Difference between revisions of "Documentation/DevGuide/Basic/File IO"

Latest revision as of 20:56, 20 December 2020

Apache OpenOffice Basic has a complete set of statements and runtime functions to access the operating system's file system that are compatible to Visual Basic. For platform independence, the ability to handle file names in file:// URL notation has been added.

It is not recommended to use this classic Basic file interface in the UNO context, because many interfaces in the Apache OpenOffice API expect file I/O specific parameters whose types, for example, com.sun.star.io.XInputStream are not compatible with the classic Basic file API.

The module UCB of Basic library Tools of the container OpenOffice Macros shows some examples of file I/O using the API : Function ReadDirectories( ) Sub SaveDataToFile( ) Function LoadDataFromFile( ) Function CreateFolder( )

For programming, the file I/O in Apache OpenOffice API context with the service com.sun.star.ucb.SimpleFileAccess should be used. This service supports the interface com.sun.star.ucb.XSimpleFileAccess2, including the main interface com.sun.star.ucb.XSimpleFileAccess that provides fundamental methods to access the file system. The methods are explained in detail in the corresponding interface documentation. The following list provides an overview about the operations supported by this service:

• copy, move and remove files and folders (methods copy(), move(), kill())
• prompt for information about files and folders (methods isFolder(), isReadOnly(), getSize(), getContentType(), getDateTimeModified(), exists())
• open or create files (openFileRead(), openFileWrite(), openFileReadWrite()). These functions return objects that support the corresponding stream interfaces com.sun.star.io.XInputStream, com.sun.star.io.XOutputStream and com.sun.star.io.XStream. These interfaces are used to read and write files. The XSimpleFileAccess2 does not have methods of its own for these operations. Additionally, these interfaces are often necessary as parameters to access methods of several other interfaces. The opened files have to be closed by calling the appropriate methods closeInput() or closeOutput().
• The XSimpleFileAccess2 also does not have methods to ask for or set the position within a file stream. This is done by calling methods of the com.sun.star.io.XSeekable interface that is supported by the objects returned by the openXXX() methods.

Two more services are instantiated at the global service manager that extends the service com.sun.star.ucb.SimpleFileAccess by functionality specific to text files:

• The service com.sun.star.io.TextInputStream supporting com.sun.star.io.XTextInputStream and com.sun.star.io.XActiveDataSink
• The service is initialized by passing an object supporting XInputStream to the setInputStream() method, for example, an object returned by openFileRead().

Then the method readLine() and readString() are used to read text from the input stream/file. The method isEOF() is used to check for if the end of the file is reached. The setEncoding() sets a text encoding where UTF-8 is the default.

• The service com.sun.star.io.TextOutputStream supporting com.sun.star.io.XTextOutputStream and com.sun.star.io.XActiveDataSource
• The service is initialized by passing an object supporting XOutputStream to the setOutputStream() method, for example, an object returned by openFileWrite().

Then the method writeString() is used to write text to the output stream.