stephenboyd / couchbase-lite-core

Couchbase Lite Core (aka LiteCore) is the next-generation core storage and query engine for Couchbase Lite. It provides a cross-platform implementation of the database CRUD and query features, document versioning, and replication/sync.

All platform implementations of Couchbase Lite 2.0 are built atop this core, adding higher-level language & platform bindings. But LiteCore may find other uses too, perhaps for applications that want a fast minimalist data store with map/reduce indexing and queries, but don't need the higher-level features of Couchbase Lite.

THIS IS STILL PRE-1.0. As of August 2017, the status is roughly "beta". We expect a stable 1.0 release by the end of 2017. See "Status" section below.

Features

• Database CRUD (Create, Read, Update, Delete) operations:
  • Fast key-value storage, where keys and values are both opaque blobs
  • Iteration by key order
  • Iteration by sequence, reflecting the order in which changes were made to the database. (This is useful for tasks like updating indexes and replication.)
  • Optional multi-version document format that tracks history using a revision tree (as in CouchDB) or version vectors
  • Timed document expiration (as in Couchbase Server)
  • API support for database encryption (as provided by SQLCipher or SQLite's Encryption Extension)
  • Highly efficient Fleece binary data encoding: supports JSON data types but requires no parsing, making it extremely efficient to read.
• Direct database querying based on N1QL:
  • Supports most N1QL functionality
  • JSON-based query syntax, similar to a parse tree; easy to generate from platform APIs like NSPredicate
  • Can search and index arbitrary document properties without requiring any schema
  • Queries compile into SQL and from there into SQLite compiled bytecode
  • Parameters can be substituted without having to recompile the query
  • Queries don't require indexes, but will run faster if indexes are created on the document properties being searched for.
  • Supports full-text search, using SQLite's FTS4 module.
  • (Map-reduce is still in the source tree but hasn't been built in a while so it's unlikely to work without fixes.)
• Replicator:
  • Multi-master bidirectional document sync
  • Uses BLIP multiplexing protocol over WebSockets
  • Pluggable transports mean it could run over Bluetooth or other protocols
• REST API:
  • Implements a subset of the CouchDB / Sync Gateway / Couchbase Lite REST API
  • Currently incomplete; not ready for prime time
• Pluggable storage engines:
  • SQLite is available by default
  • Others can be added by implementing C++ DataFile and KeyStore interfaces
• C and C++ APIs
• Bindings to C# and Java

Platform Support

LiteCore runs on Mac OS, iOS, tvOS, Android, various other flavors of Unix, and Windows.

It is written in C++ (using C++11 features) and compiles with Clang and MSVC.

Status

As of August 2017: Under heavy development, approaching beta. Almost all features are implemented, and seem pretty solid, but APIs may still change and there may be short-term build problems if one compiler or another dislikes a recent commit.

• The primary development platform is macOS, so the Xcode project should always build, and the code should pass its unit tests on Mac. iOS is pretty likely to work too ,since it's so similar to Mac at this level.
• The CMake build is generally up to date but may fall behind.
• The C# and Java bindings are updated within a few days of C API changes.

Building It

Very Important:

• This repo has submodules. Make sure they're checked out. Either use git clone --recursive to download LiteCore, or else after the clone run git submodule update --init --recursive.

Once you've cloned or downloaded the source tree...

macOS, iOS

If you want to use Objective-C or Swift APIs, you should use Couchbase Lite instead — check out and build the feature/2.0 branch of the couchbase-lite-ios repo, which itself includes LiteCore as a submodule. The following instructions are to build just LiteCore on its own:

• Make sure you have Xcode 8.3 or later.
• Open Xcode/LiteCore.xcodeproj.
• Select the scheme LiteCore dylib.
• Build.

Linux, Android

Note Android requires CMake 3.7 or higher!

Important! LiteCore uses a couple of external libraries, which may or may not be installed in your system already. If not, please install the appropriate development packages via your package manager. You must have the following libraries present:

• libz
• libatomic (usually comes with libgcc)

You'll need Clang 3.8 or higher. Unfortunately a lot of distros only have 3.5; run clang --version to check, and upgrade manually if necessary. You also need a corresponding version of libc++. On Debian-like systems, the apt-get packages you need are clang, libc++1, libc++-dev, libc++abi-dev.

Actually Building

Once you've got the dependencies and compiler installed, do this from the root directory of the source tree:

cd build_cmake/scripts
./build_unix.sh

If CMake's initial configuration checks fail, the setup may be left in a broken state and will then fail immediately. To remedy this:

rm -r ../unix
./build_unix.sh

Windows Desktop

Open the Visual Studio 2015 Developer Command Prompt and navigate to the repo root. Then execute:

* 64-bit build *
cd build_make
"C:\Program Files (x86)\CMake\bin\cmake.exe" -G "Visual Studio 14 2015 Win64" ..

* 32-bit build *
cd build_make
"C:\Program Files (x86)\CMake\bin\cmake.exe" -G "Visual Studio 14 2015" ..

This will create LiteCore.sln in the directory that you can open with Visual Studio.

Windows Store

Open the Visual Studio 2015 Developer Command Prompt and navigate to the repo root. Then execute:

* x64 build *
cd build_make
"C:\Program Files (x86)\CMake\bin\cmake.exe" -G "Visual Studio 14 2015 Win64" -DCMAKE_SYSTEM_NAME=WindowsStore
-D CMAKE_SYSTEM_VERSION="10.0.14393.0" ..

* x86 build *
cd build_make
"C:\Program Files (x86)\CMake\bin\cmake.exe" -G "Visual Studio 14 2015" -DCMAKE_SYSTEM_NAME=WindowsStore
-D CMAKE_SYSTEM_VERSION="10.0.14393.0" ..

* ARM build *
cd build_make
"C:\Program Files (x86)\CMake\bin\cmake.exe" -G "Visual Studio 14 2015 ARM" -DCMAKE_SYSTEM_NAME=WindowsStore
-D CMAKE_SYSTEM_VERSION="10.0.14393.0" ..

This will create LiteCore.sln in the directory that you can open with Visual Studio.

Documentation

API

We have online C API documentation, generated by Doxygen from the headers.

If this is out of date, or you want a local copy, you can generate your own by running the following commands from a shell at the root directory of the repo:

cd C
doxygen

The main page is then located at ../docs/C/html/modules.html.

Internal Implementation

For those interested in diving into the implementation, there is an overview of the major classes.

Authors

Jens Alfke (@snej), Jim Borden (@borrrden), Hideki Itakura (@hideki)

License

Like all Couchbase open source code, this is released under the Apache 2 license.