bytechunk.java

业界著名的tomcat服务器的最新6.0的源代码。

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.util.buf;

import java.io.IOException;
import java.io.Serializable;

/*
 * In a server it is very important to be able to operate on
 * the original byte[] without converting everything to chars.
 * Some protocols are ASCII only, and some allow different
 * non-UNICODE encodings. The encoding is not known beforehand,
 * and can even change during the execution of the protocol.
 * ( for example a multipart message may have parts with different
 *  encoding )
 *
 * For HTTP it is not very clear how the encoding of RequestURI
 * and mime values can be determined, but it is a great advantage
 * to be able to parse the request without converting to string.
 */

// TODO: This class could either extend ByteBuffer, or better a ByteBuffer inside
// this way it could provide the search/etc on ByteBuffer, as a helper.

/**
 * This class is used to represent a chunk of bytes, and
 * utilities to manipulate byte[].
 *
 * The buffer can be modified and used for both input and output.
 *
 * There are 2 modes: The chunk can be associated with a sink - ByteInputChannel or ByteOutputChannel,
 * which will be used when the buffer is empty ( on input ) or filled ( on output ).
 * For output, it can also grow. This operating mode is selected by calling setLimit() or
 * allocate(initial, limit) with limit != -1.
 *
 * Various search and append method are defined - similar with String and StringBuffer, but
 * operating on bytes.
 *
 * This is important because it allows processing the http headers directly on the received bytes,
 * without converting to chars and Strings until the strings are needed. In addition, the charset
 * is determined later, from headers or user code.
 *
 *
 * @author [e-mail]
 * @author James Todd [[e-mail]]
 * @author Costin Manolache
 * @author Remy Maucherat
 */
public final class ByteChunk implements Cloneable, Serializable {

    /** Input interface, used when the buffer is emptiy
     *
     * Same as java.nio.channel.ReadableByteChannel
     */
    public static interface ByteInputChannel {
        /** 
         * Read new bytes ( usually the internal conversion buffer ).
         * The implementation is allowed to ignore the parameters, 
         * and mutate the chunk if it wishes to implement its own buffering.
         */
        public int realReadBytes(byte cbuf[], int off, int len)
            throws IOException;
    }

    /** Same as java.nio.channel.WrittableByteChannel.
     */
    public static interface ByteOutputChannel {
        /** 
         * Send the bytes ( usually the internal conversion buffer ).
         * Expect 8k output if the buffer is full.
         */
        public void realWriteBytes(byte cbuf[], int off, int len)
            throws IOException;
    }

    // --------------------

    /** Default encoding used to convert to strings. It should be UTF8,
	as most standards seem to converge, but the servlet API requires
	8859_1, and this object is used mostly for servlets. 
    */
    public static final String DEFAULT_CHARACTER_ENCODING="ISO-8859-1";
        
    // byte[]
    private byte[] buff;

    private int start=0;
    private int end;

    private String enc;

    private boolean isSet=false; // XXX

    // How much can it grow, when data is added
    private int limit=-1;

    private ByteInputChannel in = null;
    private ByteOutputChannel out = null;

    private boolean isOutput=false;
    private boolean optimizedWrite=true;
    
    /**
     * Creates a new, uninitialized ByteChunk object.
     */
    public ByteChunk() {
    }

    public ByteChunk( int initial ) {
	allocate( initial, -1 );
    }

    //--------------------
    public ByteChunk getClone() {
	try {
	    return (ByteChunk)this.clone();
	} catch( Exception ex) {
	    return null;
	}
    }

    public boolean isNull() {
	return ! isSet; // buff==null;
    }
    
    /**
     * Resets the message buff to an uninitialized state.
     */
    public void recycle() {
	//	buff = null;
	enc=null;
	start=0;
	end=0;
	isSet=false;
    }

    public void reset() {
	buff=null;
    }

    // -------------------- Setup --------------------

    public void allocate( int initial, int limit  ) {
	isOutput=true;
	if( buff==null || buff.length < initial ) {
	    buff=new byte[initial];
	}    
	this.limit=limit;
	start=0;
	end=0;
	isSet=true;
    }

    /**
     * Sets the message bytes to the specified subarray of bytes.
     * 
     * @param b the ascii bytes
     * @param off the start offset of the bytes
     * @param len the length of the bytes
     */
    public void setBytes(byte[] b, int off, int len) {
        buff = b;
        start = off;
        end = start+ len;
        isSet=true;
    }

    public void setOptimizedWrite(boolean optimizedWrite) {
        this.optimizedWrite = optimizedWrite;
    }

    public void setEncoding( String enc ) {
	this.enc=enc;
    }
    public String getEncoding() {
        if (enc == null)
            enc=DEFAULT_CHARACTER_ENCODING;
        return enc;
    }

    /**
     * Returns the message bytes.
     */
    public byte[] getBytes() {
	return getBuffer();
    }

    /**
     * Returns the message bytes.
     */
    public byte[] getBuffer() {
	return buff;
    }

    /**
     * Returns the start offset of the bytes.
     * For output this is the end of the buffer.
     */
    public int getStart() {
	return start;
    }

    public int getOffset() {
	return start;
    }

    public void setOffset(int off) {
        if (end < off ) end=off;
	start=off;
    }

    /**
     * Returns the length of the bytes.
     * XXX need to clean this up
     */
    public int getLength() {
	return end-start;
    }

    /** Maximum amount of data in this buffer.
     *
     *  If -1 or not set, the buffer will grow undefinitely.
     *  Can be smaller than the current buffer size ( which will not shrink ).
     *  When the limit is reached, the buffer will be flushed ( if out is set )
     *  or throw exception.
     */
    public void setLimit(int limit) {
	this.limit=limit;
    }
    
    public int getLimit() {
	return limit;
    }

    /**
     * When the buffer is empty, read the data from the input channel.
     */
    public void setByteInputChannel(ByteInputChannel in) {
        this.in = in;
    }

    /** When the buffer is full, write the data to the output channel.
     * 	Also used when large amount of data is appended.
     *
     *  If not set, the buffer will grow to the limit.
     */
    public void setByteOutputChannel(ByteOutputChannel out) {
	this.out=out;
    }

    public int getEnd() {
	return end;
    }

    public void setEnd( int i ) {
	end=i;
    }

    // -------------------- Adding data to the buffer --------------------
    /** Append a char, by casting it to byte. This IS NOT intended for unicode.
     *
     * @param c
     * @throws IOException
     */
    public void append( char c )
	throws IOException
    {
	append( (byte)c);
    }

    public void append( byte b )
	throws IOException
    {
	makeSpace( 1 );

	// couldn't make space
	if( limit >0 && end >= limit ) {
	    flushBuffer();
	}
	buff[end++]=b;
    }

    public void append( ByteChunk src )
	throws IOException
    {
	append( src.getBytes(), src.getStart(), src.getLength());
    }

    /** Add data to the buffer
     */
    public void append( byte src[], int off, int len )
	throws IOException
    {
	// will grow, up to limit
	makeSpace( len );

	// if we don't have limit: makeSpace can grow as it wants
	if( limit < 0 ) {
	    // assert: makeSpace made enough space
	    System.arraycopy( src, off, buff, end, len );
	    end+=len;
	    return;
	}

        // Optimize on a common case.
        // If the buffer is empty and the source is going to fill up all the
        // space in buffer, may as well write it directly to the output,
        // and avoid an extra copy
        if ( optimizedWrite && len == limit && end == start && out != null ) {
            out.realWriteBytes( src, off, len );
            return;
        }
	// if we have limit and we're below
	if( len <= limit - end ) {
	    // makeSpace will grow the buffer to the limit,
	    // so we have space
	    System.arraycopy( src, off, buff, end, len );
	    end+=len;
	    return;
	}

	// need more space than we can afford, need to flush
	// buffer

	// the buffer is already at ( or bigger than ) limit

        // We chunk the data into slices fitting in the buffer limit, although
        // if the data is written directly if it doesn't fit

        int avail=limit-end;
        System.arraycopy(src, off, buff, end, avail);
        end += avail;

        flushBuffer();

        int remain = len - avail;

        while (remain > (limit - end)) {
            out.realWriteBytes( src, (off + len) - remain, limit - end );
            remain = remain - (limit - end);
        }

        System.arraycopy(src, (off + len) - remain, buff, end, remain);
        end += remain;

    }


    // -------------------- Removing data from the buffer --------------------

    public int substract()
        throws IOException {

        if ((end - start) == 0) {
            if (in == null)
                return -1;
            int n = in.realReadBytes( buff, 0, buff.length );
            if (n < 0)
                return -1;
        }

        return (buff[start++] & 0xFF);

    }

    public int substract(ByteChunk src)
        throws IOException {

        if ((end - start) == 0) {
            if (in == null)
                return -1;
            int n = in.realReadBytes( buff, 0, buff.length );
            if (n < 0)
                return -1;
        }

        int len = getLength();
        src.append(buff, start, len);
        start = end;
        return len;

    }

    public int substract( byte src[], int off, int len )
        throws IOException {

        if ((end - start) == 0) {
            if (in == null)
                return -1;
            int n = in.realReadBytes( buff, 0, buff.length );
            if (n < 0)
                return -1;
        }

        int n = len;
        if (len > getLength()) {
            n = getLength();
        }