Spec doc

Author: ribasushi

rfcs/Base36.md

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+# Base36
+
+The multibase base36 prefix is the character `k` or `K`. The digit-alphabet
+consists of 0..9 and then the case insensitive range a..z for the values 10..35
+
+## Encoding
+
+A byte array is encoded to base36 by:
+
+1. Counting the number of leading 0 bytes (Z).
+2. Interpreting the rest of the byte array as a big-endian unsigned integer (N).
+3. Concatenating a length Z string of '0' characters with the decimal
+   representation of N.
+
+A byte array is encoded to multibase base36 by prefixing its base36 encoding
+with the character `k`.
+
+## Decoding
+
+A multibase base36 encoded string is decoded by first dropping the multibase
+prefix (which must be `k` or `K`).
+
+The remaining characters are then converted to a byte array by:
+
+1. Counting the number of leading '0' characters (Z).
+2. Interpreting the rest of the character sequence as a base36 unsigned integer
+   (N).
+3. Concatenating a length Z array of NULL (0x00) bytes with N encoded as a
+   big-endian unsigned integer.
+
+## Examples
+
+Byte Array <-> Base36 Multibase:
+
+|---|---|---|---|
+| `[0x00, 0x01]`       | <-> | `"k01"`   | `"K01"`   |
+| `[0x00, 0x00, 0xff]` | <-> | `"k0073"` | `"K0073"` |
+| `[0x01, 0x00]`       | <-> | `"k74"`   | `"K74"`   |
+| `[0x00, 0x01, 0x00]` | <-> | `"k074"`  | `"K074"`  |