javax.crypto: public class: CipherInputStream

javax.crypto
public class: CipherInputStream [javadoc | source]

java.lang.Object
   java.io.InputStream
      java.io.FilterInputStream
         javax.crypto.CipherInputStream

All Implemented Interfaces:
Closeable

A CipherInputStream is composed of an InputStream and a Cipher so that read() methods return data that are read in from the underlying InputStream but have been additionally processed by the Cipher. The Cipher must be fully initialized before being used by a CipherInputStream.

For example, if the Cipher is initialized for decryption, the CipherInputStream will attempt to read in data and decrypt them, before returning the decrypted data.

This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.io.FilterInputStream and java.io.InputStream. This class has exactly those methods specified in its ancestor classes, and overrides them all. Moreover, this class catches all exceptions that are not thrown by its ancestor classes. In particular, the skip method skips, and the available method counts only data that have been processed by the encapsulated Cipher.

It is crucial for a programmer using this class not to use methods that are not defined or overriden in this class (such as a new method or constructor that is later added to one of the super classes), because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherInputStream.

Also see:

java.io.InputStream

java.io.FilterInputStream

javax.crypto.Cipher

javax.crypto.CipherOutputStream

author: Li - Gong

since: 1.4 -

Fields inherited from java.io.FilterInputStream:
in

Constructor:

Constructor:
protected CipherInputStream(InputStream is) { super(is); input = is; cipher = new NullCipher(); } Constructs a CipherInputStream from an InputStream without specifying a Cipher. This has the effect of constructing a CipherInputStream using a NullCipher. Note: if the specified input stream is null, a NullPointerException may be thrown later when it is used. Parameters: `is` - the to-be-processed input stream
public CipherInputStream(InputStream is, Cipher c) { super(is); input = is; cipher = c; } Constructs a CipherInputStream from an InputStream and a Cipher. Note: if the specified input stream or cipher is null, a NullPointerException may be thrown later when they are used. Parameters: `is` - the to-be-processed input stream `c` - an initialized Cipher object

 protected CipherInputStream(InputStream is) {
        super(is);
        input = is;
        cipher = new NullCipher();
}

Parameters:

is - the to-be-processed input stream

 public CipherInputStream(InputStream is,
    Cipher c) {
        super(is);
        input = is;
        cipher = c;
}

Parameters:

is - the to-be-processed input stream

c - an initialized Cipher object

Method from javax.crypto.CipherInputStream Summary:
available, close, markSupported, read, read, read, skip

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

Methods from java.io.InputStream:
available, close, mark, markSupported, read, read, read, reset, skip

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from javax.crypto.CipherInputStream Detail:
public int available() throws IOException { return (ofinish - ostart); } Returns the number of bytes that can be read from this input stream without blocking. The `available` method of `InputStream` returns `0`. This method should be overridden by subclasses.
public void close() throws IOException { input.close(); try { // throw away the unprocessed data cipher.doFinal(); } catch (BadPaddingException ex) { } catch (IllegalBlockSizeException ex) { } ostart = 0; ofinish = 0; } Closes this input stream and releases any system resources associated with the stream. The `close` method of `CipherInputStream` calls the `close` method of its underlying input stream.
public boolean markSupported() { return false; } Tests if this input stream supports the `mark` and `reset` methods, which it does not.
public int read() throws IOException { if (ostart >= ofinish) { // we loop for new data as the spec says we are blocking int i = 0; while (i == 0) i = getMoreData(); if (i == -1) return -1; } return ((int) obuffer[ostart++] & 0xff); } Reads the next byte of data from this input stream. The value byte is returned as an `int` in the range `0` to `255`. If no byte is available because the end of the stream has been reached, the value `-1` is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.
public int read(byte[] b) throws IOException { return read(b, 0, b.length); } Reads up to `b.length` bytes of data from this input stream into an array of bytes. The `read` method of `InputStream` calls the `read` method of three arguments with the arguments `b`, `0`, and `b.length`.
public int read(byte[] b, int off, int len) throws IOException { if (ostart >= ofinish) { // we loop for new data as the spec says we are blocking int i = 0; while (i == 0) i = getMoreData(); if (i == -1) return -1; } if (len < = 0) { return 0; } int available = ofinish - ostart; if (len < available) available = len; if (b != null) { System.arraycopy(obuffer, ostart, b, off, available); } ostart = ostart + available; return available; } Reads up to `len` bytes of data from this input stream into an array of bytes. This method blocks until some input is available. If the first argument is `null,` up to `len` bytes are read and discarded.
public long skip(long n) throws IOException { int available = ofinish - ostart; if (n > available) { n = available; } if (n < 0) { return 0; } ostart += n; return n; } Skips `n` bytes of input from the bytes that can be read from this input stream without blocking. Fewer bytes than requested might be skipped. The actual number of bytes skipped is equal to `n` or the result of a call to `available` , whichever is smaller. If `n` is less than zero, no bytes are skipped. The actual number of bytes skipped is returned.

Method from javax.crypto.CipherInputStream Detail:

 public int available() throws IOException {
        return (ofinish - ostart);
}

available

InputStream

0

should

 public  void close() throws IOException {
        input.close();
        try {
            // throw away the unprocessed data
            cipher.doFinal();
        }
        catch (BadPaddingException ex) {
        }
        catch (IllegalBlockSizeException ex) {
        }
        ostart = 0;
        ofinish = 0;
}

The close method of CipherInputStream calls the close method of its underlying input stream.

 public boolean markSupported() {
        return false;
}

mark

reset

 public int read() throws IOException {
        if (ostart  >= ofinish) {
            // we loop for new data as the spec says we are blocking
            int i = 0;
            while (i == 0) i = getMoreData();
            if (i == -1) return -1;
        }
        return ((int) obuffer[ostart++] & 0xff);
}

int

0

255

-1

 public int read(byte[] b) throws IOException {
        return read(b, 0, b.length);
}

b.length

The read method of InputStream calls the read method of three arguments with the arguments b, 0, and b.length.

 public int read(byte[] b,
    int off,
    int len) throws IOException {
        if (ostart  >= ofinish) {
            // we loop for new data as the spec says we are blocking
            int i = 0;
            while (i == 0) i = getMoreData();
            if (i == -1) return -1;
        }
        if (len < = 0) {
            return 0;
        }
        int available = ofinish - ostart;
        if (len <  available) available = len;
        if (b != null) {
            System.arraycopy(obuffer, ostart, b, off, available);
        }
        ostart = ostart + available;
        return available;
}

len

null,

len

 public long skip(long n) throws IOException {
        int available = ofinish - ostart;
        if (n  > available) {
            n = available;
        }
        if (n <  0) {
            return 0;
        }
        ostart += n;
        return n;
}

n

Fewer bytes than requested might be skipped. The actual number of bytes skipped is equal to n or the result of a call to available , whichever is smaller. If n is less than zero, no bytes are skipped.

The actual number of bytes skipped is returned.