data.ulid- Universally unique lexicographically sortable identifier
This module implements ULID (https://github.com/ulid/spec), a UUID-like unique identifier that can be sortable in chronological order and has slightly more compact string representation.
(define gen-ulid (make-ulid-generator)) (gen-ulid) ⇒ #<ulid 01G70P3EWJT28VPQ12NTFFDSZ1> (ulid->string (gen-ulid)) ⇒ "01G70P3Y72TQ1HYY90G8TJSY07"
Creates and returns a generator that yields a fresh ULID object
every time it is called. The optional random-source argument
is a SRFI-27 random source (see
srfi.27 - Sources of Random Bits)
to be used for the random part of ULID. When omitted,
an internal random source is used.
To guarantee uniqueness and monotonicity, a ULID generator needs to keep internal state. If you want to share the generator among multiple threads, you need to manage your own lock. Keeping the generator private in one thread eliminates the need of mutex (however, monotonicity is only guaranteed within each generator).
A ULID consists of 48bit timestamp field (milliseconds since Unix epoch) and 80bit randomness field. The randomness field are generated randomly if it is the first ULID within the timestamp. If more than one ULID needs to be generated in a millisecond window, the subsequent ULID gets randomness field incremented from the previous ULID, so that the chronological order is maintained.
The ULID spec says if the randomness field overflows because so many ULIDs are generated within a millisecond, it is an error. Such scenario is very unlikely but can occur. In our implementation, however, we wait for the next millisecond boundary in case we ran out randomness field, so the generator never yields an error.
#t iff obj is an ULID object.
Returns the timestamp part of ulid (48bits) as an exact integer.
Returns the randomess part of ulid (80bits) as an exact integer.
Returns true if two ULIDs are equivalent.
Returns true if ulid1 precedes ulid2. If both ULIDs are created from the same generator, this means ulid1 is created chronologically before ulid2. If they are created from different generators, the chronological order is not guaranteed, but the discrepancy only occurs when two ULIDs are created at the same timestamp in millisecond resolution.
Returns a hash value of ulid in a nonnegative exact integer.
Bound to a comparator suitable to compare and hash ULIDs.
Covvert between ulid and a u8vector of length 16. Bits are packed in big-endian order (first 8 bits of timestamp to first byte, and so on).
Convert between ulid and an exact nonnegative integer up to 128bit.
Convert ulid to a string of Base32 representation; the
U are excluded to avoid confusion). Length of
the string is always 26.
ulid->string always use uppercase characters; on the other hand,
string->ulid allows both lowercase and uppercase characters.