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dca62ba9ee
This is much simpler and lets us tidy up the addProperty code more. It also makes it easier to change ShapeTable for property maps in the future. Lookup performance and memory usage appear to be similar for the two versions, probably because ShapeTable used the same double-hashing algorithm and because we can purge most ShapeTables on GC. Differential Revision: https://phabricator.services.mozilla.com/D113089
2246 lines
70 KiB
C++
2246 lines
70 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. Does
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// nothing if the 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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AddPtr p = lookupForAdd(aKey);
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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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//---------------------------------------------------------------------------
|
|
|
|
// HashSet is a fast hash-based set of values.
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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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|
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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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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;
|
|
HashSet& operator=(HashSet&& aRhs) = default;
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|
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// -- Status and sizing ----------------------------------------------------
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|
|
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// The set's current generation.
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Generation generation() const { return mImpl.generation(); }
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// Is the set empty?
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bool empty() const { return mImpl.empty(); }
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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().
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uint32_t capacity() const { return mImpl.capacity(); }
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|
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// 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. 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 */
|