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Micro-optimize parsing

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This commit is contained in:
Victor Zverovich 2018-09-04 15:37:31 -07:00
parent be0e268468
commit 2117775747
1 changed files with 17 additions and 15 deletions
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32
include/fmt/format.h
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@ -2102,21 +2102,21 @@ struct id_adapter {
Handler &handler;
};
template <bool IS_CONSTEXPR, class InputIt, class T>
FMT_CONSTEXPR InputIt find(InputIt first, InputIt last, const T &value) {
for (; first != last; ++first) {
if (*first == value)
return first;
// Return the result via the out param to workaround gcc bug 77539.
template <bool IS_CONSTEXPR, typename T, typename Ptr = const T*>
FMT_CONSTEXPR bool find(Ptr first, Ptr last, T value, Ptr &out) {
for (out = first; out != last; ++out) {
if (*out == value)
return true;
}
return last;
return false;
}
template <>
inline const char *find<false, const char*, char>(
const char *first, const char *last, const char &value) {
auto result = static_cast<const char*>(
std::memchr(first, value, last - first));
return result ? result : last;
inline bool find<false, char>(
const char *first, const char *last, char value, const char *&out) {
out = static_cast<const char*>(std::memchr(first, value, last - first));
return out != FMT_NULL;
}
template <bool IS_CONSTEXPR, typename Char, typename Handler>
@ -2125,8 +2125,8 @@ FMT_CONSTEXPR void parse_format_string(
struct writer {
FMT_CONSTEXPR void operator()(const Char *begin, const Char *end) {
for (;;) {
auto p = find<IS_CONSTEXPR>(begin, end, '}');
if (p == end) {
const Char *p = FMT_NULL;
if (!find<IS_CONSTEXPR>(begin, end, '}', p)) {
handler_.on_text(begin, end);
return;
}
@ -2146,8 +2146,8 @@ FMT_CONSTEXPR void parse_format_string(
for (;;) {
// Doing two passes with memchr (one for '{' and another for '}') is up to
// 2.5x faster than the naive one-pass implementation on long format strings.
auto p = find<IS_CONSTEXPR>(begin, end, '{');
if (p == end) {
const Char *p = FMT_NULL;
if (!find<IS_CONSTEXPR>(begin, end, '{', p)) {
if (begin != end)
write(begin, end);
return;
@ -2176,6 +2176,8 @@ FMT_CONSTEXPR void parse_format_string(
return;
}
begin = pointer_from(it) + 1;
if (begin == end)
return;
}
}