cpp_util::cstring_view

Implementation of P1402R0 for a cstring_view.

Mimics (and delegates most of its functionality to) a std::basic_string_view, but removes all functions that could potentially break the invariant of null termination.

Changes compared to P1402R0

• The conversion from a std::string to a basic_cstring_view is implemented using a special constructor, since it is not possible to add a function to the std::basic_string class.

• Moved the null_terminated_t into the basic_cstring_view class definition.

• Enabled all char8_t functionality only conditionally if the feature test macro __cpp_char8_t is defined.

• Renamed the suffix literal for a basic_cstring_view from csv to _csv since only standard library suffixes can omit the _.

• Corrected constexpr string_view_type substr(size_type pos = 0, size_type n) const; and removed the default parameter from the first parameter.

• Enabled starts_with and ends_with delegation to std::string_view only if the feature test macro __cpp_lib_starts_ends_with is defined, otherwise a custom implementation based on cppreference is used.

• Added contains() functions proposed for C++23.

• Added custom assert() to various functions.

• Implemented the comparison functions using operator== and operator<=> if the feature test macros __cpp_impl_three_way_comparison and __cpp_lib_three_way_comparison are defined.

• Added ranges helper templates, which are only enabled if the feature test macro __cpp_lib_ranges is defined.

• Added support for std::format if the feature test macro __cpp_lib_format is defined.

• Added [[nodiscard]] to almost all functions.

Prerequisites

Any compiler supporting C++17 should be sufficient (for more information see Compiler Support). Additionally, at least CMake 3.30 is required.

The tests are implemented using Catch2, which gets shipped as single header file with this repository.

Building and Running the Examples

Building with GCC, Clang, or MSVC can be done using CMake presets.

git clone [email protected]:breyerml/cstring_view.git
cd cstring_view
cmake --preset [preset] -DCPP_UTIL_BUILD_EXAMPLES .
cmake --build --preset [preset]
./build/cstring_view_examples

Where [preset] is one of gcc, clang, or msvc.

Building and Running the Tests

To additionally build the tests and run them use:

cmake --preset [preset] -DCPP_UTIL_ENABLE_TESTS .
cmake --build --preset [preset]
ctest --preset [preset]

Tests for all supported C++ standards starting with C++17 for the currently used compiler are generated.

Compiler Support

The cpp_util::cstring_view has been tested with the following compilers, all installed using the respective package manager and GitHub actions (other compilers or compiler versions may also be supported):

Compiler	Versions
GCC	9.5.0, 10.5.0, 11.4.0, 12.3.0
Clang	11.1.0, 12.0.1, 13.0.1, 14.0.0, 15.0.7
MSVC	19.29.30154.0

All tests were run using the following compiler flags:

• GCC: -Wall -Wextra -Wpedantic -Werror

• Clang: -Weverything -Wno-c++98-compat -Wno-c++98-compat-pedantic -Wno-unknown-warning-option -Wno-zero-as-null-pointer-constant -Wno-reserved-identifier -Werror

  • -Wno-c++98-compat -Wno-c++98-compat-pedantic: since C++98 is not supported
  • -Wno-unknown-warning-option: due to clang-11.1.0 and clang-12.0.1 not recognizing the Wno-reserved-identifier option
  • -Wno-zero-as-null-pointer-constant: due to a warning generated by clang11.1.0 in the Catch2 header
  • -Wno-reserved-identifier: due to a warning generated by clang-13.0.1 when using the custom _csv literals

• MSVC: /W4 /EHsc /WX

Compiler Standard Version

• C++17:

  • the minimum required standard version enabling all functions

• C++20:

  • the implementation of the starts_with and ends_with functions is now delegated to the respective std::string_view implementation
  • the relational operators are now implemented in terms of the three-way comparison operator operator<=>(const basic_cstring_view&, const basic_cstring_view&)
  • add support for char8_t string views
  • add support for std::ranges

The actual features are enabled using the specific features test macros and not the __cplusplus macro.