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84 lines
2.8 KiB
C++
84 lines
2.8 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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#ifndef mozilla_recordreplay_ValueIndex_h
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#define mozilla_recordreplay_ValueIndex_h
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#include "mozilla/Types.h"
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#include <unordered_map>
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namespace mozilla {
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namespace recordreplay {
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// ValueIndexes are a bidirectional map between arbitrary pointers and indexes.
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// These are used while recording and replaying to handle the general issue
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// that pointer values are not preserved during replay: recording a pointer and
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// replaying its bits later will not yield a pointer to the same heap value,
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// but rather a pointer to garbage that must not be dereferenced.
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//
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// When entries are added to a ValueIndex at consistent points between
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// recording and replaying, then the resulting indexes will be consistent, and
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// that index can be recorded and later replayed and used to find the
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// replay-specific pointer value corresponding to the pointer used at that
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// point in the recording. Entries can be removed from the ValueIndex at
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// different points in the recording and replay without affecting the indexes
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// that will be generated later.
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//
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// This is a helper class that is used in various places to help record/replay
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// pointers to heap data.
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class ValueIndex
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{
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public:
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ValueIndex()
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: mIndexCount(0)
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{}
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typedef std::unordered_map<const void*, size_t> ValueToIndexMap;
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// Add a new entry to the map.
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size_t Insert(const void* aValue);
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// Remove an entry from the map, unless there is no entry for aValue.
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void Remove(const void* aValue);
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// Get the index for an entry in the map. The entry must exist in the map.
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size_t GetIndex(const void* aValue);
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// Get the index for an entry in the map if there is one, otherwise return
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// false.
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bool MaybeGetIndex(const void* aValue, size_t* aIndex);
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// Return whether there is an entry for aValue.
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bool Contains(const void* aValue);
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// Get the value associated with an index. The index must exist in the map.
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const void* GetValue(size_t aIndex);
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// Whether the map is empty.
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bool IsEmpty();
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// Raw read-only access to the map contents.
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const ValueToIndexMap& GetValueToIndexMap();
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private:
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typedef std::unordered_map<size_t, const void*> IndexToValueMap;
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// Map from pointer values to indexes.
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ValueToIndexMap mValueToIndex;
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// Map from indexes to pointer values.
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IndexToValueMap mIndexToValue;
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// The total number of entries that have ever been added to this map.
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size_t mIndexCount;
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};
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} // namespace recordreplay
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} // namespace mozilla
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#endif // mozilla_recordreplay_ValueIndex_h
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