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, resetreadpublic 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 FilterInputStreambuf - 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
FilterInputStreambyteCount 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 FilterInputStreambyteCount - 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
InputStreamNote 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 FilterInputStreamIOException - 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 Closeableclose in interface AutoCloseableclose in class FilterInputStreamIOException - if an error occurs.public boolean markSupported()
mark and
reset, which it does not.markSupported in class FilterInputStreammark and
reset.FilterInputStream.mark(int),
FilterInputStream.reset(),
FilterInputStream.skip(long)