//

// MemoryStream.h

//

// Library: Foundation

// Package: Streams

// Module:  MemoryStream

//

// Definition of MemoryStreamBuf, MemoryInputStream, MemoryOutputStream

//

// Copyright (c) 2009, Applied Informatics Software Engineering GmbH.

// and Contributors.

//

// SPDX-License-Identifier: BSL-1.0

//

#ifndef Foundation_MemoryStream_INCLUDED

#define Foundation_MemoryStream_INCLUDED

#include "Poco/Bugcheck.h"

#include "Poco/Foundation.h"

#include "Poco/StreamUtil.h"

#include <streambuf>

#include <iosfwd>

#include <ios>

#include <istream>

#include <ostream>

namespace Poco {

template <typename ch, typename tr>

class BasicMemoryStreamBuf: public std::basic_streambuf<ch, tr>

  /// BasicMemoryStreamBuf is a simple implementation of a

  /// stream buffer for reading and writing from a memory area.

  ///

  /// This streambuf only supports unidirectional streams.

  /// In other words, the BasicMemoryStreamBuf can be

  /// used for the implementation of an istream or an

  /// ostream, but not for an iostream.

{

protected:

  using Base = std::basic_streambuf<ch, tr>;

  using IOS = std::basic_ios<ch, tr>;

  using char_type = ch;

  using char_traits = tr;

  using int_type = typename Base::int_type;

  using pos_type = typename Base::pos_type;

  using off_type = typename Base::off_type;

public:

  BasicMemoryStreamBuf(char_type* pBuffer, std::streamsize bufferSize):

    _pBuffer(pBuffer),

    _bufferSize(bufferSize)

  {

    this->setg(_pBuffer, _pBuffer, _pBuffer + _bufferSize);

    this->setp(_pBuffer, _pBuffer + _bufferSize);

  }

  ~BasicMemoryStreamBuf() override = default;

  BasicMemoryStreamBuf() = delete;

  BasicMemoryStreamBuf(const BasicMemoryStreamBuf&) = delete;

  BasicMemoryStreamBuf& operator=(const BasicMemoryStreamBuf&) = delete;

  int_type overflow(int_type /*c*/) override

  {

    return char_traits::eof();

  }

  int_type underflow() override

  {

    return char_traits::eof();

  }

  pos_type seekoff(off_type off, std::ios_base::seekdir way, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out) override

  {

    const pos_type fail = off_type(-1);

    off_type newoff = off_type(-1);

    if ((which & std::ios_base::in) != 0)

    {

      if (this->gptr() == nullptr)

        return fail;

      if (way == std::ios_base::beg)

      {

        newoff = 0;

      }

      else if (way == std::ios_base::cur)

      {

        // cur is not valid if both in and out are specified (Condition 3)

        if ((which & std::ios_base::out) != 0)

          return fail;

        newoff = this->gptr() - this->eback();

      }

      else if (way == std::ios_base::end)

      {

        newoff = this->egptr() - this->eback();

      }

      else

      {

        poco_bugcheck();

      }

      if ((newoff + off) < 0 || (this->egptr() - this->eback()) < (newoff + off))

        return fail;

      this->setg(this->eback(), this->eback() + newoff + off, this->egptr());

    }

    if ((which & std::ios_base::out) != 0)

    {

      if (this->pptr() == nullptr)

        return fail;

      if (way == std::ios_base::beg)

      {

        newoff = 0;

      }

      else if (way == std::ios_base::cur)

      {

        // cur is not valid if both in and out are specified (Condition 3)

        if ((which & std::ios_base::in) != 0)

          return fail;

        newoff = this->pptr() - this->pbase();

      }

      else if (way == std::ios_base::end)

      {

        newoff = this->epptr() - this->pbase();

      }

      else

      {

        poco_bugcheck();

      }

      if (newoff + off < 0 || (this->epptr() - this->pbase()) < newoff + off)

        return fail;

      this->pbump((int)(newoff + off - (this->pptr() - this->pbase())));

    }

    return newoff;

  }

  pos_type seekpos(pos_type pos, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out) override

  {

    const off_type off = pos;

    return seekoff(off, std::ios::beg, which);

  }

  int sync() override

  {

    return 0;

  }

  std::streamsize charsWritten() const

  {

    return static_cast<std::streamsize>(this->pptr() - this->pbase());

  }

  void reset()

    /// Resets the buffer so that current read and write positions

    /// will be set to the beginning of the buffer.

  {

    this->setg(_pBuffer, _pBuffer, _pBuffer + _bufferSize);

    this->setp(_pBuffer, _pBuffer + _bufferSize);

  }

private:

  char_type*      _pBuffer;

  std::streamsize _bufferSize;

};

//

// We provide an instantiation for char

//

using MemoryStreamBuf = BasicMemoryStreamBuf<char, std::char_traits<char>>;

class Foundation_API MemoryIOS: public virtual std::ios

  /// The base class for MemoryInputStream and MemoryOutputStream.

  ///

  /// This class is needed to ensure the correct initialization

  /// order of the stream buffer and base classes.

{

public:

  MemoryIOS(char* pBuffer, std::streamsize bufferSize);

    /// Creates the basic stream.

  ~MemoryIOS() override;

  /// Destroys the stream.

  MemoryStreamBuf* rdbuf();

    /// Returns a pointer to the underlying streambuf.

protected:

  MemoryStreamBuf _buf;

};

class Foundation_API MemoryInputStream: public MemoryIOS, public std::istream

  /// An input stream for reading from a memory area.

{

public:

  MemoryInputStream(const char* pBuffer, std::streamsize bufferSize);

    /// Creates a MemoryInputStream for the given memory area,

    /// ready for reading.

  ~MemoryInputStream() override;

  /// Destroys the MemoryInputStream.

};

class Foundation_API MemoryOutputStream: public MemoryIOS, public std::ostream

  /// An input stream for reading from a memory area.

{

public:

  MemoryOutputStream(char* pBuffer, std::streamsize bufferSize);

    /// Creates a MemoryOutputStream for the given memory area,

    /// ready for writing.

  ~MemoryOutputStream() override;

  /// Destroys the MemoryInputStream.

  std::streamsize charsWritten() const;

    /// Returns the number of chars written to the buffer.

};

//

// inlines

//

inline MemoryStreamBuf* MemoryIOS::rdbuf()

{

  return &_buf;

}

inline std::streamsize MemoryOutputStream::charsWritten() const

{

  return _buf.charsWritten();

}

} // namespace Poco

#endif // Foundation_MemoryStream_INCLUDED