# toml++ (tomlplusplus) · [][cpp_compilers] [][v0.5.0] [](https://circleci.com/gh/marzer/tomlplusplus) [](./LICENSE)
- Header-only
- C++17 (plus some C++20 features where available, e.g. experimental support for char8_t strings)
- [TOML v0.5.0](https://github.com/toml-lang/toml/blob/master/versions/en/toml-v0.5.0.md), plus support for some
[unreleased TOML language features] (these are optional)
- Proper UTF-8 handling (incl. BOM)
- Works with or without exceptions
- Doesn't require RTTI
- First-class support for serializing to JSON
- Tested on Clang and GCC and MSVC (VS2019)
# Example
Given a TOML file `configuration.toml` containing the following:
```toml
[library]
name = "toml++"
version = "0.1.0"
authors = ["Mark Gillard "]
[dependencies]
cpp = 17
```
Reading it in C++ is easy with `toml++`:
```cpp
auto config = toml::parse_file( "configuration.toml" );
// get key-value pairs
std::string_view library_name = config["library"]["name"].value_or(""sv);
std::string_view library_version = config["library"]["version"].value_or(""sv);
std::string_view library_author = config["library"]["authors"][0].value_or(""sv);
int64_t depends_on_cpp_version = config["dependencies"]["cpp"].value_or(0);
// modify the data
config.insert_or_assign("alternatives", toml::array{
"cpptoml",
"toml11",
"Boost.TOML"
});
// iterate & visit over the data
for (auto [k, v] : config)
{
v.visit([](auto& node) noexcept
{
std::cout << node << std:endl;
if constexpr (toml::is_string)
do_something_with_string_values(node);
});
}
// re-serialize as TOML
std::cout << config << std::endl;
// re-serialize as JSON
std::cout << toml::json_formatter{ config } << std::endl;
```
You'll find some more code examples in the `examples` directory, and plenty more as part of the [API documentation].
# Adding toml++ to your project
`toml++` comes in two flavours: Regular and Single-header.
### Regular mode
1. Add `tomlplusplus/include` to your include paths
2. `#include `
### Single-header mode
1. Drop `toml.hpp` wherever you like in your source tree
2. There is no step two
The API is the same regardless of how you consume the library.
### Configuration
A number of configurable options are exposed in the form of preprocessor `#defines`. Most likely you
won't need to mess with these at all, butif you do, set them before including toml++.
| Option | Type | Default | Description |
|----------------------------|:--------------:|-----------------------------------|----------------------------------------------------------------------------------------------------------|
| `TOML_ASSERT(expr)` | function macro | `assert(expr)`
(or undefined) | Sets the assert function used by the library. |
| `TOML_CHAR_8_STRINGS` | boolean | `0` | Uses C++20 [char8_t]-based strings as the toml string data type. **_Experimental!_** |
| `TOML_CONFIG_HEADER` | string literal | undefined | Includes the given header file before the rest of the library. |
| `TOML_LARGE_FILES` | boolean | `0` | Uses 32-bit integers for line and column indices (instead of 16-bit). |
| `TOML_SMALL_FLOAT_TYPE` | type name | undefined | If your codebase has an additional 'small' float type (e.g. half-precision), this tells toml++ about it. |
| `TOML_SMALL_INT_TYPE` | type name | undefined | If your codebase has an additional 'small' integer type (e.g. 24-bits), this tells toml++ about it. |
| `TOML_UNDEF_MACROS` | boolean | `1` | `#undefs` the library's internal macros at the end of the header. |
| `TOML_UNRELEASED_FEATURES` | boolean | `1` | Enables support for [unreleased TOML language features] not yet part of a [numbered version]. |
# TOML Language Support
At any given time `toml++` aims to implement whatever the [numbered version] of TOML is, with the
addition of unreleased features from the [TOML master] and some sane cherry-picks from the
[TOML issues list] where the discussion strongly indicates inclusion in a near-future release.
The library advertises the most recent numbered language version it fully supports via the preprocessor
defines `TOML_LANG_MAJOR`, `TOML_LANG_MINOR` and `TOML_LANG_PATCH`.
### **🔸Unreleased TOML features:**
- [#356]: Allow leading zeros in the exponent part of a float
- [#516]: Allow newlines and trailing commas in inline tables
- [#562]: Allow hex floatingpoint values
- [#567]: Clarify that control characters are not permitted in comments
- [#571]: Allow raw tabs inside strings
- [#644]: Support `+` in key names
- [#665]: Make arrays heterogeneous
- [#671]: Local time of day format should support `09:30` as opposed to `09:30:00`
- [#687]: Relax bare key restrictions to allow additional unicode characters
_These can be disabled (and thus strict [TOML v0.5.0] compliance enforced) by specifying
`TOML_UNRELEASED_FEATURES = 0` (see [Configuration](#Configuration))._
### **🔹TOML v0.5.0 and earlier:**
- All features supported.
# Contributing
Contributions are very welcome! Either by [reporting issues] or submitting pull requests.
If you wish to submit a pull request, please see [CONTRIBUTING] for all the details you need to get going.
# License and Attribution
`toml++` is licensed under the terms of the MIT license - see [LICENSE].
UTF-8 decoding is performed using a state machine based on Bjoern Hoehrmann's '[Flexible and Economical UTF-8 Decoder]',
which is also subject to the terms of the MIT license - see [LICENSE-utf8-decoder].
[API documentation]: https://marzer.github.io/tomlplusplus/
[unreleased TOML language features]: #unreleased-toml-features
[numbered version]: https://github.com/toml-lang/toml/releases
[char8_t]: https://en.cppreference.com/w/cpp/keyword/char8_t
[TOML master]: https://github.com/toml-lang/toml/blob/master/README.md
[TOML issues list]: https://github.com/toml-lang/toml/issues
[TOML v0.5.0]: https://github.com/toml-lang/toml/blob/master/versions/en/toml-v0.5.0.md
[v0.5.0]: https://github.com/toml-lang/toml/blob/master/versions/en/toml-v0.5.0.md
[CONTRIBUTING]: ./CONTRIBUTING.md
[LICENSE]: ./LICENSE
[Flexible and Economical UTF-8 Decoder]: http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
[cpp_compilers]: https://en.cppreference.com/w/cpp/compiler_support
[reporting issues]: https://github.com/marzer/tomlplusplus/issues
[#356]: https://github.com/toml-lang/toml/issues/356
[#516]: https://github.com/toml-lang/toml/issues/516
[#562]: https://github.com/toml-lang/toml/issues/562
[#567]: https://github.com/toml-lang/toml/issues/567
[#571]: https://github.com/toml-lang/toml/issues/571
[#622]: https://github.com/toml-lang/toml/issues/622
[#644]: https://github.com/toml-lang/toml/issues/644
[#665]: https://github.com/toml-lang/toml/issues/665
[#671]: https://github.com/toml-lang/toml/issues/671
[#687]: https://github.com/toml-lang/toml/issues/687
[LICENSE-utf8-decoder]: ./LICENSE-utf8-decoder