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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:22:09 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:22:09 +0000
commit43a97878ce14b72f0981164f87f2e35e14151312 (patch)
tree620249daf56c0258faa40cbdcf9cfba06de2a846 /mfbt/Scoped.h
parentInitial commit. (diff)
downloadfirefox-upstream.tar.xz
firefox-upstream.zip
Adding upstream version 110.0.1.upstream/110.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* DEPRECATED: Use UniquePtr.h instead. */
+
+#ifndef mozilla_Scoped_h
+#define mozilla_Scoped_h
+
+/*
+ * DEPRECATED: Use UniquePtr.h instead.
+ *
+ * Resource Acquisition Is Initialization is a programming idiom used
+ * to write robust code that is able to deallocate resources properly,
+ * even in presence of execution errors or exceptions that need to be
+ * propagated. The Scoped* classes defined via the |SCOPED_TEMPLATE|
+ * and |MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLTE| macros perform the
+ * deallocation of the resource they hold once program execution
+ * reaches the end of the scope for which they have been defined.
+ * These macros have been used to automatically close file
+ * descriptors/file handles when reaching the end of the scope,
+ * graphics contexts, etc.
+ *
+ * The general scenario for RAII classes created by the above macros
+ * is the following:
+ *
+ * ScopedClass foo(create_value());
+ * // ... In this scope, |foo| is defined. Use |foo.get()| or |foo.rwget()|
+ * to access the value.
+ * // ... In case of |return| or |throw|, |foo| is deallocated automatically.
+ * // ... If |foo| needs to be returned or stored, use |foo.forget()|
+ *
+ * Note that the RAII classes defined in this header do _not_ perform any form
+ * of reference-counting or garbage-collection. These classes have exactly two
+ * behaviors:
+ *
+ * - if |forget()| has not been called, the resource is always deallocated at
+ * the end of the scope;
+ * - if |forget()| has been called, any control on the resource is unbound
+ * and the resource is not deallocated by the class.
+ */
+
+#include <utility>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+
+namespace mozilla {
+
+/*
+ * Scoped is a helper to create RAII wrappers
+ * Type argument |Traits| is expected to have the following structure:
+ *
+ * struct Traits
+ * {
+ * // Define the type of the value stored in the wrapper
+ * typedef value_type type;
+ * // Returns the value corresponding to the uninitialized or freed state
+ * const static type empty();
+ * // Release resources corresponding to the wrapped value
+ * // This function is responsible for not releasing an |empty| value
+ * const static void release(type);
+ * }
+ */
+template <typename Traits>
+class MOZ_NON_TEMPORARY_CLASS Scoped {
+ public:
+ typedef typename Traits::type Resource;
+
+ explicit Scoped() : mValue(Traits::empty()) {}
+
+ explicit Scoped(const Resource& aValue) : mValue(aValue) {}
+
+ /* Move constructor. */
+ Scoped(Scoped&& aOther) : mValue(std::move(aOther.mValue)) {
+ aOther.mValue = Traits::empty();
+ }
+
+ ~Scoped() { Traits::release(mValue); }
+
+ // Constant getter
+ operator const Resource&() const { return mValue; }
+ const Resource& operator->() const { return mValue; }
+ const Resource& get() const { return mValue; }
+ // Non-constant getter.
+ Resource& rwget() { return mValue; }
+
+ /*
+ * Forget the resource.
+ *
+ * Once |forget| has been called, the |Scoped| is neutralized, i.e. it will
+ * have no effect at destruction (unless it is reset to another resource by
+ * |operator=|).
+ *
+ * @return The original resource.
+ */
+ Resource forget() {
+ Resource tmp = mValue;
+ mValue = Traits::empty();
+ return tmp;
+ }
+
+ /*
+ * Perform immediate clean-up of this |Scoped|.
+ *
+ * If this |Scoped| is currently empty, this method has no effect.
+ */
+ void dispose() {
+ Traits::release(mValue);
+ mValue = Traits::empty();
+ }
+
+ bool operator==(const Resource& aOther) const { return mValue == aOther; }
+
+ /*
+ * Replace the resource with another resource.
+ *
+ * Calling |operator=| has the side-effect of triggering clean-up. If you do
+ * not want to trigger clean-up, you should first invoke |forget|.
+ *
+ * @return this
+ */
+ Scoped& operator=(const Resource& aOther) { return reset(aOther); }
+
+ Scoped& reset(const Resource& aOther) {
+ Traits::release(mValue);
+ mValue = aOther;
+ return *this;
+ }
+
+ /* Move assignment operator. */
+ Scoped& operator=(Scoped&& aRhs) {
+ MOZ_ASSERT(&aRhs != this, "self-move-assignment not allowed");
+ this->~Scoped();
+ new (this) Scoped(std::move(aRhs));
+ return *this;
+ }
+
+ private:
+ explicit Scoped(const Scoped& aValue) = delete;
+ Scoped& operator=(const Scoped& aValue) = delete;
+
+ private:
+ Resource mValue;
+};
+
+/*
+ * SCOPED_TEMPLATE defines a templated class derived from Scoped
+ * This allows to implement templates such as ScopedFreePtr.
+ *
+ * @param name The name of the class to define.
+ * @param Traits A struct implementing clean-up. See the implementations
+ * for more details.
+ */
+#define SCOPED_TEMPLATE(name, Traits) \
+ template <typename Type> \
+ struct MOZ_NON_TEMPORARY_CLASS name \
+ : public mozilla::Scoped<Traits<Type> > { \
+ typedef mozilla::Scoped<Traits<Type> > Super; \
+ typedef typename Super::Resource Resource; \
+ name& operator=(Resource aRhs) { \
+ Super::operator=(aRhs); \
+ return *this; \
+ } \
+ name& operator=(name&& aRhs) = default; \
+ \
+ explicit name() : Super() {} \
+ explicit name(Resource aRhs) : Super(aRhs) {} \
+ name(name&& aRhs) : Super(std::move(aRhs)) {} \
+ \
+ private: \
+ explicit name(const name&) = delete; \
+ name& operator=(const name&) = delete; \
+ };
+
+/*
+ * MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE makes it easy to create scoped
+ * pointers for types with custom deleters; just overload
+ * TypeSpecificDelete(T*) in the same namespace as T to call the deleter for
+ * type T.
+ *
+ * @param name The name of the class to define.
+ * @param Type A struct implementing clean-up. See the implementations
+ * for more details.
+ * *param Deleter The function that is used to delete/destroy/free a
+ * non-null value of Type*.
+ *
+ * Example:
+ *
+ * MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedPRFileDesc, PRFileDesc, \
+ * PR_Close)
+ * ...
+ * {
+ * ScopedPRFileDesc file(PR_OpenFile(...));
+ * ...
+ * } // file is closed with PR_Close here
+ */
+#define MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(name, Type, Deleter) \
+ template <> \
+ inline void TypeSpecificDelete(Type* aValue) { \
+ Deleter(aValue); \
+ } \
+ typedef ::mozilla::TypeSpecificScopedPointer<Type> name;
+
+template <typename T>
+void TypeSpecificDelete(T* aValue);
+
+template <typename T>
+struct TypeSpecificScopedPointerTraits {
+ typedef T* type;
+ static type empty() { return nullptr; }
+ static void release(type aValue) {
+ if (aValue) {
+ TypeSpecificDelete(aValue);
+ }
+ }
+};
+
+SCOPED_TEMPLATE(TypeSpecificScopedPointer, TypeSpecificScopedPointerTraits)
+
+} /* namespace mozilla */
+
+#endif /* mozilla_Scoped_h */