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hamming.js
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hamming.js
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// Generated by CoffeeScript 1.4.0
(function() {
var NUM_PROMPTS, convertToBitArray, flippedBit, generateHammingCode, input, intro, largestPowerForNum, printArraySingle, promptHammingCode, promptResponse, prompts, setupStep, simulateNetwork;
convertToBitArray = function(data, maxLength) {
var bit, i, mask, result, _i;
if (maxLength == null) {
maxLength = 32;
}
result = [];
mask = 0x01;
for (i = _i = 0; 0 <= maxLength ? _i < maxLength : _i > maxLength; i = 0 <= maxLength ? ++_i : --_i) {
bit = mask & data;
result.unshift(bit === 0 ? 0 : 1);
mask *= 2;
}
return result;
};
printArraySingle = function(arr) {
var i, string, _i, _ref;
string = "[ " + arr[0];
for (i = _i = 1, _ref = arr.length; 1 <= _ref ? _i < _ref : _i > _ref; i = 1 <= _ref ? ++_i : --_i) {
string += "," + arr[i];
}
string += " ]";
console.log(string);
return string;
};
largestPowerForNum = function(num) {
var power;
power = 0;
while (num >= 1) {
power++;
num /= 2;
}
return power;
};
simulateNetwork = function(arr) {
var pos;
if (Math.random() > 0.20) {
pos = Math.floor(Math.random() * arr.length);
arr[pos] += 1;
arr[pos] %= 2;
return pos + 1;
}
return -1;
};
generateHammingCode = function(val) {
var addToParityBits, binary, code, necBinary, pos, power;
val = parseInt(val, 10);
necBinary = largestPowerForNum(val);
binary = convertToBitArray(val, necBinary + 1);
addToParityBits = function(num, array) {
var i, largest, numBinary, power, _i, _ref, _results;
largest = largestPowerForNum(num);
numBinary = convertToBitArray(num, largest);
power = 1;
_results = [];
for (i = _i = _ref = numBinary.length - 1; _ref <= 0 ? _i <= 0 : _i >= 0; i = _ref <= 0 ? ++_i : --_i) {
if (numBinary[i] === 1) {
array[power - 1] += array[num - 1];
array[power - 1] %= 2;
}
_results.push(power *= 2);
}
return _results;
};
code = [];
power = 1;
pos = 1;
while (binary.length > 0) {
if (pos === power) {
code.push(0);
power *= 2;
} else {
code.push(binary.shift());
addToParityBits(pos, code);
}
pos++;
}
return code;
};
promptHammingCode = function(code) {
var i, labels, message, power, _i, _ref;
console.log(" -- Signal Recieved -- ");
console.log("Coded Message\n");
message = " ";
labels = " ";
power = 1;
for (i = _i = 0, _ref = code.length; 0 <= _ref ? _i < _ref : _i > _ref; i = 0 <= _ref ? ++_i : --_i) {
message += " " + code[i] + " ";
if (i + 1 === power) {
labels += " p";
power *= 2;
} else {
labels += " m";
}
labels += (i + 1) + " ";
if (i < 10) {
labels += " ";
}
}
console.log(message);
console.log(labels);
console.log("\nPlease verify the code.");
return console.log("Enter the number of the bit that was flipped (-1 if all are correct): ");
};
intro = function() {
console.log("The Hamming Story");
console.log(" One day you were sitting at your computer and chatting with");
console.log("your friends over IRC. Suddenly your network became very");
console.log("unreliable and to compensate your friends began sending messages");
console.log("to you using Hamming encodings. Unfortunetly you forgot to update");
console.log("your messaging client (again) and it cannot automatically decode");
console.log("the messages for you. Luckily you are a networks student and know");
console.log("how the code works!\n");
console.log("Translate each code as it comes across the wire by either");
console.log("verifying the message is correct or correcting the bit flipped.");
console.log("Finish them all to find out what your friends are saying to you!");
return console.log("");
};
input = process.openStdin();
prompts = 0;
NUM_PROMPTS = 10;
flippedBit = -1;
setupStep = function() {
var code, val;
if (prompts < NUM_PROMPTS) {
val = Math.floor(Math.random() * 20) + 10;
code = generateHammingCode(val);
flippedBit = simulateNetwork(code);
promptHammingCode(code);
return prompts++;
} else {
console.log("Nice job you've decoded the message!");
console.log("They say: Good luck on your midterm!");
console.log("");
console.log(" -- Terminated --");
return process.exit(0);
}
};
promptResponse = function(data) {
var val;
val = parseInt(data, 10);
if (val !== flippedBit) {
if (val === -1) {
console.log("Sorry but it looks like a bit has been flipped.\n");
} else {
console.log("That bit looks okay to me.\n");
}
return console.log("Enter the number of the bit that was flipped (-1 if all are correct): ");
} else {
console.log("Correct! Nice work\n");
return setupStep();
}
};
intro();
input.addListener('data', promptResponse);
setupStep();
}).call(this);