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+{fmt}
+=====
+
+.. image:: https://travis-ci.org/fmtlib/fmt.png?branch=master
+ :target: https://travis-ci.org/fmtlib/fmt
+
+.. image:: https://ci.appveyor.com/api/projects/status/ehjkiefde6gucy1v
+ :target: https://ci.appveyor.com/project/vitaut/fmt
+
+.. image:: https://oss-fuzz-build-logs.storage.googleapis.com/badges/fmt.svg
+ :alt: fmt is continuously fuzzed at oss-fuzz
+ :target: https://bugs.chromium.org/p/oss-fuzz/issues/list?\
+ colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20\
+ Summary&q=proj%3Dfmt&can=1
+
+.. image:: https://img.shields.io/badge/stackoverflow-fmt-blue.svg
+ :alt: Ask questions at StackOverflow with the tag fmt
+ :target: https://stackoverflow.com/questions/tagged/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 BYSOL,
+an initiative to help victims of political repressions in Belarus:
+https://www.facebook.com/donate/759400044849707/108388587646909/.
+
+`Documentation <https://fmt.dev>`__
+
+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/Eq5763>`_.
+
+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>`__
+* `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
+* 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`_
+ 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`_
+* 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%20
+ Component%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>`_)
+
+.. code:: c++
+
+ #include <fmt/core.h>
+
+ int main() {
+ fmt::print("Hello, world!\n");
+ }
+
+**Format a string** (`run <https://godbolt.org/z/oK8h33>`_)
+
+.. code:: 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>`_)
+
+.. code:: c++
+
+ std::string s = fmt::format("I'd rather be {1} than {0}.", "right", "happy");
+ // s == "I'd rather be happy than right."
+
+**Print chrono durations** (`run <https://godbolt.org/z/K8s4Mc>`_)
+
+.. code:: c++
+
+ #include <fmt/chrono.h>
+
+ int main() {
+ using namespace std::literals::chrono_literals;
+ fmt::print("Default format: {} {}\n", 42s, 100ms);
+ fmt::print("strftime-like format: {:%H:%M:%S}\n", 3h + 15min + 30s);
+ }
+
+Output::
+
+ Default format: 42s 100ms
+ strftime-like format: 03:15:30
+
+**Print a container** (`run <https://godbolt.org/z/MjsY7c>`_)
+
+.. code:: 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**
+
+.. code:: c++
+
+ std::string s = fmt::format(FMT_STRING("{:d}"), "don't panic");
+
+This gives a compile-time error because ``d`` is an invalid format specifier for
+a string.
+
+**Write a file from a single thread**
+
+.. code:: 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**
+
+.. code:: 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, "Hello, {}!\n", "мир");
+ fmt::print(fg(fmt::color::steel_blue) | fmt::emphasis::italic,
+ "Hello, {}!\n", "世界");
+ }
+
+Output on a modern terminal:
+
+.. image:: https://user-images.githubusercontent.com/
+ 576385/88485597-d312f600-cf2b-11ea-9cbe-61f535a86e28.png
+
+Benchmarks
+----------
+
+Speed tests
+~~~~~~~~~~~
+
+================= ============= ===========
+Library Method Run Time, s
+================= ============= ===========
+libc printf 1.04
+libc++ std::ostream 3.05
+{fmt} 6.1.1 fmt::print 0.75
+Boost Format 1.67 boost::format 7.24
+Folly Format folly::format 2.23
+================= ============= ===========
+
+{fmt} is the fastest of the benchmarked methods, ~35% faster than ``printf``.
+
+The above results were generated by building ``tinyformat_test.cpp`` on macOS
+10.14.6 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/tinyformat_test.cpp>`_.
+
+{fmt} is up to 20-30x faster than ``std::ostringstream`` and ``sprintf`` on
+floating-point 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>`_:
+
+.. image:: https://user-images.githubusercontent.com/576385/
+ 95684665-11719600-0ba8-11eb-8e5b-972ff4e49428.png
+ :target: https://fmt.dev/unknown_mac64_clang12.0.html
+
+Compile time and code bloat
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The script `bloat-test.py
+<https://github.com/fmtlib/format-benchmark/blob/master/bloat-test.py>`_
+from `format-benchmark <https://github.com/fmtlib/format-benchmark>`_
+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 LLVM version 8.1.0 (clang-802.0.42),
+macOS Sierra, best of three) is shown in the following tables.
+
+**Optimized build (-O3)**
+
+============= =============== ==================== ==================
+Method Compile Time, s Executable size, KiB Stripped size, KiB
+============= =============== ==================== ==================
+printf 2.6 29 26
+printf+string 16.4 29 26
+iostreams 31.1 59 55
+{fmt} 19.0 37 34
+Boost Format 91.9 226 203
+Folly Format 115.7 101 88
+============= =============== ==================== ==================
+
+As you can see, {fmt} has 60% less overhead in terms of resulting binary code
+size compared to iostreams and comes pretty close to ``printf``. Boost Format
+and Folly Format have the largest overheads.
+
+``printf+string`` is the same as ``printf`` but with extra ``<string>``
+include to measure the overhead of the latter.
+
+**Non-optimized build**
+
+============= =============== ==================== ==================
+Method Compile Time, s Executable size, KiB Stripped size, KiB
+============= =============== ==================== ==================
+printf 2.2 33 30
+printf+string 16.0 33 30
+iostreams 28.3 56 52
+{fmt} 18.2 59 50
+Boost Format 54.1 365 303
+Folly Format 79.9 445 430
+============= =============== ==================== ==================
+
+``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`__ for the instructions on how to build
+the library and run the unit tests.
+
+__ https://fmt.dev/latest/usage.html#building-the-library
+
+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
+
+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
+
+* `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>`_: analytical database
+ management system
+
+* `CUAUV <http://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
+
+* `Folly <https://github.com/facebook/folly>`_: Facebook open-source library
+
+* `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
+
+* `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 executing 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
+
+* `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:
+
+.. code:: c++
+
+ std::cout << std::setprecision(2) << std::fixed << 1.23456 << "\n";
+
+which is a lot of typing compared to printf:
+
+.. code:: 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 which 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`_).
+
+FastFormat
+~~~~~~~~~~
+
+This is an interesting library which 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, STLSoft, which might be too
+restrictive for using it in some projects.
+
+Boost Spirit.Karma
+~~~~~~~~~~~~~~~~~~
+
+This is not really 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.rst>`_.
+
+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>`_) and Jonathan Müller (`foonathan
+<https://github.com/foonathan>`_) 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.
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 23:11:26 +0000