Question

Write a parity checker for the ASCII system in MARIE. MARIE is an assembly language. The parity checker should repeatedly execute a loop that performs the following tasks: 1. Ask the user for an input X, which can be any printable ASCII character from Table 1; 2. Output the decimal code of X; 3. Output the total number of 1’s that appears in the binary code of X; 4. Output the parity bit which, when added to the binary code of X, will make the number of 1’s even.

Answer 1

import MarieSimTester.Test;

static class Parity {

static final byte start = 33; // Start at 33 instead of 32 (because 32 is whitespace, which is not directly accepted by MarieSim)

static final byte end = 126; // End at the last ASCII code.

// default sample program for this project

static final String DefaultMasfilepath = "testbed/parity-brute.mas";

// Generate the sequence of ascii characters within the given range and including the boundary.

public String input(int start, int end) {

// If the range is invalid, fix it with the correct range.

if (start<Parity.start) start=Parity.start;

if (end>Parity.end) end=Parity.end;

String ascii = "";

for (byte i=(byte)start; i<=(byte)end; i++) {

// Convert the byte to character (note: Java uses unicode)

char c = (char) i;

if (ascii.length()!=0)

ascii += " ";

ascii += c;

}

return ascii;

}

public String toBinary(char c) {

// Convert the byte to binary string

// Reference: http://stackoverflow.com/questions/12310017/how-to-convert-a-byte-to-its-binary-string-representation

return String.format("%8s", Integer.toBinaryString(c & 0xFF)).replace(' ', '0');

}

// Provide result for each ascii character

// Output for each character includes:

// (1) the decimal value of the ASCII code

// (2) the number bits with value 1 in the code

// (3) whether an additional 1 bit is needed to make the parity even.

public String output(char c) {

// Convert the char to decimal

String binary = toBinary(c);

int dec = (int) (c & 0xFF);

// Count the number of 1s in the binary string.

// Reference: http://stackoverflow.com/questions/275944/java-how-do-i-count-the-number-of-occurrences-of-a-char-in-a-string

int count = binary.length() - binary.replace("1", "").length();

int parity = count%2==0 ? 0 : 1;

return dec + " " + count + " " + parity;

}

public String output(String input) {

if (input==null) return null;

// split input by whitespaces.

String[] chars = input.trim().split("\\s");

String result = "";

for (String token : chars) {

if (token.length()>=1) {

if (result.length()>0) result += " ";

result += output(token.charAt(0));

}

}

return result;

}

// Provide result for each ascii character in the specific range.

public String output(int start, int end) {

if (start<Parity.start) start=Parity.start;

if (end>Parity.end) end=Parity.end;

String result = "";

for (byte i=(byte)start; i<=(byte)end; i++) {

result += output((char) i) + " ";

}

return result;

}

// Support printing of ascii for visual verification if needed.

public void print() {

for (byte i=start; i<=end; i++) {

char c = (char) i;

// Add a space every 4 bits for ease of reading.

String binary = toBinary(c);

binary = binary.substring(1, 4) + " " + binary.substring(4, 8);

System.out.println(c + " " + binary + " " + output(c));

}

}

}

public static void testSingleRun(String masfilepath) {

Parity fn = new Parity();

// Test just the first few ASCII characters.

int start=33;

int end=35;

final String input = fn.input(start, end);

final String expectedOutput = fn.output(start, end);

final int maxPollCount = 10;

if (masfilepath==null) masfilepath = fn.DefaultMasfilepath;

(new Test()).singleRunAscii2Dec(masfilepath, input, expectedOutput, maxPollCount);

}

public static void testMultiRunAllChars(String masfilepath) {

Parity fn = new Parity();

final int inputsPerRun = 10;

final int maxPollCount = (int)((double)inputsPerRun*2.5); // tune accordingly to allow enough time.

// Test all ASCII characters

int total = (int)(Parity.end-Parity.start)+1;

// Count the total number of runs.

int runs = (int) Math.ceil((double)total/(double)inputsPerRun);

String inputs[] = new String[runs];

String expectedOutputs[] = new String[runs];

for (int run=0; run<runs; run++) {

int start = run*inputsPerRun + Parity.start;

int end = start + inputsPerRun - 1;

// If start or end is out of range, the fn method will automatically fix it.

inputs[run] = fn.input(start, end);

expectedOutputs[run] = fn.output(start, end);

}

if (masfilepath==null) masfilepath = fn.DefaultMasfilepath;

(new Test()).multiRunsAscii2Dec(masfilepath, inputs, expectedOutputs, maxPollCount);

}

public static void testMultiRun(String masfilepath) {

Parity fn = new Parity();

final int inputsPerRun = 6;

final int maxPollCount = (int)((double)inputsPerRun*2.5); // tune accordingly to allow enough time.

String inputs[] = { "H i !",

"{ W }",

"z Z",

"2 3 4",

"A b C d",

"@ A d e g o"};

String expectedOutputs[] = new String[inputs.length];

for (int run=0; run<inputs.length; run++) {

expectedOutputs[run] = fn.output(inputs[run]);

}

if (masfilepath==null) masfilepath = fn.DefaultMasfilepath;

(new Test()).multiRunsAscii2Dec(masfilepath, inputs, expectedOutputs, maxPollCount);

}

public static void main(String args[]) {

if (args.length>=1) {

testMultiRunAllChars(args[0]);

}

else {

// default

Usage.print(TestParity.class, Parity.DefaultMasfilepath);

testMultiRunAllChars(null);

}

}

}