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Sketch implementaion of try_lexical_cast

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This commit is contained in:
Antony Polukhin
2013-12-12 18:41:51 +04:00
parent 57e4e87e3b
commit 07082420b3
1 changed files with 129 additions and 39 deletions
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168
include/boost/lexical_cast.hpp
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@@ -2060,7 +2060,7 @@ namespace boost {
template<typename Target, typename Source>
struct lexical_cast_do_cast
{
static inline Target lexical_cast_impl(const Source& arg)
static inline bool try_lexical_cast_impl(const Source& arg, Target& result)
{
typedef lexical_cast_stream_traits<Source, Target> stream_trait;
@@ -2076,27 +2076,42 @@ namespace boost {
BOOST_DEDUCED_TYPENAME stream_trait::traits
> o_interpreter_type;
// Target type must be default constructible
Target result;
i_interpreter_type i_interpreter;
// Disabling ADL, by directly specifying operators.
const bool input_ok = (i_interpreter.operator <<(arg));
if (!(i_interpreter.operator <<(arg)))
return false;
o_interpreter_type out(i_interpreter.cbegin(), i_interpreter.cend());
// Disabling ADL, by directly specifying operators.
if(!input_ok || !(out.operator >>(result)))
BOOST_LCAST_THROW_BAD_CAST(Source, Target);
if(!(out.operator >>(result)))
return false;
return true;
}
static inline Target lexical_cast_impl(const Source& arg)
{
// Target type must be default constructible
Target result;
if(!try_lexical_cast_impl(arg, result))
BOOST_LCAST_THROW_BAD_CAST(Source, Target);
return result;
}
};
template <typename Source>
template <typename Target, typename Source>
struct lexical_cast_copy
{
static inline bool try_lexical_cast_impl(const Source& arg, Target& result)
{
result = arg;
return true;
}
static inline const Source& lexical_cast_impl(const Source &arg) BOOST_NOEXCEPT
{
return arg;
@@ -2201,6 +2216,17 @@ namespace boost {
template <typename Target, typename Source>
struct lexical_cast_dynamic_num
{
static inline bool try_lexical_cast_impl(const Source& arg, Target& result)
{
try {
result = lexical_cast_impl(arg);
} catch (const bad_lexical_cast& e) {
return false;
}
return true;
}
static inline Target lexical_cast_impl(const Source &arg)
{
typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
@@ -2224,46 +2250,63 @@ namespace boost {
return caster_type::lexical_cast_impl(arg);
}
};
template <typename Target, typename Source>
struct lexical_cast_caster_type_detector {
typedef BOOST_DEDUCED_TYPENAME boost::detail::array_to_pointer_decay<Source>::type src;
typedef BOOST_DEDUCED_TYPENAME boost::type_traits::ice_or<
boost::detail::is_xchar_to_xchar<Target, src >::value,
boost::detail::is_char_array_to_stdstring<Target, src >::value,
boost::type_traits::ice_and<
boost::is_same<Target, src >::value,
boost::detail::is_stdstring<Target >::value
>::value,
boost::type_traits::ice_and<
boost::is_same<Target, src >::value,
boost::detail::is_character<Target >::value
>::value
> shall_we_copy_t;
typedef boost::detail::is_arithmetic_and_not_xchars<Target, src >
shall_we_copy_with_dynamic_check_t;
// We do evaluate second `if_` lazily to avoid unnecessary instantiations
// of `shall_we_copy_with_dynamic_check_t` and improve compilation times.
typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
shall_we_copy_t::value,
boost::mpl::identity<boost::detail::lexical_cast_copy<Target, src > >,
boost::mpl::if_<
shall_we_copy_with_dynamic_check_t,
boost::detail::lexical_cast_dynamic_num<Target, src >,
boost::detail::lexical_cast_do_cast<Target, src >
>
>::type caster_type_lazy;
typedef BOOST_DEDUCED_TYPENAME caster_type_lazy::type caster_type;
};
}
template <typename Target, typename Source>
inline Target lexical_cast(const Source &arg)
{
typedef BOOST_DEDUCED_TYPENAME boost::detail::array_to_pointer_decay<Source>::type src;
typedef BOOST_DEDUCED_TYPENAME boost::type_traits::ice_or<
boost::detail::is_xchar_to_xchar<Target, src >::value,
boost::detail::is_char_array_to_stdstring<Target, src >::value,
boost::type_traits::ice_and<
boost::is_same<Target, src >::value,
boost::detail::is_stdstring<Target >::value
>::value,
boost::type_traits::ice_and<
boost::is_same<Target, src >::value,
boost::detail::is_character<Target >::value
>::value
> shall_we_copy_t;
typedef boost::detail::is_arithmetic_and_not_xchars<Target, src >
shall_we_copy_with_dynamic_check_t;
// We do evaluate second `if_` lazily to avoid unnecessary instantiations
// of `shall_we_copy_with_dynamic_check_t` and improve compilation times.
typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
shall_we_copy_t::value,
boost::mpl::identity<boost::detail::lexical_cast_copy<src > >,
boost::mpl::if_<
shall_we_copy_with_dynamic_check_t,
boost::detail::lexical_cast_dynamic_num<Target, src >,
boost::detail::lexical_cast_do_cast<Target, src >
>
>::type caster_type_lazy;
typedef BOOST_DEDUCED_TYPENAME caster_type_lazy::type caster_type;
typedef BOOST_DEDUCED_TYPENAME
boost::detail::lexical_cast_caster_type_detector<Target, Source>
::caster_type caster_type;
return caster_type::lexical_cast_impl(arg);
}
template <typename Target, typename Source>
inline bool try_lexical_cast(const Source &arg, Target& result)
{
typedef BOOST_DEDUCED_TYPENAME
boost::detail::lexical_cast_caster_type_detector<Target, Source>
::caster_type caster_type;
return caster_type::try_lexical_cast_impl(arg, result);
}
template <typename Target>
inline Target lexical_cast(const char* chars, std::size_t count)
{
@@ -2272,6 +2315,13 @@ namespace boost {
);
}
template <typename Target>
inline bool try_lexical_cast(const char* chars, std::size_t count, Target& result)
{
return ::boost::try_lexical_cast(
::boost::iterator_range<const char*>(chars, chars + count), result
);
}
template <typename Target>
inline Target lexical_cast(const unsigned char* chars, std::size_t count)
@@ -2281,6 +2331,14 @@ namespace boost {
);
}
template <typename Target>
inline bool try_lexical_cast(const unsigned char* chars, std::size_t count, Target& result)
{
return ::boost::try_lexical_cast(
::boost::iterator_range<const unsigned char*>(chars, chars + count), result
);
}
template <typename Target>
inline Target lexical_cast(const signed char* chars, std::size_t count)
{
@@ -2289,6 +2347,14 @@ namespace boost {
);
}
template <typename Target>
inline bool try_lexical_cast(const signed char* chars, std::size_t count, Target& result)
{
return ::boost::try_lexical_cast(
::boost::iterator_range<const signed char*>(chars, chars + count), result
);
}
#ifndef BOOST_LCAST_NO_WCHAR_T
template <typename Target>
inline Target lexical_cast(const wchar_t* chars, std::size_t count)
@@ -2297,6 +2363,14 @@ namespace boost {
::boost::iterator_range<const wchar_t*>(chars, chars + count)
);
}
template <typename Target>
inline bool try_lexical_cast(const wchar_t* chars, std::size_t count, Target& result)
{
return ::boost::try_lexical_cast(
::boost::iterator_range<const wchar_t*>(chars, chars + count), result
);
}
#endif
#ifndef BOOST_NO_CXX11_CHAR16_T
template <typename Target>
@@ -2306,6 +2380,14 @@ namespace boost {
::boost::iterator_range<const char16_t*>(chars, chars + count)
);
}
template <typename Target>
inline bool try_lexical_cast(const char16_t* chars, std::size_t count, Target& result)
{
return ::boost::try_lexical_cast(
::boost::iterator_range<const char16_t*>(chars, chars + count), result
);
}
#endif
#ifndef BOOST_NO_CXX11_CHAR32_T
template <typename Target>
@@ -2315,6 +2397,14 @@ namespace boost {
::boost::iterator_range<const char32_t*>(chars, chars + count)
);
}
template <typename Target>
inline bool try_lexical_cast(const char32_t* chars, std::size_t count, Target& result)
{
return ::boost::try_lexical_cast(
::boost::iterator_range<const char32_t*>(chars, chars + count), result
);
}
#endif
} // namespace boost