BansheeEngine/BansheeUtility/Include/BsDataStream.h

#pragma once

#include "BsPrerequisitesUtil.h"
#include <istream>

namespace BansheeEngine 
{
	/** @addtogroup Filesystem
	 *  @{
	 */

	/** Supported encoding types for strings. */
	enum class StringEncoding
	{
		UTF8 = 1,
		UTF16 = 2
	};

	/**
	 * General purpose class used for encapsulating the reading and writing of data from and to various sources using a 
	 * common interface.
	 */
	class BS_UTILITY_EXPORT DataStream
	{
	public:
		enum AccessMode
		{
			READ = 1, 
			WRITE = 2
		};

	public:
        /** Creates an unnamed stream. */
        DataStream(UINT16 accessMode = READ) 
			:mSize(0), mAccess(accessMode) 
		{ }

        /** Creates a named stream. */
		DataStream(const String& name, UINT16 accessMode = READ) 
			:mName(name), mSize(0), mAccess(accessMode) {}

		virtual ~DataStream() {}

		const String& getName(void) { return mName; }
		UINT16 getAccessMode() const { return mAccess; }

		virtual bool isReadable() const { return (mAccess & READ) != 0; }
		virtual bool isWriteable() const { return (mAccess & WRITE) != 0; }
       
        /** Reads data from the buffer and copies it to the specified value. */
        template<typename T> DataStream& operator>>(T& val);

		/**
		 * Read the requisite number of bytes from the stream, stopping at the end of the file.
		 *
		 * @param[in]	buf		Pre-allocated buffer to read the data into.
		 * @param[in]	count	Number of bytes to read.
		 * @return				Number of bytes actually read.
		 * 			
		 * @note	Stream must be created with READ access mode.
		 */
		virtual size_t read(void* buf, size_t count) = 0;

		/**
		 * Write the requisite number of bytes to the stream.
		 *
		 * @param[in]	buf		Buffer containing bytes to write.
		 * @param[in]	count	Number of bytes to write.
		 * @return				Number of bytes actually written.
		 * 			
		 * @note	Stream must be created with WRITE access mode.
		 */
		virtual size_t write(const void* buf, size_t count) { return 0; }

		/**
		 * Writes the provided narrow string to the steam. String is convered to the required encoding before being written.
		 * 			
		 * @param[in]	string		String containing narrow characters to write, encoded as UTF8.
		 * @param[in]	encoding	Encoding to convert the string to before writing.
		 */
		virtual void writeString(const String& string, StringEncoding encoding = StringEncoding::UTF8);

		/**
		 * Writes the provided wide string to the steam. String is convered to the required encoding before being written.
		 * 			
		 * @param[in]	string		String containing wide characters to write, encoded as specified by platform for 
		 * 							wide characters.
		 * @param[in]	encoding	Encoding to convert the string to before writing.
		 */
		virtual void writeString(const WString& string, StringEncoding encoding = StringEncoding::UTF16);

	    /**
	     * Returns a string containing the entire stream.
	     *
		 * @return	String data encoded as UTF-8. 
		 *
		 * @note	This is a convenience method for text streams only, allowing you to retrieve a String object containing 
		 *			all the data in the stream.
	     */
	    virtual String getAsString();

	    /**
	     * Returns a wide string containing the entire stream.
	     *
		 * @return	Wide string encoded as specified by current platform.
		 *
		 * @note	This is a convenience method for text streams only, allowing you to retrieve a WString object 
		 *			containing all the data in the stream.
	     */
	    virtual WString getAsWString();

		/**
		 * Skip a defined number of bytes. This can also be a negative value, in which case the file pointer rewinds a 
		 * defined number of bytes.
		 */
		virtual void skip(size_t count) = 0;
	
	    /** Repositions the read point to a specified byte. */
	    virtual void seek(size_t pos) = 0;
		
	    /** Returns the current byte offset from beginning. */
	    virtual size_t tell() const = 0;

	    /** Returns true if the stream has reached the end. */
	    virtual bool eof() const = 0;

        /** Returns the total size of the data to be read from the stream, or 0 if this is indeterminate for this stream. */
        size_t size() const { return mSize; }

        /** Close the stream. This makes further operations invalid. */
        virtual void close() = 0;
		
	protected:
		static const UINT32 StreamTempSize;

		String mName;		
        size_t mSize;
		UINT16 mAccess;
	};

	/** Data stream for handling data from memory. */
	class BS_UTILITY_EXPORT MemoryDataStream : public DataStream
	{		
	public:
		/**
		 * Wrap an existing memory chunk in a stream.
		 *
		 * @param[in] 	memory		Memory to wrap the data stream around.
		 * @param[in]	size		Size of the memory chunk in bytes.
		 */
		MemoryDataStream(void* memory, size_t size);
		
		/**
		 * Create a stream which pre-buffers the contents of another stream. Data from the other buffer will be entirely 
		 * read and stored in an internal buffer.
		 *
		 * @param[in]	sourceStream		Stream to read data from.
		 */
		MemoryDataStream(DataStream& sourceStream);
		
		/**
		 * Create a stream which pre-buffers the contents of another stream. Data from the other buffer will be entirely 
		 * read and stored in an internal buffer.
		 *
		 * @param[in]	sourceStream		Stream to read data from.
		 */
		MemoryDataStream(const DataStreamPtr& sourceStream);

		~MemoryDataStream();

		/** Get a pointer to the start of the memory block this stream holds. */
		UINT8* getPtr() const { return mData; }
		
		/** Get a pointer to the current position in the memory block this stream holds. */
		UINT8* getCurrentPtr() const { return mPos; }
		
        /** @copydoc DataStream::read */
		size_t read(void* buf, size_t count) override;

        /** @copydoc DataStream::write */
		size_t write(const void* buf, size_t count) override;

        /** @copydoc DataStream::skip */
		void skip(size_t count) override;
	
        /** @copydoc DataStream::seek */
		void seek(size_t pos) override;
		
        /** @copydoc DataStream::tell */
		size_t tell() const override;

        /** @copydoc DataStream::eof */
		bool eof() const override;

        /** @copydoc DataStream::close */
		void close() override;

	protected:
		UINT8* mData;
		UINT8* mPos;
		UINT8* mEnd;

		bool mFreeOnClose;
	};

	/** Data stream for handling data from standard streams. */
	class BS_UTILITY_EXPORT FileDataStream : public DataStream
	{
	public:
		/**
		 * Construct read-only stream from an standard stream.
		 *
		 * If @p freeOnClose is true, the STL stream will be freed once the data stream is closed.
		 */
		FileDataStream(std::shared_ptr<std::ifstream> s, bool freeOnClose = true);

		/**
		 * Construct read-write stream from an standard stream.
		 * 			
		 * If @p freeOnClose is true, the STL stream will be freed once the data stream is closed.
		 */
		FileDataStream(std::shared_ptr<std::fstream> s, bool freeOnClose = true);

		/**
		 * Construct read-only stream from an standard stream, and tell it the size.
		 * 			
		 * Size parameter allows you to specify the size without requiring us to seek to the end of the stream to find 
		 * the size.
		 *			
		 * If @p freeOnClose is true, the STL stream will be freed once the data stream is closed.
		 */
		FileDataStream(std::shared_ptr<std::ifstream> s, size_t size, bool freeOnClose = true);

		/**
		 * Construct read-write stream from an standard stream, and tell it the size.
		 * 			
		 * Size parameter allows you to specify the size without requiring us to seek to the end of the stream to find 
		 * the size.
		 *			
		 * If @p freeOnClose is true, the STL stream will be freed once the data stream is closed.
		 */
		FileDataStream(std::shared_ptr<std::fstream> s, size_t size, bool freeOnClose = true);

		~FileDataStream();

        /** @copydoc DataStream::read */
		size_t read(void* buf, size_t count) override;

        /** @copydoc DataStream::write */
		size_t write(const void* buf, size_t count) override;

        /** @copydoc DataStream::skip */
		void skip(size_t count) override;
	
        /** @copydoc DataStream::seek */
		void seek(size_t pos) override;

        /** @copydoc DataStream::tell */
		size_t tell() const override;

        /** @copydoc DataStream::eof */
		bool eof() const override;

        /** @copydoc DataStream::close */
		void close() override;

	protected:
		std::shared_ptr<std::istream> mpInStream;
		std::shared_ptr<std::ifstream> mpFStreamRO;
		std::shared_ptr<std::fstream> mpFStream;
		bool mFreeOnClose;	

		void determineAccess();
	};

	/** @} */
}