AP_HAL: utility: Add OwnPtr implementation

This is very similar to std::unique_ptr, but doesn't require including
the <memory> header which pulls lots of c++ headers and cause problems
with nuttx headers. It's header-only. It contains an explanation on what
it solves, how to use and unit tests.

libraries/AP_HAL/utility/OwnPtr.h

@@ -0,0 +1,127 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+ * Copyright (C) 2015-2016  Intel Corporation. All rights reserved.
+ *
+ * This file is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <cstddef>
+
+namespace AP_HAL {
+
+/* Poor's man std::unique_ptr
+ *
+ * OwnPtr is a container for a pointer declaring ownership.
+ *
+ * The goal is to allow to own object, pass it around and automatically delete
+ * the pointer when the container goes out of scope.
+ *
+ * In order to pass it around the move constructor or move assignment operator
+ * must be used. operator*, operator-> and the get() method can be used to get
+ * the pointer contained in the OwnPtr container.
+ *
+ * The OwnPtr name comes from similar class in WebKit, before they switched to
+ * std::unique_ptr. The implementation is different/simpler. We need our own
+ * implementation since the <memory> header (and thus std::unique_ptr) is not
+ * compatible with the PX4 toolchain and/or nuttx headers.
+ */
+template<typename T>
+class OwnPtr {
+public:
+    OwnPtr() : _ptr(nullptr) { }
+    OwnPtr(std::nullptr_t) : _ptr(nullptr) { }
+
+    /* non-copyable */
+    OwnPtr(const OwnPtr<T> &other) = delete;
+
+    /* Allow construction from a derived class U */
+    template<typename U>
+    OwnPtr(OwnPtr<U>&& other) : _ptr(other.leak()) { }
+
+    OwnPtr(T *ptr) : _ptr(ptr) { }
+
+    OwnPtr<T>& operator=(std::nullptr_t) { clear(); return *this; }
+
+    template<typename U>
+    OwnPtr<T>& operator=(OwnPtr<U>&& other)
+    {
+        T *old = _ptr;
+        _ptr = other.leak();
+        delete old;
+        return *this;
+    }
+
+    template<typename U>
+    OwnPtr<T>& operator=(U *other)
+    {
+        T *old = _ptr;
+        _ptr = other;
+        delete old;
+        return *this;
+    }
+
+    ~OwnPtr() { delete _ptr; }
+
+    void clear()
+    {
+        delete leak();
+    }
+
+    T *leak()
+    {
+        T *old = _ptr;
+        _ptr = nullptr;
+        return old;
+    }
+
+    T *get() const
+    {
+        return _ptr;
+    }
+
+    T& operator*() const { return *_ptr; }
+    T *operator->() const { return _ptr; }
+    bool operator !() const { return !_ptr; }
+    explicit operator bool() const { return _ptr != nullptr; }
+
+private:
+    T *_ptr;
+};
+
+template<typename T>
+inline bool operator==(T* a, const OwnPtr<T>& b)
+{
+    return a == b.get();
+}
+
+template<typename T>
+inline bool operator==(const OwnPtr<T>& a, T* b)
+{
+    return a.get() == b;
+}
+
+template<typename T>
+inline bool operator!=(T* a, const OwnPtr<T>& b)
+{
+    return a != b.get();
+}
+
+template<typename T>
+inline bool operator!=(const OwnPtr<T>& a, T* b)
+{
+    return a.get() != b;
+}
+
+}

libraries/AP_HAL/utility/tests/test_own_ptr.cpp

@@ -0,0 +1,199 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+ * Copyright (C) 2015-2016  Intel Corporation. All rights reserved.
+ *
+ * This file is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <AP_gtest.h>
+
+#include <utility>
+#include <AP_HAL/utility/OwnPtr.h>
+
+TEST(OwnPtrTest, SamePointer)
+{
+    int *a = new int{42};
+    AP_HAL::OwnPtr<int> own(a);
+
+    EXPECT_TRUE(own == a);
+    EXPECT_TRUE(a == own);
+
+    EXPECT_FALSE(own != a);
+    EXPECT_FALSE(a != own);
+
+    EXPECT_EQ(a, own.get());
+}
+
+TEST(OwnPtrTest, MoveOwnership)
+{
+    int *a = new int{42};
+    AP_HAL::OwnPtr<int> own(a);
+    AP_HAL::OwnPtr<int> own2 = std::move(own);
+
+    EXPECT_EQ(own2.get(), a);
+    EXPECT_EQ(own.get(), nullptr);
+}
+
+class TestDeleted {
+public:
+    TestDeleted(unsigned int &d) : deleted(d) { }
+    ~TestDeleted() { deleted++; }
+
+    unsigned int &deleted;
+};
+
+TEST(OwnPtrTest, DeleteOutOfScope)
+{
+    unsigned int deleted = 0;
+
+    {
+        AP_HAL::OwnPtr<TestDeleted> own(new TestDeleted{deleted});
+    }
+
+    EXPECT_EQ(deleted, 1);
+}
+
+TEST(OwnPtrTest, DeleteOutOfScopeAfterMove)
+{
+    unsigned int deleted = 0;
+    AP_HAL::OwnPtr<TestDeleted> own;
+
+    {
+        AP_HAL::OwnPtr<TestDeleted> own2(new TestDeleted{deleted});
+        own = std::move(own2);
+    }
+
+    // own2 is now out of scope, but it has been moved already
+    EXPECT_EQ(deleted, 0);
+
+    // now remove also 'own'
+    own.clear();
+
+    EXPECT_EQ(deleted, 1);
+}
+
+class TestCall {
+public:
+    int foo() { return 42; }
+};
+
+TEST(OwnPtrTest, CallMethod)
+{
+    AP_HAL::OwnPtr<TestCall> own(new TestCall{});
+    EXPECT_EQ(own->foo(), 42);
+    EXPECT_EQ((*own).foo(), 42);
+}
+
+class TestDestructor {
+public:
+    TestDestructor(AP_HAL::OwnPtr<TestDeleted> v) : _v(std::move(v)) { }
+
+    AP_HAL::OwnPtr<TestDeleted> _v;
+};
+
+TEST(OwnPtrTest, MoveToConstructor)
+{
+    unsigned int deleted = 0;
+
+    AP_HAL::OwnPtr<TestDeleted> own(new TestDeleted{deleted});
+    {
+        EXPECT_EQ(0, deleted);
+        TestDestructor destructor{std::move(own)};
+        EXPECT_EQ(0, deleted);
+    }
+    EXPECT_EQ(1, deleted);
+}
+
+static AP_HAL::OwnPtr<TestDeleted> create_test_deleted(unsigned int &deleted)
+{
+    return AP_HAL::OwnPtr<TestDeleted>(new TestDeleted(deleted));
+}
+
+TEST(OwnPtrTest, ReturnType)
+{
+    unsigned int deleted = 0;
+
+    auto own = create_test_deleted(deleted);
+    EXPECT_EQ(0, deleted);
+    {
+        auto own2 = create_test_deleted(deleted);
+        EXPECT_EQ(0, deleted);
+    }
+    EXPECT_EQ(1, deleted);
+    own.clear();
+    EXPECT_EQ(2, deleted);
+}
+
+TEST(OwnPtrTest, ReplacePointer)
+{
+    unsigned int deleted1 = 0;
+    unsigned int deleted2 = 0;
+
+    auto own = create_test_deleted(deleted1);
+    EXPECT_EQ(0, deleted1);
+    {
+        own = create_test_deleted(deleted2);
+        EXPECT_EQ(1, deleted1);
+    }
+    EXPECT_EQ(0, deleted2);
+    own = nullptr;
+    EXPECT_EQ(1, deleted2);
+}
+
+TEST(OwnPtrTest, ReplaceWithRawPointer)
+{
+    unsigned int deleted1 = 0;
+
+    auto own = create_test_deleted(deleted1);
+    EXPECT_EQ(0, deleted1);
+    {
+        own = new TestDeleted{deleted1};
+        EXPECT_EQ(1, deleted1);
+    }
+}
+
+TEST(OwnPtrTest, Empty)
+{
+    int *a = new int{42};
+
+    AP_HAL::OwnPtr<int> own1;
+    EXPECT_FALSE(own1);
+
+    own1 = a;
+    EXPECT_TRUE((bool) own1);
+}
+
+class A {
+public:
+    A(int a) : _a(a) { }
+    int _a;
+};
+
+class B : public A {
+public:
+    B() : A(42) { }
+};
+
+TEST(OwnPtrTest, Inheritance)
+{
+    A *a = new A(21);
+    B *b = new B();
+    AP_HAL::OwnPtr<A> own_a(a);
+    AP_HAL::OwnPtr<B> own_b(b);
+
+    own_a = std::move(own_b);
+    EXPECT_EQ(b, own_a.get());
+    EXPECT_EQ(42, own_a->_a);
+}
+
+AP_GTEST_MAIN()

libraries/AP_HAL/utility/tests/wscript

@@ -0,0 +1,7 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+def build(bld):
+    bld.ap_find_tests(
+        use='ap',
+    )