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Fix handling of output iterators in format_to_n (#1506)

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This commit is contained in:
Victor Zverovich 2020-01-05 09:28:21 -10:00
parent aa07c57654
commit 9e3f3e8cff
2 changed files with 32 additions and 8 deletions
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13
include/fmt/format.h
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@ -395,6 +395,7 @@ template <typename OutputIt> class truncating_iterator_base {
public:
using iterator_category = std::output_iterator_tag;
using value_type = typename std::iterator_traits<OutputIt>::value_type;
using difference_type = void;
using pointer = void;
using reference = void;
@ -415,12 +416,10 @@ class truncating_iterator;
template <typename OutputIt>
class truncating_iterator<OutputIt, std::false_type>
: public truncating_iterator_base<OutputIt> {
using traits = std::iterator_traits<OutputIt>;
mutable typename traits::value_type blackhole_;
mutable typename truncating_iterator_base<OutputIt>::value_type blackhole_;
public:
using value_type = typename traits::value_type;
using value_type = typename truncating_iterator_base<OutputIt>::value_type;
truncating_iterator(OutputIt out, std::size_t limit)
: truncating_iterator_base<OutputIt>(out, limit) {}
@ -445,13 +444,11 @@ template <typename OutputIt>
class truncating_iterator<OutputIt, std::true_type>
: public truncating_iterator_base<OutputIt> {
public:
using value_type = typename OutputIt::container_type::value_type;
truncating_iterator(OutputIt out, std::size_t limit)
: truncating_iterator_base<OutputIt>(out, limit) {}
truncating_iterator& operator=(value_type val) {
if (this->count_++ < this->limit_) this->out_ = val;
template <typename T> truncating_iterator& operator=(T val) {
if (this->count_++ < this->limit_) *this->out_++ = val;
return *this;
}

27
test/format-test.cc
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@ -2080,6 +2080,33 @@ TEST(FormatTest, WideFormatToN) {
EXPECT_EQ(L"BC x", fmt::wstring_view(buffer, 4));
}
struct test_output_iterator {
char* data;
using iterator_category = std::output_iterator_tag;
using value_type = void;
using difference_type = void;
using pointer = void;
using reference = void;
test_output_iterator& operator++() {
++data;
return *this;
}
test_output_iterator operator++(int) {
auto tmp = *this;
++data;
return tmp;
}
char& operator*() { return *data; }
};
TEST(FormatTest, FormatToNOutputIterator) {
char buf[10] = {};
fmt::format_to_n(test_output_iterator{buf}, 10, "{}", 42);
EXPECT_STREQ(buf, "42");
}
#if FMT_USE_CONSTEXPR
struct test_arg_id_handler {
enum result { NONE, EMPTY, INDEX, NAME, ERROR };