# SCRU64: Sortable, Clock-based, Realm-specifically Unique identifier

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SCRU64 ID offers compact, time-ordered unique identifiers generated by
distributed nodes. SCRU64 has the following features:

- 63-bit non-negative integer storable as signed/unsigned 64-bit integer
- Sortable by generation time (as integer and as text)
- 12-digit case-insensitive textual representation (Base36)
- ~38-bit Unix epoch-based timestamp that ensures useful life until year 4261
- Variable-length node/machine ID and counter fields that share 24 bits

```rust
// pass node ID through environment variable
// (e.g., SCRU64_NODE_SPEC=42/8 command ...)

// generate a new identifier object
let x = scru64::new_sync();
println!("{}", x); // e.g., "0u2r85hm2pt3"
println!("{}", x.to_u64()); // as a 64-bit unsigned integer

// generate a textual representation directly
println!("{}", scru64::new_string_sync()); // e.g., "0u2r85hm2pt4"
```

See [SCRU64 Specification] for details.

SCRU64's uniqueness is realm-specific, i.e., dependent on the centralized
assignment of node ID to each generator. If you need decentralized, globally
unique time-ordered identifiers, consider [SCRU128].

[SCRU64 Specification]: https://github.com/scru64/spec
[SCRU128]: https://github.com/scru128/spec

## Crate features

Default features:

- `std` integrates the library with, among others, the system clock to draw
  current timestamps. Without `std`, this crate provides limited functionality
  available under `no_std` environments.
- `global_gen` (implies `std`) enables the `new()`, `new_string()`, `new_sync()`,
  and `new_string_sync()` primary entry point functions as well as the
  process-wide global generator under the hood.

Optional features:

- `serde` enables serialization/deserialization via serde.

## License

Licensed under the Apache License, Version 2.0.

## See also

- [docs.rs/scru64](https://docs.rs/scru64)