Package java.util.zip

Class CheckedInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

java.util.zip.CheckedInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class CheckedInputStream
extends FilterInputStream

The CheckedInputStream class is used to maintain a checksum at the same time as the data, on which the checksum is computed, is read from a stream. The purpose of this checksum is to establish data integrity, comparing the computed checksum against a published checksum value.

Field Summary

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

Constructors

Constructor	Description
CheckedInputStream(InputStream is, Checksum csum)	Constructs a new CheckedInputStream on InputStream is.

Method Summary

Modifier and Type	Method	Description
Checksum	getChecksum()	Returns the checksum calculated on the stream read so far.
int	read()	Reads one byte of data from the underlying input stream and updates the checksum with the byte data.
int	read(byte[] buffer, int byteOffset, int byteCount)	Reads up to byteCount bytes of data from the underlying input stream, storing it into buffer, starting at offset byteOffset.
long	skip(long byteCount)	Skip up to byteCount bytes of data on the underlying input stream.

Methods inherited from class java.io.FilterInputStream

available, close, mark, markSupported, reset

Methods inherited from class java.io.InputStream

read

Methods inherited from class java.lang.Object

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

Constructor Detail

CheckedInputStream

public CheckedInputStream(InputStream is,
                          Checksum csum)

Constructs a new CheckedInputStream on InputStream is. The checksum will be calculated using the algorithm implemented by csum.

Warning: passing a null source creates an invalid CheckedInputStream. All operations on such a stream will fail.

Parameters:

is - the input stream to calculate checksum from.

csum - an entity implementing the checksum algorithm.

Method Detail

read

public int read()
         throws IOException

Reads one byte of data from the underlying input stream and updates the checksum with the byte data.

Overrides:

read in class FilterInputStream

Returns:

-1 at the end of the stream, a single byte value otherwise.

Throws:

IOException - if an IOException occurs.

read

public int read(byte[] buffer,
                int byteOffset,
                int byteCount)
         throws IOException

Reads up to byteCount bytes of data from the underlying input stream, storing it into buffer, starting at offset byteOffset. The checksum is updated with the bytes read. Returns the number of bytes actually read or -1 if arrived at the end of the filtered stream while reading the data.

Overrides:

read in class FilterInputStream

Throws:

IOException - if this stream is closed or some I/O error occurs.

getChecksum

public Checksum getChecksum()

Returns the checksum calculated on the stream read so far.

skip

public long skip(long byteCount)
          throws IOException

Skip up to byteCount bytes of data on the underlying input stream. Any skipped bytes are added to the running checksum value.

Overrides:

skip in class FilterInputStream

Parameters:

byteCount - the number of bytes to skip.

Returns:

the number of bytes skipped.

Throws:

IOException - if this stream is closed or another I/O error occurs.

See Also:

FilterInputStream.mark(int), FilterInputStream.reset()