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// repository documentation

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# Universally Unique Lexicographically Sortable Identifier

## This page was copied from https://github.com/alizain/ulid

## The code was ported to python from https://github.com/alizain/ulid

## Converted to Python (2 and 3) by Massimo Di Pierro

UUID can be suboptimal for many uses-cases because:

- It isn't the most character efficient way of encoding 128 bits of randomness
- The string format itself is apparently based on the original MAC & time version (UUIDv1 from Wikipedia)
- It provides no other information than randomness

Instead, herein is proposed ULID:

- 128-bit compatibility with UUID
- 1.21e+24 unique ULIDs per millisecond
- Lexicographically sortable!
- Canonically encoded as a 26 character string, as opposed to the 36 character UUID
- Uses Crockford's base32 for better efficiency and readability (5 bits per character)
- Case insensitive
- No special characters (URL safe)

### Install

```
pip install ulid
```

### Usage

```
import ulid
print ulid.ulid()
```

Below is the current specification of ULID as implemented in this repository. *Note: the binary format has not been implemented.*

```
 01AN4Z07BY      79KA1307SR9X4MV3

|----------|    |----------------|
 Timestamp          Randomness
  10 chars           16 chars
   48bits             80bits
   base32             base32
```

### Components

**Timestamp**
- 48 bit integer
- UNIX-time in milliseconds
- Won't run out of space till the year 10895 AD.

**Randomness**
- 80 bits
- Cryptographically secure source of randomness, if possible

### Sorting

The left-most character must be sorted first, and the right-most character sorted last. The default ASCII order is used for sorting.

### Binary Layout and Byte Order

The components are encoded as 16 octets. Each component is encoded with the Most Significant Byte first (network byte order).

```
0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      32_bit_uint_time_low                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     16_bit_uint_time_high     |       16_bit_uint_random      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       32_bit_uint_random                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       32_bit_uint_random                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
```

### String Representation

```
ttttttttttrrrrrrrrrrrrrrrr

where
t is Timestamp
r is Randomness
```

## Test Suite

## Performance

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