Salts longer than 42 characters are truncated

[langelgjm]

After installing plpg_hashids, I do the following:

SELECT hashids.encode(1001, 'the salt goes here and has some maximum l') = hashids.encode(1001, 'the salt goes here and has some maximum le');
-- false, as expected: different salts produce different hashes

SELECT hashids.encode(1001, 'the salt goes here and has some maximum le') = hashids.encode(1001, 'the salt goes here and has some maximum len');
-- true, unexpected: different salts produce the same hash

Database version:
PostgreSQL 9.6.15 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.3 20140911 (Red Hat 4.8.3-9), 64-bit (AWS RDS)

I took a quick look through the code and didn't see anything obvious that would cause this, but will try to narrow down the cause.