OpenJDK 1.22 · java.security.DigestInputStream · APIdia, the JavaDoc alternative

A transparent stream that updates the associated message digest using the bits going through the stream.

To complete the message digest computation, call one of the digest methods on the associated message digest after your calls to one of this digest input stream's read methods.

It is possible to turn this stream on or off (see on). When it is on, a call to one of the read methods results in an update on the message digest. But when it is off, the message digest is not updated. The default is for the stream to be on.

Note that digest objects can compute only one digest (see MessageDigest), so that in order to compute intermediate digests, a caller should retain a handle onto the digest object, and clone it for each digest to be computed, leaving the original digest untouched.

Implementation Note

This implementation only updates the message digest with data actually read from the input stream when it is turned on. This includes the various read methods, transferTo, readAllBytes, and readNBytes. Please note that data bypassed by the skip method are ignored. On the other hand, if the underlying stream supports the mark and reset methods, and the same data is read again after reset, then the message digest is updated again.

Modifier and Type	Field and Description
protected MessageDigest	digest The message digest associated with this stream.
private boolean	on

Constructor Summary

Access	Constructor and Description
public	DigestInputStream(InputStream the input stream. stream, MessageDigest the message digest to associate with this stream. digest) Creates a digest input stream, using the specified input stream and message digest.

Method Summary

Modifier and Type	Method and Description
public MessageDigest	Returns: the message digest associated with this stream. getMessageDigest() Returns the message digest associated with this stream.
public void	on(boolean `true` to turn the digest function on, `false` to turn it off. on) Turns the digest function on or off.
public int	Returns: the byte read. read() Overrides java.io.FilterInputStream.read. Reads a byte, and updates the message digest (if the digest function is on).
public int	Returns: the actual number of bytes read. This is less than `len` if the end of the stream is reached prior to reading `len` bytes. -1 is returned if no bytes were read because the end of the stream had already been reached when the call was made. read(byte[] the array into which the data is read. b, int the starting offset into `b` of where the data should be placed. off, int the maximum number of bytes to be read from the input stream into b, starting at offset `off`. len) Overrides java.io.FilterInputStream.read. Reads into a byte array, and updates the message digest (if the digest function is on).
public void	setMessageDigest(MessageDigest the message digest to be associated with this stream. digest) Associates the specified message digest with this stream.
public String	toString() Overrides java.lang.Object.toString. Prints a string representation of this digest input stream and its associated message digest object.

Inherited from java.io.FilterInputStream:: available close mark markSupported read reset skip

Field Detail

digest	back to summary
protected MessageDigest digest The message digest associated with this stream.

on	back to summary
private boolean on

Constructor Detail

DigestInputStream	back to summary
public DigestInputStream(InputStream stream, MessageDigest digest) Creates a digest input stream, using the specified input stream and message digest. Parameters stream:InputStream the input stream. digest:MessageDigest the message digest to associate with this stream.

DigestInputStream

back to summary

public DigestInputStream(InputStream stream, MessageDigest digest)

Creates a digest input stream, using the specified input stream and message digest.

Parameters

stream:InputStream: the input stream.
digest:MessageDigest: the message digest to associate with this stream.

Method Detail

getMessageDigest back to summary

getMessageDigest	back to summary
public MessageDigest getMessageDigest() Returns the message digest associated with this stream. Returns:MessageDigest the message digest associated with this stream. See Also `setMessageDigest(java.security.MessageDigest)`

public MessageDigest getMessageDigest()

Returns the message digest associated with this stream.

Returns:MessageDigest: the message digest associated with this stream.
See Also: setMessageDigest(java.security.MessageDigest)

on back to summary

on	back to summary
public void on(boolean on) Turns the digest function on or off. The default is on. When it is on, a call to one of the `read` methods results in an update on the message digest. But when it is off, the message digest is not updated. Parameters on:boolean `true` to turn the digest function on, `false` to turn it off.

public void on(boolean on)

Turns the digest function on or off. The default is on. When it is on, a call to one of the read methods results in an update on the message digest. But when it is off, the message digest is not updated.

Parameters

on:boolean: true to turn the digest function on, false to turn it off.

read back to summary

read	back to summary
public int read() throws IOException Overrides java.io.FilterInputStream.read. Reads a byte, and updates the message digest (if the digest function is on). That is, this method reads a byte from the input stream, blocking until the byte is actually read. If the digest function is on (see `on`), this method will then call `update` on the message digest associated with this stream, passing it the byte read. Returns:int the byte read. Exceptions IOException: if an I/O error occurs. See Also `MessageDigest#update(byte)`

public int read() throws IOException

Overrides java.io.FilterInputStream.read.

Reads a byte, and updates the message digest (if the digest function is on). That is, this method reads a byte from the input stream, blocking until the byte is actually read. If the digest function is on (see on), this method will then call update on the message digest associated with this stream, passing it the byte read.

Returns:int

the byte read.

Exceptions

IOException:: if an I/O error occurs.

See Also

MessageDigest#update(byte)

read back to summary

read	back to summary
public int read(byte[] b, int off, int len) throws IOException Overrides java.io.FilterInputStream.read. Reads into a byte array, and updates the message digest (if the digest function is on). That is, this method reads up to `len` bytes from the input stream into the array `b`, starting at offset `off`. This method blocks until the data is actually read. If the digest function is on (see `on`), this method will then call `update` on the message digest associated with this stream, passing it the data. Parameters b:byte[] the array into which the data is read. off:int the starting offset into `b` of where the data should be placed. len:int the maximum number of bytes to be read from the input stream into b, starting at offset `off`. Returns:int the actual number of bytes read. This is less than `len` if the end of the stream is reached prior to reading `len` bytes. -1 is returned if no bytes were read because the end of the stream had already been reached when the call was made. Exceptions IOException: if an I/O error occurs. See Also `MessageDigest#update(byte[], int, int)`

public int read(byte[] b, int off, int len) throws IOException

Overrides java.io.FilterInputStream.read.

Reads into a byte array, and updates the message digest (if the digest function is on). That is, this method reads up to len bytes from the input stream into the array b, starting at offset off. This method blocks until the data is actually read. If the digest function is on (see on), this method will then call update on the message digest associated with this stream, passing it the data.

Parameters

b:byte[]: the array into which the data is read.
off:int: the starting offset into b of where the data should be placed.
len:int: the maximum number of bytes to be read from the input stream into b, starting at offset off.

Returns:int

the actual number of bytes read. This is less than len if the end of the stream is reached prior to reading len bytes. -1 is returned if no bytes were read because the end of the stream had already been reached when the call was made.

Exceptions

IOException:: if an I/O error occurs.

setMessageDigest back to summary

setMessageDigest	back to summary
public void setMessageDigest(MessageDigest digest) Associates the specified message digest with this stream. Parameters digest:MessageDigest the message digest to be associated with this stream. See Also `getMessageDigest()`

public void setMessageDigest(MessageDigest digest)

Associates the specified message digest with this stream.

Parameters

digest:MessageDigest: the message digest to be associated with this stream.

See Also

getMessageDigest()

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Prints a string representation of this digest input stream and its associated message digest object. Returns:String Doc from java.lang.Object.toString. a string representation of the object

toString

back to summary

public String toString()

Overrides java.lang.Object.toString.

Prints a string representation of this digest input stream and its associated message digest object.

Returns:String

Doc from java.lang.Object.toString.

a string representation of the object

public Class DigestInputStream

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail