poco/Foundation/include/Poco/Buffer.h

//
// Buffer.h
//
// $Id: //poco/svn/Foundation/include/Poco/Buffer.h#2 $
//
// Library: Foundation
// Package: Core
// Module:  Buffer
//
// Definition of the Buffer class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_Buffer_INCLUDED
#define Foundation_Buffer_INCLUDED


#include "Poco/Foundation.h"
#include <cstddef>
#include <cstring>


namespace Poco {


template <class T>
class Buffer
	/// A buffer class that allocates a buffer of a given type and size.
	/// Buffer can be zero-size, resized, copy-constructed and assigned.
	/// Memory allocation, resizing and deallocation is managed automatically.
	///
	/// This class is useful everywhere where a temporary buffer
	/// is needed.
{
public:
	Buffer(std::size_t size):
		_size(size),
		_ptr(size ? new T[size] : 0)
		/// Creates and allocates the Buffer.
	{
	}
	
	Buffer(): _size(0),	_ptr(0)
		/// Creates the Buffer.
	{
	}

	Buffer(const Buffer& other):
		/// Copy constructor.
		_size(other._size),
		_ptr(other._size ? new T[other._size] : 0)
	{
		if (_size)
			std::memcpy(_ptr, other._ptr, _size * sizeof(T));
	}

	Buffer& operator = (const Buffer& other)
		/// Assignment operator.
	{
		if (this != &other)
		{
			Buffer tmp(other);
			swap(tmp);
		}

		return *this;
	}

	~Buffer()
		/// Destroys the Buffer.
	{
		delete [] _ptr;
	}
	
	void swap(Buffer& other)
		/// Swaps the buffer with another one.
	{
		using std::swap;
		
		swap(_ptr, other._ptr);
		swap(_size, other._size);
	}

	std::size_t size() const
		/// Returns the size of the buffer.
	{
		return _size;
	}
	
	void clear()
		/// Sets the contents of the bufer to zero.
	{
		std::memset(_ptr, 0, _size * sizeof(T));
	}

	void resize(std::size_t newSize, bool preserve = false)
		/// Resizes the buffer. If preserve is true, the contents
		/// of the buffer is preserved. If the newSize is smaller
		/// than the current size, data truncation will occur.
		/// 
		/// For efficiency sake, the default behavior is not to
		/// preserve the contents.
	{
		if (preserve) 
		{
			if (_size == newSize) return;
			Buffer tmp;
			tmp = *this;
			recreate(newSize);
			std::size_t size = _size < tmp._size ? _size : tmp._size;
			std::memcpy(_ptr, tmp._ptr, size * sizeof(T));
			return;
		}
		else if (_size == newSize) 
		{
			clear();
			return;
		}

		recreate(newSize);
	}

	void append(const T* buf, std::size_t sz)
		/// Resizes this buffer and appends the argument buffer.
	{
		if (0 == sz) return;
		std::size_t oldSize = _size;
		resize(_size + sz, true);
		std::memcpy(_ptr + oldSize, buf, sz);
	}

	void append(const Buffer& buf)
		/// Resizes this buffer and appends the argument buffer.
	{
		append(buf.begin(), buf.size());
	}

	std::size_t elementSize() const
		/// Returns the size of the buffer element.
	{
		return sizeof(T);
	}

	std::size_t byteCount() const
		/// Returns the total length of the buffer in bytes.
	{
		return _size * sizeof(T);
	}

	T* begin()
		/// Returns a pointer to the beginning of the buffer.
	{
		return _ptr;
	}
	
	const T* begin() const
		/// Returns a pointer to the beginning of the buffer.
	{
		return _ptr;
	}

	T* end()
		/// Returns a pointer to end of the buffer.
	{
		return _ptr + _size;
	}
	
	const T* end() const
		/// Returns a pointer to the end of the buffer.
	{
		return _ptr + _size;
	}
	
	bool isEmpty() const
		/// Return true if buffer is empty.
	{
		return 0 == _size;
	}

	T& operator [] (std::size_t index)
	{
		poco_assert (index < _size);
		
		return _ptr[index];
	}

	const T& operator [] (std::size_t index) const
	{
		poco_assert (index < _size);
		
		return _ptr[index];
	}

private:

	void recreate(std::size_t newSize)
	{
		if (newSize != _size)
		{
			delete [] _ptr;
			if (0 == newSize)
				_ptr = 0;
			else
				_ptr = new T[newSize];

			_size = newSize;
		}
	}

	std::size_t _size;
	T*          _ptr;
};


} // namespace Poco


#endif // Foundation_Buffer_INCLUDED