public class CipherInputStream extends FilterInputStream
InputStream
and a cipher so that read()
methods return data that are read from the underlying InputStream
and
processed by the cipher.
The cipher must be initialized for the requested operation before being used
by a CipherInputStream
. For example, if a cipher initialized for
decryption is used with a CipherInputStream
, the CipherInputStream
tries to read the data an decrypt them before returning.
in
Modifier | Constructor and Description |
---|---|
protected |
CipherInputStream(InputStream is)
Creates a new
CipherInputStream instance for an InputStream without a cipher. |
|
CipherInputStream(InputStream is,
Cipher c)
Creates a new
CipherInputStream instance for an InputStream and a cipher. |
Modifier and Type | Method and Description |
---|---|
int |
available()
Returns an estimated number of bytes that can be read or skipped without blocking for more
input.
|
void |
close()
Closes this
CipherInputStream , also closes the underlying input
stream and call doFinal on the cipher object. |
boolean |
markSupported()
Returns whether this input stream supports
mark and
reset , which it does not. |
int |
read()
Reads the next byte from this cipher input stream.
|
int |
read(byte[] buf,
int off,
int len)
Reads the next
len bytes from this input stream into buffer
buf starting at offset off . |
long |
skip(long byteCount)
Skips
byteCount bytes in this stream. |
mark, reset
read
public CipherInputStream(InputStream is, Cipher c)
CipherInputStream
instance for an InputStream
and a cipher.
Warning: passing a null source creates an invalid
CipherInputStream
. All read operations on such a stream will
fail.
is
- the input stream to read data from.c
- the cipher to process the data with.protected CipherInputStream(InputStream is)
CipherInputStream
instance for an InputStream
without a cipher.
A NullCipher
is created and used to process the data.
is
- the input stream to read data from.public int read() throws IOException
read
in class FilterInputStream
-1
if the end of the stream is reached.IOException
- if an error occurs.public int read(byte[] buf, int off, int len) throws IOException
len
bytes from this input stream into buffer
buf
starting at offset off
.
if buf
is null
, the next len
bytes are read and
discarded.
read
in class FilterInputStream
buf
- the byte array in which to store the bytes read.off
- the initial position in buffer
to store the bytes
read from this stream.len
- the maximum number of bytes to store in buffer
.buf
, or -1
of the of the stream is reached.IOException
- if an error occurs.NullPointerException
- if the underlying input stream is null
.public long skip(long byteCount) throws IOException
FilterInputStream
byteCount
bytes in this stream. Subsequent
calls to read
will not return these bytes unless reset
is
used. This implementation skips byteCount
bytes in the
filtered stream.skip
in class FilterInputStream
byteCount
- the number of bytes to skip.IOException
- if this stream is closed or another IOException occurs.FilterInputStream.mark(int)
,
FilterInputStream.reset()
public int available() throws IOException
InputStream
Note that this method provides such a weak guarantee that it is not very useful in practice.
Firstly, the guarantee is "without blocking for more input" rather than "without blocking": a read may still block waiting for I/O to complete — the guarantee is merely that it won't have to wait indefinitely for data to be written. The result of this method should not be used as a license to do I/O on a thread that shouldn't be blocked.
Secondly, the result is a conservative estimate and may be significantly smaller than the actual number of bytes available. In particular, an implementation that always returns 0 would be correct. In general, callers should only use this method if they'd be satisfied with treating the result as a boolean yes or no answer to the question "is there definitely data ready?".
Thirdly, the fact that a given number of bytes is "available" does not guarantee that a read or skip will actually read or skip that many bytes: they may read or skip fewer.
It is particularly important to realize that you must not use this method to
size a container and assume that you can read the entirety of the stream without needing
to resize the container. Such callers should probably write everything they read to a
ByteArrayOutputStream
and convert that to a byte array. Alternatively, if you're
reading from a file, File.length()
returns the current length of the file (though
assuming the file's length can't change may be incorrect, reading a file is inherently
racy).
The default implementation of this method in InputStream
always returns 0.
Subclasses should override this method if they are able to indicate the number of bytes
available.
available
in class FilterInputStream
IOException
- if this stream is closed or an error occurspublic void close() throws IOException
CipherInputStream
, also closes the underlying input
stream and call doFinal
on the cipher object.close
in interface Closeable
close
in interface AutoCloseable
close
in class FilterInputStream
IOException
- if an error occurs.public boolean markSupported()
mark
and
reset
, which it does not.markSupported
in class FilterInputStream
mark
and
reset
.FilterInputStream.mark(int)
,
FilterInputStream.reset()
,
FilterInputStream.skip(long)