Add Length Value Decoder Operatoin

src/core/operations/LengthValueDecoder.mjs

@@ -0,0 +1,78 @@
+/**
+ * @author gchq77703 []
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import LengthValue from "../lib/LengthValue";
+
+/**
+ * From Length Value operation
+ */
+class FromLengthValue extends Operation {
+
+    /**
+     * FromLengthValue constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "From Length Value";
+        this.module = "Default";
+        this.description = "Converts a Length-Value (LV) encoded string into a line-delimited JSON (LDJSON / Streaming JSON) format";
+        this.infoURL = "";
+        this.inputType = "byteArray";
+        this.outputType = "string";
+        this.args = [
+            {
+                name: "Bytes in Length Value",
+                type: "populateOption",
+                value: [
+                    {
+                        name: "1 Byte",
+                        value: "1"
+                    },
+                    {
+                        name: "2 Bytes",
+                        value: "2"
+                    },
+                    {
+                        name: "4 Bytes",
+                        value: "4"
+                    }
+                ]
+            },
+            {
+                name: "Use Basic Encoding Rules",
+                type: "boolean"
+            }
+        ];
+    }
+
+    /**
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        const bytesInLength = parseInt(args[0].split(" ")[0], 10);
+        const basicEncodingRules = args[2];
+
+        const lv = new LengthValue(input, { bytesInLength, basicEncodingRules });
+
+        const data = [];
+
+        while (!lv.atEnd()) {
+            const dataLength = lv.getLength();
+            const value = lv.getValue(dataLength);
+
+            data.push(value);
+        }
+
+        return data.map(line => line.map(value => ("00" + value.toString(16)).slice(-2)).join(" ")).join("\n");
+    }
+
+}
+
+export default FromLengthValue;