This adds some comments to explain what this rather subtle code is
doing. It also replaces string::copy with using char_traits::copy
directly, because the bounds checks and length adjustments that
string::copy does are redundant here - we already ensure the lengths are
correct.
Tested x86_64-linux.
-- >8 --
libstdc++-v3/ChangeLog:
* include/std/format (__formatter_fp::_M_localize): Add comments
and micro-optimize string copy.
---
libstdc++-v3/include/std/format | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index 52243eb5479..e963d7f79b3 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -1886,25 +1886,28 @@ namespace __format
if (__grp.empty() && __point == __dot)
return __lstr; // Locale uses '.' and no grouping.
- size_t __d = __str.find(__dot);
- size_t __e = min(__d, __str.find(__exp));
+ size_t __d = __str.find(__dot); // Index of radix character (if any).
+ size_t __e = min(__d, __str.find(__exp)); // First of radix or exponent
if (__e == __str.npos)
__e = __str.size();
- const size_t __r = __str.size() - __e;
+ const size_t __r = __str.size() - __e; // Length of remainder.
auto __overwrite = [&](_CharT* __p, size_t) {
+ // Apply grouping to the digits before the radix or exponent.
auto __end = std::__add_grouping(__p, __np.thousands_sep(),
__grp.data(), __grp.size(),
__str.data(), __str.data() + __e);
- if (__r)
+ if (__r) // If there's a fractional part or exponent
{
if (__d != __str.npos)
{
- *__end = __point;
+ *__end = __point; // Add the locale's radix character.
++__end;
++__e;
}
- if (__r > 1)
- __end += __str.copy(__end, __str.npos, __e);
+ const size_t __rlen = __str.size() - __e;
+ // Append fractional digits and/or exponent:
+ char_traits<_CharT>::copy(__end, __str.data() + __e, __rlen);
+ __end += __rlen;
}
return (__end - __p);
};
--
2.46.0
