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https://github.com/beached/ostreams
A constexpr output streams library
https://github.com/beached/ostreams
constexpr cpp cpp14 outputstream
Last synced: 4 days ago
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A constexpr output streams library
- Host: GitHub
- URL: https://github.com/beached/ostreams
- Owner: beached
- License: mit
- Created: 2018-08-29T18:45:22.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2020-09-26T23:29:02.000Z (over 4 years ago)
- Last Synced: 2024-11-10T15:11:46.360Z (2 months ago)
- Topics: constexpr, cpp, cpp14, outputstream
- Language: C++
- Homepage:
- Size: 146 KB
- Stars: 0
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# ostreams
A constexpr output stream implementation. See [tests](https://github.com/beached/ostreams/tree/master/tests) for example of usage
To create a formatted buffer
```cpp
daw::static_string_t buffer{}; // Uses a static string, but any contiguous memory area is fine
buffer.resize(buffer.size( )); // makes static string marked as fully used
auto buff_stream = daw::io::make_memory_buffer_stream( buffer.data( ), buffer.size( ) ); // create stream
buff_stream << "The meaning of life is " << 42 << '\n';
buffer.shrink_to_fit( ); // reclaim unused space in buffer
```
Console output
```cpp
daw::con_out << "The meaning of life is " << 42 << '\n';
```
File output
```cpp
auto fs = daw::make_file_stream( "file_name" );
if( !fs ) {
daw::con_err << "Error opening file\n";
exit( EXIT_FAILURE );
}
fs << "The meaining of life is " << 42 << '\n';
fs.close( ); // or let it go out of scope
```
## Extending to your classes
Add a function ``` to_os_string( ClassType ) ``` in your classes namespace that returns a type that is string like(has ``` data( ) ``` and ``` size( ) ```methods). If you want constexpr formatting this function must be constexpr. The provided ``` static_string_t ``` can help or a ``` string_view ``` may work too.
Custom streams must provide ``` operator() ``` for character and string like data. They must also specialize ``` daw::io::supports_output_stream_interface ``` to inherit from ``` std::true_type ```
Otherwise, for composite classes you would overload ``` operator<< ``` like in C++ iostreams. The requirement being that it is a template and uses SFINAE to only allow when ``` daw::io::is_output_stream_v == true ```.
## Benchmarks
Using a format string(or equivilent) of `"The asnwer to the meaning of life is %d %f\n"` with a double of 42.0
The following are the results:
#### Mac 2017 Macbook Air - 1.8 GHz Intel Core i5
| method | count | total time | item time |
|--------------------|--------|-------------|-----------|
| daw::memory_stream | 100000 | 13.90ms | 138.99ns |
| snprintf | 100000 | 31.98ms | 319.83ns |
| std::string_stream | 100000 | 77.30ms | 772.96ns |
| printf | 100000 | 170.57ms | 1.71us |
| daw::con_err | 100000 | 573.81ms | 5.74us |
| std::cerr | 100000 | 800.21ms | 8.00us |
#### Windows Intel i7-7500U
| method | count | total time | item time |
|--------------------|--------|-------------|-----------|
| daw::memory_stream | 100000 | 21.70ms | 217.00ns |
| snprintf | 100000 | 96.02ms | 960.96ns |
| std::string_stream | 100000 | 127.61ms | 1.28us |
| daw::con_err | 100000 | 326.27ms | 3.26us |
| std::cerr | 100000 | 842.78ms | 8.43us |
| printf | 100000 | 3.99s | 39.86us |
# Round trip errors
Tested using strtod/strtof to return string to a double/float
| type| value| output| difference |
|-----|------|-------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| double| 0.1| 0.1| 0 |
| double| 0.12| 0.11999999999999998| -1.38778e-17 |
| double| 0.123| 0.12299999999999999| -1.38778e-17 |
| double| 0.1234| 0.12339999999999998| -1.38778e-17 |
| double| 1.2345| 1.23449999999999992| 0 |
| double| 0.333333| 0.33333333333333332| 0 |
| double| 0.666667| 0.66666666666666665| 0 |
| double| 3.33333| 3.33333333333333349| 0 |
| double| 6.66667| 6.66666666666666698| 0 |
| double| 2.22507e-308| 0.0000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 0000000022250738585072009| -4.94066e-324 |
| double| -2.22507e-308| -0.00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 000000022250738585072009| 4.94066e-324 |
| double| 1.79769e+308| 17976931348623156600000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 000000000| 0 |
| double| 4.94066e-324| 0| -4.94066e-324 |
| double| 4| 3.99999999999999953| 0 |
| double| 8.98847e+307| 89884656743115786500000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000| 0 |
| float| 0.1| 0.1| 0 |
| float| 0.12| 0.119999996| 0 |
| float| 0.123| 0.123000001| 0 |
| float| 0.1234| 0.123400000| 0 |
| float| 1.2345| 1.234500046| 0 |
| float| 0.333333| 0.333333330| 0 |
| float| 0.666667| 0.666666660| 0 |
| float| 3.33333| 3.333333240| 0 |
| float| 6.66667| 6.666666481| 0 |
| float| 1.17549e-38| 0.0000000000000000000000000000000000000117549440| 0 |
| float| 3.40282e+38| 340282346300000000000000000000000000000| 0 |
| float| 1.4013e-45| 0| -1.4013e-45 |
| float| 4| 3.999999788| 0 |
| float| 1.70141e+38| 170141175700000000000000000000000000000| 0 |