xml_transport.h

#pragma once

//          Copyright David Lawrence Bien 1997 - 2021.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt).

// xml_transport.h
// Declare XML output transport classes.
// dbien
// 17FEB2021

#include "xml_types.h"
#include "_fdobjs.h"

__XMLP_BEGIN_NAMESPACE

// xml_write_transport_file:
// Write XML to a file.
template < class t_TyChar, class t_TyFSwitchEndian >
class xml_write_transport_file
{
  typedef xml_write_transport_file _TyThis;
public:
  typedef t_TyChar _TyChar;
  typedef t_TyFSwitchEndian _TyFSwitchEndian;
  // We don't need to open a xml_write_transport_file read/write, as we do for a xml_write_transport_mapped.
  typedef false_type _TyFOpenFileReadWrite;
  typedef unique_ptr< _TyChar[] > _TyBuffer;

  xml_write_transport_file() = delete;
  xml_write_transport_file( FileObj & _rfoFile, bool _fWriteBOM, size_t _nchWriteBuffer = 4096 )
    : m_foFile( std::move( _rfoFile ) ),
      m_nchWriteBuffer( _nchWriteBuffer )
  {
#ifdef _MSC_VER
    m_upBuffer = make_unique_for_overwrite< _TyChar[] >( m_nchWriteBuffer );
#else
    m_upBuffer = _TyBuffer( new _TyChar[ m_nchWriteBuffer ] );
#endif
    m_pcBufCur = &m_upBuffer[0];
    VerifyThrow( m_foFile.FIsOpen() );
    if ( _fWriteBOM )
      WriteBOM< _TyChar, _TyFSwitchEndian >( m_foFile.HFileGet() );
    // Leave the file right where it is.
  }
  xml_write_transport_file( xml_write_transport_file const & ) = delete;
  xml_write_transport_file & operator =( xml_write_transport_file const & ) = delete;
  xml_write_transport_file( xml_write_transport_file && _rr )
  {
    swap( _rr );
  }
  xml_write_transport_file & operator =( xml_write_transport_file && _rr )
  {
    _TyThis acquire( std::move( _rr ) );
    swap( acquire );
    return *this;
  }
  void swap( _TyThis & _r )
  {
    m_foFile.swap( _r.m_foFile );
    m_upBuffer.swap( _r.m_upBuffer );
    std::swap( m_nchWriteBuffer, _r.m_nchWriteBuffer );
    std::swap( m_pcBufCur, _r.m_pcBufCur );
  }
  ~xml_write_transport_file()
  {
    bool fInUnwinding = !!std::uncaught_exceptions();
    if ( !!m_pcBufCur && ( m_pcBufCur != &m_upBuffer[0] ) )
    {
      bool fFlush = _FFlushBuffer();
      if ( !fFlush )
      {
        if ( !fInUnwinding )
          THROWNAMEDEXCEPTIONERRNO( GetLastErrNo(), "Failed to write to file handle [0x%zx].", (size_t)m_foFile.HFileGet() );
        else
        {
          try
          {
            LOGSYSLOGERRNO( eslmtError, GetLastErrNo(), "Failed to write to file handle [0x%zx].", (size_t)m_foFile.HFileGet() );
          }
          catch( ... )
          {
            // can't throw - we are in an unwinding.
          }
        }
      }
    }
  }
  // Write any character type to the transport - it will do the appropriate translation and it needn't even buffer anything...
  template < class t_TyCharWrite >
  void Write( const t_TyCharWrite * _pcBegin, const t_TyCharWrite * _pcEnd )
  {
    // We send to the conversion template which will call back into this:
    VerifyThrow( FWriteUTFStream< _TyChar >( _pcBegin, _pcEnd - _pcBegin, *this ) );
  }
  bool FWrite( const _TyChar * _pcBuf, size_t _nch ) noexcept
  {
    // Write to the buffer until it is full and then empty it into the file:
    const _TyChar * const pcEndBuf = _PcEndBuf();
    const _TyChar * pcBufWriteCur = _pcBuf;
    for ( size_t nchRemaining = _nch; nchRemaining; )
    {
      size_t nchLeftInBuf = pcEndBuf - m_pcBufCur;
      size_t nchWrite = (min)( nchLeftInBuf, nchRemaining );
      nchRemaining -= nchWrite;
      memcpy( m_pcBufCur, pcBufWriteCur, nchWrite * sizeof( _TyChar ) );
      pcBufWriteCur += nchWrite;
      m_pcBufCur += nchWrite;
      if ( m_pcBufCur == pcEndBuf )
      {
        if ( !_FFlushBuffer() )
          return false;
        m_pcBufCur = &m_upBuffer[0];
      }
    }
    return true;
  }
  static constexpr EFileCharacterEncoding GetEncoding()
  {
    return GetCharacterEncoding< _TyChar, _TyFSwitchEndian >();
  }
protected:
  // We want these calls to be noexcept. We write to the buffer in non-switch-endian
  //  for debugging purposes. Then when the buffer is full we write to the file, switching
  //  the endian of the buffer first.
  bool _FFlushBuffer() noexcept
    requires( is_same_v< _TyFSwitchEndian, false_type > )
  {
    return _FFlushBufferNoSwitchEndian();
  }
  bool _FFlushBufferNoSwitchEndian()
  {
    Assert( !!m_pcBufCur && ( m_pcBufCur != &m_upBuffer[0] ) );
    size_t nbyWrite = ( m_pcBufCur - &m_upBuffer[0] ) * sizeof( _TyChar );
    int iResult = FileWrite( m_foFile.HFileGet(), &m_upBuffer[0], nbyWrite );
    return !iResult;
  }
  bool _FFlushBuffer() noexcept
    requires( is_same_v< _TyFSwitchEndian, true_type > )
  {
    Assert( !!m_pcBufCur && ( m_pcBufCur != &m_upBuffer[0] ) );
    SwitchEndian( &m_upBuffer[0], m_pcBufCur );
    return _FFlushBufferNoSwitchEndian();
  }
  _TyChar * _PcEndBuf()
  {
    Assert( !!m_upBuffer );
    return &m_upBuffer[m_nchWriteBuffer-1] + 1;
  }
  FileObj m_foFile;
  _TyBuffer m_upBuffer;
  size_t m_nchWriteBuffer{0};
  _TyChar * m_pcBufCur{nullptr};
};

// xml_write_transport_mapped:
// Write XML to a mapped file.
template < class t_TyChar, class t_TyFSwitchEndian >
class xml_write_transport_mapped
{
  typedef xml_write_transport_mapped _TyThis;
public:
  typedef t_TyChar _TyChar;
  typedef t_TyFSwitchEndian _TyFSwitchEndian;
  // We must map a xml_write_transport_mapped read/write because we must map it read/write.
  typedef true_type _TyFOpenFileReadWrite;
  static const size_t s_knGrowFileByBytes = 16384 * sizeof( _TyChar ); // As we write the file grow it in this increment.

  xml_write_transport_mapped( FileObj & _rfoFile, bool _fWriteBOM )
    : m_foFile( std::move( _rfoFile ) )
  {
    VerifyThrow( m_foFile.FIsOpen() );
    // Write the BOM and then initialize the file.
    if ( _fWriteBOM )
      WriteBOM< _TyChar, _TyFSwitchEndian >( m_foFile.HFileGet() );
    // Leave the file right where it is and map it here - the mapping will take care of correctly offsetting everything.
	  m_nbyMapAtPosition = (uint64_t)NFileSeekAndThrow(m_foFile.HFileGet(), 0, vkSeekCur);
    size_t stMapBytes = s_knGrowFileByBytes;
    int iResult = FileSetSize( m_foFile.HFileGet(), m_nbyMapAtPosition + stMapBytes ); // Set initial size.
    if ( !!iResult )
      THROWNAMEDEXCEPTIONERRNO(GetLastErrNo(), "FileSetSize() failed.");
    uint64_t u64SizeMapping;
    uint64_t u64ResultMapAtPosition = m_nbyMapAtPosition; // The result will be m_nbyMapAtPosition % PageSize().
    m_fmoMap.SetHMMFile( MapReadWriteHandle( m_foFile.HFileGet(), &u64SizeMapping, &u64ResultMapAtPosition ) );
    if ( !m_fmoMap.FIsOpen() )
      THROWNAMEDEXCEPTIONERRNO(GetLastErrNo(), "MapReadWriteHandle() failed.");
    Assert( size_t( u64SizeMapping - u64ResultMapAtPosition ) == stMapBytes );
    m_pcCur = m_pcBase = (_TyChar*)m_fmoMap.Pby( (size_t)u64ResultMapAtPosition );
    m_pcEnd = m_pcCur + ( stMapBytes / sizeof( _TyChar) );
  }

  ~xml_write_transport_mapped()
  {
    bool fInUnwinding = !!std::uncaught_exceptions();
    (void)_Close( !fInUnwinding ); // Only throw on error from close if we are not currently unwinding.
  }

  // Write any character type to the transport - it will do the appropriate translation and it needn't even buffer anything...
  template < class t_TyCharWrite >
  void Write( const t_TyCharWrite * _pcBegin, const t_TyCharWrite * _pcEnd )
  {
    // We send to the conversion template which will call back into this:
    VerifyThrow( FWriteUTFStream< _TyChar >( _pcBegin, _pcEnd - _pcBegin, *this ) );
  }
  // We want these calls to be noexcept.
  bool FWrite( const _TyChar * _pcBuf, size_t _nch ) noexcept
    requires( is_same_v< _TyFSwitchEndian, false_type > )
  {
    int iResult = _CheckGrowMapNoThrow( _nch );
    if ( !iResult )
    {
      memcpy( m_pcCur, _pcBuf, _nch * sizeof( _TyChar ) );
      m_pcCur += _nch;
    }
    return !iResult;
  }
  // We want these calls to be noexcept.
  bool FWrite( const _TyChar * _pcBuf, size_t _nch ) noexcept
    requires( is_same_v< _TyFSwitchEndian, true_type > )
  {
    int iResult = _CheckGrowMapNoThrow( _nch );
    if ( !iResult )
    {
      memcpy( m_pcCur, _pcBuf, _nch * sizeof( _TyChar ) );
      SwitchEndian( m_pcCur, _nch );
      m_pcCur += _nch;
    }
    return !iResult;
  }
  static constexpr EFileCharacterEncoding GetEncoding()
  {
    return GetCharacterEncoding< _TyChar, _TyFSwitchEndian >();
  }
protected:
  // Don't throw - return 0 on success, non-zero on failure.
  int _CheckGrowMapNoThrow( size_t _charsByAtLeast ) noexcept
  {
    try
    {
      if ( size_t( m_pcEnd - m_pcCur ) < _charsByAtLeast )
        _GrowMap( _charsByAtLeast );
      return 0;
    }
    catch( std::exception const & _rexc )
    {
      n_SysLog::Log( eslmtError, "Caught exception [%s]", _rexc.what() );
      return -1;
    }
  }
  void _GrowMap( size_t _charsByAtLeast )
  {
    VerifyThrow( m_foFile.FIsOpen() && m_fmoMap.FIsOpen() );
    // unmap, grow file, remap. That was easy!
    size_t nbyGrowAtLeast = _charsByAtLeast * sizeof( _TyChar ); // scale from chars to bytes.
    size_t nbyGrowBy = (((nbyGrowAtLeast - 1) / s_knGrowFileByBytes) + 1) * s_knGrowFileByBytes;
    size_t nbyOldMapping = ( m_pcEnd - m_pcBase ) * sizeof( _TyChar );
    (void)m_fmoMap.Close();
    int iFileSetSize = FileSetSize( m_foFile.HFileGet(), m_nbyMapAtPosition + nbyOldMapping + nbyGrowBy );
    if (-1 == iFileSetSize)
      THROWNAMEDEXCEPTIONERRNO( GetLastErrNo(), "FileSetSize() failed." );
    uint64_t u64SizeMapping;
    uint64_t u64ResultMapAtPosition = m_nbyMapAtPosition; // The result will be m_nbyMapAtPosition % PageSize().
    m_fmoMap.SetHMMFile( MapReadWriteHandle( m_foFile.HFileGet(), &u64SizeMapping, &u64ResultMapAtPosition ) );
    if ( !m_fmoMap.FIsOpen() )
      THROWNAMEDEXCEPTIONERRNO( GetLastErrNo(), "Remapping failed." );
    Assert( ( u64SizeMapping - u64ResultMapAtPosition ) == nbyOldMapping + nbyGrowBy );
    size_t nchOffsetCur = m_pcCur - m_pcBase;
    m_pcBase = (_TyChar*)m_fmoMap.Pby( (size_t)u64ResultMapAtPosition );
    m_pcEnd = m_pcBase + ( u64SizeMapping / sizeof( _TyChar) );
    m_pcCur = m_pcBase + nchOffsetCur;
  }
  // Allow throwing on error because closing actually does something and we need to know if it succeeds.
  int _Close( bool _fThrowOnError ) noexcept(false)
  {
    if ( !m_fmoMap.FIsOpen() )
    {
      // Not much to do cuz we don't know about the size of the mapping, etc. Just close the file.
      m_foFile.Close();
      return 0;
    }
    int iCloseFileMapping = m_fmoMap.Close();
    vtyErrNo errCloseFileMapping = !iCloseFileMapping ? vkerrNullErrNo : GetLastErrNo();
    vtyErrNo errTruncate = vkerrNullErrNo;
    vtyErrNo errCloseFile = vkerrNullErrNo;
    if ( m_foFile.FIsOpen() )
    {
      // We need to truncate the file to m_pcCur - m_pcBase bytes.
      size_t nbySizeTruncate = ( m_pcCur - m_pcBase ) * sizeof( _TyChar );
      int iTruncate = FileSetSize(m_foFile.HFileGet(), m_nbyMapAtPosition + nbySizeTruncate );
      errTruncate = !iTruncate ? vkerrNullErrNo : GetLastErrNo();
      int iClose = m_foFile.Close();
      errCloseFile = !iClose ? vkerrNullErrNo : GetLastErrNo();
    }
    vtyErrNo errFirst;
    unsigned nError;
    if ( ( (nError = 1), ( vkerrNullErrNo != ( errFirst = errTruncate ) ) ) || 
         ( (nError = 2), ( vkerrNullErrNo != ( errFirst = errCloseFileMapping ) ) ) ||
         ( (nError = 3), ( vkerrNullErrNo != ( errFirst = errCloseFile ) ) ) )
    {
      // Ensure that the errno is represented in the last error:
      SetLastErrNo( errFirst );
      if ( _fThrowOnError )
      {
        const char * pcThrow;
        switch( nError )
        {
          case 1: pcThrow = "Error encountered truncating."; break;
          case 2: pcThrow = "Error encountered closing file mapping."; break;
          case 3: pcThrow = "Error encountered closing file."; break;
          default: pcThrow = "Wh-what?!"; break;
        }
        THROWNAMEDEXCEPTIONERRNO( errFirst, pcThrow );
      }
    }
    return errFirst == vkerrNullErrNo ? 0 : -1;
  }

  FileObj m_foFile;
  FileMappingObj m_fmoMap;
  uint64_t m_nbyMapAtPosition{0}; // We save this because we may be growing the file.
  _TyChar * m_pcBase{nullptr};
  _TyChar * m_pcCur{nullptr};
  _TyChar * m_pcEnd{nullptr};
};

// xml_write_transport_memstream:
// Write XML to a memstream - an in-memory stream impl.
template < class t_TyChar, class t_TyFSwitchEndian >
class xml_write_transport_memstream
{
  typedef xml_write_transport_memstream _TyThis;
public:
  typedef t_TyChar _TyChar;
  typedef t_TyFSwitchEndian _TyFSwitchEndian;
  typedef MemStream< size_t, false > _TyMemStream;
  typedef MemFileContainer< size_t, false > _TyMemFileContainer;
  static const size_t s_knbyChunkSizeMemStream = 4096; // Needs to be divisible by sizeof( char32_t ).

  xml_write_transport_memstream( xml_write_transport_memstream const & ) = delete;
  xml_write_transport_memstream & operator =( xml_write_transport_memstream const & ) = delete;
  xml_write_transport_memstream( bool _fWriteBOM )
  {
    // Create a new memstream object. The MemFileContainer just goes away - just really there for creating the shared memfile object initially.
    {//B
      _TyMemFileContainer mfc( s_knbyChunkSizeMemStream );
      mfc.OpenStream( m_msMemStream );
    }//EB
    if ( _fWriteBOM )
    {
      EFileCharacterEncoding efce = GetCharacterEncoding< _TyChar, _TyFSwitchEndian >();
      Assert( efceFileCharacterEncodingCount != efce );
      VerifyThrowSz( efceFileCharacterEncodingCount != efce, "Unknown char/switch endian encoding." );
      string strBOM = StrGetBOMForEncoding( efce );
      m_msMemStream.Write( strBOM.c_str(), strBOM.length() );
    }
  }
  xml_write_transport_memstream( _TyMemStream && _rrmsMemStream )
    requires( is_same_v< _TyFSwitchEndian, false_type > )
    : m_msMemStream( std::move( _rrmsMemStream ) )
  {
  }
  xml_write_transport_memstream( _TyMemStream && _rrmsMemStream )
    requires( is_same_v< _TyFSwitchEndian, true_type > )
    : m_msMemStream( std::move( _rrmsMemStream ) )
  {
    // For switch endian we need to switch the bytes and we didn't write the code to switch bytes within
    //  a single character that straddles a segment boundary in the SegArray.
    VerifyThrowSz( !( m_msMemStream.GetCurPos() % sizeof( _TyChar ) ), "For switch endian xml_write_transport_memstream<> must start at a multiple of a character size." );
  }
  _TyMemStream & GetMemStream() 
  {
    return m_msMemStream;
  }
  const _TyMemStream & GetMemStream() const
  {
    return m_msMemStream;
  }
  // Write any character type to the transport - it will do the appropriate translation and it needn't even buffer anything...
  template < class t_TyCharWrite >
  void Write( const t_TyCharWrite * _pcBegin, const t_TyCharWrite * _pcEnd )
  {
    // We send to the conversion template which will call back into this:
    VerifyThrow( FWriteUTFStream< _TyChar >( _pcBegin, _pcEnd - _pcBegin, *this ) );
  }
  // We want these calls to be noexcept.
  bool FWrite( const _TyChar * _pcBuf, size_t _nch ) noexcept
    requires( is_same_v< _TyFSwitchEndian, false_type > )
  {
    ssize_t sstResult = m_msMemStream.WriteNoExcept( _pcBuf, _nch * sizeof ( _TyChar ) );
    return !( sstResult < 0 ) && size_t( sstResult ) == ( _nch * sizeof ( _TyChar ) );
  }
  // We want these calls to be noexcept.
  bool FWrite( const _TyChar * _pcBuf, size_t _nch ) noexcept
    requires( is_same_v< _TyFSwitchEndian, true_type > )
  {
    size_t nPosInit = m_msMemStream.GetCurPos();
    ssize_t sstResult = m_msMemStream.WriteNoExcept( _pcBuf, _nch * sizeof ( _TyChar ) );
    if ( !( sstResult < 0 ) && size_t( sstResult ) == ( _nch * sizeof ( _TyChar ) ) )
    {
      m_msMemStream.Apply( nPosInit, m_msMemStream.GetCurPos(), 
        []( vtyMemStreamByteType * _pbyBegin, vtyMemStreamByteType * _pbyEnd )
        {
          Assert( !( ( _pbyEnd - _pbyBegin ) % sizeof ( _TyChar ) ) );
          SwitchEndian( (_TyChar*)_pbyBegin, (_TyChar*)_pbyEnd );
        }
      );
      return true;
    }
    return false;
  }
  static constexpr EFileCharacterEncoding GetEncoding()
  {
    return GetCharacterEncoding< _TyChar, _TyFSwitchEndian >();
  }
protected:
  _TyMemStream m_msMemStream;
};

// xml_write_transport_var:
// Variant transport. Not sure if this is necessary.
template < class ... T_TysTransports >
class xml_write_transport_var
{
  typedef xml_write_transport_var _TyThis;
public:

protected:
};

__XMLP_END_NAMESPACE