mirror/fmt
1
0
Fork 0
mirror of https://github.com/fmtlib/fmt.git synced 2024-11-07 08:31:16 +00:00
Code Issues Packages Projects Releases Wiki Activity

check for property 'mutable iterator' and SFINAE on it

Browse Source
This commit is contained in:
Daniela Engert 2018-10-25 15:22:27 +02:00 committed by Victor Zverovich
parent 2dea780fbd
commit 5ee1a4bc8a
2 changed files with 76 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
include/fmt/format.h
View File

@ -3396,6 +3396,51 @@ inline typename buffer_context<Char>::type::iterator format_to(
basic_format_args<context>(as));
}
namespace internal {
// Detect the iterator category of *any* given type in a SFINAE-friendly way.
// Unfortunately, older implementations of std::iterator_traits are not safe
// for use in a SFINAE-context.
// the gist of C++17's void_t magic
template<typename... Ts>
struct void_ { typedef void type; };
template <typename T, typename Enable = void>
struct it_category : std::false_type {};
template <typename T>
struct it_category<T*> { typedef std::random_access_iterator_tag type; };
template <typename T>
struct it_category<T, typename void_<typename T::iterator_category>::type> {
typedef typename T::iterator_category type;
};
// Detect if *any* given type models the OutputIterator concept
template <typename It>
class is_output_iterator {
// Check for mutability because all iterator categories derived from
// std::input_iterator_tag *may* also meet the requirements of an
// OutputIterator, thereby falling into the category of 'mutable iterators'
// [iterator.requirements.general] clause 4.
// The compiler reveals this property only at the point of *actually
// dereferencing* the iterator!
template <typename U>
static decltype(*(internal::declval<U>())) test(std::input_iterator_tag);
template <typename U>
static char& test(std::output_iterator_tag);
template <typename U>
static const char& test(...);
typedef decltype(test<It>(typename it_category<It>::type{})) type;
typedef typename std::remove_reference<type>::type result;
public:
static const bool value = !std::is_const<result>::value;
};
} // internal
template <typename OutputIt, typename Char = char>
//using format_context_t = basic_format_context<OutputIt, Char>;
struct format_context_t { typedef basic_format_context<OutputIt, Char> type; };
@ -3408,8 +3453,9 @@ struct format_args_t {
};
template <typename String, typename OutputIt, typename... Args>
inline OutputIt vformat_to(
OutputIt out, const String &format_str,
inline typename std::enable_if<internal::is_output_iterator<OutputIt>::value,
OutputIt>::type
vformat_to(OutputIt out, const String &format_str,
typename format_args_t<OutputIt, FMT_CHAR(String)>::type args) {
typedef output_range<OutputIt, FMT_CHAR(String)> range;
return vformat_to<arg_formatter<range>>(range(out),
@ -3428,7 +3474,9 @@ inline OutputIt vformat_to(
\endrst
*/
template <typename OutputIt, typename S, typename... Args>
inline FMT_ENABLE_IF_STRING(S, OutputIt)
inline typename std::enable_if<
internal::is_string<S>::value &&
internal::is_output_iterator<OutputIt>::value, OutputIt>::type
format_to(OutputIt out, const S &format_str, const Args &... args) {
internal::check_format_string<Args...>(format_str);
typedef typename format_context_t<OutputIt, FMT_CHAR(S)>::type context;
@ -3464,7 +3512,9 @@ inline format_arg_store<
}
template <typename OutputIt, typename Char, typename... Args>
inline format_to_n_result<OutputIt> vformat_to_n(
inline typename std::enable_if<
internal::is_output_iterator<OutputIt>::value,
format_to_n_result<OutputIt>>::type vformat_to_n(
OutputIt out, std::size_t n, basic_string_view<Char> format_str,
typename format_to_n_args<OutputIt, Char>::type args) {
typedef internal::truncating_iterator<OutputIt> It;
@ -3480,7 +3530,10 @@ inline format_to_n_result<OutputIt> vformat_to_n(
\endrst
*/
template <typename OutputIt, typename S, typename... Args>
inline FMT_ENABLE_IF_STRING(S, format_to_n_result<OutputIt>)
inline typename std::enable_if<
internal::is_string<S>::value &&
internal::is_output_iterator<OutputIt>::value,
format_to_n_result<OutputIt>>::type
format_to_n(OutputIt out, std::size_t n, const S &format_str,
const Args &... args) {
internal::check_format_string<Args...>(format_str);

18
test/format-test.cc
View File

@ -197,6 +197,24 @@ TEST(IteratorTest, TruncatingBackInserter) {
EXPECT_EQ(buffer, "42");
}
TEST(IteratorTest, IsOutputIterator) {
EXPECT_TRUE(fmt::internal::is_output_iterator<char*>::value);
EXPECT_FALSE(fmt::internal::is_output_iterator<const char*>::value);
EXPECT_FALSE(fmt::internal::is_output_iterator<std::string>::value);
EXPECT_TRUE(fmt::internal::is_output_iterator<
std::back_insert_iterator<std::string>>::value);
EXPECT_TRUE(fmt::internal::is_output_iterator<
std::string::iterator>::value);
EXPECT_FALSE(fmt::internal::is_output_iterator<
std::string::const_iterator>::value);
EXPECT_FALSE(fmt::internal::is_output_iterator<std::list<char>>::value);
EXPECT_TRUE(fmt::internal::is_output_iterator<
std::list<char>::iterator>::value);
EXPECT_FALSE(fmt::internal::is_output_iterator<
std::list<char>::const_iterator>::value);
EXPECT_FALSE(fmt::internal::is_output_iterator<uint32_pair>::value);
}
TEST(MemoryBufferTest, Ctor) {
basic_memory_buffer<char, 123> buffer;
EXPECT_EQ(static_cast<size_t>(0), buffer.size());