gov.nasa.pds.objectAccess

Class ByteWiseFileAccessor

java.lang.Object

gov.nasa.pds.objectAccess.ByteWiseFileAccessor

public class ByteWiseFileAccessor
extends Object

Class that provides common I/O functionality for PDS data objects.

Constructor Summary

Constructors

Constructor and Description
ByteWiseFileAccessor(File file, long offset, int length, int records) Constructs a ByteWiseFileAccessor object which maps a region of a data file into memory.
ByteWiseFileAccessor(URL url, long offset, int length) Constructor.
ByteWiseFileAccessor(URL url, long offset, int length, int records) Constructs a ByteWiseFileAccessor object which maps a region of a data file into memory.
ByteWiseFileAccessor(URL url, long offset, int length, int records, boolean checkSize) Constructs a ByteWiseFileAccessor object which maps a region of a data file into memory.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	hasRemaining() Checks to see if the buffer can still be read.
void	mark() Marks the buffer.
byte	readByte() Reads a byte from the buffer.
byte[]	readRecordBytes(int recordNum, int offset, int length) Reads length bytes of data from a specified record at the given offset.
void	reset() Resets the buffer.

Methods inherited from class java.lang.Object

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

Constructor Detail

ByteWiseFileAccessor

public ByteWiseFileAccessor(File file,
                    long offset,
                    int length,
                    int records)
                     throws FileNotFoundException,
                            IOException

Constructs a ByteWiseFileAccessor object which maps a region of a data file into memory.

Parameters:

file - the data file

offset - the offset within the data file

length - the record length in bytes

records - the number of records

Throws:

FileNotFoundException - If file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading

IOException - If an I/O error occurs

ByteWiseFileAccessor

public ByteWiseFileAccessor(URL url,
                    long offset,
                    int length,
                    int records)
                     throws FileNotFoundException,
                            IOException

Constructs a ByteWiseFileAccessor object which maps a region of a data file into memory.

Parameters:

url - the data file

offset - the offset within the data file

length - the record length in bytes

records - the number of records

Throws:

FileNotFoundException - If file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading

IOException - If an I/O error occurs

ByteWiseFileAccessor

public ByteWiseFileAccessor(URL url,
                    long offset,
                    int length,
                    int records,
                    boolean checkSize)
                     throws FileNotFoundException,
                            IOException

Constructs a ByteWiseFileAccessor object which maps a region of a data file into memory.

Parameters:

url - the data file

offset - the offset within the data file

length - the record length in bytes

records - the number of records

checkSize - check that the size of the data file is equal to the size of the table (length * records) + offset.

Throws:

FileNotFoundException - If file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading

IOException - If an I/O error occurs

ByteWiseFileAccessor

public ByteWiseFileAccessor(URL url,
                    long offset,
                    int length)
                     throws IOException

Constructor.

Parameters:

url - The data file.

offset - The offset within the data file.

Throws:

IOException - If an I/O error occurs.

Method Detail

readRecordBytes

public byte[] readRecordBytes(int recordNum,
                     int offset,
                     int length)

Reads length bytes of data from a specified record at the given offset.

Parameters:

recordNum - the record number to read bytes from (1-relative)

offset - an offset within the record

length - the number of bytes to read from the record

Returns:

an array of bytes

readByte

public byte readByte()

Reads a byte from the buffer.

Returns:

A byte.

mark

public void mark()

Marks the buffer.

reset

public void reset()

Resets the buffer.

hasRemaining

public boolean hasRemaining()

Checks to see if the buffer can still be read.

Returns:

'true' if there are more bytes to be read. 'false' otherwise.