source: other-projects/hathitrust/wcsa/extracted-features-solr/trunk/solr-ingest/src/main/java/org/hathitrust/extractedfeatures/WhitelistBloomFilter.java@ 31201

package org.hathitrust.extractedfeatures;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;

import com.google.common.hash.BloomFilter;
import com.google.common.hash.Funnel;
import com.google.common.hash.Funnels;

public class WhitelistBloomFilter {

    protected BloomFilter<CharSequence> _bloomFilter;
    protected static final String SERIALIZED_SUFFIX = "-serialized";
    protected static final double FALSE_POSITIVE_PERCENTAGE = 0.01;
    
    
    // http://stackoverflow.com/questions/453018/number-of-lines-in-a-file-in-java
    public static int countLines(String filename) throws IOException 
    {
        InputStream is = new BufferedInputStream(new FileInputStream(filename));

        try {
            byte[] c = new byte[1024];
            int count = 0;
            int readChars = 0;
            boolean empty = true;
            while ((readChars = is.read(c)) != -1) {
                empty = false;
                for (int i = 0; i < readChars; ++i) {
                    if (c[i] == '\n') {
                        ++count;
                    }
                }
            }
            return (count == 0 && !empty) ? 1 : count;
        } finally {
            is.close();
        }
    }


    public WhitelistBloomFilter(String dictionary_filename, boolean serialize) {
        System.out.println("Constructing: WhitelistBloomFilter");

        File ser_dictionary_file = new File(dictionary_filename + SERIALIZED_SUFFIX);
        
        if (ser_dictionary_file.exists()) {
            System.out.println("Loading Serialized Bloom filter ...");
            _bloomFilter = serializeIn(ser_dictionary_file);
            System.out.println("... done");
        }
        else {
            // Need to generate the Bloom filter from the given raw text file
            
            System.out.println("Counting lines in: " + dictionary_filename);
            int num_lines = -1;
            try {
                num_lines = countLines(dictionary_filename);

                Funnel<CharSequence> string_funnel = Funnels.stringFunnel(StandardCharsets.UTF_8);
                _bloomFilter = BloomFilter.create(string_funnel, num_lines,FALSE_POSITIVE_PERCENTAGE);
            } 
            catch (IOException e) {
                e.printStackTrace();
            }
            System.out.println("Number of lines: " + num_lines);
            
            storeEntries(dictionary_filename,serialize);
        }

    }

    protected void storeEntries(String filename, boolean serialize) 
    {
        System.out.println("Building Bloom filter ...");

        //read file into stream, try-with-resources
        try (Stream<String> stream = Files.lines(Paths.get(filename))) {
            stream.forEach(word -> {_bloomFilter.put(word);});
        } catch (IOException e) {
            e.printStackTrace();
        }

        System.out.println("... done");
        
        if (serialize) {
            System.out.println("Serializing Bloom filter ...");

            File ser_dictionary = new File(filename + SERIALIZED_SUFFIX);
            serializeOut(ser_dictionary);

            System.out.println("... done");
        }

    }

    public boolean contains(String key)
    {
        return _bloomFilter.mightContain(key);
    }

    protected void serializeOut(File ser_file)
    {
        try {
            FileOutputStream fos = new FileOutputStream(ser_file);

            BufferedOutputStream bfos = new BufferedOutputStream(fos);

            _bloomFilter.writeTo(bfos);

            bfos.close();
        }
        catch (FileNotFoundException e) {
            System.err.println("Unable to open Bloom file:" + ser_file.getAbsolutePath());
            e.printStackTrace();
        } catch (IOException e) {
            System.err.println("Error reading in Bloom file:" + ser_file.getAbsolutePath());
            e.printStackTrace();
        }
    }

    protected static BloomFilter<CharSequence> serializeIn(File ser_file)
    {
        BloomFilter<CharSequence> bloomFilter = null;
    
        try {
            FileInputStream fis = new FileInputStream(ser_file);
            BufferedInputStream bfis = new BufferedInputStream(fis);

            Funnel<CharSequence> string_funnel = Funnels.stringFunnel(StandardCharsets.UTF_8);
            bloomFilter = BloomFilter.readFrom(bfis,string_funnel);

            bfis.close();
        }
        catch (FileNotFoundException e) {
            System.err.println("Unable to open Bloom file:" + ser_file.getAbsolutePath());
            e.printStackTrace();
        } catch (IOException e) {
            System.err.println("Error writing out Bloom file:" + ser_file.getAbsolutePath());
            e.printStackTrace();
        }
        return bloomFilter;
    }


}