bytebuffer.java

是一款用JAVA 编写的编译器 具有很强的编译功能

/*
 * Copyright 1999-2005 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package com.sun.tools.javac.util;

import java.io.*;

/** A byte buffer is a flexible array which grows when elements are
 *  appended. There are also methods to append names to byte buffers
 *  and to convert byte buffers to names.
 *
 *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If
 *  you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public class ByteBuffer {

    /** An array holding the bytes in this buffer; can be grown.
     */
    public byte[] elems;

    /** The current number of defined bytes in this buffer.
     */
    public int length;

    /** Create a new byte buffer.
     */
    public ByteBuffer() {
	this(64);
    }

    /** Create a new byte buffer with an initial elements array
     *  of given size.
     */
    public ByteBuffer(int initialSize) {
	elems = new byte[initialSize];
	length = 0;
    }

    private void copy(int size) {
	byte[] newelems = new byte[size];
	System.arraycopy(elems, 0, newelems, 0, elems.length);
	elems = newelems;
    }

    /** Append byte to this buffer.
     */
    public void appendByte(int b) {
	if (length >= elems.length) copy(elems.length * 2);
	elems[length++] = (byte)b;
    }

    /** Append `len' bytes from byte array,
     *  starting at given `start' offset.
     */
    public void appendBytes(byte[] bs, int start, int len) {
	while (length + len > elems.length) copy(elems.length * 2);
	System.arraycopy(bs, start, elems, length, len);
	length += len;
    }

    /** Append all bytes from given byte array.
     */
    public void appendBytes(byte[] bs) {
	appendBytes(bs, 0, bs.length);
    }

    /** Append a character as a two byte number.
     */
    public void appendChar(int x) {
	while (length + 1 >= elems.length) copy(elems.length * 2);
	elems[length  ] = (byte)((x >>  8) & 0xFF);
        elems[length+1] = (byte)((x      ) & 0xFF);
	length = length + 2;
    }

    /** Append an integer as a four byte number.
     */
    public void appendInt(int x) {
	while (length + 3 >= elems.length) copy(elems.length * 2);
	elems[length  ] = (byte)((x >> 24) & 0xFF);
        elems[length+1] = (byte)((x >> 16) & 0xFF);
	elems[length+2] = (byte)((x >>  8) & 0xFF);
        elems[length+3] = (byte)((x      ) & 0xFF);
	length = length + 4;
    }

    /** Append a long as an eight byte number.
     */
    public void appendLong(long x) {
        ByteArrayOutputStream buffer = new ByteArrayOutputStream(8);
        DataOutputStream bufout = new DataOutputStream(buffer);
        try {
            bufout.writeLong(x);
            appendBytes(buffer.toByteArray(), 0, 8);
        } catch (IOException e) {
            throw new AssertionError("write");
        }
    }

    /** Append a float as a four byte number.
     */
    public void appendFloat(float x) {
        ByteArrayOutputStream buffer = new ByteArrayOutputStream(4);
        DataOutputStream bufout = new DataOutputStream(buffer);
        try {
            bufout.writeFloat(x);
            appendBytes(buffer.toByteArray(), 0, 4);
        } catch (IOException e) {
            throw new AssertionError("write");
        }
    }

    /** Append a double as a eight byte number.
     */
    public void appendDouble(double x) {
        ByteArrayOutputStream buffer = new ByteArrayOutputStream(8);
        DataOutputStream bufout = new DataOutputStream(buffer);
        try {
            bufout.writeDouble(x);
            appendBytes(buffer.toByteArray(), 0, 8);
        } catch (IOException e) {
            throw new AssertionError("write");
        }
    }

    /** Append a name.
     */
    public void appendName(Name name) {
	appendBytes(name.table.names, name.index, name.len);
    }

    /** Reset to zero length.
     */
    public void reset() {
	length = 0;
    }

    /** Convert contents to name.
     */
    public Name toName(Name.Table names) {
	return names.fromUtf(elems, 0, length);
    }
}