Add a general-purpose scoped pointer for libcore JNI.

This is a functional equivalent of C++0x's std::unique_ptr.

(I'm not planning to use this in froyo, but I want it there in case I have to
backport changes from dalvik-dev.)

1 files changed, 231 insertions, 0 deletions

diff --git a/include/UniquePtr.h b/include/UniquePtr.h
new file mode 100644
index 0000000..f5c7c2c
--- /dev/null
+++ b/include/UniquePtr.h
@@ -0,0 +1,231 @@
+/*
+ * 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.
+ */
+
+#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() {
+        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() {
+        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