CFile:Write


The Write method writes binary data to a file opened in binary mode. The format to use for writing the value or table elements is specified by the sDataType parameter. Also see the WriteBswap method for writing data with a reversed byte order.

Syntax

nBytes = CFile:Write( value, sDataType )

nBytes = CFile:Write( table, sDataType* )

Remarks

This method can write single values or an entire data table to the CFile object. The format used in the output file is not necessarily the same as that of the value being written. For example, suppose value = 12. Then you can write this value as an 8-, 16-, or 32-bit integer or a 32- or 64 bit real number by changing the sDataType string. See Data Types for a description of the available data types and the string to use for sDataType.

Example

The script below provides a complete function to save a lua table to a raw binary file as 64-bit real numbers. The table is a simple array with indices [1] through [ nCols x nRows ].

The nCols and nRows parameters are written individually as "long" (32 bit) integers. Following that is a numeric Data Type code to indicate the table contains 64 bit real numbers. Then the entire table is saved. When using Write for a table, the output data type defaults to 64-bit real values if it is not specified. For the file to end up with the correct length, it is assumed that the number of table elements is nCols x nRows.

 

function Write2dTable( t, nCols, nRows )

 

  if type(t) ~= "table" then return false end

-- failure: a table was not passed

  local sName = GetFileNameSave( "dat" )

-- Get a file name with file type "dat"

  if sName ~= nil then

-- check that a file name was selected

    F = FileOpen( sName, "wb" )

-- Open the file for writing binary data

    if F ~= nil then

-- if the file was opened

      F:Write( nCols, "long" )

-- number of columns as a long integer

      F:Write( nRows, "long" )

-- number of rows as a long integer

      F:Write( 6, "long" )

-- 6 = code for 64-bit real number data

      F:Write( t )

-- write the table as 64-bit real values.

      F:Close()

-- remember to close the file when done

      return true

-- success

    end

 

  end

 

  return false

-- failure

end

 

Related Topics

CFile Class, WriteBswap, Read, File Access Modes