Method append

util/string/escape.cpp:341–343

TChar* UnescapeC(const TChar* str, size_t len, TChar* buf) {
    struct TUnboundedString {
        void append(TChar ch) noexcept {
            *P++ = ch;
        }

        void append(const TChar* b, const TChar* e) noexcept {
            while (b != e) {