it.drwolf.ridire.util.JumpToLine.java Source code

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Here is the source code for it.drwolf.ridire.util.JumpToLine.java

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/*******************************************************************************
 * Copyright 2013 Universit degli Studi di Firenze
 * 
 * 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 it.drwolf.ridire.util;

/**
 * Copyright (c) 2010 Mark S. Kolich
 * http://mark.koli.ch
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

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

import org.apache.commons.io.IOUtils;
import org.apache.commons.io.LineIterator;

public class JumpToLine {

    private File file_;
    private long lastLineRead_;

    private InputStreamReader isr_;
    private LineIterator it_;

    public JumpToLine(File file) throws IOException {
        this.file_ = file;
        this.lastLineRead_ = 1L;
    }

    /**
     * Closes this IOUtils LineIterator and the underlying input stream reader.
     */
    public void close() {
        IOUtils.closeQuietly(this.isr_);
        if (this.it_ != null) {
            this.it_.close();
        }
    }

    public File getFile() {
        return this.file_;
    }

    public long getLastLineRead() {
        return this.lastLineRead_;
    }

    /**
     * Returns true of there are any more lines to read in the file. Otherwise,
     * returns false.
     * 
     * @return
     */
    public boolean hasNext() {
        return this.it_.hasNext();
    }

    /**
     * Opens any underlying streams/readers and immeadietly seeks to the line in
     * the file that's next to be read; skipping over lines in the file this
     * reader has already read.
     */
    public void open() throws IOException {
        try {
            this.isr_ = new InputStreamReader(new FileInputStream(this.file_));
            this.it_ = IOUtils.lineIterator(this.isr_);
        } catch (Exception e) {
            this.close();
            throw new IOException(e);
        }
    }

    /**
     * Read a line of text from this reader.
     * 
     * @return
     */
    public String readLine() {
        String ret = null;
        try {
            // If there is nothing more to read with this LineIterator
            // then nextLine() throws a NoSuchElementException.
            ret = this.it_.nextLine();
            this.lastLineRead_ += 1L;
        } catch (NoSuchElementException e) {
            throw e;
        }
        return ret;
    }

    /**
     * Seeks to the last line read in the file.
     */
    public long seek() {
        return this.seek(this.lastLineRead_);
    }

    /**
     * Seeks to a given line number in a file.
     * 
     * @param line
     */
    public long seek(long line) {
        long lineCount = 1L;
        while (this.it_ != null && this.it_.hasNext() && lineCount < line) {
            this.it_.nextLine();
            lineCount += 1L;
        }
        // If we got to the end of the file, but haven't read as many
        // lines as we should have, then the requested line number is
        // out of range.
        if (lineCount < line) {
            throw new NoSuchElementException("Invalid line number; " + "out of range.");
        }
        this.lastLineRead_ = lineCount;
        return lineCount;
    }

}