BinaryStream Class

BinaryStream objects are used to read and write data to and from a binary file. The benefit of using BinaryStreams rather than text streams is that you can read from and write to any position in the file.

Events

None

Properties

EOF This property is Read-Only

Methods

Close	ReadPString	WriteDouble
Read	ReadShort	WriteLong
ReadBoolean	ReadSingle	WritePString
ReadByte	Write	WriteShort
ReadDouble	WriteBoolean	WriteSingle
ReadLong	WriteByte

More information available in parent classes: Object

Text files must be read sequentially from the start to the end.

Constructor

Use these constructors to back the BinaryStream from a MemoryBlock or a String instead of a file on disk.

Name	Parameters	Description
BinaryStream	mb as MemoryBlock	Creates a BinaryStream from a MemoryBlock. All BinaryStream functions are supported. If the MemoryBlock was created from a Declare, then the Length property of the BinaryStream will always report -1.
BinaryStream	s as String	Creates a BinaryStream from a String. All BinaryStream functions except writing and setting the length are supported. Sine the string is immutable, the BinaryStream behavior is read only and the write methods of the stream produce an error.

Notes

What is the LittleEndian property? The Windows and Linux operating systems store binary values in the reverse order from the Mac OS. If you were using the ReadShort or ReadLong methods to read data from a file that was in little endian format, you would get incorrect data. REALbasic reads data in big endian format. Most Macintosh files are in big endian format. If you are reading a file that is in little endian format, you will need to set this property to True before you begin reading the file. This applies to writing data with WriteShort and WriteLong.

You can use the constants TargetLittleEndian and TargetBigEndian to determine which byte order is being used for a particular compile.

For example, in big endian (like the Mac OS), the value 258 would be stored as:

01 02

while in little endian, it would be stored as:

02 01

If the LittleEndian property is set incorrectly, then you would read the value as 513.

Because REALbasic has the LittleEndian property, you can write your code to be operating system independent. Set the LittleEndian property to True if the file format is intrinsically little endian (i.e. GIF files), otherwise leave it as False.

The BinaryStream class implements the Readable and Writeable class interfaces. If you implement either or both of these interfaces, you must provide the methods and parameters as specified by those class interfaces.

For more information about class interfaces and how to implement them, see the section "Class Interfaces" on page 440 of the User's Guide.

Example

This example reads each pair of bytes from a file and writes them in reverse order to a new file. The user chooses the source file using the Open-file dialog box and saves the new file using the Save as dialog box.

Dim WriteToFile as BinaryStream
Dim ReadFromFile as BinaryStream
Dim f as FolderItem
f= GetOpenFolderItem("text")
If f <> Nil Then
ReadFromFile=f.OpenAsBinaryFile( False)
ReadFromFile.littleEndian= True
f= GetSaveFolderItem("","")
If f <> Nil Then
  WriteToFile=f.CreateBinaryFile("text")
  While Not ReadFromFile.EOF
   WriteToFile.WriteShort ReadFromFile.ReadShort
  wend
WriteToFile.close
End If
ReadFromFile.close
End If