Add Strip IPv4 header operation

src/core/operations/StripIPv4Header.mjs

@@ -0,0 +1,57 @@
+/**
+ * @author c65722 []
+ * @copyright Crown Copyright 2024
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+import Stream from "../lib/Stream.mjs";
+
+/**
+ * Strip IPv4 header operation
+ */
+class StripIPv4Header extends Operation {
+
+    /**
+     * StripIPv4Header constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Strip IPv4 header";
+        this.module = "Default";
+        this.description = "Strips the IPv4 header from an IPv4 packet, outputting the payload.";
+        this.infoURL = "https://wikipedia.org/wiki/IPv4";
+        this.inputType = "ArrayBuffer";
+        this.outputType = "ArrayBuffer";
+        this.args = [];
+    }
+
+    /**
+     * @param {ArrayBuffer} input
+     * @param {Object[]} args
+     * @returns {ArrayBuffer}
+     */
+    run(input, args) {
+        const MIN_HEADER_LEN = 20;
+
+        const s = new Stream(new Uint8Array(input));
+        if (s.length < MIN_HEADER_LEN) {
+            throw new OperationError("Input length is less than minimum IPv4 header length");
+        }
+
+        const ihl = s.readInt(1) & 0x0f;
+        const dataOffsetBytes = ihl * 4;
+        if (s.length < dataOffsetBytes) {
+            throw new OperationError("Input length is less than IHL");
+        }
+
+        s.moveTo(dataOffsetBytes);
+
+        return s.getBytes().buffer;
+    }
+
+}
+
+export default StripIPv4Header;