Folly: Facebook Open-source Library
Folly (acronymed loosely after Facebook Open Source Library) is a library of C++14 components designed with practicality and efficiency in mind. Folly contains a variety of core library components used extensively at Facebook. In particular, it's often a dependency of Facebook's other open source C++ efforts and place where those projects can share code.
It complements (as opposed to competing against) offerings
such as Boost and of course
std. In fact, we embark on defining our
own component only when something we need is either not available, or
does not meet the needed performance profile. We endeavor to remove
things from folly if or when
std or Boost obsoletes them.
Performance concerns permeate much of Folly, sometimes leading to
designs that are more idiosyncratic than they would otherwise be (see
SmallLocks.h). Good performance at large
scale is a unifying theme in all of Folly.
Folly is a collection of relatively independent components, some as simple as a few symbols. There is no restriction on internal dependencies, meaning that a given folly module may use any other folly components.
All symbols are defined in the top-level namespace
folly, except of
course macros. Macro names are ALL_UPPERCASE and should be prefixed
folly defines other internal namespaces
detail. User code should not depend on symbols
in those namespaces.
Folly has an
experimental directory as well. This designation connotes
primarily that we feel the API may change heavily over time. This code,
typically, is still in heavy use and is well tested.
At the top level Folly uses the classic "stuttering" scheme
folly/folly used by Boost and others. The first directory serves as
an installation root of the library (with possible versioning a la
folly-1.0/), and the second is to distinguish the library when
including files, e.g.
The directory structure is flat (mimicking the namespace structure),
i.e. we don't have an elaborate directory hierarchy (it is possible
this will change in future versions). The subdirectory
contains files that are used inside folly and possibly at Facebook but
not considered stable enough for client use. Your code should not use
folly/experimental lest it may break when you update Folly.
folly/folly/test subdirectory includes the unittests for all
components, usually named
ComponentXyzTest.cpp for each
folly/folly/docs directory contains
What's in it?
Because of folly's fairly flat structure, the best way to see what's in it
is to look at the headers in top level
folly/ directory. You can also
docs folder for documentation, starting with the
Folly is published on Github at https://github.com/facebook/folly
folly requires gcc 5.1+ and a version of boost compiled with C++14 support.
googletest is required to build and run folly's tests. You can download it from https://github.com/google/googletest/archive/release-1.8.0.tar.gz The following commands can be used to download and install it:
wget https://github.com/google/googletest/archive/release-1.8.0.tar.gz && \ tar zxf release-1.8.0.tar.gz && \ rm -f release-1.8.0.tar.gz && \ cd googletest-release-1.8.0 && \ cmake . && \ make && \ make install
Finding dependencies in non-default locations
If you have boost, gtest, or other dependencies installed in a non-default
location, you can use the
variables to make CMAKE look also look for header files and libraries in
non-standard locations. For example, to also search the directories
/alt/include/path2 for header files and the
/alt/lib/path2 for libraries, you can invoke
cmake as follows:
cmake \ -DCMAKE_INCLUDE_PATH=/alt/include/path1:/alt/include/path2 \ -DCMAKE_LIBRARY_PATH=/alt/lib/path1:/alt/lib/path2 ...
Ubuntu 16.04 LTS
The following packages are required (feel free to cut and paste the apt-get command below):
sudo apt-get install \ g++ \ cmake \ libboost-all-dev \ libevent-dev \ libdouble-conversion-dev \ libgoogle-glog-dev \ libgflags-dev \ libiberty-dev \ liblz4-dev \ liblzma-dev \ libsnappy-dev \ make \ zlib1g-dev \ binutils-dev \ libjemalloc-dev \ libssl-dev \ pkg-config
If advanced debugging functionality is required, use:
sudo apt-get install \ libunwind8-dev \ libelf-dev \ libdwarf-dev
In the folly directory (e.g. the checkout root or the archive unpack root), run:
mkdir _build && cd _build cmake .. make -j $(nproc) make install # with either sudo or DESTDIR as necessary
OS X (Homebrew)
folly is available as a Formula and releases may be built via
brew install folly.
You may also use
folly/build/bootstrap-osx-homebrew.sh to build against
This will create a build directory
_build in the top-level.
OS X (MacPorts)
Install the required packages from MacPorts:
sudo port install \ boost \ cmake \ gflags \ git \ google-glog \ libevent \ libtool \ lz4 \ lzma \ openssl \ snappy \ xz \ zlib
Download and install double-conversion:
git clone https://github.com/google/double-conversion.git cd double-conversion cmake -DBUILD_SHARED_LIBS=ON . make sudo make install
Download and install folly with the parameters listed below:
git clone https://github.com/facebook/folly.git cd folly mkdir _build cd _build cmake .. make sudo make install
folly is available in Vcpkg and releases may be built via
vcpkg install folly:x64-windows.
You may also use
vcpkg install folly:x64-windows --head to build against
Other Linux distributions
Download and build double-conversion. You may need to tell cmake where to find it.
ln -s src double-conversion
mkdir build && cd build[folly/build/]
cmake "-DCMAKE_INCLUDE_PATH=$DOUBLE_CONVERSION_HOME/include" "-DCMAKE_LIBRARY_PATH=$DOUBLE_CONVERSION_HOME/lib" ..
additional platform specific dependencies:
Fedora >= 21 64-bit (last tested on Fedora 28 64-bit)