folly/
For a high level overview see the README
Components
Below is a list of (some) Folly components in alphabetical order, along with a brief description of each.
Arena.h, ThreadCachedArena.h
Simple arena for memory allocation: multiple allocations get freed all at once. With threaded version.
AtomicHashMap.h, AtomicHashArray.h, AtomicHashArray.h, AtomicLinkedList.h, ...
High-performance atomic data-structures. Many of these are built with very specific tradeoffs and constraints in mind that make them faster than their more general counterparts. Each header should contain information about what these tradeoffs are.
Baton.h
A Baton allows a thread to block once and be awoken: it captures a single handoff. It is essentially a (very small, very fast) semaphore that supports only a single call to sem_call and sem_wait.
Benchmark.h
A small framework for benchmarking code. Client code registers benchmarks, optionally with an argument that dictates the scale of the benchmark (iterations, working set size etc). The framework runs benchmarks (subject to a command-line flag) and produces formatted output with timing information.
Bits.h
Various bit manipulation utilities optimized for speed; includes functions that wrap the ffsl(l) primitives in a uniform interface.
ConcurrentSkipList.h
An implementation of the structure described in A Provably Correct Scalable Concurrent Skip List by Herlihy et al.
Conv.h
A variety of data conversion routines (notably to and from string), optimized for speed and safety.
Demangle.h
Pretty-printing C++ types.
DiscriminatedPtr.h
Similar to boost::variant, but restricted to pointers only. Uses the highest-order unused 16 bits in a pointer as discriminator. So sizeof(DiscriminatedPtr<int, string, Widget>) == sizeof(void*).
dynamic.h
Dynamically-typed object, created with JSON objects in mind. DynamicConverter.h is a utility for effeciently converting from a dynamic to a more concrete structure when the scheme is known (e.g. json -> map<int,int>).
EvictingCacheMap.h
A simple LRU hash map.
FBString.h
A drop-in implementation of std::string with a variety of optimizations.
FBVector.h
A mostly drop-in implementation of std::vector with a variety of optimizations.
File.h
A C++ abstraction around files.
Fingerprint.h
Rabin fingerprinting.
Function.h
A polymorphic wrapper for callables similar to std::function but not copyable and therefore able to wrap non-copyable callables, such as lambdas that capture move-only types like std::unique_ptr or folly::Promise.
futures/
Futures is a framework for expressing asynchronous code in C++ using the Promise/Future pattern.
Format.h
Python-style formatting utilities.
gen/
This library makes it possible to write declarative comprehensions for processing sequences of values efficiently in C++ akin to C#'s LINQ.
GroupVarint.h
Group Varint encoding for 32-bit values.
####IpAddress.h
A collection of utilities to deal with IPAddresses, including ipv4 and ipv6.
io/
A collection of useful of abstractions for high-performance io. This is heavily relied upon in Facebook's internally networking code.
Hash.h
Various popular hash function implementations.
Histogram.h
A simple class for collecting histogram data.
IntrusiveList.h
Convenience type definitions for using boost::intrusive_list.
json.h
JSON serializer and deserializer. Uses dynamic.h.
Likely.h
Wrappers around __builtin_expect.
Malloc.h, Memory.h
Memory allocation helpers, particularly when using jemalloc.
MicroSpinLock.h
A really, really small spinlock for fine-grained locking of lots of teeny-tiny data.
MPMCQueue.h
MPMCQueue is a high-performance bounded concurrent queue that supports multiple producers, multiple consumers, and optional blocking. The queue has a fixed capacity, for which all memory will be allocated up front.
The additional utility MPMCPipeline.h is an extension that lets you chain several queues together with processing steps in between.
PackedSyncPtr.h
A highly specialized data structure consisting of a pointer, a 1-bit spin lock, and a 15-bit integral, all inside one 64-bit word.
Preprocessor.h
Necessarily evil stuff.
ProducerConsumerQueue.h
Lock free single-reader, single-writer queue.
Random.h
Defines only one function---randomNumberSeed().
Range.h
Boost-style range facility and the StringPiece specialization.
RWSpinLock.h
Fast and compact reader-writer spin lock.
ScopeGuard.h
C++11 incarnation of the old ScopeGuard idiom.
Singleton.h
A singleton to rule the singletons. This is an attempt to insert a layer between C++ statics and the fiasco that ensues, so that things can be created, and destroyed, correctly upon program creation, program end and sometimes dlopen and fork.
Singletons are bad for you, but this may help.
SmallLocks.h
Very small spin locks (1 byte and 1 bit).
small_vector.h
Vector with the small buffer optimization and an optional embedded PicoSpinLock.
sorted_vector_types.h
Collections similar to std::map but implemented as sorted vectors.
stats/
A collection of efficient utilities for collecting statistics (often of time series data).
StlAllocator.h
STL allocator wrapping a simple allocate/deallocate interface.
String.h
String utilities that connect folly::fbstring with std::string.
Subprocess.h
Subprocess library, modeled after Python's subprocess module.
Synchronized.h
High-level synchronization library.
System.h
Demangling and errno utilities.
ThreadCachedInt.h
High-performance atomic increment using thread caching.
ThreadLocal.h
Improved thread local storage for non-trivial types.
TimeoutQueue.h
Queue with per-item timeout.
Traits.h
Type traits that complement those defined in the standard C++11 header <traits>.
Unicode.h
Defines the codePointToUtf8 function.
Uri.h
A collection of utilities to deal with URIs.
https://github.com/facebook/folly/blob/master/folly/docs/Overview.md
What is folly?
Folly (acronymed loosely after Facebook Open Source Library) is a library of C++11 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 e.g. PackedSyncPtr.h, SmallLocks.h). Good performance at large scale is a unifying theme in all of Folly.
Logical Design
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 with FOLLY_. Namespace folly defines other internal namespaces such as internal or 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.
Physical Design
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. #include <folly/FBString.h>.
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 experimental contains files that are used inside folly and possibly at Facebook but not considered stable enough for client use. Your code should not use files in folly/experimentallest it may break when you update Folly.
The folly/folly/test subdirectory includes the unittests for all components, usually named ComponentXyzTest.cpp for eachComponentXyz.*. The folly/folly/docs directory contains documentation.
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 check the docs folder for documentation, starting with the overview.
Folly is published on Github at https://github.com/facebook/folly
Build Notes
Dependencies
folly requires gcc 4.9+ and a version of boost compiled with C++14 support.
Please download googletest from https://github.com/google/googletest/archive/release-1.8.0.tar.gz and unpack it into the folly/test subdirectory as gtest:
(cd folly/test &&
rm -rf gtest &&
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 &&
mv googletest-release-1.8.0 gtest)
Linking non-default boost libraries
If you have boost installed in a non-default location, you need to be sure that the linker and configure scripts know where to find boost. This means making sure that the LIBRARY_PATH environment variable contains <BOOST_ROOT>/lib, as well as including the path explicitly when running ./configure:
export LIBRARY_PATH=$BOOST_ROOT/lib:$LIBRARY_PATH
./configure --with-boost=$BOOST_ROOT/lib
Ubuntu 12.04
This release is old, requiring many upgrades. However, since Travis CI runs on 12.04, folly/build/deps_ubuntu_12.04.sh is provided, and upgrades all the required packages.
Ubuntu 13.10
The following packages are required (feel free to cut and paste the apt-get command below):
sudo apt-get install
g++
automake
autoconf
autoconf-archive
libtool
libboost-all-dev
libevent-dev
libdouble-conversion-dev
libgoogle-glog-dev
libgflags-dev
liblz4-dev
liblzma-dev
libsnappy-dev
make
zlib1g-dev
binutils-dev
libjemalloc-dev
libssl-dev
pkg-config
If advanced debugging functionality is required
sudo apt-get install
libunwind8-dev
libelf-dev
libdwarf-dev
Ubuntu 14.04 LTS
The packages listed above for Ubuntu 13.10 are required, as well as:
sudo apt-get install
libiberty-dev
The above packages are sufficient for Ubuntu 13.10 and Ubuntu 14.04.
In the folly directory, run:
autoreconf -ivf
./configure
make
make check
sudo make install
Ubuntu 16.04 LTS
The packages listed above for 13.10 and 14.04 are sufficient for installation, and the build commands remain the same.
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 master:
cd folly
./build/bootstrap-osx-homebrew.sh
OS X (MacPorts)
Install the required packages from MacPorts:
sudo port install
autoconf
automake
boost
gflags
git
google-glog
libevent
libtool
lz4
lzma
scons
snappy
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/folly
autoreconf -ivf
./configure CPPFLAGS="-I/opt/local/include" LDFLAGS="-L/opt/local/lib"
make
sudo make install
Other Linux distributions
-
double-conversion (https://github.com/google/double-conversion)
Download and build double-conversion. You may need to tell configure where to find it.
[double-conversion/]
ln -s src double-conversion[folly/]
./configure LDFLAGS=-L$DOUBLE_CONVERSION_HOME/ CPPFLAGS=-I$DOUBLE_CONVERSION_HOME/[folly/]
LD_LIBRARY_PATH=$DOUBLE_CONVERSION_HOME/ make -
additional platform specific dependencies:
Fedora 21 64-bit
- gcc
- gcc-c++
- autoconf
- autoconf-archive
- automake
- boost-devel
- libtool
- lz4-devel
- lzma-devel
- snappy-devel
- zlib-devel
- glog-devel
- gflags-devel
- scons
- double-conversion-devel
- openssl-devel
- libevent-devel
Optional
- libdwarf-dev
- libelf-dev
- libunwind8-dev
https://github.com/facebook/folly/blob/master/README.md