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The ANTLR 4 Runtime
There is a newer version: 4.13.2
/*
 * [The "BSD license"]
 *  Copyright (c) 2012 Terence Parr
 *  Copyright (c) 2012 Sam Harwell
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.antlr.v4.runtime.misc;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class Utils {
    // Seriously: why isn't this built in to java? ugh!
    public static  String join(Iterator iter, String separator) {
        StringBuilder buf = new StringBuilder();
        while ( iter.hasNext() ) {
            buf.append(iter.next());
            if ( iter.hasNext() ) {
                buf.append(separator);
            }
        }
        return buf.toString();
    }

	public static  String join(T[] array, String separator) {
		StringBuilder builder = new StringBuilder();
		for (int i = 0; i < array.length; i++) {
			builder.append(array[i]);
			if (i < array.length - 1) {
				builder.append(separator);
			}
		}

		return builder.toString();
	}

	public static int numNonnull(Object[] data) {
		int n = 0;
		if ( data == null ) return n;
		for (Object o : data) {
			if ( o!=null ) n++;
		}
		return n;
	}

	public  static  void removeAllElements(Collection data, T value) {
		if ( data==null ) return;
		while ( data.contains(value) ) data.remove(value);
	}

	public static String escapeWhitespace(String s, boolean escapeSpaces) {
		StringBuilder buf = new StringBuilder();
		for (char c : s.toCharArray()) {
			if ( c==' ' && escapeSpaces ) buf.append('\u00B7');
			else if ( c=='\t' ) buf.append("\\t");
			else if ( c=='\n' ) buf.append("\\n");
			else if ( c=='\r' ) buf.append("\\r");
			else buf.append(c);
		}
		return buf.toString();
	}

	public static void writeFile(String fileName, String content) throws IOException {
		writeFile(fileName, content, null);
	}

	public static void writeFile(String fileName, String content, String encoding) throws IOException {
		File f = new File(fileName);
		FileOutputStream fos = new FileOutputStream(f);
		OutputStreamWriter osw;
		if (encoding != null) {
			osw = new OutputStreamWriter(fos, encoding);
		}
		else {
			osw = new OutputStreamWriter(fos);
		}

		try {
			osw.write(content);
		}
		finally {
			osw.close();
		}
	}


	public static char[] readFile(String fileName) throws IOException {
		return readFile(fileName, null);
	}


	public static char[] readFile(String fileName, String encoding) throws IOException {
		File f = new File(fileName);
		int size = (int)f.length();
		InputStreamReader isr;
		FileInputStream fis = new FileInputStream(fileName);
		if ( encoding!=null ) {
			isr = new InputStreamReader(fis, encoding);
		}
		else {
			isr = new InputStreamReader(fis);
		}
		char[] data = null;
		try {
			data = new char[size];
			int n = isr.read(data);
			if (n < data.length) {
				data = Arrays.copyOf(data, n);
			}
		}
		finally {
			isr.close();
		}
		return data;
	}

	/** Convert array of strings to string→index map. Useful for
	 *  converting rulenames to name→ruleindex map.
	 */
	public static Map toMap(String[] keys) {
		Map m = new HashMap();
		for (int i=0; i= 0 ) {
			s.add(i);
			i = bits.nextSetBit(i+1);
		}
		return s;
	}
}