CyberChef/src/core/operations/TakeBytes.mjs

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/**
* @author n1474335 [n1474335@gmail.com]
* @copyright Crown Copyright 2016
* @license Apache-2.0
*/
import Operation from "../Operation";
/**
* Take bytes operation
*/
class TakeBytes extends Operation {
/**
* TakeBytes constructor
*/
constructor() {
super();
this.name = "Take bytes";
this.module = "Default";
this.description = "Takes a slice of the specified number of bytes from the data. Negative values are allowed.";
this.inputType = "ArrayBuffer";
this.outputType = "ArrayBuffer";
this.args = [
{
"name": "Start",
"type": "number",
"value": 0
},
{
"name": "Length",
"type": "number",
"value": 5
},
{
"name": "Apply to each line",
"type": "boolean",
"value": false
}
];
}
/**
* @param {ArrayBuffer} input
* @param {Object[]} args
* @returns {ArrayBuffer}
*
* @throws {OperationError} if invalid value
*/
run(input, args) {
let start = args[0],
length = args[1];
const applyToEachLine = args[2];
if (!applyToEachLine) {
if (start < 0) { // Take from the end
start = input.byteLength + start;
}
if (length < 0) { // Flip start point
start = start + length;
if (start < 0) {
start = input.byteLength + start;
length = start - length;
} else {
length = -length;
}
}
return input.slice(start, start+length);
}
// Split input into lines
const data = new Uint8Array(input);
const lines = [];
let line = [],
i;
for (i = 0; i < data.length; i++) {
if (data[i] === 0x0a) {
lines.push(line);
line = [];
} else {
line.push(data[i]);
}
}
lines.push(line);
let output = [];
let s = start,
l = length;
for (i = 0; i < lines.length; i++) {
if (s < 0) { // Take from the end
s = lines[i].length + s;
}
if (l < 0) { // Flip start point
s = s + l;
if (s < 0) {
s = lines[i].length + s;
l = s - l;
} else {
l = -l;
}
}
output = output.concat(lines[i].slice(s, s+l));
output.push(0x0a);
s = start;
l = length;
}
return new Uint8Array(output.slice(0, output.length-1)).buffer;
}
}
export default TakeBytes;