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make format_int constexpr #4032

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merged 4 commits into from
Jun 23, 2024
Merged

make format_int constexpr #4032

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9e2efbf
make format_int constexpr
dixlorenz Jun 21, 2024
92a9bd3
format_int can only be constexpr in C++20
dixlorenz Jun 21, 2024
17918c6
apply clang-format
dixlorenz Jun 22, 2024
d4fe2e6
drop constexpr for str()
dixlorenz Jun 22, 2024
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32 changes: 20 additions & 12 deletions include/fmt/format.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3918,12 +3918,14 @@ class format_int {
mutable char buffer_[buffer_size];
char* str_;

template <typename UInt> auto format_unsigned(UInt value) -> char* {
template <typename UInt>
FMT_CONSTEXPR20 auto format_unsigned(UInt value) -> char* {
auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
return detail::format_decimal(buffer_, n, buffer_size - 1).begin;
}

template <typename Int> auto format_signed(Int value) -> char* {
template <typename Int>
FMT_CONSTEXPR20 auto format_signed(Int value) -> char* {
auto abs_value = static_cast<detail::uint32_or_64_or_128_t<Int>>(value);
bool negative = value < 0;
if (negative) abs_value = 0 - abs_value;
Expand All @@ -3933,32 +3935,38 @@ class format_int {
}

public:
explicit format_int(int value) : str_(format_signed(value)) {}
explicit format_int(long value) : str_(format_signed(value)) {}
explicit format_int(long long value) : str_(format_signed(value)) {}
explicit format_int(unsigned value) : str_(format_unsigned(value)) {}
explicit format_int(unsigned long value) : str_(format_unsigned(value)) {}
explicit format_int(unsigned long long value)
explicit FMT_CONSTEXPR20 format_int(int value) : str_(format_signed(value)) {}
explicit FMT_CONSTEXPR20 format_int(long value)
: str_(format_signed(value)) {}
explicit FMT_CONSTEXPR20 format_int(long long value)
: str_(format_signed(value)) {}
explicit FMT_CONSTEXPR20 format_int(unsigned value)
: str_(format_unsigned(value)) {}
explicit FMT_CONSTEXPR20 format_int(unsigned long value)
: str_(format_unsigned(value)) {}
explicit FMT_CONSTEXPR20 format_int(unsigned long long value)
: str_(format_unsigned(value)) {}

/// Returns the number of characters written to the output buffer.
auto size() const -> size_t {
FMT_CONSTEXPR20 auto size() const -> size_t {
return detail::to_unsigned(buffer_ - str_ + buffer_size - 1);
}

/// Returns a pointer to the output buffer content. No terminating null
/// character is appended.
auto data() const -> const char* { return str_; }
FMT_CONSTEXPR20 auto data() const -> const char* { return str_; }

/// Returns a pointer to the output buffer content with terminating null
/// character appended.
auto c_str() const -> const char* {
FMT_CONSTEXPR20 auto c_str() const -> const char* {
buffer_[buffer_size - 1] = '\0';
return str_;
}

/// Returns the content of the output buffer as an `std::string`.
auto str() const -> std::string { return std::string(str_, size()); }
FMT_CONSTEXPR20 auto str() const -> std::string {
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Let's drop FMT_CONSTEXPR20 here since constexpr std::string is less widely available.

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ok, one can always write a constexpr free function for it (I did anyway)

return std::string(str_, size());
}
};

template <typename T, typename Char>
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