/**
 * 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];
    }

    @Override
    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;
    }

    @Override
    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;
    }

    @Override
    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;
    }
}
