StringBundler.java

/**
 * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library 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 Lesser General Public License for more
 * details.
 */

package com.liferay.portal.kernel.util;

import com.liferay.portal.kernel.memory.SoftReferenceThreadLocal;

import java.io.IOException;
import java.io.Serializable;
import java.io.Writer;

/**
 * <p>
 * See https://issues.liferay.com/browse/LPS-6072.
 * </p>
 *
 * @author Shuyang Zhou
 * @author Brian Wing Shun Chan
 * @author Preston Crary
 */
public class StringBundler implements Serializable {

	public StringBundler() {
		_array = new String[_DEFAULT_ARRAY_CAPACITY];
	}

	public StringBundler(int initialCapacity) {
		if (initialCapacity <= 0) {
			initialCapacity = _DEFAULT_ARRAY_CAPACITY;
		}

		_array = new String[initialCapacity];
	}

	public StringBundler(String s) {
		_array = new String[_DEFAULT_ARRAY_CAPACITY];

		_array[0] = s;

		_arrayIndex = 1;
	}

	public StringBundler(String[] stringArray) {
		this(stringArray, 0);
	}

	public StringBundler(String[] stringArray, int extraSpace) {
		_array = new String[stringArray.length + extraSpace];

		for (String s : stringArray) {
			if ((s != null) && (s.length() > 0)) {
				_array[_arrayIndex++] = s;
			}
		}
	}

	public StringBundler append(boolean b) {
		if (b) {
			return append(StringPool.TRUE);
		}
		else {
			return append(StringPool.FALSE);
		}
	}

	public StringBundler append(char c) {
		return append(String.valueOf(c));
	}

	public StringBundler append(char[] chars) {
		if (chars == null) {
			return append("null");
		}
		else {
			return append(new String(chars));
		}
	}

	public StringBundler append(double d) {
		return append(Double.toString(d));
	}

	public StringBundler append(float f) {
		return append(Float.toString(f));
	}

	public StringBundler append(int i) {
		return append(Integer.toString(i));
	}

	public StringBundler append(long l) {
		return append(Long.toString(l));
	}

	public StringBundler append(Object obj) {
		return append(String.valueOf(obj));
	}

	public StringBundler append(String s) {
		if (s == null) {
			s = StringPool.NULL;
		}

		if (s.length() == 0) {
			return this;
		}

		if (_arrayIndex >= _array.length) {
			expandCapacity(_array.length * 2);
		}

		_array[_arrayIndex++] = s;

		return this;
	}

	public StringBundler append(String[] stringArray) {
		if (ArrayUtil.isEmpty(stringArray)) {
			return this;
		}

		if ((_array.length - _arrayIndex) < stringArray.length) {
			expandCapacity((_array.length + stringArray.length) * 2);
		}

		for (String s : stringArray) {
			if ((s != null) && (s.length() > 0)) {
				_array[_arrayIndex++] = s;
			}
		}

		return this;
	}

	public StringBundler append(StringBundler sb) {
		if ((sb == null) || (sb._arrayIndex == 0)) {
			return this;
		}

		if ((_array.length - _arrayIndex) < sb._arrayIndex) {
			expandCapacity((_array.length + sb._arrayIndex) * 2);
		}

		System.arraycopy(sb._array, 0, _array, _arrayIndex, sb._arrayIndex);

		_arrayIndex += sb._arrayIndex;

		return this;
	}

	public int capacity() {
		return _array.length;
	}

	public String[] getStrings() {
		return _array;
	}

	public int index() {
		return _arrayIndex;
	}

	public int length() {
		int length = 0;

		for (int i = 0; i < _arrayIndex; i++) {
			length += _array[i].length();
		}

		return length;
	}

	public void setIndex(int newIndex) {
		if (newIndex < 0) {
			throw new ArrayIndexOutOfBoundsException(newIndex);
		}

		if (newIndex > _array.length) {
			String[] newArray = new String[newIndex];

			System.arraycopy(_array, 0, newArray, 0, _arrayIndex);

			_array = newArray;
		}

		if (_arrayIndex < newIndex) {
			for (int i = _arrayIndex; i < newIndex; i++) {
				_array[i] = StringPool.BLANK;
			}
		}

		if (_arrayIndex > newIndex) {
			for (int i = newIndex; i < _arrayIndex; i++) {
				_array[i] = null;
			}
		}

		_arrayIndex = newIndex;
	}

	public void setStringAt(String s, int index) {
		if ((index < 0) || (index >= _arrayIndex)) {
			throw new ArrayIndexOutOfBoundsException(index);
		}

		_array[index] = s;
	}

	public String stringAt(int index) {
		if ((index < 0) || (index >= _arrayIndex)) {
			throw new ArrayIndexOutOfBoundsException(index);
		}

		return _array[index];
	}

	@Override
	public String toString() {
		if (_arrayIndex == 0) {
			return StringPool.BLANK;
		}

		if (_arrayIndex == 1) {
			return _array[0];
		}

		if (_arrayIndex == 2) {
			return _array[0].concat(_array[1]);
		}

		if (_arrayIndex == 3) {
			return _array[0].concat(_array[1]).concat(_array[2]);
		}

		int length = 0;

		for (int i = 0; i < _arrayIndex; i++) {
			length += _array[i].length();
		}

		UnsafeStringBuilder usb = null;

		if (length > _THREAD_LOCAL_BUFFER_LIMIT) {
			usb = _unsafeStringBuilderThreadLocal.get();

			if (usb == null) {
				usb = new UnsafeStringBuilder(length);

				_unsafeStringBuilderThreadLocal.set(usb);
			}
			else {
				usb.resetAndEnsureCapacity(length);
			}
		}
		else {
			usb = new UnsafeStringBuilder(length);
		}

		for (int i = 0; i < _arrayIndex; i++) {
			usb.append(_array[i]);
		}

		return usb.toString();
	}

	public void writeTo(Writer writer) throws IOException {
		for (int i = 0; i < _arrayIndex; i++) {
			writer.write(_array[i]);
		}
	}

	protected void expandCapacity(int newCapacity) {
		String[] newArray = new String[newCapacity];

		System.arraycopy(_array, 0, newArray, 0, _arrayIndex);

		_array = newArray;
	}

	private static final int _DEFAULT_ARRAY_CAPACITY = 16;

	private static final int _THREAD_LOCAL_BUFFER_LIMIT;

	private static final ThreadLocal<UnsafeStringBuilder>
		_unsafeStringBuilderThreadLocal;
	private static final long serialVersionUID = 1L;

	static {
		int threadLocalBufferLimit = GetterUtil.getInteger(
			System.getProperty(
				StringBundler.class.getName() + ".threadlocal.buffer.limit"),
			Integer.MAX_VALUE);

		if ((threadLocalBufferLimit > 0) &&
			(threadLocalBufferLimit < Integer.MAX_VALUE)) {

			_THREAD_LOCAL_BUFFER_LIMIT = threadLocalBufferLimit;

			_unsafeStringBuilderThreadLocal = new SoftReferenceThreadLocal<>();
		}
		else {
			_THREAD_LOCAL_BUFFER_LIMIT = Integer.MAX_VALUE;

			_unsafeStringBuilderThreadLocal = null;
		}
	}

	private String[] _array;
	private int _arrayIndex;

	private static class UnsafeStringBuilder {

		public void append(String s) {
			int length = s.length();

			s.getChars(0, length, _value, _count);

			_count += length;
		}

		public void resetAndEnsureCapacity(int newLength) {
			if (_value.length < newLength) {
				int length = _value.length * 2 + 2;

				if (length < newLength) {
					length = newLength;
				}

				_value = new char[length];
			}

			_count = 0;
		}

		@Override
		public String toString() {
			return new String(_value, 0, _count);
		}

		private UnsafeStringBuilder(int length) {
			_value = new char[length];
		}

		private int _count;
		private char[] _value;

	}

}