Check in the pristine copy of ICU 4.6...

icu46/source/common/unicode/localpointer.h

+/*
+*******************************************************************************
+*
+*   Copyright (C) 2009-2010, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  localpointer.h
+*   encoding:   US-ASCII
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2009nov13
+*   created by: Markus W. Scherer
+*/
+
+#ifndef __LOCALPOINTER_H__
+#define __LOCALPOINTER_H__
+
+/**
+ * \file 
+ * \brief C++ API: "Smart pointers" for use with and in ICU4C C++ code.
+ *
+ * These classes are inspired by
+ * - std::auto_ptr
+ * - boost::scoped_ptr & boost::scoped_array
+ * - Taligent Safe Pointers (TOnlyPointerTo)
+ *
+ * but none of those provide for all of the goals for ICU smart pointers:
+ * - Smart pointer owns the object and releases it when it goes out of scope.
+ * - No transfer of ownership via copy/assignment to reduce misuse. Simpler & more robust.
+ * - ICU-compatible: No exceptions.
+ * - Need to be able to orphan/release the pointer and its ownership.
+ * - Need variants for normal C++ object pointers, C++ arrays, and ICU C service objects.
+ *
+ * For details see http://site.icu-project.org/design/cpp/scoped_ptr
+ */
+
+#include "unicode/utypes.h"
+
+#if U_SHOW_CPLUSPLUS_API
+
+U_NAMESPACE_BEGIN
+
+/**
+ * "Smart pointer" base class; do not use directly: use LocalPointer etc.
+ *
+ * Base class for smart pointer classes that do not throw exceptions.
+ *
+ * Do not use this base class directly, since it does not delete its pointer.
+ * A subclass must implement methods that delete the pointer:
+ * Destructor and adoptInstead().
+ *
+ * There is no operator T *() provided because the programmer must decide
+ * whether to use getAlias() (without transfer of ownership) or orpan()
+ * (with transfer of ownership and NULLing of the pointer).
+ *
+ * @see LocalPointer
+ * @see LocalArray
+ * @see U_DEFINE_LOCAL_OPEN_POINTER
+ * @stable ICU 4.4
+ */
+template<typename T>
+class LocalPointerBase {
+public:
+    /**
+     * Constructor takes ownership.
+     * @param p simple pointer to an object that is adopted
+     * @stable ICU 4.4
+     */
+    explicit LocalPointerBase(T *p=NULL) : ptr(p) {}
+    /**
+     * Destructor deletes the object it owns.
+     * Subclass must override: Base class does nothing.
+     * @stable ICU 4.4
+     */
+    ~LocalPointerBase() { /* delete ptr; */ }
+    /**
+     * NULL check.
+     * @return TRUE if ==NULL
+     * @stable ICU 4.4
+     */
+    UBool isNull() const { return ptr==NULL; }
+    /**
+     * NULL check.
+     * @return TRUE if !=NULL
+     * @stable ICU 4.4
+     */
+    UBool isValid() const { return ptr!=NULL; }
+    /**
+     * Comparison with a simple pointer, so that existing code
+     * with ==NULL need not be changed.
+     * @param other simple pointer for comparison
+     * @return true if this pointer value equals other
+     * @stable ICU 4.4
+     */
+    bool operator==(const T *other) const { return ptr==other; }
+    /**
+     * Comparison with a simple pointer, so that existing code
+     * with !=NULL need not be changed.
+     * @param other simple pointer for comparison
+     * @return true if this pointer value differs from other
+     * @stable ICU 4.4
+     */
+    bool operator!=(const T *other) const { return ptr!=other; }
+    /**
+     * Access without ownership change.
+     * @return the pointer value
+     * @stable ICU 4.4
+     */
+    T *getAlias() const { return ptr; }
+    /**
+     * Access without ownership change.
+     * @return the pointer value as a reference
+     * @stable ICU 4.4
+     */
+    T &operator*() const { return *ptr; }
+    /**
+     * Access without ownership change.
+     * @return the pointer value
+     * @stable ICU 4.4
+     */
+    T *operator->() const { return ptr; }
+    /**
+     * Gives up ownership; the internal pointer becomes NULL.
+     * @return the pointer value;
+     *         caller becomes responsible for deleting the object
+     * @stable ICU 4.4
+     */
+    T *orphan() {
+        T *p=ptr;
+        ptr=NULL;
+        return p;
+    }
+    /**
+     * Deletes the object it owns,
+     * and adopts (takes ownership of) the one passed in.
+     * Subclass must override: Base class does not delete the object.
+     * @param p simple pointer to an object that is adopted
+     * @stable ICU 4.4
+     */
+    void adoptInstead(T *p) {
+        // delete ptr;
+        ptr=p;
+    }
+protected:
+    T *ptr;
+private:
+    // No comparison operators with other LocalPointerBases.
+    bool operator==(const LocalPointerBase &other);
+    bool operator!=(const LocalPointerBase &other);
+    // No ownership transfer: No copy constructor, no assignment operator.
+    LocalPointerBase(const LocalPointerBase &other);
+    void operator=(const LocalPointerBase &other);
+    // No heap allocation. Use only on the stack.
+    static void * U_EXPORT2 operator new(size_t size);
+    static void * U_EXPORT2 operator new[](size_t size);
+#if U_HAVE_PLACEMENT_NEW
+    static void * U_EXPORT2 operator new(size_t, void *ptr);
+#endif
+};
+
+/**
+ * "Smart pointer" class, deletes objects via the standard C++ delete operator.
+ * For most methods see the LocalPointerBase base class.
+ *
+ * Usage example:
+ * \code
+ * LocalPointer<UnicodeString> s(new UnicodeString((UChar32)0x50005));
+ * int32_t length=s->length();  // 2
+ * UChar lead=s->charAt(0);  // 0xd900
+ * if(some condition) { return; }  // no need to explicitly delete the pointer
+ * s.adoptInstead(new UnicodeString((UChar)0xfffc));
+ * length=s->length();  // 1
+ * // no need to explicitly delete the pointer
+ * \endcode
+ *
+ * @see LocalPointerBase
+ * @stable ICU 4.4
+ */
+template<typename T>
+class LocalPointer : public LocalPointerBase<T> {
+public:
+    /**
+     * Constructor takes ownership.
+     * @param p simple pointer to an object that is adopted
+     * @stable ICU 4.4
+     */
+    explicit LocalPointer(T *p=NULL) : LocalPointerBase<T>(p) {}
+    /**
+     * Destructor deletes the object it owns.
+     * @stable ICU 4.4
+     */
+    ~LocalPointer() {
+        delete LocalPointerBase<T>::ptr;
+    }
+    /**
+     * Deletes the object it owns,
+     * and adopts (takes ownership of) the one passed in.
+     * @param p simple pointer to an object that is adopted
+     * @stable ICU 4.4
+     */
+    void adoptInstead(T *p) {
+        delete LocalPointerBase<T>::ptr;
+        LocalPointerBase<T>::ptr=p;
+    }
+};
+
+/**
+ * "Smart pointer" class, deletes objects via the C++ array delete[] operator.
+ * For most methods see the LocalPointerBase base class.
+ * Adds operator[] for array item access.
+ *
+ * Usage example:
+ * \code
+ * LocalArray<UnicodeString> a(new UnicodeString[2]);
+ * a[0].append((UChar)0x61);
+ * if(some condition) { return; }  // no need to explicitly delete the array
+ * a.adoptInstead(new UnicodeString[4]);
+ * a[3].append((UChar)0x62).append((UChar)0x63).reverse();
+ * // no need to explicitly delete the array
+ * \endcode
+ *
+ * @see LocalPointerBase
+ * @stable ICU 4.4
+ */
+template<typename T>
+class LocalArray : public LocalPointerBase<T> {
+public:
+    /**
+     * Constructor takes ownership.
+     * @param p simple pointer to an array of T objects that is adopted
+     * @stable ICU 4.4
+     */
+    explicit LocalArray(T *p=NULL) : LocalPointerBase<T>(p) {}
+    /**
+     * Destructor deletes the array it owns.
+     * @stable ICU 4.4
+     */
+    ~LocalArray() {
+        delete[] LocalPointerBase<T>::ptr;
+    }
+    /**
+     * Deletes the array it owns,
+     * and adopts (takes ownership of) the one passed in.
+     * @param p simple pointer to an array of T objects that is adopted
+     * @stable ICU 4.4
+     */
+    void adoptInstead(T *p) {
+        delete[] LocalPointerBase<T>::ptr;
+        LocalPointerBase<T>::ptr=p;
+    }
+    /**
+     * Array item access (writable).
+     * No index bounds check.
+     * @param i array index
+     * @return reference to the array item
+     * @stable ICU 4.4
+     */
+    T &operator[](ptrdiff_t i) const { return LocalPointerBase<T>::ptr[i]; }
+};
+
+/**
+ * \def U_DEFINE_LOCAL_OPEN_POINTER
+ * "Smart pointer" definition macro, deletes objects via the closeFunction.
+ * Defines a subclass of LocalPointerBase which works just
+ * like LocalPointer<Type> except that this subclass will use the closeFunction
+ * rather than the C++ delete operator.
+ *
+ * Requirement: The closeFunction must tolerate a NULL pointer.
+ * (We could add a NULL check here but it is normally redundant.)
+ *
+ * Usage example:
+ * \code
+ * LocalUCaseMapPointer csm(ucasemap_open(localeID, options, &errorCode));
+ * utf8OutLength=ucasemap_utf8ToLower(csm.getAlias(),
+ *     utf8Out, (int32_t)sizeof(utf8Out),
+ *     utf8In, utf8InLength, &errorCode);
+ * if(U_FAILURE(errorCode)) { return; }  // no need to explicitly delete the UCaseMap
+ * \endcode
+ *
+ * @see LocalPointerBase
+ * @see LocalPointer
+ * @stable ICU 4.4
+ */
+#define U_DEFINE_LOCAL_OPEN_POINTER(LocalPointerClassName, Type, closeFunction) \
+    class LocalPointerClassName : public LocalPointerBase<Type> { \
+    public: \
+        explicit LocalPointerClassName(Type *p=NULL) : LocalPointerBase<Type>(p) {} \
+        ~LocalPointerClassName() { closeFunction(ptr); } \
+        void adoptInstead(Type *p) { \
+            closeFunction(ptr); \
+            ptr=p; \
+        } \
+    }
+
+U_NAMESPACE_END
+
+#endif  /* U_SHOW_CPLUSPLUS_API */
+#endif  /* __LOCALPOINTER_H__ */