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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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.jboss.netty.util.internal;

import java.util.ArrayList;
import java.util.Formatter;
import java.util.List;

/**
 * String utility class.
 */
public final class StringUtil {

    private StringUtil() {
        // Unused.
    }

    public static final String NEWLINE;

    static {
        String newLine = null;

        try {
            newLine = new Formatter().format("%n").toString();
        } catch (Exception e) {
            newLine = "\n";
        }

        NEWLINE = newLine;
    }

    /**
     * Strip an Object of it's ISO control characters.
     *
     * @param value
     *          The Object that should be stripped. This objects toString method will
     *          called and the result passed to {@link #stripControlCharacters(String)}.
     * @return {@code String}
     *          A new String instance with its hexadecimal control characters replaced
     *          by a space. Or the unmodified String if it does not contain any ISO
     *          control characters.
     */
    public static String stripControlCharacters(Object value) {
        if (value == null) {
            return null;
        }

        return stripControlCharacters(value.toString());
    }

    /**
     * Strip a String of it's ISO control characters.
     *
     * @param value
     *          The String that should be stripped.
     * @return {@code String}
     *          A new String instance with its hexadecimal control characters replaced
     *          by a space. Or the unmodified String if it does not contain any ISO
     *          control characters.
     */
    public static String stripControlCharacters(String value) {
        if (value == null) {
            return null;
        }

        boolean hasControlChars = false;
        for (int i = value.length() - 1; i >= 0; i --) {
            if (Character.isISOControl(value.charAt(i))) {
                hasControlChars = true;
                break;
            }
        }

        if (!hasControlChars) {
            return value;
        }

        StringBuilder buf = new StringBuilder(value.length());
        int i = 0;

        // Skip initial control characters (i.e. left trim)
        for (; i < value.length(); i ++) {
            if (!Character.isISOControl(value.charAt(i))) {
                break;
            }
        }

        // Copy non control characters and substitute control characters with
        // a space.  The last control characters are trimmed.
        boolean suppressingControlChars = false;
        for (; i < value.length(); i ++) {
            if (Character.isISOControl(value.charAt(i))) {
                suppressingControlChars = true;
                continue;
            } else {
                if (suppressingControlChars) {
                    suppressingControlChars = false;
                    buf.append(' ');
                }
                buf.append(value.charAt(i));
            }
        }

        return buf.toString();
    }

    private static final String EMPTY_STRING = "";

    /**
     * Splits the specified {@link String} with the specified delimiter.  This operation is a simplified and optimized
     * version of {@link String#split(String)}.
     */
    public static String[] split(String value, char delim) {
        final int end = value.length();
        final List res = new ArrayList();

        int start = 0;
        for (int i = 0; i < end; i ++) {
            if (value.charAt(i) == delim) {
                if (start == i) {
                    res.add(EMPTY_STRING);
                } else {
                    res.add(value.substring(start, i));
                }
                start = i + 1;
            }
        }

        if (start == 0) { // If no delimiter was found in the value
            res.add(value);
        } else {
            if (start != end) {
                // Add the last element if it's not empty.
                res.add(value.substring(start, end));
            } else {
                // Truncate trailing empty elements.
                for (int i = res.size() - 1; i >= 0; i --) {
                    if (res.get(i).length() == 0) {
                        res.remove(i);
                    } else {
                        break;
                    }
                }
            }
        }

        return res.toArray(new String[res.size()]);
    }
}