Awesome

libxid

A globally unique id generator.

This is a c++ implementation of the Golang package found at: https://github.com/rs/xid

Xid uses MongoDB Object ID algorighm¹ to generate globally unique ids with base32 serialzation to produce shorter strings.

Binary representation

+---+----+----+----+----+----+----+----+----+----+-----+-----+
| 0 |  1 |  2 |  3 |  4 |  5 |  6 |  7 |  8 |  9 |  10 |  11 |
+---+----+----+----+----+----+----+----+----+----+-----+-----+
 \----- time -----/ \ machine id / \- pid -/ \--- counter ---/

• 4-byte value representing the seconds since the Unix epoch,
• 3-byte machine identifier,
• 2-byte process id, and
• 3-byte counter, starting with a random value.

The binary representation of the id is compatible with MongoDB's 12 bytes Object IDs. The string representation is using base32hex (w/o padding)² for better space efficiency when stored in string form (20 bytes). The hex variant of base32 is used to retain the sortable property of the id.

Features

• Size: 12 bytes (96 bits), smaller than UUID, larger than Twitter Snowflake³
• Base32hex encoded by default (20 chars when transported as printable string, still sortable)
• Configuration free: there is no need to set a unique machine and/or data center id
• K-ordered
• Embedded time with 1 second precision
• Unicity guaranteed for 16,777,216 (24 bits) unique ids per second and per host/process
• Lock-free (unlike UUIDv1 and v2)

Comparison

Install

CMake

include(FetchContent)

#libxid
FetchContent_Declare(libxid
  URL      https://github.com/uatuko/libxid/archive/refs/tags/v0.1.0.tar.gz
  URL_HASH SHA256=31589bb5274c9d25a8b6c49ee04a6c76151f10082e7feb13314be02a4b2d58c8
)
FetchContent_MakeAvailable(libxid)

target_link_libraries(<target>
  PRIVATE
    libxid::xid
)

Usage

#include <xid/xid.h>

auto id = xid::next(); // generate the next id
std::string s = xid::next(); // generate the next id and convert it to a string

// Get embedded info
auto id = xid::next();

id.time();
id.machine();
id.pid();
id.counter();

// Decode id strings
auto id = xid::id("cc0a2mn6i1e6brmdbip0");
auto bytes = xid::id::decode("cc0aar76i1e6jr6no620");