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The ANTLR 4 Runtime
There is a newer version: 4.9.0
/*
 * [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;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

/** This is an ANTLRInputStream that is loaded from a file
 *  all at once when you construct the object.  This is a special case
 *  since we know the exact size of the object to load.  We can avoid lots
 *  of data copying.
 */
public class ANTLRFileStream extends ANTLRInputStream {
	protected String fileName;

	public ANTLRFileStream(String fileName) throws IOException {
		this(fileName, null);
	}

	public ANTLRFileStream(String fileName, String encoding) throws IOException {
		this.fileName = fileName;
		load(fileName, encoding);
	}

	public void load(String fileName, String encoding)
		throws IOException
	{
		if ( fileName==null ) {
			return;
		}
		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);
		}
		try {
			data = new char[size];
			super.n = isr.read(data);
		}
		finally {
			isr.close();
		}
	}

	@Override
	public String getSourceName() {
		return fileName;
	}
}