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localpointer.h
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executable file
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/*
*******************************************************************************
*
* 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__ */