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/*
 * Copyright @ 2015 Atlassian Pty Ltd
 *
 * Licensed 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.jitsi.service.neomedia;

import org.jitsi.utils.*;

import java.util.*;

/**
 * Implements {@link ByteArrayBuffer}.
 * @author Boris Grozev
 */
public class ByteArrayBufferImpl
    implements ByteArrayBuffer
{
    /**
     * The byte array represented by this {@link ByteArrayBufferImpl}.
     */
    protected byte[] buffer;

    /**
     * The offset in the byte buffer where the actual data starts.
     */
    private int offset;

    /**
     * The length of the data in the buffer.
     */
    private int length;

    /**
     * Initializes a new {@link ByteArrayBufferImpl} instance.
     * @param buffer
     * @param offset
     * @param length
     */
    public ByteArrayBufferImpl(byte[] buffer, int offset, int length)
    {
        this.buffer = Objects.requireNonNull(buffer, "buffer");
        if (offset + length > buffer.length || length < 0 || offset < 0)
        {
            throw new IllegalArgumentException("length or offset");
        }
        this.offset = offset;
        this.length = length;
    }

    /**
     * Initializes a new {@link ByteArrayBufferImpl} based on a newly allocated
     * byte array with the given size.
     * @param size the size of the underlying byte array.
     */
    public ByteArrayBufferImpl(int size)
    {
        if (size < 0)
        {
            throw new IllegalArgumentException("size");
        }
        buffer = new byte[size];
        offset = 0;
        length = size;
    }

    /**
     * Initializes a new {@link ByteArrayBufferImpl} instance.
     */
    public ByteArrayBufferImpl(byte[] buf)
    {
        this(buf, 0, buf.length);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public byte[] getBuffer()
    {
        return buffer;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int getOffset()
    {
        return offset;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int getLength()
    {
        return length;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setLength(int length)
    {
        if (offset + length > buffer.length || length < 0)
        {
            throw new IllegalArgumentException("length");
        }
        this.length = length;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setOffset(int offset)
    {
        if (offset + length > buffer.length || offset < 0)
        {
            throw new IllegalArgumentException("offset");
        }
        this.offset = offset;
    }

    /**
     * Sets the offset and the length of this {@link ByteArrayBuffer}
     * @param offset the offset to set.
     * @param length the length to set.
     */
    public void setOffsetLength(int offset, int length)
    {
        if (offset + length > buffer.length || length < 0 || offset < 0)
        {
            throw new IllegalArgumentException("length or offset");
        }
        this.offset = offset;
        this.length = length;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isInvalid()
    {
        return false;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void readRegionToBuff(int off, int len, byte[] outBuff)
    {
        int startOffset = this.offset + off;
        if (off < 0 || len <= 0 || startOffset + len > this.buffer.length)
        {
            return;
        }

        if (outBuff.length < len)
        {
            return;
        }

        System.arraycopy(this.buffer, startOffset, outBuff, 0, len);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void grow(int howMuch)
    {
        if (howMuch < 0)
            throw new IllegalArgumentException("howMuch");

        int newLength = length + howMuch;

        if (newLength > buffer.length - offset)
        {
            byte[] newBuffer = new byte[newLength];

            System.arraycopy(buffer, offset, newBuffer, 0, length);
            offset = 0;
            buffer = newBuffer;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void append(byte[] data, int len)
    {
        if (data == null || len == 0)
        {
            return;
        }

        // Ensure the internal buffer is long enough to accommodate data. (The
        // method grow will re-allocate the internal buffer if it's too short.)
        grow(len);
        // Append data.
        System.arraycopy(data, 0, buffer, length + offset, len);
        length += len;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void shrink(int len)
    {
        if (len <= 0)
        {
            return;
        }

        length = Math.max(0, length - len);
    }
}