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system/node_modules/ethers/src.ts/utils/base58.ts

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+/**
+ *  The [Base58 Encoding](link-base58) scheme allows a **numeric** value
+ *  to be encoded as a compact string using a radix of 58 using only
+ *  alpha-numeric characters. Confusingly similar characters are omitted
+ *  (i.e. ``"l0O"``).
+ *
+ *  Note that Base58 encodes a **numeric** value, not arbitrary bytes,
+ *  since any zero-bytes on the left would get removed. To mitigate this
+ *  issue most schemes that use Base58 choose specific high-order values
+ *  to ensure non-zero prefixes.
+ *
+ *  @_subsection: api/utils:Base58 Encoding [about-base58]
+ */
+
+import { getBytes } from "./data.js";
+import { assertArgument } from "./errors.js";
+import { toBigInt } from "./maths.js";
+
+import type { BytesLike } from "./index.js";
+
+
+const Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+let Lookup: null | Record<string, bigint> = null;
+
+function getAlpha(letter: string): bigint {
+    if (Lookup == null) {
+        Lookup = { };
+        for (let i = 0; i < Alphabet.length; i++) {
+            Lookup[Alphabet[i]] = BigInt(i);
+        }
+    }
+    const result = Lookup[letter];
+    assertArgument(result != null, `invalid base58 value`, "letter", letter);
+    return result;
+}
+
+
+const BN_0 = BigInt(0);
+const BN_58 = BigInt(58);
+
+/**
+ *  Encode %%value%% as a Base58-encoded string.
+ */
+export function encodeBase58(_value: BytesLike): string {
+    const bytes = getBytes(_value);
+
+    let value = toBigInt(bytes);
+    let result = "";
+    while (value) {
+        result = Alphabet[Number(value % BN_58)] + result;
+        value /= BN_58;
+    }
+
+    // Account for leading padding zeros
+    for (let i = 0; i < bytes.length; i++) {
+        if (bytes[i]) { break; }
+        result = Alphabet[0] + result;
+    }
+
+    return result;
+}
+
+/**
+ *  Decode the Base58-encoded %%value%%.
+ */
+export function decodeBase58(value: string): bigint {
+    let result = BN_0;
+    for (let i = 0; i < value.length; i++) {
+        result *= BN_58;
+        result += getAlpha(value[i]);
+    }
+    return result;
+}