ttmmap.c

神龙卡开发原代码

  }


/*******************************************************************
 *
 *  Function    : TT_Flush_Stream
 *
 *  Description : Flushes a stream, i.e., closes its file handle.
 *
 *  Input  :  stream         address of target TT_Stream structure
 *
 *  Output :  Error code
 *
 *  NOTE : Never flush the current opened stream.  This means that
 *         you should _never_ call this function between a
 *         TT_Use_Stream() and a TT_Done_Stream()!
 *
 ******************************************************************/
 
  EXPORT_FUNC
  TT_Error  TT_Flush_Stream( TT_Stream*  stream )
  {
    /* XXX - DUMMY IMPLEMENTATION */
    return TT_Err_Ok;
  }


/*******************************************************************
 *
 *  Function    :  TT_Stream_Size
 *
 *  Description :  Returns the length of a given stream, even if it  
 *                 is flushed.
 *
 *  Input  :  stream     the stream
 *
 *  Output :  Length of stream in bytes.            
 *
 ******************************************************************/

  EXPORT_FUNC
  Long  TT_Stream_Size( TT_Stream  stream )
  {
    PStream_Rec  rec = STREAM2REC( stream );


    if ( rec )
      return rec->map->size;
    else
      return 0;  /* invalid stream - return 0 */
  }


/*******************************************************************
 *
 *  Function    : TT_Seek_File
 *
 *  Description : Seeks the file cursor to a different position.
 *
 *  Input  :  position     new position in file
 *
 *  Output :  SUCCESS on success.  FAILURE if out of range.
 *
 ******************************************************************/

  EXPORT_FUNC
  TT_Error  TT_Seek_File( STREAM_ARGS Long  position )
  {
    if ( position > CUR_Stream->map->size )
      return TT_Err_Invalid_File_Offset;

    CUR_Stream->pos = position;

    return TT_Err_Ok;
  }


/*******************************************************************
 *
 *  Function    : TT_Skip_File
 *
 *  Description : Skips forward the file cursor.
 *
 *  Input  :  distance    number of bytes to skip
 *
 *  Output :  see TT_Seek_File
 *
 ******************************************************************/

  EXPORT_FUNC
  TT_Error  TT_Skip_File( STREAM_ARGS Long  distance )
  {
    return TT_Seek_File( STREAM_VARS CUR_Stream->pos + distance );
  }


/*******************************************************************
 *
 *  Function    : TT_Read_File
 *
 *  Description : Reads a chunk of the file and copies it to memory.
 *
 *  Input  :  buffer    target buffer
 *            count     length in bytes to read
 *
 *  Output :  SUCCESS on success.  FAILURE if out of range.
 *
 ******************************************************************/

  EXPORT_FUNC
  TT_Error  TT_Read_File( STREAM_ARGS void*  buffer, Long  count )
  {
    if ( CUR_Stream->pos + count > CUR_Stream->map->size )
      return TT_Err_Invalid_File_Read;

    MEM_Copy( buffer,
              MAP_Address( CUR_Stream->map ) + CUR_Stream->pos, count );
    CUR_Stream->pos += count;

    return TT_Err_Ok;
  }


/*******************************************************************
 *
 *  Function    : TT_Read_At_File
 *
 *  Description : Reads file at a specified position.
 *
 *  Input  :  position  position to seek to before read
 *            buffer    target buffer
 *            count     number of bytes to read
 *
 *  Output :  SUCCESS on success. FAILURE if error.
 *
 ******************************************************************/

  EXPORT_FUNC
  TT_Error  TT_Read_At_File( STREAM_ARGS Long   position,
                                         void*  buffer,
                                         Long   count )
  {
    TT_Error  error;


    if ( (error = TT_Seek_File( STREAM_VARS position ))      || 
         (error = TT_Read_File( STREAM_VARS buffer, count )) )
      return error;

    return TT_Err_Ok;
  }


/*******************************************************************
 *
 *  Function    :  TT_File_Pos
 *
 *  Description :  Returns current file seek pointer.
 *
 *  Input  :  none
 *
 *  Output :  current file position
 *
 ******************************************************************/

  EXPORT_FUNC
  Long  TT_File_Pos( STREAM_ARG )
  {
    return CUR_Stream->pos;
  }


/*******************************************************************
 *
 *  Function    :  TT_Access_Frame
 *
 *  Description :  Notifies the component that we're going to read
 *                 'size' bytes from the current file position.
 *                 This function should load/cache/map these bytes
 *                 so that they will be addressed by the GET_xxx()
 *                 functions easily.
 *
 *  Input  :  size   number of bytes to access.
 *
 *  Output :  Error code
 *
 *  Notes:    The function fails if the byte range is not within the
 *            the file, or if there is not enough memory to cache
 *            the bytes properly (which usually means that aSize is
 *            too big in both cases).
 *
 ******************************************************************/

  EXPORT_FUNC
  TT_Error  TT_Access_Frame( STREAM_ARGS FRAME_ARGS Long  size )
  {
    if ( CUR_Frame.address != NULL )
      return TT_Err_Nested_Frame_Access;

    if ( CUR_Stream->pos + size > CUR_Stream->map->size )
      return TT_Err_Invalid_Frame_Access;

    CUR_Frame.size    = size;
    CUR_Frame.address = MAP_Address( CUR_Stream->map ) + CUR_Stream->pos;
    CUR_Frame.cursor  = CUR_Frame.address;

    CUR_Stream->pos += size;

    return TT_Err_Ok;
  }


/*******************************************************************
 *
 *  Function    :  TT_Check_And_Access_Frame
 *
 *  Description :  Notifies the component that we're going to read
 *                 'size' bytes from the current file position.
 *                 This function should load/cache/map these bytes
 *                 so that they will be addressed by the GET_xxx()
 *                 functions easily.
 *
 *  Input  :  size   number of bytes to access.
 *
 *  Output :  Error code
 *
 *  Notes:    The function truncates 'size' if the byte range is not 
 *            within the file.
 *
 *            It will fail if there is not enough memory to cache
 *            the bytes properly (which usually means that aSize is
 *            too big).
 *
 *            It will fail if you make two consecutive calls
 *            to TT_Access_Frame(), without a TT_Forget_Frame() between
 *            them.
 *
 *            The only difference with TT_Access_Frame() is that we
 *            check that the frame is within the current file.  We
 *            otherwise truncate it.  The 'overflow' is set to zero.
 *
 ******************************************************************/

  EXPORT_FUNC
  TT_Error  TT_Check_And_Access_Frame( STREAM_ARGS FRAME_ARGS Long  size )
  {
    TT_Error  error;
    Long      readBytes;


    if ( CUR_Frame.address != NULL )
      return TT_Err_Nested_Frame_Access;

    readBytes = CUR_Stream->map->size - CUR_Stream->pos;
    if ( size > readBytes )
    {
      /* There is overflow, we allocate a new block then */
      if ( ALLOC( CUR_Frame.address, size ) )
        return error;

      CUR_Frame.size = size;

      /* copy the valid part */
      MEM_Copy( CUR_Frame.address, 
                MAP_Address( CUR_Stream->map ) + CUR_Stream->pos,
                readBytes );
    }
    else
    {
      CUR_Frame.size    = size;
      CUR_Frame.address = MAP_Address( CUR_Stream->map ) + CUR_Stream->pos;
    }

    CUR_Frame.cursor = CUR_Frame.address;
    return TT_Err_Ok;
  }


/*******************************************************************
 *
 *  Function    :  TT_Forget_Frame
 *
 *  Description :  Releases a cached frame after reading.
 *
 *  Input  :  None
 *
 *  Output :  SUCCESS on success.  FAILURE on error.
 *
 ******************************************************************/

  EXPORT_FUNC
  TT_Error  TT_Forget_Frame( FRAME_ARG )
  {
    if ( CUR_Frame.address == NULL )
      return TT_Err_Nested_Frame_Access;

    /* If we were using a duplicate in case of overflow, free it now */
    if ( CUR_Frame.address < (Byte*)CUR_Stream->map->base ||
         CUR_Frame.address >= (Byte*)CUR_Stream->map->base +
         CUR_Stream->map->size )
      FREE( CUR_Frame.address );

    ZERO_Frame( files.frame );

    return TT_Err_Ok;
  }


/*******************************************************************
 *
 *  Function    :  GET_Byte
 *
 *  Description :  Extracts a byte from the current file frame.
 *
 *  Input  :  None or current frame
 *
 *  Output :  Extracted Byte
 *
 *  NOTES : We consider that the programmer is intelligent enough
 *          not to try to get a byte that is out of the frame.  Hence,
 *          we provide no bounds check here. (A misbehaving client
 *          could easily page fault using this call.)
 *
 ******************************************************************/

#if 0

  EXPORT_FUNC
  Byte  TT_Get_Byte( FRAME_ARG )
  {
    CHECK_FRAME( CUR_Frame, 1 );

    return (Byte)(*CUR_Frame.cursor++);
  }

#endif


/*******************************************************************
 *
 *  Function    :  GET_Char
 *
 *  Description :  Extracts a signed byte from the current file frame.
 *
 *  Input  :  None or current frame
 *
 *  Output :  Extracted char
 *
 *  NOTES : We consider that the programmer is intelligent enough
 *          not to try to get a byte that is out of the frame.  Hence,
 *          we provide no bounds check here. (A misbehaving client
 *          could easily page fault using this call.)
 *
 ******************************************************************/

  EXPORT_FUNC
  Char  TT_Get_Char( FRAME_ARG )
  {
    CHECK_FRAME( CUR_Frame, 1 );

    return (Char)(*CUR_Frame.cursor++);
  }


/*******************************************************************
 *
 *  Function    :  GET_Short
 *
 *  Description :  Extracts a short from the current file frame.
 *
 *  Input  :  None or current frame
 *
 *  Output :  Extracted short
 *
 *  NOTES : We consider that the programmer is intelligent enough
 *          not to try to get a byte that is out of the frame.  Hence,
 *          we provide no bounds check here. (A misbehaving client
 *          could easily page fault using this call.)
 *
 ******************************************************************/

  EXPORT_FUNC
  Short  TT_Get_Short( FRAME_ARG )
  {
    Short  getshort;


    CHECK_FRAME( CUR_Frame, 2 );

    getshort = ((Short)CUR_Frame.cursor[0] << 8) |
                (Short)CUR_Frame.cursor[1];

    CUR_Frame.cursor += 2;

    return getshort;
  }


/*******************************************************************
 *
 *  Function    :  GET_UShort
 *
 *  Description :  Extracts an unsigned short from the frame.
 *
 *  Input  :  None or current frame
 *
 *  Output :  Extracted ushort
 *
 *  NOTES : We consider that the programmer is intelligent enough
 *          not to try to get a byte that is out of the frame.  Hence,
 *          we provide no bounds check here. (A misbehaving client
 *          could easily page fault using this call.)
 *
 ******************************************************************/

#if 0

  EXPORT_FUNC
  UShort  TT_Get_UShort( FRAME_ARG )
  {
    UShort  getshort;


    CHECK_FRAME( CUR_Frame, 2 );

    getshort = ((UShort)CUR_Frame.cursor[0] << 8) |
                (UShort)CUR_Frame.cursor[1];

    CUR_Frame.cursor += 2;

    return getshort;
  }

#endif


/*******************************************************************
 *
 *  Function    :  GET_Long
 *
 *  Description :  Extracts a long from the frame.
 *
 *  Input  :  None or current frame
 *
 *  Output :  Extracted long
 *
 *  NOTES : We consider that the programmer is intelligent enough
 *          not to try to get a byte that is out of the frame.  Hence,
 *          we provide no bounds check here. (A misbehaving client
 *          could easily page fault using this call.)
 *
 ******************************************************************/

  EXPORT_FUNC
  Long  TT_Get_Long( FRAME_ARG )
  {
    Long  getlong;


    CHECK_FRAME( CUR_Frame, 4 );

    getlong = ((Long)CUR_Frame.cursor[0] << 24) |
              ((Long)CUR_Frame.cursor[1] << 16) |
              ((Long)CUR_Frame.cursor[2] << 8 ) |
               (Long)CUR_Frame.cursor[3];

    CUR_Frame.cursor += 4;

    return getlong;
  }


/*******************************************************************
 *
 *  Function    :  GET_ULong
 *
 *  Description :  Extracts an unsigned long from the frame.
 *
 *  Input  :  None
 *
 *  Output :  Extracted ulong
 *
 *  NOTES : We consider that the programmer is intelligent enough
 *          not to try to get a byte that is out of the frame.  Hence,
 *          we provide no bounds check here. (A misbehaving client
 *          could easily page fault using this call.)
 *
 ******************************************************************/

#if 0

  EXPORT_FUNC
  ULong  TT_Get_ULong( FRAME_ARG )
  {
    ULong  getlong;


    CHECK_FRAME( CUR_Frame, 4 );

    getlong = ( ((ULong)CUR_Frame.cursor[0] << 24) |
                ((ULong)CUR_Frame.cursor[1] << 16) |
                ((ULong)CUR_Frame.cursor[2] << 8 ) |
                 (ULong)CUR_Frame.cursor[3] );

    CUR_Frame.cursor += 4;

    return getlong;
  }

#endif


/* END */