Package javax.crypto

Class CipherInputStream

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    public class CipherInputStream
extends FilterInputStream
    This class wraps an 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.

    • Constructor Detail

      • CipherInputStream

        public CipherInputStream​(InputStream is,
                         Cipher c)
        Creates a new 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.

        Parameters:
        is - the input stream to read data from.
        c - the cipher to process the data with.

      • CipherInputStream

        protected CipherInputStream​(InputStream is)
        Creates a new CipherInputStream instance for an InputStream without a cipher.

        A NullCipher is created and used to process the data.

        Parameters:
        is - the input stream to read data from.

    • Method Detail

      • read

        public int read()
         throws IOException
        Reads the next byte from this cipher input stream.
        Overrides:
        read in class FilterInputStream
        Returns:
        the next byte, or -1 if the end of the stream is reached.
        Throws:
        IOException - if an error occurs.

      • read

        public int read​(byte[] buf,
                int off,
                int len)
         throws IOException
        Reads the next 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.

        Overrides:
        read in class FilterInputStream
        Returns:
        the number of bytes filled into buffer buf, or -1 of the of the stream is reached.
        Throws:
        IOException - if an error occurs.
        NullPointerException - if the underlying input stream is null.

      • available

        public int available()
              throws IOException
        Description copied from class: InputStream
        Returns an estimated number of bytes that can be read or skipped without blocking for more input.

        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.

        Overrides:
        available in class FilterInputStream
        Returns:
        the estimated number of bytes available
        Throws:
        IOException - if this stream is closed or an error occurs