UnQLite

UnQLite is a self-contained, serverless, transactional database engine for C and C++ applications.

It runs in-process, stores data in a single portable file, and ships as a small embed-friendly codebase with no external runtime dependency. UnQLite exposes two layers:

a raw key/value store for binary-safe records
a document store powered by the Jx9 embedded scripting language

Official website: https://unqlite.symisc.net/

Current public release: 1.2.1

Why UnQLite

Embedded: no separate daemon, no socket protocol, no service to deploy
Transactional: ACID semantics for local storage workloads
Simple distribution: a database is typically one file on disk
Portable: the file format is cross-platform
Flexible: use key/value APIs directly, or use the document store and Jx9 layer
Small integration surface: the recommended embed path is the amalgamation
Optional threading support: enable it at compile time with UNQLITE_ENABLE_THREADS

Recommended Integration Path

If you want the simplest and most stable embed story, use the amalgamation files at the repository root:

unqlite.c
unqlite.h

That is the intended drop-in path for production embedding.

The src/ directory contains the split source tree used to build and maintain the amalgamation.

Repository Layout

unqlite.c: amalgamated implementation
unqlite.h: public header for the amalgamation build
src/: split source tree and internal headers
samples/: small example programs
CHANGELOG.md: release notes
LICENSE: 2-Clause BSD license

Quick Start

The fastest way to embed UnQLite is to compile your application together with unqlite.c.

GCC or Clang

sh
cc -O2 -std=c99 -I. your_app.c unqlite.c -o your_app

Compile the bundled key/value intro sample:

sh
cc -O2 -std=c99 -I. samples/1.c unqlite.c -o unqlite_kv_intro

MSVC

bat
cl /nologo /TC /I. your_app.c unqlite.c

Compile the bundled key/value intro sample:

bat
cl /nologo /TC /I. samples\1.c unqlite.c /link /OUT:unqlite_kv_intro.exe

Threading Support

If your application needs UnQLite compiled with thread support, define UNQLITE_ENABLE_THREADS when building:

sh
cc -O2 -std=c99 -DUNQLITE_ENABLE_THREADS -I. your_app.c unqlite.c -o your_app

bat
cl /nologo /TC /DUNQLITE_ENABLE_THREADS /I. your_app.c unqlite.c

Minimal Example

c
#include "unqlite.h"
#include <stdio.h>

static int print_value(const void *data, unsigned int len, void *user_data) {
    (void)user_data;
    fwrite(data, 1, len, stdout);
    return UNQLITE_OK;
}

int main(void) {
    unqlite *db = 0;

    if (unqlite_open(&db, ":mem:", UNQLITE_OPEN_CREATE) != UNQLITE_OK) {
        return 1;
    }

    if (unqlite_kv_store(db, "hello", -1, "world", 5) != UNQLITE_OK) {
        unqlite_close(db);
        return 1;
    }

    if (unqlite_kv_fetch_callback(db, "hello", -1, print_value, 0) != UNQLITE_OK) {
        unqlite_close(db);
        return 1;
    }

    putchar('\n');
    return unqlite_close(db) == UNQLITE_OK ? 0 : 1;
}

If you only need embedded key/value storage, you can stay entirely within the unqlite_kv_* API family and ignore the document-store layer.

What UnQLite Includes

On-disk and in-memory databases
Key/value CRUD APIs
Cursor APIs for linear traversal
A pluggable storage engine model
A document store built on Jx9
Foreign function and constant binding for Jx9 code
A virtual file system abstraction for portability

Samples

The samples/ directory contains small, focused examples for common integration paths.

Useful starting points:

samples/1.c: key/value introduction
samples/2.c through samples/6.c: broader API usage
samples/unqlite_huge.c: large-value handling
samples/unqlite_tar.c: archive-oriented example
samples/unqlite_mp3.c: metadata-oriented example

Documentation

The official documentation lives on the new site:

Homepage: https://unqlite.symisc.net/
Downloads: https://unqlite.symisc.net/downloads.html
UnQLite in 5 Minutes or Less: https://unqlite.symisc.net/intro.html
C/C++ API introduction: https://unqlite.symisc.net/api_intro.html
C/C++ API reference: https://unqlite.symisc.net/c_api.html
Cursor reference: https://unqlite.symisc.net/c_api/unqlite_kv_cursor.html
Architecture overview: https://unqlite.symisc.net/arch.html
Jx9 overview: https://unqlite.symisc.net/jx9.html
FAQ: https://unqlite.symisc.net/faq.html

Notes

UnQLite is not a client/server database.
The amalgamation is the easiest way to consume the library.
If you are evaluating the engine for a KV-only use case, start with samples/1.c.
If you need document-oriented scripting, move next to the Jx9 documentation and samples.