Package nom.tam.util

Class RandomAccessFileChannel

java.lang.Object

nom.tam.util.RandomAccessFileChannel

All Implemented Interfaces:

Closeable, AutoCloseable, InputReader, OutputWriter, RandomAccessFileIO, ReadWriteAccess

public class RandomAccessFileChannel
extends Object
implements RandomAccessFileIO

A random accessible FileChannel implementation for FITS I/O purposes. It enables file-like access for nom-tam-fits that goes beyond local files. This class provides a generic implementation, which may be used, for example, with the NIO SPI file system provider to Amazon S3.

Since:

1.21

Author:

Dustin Jenkins, Attila Kovacs

See Also:

• AWS NIO SPI library
• FitsFile

Constructor Summary

Constructors

Constructor	Description
RandomAccessFileChannel(Path filePath)	Constructor for a readable/writable random accessible FileChannel, which can be used for accessing FITS files.
RandomAccessFileChannel(Path filePath, boolean readOnly)	Constructor for a random accessible FileChannel, for reading or for reading and writing.

Method Summary

Modifier and Type	Method	Description
void	close()
final FileChannel	getChannel()	Obtain the current FileChannel instance.
FileDescriptor	getFD()	Obtain the current FileDescriptor instance.
final long	length()	Returns the current total length of this instance, that is the total number of bytes that may be read from it.
final long	position()	Returns the current read/write position in this instance.
final void	position(long l)	Sets a new position for the next read or write in this instance.
int	read()	Reads a byte.
int	read(byte[] bytes, int offset, int readLength)	Read bytes from the underlying file channel.
String	readUTF()	See RandomAccessFile.readUTF() for a contract of this method.
void	setLength(long l)	See RandomAccessFile.setLength(long) for a contract of this method.
void	write(byte[] bytes, int offset, int writeLength)	Write bytes to the underlying file channel.
void	write(int i)	Writes a byte.
void	writeUTF(String s)	See RandomAccessFile.writeUTF(String) for a contract of this method.

Methods inherited from class java.lang.Object

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

Methods inherited from interface nom.tam.util.RandomAccessFileIO

read, write

Constructor Details

RandomAccessFileChannel

public RandomAccessFileChannel(Path filePath)
                        throws IOException

Constructor for a readable/writable random accessible FileChannel, which can be used for accessing FITS files.

Parameters:

filePath - The path to the file

Throws:

IOException - if the file is not accessible

Since:

1.21

See Also:

• RandomAccessFileChannel(Path, boolean)

RandomAccessFileChannel

public RandomAccessFileChannel(Path filePath,
 boolean readOnly)
                        throws IOException

Constructor for a random accessible FileChannel, for reading or for reading and writing. It may be used for accessing FITS files.

Parameters:

filePath - The path to the file

readOnly - true if the file should only be used for reading, otherwise false.

Throws:

IOException - if the file is not accessible

Since:

1.21

See Also:

• RandomAccessFileChannel(Path, boolean)

Method Details

readUTF

public String readUTF()

Description copied from interface: RandomAccessFileIO

See RandomAccessFile.readUTF() for a contract of this method.

Specified by:

readUTF in interface RandomAccessFileIO

Returns:

Reads a UTF string from the input, up to an EOL termination (with \n) or until the end of file, whichever comes first.

See Also:

• RandomAccessFileIO.writeUTF(String)
• RandomAccessFile.readUTF()

getChannel

public final FileChannel getChannel()

Description copied from interface: RandomAccessFileIO

Obtain the current FileChannel instance. For instances that do not use File backed sources

Specified by:

getChannel in interface RandomAccessFileIO

Returns:

FileChannel instance, possibly null.

See Also:

• RandomAccessFile.getChannel()

getFD

public FileDescriptor getFD()

Description copied from interface: RandomAccessFileIO

Obtain the current FileDescriptor instance.

Specified by:

getFD in interface RandomAccessFileIO

Returns:

FileDescriptor instance, or possibly null.

See Also:

• RandomAccessFile.getFD()

setLength

public void setLength(long l)

Description copied from interface: RandomAccessFileIO

See RandomAccessFile.setLength(long) for a contract of this method.

Specified by:

setLength in interface RandomAccessFileIO

Parameters:

l - The new file length.

See Also:

• RandomAccessFile.setLength(long)

writeUTF

public void writeUTF(String s)

Description copied from interface: RandomAccessFileIO

See RandomAccessFile.writeUTF(String) for a contract of this method.

Specified by:

writeUTF in interface RandomAccessFileIO

Parameters:

s - A java string.

See Also:

• RandomAccessFileIO.readUTF()
• RandomAccessFile.writeUTF(String)

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

position

public final long position()
                    throws IOException

Description copied from interface: ReadWriteAccess

Returns the current read/write position in this instance. The position may exceed the length, depending on implementation, just as seek may go beyond the file size in RandomAccessFile.

Specified by:

position in interface ReadWriteAccess

Returns:

the current read/write position.

Throws:

IOException - if there was an IO error.

See Also:

• ReadWriteAccess.position(long)
• ReadWriteAccess.length()

position

public final void position(long l)
                    throws IOException

Description copied from interface: ReadWriteAccess

Sets a new position for the next read or write in this instance. The position may exceed the length, depending on implementation, just as seek may go beyond the file size in RandomAccessFile.

Specified by:

position in interface ReadWriteAccess

Parameters:

l - the new read/write position.

Throws:

IOException - if there was an IO error.

See Also:

• ReadWriteAccess.position()
• ReadWriteAccess.length()

length

public final long length()

Description copied from interface: ReadWriteAccess

Returns the current total length of this instance, that is the total number of bytes that may be read from it.

Specified by:

length in interface ReadWriteAccess

Returns:

the total number of bytes contained in this instance

read

public int read()

Description copied from interface: InputReader

Reads a byte. See the general contract of FilterInputStream.read().

Specified by:

read in interface InputReader

Returns:

the (unsigned) byte value or -1 if there is nothing left to read.

See Also:

• FilterInputStream.read()

read

public int read(byte[] bytes,
 int offset,
 int readLength)
         throws IOException

Read bytes from the underlying file channel.

Specified by:

read in interface InputReader

Parameters:

bytes - The byte array to read into.

offset - The offset in the FileChannel to start reading.

readLength - The number of bytes to read.

Returns:

The number of bytes read.

Throws:

IOException - If an error occurs reading from the FileChannel.

See Also:

• DataInputStream.read(byte[], int, int)

write

public void write(int i)

Description copied from interface: OutputWriter

Writes a byte. See the general contract of DataOutputStream.write(int).

Specified by:

write in interface OutputWriter

Parameters:

i - the (unsigned) byte value to write.

See Also:

• DataOutputStream.write(int)

write

public void write(byte[] bytes,
 int offset,
 int writeLength)
           throws IOException

Write bytes to the underlying file channel.

Specified by:

write in interface OutputWriter

Parameters:

bytes - The byte array to write.

offset - The offset in the FileChannel to start writing from.

writeLength - The number of bytes to write.

Throws:

IOException - If an error occurs writing to the FileChannel.

See Also:

• DataOutputStream.write(byte[], int, int)