inputstreamsource.java

html 解析处理代码

            }
            else
            {
                if (mBuffer != buffer)
                {   // copy the bytes previously read
                    System.arraycopy (mBuffer, 0, buffer, 0, mLevel);
                    mBuffer = buffer;
                }
                mLevel += read;
            }
            // todo, should repeat on read shorter than original min
        }
    }

    //
    // Reader overrides
    //

    /**
     * Does nothing.
     * It's supposed to close the source, but use destroy() instead.
     * @exception IOException <em>not used</em>
     * @see #destroy
     */
    public void close () throws IOException
    {
    }

    /**
     * Read a single character.
     * This method will block until a character is available,
     * an I/O error occurs, or the end of the stream is reached.
     * @return The character read, as an integer in the range 0 to 65535
     * (<tt>0x00-0xffff</tt>), or {@link #EOF EOF} if the end of the stream has
     * been reached
     * @exception IOException If an I/O error occurs.
     */
    public int read () throws IOException
    {
        int ret;

        if (mLevel - mOffset < 1)
        {
            if (null == mStream)
                throw new IOException ("source is closed");
            fill (1);
            if (mOffset >= mLevel)
                ret = EOF;
            else
                ret = mBuffer[mOffset++];
        }
        else
            ret = mBuffer[mOffset++];

        return (ret);
    }

    /**
     * Read characters into a portion of an array.  This method will block
     * until some input is available, an I/O error occurs, or the end of the
     * stream is reached.
     * @param cbuf Destination buffer
     * @param off Offset at which to start storing characters
     * @param len Maximum number of characters to read
     * @return The number of characters read, or {@link #EOF EOF} if the end of
     * the stream has been reached
     * @exception IOException If an I/O error occurs.
     */
    public int read (char[] cbuf, int off, int len) throws IOException
    {
        int ret;

        if (null == mStream)
            throw new IOException ("source is closed");
        if ((null == cbuf) || (0 > off) || (0 > len))
            throw new IOException ("illegal argument read ("
                + ((null == cbuf) ? "null" : "cbuf")
                + ", " + off + ", " + len + ")");
        if (mLevel - mOffset < len)
            fill (len - (mLevel - mOffset)); // minimum to satisfy this request
        if (mOffset >= mLevel)
            ret = EOF;
        else
        {
            ret = Math.min (mLevel - mOffset, len);
            System.arraycopy (mBuffer, mOffset, cbuf, off, ret);
            mOffset += ret;
        }

        return (ret);
    }

    /**
     * Read characters into an array.
     * This method will block until some input is available, an I/O error occurs,
     * or the end of the stream is reached.
     * @param cbuf Destination buffer.
     * @return The number of characters read, or {@link #EOF EOF} if the end of
     * the stream has been reached.
     * @exception IOException If an I/O error occurs.
     */
    public int read (char[] cbuf) throws IOException
    {
        return (read (cbuf, 0, cbuf.length));
    }

    /**
     * Reset the source.
     * Repositions the read point to begin at zero.
     * @exception IllegalStateException If the source has been closed.
     */
    public void reset ()
        throws
            IllegalStateException
    {
        if (null == mStream)
            throw new IllegalStateException ("source is closed");
        if (-1 != mMark)
            mOffset = mMark;
        else
            mOffset = 0;
    }

    /**
     * Tell whether this source supports the mark() operation.
     * @return <code>true</code>.
     */
    public boolean markSupported ()
    {
        return (true);
    }

    /**
     * Mark the present position in the source.
     * Subsequent calls to {@link #reset()}
     * will attempt to reposition the source to this point.
     * @param  readAheadLimit <em>Not used.</em>
     * @exception IOException If the source is closed.
     *
     */
    public void mark (int readAheadLimit) throws IOException
    {
        if (null == mStream)
            throw new IOException ("source is closed");
        mMark = mOffset;
    }

    /**
     * Tell whether this source is ready to be read.
     * @return <code>true</code> if the next read() is guaranteed not to block
     * for input, <code>false</code> otherwise.
     * Note that returning false does not guarantee that the next read will block.
     * @exception IOException If the source is closed.
     */
    public boolean ready () throws IOException
    {
        if (null == mStream)
            throw new IOException ("source is closed");
        return (mOffset < mLevel);
    }

    /**
     * Skip characters.
     * This method will block until some characters are available,
     * an I/O error occurs, or the end of the stream is reached.
     * <em>Note: n is treated as an int</em>
     * @param n The number of characters to skip.
     * @return The number of characters actually skipped
     * @exception IllegalArgumentException If <code>n</code> is negative.
     * @exception IOException If an I/O error occurs.
     */
    public long skip (long n)
        throws
            IOException,
            IllegalArgumentException
    {
        long ret;

        if (null == mStream)
            throw new IOException ("source is closed");
        if (0 > n)
            throw new IllegalArgumentException ("cannot skip backwards");
        else
        {
            if (mLevel - mOffset < n)
                fill ((int)(n - (mLevel - mOffset))); // minimum to satisfy this request
            if (mOffset >= mLevel)
                ret = EOF;
            else
            {
                ret = Math.min (mLevel - mOffset, n);
                mOffset += ret;
            }
        }

        return (ret);
    }

    //
    // Methods not in your Daddy's Reader
    //

    /**
     * Undo the read of a single character.
     * @exception IOException If the source is closed or no characters have
     * been read.
     */
    public void unread () throws IOException
    {
        if (null == mStream)
            throw new IOException ("source is closed");
        if (0 < mOffset)
            mOffset--;
        else
            throw new IOException ("can't unread no characters");
    }

    /**
     * Retrieve a character again.
     * @param offset The offset of the character.
     * @return The character at <code>offset</code>.
     * @exception IOException If the offset is beyond {@link #offset()} or the
     * source is closed.
     */
    public char getCharacter (int offset) throws IOException
    {
        char ret;

        if (null == mStream)
            throw new IOException ("source is closed");
        if (offset >= mBuffer.length)
            throw new IOException ("illegal read ahead");
        else
            ret = mBuffer[offset];
        
        return (ret);
    }

    /**
     * Retrieve characters again.
     * @param array The array of characters.
     * @param offset The starting position in the array where characters are to be placed.
     * @param start The starting position, zero based.
     * @param end The ending position
     * (exclusive, i.e. the character at the ending position is not included),
     * zero based.
     * @exception IOException If the start or end is beyond {@link #offset()}
     * or the source is closed.
     */
    public void getCharacters (char[] array, int offset, int start, int end) throws IOException
    {
        if (null == mStream)
            throw new IOException ("source is closed");
        System.arraycopy (mBuffer, start, array, offset, end - start);
    }
    
    /**
     * Retrieve a string.
     * @param offset The offset of the first character.
     * @param length The number of characters to retrieve.
     * @return A string containing the <code>length</code> characters at <code>offset</code>.
     * @exception IOException If the offset or (offset + length) is beyond
     * {@link #offset()} or the source is closed.
     */
    public String getString (int offset, int length) throws IOException
    {
        String ret;

        if (null == mStream)
            throw new IOException ("source is closed");
        if (offset + length > mBuffer.length)
            throw new IOException ("illegal read ahead");
        else
            ret = new String (mBuffer, offset, length);
        
        return (ret);
    }

    /**
     * Append characters already read into a <code>StringBuffer</code>.
     * @param buffer The buffer to append to.
     * @param offset The offset of the first character.
     * @param length The number of characters to retrieve.
     * @exception IOException If the offset or (offset + length) is beyond
     * {@link #offset()} or the source is closed.
     */
    public void getCharacters (StringBuffer buffer, int offset, int length) throws IOException
    {
        if (null == mStream)
            throw new IOException ("source is closed");
        buffer.append (mBuffer, offset, length);
    }

    /**
     * Close the source.
     * Once a source has been closed, further {@link #read() read},
     * {@link #ready ready}, {@link #mark mark}, {@link #reset reset},
     * {@link #skip skip}, {@link #unread unread},
     * {@link #getCharacter getCharacter} or {@link #getString getString}
     * invocations will throw an IOException.
     * Closing a previously-closed source, however, has no effect.
     * @exception IOException If an I/O error occurs
     */
    public void destroy () throws IOException
    {
        mStream = null;
        if (null != mReader)
            mReader.close ();
        mReader = null;
        mBuffer = null;
        mLevel = 0;
        mOffset = 0;
        mMark = -1;
    }

    /**
     * Get the position (in characters).
     * @return The number of characters that have already been read, or
     * {@link #EOF EOF} if the source is closed.
     */
    public int offset ()
    {
        int ret;

        if (null == mStream)
            ret = EOF;
        else
            ret = mOffset;

        return (ret);
    }

    /**
     * Get the number of available characters.
     * @return The number of characters that can be read without blocking or
     * zero if the source is closed.
     */
    public int available ()
    {
        int ret;

        if (null == mStream)
            ret = 0;
        else
            ret = mLevel - mOffset;

        return (ret);
    }
}