faux-folly/folly/docs/Overview.md

`folly/`

Introduction

Folly (acronymed loosely after Facebook Open Source Library) is a library of C++11 components designed with practicality and efficiency in mind. 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.

Performance concerns permeate much of Folly, sometimes leading to designs that are more idiosyncratic than they would otherwise be. 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. Namespace folly defines other internal namespaces such as internal or detail. User code should not depend on symbols in those namespaces.

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 folly/folly/test subdirectory includes the unittests for all components, usually named ComponentXyzTest.cpp for each ComponentXyz.*. The folly/folly/docs directory contains documentation.

Compatibility

Currently, folly has been tested on gcc 4.6 on 64-bit installations of Fedora 17, Ubuntu 12.04, and Debian wheezy. It might work unmodified on other 64-bit Linux platforms.

Components

Below is a list of Folly components in alphabetical order, along with a brief description of each.

`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.