ESM: Ported MS and Entropy operations

src/core/operations/FrequencyDistribution.mjs

@@ -0,0 +1,110 @@
+/**
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2016
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import Utils from "../Utils";
+import OperationError from "../errors/OperationError";
+
+/**
+ * Frequency distribution operation
+ */
+class FrequencyDistribution extends Operation {
+
+    /**
+     * FrequencyDistribution constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Frequency distribution";
+        this.module = "Default";
+        this.description = "Displays the distribution of bytes in the data as a graph.";
+        this.inputType = "ArrayBuffer";
+        this.outputType = "json";
+        this.presentType = "html";
+        this.args = [
+            {
+                "name": "Show 0%s",
+                "type": "boolean",
+                "value": "Entropy.FREQ_ZEROS"
+            }
+        ];
+    }
+
+    /**
+     * @param {ArrayBuffer} input
+     * @param {Object[]} args
+     * @returns {json}
+     */
+    run(input, args) {
+        const data = new Uint8Array(input);
+        if (!data.length) throw new OperationError("No data");
+
+        const distrib = new Array(256).fill(0),
+            percentages = new Array(256),
+            len = data.length;
+        let i;
+
+        // Count bytes
+        for (i = 0; i < len; i++) {
+            distrib[data[i]]++;
+        }
+
+        // Calculate percentages
+        let repr = 0;
+        for (i = 0; i < 256; i++) {
+            if (distrib[i] > 0) repr++;
+            percentages[i] = distrib[i] / len * 100;
+        }
+
+        return {
+            "dataLength": len,
+            "percentages": percentages,
+            "distribution": distrib,
+            "bytesRepresented": repr
+        };
+    }
+
+    /**
+     * Displays the frequency distribution as a bar chart for web apps.
+     *
+     * @param {json} freq
+     * @returns {html}
+     */
+    present(freq, args) {
+        const showZeroes = args[0];
+        // Print
+        let output = `<canvas id='chart-area'></canvas><br>
+Total data length: ${freq.dataLength}
+Number of bytes represented: ${freq.bytesRepresented}
+Number of bytes not represented: ${256 - freq.bytesRepresented}
+
+Byte   Percentage
+<script>
+    var canvas = document.getElementById("chart-area"),
+        parentRect = canvas.parentNode.getBoundingClientRect(),
+        scores = ${JSON.stringify(freq.percentages)};
+
+    canvas.width = parentRect.width * 0.95;
+    canvas.height = parentRect.height * 0.9;
+
+    CanvasComponents.drawBarChart(canvas, scores, "Byte", "Frequency %", 16, 6);
+</script>`;
+
+        for (let i = 0; i < 256; i++) {
+            if (freq.distribution[i] || showZeroes) {
+                output += " " + Utils.hex(i, 2) + "    (" +
+                    (freq.percentages[i].toFixed(2).replace(".00", "") + "%)").padEnd(8, " ") +
+                    Array(Math.ceil(freq.percentages[i])+1).join("|") + "\n";
+            }
+        }
+
+        return output;
+    }
+
+}
+
+export default FrequencyDistribution;