Added BCD operations with tests

src/core/config/Categories.js

@@ -46,6 +46,8 @@ const Categories = [
             "From Base58",
             "To Base",
             "From Base",
+            "To BCD",
+            "From BCD",
             "To HTML Entity",
             "From HTML Entity",
             "URL Encode",

src/core/config/OperationConfig.js

@@ -2,6 +2,7 @@ import FlowControl from "../FlowControl.js";
 import Base from "../operations/Base.js";
 import Base58 from "../operations/Base58.js";
 import Base64 from "../operations/Base64.js";
+import BCD from "../operations/BCD.js";
 import BitwiseOp from "../operations/BitwiseOp.js";
 import ByteRepr from "../operations/ByteRepr.js";
 import CharEnc from "../operations/CharEnc.js";
@@ -3507,6 +3508,64 @@ const OperationConfig = {
             }
         ]
     },
+    "From BCD": {
+        description: "Binary-Coded Decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four or eight. Special bit patterns are sometimes used for a sign.",
+        run: BCD.runFromBCD,
+        inputType: "string",
+        outputType: "number",
+        args: [
+            {
+                name: "Scheme",
+                type: "option",
+                value: BCD.ENCODING_SCHEME
+            },
+            {
+                name: "Packed",
+                type: "boolean",
+                value: true
+            },
+            {
+                name: "Signed",
+                type: "boolean",
+                value: false
+            },
+            {
+                name: "Input format",
+                type: "option",
+                value: BCD.FORMAT
+            }
+        ]
+
+    },
+    "To BCD": {
+        description: "Binary-Coded Decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four or eight. Special bit patterns are sometimes used for a sign",
+        run: BCD.runToBCD,
+        inputType: "number",
+        outputType: "string",
+        args: [
+            {
+                name: "Scheme",
+                type: "option",
+                value: BCD.ENCODING_SCHEME
+            },
+            {
+                name: "Packed",
+                type: "boolean",
+                value: true
+            },
+            {
+                name: "Signed",
+                type: "boolean",
+                value: false
+            },
+            {
+                name: "Output format",
+                type: "option",
+                value: BCD.FORMAT
+            }
+        ]
+
+    },
 };
 
 export default OperationConfig;

src/core/operations/BCD.js

@@ -0,0 +1,214 @@
+import Utils from "../Utils.js";
+
+
+/**
+ * Binary-Coded Decimal operations.
+ *
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2017
+ * @license Apache-2.0
+ *
+ * @namespace
+ */
+const BCD = {
+
+    /**
+     * @constant
+     * @default
+     */
+    ENCODING_SCHEME: [
+        "8 4 2 1",
+        "7 4 2 1",
+        "4 2 2 1",
+        "2 4 2 1",
+        "8 4 -2 -1",
+        "Excess-3",
+        "IBM 8 4 2 1",
+    ],
+
+    /**
+     * Lookup table for the binary value of each digit representation.
+     *
+     * I wrote a very nice algorithm to generate 8 4 2 1 encoding programatically,
+     * but unfortunately it's much easier (if less elegant) to use lookup tables
+     * when supporting multiple encoding schemes.
+     *
+     * "Practicality beats purity" - PEP 20
+     *
+     * In some schemes it is possible to represent the same value in multiple ways.
+     * For instance, in 4 2 2 1 encoding, 0100 and 0010 both represent 2. Support
+     * has not yet been added for this.
+     *
+     * @constant
+     */
+    ENCODING_LOOKUP: {
+        "8 4 2 1":     [0,  1,  2,  3,  4,  5,  6,  7,  8,  9],
+        "7 4 2 1":     [0,  1,  2,  3,  4,  5,  6,  8,  9,  10],
+        "4 2 2 1":     [0,  1,  4,  5,  8,  9,  12, 13, 14, 15],
+        "2 4 2 1":     [0,  1,  2,  3,  4,  11, 12, 13, 14, 15],
+        "8 4 -2 -1":   [0,  7,  6,  5,  4,  11, 10, 9,  8,  15],
+        "Excess-3":    [3,  4,  5,  6,  7,  8,  9,  10, 11, 12],
+        "IBM 8 4 2 1": [10, 1,  2,  3,  4,  5,  6,  7,  8,  9],
+    },
+
+    /**
+     * @default
+     * @constant
+     */
+    FORMAT: ["Nibbles", "Bytes", "Raw"],
+
+
+    /**
+     * To BCD operation.
+     *
+     * @param {number} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    runToBCD: function(input, args) {
+        if (isNaN(input))
+            return "Invalid input";
+        if (Math.floor(input) !== input)
+            return "Fractional values are not supported by BCD";
+
+        const encoding = BCD.ENCODING_LOOKUP[args[0]],
+            packed = args[1],
+            signed = args[2],
+            outputFormat = args[3];
+
+        // Split input number up into separate digits
+        const digits = input.toString().split("");
+
+        if (digits[0] === "-" || digits[0] === "+") {
+            digits.shift();
+        }
+
+        let nibbles = [];
+
+        digits.forEach(d => {
+            const n = parseInt(d, 10);
+            nibbles.push(encoding[n]);
+        });
+
+        if (signed) {
+            if (packed && digits.length % 2 === 0) {
+                // If there are an even number of digits, we add a leading 0 so
+                // that the sign nibble doesn't sit in its own byte, leading to
+                // ambiguity around whether the number ends with a 0 or not.
+                nibbles.unshift(encoding[0]);
+            }
+
+            nibbles.push(input > 0 ? 12 : 13);
+            // 12 ("C") for + (credit)
+            // 13 ("D") for - (debit)
+        }
+
+        let bytes = [];
+
+        if (packed) {
+            let encoded = 0,
+                little = false;
+
+            nibbles.forEach(n => {
+                encoded ^= little ? n : (n << 4);
+                if (little) {
+                    bytes.push(encoded);
+                    encoded = 0;
+                }
+                little = !little;
+            });
+
+            if (little) bytes.push(encoded);
+        } else {
+            bytes = nibbles;
+
+            // Add null high nibbles
+            nibbles = nibbles.map(n => {
+                return [0, n];
+            }).reduce((a, b) => {
+                return a.concat(b);
+            });
+        }
+
+        // Output
+        switch (outputFormat) {
+            case "Nibbles":
+                return nibbles.map(n => {
+                    return Utils.padLeft(n.toString(2), 4);
+                }).join(" ");
+            case "Bytes":
+                return bytes.map(b => {
+                    return Utils.padLeft(b.toString(2), 8);
+                }).join(" ");
+            case "Raw":
+            default:
+                return Utils.byteArrayToChars(bytes);
+        }
+    },
+
+
+    /**
+     * From BCD operation.
+     *
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {number}
+     */
+    runFromBCD: function(input, args) {
+        const encoding = BCD.ENCODING_LOOKUP[args[0]],
+            packed = args[1],
+            signed = args[2],
+            inputFormat = args[3];
+
+        let nibbles = [],
+            output = "",
+            byteArray;
+
+        // Normalise the input
+        switch (inputFormat) {
+            case "Nibbles":
+            case "Bytes":
+                input = input.replace(/\s/g, "");
+                for (let i = 0; i < input.length; i += 4) {
+                    nibbles.push(parseInt(input.substr(i, 4), 2));
+                }
+                break;
+            case "Raw":
+            default:
+                byteArray = Utils.strToByteArray(input);
+                byteArray.forEach(b => {
+                    nibbles.push(b >>> 4);
+                    nibbles.push(b & 15);
+                });
+                break;
+        }
+
+        if (!packed) {
+            // Discard each high nibble
+            for (let i = 0; i < nibbles.length; i++) {
+                nibbles.splice(i, 1);
+            }
+        }
+
+        if (signed) {
+            const sign = nibbles.pop();
+            if (sign === 13 ||
+                sign === 11) {
+                // Negative
+                output += "-";
+            }
+        }
+
+        nibbles.forEach(n => {
+            if (isNaN(n)) throw "Invalid input";
+            let val = encoding.indexOf(n);
+            if (val < 0) throw `Value ${Utils.bin(n, 4)} not in encoding scheme`;
+            output += val.toString();
+        });
+
+        return parseInt(output, 10);
+    },
+
+};
+
+export default BCD;