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string: upgrade vappendf and appendf to return number of chars appended

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This comes handy when concatenating strings and calculating mappings.

Signed-off-by: Simon Rozman <simon@rozman.si>
This commit is contained in:
Simon Rozman 2023-11-17 14:59:29 +01:00
parent 10791467d8
commit 06da717405
1 changed files with 17 additions and 12 deletions
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17
include/stdex/string.hpp
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@ -1238,8 +1238,10 @@ namespace stdex
/// \param[in ] locale Stdlib locale used to perform formatting. Use `NULL` to use locale globally set by `setlocale()`. /// \param[in ] locale Stdlib locale used to perform formatting. Use `NULL` to use locale globally set by `setlocale()`.
/// \param[in ] arg Arguments to `format` /// \param[in ] arg Arguments to `format`
/// ///
/// \return Number of appended code units
///
template<class _Elem, class _Traits, class _Ax> template<class _Elem, class _Traits, class _Ax>
inline void vappendf(_Inout_ std::basic_string<_Elem, _Traits, _Ax> &str, _In_z_ _Printf_format_string_params_(2) const _Elem *format, _In_opt_ locale_t locale, _In_ va_list arg) inline size_t vappendf(_Inout_ std::basic_string<_Elem, _Traits, _Ax> &str, _In_z_ _Printf_format_string_params_(2) const _Elem *format, _In_opt_ locale_t locale, _In_ va_list arg)
{ {
_Elem buf[1024/sizeof(_Elem)]; _Elem buf[1024/sizeof(_Elem)];
@ -1248,15 +1250,15 @@ namespace stdex
if (count >= 0) { if (count >= 0) {
// Copy from stack. // Copy from stack.
str.append(buf, count); str.append(buf, count);
} else { return count;
}
for (size_t capacity = 2*1024/sizeof(_Elem);; capacity *= 2) { for (size_t capacity = 2*1024/sizeof(_Elem);; capacity *= 2) {
// Allocate on heap and retry. // Allocate on heap and retry.
auto buf_dyn = std::make_unique<_Elem[]>(capacity); auto buf_dyn = std::make_unique<_Elem[]>(capacity);
count = vsnprintf(buf_dyn.get(), capacity - 1, format, locale, arg); count = vsnprintf(buf_dyn.get(), capacity - 1, format, locale, arg);
if (count >= 0) { if (count >= 0) {
str.append(buf_dyn.get(), count); str.append(buf_dyn.get(), count);
break; return count;
}
} }
} }
} }
@ -1268,13 +1270,16 @@ namespace stdex
/// \param[in ] format String template using `printf()` style /// \param[in ] format String template using `printf()` style
/// \param[in ] locale Stdlib locale used to perform formatting. Use `NULL` to use locale globally set by `setlocale()`. /// \param[in ] locale Stdlib locale used to perform formatting. Use `NULL` to use locale globally set by `setlocale()`.
/// ///
/// \return Number of appended code units
///
template<class _Elem, class _Traits, class _Ax> template<class _Elem, class _Traits, class _Ax>
inline void appendf(_Inout_ std::basic_string<_Elem, _Traits, _Ax> &str, _In_z_ _Printf_format_string_params_(2) const _Elem *format, _In_opt_ locale_t locale, ...) inline size_t appendf(_Inout_ std::basic_string<_Elem, _Traits, _Ax> &str, _In_z_ _Printf_format_string_params_(2) const _Elem *format, _In_opt_ locale_t locale, ...)
{ {
va_list arg; va_list arg;
va_start(arg, locale); va_start(arg, locale);
vappendf(str, format, locale, arg); size_t n = vappendf(str, format, locale, arg);
va_end(arg); va_end(arg);
return n;
} }
/// ///