util/AllocatedArray: new utility class

Makefile.am

@@ -396,6 +396,7 @@ libutil_a_SOURCES = \
 	src/util/Clamp.hxx \
 	src/util/DeleteDisposer.hxx \
 	src/util/Alloc.cxx src/util/Alloc.hxx \
+	src/util/AllocatedArray.hxx \
 	src/util/VarSize.hxx \
 	src/util/ScopeExit.hxx \
 	src/util/Error.cxx src/util/Error.hxx \

src/util/AllocatedArray.hxx

+/*
+ * Copyright (C) 2010-2016 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_ARRAY_HXX
+#define ALLOCATED_ARRAY_HXX
+
+#include "WritableBuffer.hxx"
+#include "Compiler.h"
+
+#include <algorithm>
+
+#include <assert.h>
+
+/**
+ * An array allocated on the heap with a length determined at runtime.
+ */
+template<class T>
+class AllocatedArray {
+	typedef WritableBuffer<T> Buffer;
+
+public:
+	typedef typename Buffer::size_type size_type;
+	typedef typename Buffer::reference_type reference_type;
+	typedef typename Buffer::const_reference_type const_reference_type;
+	typedef typename Buffer::iterator iterator;
+	typedef typename Buffer::const_iterator const_iterator;
+
+protected:
+	Buffer buffer{nullptr};
+
+public:
+	constexpr AllocatedArray() = default;
+
+	explicit AllocatedArray(size_type _size)
+		:buffer{new T[_size], _size} {
+		assert(size() == 0 || buffer.data != nullptr);
+	}
+
+	explicit AllocatedArray(const AllocatedArray &other)
+		:buffer{new T[other.buffer.size], other.buffer.size} {
+		assert(size() == 0 || buffer.data != nullptr);
+		assert(other.size() == 0 || other.buffer.data != nullptr);
+
+		std::copy_n(other.buffer.data, buffer.size, buffer.data);
+	}
+
+	AllocatedArray(AllocatedArray &&other)
+		:buffer(other.buffer) {
+		other.buffer = Buffer::Null();
+	}
+
+	~AllocatedArray() {
+		delete[] buffer.data;
+	}
+
+	AllocatedArray &operator=(const AllocatedArray &other) {
+		assert(size() == 0 || buffer.data != nullptr);
+		assert(other.size() == 0 || other.buffer.data != nullptr);
+
+		if (&other == this)
+			return *this;
+
+		ResizeDiscard(other.size());
+		std::copy_n(other.buffer.data, other.buffer.size, buffer.data);
+		return *this;
+	}
+
+	AllocatedArray &operator=(AllocatedArray &&other) {
+		std::swap(buffer, other.buffer);
+		return *this;
+	}
+
+	constexpr bool IsNull() const {
+		return buffer.IsNull();
+	}
+
+	/**
+	 * Returns true if no memory was allocated so far.
+	 */
+	constexpr bool empty() const {
+		return buffer.IsEmpty();
+	}
+
+	/**
+	 * Returns the number of allocated elements.
+	 */
+	constexpr size_type size() const {
+		return buffer.size;
+	}
+
+	reference_type front() {
+		return buffer.front();
+	}
+
+	const_reference_type front() const {
+		return buffer.front();
+	}
+
+	reference_type back() {
+		return buffer.back();
+	}
+
+	const_reference_type back() const {
+		return buffer.back();
+	}
+
+	/**
+	 * Returns one element.  No bounds checking.
+	 */
+	reference_type operator[](size_type i) {
+		assert(i < size());
+
+		return buffer.data[i];
+	}
+
+	/**
+	 * Returns one constant element.  No bounds checking.
+	 */
+	const_reference_type operator[](size_type i) const {
+		assert(i < size());
+
+		return buffer.data[i];
+	}
+
+	iterator begin() {
+		return buffer.begin();
+	}
+
+	constexpr const_iterator begin() const {
+		return buffer.cbegin();
+	}
+
+	iterator end() {
+		return buffer.end();
+	}
+
+	constexpr const_iterator end() const {
+		return buffer.cend();
+	}
+
+	/**
+	 * Resizes the array, discarding old data.
+	 */
+	void ResizeDiscard(size_type _size) {
+		if (_size == buffer.size)
+			return;
+
+		delete[] buffer.data;
+		buffer.size = _size;
+		buffer.data = new T[buffer.size];
+
+		assert(size() == 0 || buffer.data != nullptr);
+	}
+
+	/**
+	 * Grows the array to the specified size, discarding old data.
+	 * Similar to ResizeDiscard(), but will never shrink the array to
+	 * avoid expensive heap operations.
+	 */
+	void GrowDiscard(size_type _size) {
+		if (_size > buffer.size)
+			ResizeDiscard(_size);
+	}
+
+	/**
+	 * Grows the array to the specified size, preserving the value of a
+	 * range of elements, starting from the beginning.
+	 */
+	void GrowPreserve(size_type _size, size_type preserve) {
+		if (_size <= buffer.size)
+			return;
+
+		T *new_data = new T[_size];
+		assert(_size == 0 || new_data != nullptr);
+
+		std::move(buffer.data, buffer.data + preserve, new_data);
+
+		delete[] buffer.data;
+		buffer.data = new_data;
+		buffer.size = _size;
+	}
+
+	/**
+	 * Declare that the buffer has the specified size.  Must not be
+	 * larger than the current size.  Excess elements are not used (but
+	 * they are still allocated).
+	 */
+	void SetSize(size_type _size) {
+		assert(_size <= buffer.size);
+
+		buffer.size = _size;
+	}
+};
+
+#endif