fast_io is a C++20 input/output library that provides exceptional speed and is designed to replace the commonly used <iostream>
and <cstdio>
libraries. It is a header-only library and is licensed under the MIT license, making it easy to include in any project. However, it requires a C++20 compiler that supports concepts.
The original repository for fast_io has been archived due to git bloat over time, but older commits can still be found there. old commits were here.
stdout
#include <fast_io.h>
int main() {
print("Hello, fast_io world!\n");
}
#include <fast_io.h>
int main() {
fast_io::native_file_loader file_data("text.txt");
// file_data satisfies std::ranges::contiguous_range
}
For other up-to-date examples, please look in the examples/
folder.
Deprecated examples are here but they might not work anymore.
This i18n repo stores the i18n source files.
https://bitbucket.org/ejsvifq_mabmip/fast_io_i18n
The term fast
in fast_io
does not necessarily imply that it is the fastest input/output library available (as it would have been named as fastest_io
instead). Instead, the term refers to the fact that fast_io
is notably faster than <iostream>
and <cstdio>
libraries in all cases.
See support.md for a list of supported things and platform specific usage notes.
You can ask questions on the fast_io discord server
or QQ group: 801441303
.
See either https://ewindy.gitee.io/fast_io_rst/index.html or https://gitee.com/qabeowjbtkwb/fast_io/wikis.
As close to system call as possible.
Unicode support (UTF-8, UTF-16, UTF-32) + codecvt for GB18030 and UTF-EBCDIC (no libc correctly deals with it)
RAII for C FILE*
, POSIX fd
and win32/NT HANDLE
Interop with <cstdio>
and <iostream>
No easily misused stuff like std::endl
Static I/O manipulators instead of format strings.
Optional locale.
Stateless I/O manipulation.
Consistent error handling; when available, exceptions as the only error reporting mechanism (no std::error_code
, std::system_error
or useless bounds checking)
Freestanding mode.
Address Sanitizer special code for protecting memory safety issues.
Dynamic Instrumentation Support
Supports POSIX iconv. You can use fast_io for your coding conversion.
Binary serialization for trivially copyable types and standard containers
Plays well with C++ containers (e.g. std::vector<fast_io::obuf_file>
is valid)
Basic/Lua/Python/etc format (print, scan). No support for C and C++ since they are security hazards.
Provide APIs to expose the internal implementation of FILE*
and C++ streams.
Native Handle Interface
Extremely easy to support custom devices
C and C++ style compile time open mode parsing.
No traits_type
and EOF
Dynamic Type Support
Multi Process
Memory mapping
debugging IO (optionally with GUI)
Round-trip floating point algorithm
Hash algorithms support: intrinsic SHA-1, intrinsic HMAC-SHA1, intrinsic SHA-256, intrinsic HMAC-SHA256, SHA-512, HMAC-SHA512 as well as non crypto hash algorithms, such as Jenkins Hash.
zlib compression/decompression
Filesystem
OpenSSL BIO, Qt QFile, MFC CFile support
Goal: Print out ten million integers from 0 to 10M to file. Then reopen that file to scan back.
All benchmarks are in benchmarks/0000.10m_size_t/unit.
Notice: I modified libstdc++'s BUFSIZ 1048576 due to BUFSIZ is too small (512 bytes) for MinGW-W64, or it performs horribly.
Platform | Windows | MinGW-W64 GCC 11.0.0 | MSVCRT + libstdc++ |
---|---|---|---|
Method | Output time | Input time | Comment |
---|---|---|---|
stdio.h(fprintf/fscanf) | 2.412987s | 5.607791s | |
fstream | 0.462012s | 1.192s | |
fstream with rdbuf.sputc trick | 0.33895s | 1.170173s | |
fast_io::i/obuf_file | 0.04903s | 0.080996s | |
fast_io::i/obuf_file_mutex | 0.146064s | 0.113155s | thread safe |
c_locale_i/obuf_file ("C") | 0.065988s | 0.086012s | imbued with locale, locale "C" |
c_locale_i/obuf_file local | 0.153995s | :x: | imbued with locale, locale "" |
fmt::format_int+obuf_file | 0.122999s | :x: | |
fmt::format_int+ofstream | 0.209055s | :x: | |
fmt::format+ofstream | 0.548s | :x: | fmt makes things slower |
fmt::print | 0.663996s | :x: | fmt makes things slower |
std::to_chars+obuf_file | 0.12s | :x: | |
std::to_chars+ofstream | 0.192s | :x: | |
fast_io::c_file_unlocked | 0.098999s | 0.126003s | I hacked MSVCRT's FILE* implementation |
fast_io::c_file | 0.298988s | 0.318001s | Thread Safe. I hacked MSVCRT's FILE* implementation |
fast_io::filebuf_file | 0.048999s | 0.081s | I hacked libstdc++'s streambuf/filebuf implementation |
fast_io::iobuf_utf8_file_char16 | 0.124s | 0.112001s | UTF-16=>UTF-8 with SSE |
fast_io::iobuf_utf8_file_char32 | 0.110999s | 0.111011s | UTF-32=>UTF-8 with SSE |
std::wofstream | 2.64s | 3.843735s | wofstream with std::locale codecvt. Extremely slow tbh. |
fast_io::wfilebuf_io_observer | 2.415692s | 2.497704s | wofstream with std::locale codecvt. This proves fstream can never get fixed. |
Rust language | 0.483s | :x: | RUST IS SLOW. Also Rust does not deal with locale. Think how bad it is. |
Rust itoa library 0.4.6 | > 0.165s | :x: | I ignored the \n part for it to ensure no bias. |
Rust language is 10x slower than fast_io. + binary bloat and itoa library is still extremely slow and usable for me. It is at least 3x slower than fast_io.
Run the same test on MSVC 19.26.28805.
Platform | Windows | MSVC 19.26.28805 | Install fmtlib wastes time of my life |
---|---|---|---|
Method | Output time | Input time | Comment |
---|---|---|---|
stdio.h(fprintf/fscanf) | 1.5353597s | 1.4157233s | |
fstream | 3.6350262s | 3.8420339s | |
fstream with rdbuf.sputc trick | 3.3735902s | 3.8145566s | |
fast_io::i/obuf_file | 0.0631433s | 0.1030554s | |
fast_io::i/obuf_file_mutex | 0.2190659s | 0.2485886s | thread safe |
std::to_chars+obuf_file | 0.1641641s | :x: | |
std::to_chars+ofstream | 0.5461922s | :x: | |
fast_io::c_file_unlocked | 0.1102575s | 0.2399757s | I hacked Universal CRT's FILE* implementation |
fast_io::c_file | 0.2034755s | 0.2621148s | Thread Safe. I hacked UCRT's FILE* implementation |
fast_io::filebuf_file | 0.126661s | 0.2378803s | I hacked MSVC STL's streambuf/filebuf implementation |
Run the same test on GCC 11. glibc + libstdc++
Platform | Linux | GCC 11.0.0 | glibc + libstdc++ |
---|---|---|---|
Method | Output time | Input time | Comment |
---|---|---|---|
stdio.h(fprintf/fscanf) | 0.532792935s | 0.591907111s | |
fstream with rdbuf.sputc trick | 0.318896068s | 0.429406415s | |
fast_io::i/obuf_file | 0.050300857s | 0.065372395s | |
fast_io::i/obuf_file_mutex | 0.05290654s | 0.083040518s | thread safe |
c_locale_i/obuf_file ("C") | 0.051939052s | 0.065820056s | imbued with locale, locale "C" |
c_locale_i/obuf_file local | 0.162406082s | :x: | imbued with locale, locale "" |
std::to_chars+obuf_file | 0.115453587s | :x: | |
fmt::format_int+obuf_file | 0.1183587s | :x: | |
fmt::format_int+ofstream | 0.195914384s | :x: | |
fmt::format+ofstream | 0.633590975s | :x: | fmt makes things slower |
fmt::print | 0.495270371s | :x: | fmt makes things slower |
boost::iostreams | 0.400906063s | 0.444717051s | Using boost iostreams does not make your code faster |
fast_io::c_file_unlocked | 0.060076723s | 0.073299716s | I hacked glibc's FILE* implementation |
fast_io::c_file | 0.092490191s | 0.104545535s | Thread Safe. I hacked glibc's FILE* implementation |
fast_io::filebuf_file | 0.052251608s | 0.06655806s | I hacked libstdc++'s streambuf/filebuf implementation |
You can see fast_io can also boost the performance of existing facilities for 10x! Yes, it can even improve FILE* and fstream's performance for 10x depending on platforms since I use concepts to abstract them all. fmtlib actually slows down I/O performance.
We only perform this test for MSVC since only msvc's charconv implements it. Yes. fast_io defeats msvc's charconv for over 20% for running the same algorithm.
All benchmarks are in benchmarks/0001.10m_double/charconv.
Run the same test on MSVC 19.26.28805.
Platform | Windows | MSVC 19.26.28805 | |
---|---|---|---|
Method | Output time | Comment |
---|---|---|
i/obuf_file | 0.4653818s | |
charconv + obuf_file | 0.6011s |
All benchmarks are in benchmarks/0014.file_io/file_io.
Output 100000000x "Hello World\n"
Notice: I modified libstdc++'s std::filebuf's BUFSIZ to 1048576 due to BUFSIZ is too small (512 bytes) for MinGW-W64 or it performs horribly.
Platform | Windows | MinGW-W64 GCC 11.0.0 | MSVCRT + libstdc++ |
---|---|---|---|
Method | Output time | Comment |
---|---|---|
fwrite | 2.524001s | |
fstream | 1.013001s | |
fast_io::obuf_file | 0.437998s | |
fast_io::obuf_file_mutex | 1.371s | Thread safe |
fast_io::c_file_unlocked | 1.164997s | I hacked MSVCRT's FILE* implementation |
fast_io::c_file | 3.337945s | Thread Safe. I hacked MSVCRT's FILE* implementation. Need further optimization |
fast_io::filebuf_file | 0.467001s | I hacked libstdc++'s std::filebuf implementation |
Platform | Linux | GCC 11.0.0 | glibc + libstdc++ |
---|---|---|---|
Method | Output time | Comment |
---|---|---|
fwrite | 1.457288317s | |
fstream | 1.249783346s | |
fast_io::obuf_file | 0.494827134s | |
fast_io::obuf_file_mutex | 0.497138826s | Thread safe |
fast_io::c_file_unlocked | 0.687976666s | I hacked glibc's FILE* implementation |
fast_io::c_file | 0.910792697s | Thread Safe. I hacked glibc's FILE* implementation |
fast_io::filebuf_file | 0.526955039s | I hacked libstdc++'s std::filebuf implementation |
Platform | Windows | MSVC 19.26.28805 | UCRT + MSVC STL |
---|---|---|---|
Method | Output time | Comment |
---|---|---|
fwrite | 3.3139122s | |
fstream | 1.7184119s | |
fast_io::obuf_file | 0.7996034s | |
fast_io::obuf_file_mutex | 2.2949221s | Thread safe. It looks like std::mutex is horribly slow for MSVC STL. |
fast_io::c_file_unlocked | 1.2103924s | I hacked UCRT's FILE* implementation |
fast_io::c_file | 2.3604295s | Thread Safe. I hacked UCRT's FILE* implementation |
fast_io::filebuf_file | 1.2805368s | I hacked MSVC STL's std::filebuf implementation |
Platform | Windows | MinGW-W64 GCC 11.0.0 | MSVCRT + libstdc++ + static compile |
---|---|---|---|
Method | Binary Size | Comment |
---|---|---|
fstream | 925KB | Use fstream is not good for your health since std::locale bloats your binary. |
fast_io::obuf_file | 155KB | |
fast_io::c_file_unlocked | 157KB | I hacked MSVCRT's FILE* implementation |
fast_io::c_file | 157KB | Thread Safe. I hacked MSVCRT's FILE* implementation |
fast_io::filebuf_file | 933KB | I hacked libstdc++'s std::filebuf implementation. C++ stream sucks |
Generate 100000000 🚄 emojis by using the program in benchmarks/0020.utf/fill_nc.cc
Benchmarks are in examples/0043.iconv Universal iconv. (UTF-8 to GB18030 as an example) iconv test: | Platform | Windows | MinGW-W64 GCC 11.0.0 | MSVCRT + libstdc++ |
---|---|---|---|---|
Method | Elapsed time | Comment |
---|---|---|
iconv command | 1.529s | |
universal.cc | 1.293s | use POSIX libiconv |
UTF8->UTF16LE
Benchmarks are in examples/0022.utf
iconv test: | Platform | Windows | MinGW-W64 GCC 11.0.0 | MSVCRT + libstdc++ |
---|---|---|---|---|
Method | Elapsed time | Comment |
---|---|---|
iconv command | 0.967s | GNU iconv. No BOM which sucks |
utf8_file_to_utf16_file.cc | 0.498s | I use the SSE algorithms provided by the utf-utils project. |
UTF8->UTF32LE
Benchmarks are in examples/0022.utf
iconv test: | Platform | Windows | MinGW-W64 GCC 11.0.0 | MSVCRT + libstdc++ |
---|---|---|---|---|
Method | Elapsed time | Comment |
---|---|---|
iconv command | 0.844s | GNU iconv. No BOM which sucks |
utf8_file_to_utf32_file.cc | 0.442s | I use the SSE algorithms provided by the utf-utils project. |
The creation and development of this project were made possible thanks to the valuable contributions of various open-source projects. While the code was not copied directly from these projects, I used them as references and re-implemented them to suit the specific purposes of this library. In some cases, integration issues arose that required modifications to the original code. I am grateful to these projects and their developers for their commitment to making their code open and accessible to the wider community.
Project | Url |
---|---|
Grisu-Exact | https://github.com/jk-jeon/Grisu-Exact |
Ryu | https://github.com/ulfjack/ryu |
SHA-Intrinsics | https://github.com/noloader/SHA-Intrinsics |
SHA1 | https://github.com/vog/sha1 |
UTF-utils | https://github.com/BobSteagall/utf_utils |
jenkins-hash-java | https://github.com/vkandy/jenkins-hash-java |
md5 | https://github.com/JieweiWei/md5 |
ReactOS | https://github.com/reactos/reactos |
dirent_h | https://github.com/win32ports/dirent_h |
GNU C library | https://www.gnu.org/software/libc/ |
GNU Newlib | https://sourceware.org/newlib/ |
Dragonbox | https://github.com/jk-jeon/dragonbox |
JEAIII | https://github.com/jeaiii/itoa |
Crypto++ | https://github.com/weidai11/cryptopp |
MyItoA | https://gitee.com/xjkp2283572185/MyStd |