FilterInputStream buffers input from an
- * underlying implementation to provide a possibly more efficient read
- * mechanism. It maintains the buffer and buffer state in instance
- * variables that are available to subclasses. The default buffer size
- * of 2048 bytes can be overridden by the creator of the stream.
- *
- * This class also implements mark/reset functionality. It is capable
- * of remembering any number of input bytes, to the limits of
- * system memory or the size of Integer.MAX_VALUE
- *
- * Please note that this class does not properly handle character
- * encodings. Consider using the
- * The number of available bytes will be the number of read ahead bytes
- * stored in the internal buffer plus the number of available bytes in
- * the underlying stream.
- *
- * @return The number of bytes that can be read before blocking could occur
- *
- * @exception IOException If an error occurs
- */
- public synchronized int available() throws IOException
- {
- return count - pos + super.available();
- }
-
- /**
- * This method closes the underlying input stream and frees any
- * resources associated with it. Sets
- * Note that the number of bytes that can be remembered by this method
- * can be greater than the size of the internal read buffer. It is also
- * not dependent on the subordinate stream supporting mark/reset
- * functionality.
- *
- * @param readlimit The number of bytes that can be read before the mark
- * becomes invalid
- */
- public synchronized void mark(int readlimit)
- {
- marklimit = readlimit;
- markpos = pos;
- }
-
- /**
- * This method returns
- * This method will block until the byte can be read.
- *
- * @return The byte read or -1 if end of stream
- *
- * @exception IOException If an error occurs
- */
- public synchronized int read() throws IOException
- {
- if (pos >= count && !refill())
- return -1; // EOF
-
- if (markpos >= 0 && pos - markpos > marklimit)
- markpos = -1;
-
- return ((int) buf[pos++]) & 0xFF;
- }
-
- /**
- * This method reads bytes from a stream and stores them into a caller
- * supplied buffer. It starts storing the data at index
- * This method will block until some data can be read.
- *
- * @param b The array into which the bytes read should be stored
- * @param off The offset into the array to start storing bytes
- * @param len The requested number of bytes to read
- *
- * @return The actual number of bytes read, or -1 if end of stream.
- *
- * @exception IOException If an error occurs.
- * @exception IndexOutOfBoundsException when
- * This method will throw an IOException if the number of bytes read from
- * the stream since the call to BufferedReader class which
- * does.
- *
- * @author Aaron M. Renn (arenn@urbanophile.com)
- * @author Warren Levy pos == count, the buffer is empty.
- */
- protected int pos = 0;
-
- /**
- * The value of pos when the mark() method was
- * called.
- * This is set to -1 if there is no mark set.
- */
- protected int markpos = -1;
-
- /**
- * This is the maximum number of bytes than can be read after a
- * call to mark() before the mark can be discarded.
- * After this may bytes are read, the reset() method
- * may not be called successfully.
- */
- protected int marklimit = 0;
-
- /**
- * This method initializes a new BufferedInputStream that will
- * read from the specified subordinate stream with a default buffer size
- * of 2048 bytes
- *
- * @param in The subordinate stream to read from
- */
- public BufferedInputStream(InputStream in)
- {
- this(in, DEFAULT_BUFFER_SIZE);
- }
-
- /**
- * This method initializes a new BufferedInputStream that will
- * read from the specified subordinate stream with a buffer size that
- * is specified by the caller.
- *
- * @param in The subordinate stream to read from
- * @param size The buffer size to use
- *
- * @exception IllegalArgumentException when size is smaller then 1
- */
- public BufferedInputStream(InputStream in, int size)
- {
- super(in);
- if (size <= 0)
- throw new IllegalArgumentException();
- buf = new byte[size];
- }
-
- /**
- * This method returns the number of bytes that can be read from this
- * stream before a read can block. A return of 0 indicates that blocking
- * might (or might not) occur on the very next read attempt.
- * buf to null.
- *
- * @exception IOException If an error occurs.
- */
- public void close() throws IOException
- {
- // Free up the array memory.
- buf = null;
- super.close();
- }
-
- /**
- * This method marks a position in the input to which the stream can be
- * "reset" by calling the reset() method. The parameter
- * readlimit is the number of bytes that can be read from the
- * stream after setting the mark before the mark becomes invalid. For
- * example, if mark() is called with a read limit of 10, then
- * when 11 bytes of data are read from the stream before the
- * reset() method is called, then the mark is invalid and the
- * stream object instance is not required to remember the mark.
- * true to indicate that this class
- * supports mark/reset functionality.
- *
- * @return true to indicate that mark/reset functionality is
- * supported
- *
- */
- public boolean markSupported()
- {
- return true;
- }
-
- /**
- * This method reads an unsigned byte from the input stream and returns it
- * as an int in the range of 0-255. This method also will return -1 if
- * the end of the stream has been reached.
- * off
- * into the buffer and attempts to read len bytes. This method
- * can return before reading the number of bytes requested. The actual
- * number of bytes read is returned as an int. A -1 is returned to indicate
- * the end of the stream.
- * off or
- * len are negative, or when off + len
- * is larger then the size of b,
- */
- public synchronized int read(byte[] b, int off, int len) throws IOException
- {
- if (off < 0 || len < 0 || off + len > b.length)
- throw new IndexOutOfBoundsException();
-
- if (pos >= count && !refill())
- return -1; // No bytes were read before EOF.
-
- int remain = Math.min(count - pos, len);
- System.arraycopy(buf, pos, b, off, remain);
- pos += remain;
-
- if (markpos >= 0 && pos - markpos > marklimit)
- markpos = -1;
-
- return remain;
- }
-
- /**
- * This method resets a stream to the point where the mark()
- * method was called. Any bytes that were read after the mark point was
- * set will be re-read during subsequent reads.
- * mark() exceeds the mark limit
- * passed when establishing the mark.
- *
- * @exception IOException If mark() was never called or more
- * then markLimit bytes were read since the last
- * call to mark()
- */
- public synchronized void reset() throws IOException
- {
- if (markpos < 0)
- throw new IOException();
-
- pos = markpos;
- }
-
- /**
- * This method skips the specified number of bytes in the stream. It
- * returns the actual number of bytes skipped, which may be less than the
- * requested amount.
- *
- * @param n The requested number of bytes to skip
- *
- * @return The actual number of bytes skipped.
- *
- * @exception IOException If an error occurs
- */
- public synchronized long skip(long n) throws IOException
- {
- final long origN = n;
-
- while (n > 0L)
- {
- if (pos >= count && !refill())
- if (n < origN)
- break;
- else
- return -1; // No bytes were read before EOF.
-
- int numread = (int) Math.min((long) (count - pos), n);
- pos += numread;
- n -= numread;
-
- if (markpos >= 0 && pos - markpos > marklimit)
- markpos = -1;
- }
-
- return origN - n;
- }
-
- /**
- * Called to refill the buffer (when count is equal or greater the pos).
- * Package local so BufferedReader can call it when needed.
- *
- * @return true when buf can be (partly) refilled,
- * false otherwise.
- */
- boolean refill() throws IOException
- {
- if (markpos < 0)
- count = pos = 0;
- else if (markpos > 0)
- {
- // Shift the marked bytes (if any) to the beginning of the array
- // but don't grow it. This saves space in case a reset is done
- // before we reach the max capacity of this array.
- System.arraycopy(buf, markpos, buf, 0, count - markpos);
- count -= markpos;
- pos -= markpos;
- markpos = 0;
- }
- else if (marklimit >= buf.length) // BTW, markpos == 0
- {
- // Need to grow the buffer now to have room for marklimit bytes.
- // Note that the new buffer is one greater than marklimit.
- // This is so that there will be one byte past marklimit to be read
- // before having to call refill again, thus allowing marklimit to be
- // invalidated. That way refill doesn't have to check marklimit.
- byte[] newbuf = new byte[marklimit + 1];
- System.arraycopy(buf, 0, newbuf, 0, count);
- buf = newbuf;
- }
-
- int numread = super.read(buf, count, buf.length - count);
-
- if (numread < 0) // EOF
- return false;
-
- count += numread;
- return true;
- }
-}