util/AllocatedString: new utility class

Makefile.am

@@ -378,6 +378,7 @@ libutil_a_SOURCES = \
 	src/util/CharUtil.hxx \
 	src/util/NumberParser.hxx \
 	src/util/StringPointer.hxx \
+	src/util/AllocatedString.hxx \
 	src/util/StringUtil.cxx src/util/StringUtil.hxx \
 	src/util/WStringUtil.cxx src/util/WStringUtil.hxx \
 	src/util/StringAPI.hxx \

src/util/AllocatedString.hxx

@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2015 Max Kellermann <max@duempel.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ALLOCATED_STRING_HXX
+#define ALLOCATED_STRING_HXX
+
+#include "StringPointer.hxx"
+
+#include <utility>
+
+/**
+ * A string pointer whose memory is managed by this class.
+ *
+ * Unlike std::string, this object can hold a "nullptr" special value.
+ */
+template<typename T=char>
+class AllocatedString {
+public:
+	typedef typename StringPointer<T>::value_type value_type;
+	typedef typename StringPointer<T>::pointer pointer;
+	typedef typename StringPointer<T>::const_pointer const_pointer;
+
+private:
+	pointer value;
+
+	explicit AllocatedString(pointer _value)
+		:value(_value) {}
+
+public:
+	AllocatedString(std::nullptr_t n):value(n) {}
+
+	AllocatedString(AllocatedString &&src)
+		:value(src.Steal()) {}
+
+	~AllocatedString() {
+		delete[] value;
+	}
+
+	static AllocatedString Donate(pointer value) {
+		return AllocatedString(value);
+	}
+
+	static AllocatedString Null() {
+		return nullptr;
+	}
+
+	static AllocatedString Empty() {
+		auto p = new value_type[1];
+		p[0] = value_type(0);
+		return Donate(p);
+	}
+
+	AllocatedString &operator=(AllocatedString &&src) {
+		*(StringPointer<T> *)this = std::move(src);
+		std::swap(value, src.value);
+		return *this;
+	}
+
+	constexpr bool IsNull() const {
+		return value == nullptr;
+	}
+
+	constexpr const_pointer c_str() const {
+		return value;
+	}
+
+	pointer Steal() {
+		pointer result = value;
+		value = nullptr;
+		return result;
+	}
+};
+
+#endif