Add 'Drop nth bytes' operation

src/core/config/Categories.json

@@ -320,7 +320,8 @@
  "Unescape string",
  "Pseudo-Random Number Generator",
  "Sleep",
- "File Tree"
+ "File Tree",
+ "Drop nth bytes"
  ]
  },
  {

src/core/operations/DropNthBytes.mjs

@@ -0,0 +1,79 @@
+/**
+ * @author Oshawk [[email protected]]
+ * @copyright Crown Copyright 2019
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+
+/**
+ * Drop nth bytes operation
+ */
+class DropNthBytes extends Operation {
+
+ /**
+ * DropNthBytes constructor
+ */
+ constructor() {
+ super();
+
+ this.name = "Drop nth bytes";
+ this.module = "Default";
+ this.description = "Drops every nth byte starting with a given byte.";
+ this.infoURL = "";
+ this.inputType = "byteArray";
+ this.outputType = "byteArray";
+ this.args = [
+ {
+ name: "Drop every",
+ type: "number",
+ value: 4
+ },
+ {
+ name: "Starting at",
+ type: "number",
+ value: 0
+ },
+ {
+ name: "Apply to each line",
+ type: "boolean",
+ value: false
+ }
+ ];
+ }
+
+ /**
+ * @param {byteArray} input
+ * @param {Object[]} args
+ * @returns {byteArray}
+ */
+ run(input, args) {
+ const n = args[0];
+ const start = args[1];
+ const eachLine = args[2];
+
+ if (parseInt(n, 10) !== n || n <= 0) {
+ throw new OperationError("'Drop every' must be a positive integer.");
+ }
+ if (parseInt(start, 10) !== start || start < 0) {
+ throw new OperationError("'Starting at' must be a positive or zero integer.");
+ }
+
+ let offset = 0;
+ const output = [];
+ for (let i = 0; i < input.length; i++) {
+ if (eachLine && input[i] === 0x0a) {
+ output.push(0x0a);
+ offset = i + 1;
+ } else if (i - offset < start || (i - (start + offset)) % n !== 0) {
+ output.push(input[i]);
+ }
+ }
+
+ return output;
+ }
+
+}
+
+export default DropNthBytes;

tests/operations/index.mjs

@@ -59,6 +59,7 @@ import "./tests/Crypt.mjs";
 import "./tests/CSV.mjs";
 import "./tests/DateTime.mjs";
 import "./tests/DefangIP.mjs";
+import "./tests/DropNthBytes.mjs";
 import "./tests/ECDSA.mjs";
 import "./tests/ELFInfo.mjs";
 import "./tests/Enigma.mjs";

tests/operations/tests/DropNthBytes.mjs

@@ -0,0 +1,123 @@
+/**
+ * @author Oshawk [[email protected]]
+ * @copyright Crown Copyright 2019
+ * @license Apache-2.0
+ */
+
+import TestRegister from "../../lib/TestRegister.mjs";
+
+/**
+ * Drop nth bytes tests
+ */
+TestRegister.addTests([
+ {
+ name: "Drop nth bytes: Nothing",
+ input: "",
+ expectedOutput: "",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 0, false],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Nothing (apply to each line)",
+ input: "",
+ expectedOutput: "",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 0, true],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Basic single line",
+ input: "0123456789",
+ expectedOutput: "1235679",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 0, false],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Basic single line (apply to each line)",
+ input: "0123456789",
+ expectedOutput: "1235679",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 0, true],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Complex single line",
+ input: "0123456789",
+ expectedOutput: "01234678",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 5, false],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Complex single line (apply to each line)",
+ input: "0123456789",
+ expectedOutput: "01234678",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 5, true],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Basic multi line",
+ input: "01234\n56789",
+ expectedOutput: "123\n5689",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 0, false],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Basic multi line (apply to each line)",
+ input: "01234\n56789",
+ expectedOutput: "123\n678",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 0, true],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Complex multi line",
+ input: "01234\n56789",
+ expectedOutput: "012345679",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 5, false],
+ },
+ ],
+ },
+ {
+ name: "Drop nth bytes: Complex multi line (apply to each line)",
+ input: "012345\n6789ab",
+ expectedOutput: "01234\n6789a",
+ recipeConfig: [
+ {
+ op: "Drop nth bytes",
+ args: [4, 5, true],
+ },
+ ],
+ }
+]);