StrKey

StrKey is a helper class for encoding and decoding Stellar keys to/from strings. Stellar uses a base32 encoding with checksums called "strkey" for human-readable keys.

The decode contract

Every decodeX runs the same checks in the same order and reports the first one the string fails as an IllegalArgumentException:

1. the character count is one the requested type has;

2. every character is inside the ASCII range;

3. the character count leaves no partially filled trailing character;

4. every character is one of the 32 in BASE32_ALPHABET;

5. the unused trailing bits of the last character are zero;

6. the version byte names a strkey type;

7. the decoded payload has a size that type admits;

8. the framing that type defines inside its payload holds;

9. the version byte names the type the caller asked for;

10. the checksum matches the payload it covers.

Checks 2 and 4 answer one question - whether the string is written in the characters a strkey is written in - and report it in the same words. Check 5 has nothing to read for a type whose character count fills its last character, and check 8 nothing to read for a type whose payload is an opaque key of a fixed size.

Each decodeX documents only what its own type fixes: the character count it has, the version byte it is written under and the framing it defines. Each isValidX reports whether the matching decodeX accepts the string, so it is false wherever that decode throws.