Package com.drew.lang

Class RandomAccessFileReader

java.lang.Object

com.drew.lang.RandomAccessReader

com.drew.lang.RandomAccessFileReader

public class RandomAccessFileReader
extends RandomAccessReader

Provides methods to read specific values from a RandomAccessFile, with a consistent, checked exception structure for issues.

Field Summary

Fields

Modifier and Type	Field	Description
private int	_baseOffset
private int	_currentIndex
private java.io.RandomAccessFile	_file
private long	_length

Constructor Summary

Constructors

Constructor	Description
RandomAccessFileReader(java.io.RandomAccessFile file)
RandomAccessFileReader(java.io.RandomAccessFile file, int baseOffset)

Method Summary

Modifier and Type	Method	Description
byte	getByte(int index)	Gets the byte value at the specified byte index.
byte[]	getBytes(int index, int count)	Returns the required number of bytes from the specified index from the underlying source.
long	getLength()	Returns the length of the data source in bytes.
protected boolean	isValidIndex(int index, int bytesRequested)
private void	seek(int index)
int	toUnshiftedOffset(int localOffset)
protected void	validateIndex(int index, int bytesRequested)	Ensures that the buffered bytes extend to cover the specified index.

Methods inherited from class com.drew.lang.RandomAccessReader

getBit, getDouble64, getFloat32, getInt16, getInt24, getInt32, getInt64, getInt8, getNullTerminatedBytes, getNullTerminatedString, getNullTerminatedStringValue, getS15Fixed16, getString, getString, getStringValue, getUInt16, getUInt32, getUInt8, isMotorolaByteOrder, setMotorolaByteOrder

Methods inherited from class java.lang.Object

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

Field Detail

_file

private final java.io.RandomAccessFile _file

_length

private final long _length

_currentIndex

private int _currentIndex

_baseOffset

private final int _baseOffset

Constructor Detail

RandomAccessFileReader

public RandomAccessFileReader(java.io.RandomAccessFile file)
                       throws java.io.IOException

Throws:

java.io.IOException

RandomAccessFileReader

public RandomAccessFileReader(java.io.RandomAccessFile file,
                              int baseOffset)
                       throws java.io.IOException

Throws:

java.io.IOException

Method Detail

toUnshiftedOffset

public int toUnshiftedOffset(int localOffset)

Specified by:

toUnshiftedOffset in class RandomAccessReader

getLength

public long getLength()

Description copied from class: RandomAccessReader

Returns the length of the data source in bytes.

This is a simple operation for implementations (such as RandomAccessFileReader and ByteArrayReader) that have the entire data source available.

Users of this method must be aware that sequentially accessed implementations such as RandomAccessStreamReader will have to read and buffer the entire data source in order to determine the length.

Specified by:

getLength in class RandomAccessReader

Returns:

the length of the data source, in bytes.

getByte

public byte getByte(int index)
             throws java.io.IOException

Description copied from class: RandomAccessReader

Gets the byte value at the specified byte index.

Implementations should not perform any bounds checking in this method. That should be performed in validateIndex and isValidIndex.

Specified by:

getByte in class RandomAccessReader

Parameters:

index - The index from which to read the byte

Returns:

The read byte value

Throws:

BufferBoundsException - if the requested byte is beyond the end of the underlying data source

java.io.IOException - if the byte is unable to be read

getBytes

public byte[] getBytes(int index,
                       int count)
                throws java.io.IOException

Description copied from class: RandomAccessReader

Returns the required number of bytes from the specified index from the underlying source.

Specified by:

getBytes in class RandomAccessReader

Parameters:

index - The index from which the bytes begins in the underlying source

count - The number of bytes to be returned

Returns:

The requested bytes

Throws:

BufferBoundsException - if the requested bytes extend beyond the end of the underlying data source

java.io.IOException - if the byte is unable to be read

seek

private void seek(int index)
           throws java.io.IOException

Throws:

java.io.IOException

isValidIndex

protected boolean isValidIndex(int index,
                               int bytesRequested)
                        throws java.io.IOException

Specified by:

isValidIndex in class RandomAccessReader

Throws:

java.io.IOException

validateIndex

protected void validateIndex(int index,
                             int bytesRequested)
                      throws java.io.IOException

Description copied from class: RandomAccessReader

Ensures that the buffered bytes extend to cover the specified index. If not, an attempt is made to read to that point.

If the stream ends before the point is reached, a BufferBoundsException is raised.

Specified by:

validateIndex in class RandomAccessReader

Parameters:

index - the index from which the required bytes start

bytesRequested - the number of bytes which are required

Throws:

java.io.IOException - if the stream ends before the required number of bytes are acquired