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

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

Compile the bundled key/value intro sample:

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

MSVC

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

Compile the bundled key/value intro sample:

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:

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

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

Minimal Example

#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.

License

UnQLite is distributed under the 2-Clause BSD license.

• License text in this repository: LICENSE
• Official licensing page: https://unqlite.symisc.net/licensing.html