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Implement fmt::format_to into std::vector<char> #4211

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merged 2 commits into from
Oct 26, 2024
Merged

Implement fmt::format_to into std::vector<char> #4211

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64a55ba
Implement fmt::format_to into std::vector<char>
phprus Oct 21, 2024
ca497db
Move get_container to the trait
phprus Oct 23, 2024
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24 changes: 23 additions & 1 deletion include/fmt/base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1973,15 +1973,37 @@ template <typename T = char> class counting_buffer : public buffer<T> {
template <typename T>
struct is_back_insert_iterator<basic_appender<T>> : std::true_type {};

template <typename OutputIt, typename InputIt, typename = void>
struct has_back_insert_iterator_container_append : std::false_type {};
template <typename OutputIt, typename InputIt>
struct has_back_insert_iterator_container_append<
OutputIt, InputIt,
void_t<decltype(get_container(std::declval<OutputIt>())
.append(std::declval<InputIt>(),
std::declval<InputIt>()))>> : std::true_type {};

// An optimized version of std::copy with the output value type (T).
template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value)>
FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value&&
has_back_insert_iterator_container_append<
OutputIt, InputIt>::value)>
FMT_CONSTEXPR20 auto copy(InputIt begin, InputIt end, OutputIt out)
-> OutputIt {
get_container(out).append(begin, end);
return out;
}

template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value &&
!has_back_insert_iterator_container_append<
OutputIt, InputIt>::value)>
FMT_CONSTEXPR20 auto copy(InputIt begin, InputIt end, OutputIt out)
-> OutputIt {
auto& c = get_container(out);
c.insert(c.end(), begin, end);
return out;
}

template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(!is_back_insert_iterator<OutputIt>::value)>
FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
Expand Down
11 changes: 8 additions & 3 deletions test/compile-test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
#include "fmt/compile.h"

#include <type_traits>
#include <vector>

#include "fmt/chrono.h"
#include "fmt/ranges.h"
Expand Down Expand Up @@ -229,10 +230,14 @@ TEST(compile_test, unknown_format_fallback) {
EXPECT_EQ(" 42 ",
fmt::format(FMT_COMPILE("{name:^4}"), fmt::arg("name", 42)));

std::vector<char> v;
fmt::format_to(std::back_inserter(v), FMT_COMPILE("{name:^4}"),
std::vector<char> v1;
fmt::format_to(std::back_inserter(v1), FMT_COMPILE("{}"), 42);
EXPECT_EQ("42", fmt::string_view(v1.data(), v1.size()));

std::vector<char> v2;
fmt::format_to(std::back_inserter(v2), FMT_COMPILE("{name:^4}"),
fmt::arg("name", 42));
EXPECT_EQ(" 42 ", fmt::string_view(v.data(), v.size()));
EXPECT_EQ(" 42 ", fmt::string_view(v2.data(), v2.size()));

char buffer[4];
auto result = fmt::format_to_n(buffer, 4, FMT_COMPILE("{name:^5}"),
Expand Down