问题描述
有没有更好的方法来做到这一点?我觉得这样维护起来会很糟糕。
const unsigned int set_max {32};
std::vector<unsigned int> base;
base.reserve(argc-1);
for (int i = 1; i < argc; ++i) {
unsigned long tmp;
try { tmp = std::stoul(argv[i],nullptr,10); }
catch (std::invalid_argument) { std::cerr << "Invalid base! Conversion Failed.\n"; return -2; }
catch (std::out_of_range) { std::cerr << "Invalid base! Too large.\n"; return -2; }
if (tmp > std::numeric_limits<unsigned int>::max()) { std::cerr << "Invalid base! Too large.\n"; return -2; }
if (tmp < 2) { std::cerr << "Invalid base! Must at least be 2.\n"; return -2; }
if (tmp > set_max) { std::cerr << "Invalid base! Must be within " << set_max << ".\n"; return -2; }
base.push_back(static_cast<unsigned int>(tmp));
}
编辑:转贴here
解决方法
我建议将逻辑拆分为实用程序函数,以使每个操作更易于管理,例如:
enum class eConvFailure {NoError,ConvFailed,OutOfRange,TooSmall,TooLarge};
std::pair<unsigned int,eConvFailure> my_stoui(const std::string &s)
{
unsigned long tmp;
try
{
tmp = std::stoul(s,nullptr,10);
if (tmp > std::numeric_limits<unsigned int>::max()) {
throw std::out_of_range("");
}
}
catch (const std::invalid_argument &) {
return std::make_pair(0,eConvFailure::ConvFailed);
}
catch (const std::out_of_range &) {
return std::make_pair(0,eConvFailure::OutOfRange);
}
/* alternatively:
errno = 0;
tmp = std::stroul(s.c_str(),10);
if (errno != 0) {
if (tmp == ULONG_MAX && errno == ERANGE)
return std::make_pair(0,eConvFailure::OutOfRange);
else
return std::make_pair(0,eConvFailure::ConvFailed);
}
if (tmp > std::numeric_limits<unsigned int>::max()) {
return std::make_pair(0,eConvFailure::TooLarge);
}
*/
return std::make_pair(static_cast<unsigned int>(tmp),eConvFailure::NoError);
}
std::pair<unsigned int,eConvFailure> my_stoui(const std::string &s,unsigned int max_value)
{
auto res = my_stoui(s);
if (res.second != eConvFailure::NoError) {
return res;
}
if (res.first < 2) {
return std::make_pair(0,eConvFailure::TooSmall);
}
if (res.first > max_value) {
return std::make_pair(0,eConvFailure::TooLarge);
}
return res;
}
const unsigned int set_max {32};
std::string reason(eConvFailure err) {
switch (err) {
case eConvFailure::ConvFailure: return "Conversion Failed";
case eConvFailure::OutOfRange: return "Too Large";
case eConvFailure::TooSmall: return "Must at least be 2";
case eConvFailure::TooLarge: return "Must be within " + std::to_string(set_max);
default: return "Error " + std::to_string(static_cast<int>(eConvFailure));
}
}
std::vector<unsigned int> base;
base.reserve(argc-1);
for (int i = 1; i < argc; ++i) {
auto res = my_stoui(argv[i],set_max);
if (res.second != eConvFailure::NoError) {
std::cerr << "Invalid base! " << reason(res.second) << ".\n";
return -2;
}
base.push_back(res.first);
}
或者,您可以使用异常处理来代替,例如:
unsigned int my_stoui(const std::string &s)
{
unsigned long tmp = std::stoul(s,10);
if (tmp > std::numeric_limits<unsigned int>::max()) {
throw std::out_of_range("");
}
return static_cast<unsigned int>(tmp);
}
unsigned int my_stoui(const std::string &s,unsigned int max_value)
{
unsigned int tmp = my_stoui(s);
if (tmp < 2) {
throw std::runtime_error("Must at least be 2");
}
if (tmp > max_value) {
return std::runtime_error("Must be within " + std::to_string(max_value));
}
return tmp;
}
const unsigned int set_max {32};
std::vector<unsigned int> base;
base.reserve(argc-1);
try
{
for (int i = 1; i < argc; ++i) {
base.push_back(my_stoui(argv[i],set_max));
}
}
catch (const std::exception &ex)
{
std::cerr << "Invalid base! ";
if (dynamic_cast<const std::invalid_argument*>(&ex)) {
std::cerr << "Conversion failed";
}
else if (dynamic_cast<const std::out_of_range*>(&ex)) {
std::cerr << "Too large";
}
else {
std::cerr << ex.what();
}
std::cerr << ".\n";
return -2;
}