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diff --git a/contrib/fmt/README.md b/contrib/fmt/README.md new file mode 100644 index 000000000..592ac2919 --- /dev/null +++ b/contrib/fmt/README.md @@ -0,0 +1,484 @@ +<img src="https://user-images.githubusercontent.com/576385/156254208-f5b743a9-88cf-439d-b0c0-923d53e8d551.png" alt="{fmt}" width="25%"/> + +[](https://github.com/fmtlib/fmt/actions?query=workflow%3Alinux) +[](https://github.com/fmtlib/fmt/actions?query=workflow%3Amacos) +[](https://github.com/fmtlib/fmt/actions?query=workflow%3Awindows) +[](https://bugs.chromium.org/p/oss-fuzz/issues/list?\%0Acolspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20\%0ASummary&q=proj%3Dfmt&can=1) +[](https://stackoverflow.com/questions/tagged/fmt) +[](https://securityscorecards.dev/viewer/?uri=github.com/fmtlib/fmt) + +**{fmt}** is an open-source formatting library providing a fast and safe +alternative to C stdio and C++ iostreams. + +If you like this project, please consider donating to one of the funds +that help victims of the war in Ukraine: <https://www.stopputin.net/>. + +[Documentation](https://fmt.dev) + +[Cheat Sheets](https://hackingcpp.com/cpp/libs/fmt.html) + +Q&A: ask questions on [StackOverflow with the tag +fmt](https://stackoverflow.com/questions/tagged/fmt). + +Try {fmt} in [Compiler Explorer](https://godbolt.org/z/8Mx1EW73v). + +# Features + +- Simple [format API](https://fmt.dev/latest/api.html) with positional + arguments for localization +- Implementation of [C++20 + std::format](https://en.cppreference.com/w/cpp/utility/format) and + [C++23 std::print](https://en.cppreference.com/w/cpp/io/print) +- [Format string syntax](https://fmt.dev/latest/syntax.html) similar + to Python\'s + [format](https://docs.python.org/3/library/stdtypes.html#str.format) +- Fast IEEE 754 floating-point formatter with correct rounding, + shortness and round-trip guarantees using the + [Dragonbox](https://github.com/jk-jeon/dragonbox) algorithm +- Portable Unicode support +- Safe [printf + implementation](https://fmt.dev/latest/api.html#printf-formatting) + including the POSIX extension for positional arguments +- Extensibility: [support for user-defined + types](https://fmt.dev/latest/api.html#formatting-user-defined-types) +- High performance: faster than common standard library + implementations of `(s)printf`, iostreams, `to_string` and + `to_chars`, see [Speed tests](#speed-tests) and [Converting a + hundred million integers to strings per + second](http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html) +- Small code size both in terms of source code with the minimum + configuration consisting of just three files, `core.h`, `format.h` + and `format-inl.h`, and compiled code; see [Compile time and code + bloat](#compile-time-and-code-bloat) +- Reliability: the library has an extensive set of + [tests](https://github.com/fmtlib/fmt/tree/master/test) and is + [continuously fuzzed](https://bugs.chromium.org/p/oss-fuzz/issues/list?colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20Summary&q=proj%3Dfmt&can=1) +- Safety: the library is fully type-safe, errors in format strings can + be reported at compile time, automatic memory management prevents + buffer overflow errors +- Ease of use: small self-contained code base, no external + dependencies, permissive MIT + [license](https://github.com/fmtlib/fmt/blob/master/LICENSE.rst) +- [Portability](https://fmt.dev/latest/index.html#portability) with + consistent output across platforms and support for older compilers +- Clean warning-free codebase even on high warning levels such as + `-Wall -Wextra -pedantic` +- Locale independence by default +- Optional header-only configuration enabled with the + `FMT_HEADER_ONLY` macro + +See the [documentation](https://fmt.dev) for more details. + +# Examples + +**Print to stdout** ([run](https://godbolt.org/z/Tevcjh)) + +``` c++ +#include <fmt/core.h> + +int main() { + fmt::print("Hello, world!\n"); +} +``` + +**Format a string** ([run](https://godbolt.org/z/oK8h33)) + +``` c++ +std::string s = fmt::format("The answer is {}.", 42); +// s == "The answer is 42." +``` + +**Format a string using positional arguments** +([run](https://godbolt.org/z/Yn7Txe)) + +``` c++ +std::string s = fmt::format("I'd rather be {1} than {0}.", "right", "happy"); +// s == "I'd rather be happy than right." +``` + +**Print dates and times** ([run](https://godbolt.org/z/c31ExdY3W)) + +``` c++ +#include <fmt/chrono.h> + +int main() { + auto now = std::chrono::system_clock::now(); + fmt::print("Date and time: {}\n", now); + fmt::print("Time: {:%H:%M}\n", now); +} +``` + +Output: + + Date and time: 2023-12-26 19:10:31.557195597 + Time: 19:10 + +**Print a container** ([run](https://godbolt.org/z/MxM1YqjE7)) + +``` c++ +#include <vector> +#include <fmt/ranges.h> + +int main() { + std::vector<int> v = {1, 2, 3}; + fmt::print("{}\n", v); +} +``` + +Output: + + [1, 2, 3] + +**Check a format string at compile time** + +``` c++ +std::string s = fmt::format("{:d}", "I am not a number"); +``` + +This gives a compile-time error in C++20 because `d` is an invalid +format specifier for a string. + +**Write a file from a single thread** + +``` c++ +#include <fmt/os.h> + +int main() { + auto out = fmt::output_file("guide.txt"); + out.print("Don't {}", "Panic"); +} +``` + +This can be [5 to 9 times faster than +fprintf](http://www.zverovich.net/2020/08/04/optimal-file-buffer-size.html). + +**Print with colors and text styles** + +``` c++ +#include <fmt/color.h> + +int main() { + fmt::print(fg(fmt::color::crimson) | fmt::emphasis::bold, + "Hello, {}!\n", "world"); + fmt::print(fg(fmt::color::floral_white) | bg(fmt::color::slate_gray) | + fmt::emphasis::underline, "Olá, {}!\n", "Mundo"); + fmt::print(fg(fmt::color::steel_blue) | fmt::emphasis::italic, + "你好{}！\n", "世界"); +} +``` + +Output on a modern terminal with Unicode support: + + + +# Benchmarks + +## Speed tests + +| Library | Method | Run Time, s | +|-------------------|---------------|-------------| +| libc | printf | 0.91 | +| libc++ | std::ostream | 2.49 | +| {fmt} 9.1 | fmt::print | 0.74 | +| Boost Format 1.80 | boost::format | 6.26 | +| Folly Format | folly::format | 1.87 | + +{fmt} is the fastest of the benchmarked methods, \~20% faster than +`printf`. + +The above results were generated by building `tinyformat_test.cpp` on +macOS 12.6.1 with `clang++ -O3 -DNDEBUG -DSPEED_TEST -DHAVE_FORMAT`, and +taking the best of three runs. In the test, the format string +`"%0.10f:%04d:%+g:%s:%p:%c:%%\n"` or equivalent is filled 2,000,000 +times with output sent to `/dev/null`; for further details refer to the +[source](https://github.com/fmtlib/format-benchmark/blob/master/src/tinyformat-test.cc). + +{fmt} is up to 20-30x faster than `std::ostringstream` and `sprintf` on +IEEE754 `float` and `double` formatting +([dtoa-benchmark](https://github.com/fmtlib/dtoa-benchmark)) and faster +than [double-conversion](https://github.com/google/double-conversion) +and [ryu](https://github.com/ulfjack/ryu): + +[](https://fmt.dev/unknown_mac64_clang12.0.html) + +## Compile time and code bloat + +The script [bloat-test.py][test] from [format-benchmark][bench] tests compile +time and code bloat for nontrivial projects. It generates 100 translation units +and uses `printf()` or its alternative five times in each to simulate a +medium-sized project. The resulting executable size and compile time (Apple +clang version 15.0.0 (clang-1500.1.0.2.5), macOS Sonoma, best of three) is shown +in the following tables. + +[test]: https://github.com/fmtlib/format-benchmark/blob/master/bloat-test.py +[bench]: https://github.com/fmtlib/format-benchmark + +**Optimized build (-O3)** + +| Method | Compile Time, s | Executable size, KiB | Stripped size, KiB | +|---------------|-----------------|----------------------|--------------------| +| printf | 1.6 | 54 | 50 | +| IOStreams | 25.9 | 98 | 84 | +| fmt 83652df | 4.8 | 54 | 50 | +| tinyformat | 29.1 | 161 | 136 | +| Boost Format | 55.0 | 530 | 317 | + +{fmt} is fast to compile and is comparable to `printf` in terms of per-call +binary size (within a rounding error on this system). + +**Non-optimized build** + +| Method | Compile Time, s | Executable size, KiB | Stripped size, KiB | +|---------------|-----------------|----------------------|--------------------| +| printf | 1.4 | 54 | 50 | +| IOStreams | 23.4 | 92 | 68 | +| {fmt} 83652df | 4.4 | 89 | 85 | +| tinyformat | 24.5 | 204 | 161 | +| Boost Format | 36.4 | 831 | 462 | + +`libc`, `lib(std)c++`, and `libfmt` are all linked as shared libraries +to compare formatting function overhead only. Boost Format is a +header-only library so it doesn\'t provide any linkage options. + +## Running the tests + +Please refer to [Building the +library](https://fmt.dev/latest/usage.html#building-the-library) for +instructions on how to build the library and run the unit tests. + +Benchmarks reside in a separate repository, +[format-benchmarks](https://github.com/fmtlib/format-benchmark), so to +run the benchmarks you first need to clone this repository and generate +Makefiles with CMake: + + $ git clone --recursive https://github.com/fmtlib/format-benchmark.git + $ cd format-benchmark + $ cmake . + +Then you can run the speed test: + + $ make speed-test + +or the bloat test: + + $ make bloat-test + +# Migrating code + +[clang-tidy](https://clang.llvm.org/extra/clang-tidy/) v18 provides the +[modernize-use-std-print](https://clang.llvm.org/extra/clang-tidy/checks/modernize/use-std-print.html) +check that is capable of converting occurrences of `printf` and +`fprintf` to `fmt::print` if configured to do so. (By default it +converts to `std::print`.) + +# Notable projects using this library + +- [0 A.D.](https://play0ad.com/): a free, open-source, cross-platform + real-time strategy game +- [AMPL/MP](https://github.com/ampl/mp): an open-source library for + mathematical programming +- [Apple's FoundationDB](https://github.com/apple/foundationdb): an open-source, + distributed, transactional key-value store +- [Aseprite](https://github.com/aseprite/aseprite): animated sprite + editor & pixel art tool +- [AvioBook](https://www.aviobook.aero/en): a comprehensive aircraft + operations suite +- [Blizzard Battle.net](https://battle.net/): an online gaming + platform +- [Celestia](https://celestia.space/): real-time 3D visualization of + space +- [Ceph](https://ceph.com/): a scalable distributed storage system +- [ccache](https://ccache.dev/): a compiler cache +- [ClickHouse](https://github.com/ClickHouse/ClickHouse): an + analytical database management system +- [Contour](https://github.com/contour-terminal/contour/): a modern + terminal emulator +- [CUAUV](https://cuauv.org/): Cornell University\'s autonomous + underwater vehicle +- [Drake](https://drake.mit.edu/): a planning, control, and analysis + toolbox for nonlinear dynamical systems (MIT) +- [Envoy](https://lyft.github.io/envoy/): C++ L7 proxy and + communication bus (Lyft) +- [FiveM](https://fivem.net/): a modification framework for GTA V +- [fmtlog](https://github.com/MengRao/fmtlog): a performant + fmtlib-style logging library with latency in nanoseconds +- [Folly](https://github.com/facebook/folly): Facebook open-source + library +- [GemRB](https://gemrb.org/): a portable open-source implementation + of Bioware's Infinity Engine +- [Grand Mountain + Adventure](https://store.steampowered.com/app/1247360/Grand_Mountain_Adventure/): + a beautiful open-world ski & snowboarding game +- [HarpyWar/pvpgn](https://github.com/pvpgn/pvpgn-server): Player vs + Player Gaming Network with tweaks +- [KBEngine](https://github.com/kbengine/kbengine): an open-source + MMOG server engine +- [Keypirinha](https://keypirinha.com/): a semantic launcher for + Windows +- [Kodi](https://kodi.tv/) (formerly xbmc): home theater software +- [Knuth](https://kth.cash/): high-performance Bitcoin full-node +- [libunicode](https://github.com/contour-terminal/libunicode/): a + modern C++17 Unicode library +- [MariaDB](https://mariadb.org/): relational database management + system +- [Microsoft Verona](https://github.com/microsoft/verona): research + programming language for concurrent ownership +- [MongoDB](https://mongodb.com/): distributed document database +- [MongoDB Smasher](https://github.com/duckie/mongo_smasher): a small + tool to generate randomized datasets +- [OpenSpace](https://openspaceproject.com/): an open-source + astrovisualization framework +- [PenUltima Online (POL)](https://www.polserver.com/): an MMO server, + compatible with most Ultima Online clients +- [PyTorch](https://github.com/pytorch/pytorch): an open-source + machine learning library +- [quasardb](https://www.quasardb.net/): a distributed, + high-performance, associative database +- [Quill](https://github.com/odygrd/quill): asynchronous low-latency + logging library +- [QKW](https://github.com/ravijanjam/qkw): generalizing aliasing to + simplify navigation, and execute complex multi-line terminal + command sequences +- [redis-cerberus](https://github.com/HunanTV/redis-cerberus): a Redis + cluster proxy +- [redpanda](https://vectorized.io/redpanda): a 10x faster Kafka® + replacement for mission-critical systems written in C++ +- [rpclib](http://rpclib.net/): a modern C++ msgpack-RPC server and + client library +- [Salesforce Analytics + Cloud](https://www.salesforce.com/analytics-cloud/overview/): + business intelligence software +- [Scylla](https://www.scylladb.com/): a Cassandra-compatible NoSQL + data store that can handle 1 million transactions per second on a + single server +- [Seastar](http://www.seastar-project.org/): an advanced, open-source + C++ framework for high-performance server applications on modern + hardware +- [spdlog](https://github.com/gabime/spdlog): super fast C++ logging + library +- [Stellar](https://www.stellar.org/): financial platform +- [Touch Surgery](https://www.touchsurgery.com/): surgery simulator +- [TrinityCore](https://github.com/TrinityCore/TrinityCore): + open-source MMORPG framework +- [🐙 userver framework](https://userver.tech/): open-source + asynchronous framework with a rich set of abstractions and database + drivers +- [Windows Terminal](https://github.com/microsoft/terminal): the new + Windows terminal + +[More\...](https://github.com/search?q=fmtlib&type=Code) + +If you are aware of other projects using this library, please let me +know by [email](mailto:victor.zverovich@gmail.com) or by submitting an +[issue](https://github.com/fmtlib/fmt/issues). + +# Motivation + +So why yet another formatting library? + +There are plenty of methods for doing this task, from standard ones like +the printf family of function and iostreams to Boost Format and +FastFormat libraries. The reason for creating a new library is that +every existing solution that I found either had serious issues or +didn\'t provide all the features I needed. + +## printf + +The good thing about `printf` is that it is pretty fast and readily +available being a part of the C standard library. The main drawback is +that it doesn\'t support user-defined types. `printf` also has safety +issues although they are somewhat mitigated with [\_\_attribute\_\_ +((format (printf, +\...))](https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html) in +GCC. There is a POSIX extension that adds positional arguments required +for +[i18n](https://en.wikipedia.org/wiki/Internationalization_and_localization) +to `printf` but it is not a part of C99 and may not be available on some +platforms. + +## iostreams + +The main issue with iostreams is best illustrated with an example: + +``` c++ +std::cout << std::setprecision(2) << std::fixed << 1.23456 << "\n"; +``` + +which is a lot of typing compared to printf: + +``` c++ +printf("%.2f\n", 1.23456); +``` + +Matthew Wilson, the author of FastFormat, called this \"chevron hell\". +iostreams don\'t support positional arguments by design. + +The good part is that iostreams support user-defined types and are safe +although error handling is awkward. + +## Boost Format + +This is a very powerful library that supports both `printf`-like format +strings and positional arguments. Its main drawback is performance. +According to various benchmarks, it is much slower than other methods +considered here. Boost Format also has excessive build times and severe +code bloat issues (see [Benchmarks](#benchmarks)). + +## FastFormat + +This is an interesting library that is fast, safe and has positional +arguments. However, it has significant limitations, citing its author: + +> Three features that have no hope of being accommodated within the +> current design are: +> +> - Leading zeros (or any other non-space padding) +> - Octal/hexadecimal encoding +> - Runtime width/alignment specification + +It is also quite big and has a heavy dependency, on STLSoft, which might be +too restrictive for use in some projects. + +## Boost Spirit.Karma + +This is not a formatting library but I decided to include it here for +completeness. As iostreams, it suffers from the problem of mixing +verbatim text with arguments. The library is pretty fast, but slower on +integer formatting than `fmt::format_to` with format string compilation +on Karma\'s own benchmark, see [Converting a hundred million integers to +strings per +second](http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html). + +# License + +{fmt} is distributed under the MIT +[license](https://github.com/fmtlib/fmt/blob/master/LICENSE). + +# Documentation License + +The [Format String Syntax](https://fmt.dev/latest/syntax.html) section +in the documentation is based on the one from Python [string module +documentation](https://docs.python.org/3/library/string.html#module-string). +For this reason, the documentation is distributed under the Python +Software Foundation license available in +[doc/python-license.txt](https://raw.github.com/fmtlib/fmt/master/doc/python-license.txt). +It only applies if you distribute the documentation of {fmt}. + +# Maintainers + +The {fmt} library is maintained by Victor Zverovich +([vitaut](https://github.com/vitaut)) with contributions from many other +people. See +[Contributors](https://github.com/fmtlib/fmt/graphs/contributors) and +[Releases](https://github.com/fmtlib/fmt/releases) for some of the +names. Let us know if your contribution is not listed or mentioned +incorrectly and we\'ll make it right. + +# Security Policy + +To report a security issue, please disclose it at [security +advisory](https://github.com/fmtlib/fmt/security/advisories/new). + +This project is maintained by a team of volunteers on a +reasonable-effort basis. As such, please give us at least *90* days to +work on a fix before public exposure. |