CAAutoDisposer.h

/*  Copyright © 2007 Apple Inc. All Rights Reserved.
    
    Disclaimer: IMPORTANT:  This Apple software is supplied to you by 
            Apple Inc. ("Apple") in consideration of your agreement to the
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            install, modify or redistribute this Apple software.
            
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            subject to these terms, Apple grants you a personal, non-exclusive
            license, under Apple's copyrights in this original Apple software (the
            "Apple Software"), to use, reproduce, modify and redistribute the Apple
            Software, with or without modifications, in source and/or binary forms;
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            may be used to endorse or promote products derived from the Apple
            Software without specific prior written permission from Apple.  Except
            as expressly stated in this notice, no other rights or licenses, express
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            The Apple Software is provided by Apple on an "AS IS" basis.  APPLE
            MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
            THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS
            FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND
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*/
#if !defined(__CAPtr_h__)
#define __CAPtr_h__

#include <stdlib.h>     // for malloc
#include <new>          // for bad_alloc
#include <string.h>     // for memset

inline void* CA_malloc(size_t size)
{
    void* p = malloc(size);
    if (!p && size) throw std::bad_alloc();
    return p;
}

inline void* CA_realloc(void* old, size_t size)
{
#if TARGET_OS_WIN32
    void* p = realloc(old, size);
#else
    void* p = reallocf(old, size); // reallocf ensures the old pointer is freed if memory is full (p is NULL).
#endif
    if (!p && size) throw std::bad_alloc();
    return p;
}

#ifndef UINTPTR_MAX
#if __LP64__
#define UINTPTR_MAX   18446744073709551615ULL
#else
#define UINTPTR_MAX   4294967295U
#endif
#endif

inline void* CA_calloc(size_t n, size_t size)
{   
    // ensure that multiplication will not overflow
    if (n && UINTPTR_MAX / n < size) throw std::bad_alloc();
    
    size_t nsize = n*size;
    void* p = malloc(nsize);
    if (!p && nsize) throw std::bad_alloc();

    memset(p, 0, nsize);
    return p;
}


// helper class for automatic conversions
template <typename T>
struct CAPtrRef
{
    T* ptr_;

    explicit CAPtrRef(T* ptr) : ptr_(ptr) {}
};

template <typename T>
class CAAutoFree
{
private:
    T* ptr_;

public:
    
    CAAutoFree() : ptr_(0) {}
    
    explicit CAAutoFree(T* ptr) : ptr_(ptr) {}
    
    template<typename U>
    CAAutoFree(CAAutoFree<U>& that) : ptr_(that.release()) {} // take ownership

    // C++ std says: a template constructor is never a copy constructor
    CAAutoFree(CAAutoFree<T>& that) : ptr_(that.release()) {} // take ownership

    CAAutoFree(size_t n, bool clear = false) 
        // this becomes an ambiguous call if n == 0
        : ptr_(0) 
        {
            size_t maxItems = ~size_t(0) / sizeof(T);
            if (n > maxItems) 
                throw std::bad_alloc();

            ptr_ = static_cast<T*>(clear ? CA_calloc(n, sizeof(T)) : CA_malloc(n * sizeof(T)));
        }
    
    ~CAAutoFree() { free(); }
    
    void alloc(size_t numItems, bool clear = false) 
    {
        size_t maxItems = ~size_t(0) / sizeof(T);
        if (numItems > maxItems) throw std::bad_alloc();
        
        free();
        ptr_ = static_cast<T*>(clear ? CA_calloc(numItems, sizeof(T)) : CA_malloc(numItems * sizeof(T)));
    }
    
    void allocBytes(size_t numBytes, bool clear = false) 
    {
        free();
        ptr_ = static_cast<T*>(clear ? CA_calloc(1, numBytes) : CA_malloc(numBytes));
    }
    
    void reallocBytes(size_t numBytes) 
    {
        ptr_ = static_cast<T*>(CA_realloc(ptr_, numBytes));
    }

    void reallocItems(size_t numItems) 
    {
        size_t maxItems = ~size_t(0) / sizeof(T);
        if (numItems > maxItems) throw std::bad_alloc();
        
        ptr_ = static_cast<T*>(CA_realloc(ptr_, numItems * sizeof(T)));
    }
    
    template <typename U>
    CAAutoFree& operator=(CAAutoFree<U>& that) 
    { 
        set(that.release());    // take ownership
        return *this;
    }
    
    CAAutoFree& operator=(CAAutoFree& that) 
    { 
        set(that.release());    // take ownership
        return *this;
    }
    
    CAAutoFree& operator=(T* ptr) 
    {
        set(ptr); 
        return *this;
    }
    
    template <typename U>
    CAAutoFree& operator=(U* ptr) 
    {
        set(ptr); 
        return *this;
    }
        
    T& operator*() const { return *ptr_; }
    T* operator->() const { return ptr_; }
    
    T* operator()() const { return ptr_; }
    T* get() const { return ptr_; }
    operator T*() const { return ptr_; }

    bool operator==(CAAutoFree const& that) const { return ptr_ == that.ptr_; }
    bool operator!=(CAAutoFree const& that) const { return ptr_ != that.ptr_; }
    bool operator==(T* ptr) const { return ptr_ == ptr; }
    bool operator!=(T* ptr) const { return ptr_ != ptr; }
        
    T* release() 
    {
        // release ownership
        T* result = ptr_;
        ptr_ = 0;
        return result;
    }
    
    void set(T* ptr)
    {
        if (ptr != ptr_)
        {
            ::free(ptr_);
            ptr_ = ptr;
        }
    }
    
    void free() 
    {
        set(0);
    }


    // automatic conversions to allow assignment from results of functions.
    // hard to explain. see auto_ptr implementation and/or Josuttis' STL book.
    CAAutoFree(CAPtrRef<T> ref) : ptr_(ref.ptr_) { }

    CAAutoFree& operator=(CAPtrRef<T> ref)
    {
        set(ref.ptr_);
        return *this;
    }

    template<typename U>
    operator CAPtrRef<U>()
        { return CAPtrRef<U>(release()); }

    template<typename U>
    operator CAAutoFree<U>()
        { return CAAutoFree<U>(release()); }
    
};


template <typename T>
class CAAutoDelete
{
private:
    T* ptr_;

public:
    CAAutoDelete() : ptr_(0) {}

    explicit CAAutoDelete(T* ptr) : ptr_(ptr) {}
    
    template<typename U>
    CAAutoDelete(CAAutoDelete<U>& that) : ptr_(that.release()) {} // take ownership

    // C++ std says: a template constructor is never a copy constructor
    CAAutoDelete(CAAutoDelete<T>& that) : ptr_(that.release()) {} // take ownership
    
    ~CAAutoDelete() { free(); }
    
    template <typename U>
    CAAutoDelete& operator=(CAAutoDelete<U>& that) 
    { 
        set(that.release());    // take ownership
        return *this;
    }
    
    CAAutoDelete& operator=(CAAutoDelete& that) 
    { 
        set(that.release());    // take ownership
        return *this;
    }
    
    CAAutoDelete& operator=(T* ptr) 
    {
        set(ptr); 
        return *this;
    }
    
    template <typename U>
    CAAutoDelete& operator=(U* ptr) 
    {
        set(ptr); 
        return *this;
    }
        
    T& operator*() const { return *ptr_; }
    T* operator->() const { return ptr_; }
    
    T* operator()() const { return ptr_; }
    T* get() const { return ptr_; }
    operator T*() const { return ptr_; }
    
    bool operator==(CAAutoDelete const& that) const { return ptr_ == that.ptr_; }
    bool operator!=(CAAutoDelete const& that) const { return ptr_ != that.ptr_; }
    bool operator==(T* ptr) const { return ptr_ == ptr; }
    bool operator!=(T* ptr) const { return ptr_ != ptr; }
        
    T* release() 
    {
        // release ownership
        T* result = ptr_;
        ptr_ = 0;
        return result;
    }
    
    void set(T* ptr)
    {
        if (ptr != ptr_)
        {
            delete ptr_;
            ptr_ = ptr;
        }
    }
    
    void free() 
    {
        set(0);
    }


    // automatic conversions to allow assignment from results of functions.
    // hard to explain. see auto_ptr implementation and/or Josuttis' STL book.
    CAAutoDelete(CAPtrRef<T> ref) : ptr_(ref.ptr_) { }

    CAAutoDelete& operator=(CAPtrRef<T> ref)
    {
        set(ref.ptr_);
        return *this;
    }

    template<typename U>
    operator CAPtrRef<U>()
        { return CAPtrRef<U>(release()); }

    template<typename U>
    operator CAAutoFree<U>()
        { return CAAutoFree<U>(release()); }
    
};


template <typename T>
class CAAutoArrayDelete
{
private:
    T* ptr_;

public:
    CAAutoArrayDelete() : ptr_(0) {}

    explicit CAAutoArrayDelete(T* ptr) : ptr_(ptr) {}
    
    template<typename U>
    CAAutoArrayDelete(CAAutoArrayDelete<U>& that) : ptr_(that.release()) {} // take ownership

    // C++ std says: a template constructor is never a copy constructor
    CAAutoArrayDelete(CAAutoArrayDelete<T>& that) : ptr_(that.release()) {} // take ownership
    
    // this becomes an ambiguous call if n == 0
    CAAutoArrayDelete(size_t n) : ptr_(new T[n]) {}
    
    ~CAAutoArrayDelete() { free(); }
    
    void alloc(size_t numItems) 
    {
        free();
        ptr_ = new T [numItems];
    }
    
    template <typename U>
    CAAutoArrayDelete& operator=(CAAutoArrayDelete<U>& that) 
    { 
        set(that.release());    // take ownership
        return *this;
    }
    
    CAAutoArrayDelete& operator=(CAAutoArrayDelete& that) 
    { 
        set(that.release());    // take ownership
        return *this;
    }
    
    CAAutoArrayDelete& operator=(T* ptr) 
    {
        set(ptr); 
        return *this;
    }
    
    template <typename U>
    CAAutoArrayDelete& operator=(U* ptr) 
    {
        set(ptr); 
        return *this;
    }
        
    T& operator*() const { return *ptr_; }
    T* operator->() const { return ptr_; }
    
    T* operator()() const { return ptr_; }
    T* get() const { return ptr_; }
    operator T*() const { return ptr_; }

    bool operator==(CAAutoArrayDelete const& that) const { return ptr_ == that.ptr_; }
    bool operator!=(CAAutoArrayDelete const& that) const { return ptr_ != that.ptr_; }
    bool operator==(T* ptr) const { return ptr_ == ptr; }
    bool operator!=(T* ptr) const { return ptr_ != ptr; }
        
    T* release() 
    {
        // release ownership
        T* result = ptr_;
        ptr_ = 0;
        return result;
    }
    
    void set(T* ptr)
    {
        if (ptr != ptr_)
        {
            delete [] ptr_;
            ptr_ = ptr;
        }
    }
    
    void free() 
    {
        set(0);
    }


    // automatic conversions to allow assignment from results of functions.
    // hard to explain. see auto_ptr implementation and/or Josuttis' STL book.
    CAAutoArrayDelete(CAPtrRef<T> ref) : ptr_(ref.ptr_) { }

    CAAutoArrayDelete& operator=(CAPtrRef<T> ref)
    {
        set(ref.ptr_);
        return *this;
    }

    template<typename U>
    operator CAPtrRef<U>()
        { return CAPtrRef<U>(release()); }

    template<typename U>
    operator CAAutoArrayDelete<U>()
        { return CAAutoFree<U>(release()); }
    
};





// convenience function
template <typename T>
void free(CAAutoFree<T>& p)
{
    p.free();
}

////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////

#if 0
// example program showing ownership transfer

CAAutoFree<char> source()
{
    // source allocates and returns ownership to the caller.
    const char* str = "this is a test";
    size_t size = strlen(str) + 1;
    CAAutoFree<char> captr(size, false);
    strlcpy(captr(), str, size);
    printf("source %08X %08X '%s'\n", &captr, captr(), captr());
    return captr;
}

void user(CAAutoFree<char> const& captr)
{
    // passed by const reference. user can access the pointer but does not take ownership.
    printf("user: %08X %08X '%s'\n", &captr, captr(), captr());
}

void sink(CAAutoFree<char> captr)
{
    // passed by value. sink takes ownership and frees the pointer on return.
    printf("sink: %08X %08X '%s'\n", &captr, captr(), captr());
}


int main (int argc, char * const argv[]) 
{

    CAAutoFree<char> captr(source());
    printf("main captr A %08X %08X\n", &captr, captr());
    user(captr);
    sink(captr);
    printf("main captr B %08X %08X\n", &captr, captr());
    return 0;
}
#endif

#endif