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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
commit | 0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d (patch) | |
tree | a31f07c9bcca9d56ce61e9a1ffd30ef350d513aa /intl/icu/source/common/sharedobject.h | |
parent | Initial commit. (diff) | |
download | firefox-esr-0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d.tar.xz firefox-esr-0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d.zip |
Adding upstream version 115.8.0esr.upstream/115.8.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'intl/icu/source/common/sharedobject.h')
-rw-r--r-- | intl/icu/source/common/sharedobject.h | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/intl/icu/source/common/sharedobject.h b/intl/icu/source/common/sharedobject.h new file mode 100644 index 0000000000..5532ec48d8 --- /dev/null +++ b/intl/icu/source/common/sharedobject.h @@ -0,0 +1,184 @@ +// © 2016 and later: Unicode, Inc. and others. +// License & terms of use: http://www.unicode.org/copyright.html +/* +****************************************************************************** +* Copyright (C) 2015-2016, International Business Machines +* Corporation and others. All Rights Reserved. +****************************************************************************** +* sharedobject.h +*/ + +#ifndef __SHAREDOBJECT_H__ +#define __SHAREDOBJECT_H__ + + +#include "unicode/uobject.h" +#include "umutex.h" + +U_NAMESPACE_BEGIN + +class SharedObject; + +/** + * Base class for unified cache exposing enough methods to SharedObject + * instances to allow their addRef() and removeRef() methods to + * update cache metrics. No other part of ICU, except for SharedObject, + * should directly call the methods of this base class. + */ +class U_COMMON_API UnifiedCacheBase : public UObject { +public: + UnifiedCacheBase() { } + + /** + * Notify the cache implementation that an object was seen transitioning to + * zero hard references. The cache may use this to keep track the number of + * unreferenced SharedObjects, and to trigger evictions. + */ + virtual void handleUnreferencedObject() const = 0; + + virtual ~UnifiedCacheBase(); +private: + UnifiedCacheBase(const UnifiedCacheBase &) = delete; + UnifiedCacheBase &operator=(const UnifiedCacheBase &) = delete; +}; + +/** + * Base class for shared, reference-counted, auto-deleted objects. + * Subclasses can be immutable. + * If they are mutable, then they must implement their copy constructor + * so that copyOnWrite() works. + * + * Either stack-allocate, use LocalPointer, or use addRef()/removeRef(). + * Sharing requires reference-counting. + */ +class U_COMMON_API SharedObject : public UObject { +public: + /** Initializes totalRefCount, softRefCount to 0. */ + SharedObject() : + softRefCount(0), + hardRefCount(0), + cachePtr(nullptr) {} + + /** Initializes totalRefCount, softRefCount to 0. */ + SharedObject(const SharedObject &other) : + UObject(other), + softRefCount(0), + hardRefCount(0), + cachePtr(nullptr) {} + + virtual ~SharedObject(); + + /** + * Increments the number of hard references to this object. Thread-safe. + * Not for use from within the Unified Cache implementation. + */ + void addRef() const; + + /** + * Decrements the number of hard references to this object, and + * arrange for possible cache-eviction and/or deletion if ref + * count goes to zero. Thread-safe. + * + * Not for use from within the UnifiedCache implementation. + */ + void removeRef() const; + + /** + * Returns the number of hard references for this object. + * Uses a memory barrier. + */ + int32_t getRefCount() const; + + /** + * If noHardReferences() == true then this object has no hard references. + * Must be called only from within the internals of UnifiedCache. + */ + inline UBool noHardReferences() const { return getRefCount() == 0; } + + /** + * If hasHardReferences() == true then this object has hard references. + * Must be called only from within the internals of UnifiedCache. + */ + inline UBool hasHardReferences() const { return getRefCount() != 0; } + + /** + * Deletes this object if it has no references. + * Available for non-cached SharedObjects only. Ownership of cached objects + * is with the UnifiedCache, which is solely responsible for eviction and deletion. + */ + void deleteIfZeroRefCount() const; + + + /** + * Returns a writable version of ptr. + * If there is exactly one owner, then ptr itself is returned as a + * non-const pointer. + * If there are multiple owners, then ptr is replaced with a + * copy-constructed clone, + * and that is returned. + * Returns nullptr if cloning failed. + * + * T must be a subclass of SharedObject. + */ + template<typename T> + static T *copyOnWrite(const T *&ptr) { + const T *p = ptr; + if(p->getRefCount() <= 1) { return const_cast<T *>(p); } + T *p2 = new T(*p); + if(p2 == nullptr) { return nullptr; } + p->removeRef(); + ptr = p2; + p2->addRef(); + return p2; + } + + /** + * Makes dest an owner of the object pointed to by src while adjusting + * reference counts and deleting the previous object dest pointed to + * if necessary. Before this call is made, dest must either be nullptr or + * be included in the reference count of the object it points to. + * + * T must be a subclass of SharedObject. + */ + template<typename T> + static void copyPtr(const T *src, const T *&dest) { + if(src != dest) { + if(dest != nullptr) { dest->removeRef(); } + dest = src; + if(src != nullptr) { src->addRef(); } + } + } + + /** + * Equivalent to copyPtr(nullptr, dest). + */ + template<typename T> + static void clearPtr(const T *&ptr) { + if (ptr != nullptr) { + ptr->removeRef(); + ptr = nullptr; + } + } + +private: + /** + * The number of references from the UnifiedCache, which is + * the number of times that the sharedObject is stored as a hash table value. + * For use by UnifiedCache implementation code only. + * All access is synchronized by UnifiedCache's gCacheMutex + */ + mutable int32_t softRefCount; + friend class UnifiedCache; + + /** + * Reference count, excluding references from within the UnifiedCache implementation. + */ + mutable u_atomic_int32_t hardRefCount; + + mutable const UnifiedCacheBase *cachePtr; + +}; + +U_NAMESPACE_END + +#endif |