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package algs55; // section 5.5
import stdlib.*;
/* ***********************************************************************
* Compilation: javac RunLength.java
* Execution: java RunLength - < input.txt (compress)
* Execution: java RunLength + < input.txt (expand)
* Dependencies: BinaryIn.java BinaryOut.java
*
* Compress or expand binary input from standard input using
* run-length encoding.
*
* % java BinaryDump 40 < 4runs.bin
* 0000000000000001111111000000011111111111
* 40 bits
*
* This has runs of 15 0s, 7 1s, 7 0s, and 11 1s.
*
* % java RunLength - < 4runs.bin | java HexDump
* 0f 07 07 0b
* 4 bytes
*
*************************************************************************/
public class RunLength {
private static BinaryIn binaryIn;
private static BinaryOut binaryOut;
private static final int R = 256;
private static final int lgR = 8;
public static void expand() {
boolean b = false;
while (!binaryIn.isEmpty()) {
int run = binaryIn.readInt(lgR);
for (int i = 0; i < run; i++)
binaryOut.write(b);
b = !b;
}
binaryOut.close();
}
public static void compress() {
char run = 0;
boolean old = false;
while (!binaryIn.isEmpty()) {
boolean b = binaryIn.readBoolean();
if (b != old) {
binaryOut.write(run, lgR);
run = 1;
old = !old;
}
else {
if (run == R-1) {
binaryOut.write(run, lgR);
run = 0;
binaryOut.write(run, lgR);
}
run++;
}
}
binaryOut.write(run, lgR);
binaryOut.close();
}
public static void main(String[] args) {
String txtFile = "data/4runs.bin";
String binFile = "4runsOut.bin";
//args = new String[] { "+" }; binaryIn = new BinaryIn(binFile); binaryOut = new BinaryOut();
args = new String[] { "-" }; binaryIn = new BinaryIn(txtFile); binaryOut = new BinaryOut(binFile);
if (args[0].equals("-")) compress();
else if (args[0].equals("+")) expand();
else throw new Error("Illegal command line argument");
}
}
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