diff --git a/README.md b/README.md index 9f9efe1..f2c55e1 100644 --- a/README.md +++ b/README.md @@ -5,7 +5,7 @@ * Convert any integral type to a string at compile-time * Supports converting to any base between 2 and 36 inclusive * No external dependencies, only includes `type_traits` for template parameter checking -* Works best in C++20 GCC or C++17/20 Clang +* Supports custom character types, e.g. `to_string<123, 10, wchar_t>` **How to use:** @@ -22,31 +22,31 @@ With `to_string`, all that will be found in program disassembly are the resultin Try it [on Compiler Explorer](https://godbolt.org/z/T-MFoh). -**Known issues:** - -* With C++17 GCC, `to_string` must be used to initialize variables; otherwise, the integer-string conversion is done at run-time. - # How it works The basic structure of `to_string` is shown below: ```cpp -template +template struct to_string_t { - char buf[]; // Size selection explained later. - constexpr to_string_t() {} // Converts the integer to a string stored in buf. - constexpr operator char *() {} // These allow for the object to be implicitly converted - constexpr operator const char *() {} // to a character pointer. + char_type buf[]; // Size selection explained later. + constexpr to_string_t() {} // Converts the integer to a string stored in buf. + constexpr operator char_type *() {} // These allow for the object to be implicitly converted + constexpr operator const char_type *() {} // to a character pointer. + + // begin() and end() are supported too. }; -template -to_string_t to_string; // Simplifies usage: to_string_t() becomes to_string. +template +constexpr to_string_t to_string; // Simplifies usage, e.g. to_string_t<367>() becomes to_string<367>. ``` Since the number and base are template parameters, each differing `to_string` use will get its own character buffer. The integer/string conversion is done using a simple method I learned over the years, where the string is built in reverse using `n % base` to calculate the value of the lowest digit: +(*Note: The below examples of code are not up-to-date, though they still give a general idea of how `to_string` works.*) + ```cpp constexpr to_string_t() { auto ptr = buf + sizeof(buf) / sizeof(buf[0]); diff --git a/to_string.hpp b/to_string.hpp index 6117258..bf724cd 100644 --- a/to_string.hpp +++ b/to_string.hpp @@ -15,49 +15,60 @@ * @tparam N Number to convert * @tparam base Desired base, can be from 2 to 36 */ -template, int> = 0, std::enable_if_t<(base > 1 && base < 37), int> = 0> -struct to_string_t { +class to_string_t { // The lambda calculates what the string length of N will be, so that `buf` // fits to the number perfectly. - char buf[([] { - unsigned int len = N >= 0 ? 1 : 2; - for (auto n = N; n; len++, n /= base); - return len; - }())]; + char_type buf[([]() constexpr noexcept { + unsigned int len = N > 0 ? 1 : 2; + for (auto n = N; n; len++, n /= base); + return len; + }())] = {}; + public: /** * Constructs the object, filling `buf` with the string representation of N. */ - constexpr to_string_t() { - auto ptr = buf + sizeof(buf) / sizeof(buf[0]); + constexpr to_string_t() noexcept { + auto ptr = end(); *--ptr = '\0'; - for (auto n = N; n; n /= base) - *--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[(N < 0 ? -1 : 1) * (n % base)]; - if (N < 0) - *--ptr = '-'; + if (N != 0) { + for (auto n = N < 0 ? -N : N; n; n /= base) + *--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[(N < 0 ? -1 : 1) * (n % base)]; + if (N < 0) + *--ptr = '-'; + } else { + buf[0] = '0'; + } } - /** - * Allows implicit conversion of this object to a `char *`. - */ - constexpr operator char *() { - return buf; - } - - /** - * Allows implicit conversion of this object to a `const char *`. - */ - constexpr operator const char *() const { - return buf; - } + // Support implicit casting to `char *` or `const char *`. + constexpr operator char_type *() noexcept { return buf; } + constexpr operator const char_type *() const noexcept { return buf; } + + constexpr auto size() const noexcept { return sizeof(buf) / sizeof(buf[0]); } + // Element access + constexpr auto data() noexcept { return buf; } + constexpr const auto data() const noexcept { return buf; } + constexpr auto& operator[](unsigned int i) noexcept { return buf[i]; } + constexpr const auto& operator[](unsigned int i) const noexcept { return buf[i]; } + constexpr auto& front() noexcept { return buf[0]; } + constexpr const auto& front() const noexcept { return buf[0]; } + constexpr auto& back() noexcept { return buf[size() - 1]; } + constexpr const auto& back() const noexcept { return buf[size() - 1]; } + // Iterators + constexpr auto begin() noexcept { return buf; } + constexpr const auto begin() const noexcept { return buf; } + constexpr auto end() noexcept { return buf + size(); } + constexpr const auto end() const noexcept { return buf + size(); } }; /** * Simplifies use of `to_string_t` from `to_string_t()` to `to_string`. */ -template -to_string_t to_string; - +template +constexpr to_string_t to_string; + #endif // TCSULLIVAN_TO_STRING_HPP_