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The buffer management utilities used for managing streams of bytes that need to be treated as structured data. These are typically used to map structured records in files to and from systems that use these files types, i.e. IBM mainframe systems.
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/*
 * Copyright (c) 2009-2020 The Last Check, LLC, All Rights Reserved
 *
 * 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 com.thelastcheck.commons.buffer;

import java.io.Writer;

public class ByteArrayWriter extends Writer {
    private static final int    INITIAL_SIZE = 100;

    private ByteArray           buffer;
    private int                 position;
    private int                 limit;
    private final boolean       canResize;

    public ByteArrayWriter() {
        this(INITIAL_SIZE);
    }

    public ByteArrayWriter(int initialSize) {
        if (initialSize < 0) {
            throw new IllegalArgumentException("Negative initial size");
        }
        this.buffer = new ByteArray(initialSize);
        this.position = 0;
        this.limit = initialSize;
        this.canResize = true;
    }

    public ByteArrayWriter(ByteArray buffer) {
        if (buffer == null)
            throw new IllegalArgumentException("ByteArray cannot be null");
        this.buffer = buffer;
        this.position = 0;
        this.limit = buffer.getLength();
        this.canResize = false;
    }

    /**
     * Closing a ByteArrayWriter has no effect. The methods in this
     * class can be called after the stream has been closed without generating
     * an IOException.
     *
     * @see java.io.Writer#close()
     */
    @Override
    public void close() {
    }

    /**
     * Flushing a ByteArrayWriter has no effect.
     *
     * @see java.io.Writer#flush()
     */
    @Override
    public void flush() {
    }

    @Override
    public void write(char[] cbuf, int off, int len) {
        ensureCapacity(position + len);
        if ((off < 0) || (off > cbuf.length) || (len < 0) ||
                ((off + len) > cbuf.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return;
        }
        buffer.write(cbuf, off, len, position);
        position += len;
    }

    public ByteArray getBuffer() {
        if (position == limit) {
            return buffer;
        }
        return buffer.slice(0, position);
    }

    /**
     * Return the total number of bytes written to the ByteArray using the write
     * methods.
     *
     * @return total bytes written
     */
    public int getTotalBytesWritten() {
        return position;
    }

    /**
     * Write a single character.
     */
    public void write(int c) {
        ensureCapacity(position + 1);
        buffer.write((char) c, position++);
    }

    /**
     * Write a string.
     */
    public void write(String str) {
        ensureCapacity(position + str.length());
        buffer.write(str, position);
        position += str.length();
    }

    /**
     * Write a portion of a string.
     *
     * @param str
     *            String to be written
     * @param off
     *            Offset from which to start writing characters
     * @param len
     *            Number of characters to write
     */
    public void write(String str, int off, int len) {
        ensureCapacity(position + len);
        buffer.write(str.substring(off, off + len), position);
        position += len;
    }

    private void ensureCapacity(int minimumCapacity) {
        if (minimumCapacity > limit) {
            if (canResize) {
                expandCapacity(minimumCapacity);
            } else {
                throw new BufferCapacityReachedException();
            }
        }
    }

    private void expandCapacity(int minimumCapacity) {
        int newCapacity = (limit + 1) * 2;
        if (newCapacity < 0) {
            newCapacity = Integer.MAX_VALUE;
        } else if (minimumCapacity > newCapacity) {
            newCapacity = minimumCapacity;
        }
        ByteArray newBuffer = new ByteArray(newCapacity, buffer.getEncoding(), buffer.getOrder());
        newBuffer.write(buffer.getArray().value, 0);
        buffer = newBuffer;
        limit = newCapacity;
    }

}