfallible(const Lookup& aLookup, Args&&... aArgs) {
|
|
MOZ_ASSERT(!lookup(aLookup).found());
|
|
ReentrancyGuard g(*this);
|
|
putNewInfallibleInternal(aLookup, std::forward<Args>(aArgs)...);
|
|
}
|
|
|
|
// Note: |aLookup| may be alias arguments in |aArgs|, so this function must
|
|
// take care not to use |aLookup| after moving |aArgs|.
|
|
template <typename... Args>
|
|
[[nodiscard]] bool putNew(const Lookup& aLookup, Args&&... aArgs) {
|
|
if (!this->checkSimulatedOOM()) {
|
|
return false;
|
|
}
|
|
if (!EnsureHash<HashPolicy>(aLookup)) {
|
|
return false;
|
|
}
|
|
if (rehashIfOverloaded() == RehashFailed) {
|
|
return false;
|
|
}
|
|
putNewInfallible(aLookup, std::forward<Args>(aArgs)...);
|
|
return true;
|
|
}
|
|
|
|
// Note: |aLookup| may be a reference to a piece of |u|, so this function
|
|
// must take care not to use |aLookup| after moving |u|.
|
|
template <typename... Args>
|
|
[[nodiscard]] bool relookupOrAdd(AddPtr& aPtr, const Lookup& aLookup,
|
|
Args&&... aArgs) {
|
|
// Check for error from ensureHash() here.
|
|
if (!aPtr.isLive()) {
|
|
return false;
|
|
}
|
|
#ifdef DEBUG
|
|
aPtr.mGeneration = generation();
|
|
aPtr.mMutationCount = mMutationCount;
|
|
#endif
|
|
if (mTable) {
|
|
ReentrancyGuard g(*this);
|
|
// Check that aLookup has not been destroyed.
|
|
MOZ_ASSERT(prepareHash(aLookup) == aPtr.mKeyHash);
|
|
aPtr.mSlot = lookup<ForAdd>(aLookup, aPtr.mKeyHash);
|
|
if (aPtr.found()) {
|
|
return true;
|
|
}
|
|
} else {
|
|
// Clear aPtr so it's invalid; add() will allocate storage and redo the
|
|
// lookup.
|
|
aPtr.mSlot = Slot(nullptr, nullptr);
|
|
}
|
|
return add(aPtr, std::forward<Args>(aArgs)...);
|
|
}
|
|
|
|
void remove(Ptr aPtr) {
|
|
MOZ_ASSERT(mTable);
|
|
ReentrancyGuard g(*this);
|
|
MOZ_ASSERT(aPtr.found());
|
|
MOZ_ASSERT(aPtr.mGeneration == generation());
|
|
remove(aPtr.mSlot);
|
|
shrinkIfUnderloaded();
|
|
}
|
|
|
|
void rekeyWithoutRehash(Ptr aPtr, const Lookup& aLookup, const Key& aKey) {
|
|
MOZ_ASSERT(mTable);
|
|
ReentrancyGuard g(*this);
|
|
MOZ_ASSERT(aPtr.found());
|
|
MOZ_ASSERT(aPtr.mGeneration == generation());
|
|
typename HashTableEntry<T>::NonConstT t(std::move(*aPtr));
|
|
HashPolicy::setKey(t, const_cast<Key&>(aKey));
|
|
remove(aPtr.mSlot);
|
|
putNewInfallibleInternal(aLookup, std::move(t));
|
|
}
|
|
|
|
void rekeyAndMaybeRehash(Ptr aPtr, const Lookup& aLookup, const Key& aKey) {
|
|
rekeyWithoutRehash(aPtr, aLookup, aKey);
|
|
infallibleRehashIfOverloaded();
|
|
}
|
|
};
|
|
|
|
} // namespace detail
|
|
} // namespace mozilla
|
|
|
|
#endif /* mozilla_HashTable_h */
|