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lemirelemire
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Updating the documentation with memory-file mapping examples.
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‎README.md

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See example.java.
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Please note that there are more examples in the "examples" folder (e.g.,
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for memory-file mapping).
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Maven central repository
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------------------------
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‎example.java

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import com.googlecode.javaewah.EWAHCompressedBitmap;
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import java.io.*;
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import java.nio.ByteBuffer;
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/**
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* @author lemire
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*
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*/
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public class example {
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/**
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* @param args arguments from the command line
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* @throws IOException if an IO error occurs
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* Simple illustrative example.
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*
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* @author Daniel Lemire
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*
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*/
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public static void main(final String[] args) throws Exception {
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EWAHCompressedBitmap ewahBitmap1 = EWAHCompressedBitmap.bitmapOf(0,2,55,64,1<<30);
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EWAHCompressedBitmap ewahBitmap2 = EWAHCompressedBitmap.bitmapOf(1,3,64,1<<30);
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System.out.println("bitmap 1: "+ewahBitmap1);
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System.out.println("bitmap 2: "+ewahBitmap2);
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// or
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EWAHCompressedBitmap orbitmap = ewahBitmap1.or(ewahBitmap2);
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System.out.println("bitmap 1 OR bitmap 2: "+orbitmap);
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System.out.println("memory usage: " + orbitmap.sizeInBytes() + " bytes");
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// and
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EWAHCompressedBitmap andbitmap = ewahBitmap1.and(ewahBitmap2);
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System.out.println("bitmap 1 AND bitmap 2: "+andbitmap);
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System.out.println("memory usage: " + andbitmap.sizeInBytes() + " bytes");
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// xor
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EWAHCompressedBitmap xorbitmap = ewahBitmap1.xor(ewahBitmap2);
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System.out.println("bitmap 1 XOR bitmap 2:"+xorbitmap);
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System.out.println("memory usage: " + xorbitmap.sizeInBytes() + " bytes");
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// fast aggregation over many bitmaps
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EWAHCompressedBitmap ewahBitmap3 = EWAHCompressedBitmap.bitmapOf(5,55,1<<30);
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EWAHCompressedBitmap ewahBitmap4 = EWAHCompressedBitmap.bitmapOf(4,66,1<<30);
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System.out.println("bitmap 3: "+ewahBitmap3);
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System.out.println("bitmap 4: "+ewahBitmap4);
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andbitmap = EWAHCompressedBitmap.and(ewahBitmap1,ewahBitmap2,
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ewahBitmap3,ewahBitmap4);
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System.out.println("b1 AND b2 AND b3 AND b4: "+andbitmap);
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// serialization
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ByteArrayOutputStream bos = new ByteArrayOutputStream();
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// Note: you could use a file output steam instead of ByteArrayOutputStream
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ObjectOutputStream oo = new ObjectOutputStream(bos);
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ewahBitmap1.writeExternal(oo);
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oo.close();
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ewahBitmap1 = null;
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ewahBitmap1 = new EWAHCompressedBitmap();
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ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
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ewahBitmap1.readExternal(new ObjectInputStream(bis));
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System.out.println("bitmap 1 (recovered) : "+ewahBitmap1);
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//
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// support for threshold function (new as of version 0.8.0):
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// mark as true a bit that occurs at least T times in the source
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// bitmaps
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//
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EWAHCompressedBitmap threshold2 = EWAHCompressedBitmap.threshold(2, ewahBitmap1,ewahBitmap2,
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ewahBitmap3,ewahBitmap4);
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System.out.println("threshold 2 : "+threshold2);
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public class example
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{
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/**
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* @param args
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* arguments from the command line
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* @throws IOException
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* if an IO error occurs
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*/
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public static void main(final String[] args) throws Exception {
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EWAHCompressedBitmap ewahBitmap1 = EWAHCompressedBitmap.bitmapOf(0, 2, 55,
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64, 1 << 30);
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EWAHCompressedBitmap ewahBitmap2 = EWAHCompressedBitmap.bitmapOf(1, 3, 64,
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1 << 30);
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System.out.println("bitmap 1: " + ewahBitmap1);
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System.out.println("bitmap 2: " + ewahBitmap2);
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// or
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EWAHCompressedBitmap orbitmap = ewahBitmap1.or(ewahBitmap2);
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System.out.println("bitmap 1 OR bitmap 2: " + orbitmap);
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System.out.println("memory usage: " + orbitmap.sizeInBytes() + " bytes");
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// and
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EWAHCompressedBitmap andbitmap = ewahBitmap1.and(ewahBitmap2);
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System.out.println("bitmap 1 AND bitmap 2: " + andbitmap);
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System.out.println("memory usage: " + andbitmap.sizeInBytes() + " bytes");
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// xor
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EWAHCompressedBitmap xorbitmap = ewahBitmap1.xor(ewahBitmap2);
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System.out.println("bitmap 1 XOR bitmap 2:" + xorbitmap);
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System.out.println("memory usage: " + xorbitmap.sizeInBytes() + " bytes");
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// fast aggregation over many bitmaps
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EWAHCompressedBitmap ewahBitmap3 = EWAHCompressedBitmap.bitmapOf(5, 55,
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1 << 30);
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EWAHCompressedBitmap ewahBitmap4 = EWAHCompressedBitmap.bitmapOf(4, 66,
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1 << 30);
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System.out.println("bitmap 3: " + ewahBitmap3);
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System.out.println("bitmap 4: " + ewahBitmap4);
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andbitmap = EWAHCompressedBitmap.and(ewahBitmap1, ewahBitmap2, ewahBitmap3,
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ewahBitmap4);
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System.out.println("b1 AND b2 AND b3 AND b4: " + andbitmap);
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// serialization
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ByteArrayOutputStream bos = new ByteArrayOutputStream();
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// Note: you could use a file output steam instead of ByteArrayOutputStream
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ewahBitmap1.serialize(new DataOutputStream(bos));
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EWAHCompressedBitmap ewahBitmap1new = new EWAHCompressedBitmap();
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byte[] bout = bos.toByteArray();
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ewahBitmap1new.deserialize(new DataInputStream(new ByteArrayInputStream(
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bout)));
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System.out.println("bitmap 1 (recovered) : " + ewahBitmap1new);
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if (!ewahBitmap1.equals(ewahBitmap1new))
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throw new RuntimeException("Will not happen");
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//
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// we can use a ByteBuffer as backend for a bitmap
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// which allows memory-mapped bitmaps
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//
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ByteBuffer bb = ByteBuffer.wrap(bout);
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EWAHCompressedBitmap rmap = new EWAHCompressedBitmap(bb);
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System.out.println("bitmap 1 (mapped) : " + rmap);
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if (!rmap.equals(ewahBitmap1))
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throw new RuntimeException("Will not happen");
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//
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// support for threshold function (new as of version 0.8.0):
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// mark as true a bit that occurs at least T times in the source
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// bitmaps
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//
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EWAHCompressedBitmap threshold2 = EWAHCompressedBitmap.threshold(2,
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ewahBitmap1, ewahBitmap2, ewahBitmap3, ewahBitmap4);
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System.out.println("threshold 2 : " + threshold2);
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}
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}
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}

‎examples/MemoryMappingExample.java

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import com.googlecode.javaewah.EWAHCompressedBitmap;
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import java.io.*;
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import java.nio.*;
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import java.nio.channels.FileChannel;
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public class MemoryMappingExample {
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public static void main(String[] args) throws IOException {
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File tmpfile = File.createTempFile("roaring", "bin");
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tmpfile.deleteOnExit();
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final FileOutputStream fos = new FileOutputStream(tmpfile);
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EWAHCompressedBitmap ewahBitmap = EWAHCompressedBitmap.bitmapOf(0, 2, 55,
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64, 1 << 30);
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System.out.println("Created the bitmap "+ewahBitmap);
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ewahBitmap.serialize(new DataOutputStream(fos));
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long totalcount = fos.getChannel().position();
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System.out.println("Serialized total count = "+totalcount+" bytes");
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fos.close();
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RandomAccessFile memoryMappedFile = new RandomAccessFile(tmpfile, "r");
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ByteBuffer bb = memoryMappedFile.getChannel().map(FileChannel.MapMode.READ_ONLY, 0, totalcount);
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EWAHCompressedBitmap mapped = new EWAHCompressedBitmap(bb);
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System.out.println("Mapped the bitmap "+mapped);
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memoryMappedFile.close();
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}
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}

‎src/main/java/com/googlecode/javaewah/RunningLengthWord.java

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buffer.andWord(position, (number << (RUNNING_LENGTH_BITS + 1)) | RUNNING_LENGTH_PLUS_RUNNING_BIT);
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}
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/**@Override
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public
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/**
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* Sets the running bit.
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*
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* @param b the new running bit
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private static final long NOT_SHIFTED_LARGEST_RUNNING_LENGTH_COUNT = ~SHIFTED_LARGEST_RUNNING_LENGTH_COUNT;
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}
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}

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