open class DigestInputStream : FilterInputStream
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.
Summary
| Public constructors |
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Creates a digest input stream, using the specified input stream and message digest.
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| Public methods |
| open MessageDigest! |
Returns the message digest associated with this stream.
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| open Unit |
Turns the digest function on or off.
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| open Int |
Reads a byte, and updates the message digest (if the digest function is on).
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| open Int |
Reads into a byte array, and updates the message digest (if the digest function is on).
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| open Unit |
Associates the specified message digest with this stream.
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| open String |
Prints a string representation of this digest input stream and its associated message digest object.
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| Inherited functions |
From class FilterInputStream
Int |
available()
Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream. The next caller might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.
This method returns the result of in.available().
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Unit |
close()
Closes this input stream and releases any system resources associated with the stream. This method simply performs in.close().
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Unit |
mark(readlimit: Int)
Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.
The readlimit argument tells this input stream to allow that many bytes to be read before the mark position gets invalidated.
This method simply performs in.mark(readlimit).
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Boolean |
markSupported()
Tests if this input stream supports the mark and reset methods. This method simply performs in.markSupported().
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Int |
read(b: ByteArray!)
Reads up to b.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.
This method simply performs the call read(b, 0, b.length) and returns the result. It is important that it does not do in.read(b) instead; certain subclasses of FilterInputStream depend on the implementation strategy actually used.
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Unit |
reset()
Repositions this stream to the position at the time the mark method was last called on this input stream.
This method simply performs in.reset().
Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser.
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Long |
skip(n: Long)
Skips over and discards n bytes of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. The actual number of bytes skipped is returned.
This method simply performs in.skip(n).
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From class InputStream
InputStream! |
nullInputStream()
Returns a new InputStream that reads no bytes. The returned stream is initially open. The stream is closed by calling the close() method. Subsequent calls to close() have no effect.
While the stream is open, the available(), read(), read(byte[]), read(byte[], int, int), readAllBytes(), readNBytes(byte[], int, int), readNBytes(int), skip(long), skipNBytes(long), and transferTo() methods all behave as if end of stream has been reached. After the stream has been closed, these methods all throw IOException.
The markSupported() method returns false. The mark() method does nothing, and the reset() method throws IOException.
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ByteArray! |
readAllBytes()
Reads all remaining bytes from the input stream. This method blocks until all remaining bytes have been read and end of stream is detected, or an exception is thrown. This method does not close the input stream.
When this stream reaches end of stream, further invocations of this method will return an empty byte array.
Note that this method is intended for simple cases where it is convenient to read all bytes into a byte array. It is not intended for reading input streams with large amounts of data.
The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified.
If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
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ByteArray! |
readNBytes(len: Int)
Reads up to a specified number of bytes from the input stream. This method blocks until the requested number of bytes has been read, end of stream is detected, or an exception is thrown. This method does not close the input stream.
The length of the returned array equals the number of bytes read from the stream. If len is zero, then no bytes are read and an empty byte array is returned. Otherwise, up to len bytes are read from the stream. Fewer than len bytes may be read if end of stream is encountered.
When this stream reaches end of stream, further invocations of this method will return an empty byte array.
Note that this method is intended for simple cases where it is convenient to read the specified number of bytes into a byte array. The total amount of memory allocated by this method is proportional to the number of bytes read from the stream which is bounded by len. Therefore, the method may be safely called with very large values of len provided sufficient memory is available.
The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified.
If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
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Int |
readNBytes(b: ByteArray!, off: Int, len: Int)
Reads the requested number of bytes from the input stream into the given byte array. This method blocks until len bytes of input data have been read, end of stream is detected, or an exception is thrown. The number of bytes actually read, possibly zero, is returned. This method does not close the input stream.
In the case where end of stream is reached before len bytes have been read, then the actual number of bytes read will be returned. When this stream reaches end of stream, further invocations of this method will return zero.
If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read up to len bytes.
The first byte read is stored into element b[off], the next one in to b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k ] through b[off+len-1] unaffected.
The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified.
If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes of b have been updated with data from the input stream. Consequently the input stream and b may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
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Unit |
skipNBytes(n: Long)
Skips over and discards exactly n bytes of data from this input stream. If n is zero, then no bytes are skipped. If n is negative, then no bytes are skipped. Subclasses may handle the negative value differently.
This method blocks until the requested number of bytes has been skipped, end of file is reached, or an exception is thrown.
If end of stream is reached before the stream is at the desired position, then an EOFException is thrown.
If an I/O error occurs, then the input stream may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
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Long |
transferTo(out: OutputStream!)
Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read. On return, this input stream will be at end of stream. This method does not close either stream.
This method may block indefinitely reading from the input stream, or writing to the output stream. The behavior for the case where the input and/or output stream is asynchronously closed, or the thread interrupted during the transfer, is highly input and output stream specific, and therefore not specified.
If an I/O error occurs reading from the input stream or writing to the output stream, then it may do so after some bytes have been read or written. Consequently the input stream may not be at end of stream and one, or both, streams may be in an inconsistent state. It is strongly recommended that both streams be promptly closed if an I/O error occurs.
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| Properties |
| MessageDigest! |
The message digest associated with this stream.
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Public constructors
DigestInputStream(
stream: InputStream!,
digest: MessageDigest!)
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. |
Public methods
getMessageDigest
open fun getMessageDigest(): MessageDigest!
Returns the message digest associated with this stream.
| Return |
MessageDigest! |
the message digest associated with this stream. |
on
open fun on(on: Boolean): Unit
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
open fun read(): Int
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.
| Return |
Int |
the byte read. |
| Exceptions |
java.io.IOException |
if an I/O error occurs. |
java.io.IOException |
if an I/O error occurs. |
read
open fun read(
b: ByteArray!,
off: Int,
len: Int
): Int
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 |
ByteArray!: 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. |
| Return |
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 |
java.io.IOException |
If the first byte cannot be read for any reason other than end of file, or if the input stream has been closed, or if some other I/O error occurs. |
java.lang.NullPointerException |
If b is null. |
java.lang.IndexOutOfBoundsException |
If off is negative, len is negative, or len is greater than b.length - off |
java.io.IOException |
if an I/O error occurs. |
setMessageDigest
open fun setMessageDigest(digest: MessageDigest!): Unit
Associates the specified message digest with this stream.
| Parameters |
digest |
MessageDigest!: the message digest to be associated with this stream. |
toString
open fun toString(): String
Prints a string representation of this digest input stream and its associated message digest object.
| Return |
String |
a string representation of the object. |
Properties
digest
protected var digest: MessageDigest!
The message digest associated with this stream.
