ESM: Ported Base58, Base and BCD operations

src/core/lib/BCD.mjs

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+/**
+ * Binary Code Decimal resources.
+ *
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2017
+ * @license Apache-2.0
+ */
+
+/**
+ * BCD encoding schemes.
+ */
+export const 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.
+ */
+export const 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],
+};
+
+/**
+ * BCD formats.
+ */
+export const FORMAT = ["Nibbles", "Bytes", "Raw"];

src/core/lib/Base58.mjs

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+/**
+ * Base58 resources.
+ *
+ * @author tlwr [toby@toby.codes]
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2017
+ * @license Apache-2.0
+ */
+
+/**
+ * Base58 alphabet options.
+ */
+export const ALPHABET_OPTIONS = [
+    {
+        name: "Bitcoin",
+        value: "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz",
+    },
+    {
+        name: "Ripple",
+        value: "rpshnaf39wBUDNEGHJKLM4PQRST7VWXYZ2bcdeCg65jkm8oFqi1tuvAxyz",
+    },
+];