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73 lines
2.0 KiB
Java
73 lines
2.0 KiB
Java
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import edu.princeton.cs.introcs.BinaryStdIn;
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import edu.princeton.cs.introcs.BinaryStdOut;
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/*************************************************************************
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* Compilation: javac RunLength.java
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* Execution: java RunLength - < input.txt (compress)
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* Execution: java RunLength + < input.txt (expand)
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* Dependencies: BinaryIn.java BinaryOut.java
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*
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* Compress or expand binary input from standard input using
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* run-length encoding.
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*
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* % java BinaryDump 40 < 4runs.bin
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* 0000000000000001111111000000011111111111
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* 40 bits
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*
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* This has runs of 15 0s, 7 1s, 7 0s, and 11 1s.
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*
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* % java RunLength - < 4runs.bin | java HexDump
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* 0f 07 07 0b
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* 4 bytes
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*
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*************************************************************************/
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public class RunLength {
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private static final int R = 256;
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private static final int lgR = 8;
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public static void expand() {
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boolean b = false;
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while (!BinaryStdIn.isEmpty()) {
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int run = BinaryStdIn.readInt(lgR);
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for (int i = 0; i < run; i++)
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BinaryStdOut.write(b);
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b = !b;
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}
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BinaryStdOut.close();
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}
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public static void compress() {
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char run = 0;
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boolean old = false;
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while (!BinaryStdIn.isEmpty()) {
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boolean b = BinaryStdIn.readBoolean();
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if (b != old) {
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BinaryStdOut.write(run, lgR);
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run = 1;
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old = !old;
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}
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else {
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if (run == R-1) {
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BinaryStdOut.write(run, lgR);
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run = 0;
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BinaryStdOut.write(run, lgR);
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}
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run++;
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}
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}
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BinaryStdOut.write(run, lgR);
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BinaryStdOut.close();
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}
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public static void main(String[] args) {
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if (args[0].equals("-")) compress();
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else if (args[0].equals("+")) expand();
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else throw new IllegalArgumentException("Illegal command line argument");
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}
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}
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