[wip] add untested base58 encode in ts

2022-10-21 04:47:55 -06:00
parent 0e600f0f05
commit aa9b8b7339
4 changed files with 575 additions and 11 deletions
@@ -0,0 +1,188 @@
+/**
+ * Base58 encoding/decoding
+ */
+
+export {
+    encode
+    // decode
+}
+
+
+
+//=============================================================================
+// ENCODING
+//=============================================================================
+
+/**
+ * Encode a Uint8Array into base58
+ */
+function
+encode(binary : Uint8Array): string {
+    let num_leading_zeros : number     = nlz(binary);
+    let rest              : Uint8Array = binary.slice(num_leading_zeros);
+    let ones              : string     = encode_zeros(num_leading_zeros);
+    let rest_b58          : string     = encode_rest(rest);
+    let result            : string     = ones + rest_b58;
+    return result;
+}
+
+
+
+/**
+ * count the number of leading zeros in a uint8array
+ *
+ * @internal
+ */
+function
+nlz(bytes: Uint8Array): number {
+    let n = 0;
+    for (let this_byte of bytes) {
+        if (0 === this_byte)
+            n++;
+        else
+            break;
+    }
+    return n;
+}
+
+
+/**
+ * Generate a bunch of '1's for however many leading zeros there are
+ *
+ * @internal
+ */
+function
+encode_zeros(how_many : number): string {
+    let ones : string = '';
+    for (let i  = 1;
+             i <= how_many;
+             i++)
+    {
+        ones += '1';
+    }
+
+    return ones;
+}
+
+
+
+/**
+ * Encode a Uint8Array that has no leading zeros
+ *
+ * @internal
+ */
+function
+encode_rest(bytes : Uint8Array): string {
+    let bytes_bignum : bigint = bytes_to_bigint(bytes);
+    let result       : string = bignum_to_base58(bytes_bignum);
+    return result;
+}
+
+
+
+/**
+ * Convert a bytestring to a bignum
+ *
+ * @internal
+ */
+function
+bytes_to_bigint(bytes: Uint8Array): bigint {
+    let acc_bigint : bigint = 0n;
+    for(let this_byte of bytes) {
+        acc_bigint <<= 8n;
+        acc_bigint  += BigInt(this_byte);
+    }
+    return acc_bigint;
+}
+
+
+
+/**
+ * Convert a BigInt to Base58
+ *
+ * @internal
+ */
+function
+bignum_to_base58(q: bigint) {
+    let s = '';
+    while (q !== 0n) {
+        let this_n        : bigint = q % 58n;
+        q /= 58n;
+
+        let this_b58_char : string = bigint_to_char(this_n);
+        s = this_b58_char + s;
+    }
+    return s;
+}
+
+
+
+//=============================================================================
+// TRANSLATION TABLES
+//=============================================================================
+
+function
+bigint_to_char(n: bigint) {
+    switch(n) {
+        case  0n: return '1';
+        case  1n: return '2';
+        case  2n: return '3';
+        case  3n: return '4';
+        case  4n: return '5';
+        case  5n: return '6';
+        case  6n: return '7';
+        case  7n: return '8';
+        case  8n: return '9';
+        case  9n: return 'A';
+        case 10n: return 'B';
+        case 11n: return 'C';
+        case 12n: return 'D';
+        case 13n: return 'E';
+        case 14n: return 'F';
+        case 15n: return 'G';
+        case 16n: return 'H';
+        case 17n: return 'J';
+        case 18n: return 'K';
+        case 19n: return 'L';
+        case 20n: return 'M';
+        case 21n: return 'N';
+        case 22n: return 'P';
+        case 23n: return 'Q';
+        case 24n: return 'R';
+        case 25n: return 'S';
+        case 26n: return 'T';
+        case 27n: return 'U';
+        case 28n: return 'V';
+        case 29n: return 'W';
+        case 30n: return 'X';
+        case 31n: return 'Y';
+        case 32n: return 'Z';
+        case 33n: return 'a';
+        case 34n: return 'b';
+        case 35n: return 'c';
+        case 36n: return 'd';
+        case 37n: return 'e';
+        case 38n: return 'f';
+        case 39n: return 'g';
+        case 40n: return 'h';
+        case 41n: return 'i';
+        case 42n: return 'j';
+        case 43n: return 'k';
+        case 44n: return 'm';
+        case 45n: return 'n';
+        case 46n: return 'o';
+        case 47n: return 'p';
+        case 48n: return 'q';
+        case 49n: return 'r';
+        case 50n: return 's';
+        case 51n: return 't';
+        case 52n: return 'u';
+        case 53n: return 'v';
+        case 54n: return 'w';
+        case 55n: return 'x';
+        case 56n: return 'y';
+        case 57n: return 'z';
+        default:
+            throw new Error('invalid base58 bigint: ' + n)
+    }
+}