athena/include/Athena/MemoryWriter.hpp

#ifndef MEMORYWRITER_HPP
#define MEMORYWRITER_HPP

#include <string>
#include <memory>
#include <functional>
#include "Athena/IStreamWriter.hpp"

namespace Athena
{
namespace io
{

/*! \class MemoryWriter
 *  \brief A Stream class for writing data to a memory position
 *
 *  A Class for writing binary data to a file or memory stream,
 *  all work is done using a memory buffer, and not written directly to the disk
 *  this allows for fast, flexible code as well as the ability to quickly modify data
 *  \sa Stream
 */
class MemoryWriter : public IStreamWriter
{
public:

    /*! \brief This constructor references an existing buffer to write to in-place.
     *
     *   \param data The existing buffer
     *   \param length The length of the existing buffer
     */
    explicit MemoryWriter(atUint8* data, atUint64 length);

    /*! \brief Sets the buffers position relative to the specified position.<br />
     *         It seeks relative to the current position by default.
     *  \param position where in the buffer to seek
     *  \param origin The Origin to seek \sa SeekOrigin
     */
    void seek(atInt64 pos, SeekOrigin origin = SeekOrigin::Current);


    /*! \brief Returns the current position in the stream.
     *
     *  \return Int64 The current position in the stream.
     */
    inline atUint64 position()    const
    {return m_position;}

    /*! \brief Returns whether or not the stream is at the end.
     *
     *  \return bool True if at end; False otherwise.
     */
    inline atUint64 length()      const
    {return m_length;}

    inline bool isOpen() const {return true;}

    /*! \brief Sets the buffer to the given one, deleting the current one.<br />
     *         <b>BEWARE:</b> As this deletes the current buffer it WILL cause a loss of data
     *         if that was not the intent.<br />
     *         Once you pass the data to setData <b>DO NOT</b> delete the buffer
     *         as Stream now owns the address, this is done to keep memory usage down.
     *  \param data The new buffer.
     *  \param length The length of the new buffer.
     *  \throw IOException
     */
    void  setData(atUint8* data, atUint64 length);


    /*! \brief Returns a copy of the current buffer.<br />
     *         Changes to the copy do not affect the buffer so it's perfectly safe to
     *         directly edit the buffer and use setData to set the new information.<br />
     *         However once you pass the data to setData <b>DO NOT</b> delete the buffer
     *         as Stream now owns the address, this is done to keep memory usage down.
     *  \return Uint8* The copy of the buffer.
     */
    atUint8* data() const;

    /*! \brief Sets the target file
     *
     *  \param filepath The path to write to.
     */
    inline void setFilepath(const std::string& filepath)
    {m_filepath = filepath;}

    /*! \brief
     * Returns the target file
     */
    inline std::string filepath() const
    {return m_filepath;}


    /*! \brief Saves the file to the specified file.
     *
     *   \param filename If not empty, the filename to save to
     */
    void save(const std::string& filename = "");

    /*! \brief Writes the given buffer with the specified length, buffers can be bigger than the length
     *  however it's undefined behavior to try and write a buffer which is smaller than the given length.
     *
     * \param data The buffer to write
     * \param length The amount to write
     */
    void writeUBytes(const atUint8* data, atUint64 len);

protected:
    MemoryWriter() {}
    atUint8*      m_data;
    atUint64      m_length;
    atUint64      m_position;
    std::string   m_filepath; //!< Path to the target file
};

class MemoryCopyWriter : public MemoryWriter
{
public:

    /*! \brief This constructor copies an existing buffer to write to.
     *
     *   \param data The existing buffer
     *   \param length The length of the existing buffer
     */
    explicit MemoryCopyWriter(atUint8* data=nullptr, atUint64 length=0x10);

    /*! \brief This constructor creates an instance from a file on disk.
     *
     * \param filename The file to create the stream from
     */
    MemoryCopyWriter(const std::string& filename);

    /*! \brief Sets the buffers position relative to the specified position.<br />
     *         It seeks relative to the current position by default.
     *  \param position where in the buffer to seek
     *  \param origin The Origin to seek \sa SeekOrigin
     */
    void seek(atInt64 pos, SeekOrigin origin = SeekOrigin::Current);

    /*! \brief Sets the buffer to the given one, deleting the current one.<br />
     *         <b>BEWARE:</b> As this deletes the current buffer it WILL cause a loss of data
     *         if that was not the intent.<br />
     *         Once you pass the data to setData <b>DO NOT</b> delete the buffer
     *         as Stream now owns the address, this is done to keep memory usage down.
     *  \param data The new buffer.
     *  \param length The length of the new buffer.
     *  \throw IOException
     */
    void  setData(const atUint8* data, atUint64 length);

    /*! \brief Writes the given buffer with the specified length, buffers can be bigger than the length
     *  however it's undefined behavior to try and write a buffer which is smaller than the given length.
     *
     * \param data The buffer to write
     * \param length The amount to write
     */
    void writeUBytes(const atUint8* data, atUint64 len);

protected:
    std::unique_ptr<atUint8[]> m_dataCopy;
private:
    void resize(atUint64 newSize);
};

}
}

#ifndef MEMORYWRITER_BASE
#define MEMORYWRITER_BASE() \
    private: \
        typedef Athena::io::MemoryWriter base
#endif // BINARYWRITER_BASE

#ifndef MEMORYCOPYWRITER_BASE
#define MEMORYCOPYWRITER_BASE() \
    private: \
        typedef Athena::io::MemoryCopyWriter base
#endif // BINARYWRITER_BASE

#endif // MEMORYWRITER_HPP