Add UniquePtr.h to frameworks/native

/*

 * Copyright (C) 2010 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

/* === NOTE === NOTE === NOTE === NOTE === NOTE === NOTE === NOTE === NOTE ===

 *

 * THIS IS A COPY OF libcore/include/UniquePtr.h AND AS SUCH THAT IS THE

 * CANONICAL SOURCE OF THIS FILE. PLEASE KEEP THEM IN SYNC.

 *

 * === NOTE === NOTE === NOTE === NOTE === NOTE === NOTE === NOTE === NOTE ===

 */

#ifndef UNIQUE_PTR_H_included

#define UNIQUE_PTR_H_included

#include <cstdlib> // For NULL.

// Default deleter for pointer types.

template <typename T>

struct DefaultDelete {

    enum { type_must_be_complete = sizeof(T) };

    DefaultDelete() {}

    void operator()(T* p) const {

        delete p;

    }

};

// Default deleter for array types.

template <typename T>

struct DefaultDelete<T[]> {

    enum { type_must_be_complete = sizeof(T) };

    void operator()(T* p) const {

        delete[] p;

    }

};

// A smart pointer that deletes the given pointer on destruction.

// Equivalent to C++0x's std::unique_ptr (a combination of boost::scoped_ptr

// and boost::scoped_array).

// Named to be in keeping with Android style but also to avoid

// collision with any other implementation, until we can switch over

// to unique_ptr.

// Use thus:

//   UniquePtr<C> c(new C);

template <typename T, typename D = DefaultDelete<T> >

class UniquePtr {

public:

    // Construct a new UniquePtr, taking ownership of the given raw pointer.

    explicit UniquePtr(T* ptr = NULL) : mPtr(ptr) {

    }

    ~UniquePtr() {

        reset();

    }

    // Accessors.

    T& operator*() const { return *mPtr; }

    T* operator->() const { return mPtr; }

    T* get() const { return mPtr; }

    // Returns the raw pointer and hands over ownership to the caller.

    // The pointer will not be deleted by UniquePtr.

    T* release() __attribute__((warn_unused_result)) {

        T* result = mPtr;

        mPtr = NULL;

        return result;

    }

    // Takes ownership of the given raw pointer.

    // If this smart pointer previously owned a different raw pointer, that

    // raw pointer will be freed.

    void reset(T* ptr = NULL) {

        if (ptr != mPtr) {

            D()(mPtr);

            mPtr = ptr;

        }

    }

private:

    // The raw pointer.

    T* mPtr;

    // Comparing unique pointers is probably a mistake, since they're unique.

    template <typename T2> bool operator==(const UniquePtr<T2>& p) const;

    template <typename T2> bool operator!=(const UniquePtr<T2>& p) const;

    // Disallow copy and assignment.

    UniquePtr(const UniquePtr&);

    void operator=(const UniquePtr&);

};

// Partial specialization for array types. Like std::unique_ptr, this removes

// operator* and operator-> but adds operator[].

template <typename T, typename D>

class UniquePtr<T[], D> {

public:

    explicit UniquePtr(T* ptr = NULL) : mPtr(ptr) {

    }

    ~UniquePtr() {

        reset();

    }

    T& operator[](size_t i) const {

        return mPtr[i];

    }

    T* get() const { return mPtr; }

    T* release() __attribute__((warn_unused_result)) {

        T* result = mPtr;

        mPtr = NULL;

        return result;

    }

    void reset(T* ptr = NULL) {

        if (ptr != mPtr) {

            D()(mPtr);

            mPtr = ptr;

        }

    }

private:

    T* mPtr;

    // Disallow copy and assignment.

    UniquePtr(const UniquePtr&);

    void operator=(const UniquePtr&);

};

#if UNIQUE_PTR_TESTS

// Run these tests with:

// g++ -g -DUNIQUE_PTR_TESTS -x c++ UniquePtr.h && ./a.out

#include <stdio.h>

static void assert(bool b) {

    if (!b) {

        fprintf(stderr, "FAIL\n");

        abort();

    }

    fprintf(stderr, "OK\n");

}

static int cCount = 0;

struct C {

    C() { ++cCount; }

    ~C() { --cCount; }

};

static bool freed = false;

struct Freer {

    void operator()(int* p) {

        assert(*p == 123);

        free(p);

        freed = true;

    }

};

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

    //

    // UniquePtr<T> tests...

    //

    // Can we free a single object?

    {

        UniquePtr<C> c(new C);

        assert(cCount == 1);

    }

    assert(cCount == 0);

    // Does release work?

    C* rawC;

    {

        UniquePtr<C> c(new C);

        assert(cCount == 1);

        rawC = c.release();

    }

    assert(cCount == 1);

    delete rawC;

    // Does reset work?

    {

        UniquePtr<C> c(new C);

        assert(cCount == 1);

        c.reset(new C);

        assert(cCount == 1);

    }

    assert(cCount == 0);

    //

    // UniquePtr<T[]> tests...

    //

    // Can we free an array?

    {

        UniquePtr<C[]> cs(new C[4]);

        assert(cCount == 4);

    }

    assert(cCount == 0);

    // Does release work?

    {

        UniquePtr<C[]> c(new C[4]);

        assert(cCount == 4);

        rawC = c.release();

    }

    assert(cCount == 4);

    delete[] rawC;

    // Does reset work?

    {

        UniquePtr<C[]> c(new C[4]);

        assert(cCount == 4);

        c.reset(new C[2]);

        assert(cCount == 2);

    }

    assert(cCount == 0);

    //

    // Custom deleter tests...

    //

    assert(!freed);

    {

        UniquePtr<int, Freer> i(reinterpret_cast<int*>(malloc(sizeof(int))));

        *i = 123;

    }

    assert(freed);

    return 0;

}

#endif

#endif  // UNIQUE_PTR_H_included