org.projog.core.io

Class FileHandles

java.lang.Object

org.projog.core.io.FileHandles

public final class FileHandles
extends Object

Collection of input and output streams.

Each KnowledgeBase has a single unique FileHandles instance.

See Also:

KnowledgeBase.getFileHandles()

Field Summary

Fields

Modifier and Type	Field and Description
static Atom	USER_INPUT_HANDLE The handle of the "standard" input stream.
static Atom	USER_OUTPUT_HANDLE The handle of the "standard" output stream.

Constructor Summary

Constructors

Constructor and Description
FileHandles()

Method Summary

Modifier and Type	Method and Description
void	close(Term handle) Closes the stream represented by the specified Term.
Term	getCurrentInputHandle() Return the Term representing the current input stream.
InputStream	getCurrentInputStream() Return the current input stream.
Term	getCurrentOutputHandle() Return the Term representing the current output stream.
PrintStream	getCurrentOutputStream() Return the current output stream.
boolean	isHandle(String handle)
Atom	openInput(String fileName) Creates an intput file stream to read from the file with the specified name
Atom	openOutput(String fileName) Creates an output file stream to write to the file with the specified name
void	setInput(Term handle) Sets the current input stream to the input stream represented by the specified Term.
void	setOutput(Term handle) Sets the current output stream to the output stream represented by the specified Term.
void	setUserInput(InputStream is) Reassigns the "standard" input stream.
void	setUserOutput(PrintStream ps) Reassigns the "standard" output stream.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

USER_OUTPUT_HANDLE

public static final Atom USER_OUTPUT_HANDLE

The handle of the "standard" output stream.

By default the "standard" output stream will be System.out.

USER_INPUT_HANDLE

public static final Atom USER_INPUT_HANDLE

The handle of the "standard" input stream.

By default the "standard" input stream will be System.in.

Constructor Detail

FileHandles

public FileHandles()

Method Detail

getCurrentInputHandle

public Term getCurrentInputHandle()

Return the Term representing the current input stream.

By default this will be an Atom with the name "user_input".

getCurrentOutputHandle

public Term getCurrentOutputHandle()

Return the Term representing the current output stream.

By default this will be an Atom with the name "user_output".

getCurrentInputStream

public InputStream getCurrentInputStream()

Return the current input stream.

By default this will be System.in.

getCurrentOutputStream

public PrintStream getCurrentOutputStream()

Return the current output stream.

By default this will be System.out.

setUserInput

public void setUserInput(InputStream is)

Reassigns the "standard" input stream.

See Also:

USER_INPUT_HANDLE

setUserOutput

public void setUserOutput(PrintStream ps)

Reassigns the "standard" output stream.

See Also:

USER_OUTPUT_HANDLE

setInput

public void setInput(Term handle)

Sets the current input stream to the input stream represented by the specified Term.

Throws:

ProjogException - if the specified Term does not represent an Atom

setOutput

public void setOutput(Term handle)

Sets the current output stream to the output stream represented by the specified Term.

Throws:

ProjogException - if the specified Term does not represent an Atom

openInput

public Atom openInput(String fileName)
               throws IOException

Creates an intput file stream to read from the file with the specified name

Parameters:

fileName - the system-dependent filename

Returns:

a reference to the newly created stream (as required by setInput(Term) and close(Term))

Throws:

ProjogException - if this object's collection of input streams already includes the specified file

IOException - if the file cannot be opened for reading

openOutput

public Atom openOutput(String fileName)
                throws IOException

Creates an output file stream to write to the file with the specified name

Parameters:

fileName - the system-dependent filename

Returns:

a reference to the newly created stream (as required by setOutput(Term) and close(Term))

Throws:

ProjogException - if this object's collection of output streams already includes the specified file

IOException - if the file cannot be opened

close

public void close(Term handle)
           throws IOException

Closes the stream represented by the specified Term.

Throws:

ProjogException - if the specified Term does not represent an Atom

IOException - if an I/O error occurs

isHandle

public boolean isHandle(String handle)