Function GetValuePtrByPath

library/cpp/json/writer/json_value.cpp:819–855

        template <bool Create, class TJsonPtr>
        TJsonPtr GetValuePtrByPath(TJsonPtr currentJson, TStringBuf path, char delimiter) noexcept(!Create) {
            static_assert(
                !(Create && std::is_const<std::remove_pointer_t<TJsonPtr>>::value),
                "TJsonPtr must be a `TJsonValue*` if `Create` is true");
            constexpr std::integral_constant<bool, Create> create_tag{};

            while (!path.empty()) {
                i64 index = 0;
                const TStringBuf step = path.NextTok(delimiter);
                if (step.size() > 2 && *step.begin() == '[' && step.back() == ']' && TryFromString(step.substr(1, step.size() - 2), index)) {
                    if (index < 0) {
                        if constexpr (Create) {
                            currentJson->SetType(JSON_ARRAY);
                            TJsonArray::TArray& dst = currentJson->GetArraySafe();
                            while (i64(dst.size()) < -index) {
                                dst.push_front({JSON_NULL});
                            }
                        }
                        index = i64(currentJson->GetArray().size()) - (-index);
                    }
                    if (index < 0) {
                        return nullptr;
                    }
                    currentJson = CreateOrNullptr(currentJson, index, create_tag);
                } else if (Create && step == "[]") {
                    if constexpr (Create) {
                        currentJson = &currentJson->AppendValue({});
                    }
                } else {
                    currentJson = CreateOrNullptr(currentJson, step, create_tag);
                }
                if (!currentJson) {
                    return nullptr;
                }
            }
            return currentJson;
        }
    } // anonymous namespace

    bool TJsonValue::GetValueByPath(const TStringBuf path, TJsonValue& result, char delimiter) const {