下面是一个不分配任何临时变量的一种方法:
// https://github.com/KubaO/stackoverflown/tree/master/questions/string-sep-42276882
#include <QtCore>
QString separate1(const QString & string, const QString & separator) {
QString result;
result.reserve(string.size() * (1 + separator.size()));
for (auto ch : string) {
result.append(ch);
result.append(separator);
}
result.chop(separator.size());
return result;
}
唉,QString
的写入时复制还是有一定的开销,因此处理数据直接将更快:
QString separate(const QString & string, const QString & separator) {
QString result{string.size() + (string.size()-1) * separator.size(),
Qt::Uninitialized};
auto const end = result.data() + result.size();
int s{};
for (auto p = result.data(); p < end;) {
*p++ = string.at(s++);
if (Q_LIKELY(p < end))
for (auto const ch : separator)
*p++ = ch;
}
return result;
}
,并检查出来:
int main() {
auto const separator = QStringLiteral("-");
auto const source = QStringLiteral("Hello world!");
auto const compare = QStringLiteral("H-e-l-l-o- -w-o-r-l-d-!");
Q_ASSERT(separate1(source, separator) == compare);
Q_ASSERT(separate(source, separator) == compare);
}