/**
* Bit rotation operations.
*
* @author n1474335 [n1474335@gmail.com]
* @copyright Crown Copyright 2016
* @license Apache-2.0
*
* @namespace
*
* @todo Support for UTF16
*/
var Rotate = {
/**
* @constant
* @default
*/
ROTATE_AMOUNT: 1,
/**
* @constant
* @default
*/
ROTATE_WHOLE: false,
/**
* Runs rotation operations across the input data.
*
* @private
* @param {byte_array} data
* @param {number} amount
* @param {function} algo - The rotation operation to carry out
* @returns {byte_array}
*/
_rot: function(data, amount, algo) {
var result = [];
for (var i = 0; i < data.length; i++) {
var b = data[i];
for (var j = 0; j < amount; j++) {
b = algo(b);
}
result.push(b);
}
return result;
},
/**
* Rotate right operation.
*
* @param {byte_array} input
* @param {Object[]} args
* @returns {byte_array}
*/
run_rotr: function(input, args) {
if (args[1]) {
return Rotate._rotr_whole(input, args[0]);
} else {
return Rotate._rot(input, args[0], Rotate._rotr);
}
},
/**
* Rotate left operation.
*
* @param {byte_array} input
* @param {Object[]} args
* @returns {byte_array}
*/
run_rotl: function(input, args) {
if (args[1]) {
return Rotate._rotl_whole(input, args[0]);
} else {
return Rotate._rot(input, args[0], Rotate._rotl);
}
},
/**
* @constant
* @default
*/
ROT13_AMOUNT: 13,
/**
* @constant
* @default
*/
ROT13_LOWERCASE: true,
/**
* @constant
* @default
*/
ROT13_UPPERCASE: true,
/**
* ROT13 operation.
*
* @param {byte_array} input
* @param {Object[]} args
* @returns {byte_array}
*/
run_rot13: function(input, args) {
var amount = args[2],
output = input,
chr,
rot13_lowercase = args[0],
rot13_upperacse = args[1];
if (amount) {
if (amount < 0) {
amount = 26 - (Math.abs(amount) % 26);
}
for (var i = 0; i < input.length; i++) {
chr = input[i];
if (rot13_upperacse && chr >= 65 && chr <= 90) { // Upper case
chr = (chr - 65 + amount) % 26;
output[i] = chr + 65;
} else if (rot13_lowercase && chr >= 97 && chr <= 122) { // Lower case
chr = (chr - 97 + amount) % 26;
output[i] = chr + 97;
}
}
}
return output;
},
/**
* Rotate right bitwise op.
*
* @private
* @param {byte} b
* @returns {byte}
*/
_rotr: function(b) {
var bit = (b & 1) << 7;
return (b >> 1) | bit;
},
/**
* Rotate left bitwise op.
*
* @private
* @param {byte} b
* @returns {byte}
*/
_rotl: function(b) {
var bit = (b >> 7) & 1;
return ((b << 1) | bit) & 0xFF;
},
/**
* Rotates a byte array to the right by a specific amount as a whole, so that bits are wrapped
* from the end of the array to the beginning.
*
* @private
* @param {byte_array} data
* @param {number} amount
* @returns {byte_array}
*/
_rotr_whole: function(data, amount) {
var carry_bits = 0,
new_byte,
result = [];
amount = amount % 8;
for (var i = 0; i < data.length; i++) {
var old_byte = data[i] >>> 0;
new_byte = (old_byte >> amount) | carry_bits;
carry_bits = (old_byte & (Math.pow(2, amount)-1)) << (8-amount);
result.push(new_byte);
}
result[0] |= carry_bits;
return result;
},
/**
* Rotates a byte array to the left by a specific amount as a whole, so that bits are wrapped
* from the beginning of the array to the end.
*
* @private
* @param {byte_array} data
* @param {number} amount
* @returns {byte_array}
*/
_rotl_whole: function(data, amount) {
var carry_bits = 0,
new_byte,
result = [];
amount = amount % 8;
for (var i = data.length-1; i >= 0; i--) {
var old_byte = data[i];
new_byte = ((old_byte << amount) | carry_bits) & 0xFF;
carry_bits = (old_byte >> (8-amount)) & (Math.pow(2, amount)-1);
result[i] = (new_byte);
}
result[data.length-1] = result[data.length-1] | carry_bits;
return result;
},
};
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