COMMON: Add standard data method to Common::Array

This matches the C++11 std::vector method of the same name, and
replaces usage of taking the address of the first element of an
array by &array[0] or &array.front() or &*array.begin(). The data
method is better than these usages because it can be used even
when the array is empty.

common/array.h

@@ -87,10 +87,10 @@ public:
 	 * Construct an array by copying data from a regular array.
 	 */
 	template<class T2>
-	Array(const T2 *data, size_type n) {
+	Array(const T2 *array, size_type n) {
 		_size = n;
 		allocCapacity(n);
-		uninitialized_copy(data, data + _size, _storage);
+		uninitialized_copy(array, array + _size, _storage);
 	}
 
 	~Array() {
@@ -123,6 +123,16 @@ public:
 		_storage[_size].~T();
 	}
 
+	/** Returns a pointer to the underlying memory serving as element storage. */
+	const T *data() const {
+		return _storage;
+	}
+
+	/** Returns a pointer to the underlying memory serving as element storage. */
+	T *data() {
+		return _storage;
+	}
+
 	/** Returns a reference to the first element of the array. */
 	T &front() {
 		assert(_size > 0);

test/common/array.h

@@ -353,6 +353,15 @@ class ArrayTestSuite : public CxxTest::TestSuite
 		TS_ASSERT_EQUALS(array2.size(), (unsigned int)3);
 	}
 
+	void test_data() {
+		Common::Array<int> array;
+		TS_ASSERT(array.data() == nullptr);
+		array.resize(2);
+		TS_ASSERT(array.data() != nullptr);
+		TS_ASSERT_EQUALS(array.data(), &array.front());
+		TS_ASSERT_EQUALS(array.data() + array.size() - 1, &array.back());
+	}
+
 	void test_front_back_push_pop() {
 		Common::Array<int> container;