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Merged
wenchy merged 7 commits into from
Aug 25, 2025
Merged

cpp(localtime): cross-platform optimization for printing localtime #125

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c49562c
feat: thread safe localtime
Kybxd Aug 23, 2025
62b3d4f
feat: better support for c++20
Kybxd Aug 23, 2025
73b3677
feat: ignore std::chrono::
Kybxd Aug 23, 2025
537a970
feat: remove func LocalTime
Kybxd Aug 23, 2025
310f500
feat: use namespace sc
Kybxd Aug 23, 2025
637531a
feat: revert changes
Kybxd Aug 25, 2025
5ef6ad7
feat: use -j instead of --parallel for cmake
Kybxd Aug 25, 2025
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4 changes: 2 additions & 2 deletions README.md
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Expand Up @@ -26,7 +26,7 @@ The official config loader for [Tableau](https://github.com/tableauio/tableau).
- C++17: `cmake -S . -B build`
- C++20: `cmake -S . -B build -DCMAKE_CXX_STANDARD=20`
- clang: `cmake -S . -B build -DCMAKE_CXX_COMPILER=clang++`
- Build: `cmake --build build --parallel 10`
- Build: `cmake --build build -j16`
- Run: `./bin/loader`

### Dev at Windows
Expand All @@ -36,7 +36,7 @@ The official config loader for [Tableau](https://github.com/tableauio/tableau).
- CMake:
- C++17: `cmake -S . -B build -G "NMake Makefiles"`
- C++20: `cmake -S . -B build -G "NMake Makefiles" -DCMAKE_CXX_STANDARD=20`
- Build: `cmake --build build --parallel 10`
- Build: `cmake --build build`
- Run: `.\bin\loader.exe`

### References
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20 changes: 16 additions & 4 deletions cmd/protoc-gen-cpp-tableau-loader/embed/logger.pc.cc
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Expand Up @@ -96,10 +96,22 @@ void DefaultWrite(std::ostream* os, const SourceLocation& loc, const LevelInfo&

std::ostream& operator<<(std::ostream& os, const Now&) {
auto now = std::chrono::system_clock::now();
auto now_time_t = std::chrono::system_clock::to_time_t(now);
auto now_us = std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()) % 1000000;
return os << std::put_time(std::localtime(&now_time_t), "%F %T") << "." << std::setw(6) << std::setfill('0')
<< now_us.count();
#if __cplusplus >= 202002L
auto zt = std::chrono::zoned_time(std::chrono::current_zone(), std::chrono::floor<std::chrono::microseconds>(now));
return os << std::format("{:%F %T}", zt);
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@wenchy wenchy Aug 25, 2025

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Also should shows 6 decimal places (microseconds):

    std::cout << chrono::format("{:%F %T}", zt); // prints up to seconds, no fraction
    
    // To print fractional seconds:
    // The standard chrono format supports floating-point seconds with `%S` by specifying precision:
    std::cout << chrono::format("{:%F %H:%M:%S.%6f}", zt); // shows 6 decimal places (microseconds)

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@Kybxd Kybxd Aug 25, 2025 •
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Decimals are added by default when printing std::chrono::zoned_time by "%S" with an accuracy of nanoseconds, so std::chrono::floor is used here to limit it to an accuracy of microseconds

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@Kybxd Kybxd Aug 25, 2025

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test result:
企业微信截图_1756106376500

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@wenchy wenchy Aug 25, 2025

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LGTM

#else
static thread_local std::tm tm;
auto now_t = std::chrono::system_clock::to_time_t(now);
#ifdef _WIN32
localtime_s(&tm, &now_t);
#else
localtime_r(&now_t, &tm);
#endif
auto duration = now.time_since_epoch();
auto secs = std::chrono::duration_cast<std::chrono::seconds>(duration);
auto micros = std::chrono::duration_cast<std::chrono::microseconds>(duration - secs);
return os << std::put_time(&tm, "%F %T") << "." << std::setw(6) << std::setfill('0') << micros.count();
#endif
}

} // namespace log
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2 changes: 1 addition & 1 deletion init.bat
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Expand Up @@ -21,6 +21,6 @@ cmake -S . -B build ^
-DCMAKE_POLICY_VERSION_MINIMUM="3.5"

REM Compile the code
cmake --build build --parallel 10
cmake --build build

endlocal
2 changes: 1 addition & 1 deletion init.sh
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Expand Up @@ -26,4 +26,4 @@ cmake -S . -B build \
-DCMAKE_BUILD_TYPE=Debug

# Compile the code
cmake --build build --parallel 10
cmake --build build -j16
20 changes: 16 additions & 4 deletions test/cpp-tableau-loader/src/protoconf/logger.pc.cc
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Expand Up @@ -101,10 +101,22 @@ void DefaultWrite(std::ostream* os, const SourceLocation& loc, const LevelInfo&

std::ostream& operator<<(std::ostream& os, const Now&) {
auto now = std::chrono::system_clock::now();
auto now_time_t = std::chrono::system_clock::to_time_t(now);
auto now_us = std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()) % 1000000;
return os << std::put_time(std::localtime(&now_time_t), "%F %T") << "." << std::setw(6) << std::setfill('0')
<< now_us.count();
#if __cplusplus >= 202002L
auto zt = std::chrono::zoned_time(std::chrono::current_zone(), std::chrono::floor<std::chrono::microseconds>(now));
return os << std::format("{:%F %T}", zt);
#else
static thread_local std::tm tm;
auto now_t = std::chrono::system_clock::to_time_t(now);
#ifdef _WIN32
localtime_s(&tm, &now_t);
#else
localtime_r(&now_t, &tm);
#endif
auto duration = now.time_since_epoch();
auto secs = std::chrono::duration_cast<std::chrono::seconds>(duration);
auto micros = std::chrono::duration_cast<std::chrono::microseconds>(duration - secs);
return os << std::put_time(&tm, "%F %T") << "." << std::setw(6) << std::setfill('0') << micros.count();
#endif
}

} // namespace log
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