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brianwaybrianway
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[add] add some examples of nio
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‎java-io/src/main/java/com/brianway/learning/java/nio/BufferToText.java‎

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‎java-io/src/main/java/com/brianway/learning/java/nio/ChannelCopy.java‎

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package com.brianway.learning.java.nio;
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import java.io.FileInputStream;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.nio.ByteBuffer;
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import java.nio.channels.FileChannel;
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/**
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* Created by brian on 16/11/29.
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*/
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public class ChannelCopy {
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private static final int BSIZE = 1024;
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public static void main(String[] args) throws IOException {
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String parent = ChannelCopy.class.getResource("/").getPath();
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String infile = parent + "/infile.txt";
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String outCopy = parent + "/outCopy.txt";
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String outTransferTo = parent + "/outTransferTo.txt";
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copy(infile, outCopy);
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transferTo(infile, outTransferTo);
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}
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private static void copy(String infile, String outfile) throws IOException {
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FileChannel
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in = new FileInputStream(infile).getChannel(),
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out = new FileOutputStream(outfile).getChannel();
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ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
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while (in.read(buffer) != -1) {
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buffer.flip(); // prepare for writing
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out.write(buffer);
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buffer.clear(); // prepare for reading
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}
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}
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private static void transferTo(String infile, String outfile) throws IOException {
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FileChannel
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in = new FileInputStream(infile).getChannel(),
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out = new FileOutputStream(outfile).getChannel();
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in.transferTo(0, in.size(), out);
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// Or:
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// out.transferFrom(in,0,in.size());
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}
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}

‎java-io/src/main/java/com/brianway/learning/java/nio/Endians.java‎

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package com.brianway.learning.java.nio;
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import java.nio.ByteBuffer;
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import java.nio.ByteOrder;
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import java.util.Arrays;
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/**
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* Created by brian on 16/11/29.
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*
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* "big endian"(高位优先),将最重要的字节放在地址最低的存储器单元;
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* "little endian"(低位优先),将最重要的字节放在地址最高的存储器单元;
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*
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* ByteBuffer 是以高位优先的形式存储数据的。
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*/
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public class Endians {
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public static void main(String[] args) {
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ByteBuffer bb = ByteBuffer.wrap(new byte[12]);
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bb.asCharBuffer().put("abcdef");
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System.out.println(Arrays.toString(bb.array()));
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bb.rewind();
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bb.order(ByteOrder.BIG_ENDIAN);
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bb.asCharBuffer().put("abcdef");
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System.out.println(Arrays.toString(bb.array()));
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bb.rewind();
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bb.order(ByteOrder.LITTLE_ENDIAN);
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bb.asCharBuffer().put("abcdef");
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System.out.println(Arrays.toString(bb.array()));
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}
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}
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/* Output:
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[0, 97, 0, 98, 0, 99, 0, 100, 0, 101, 0, 102]
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[0, 97, 0, 98, 0, 99, 0, 100, 0, 101, 0, 102]
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[97, 0, 98, 0, 99, 0, 100, 0, 101, 0, 102, 0]
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*///:~

‎java-io/src/main/java/com/brianway/learning/java/nio/GetChannel.java‎

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package com.brianway.learning.java.nio;
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import java.io.FileInputStream;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.nio.ByteBuffer;
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import java.nio.channels.FileChannel;
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/**
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* Created by brian on 16/11/29.
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*/
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public class GetChannel {
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private static final int BSIZE = 1024;
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public static void main(String[] args) throws IOException {
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String parent = GetChannel.class.getResource("/").getPath();
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String filename = parent + "/data.txt";
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write(filename);
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addToEnd(filename);
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read(filename);
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}
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private static void write(String filename) throws IOException {
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FileChannel fc = new FileOutputStream(filename).getChannel();
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fc.write(ByteBuffer.wrap("Some text ".getBytes()));
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fc.close();
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}
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private static void addToEnd(String filename) throws IOException {
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FileChannel fc = new RandomAccessFile(filename, "rw").getChannel();
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fc.position(fc.size());
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fc.write(ByteBuffer.wrap("Some more ".getBytes()));
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fc.close();
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}
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private static void read(String filename) throws IOException {
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FileChannel fc = new FileInputStream(filename).getChannel();
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ByteBuffer buff = ByteBuffer.allocate(BSIZE);
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fc.read(buff);
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buff.flip();
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while (buff.hasRemaining()) {
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System.out.print((char) buff.get());
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}
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fc.close();
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}
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}

‎java-io/src/main/java/com/brianway/learning/java/nio/ViewBuffers.java‎

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package com.brianway.learning.java.nio;//: io/ViewBuffers.java
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import java.nio.ByteBuffer;
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import java.nio.CharBuffer;
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import java.nio.DoubleBuffer;
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import java.nio.FloatBuffer;
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import java.nio.IntBuffer;
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import java.nio.LongBuffer;
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import java.nio.ShortBuffer;
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/**
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* Created by brian on 16/11/29.
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*
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* 通过在同一个 ByteBuffer 上建立不同的试图缓冲器,
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* 将同一字节序列翻译成short,int,float,long,double等类型的数据
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*/
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public class ViewBuffers {
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public static void main(String[] args) {
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ByteBuffer bb = ByteBuffer.wrap(
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new byte[] {0, 0, 0, 0, 0, 0, 0, 'a'});
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bb.rewind();
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System.out.print("Byte Buffer ");
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while (bb.hasRemaining())
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System.out.print(bb.position() + " -> " + bb.get() + ", ");
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System.out.println();
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CharBuffer cb =
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((ByteBuffer) bb.rewind()).asCharBuffer();
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System.out.println("Char Buffer ");
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while (cb.hasRemaining())
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System.out.print(cb.position() + " -> " + cb.get() + ", ");
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System.out.println();
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FloatBuffer fb =
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((ByteBuffer) bb.rewind()).asFloatBuffer();
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System.out.print("Float Buffer ");
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while (fb.hasRemaining())
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System.out.print(fb.position() + " -> " + fb.get() + ", ");
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System.out.println();
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IntBuffer ib =
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((ByteBuffer) bb.rewind()).asIntBuffer();
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System.out.print("Int Buffer ");
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while (ib.hasRemaining())
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System.out.print(ib.position() + " -> " + ib.get() + ", ");
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System.out.println();
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LongBuffer lb =
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((ByteBuffer) bb.rewind()).asLongBuffer();
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System.out.print("Long Buffer ");
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while (lb.hasRemaining())
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System.out.print(lb.position() + " -> " + lb.get() + ", ");
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System.out.println();
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ShortBuffer sb =
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((ByteBuffer) bb.rewind()).asShortBuffer();
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System.out.print("Short Buffer ");
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while (sb.hasRemaining())
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System.out.print(sb.position() + " -> " + sb.get() + ", ");
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System.out.println();
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DoubleBuffer db =
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((ByteBuffer) bb.rewind()).asDoubleBuffer();
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System.out.print("Double Buffer ");
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while (db.hasRemaining())
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System.out.print(db.position() + " -> " + db.get() + ", ");
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}
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}
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/* Output:
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Byte Buffer 0 -> 0, 1 -> 0, 2 -> 0, 3 -> 0, 4 -> 0, 5 -> 0, 6 -> 0, 7 -> 97,
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Char Buffer 0 -> , 1 -> , 2 -> , 3 -> a,
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Float Buffer 0 -> 0.0, 1 -> 1.36E-43,
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Int Buffer 0 -> 0, 1 -> 97,
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Long Buffer 0 -> 97,
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Short Buffer 0 -> 0, 1 -> 0, 2 -> 0, 3 -> 97,
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Double Buffer 0 -> 4.8E-322,
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*///:~

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