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Apache XML Security for Java supports XML-Signature Syntax and Processing, W3C Recommendation 12 February 2002, and XML Encryption Syntax and Processing, W3C Recommendation 10 December 2002. As of version 1.4, the library supports the standard Java API JSR-105: XML Digital Signature APIs.

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/**
 * 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.xml.security.utils;

import java.io.IOException;
import java.io.OutputStream;

/**
 * A simple Unsynced ByteArrayOutputStream
 *
 */
public class UnsyncByteArrayOutputStream extends OutputStream  {

    // Maximum array size. Using same value as ArrayList in OpenJDK.
    // Integer.MAX_VALUE doesn't work on some VMs, as some header values are reserved
    private static final int VM_ARRAY_INDEX_MAX_VALUE = Integer.MAX_VALUE - 8;
    private static final int INITIAL_SIZE = 8192;

    private byte[] buf;
    private int size = INITIAL_SIZE;
    private int pos;

    public UnsyncByteArrayOutputStream() {
        buf = new byte[INITIAL_SIZE];
    }

    public void write(byte[] arg0) {
        if ((VM_ARRAY_INDEX_MAX_VALUE - pos) < arg0.length) {
            throw new OutOfMemoryError("Required length exceeds implementation limit");
        }
        int newPos = pos + arg0.length;
        if (newPos > size) {
            expandSize(newPos);
        }
        System.arraycopy(arg0, 0, buf, pos, arg0.length);
        pos = newPos;
    }

    public void write(byte[] arg0, int arg1, int arg2) {
        if ((VM_ARRAY_INDEX_MAX_VALUE - pos) < arg2) {
            throw new OutOfMemoryError("Required length exceeds implementation limit");
        }
        int newPos = pos + arg2;
        if (newPos > size) {
            expandSize(newPos);
        }
        System.arraycopy(arg0, arg1, buf, pos, arg2);
        pos = newPos;
    }

    public void write(int arg0) {
        if (VM_ARRAY_INDEX_MAX_VALUE - pos == 0) {
            throw new OutOfMemoryError("Required length exceeds implementation limit");
        }
        int newPos = pos + 1;
        if (newPos > size) {
            expandSize(newPos);
        }
        buf[pos++] = (byte)arg0;
    }

    public byte[] toByteArray() {
        byte[] result = new byte[pos];
        System.arraycopy(buf, 0, result, 0, pos);
        return result;
    }

    public void reset() {
        pos = 0;
    }

    /**
     * Takes the contents of this stream and writes it to the output stream
     * {@code out}.
     *
     * @param out
     *            an OutputStream on which to write the contents of this stream.
     * @throws IOException
     *             if an error occurs while writing to {@code out}.
     */
    public void writeTo(OutputStream out) throws IOException {
        out.write(buf, 0, pos);
    }

    private void expandSize(int newPos) {
        int newSize = size;
        while (newPos > newSize) {
            newSize = newSize << 1;
            // Deal with overflow
            if (newSize < 0) {
                newSize = VM_ARRAY_INDEX_MAX_VALUE;
            }
        }
        byte[] newBuf = new byte[newSize];
        System.arraycopy(buf, 0, newBuf, 0, pos);
        buf = newBuf;
        size = newSize;
    }
}