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The S-Space Package is a collection of algorithms for building Semantic Spaces as well as a highly-scalable library for designing new distributional semantics algorithms. Distributional algorithms process text corpora and represent the semantic for words as high dimensional feature vectors. This package also includes matrices, vectors, and numerous clustering algorithms. These approaches are known by many names, such as word spaces, semantic spaces, or distributed semantics and rest upon the Distributional Hypothesis: words that appear in similar contexts have similar meanings.

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/*
 * Copyright 2011 Keith Stevens
 *
 * This file is part of the S-Space package and is covered under the terms and
 * conditions therein.
 *
 * The S-Space package is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation and distributed hereunder to you.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND NO REPRESENTATIONS OR WARRANTIES,
 * EXPRESS OR IMPLIED ARE MADE.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, WE MAKE
 * NO REPRESENTATIONS OR WARRANTIES OF MERCHANT- ABILITY OR FITNESS FOR ANY
 * PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE OR DOCUMENTATION
 * WILL NOT INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER
 * RIGHTS.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see .
 */

package edu.ucla.sspace.matrix;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOError;
import java.io.IOException;

import java.util.Iterator;
import java.util.NoSuchElementException;


/**
 * An iterator for sequentially accessing the data of a {@link
 * MatrixIO.Format.SVDLIBC_DENSE_BINARY} formatted file.
 *
 * @author Keith Stevens
 */
class ClutoSparseFileIterator implements Iterator {

    /**
     * The {@link DataInputStream} holding the matrix data.
     */
    private final BufferedReader reader;

    /**
     * The next {@link MatrixEntry} to be returned.
     */
    private MatrixEntry next;
    
    /**
     * The number of rows in the matrix.
     */
    private int rows;

    /**
     * The number of columns in the matrix.
     */
    private int cols;

    /**
     * The number of nonZeros on this line.
     */
    private int curColIndex;

    /**
     * The row number of the next value to return
     */
    private int curRow;

    /**
     * The current line to be parsed.
     */
    private String[] curLine;

    /**
     * Creates a new {@link ClutoSparseFileIterator} for {@code
     * matrixFile}.
     */
    public ClutoSparseFileIterator(File matrixFile) throws IOException {
        reader = new BufferedReader(new FileReader(matrixFile));
        String[] numRowCol = reader.readLine().split("\\s");
        rows = Integer.parseInt(numRowCol[0]);
        cols = Integer.parseInt(numRowCol[1]);

        curRow= 0;
        curColIndex = 0;
        curLine = readLine();
        next = advance();
    }

    private MatrixEntry advance() throws IOException {        
        if (curRow >= rows) 
            return null;

        // Check that there are still non zero values to read for the current
        // row.  If not, advance to the next row.
        if (curColIndex >= curLine.length) {
            curColIndex = 0;
            curRow++;

            // If the last row has been read, return null.
            if (curRow >= rows) {
                reader.close();
                return null;
            }

            curLine = readLine();
        }

        // Parse the current column and value pair and return the corresponding
        // matrix entry.
        return new SimpleEntry(curRow,
                               Integer.parseInt(curLine[curColIndex++]) - 1,
                               Double.parseDouble(curLine[curColIndex++]));
    }

    /**
     * Reads a line and splits it into [col value] pairs.
     *
     * @throws IllegalArgumentException If there are no more lines to read.
     */
    private String[] readLine() throws IOException {
        // Read the next number of non zeros.
        String line = reader.readLine();
        if (line == null)
            throw new IllegalArgumentException(
                    "The matrix file is improperly formatted");
        return line.split("\\s+");
    }

    /**
     * {@inheritDoc}
     */
    public boolean hasNext() {
        return next != null;
    }

    /**
     * {@inheritDoc}
     */
    public MatrixEntry next() {
        if (next == null) 
            throw new NoSuchElementException("No futher entries");
        MatrixEntry me = next;
        try {
            next = advance();
        } catch (IOException ioe) {
            throw new IOError(ioe);
        }
        return me;
    }

    /**
     * Throws an {@link UnsupportedOperationException} if called.
     */
    public void remove() {
        throw new UnsupportedOperationException("Cannot remove from file");
    }
}