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#include "common/perf_counters_key.h"
#include <algorithm>
#include <iterator>
#include <numeric>
namespace ceph::perf_counters {
namespace detail {
// use a null character to delimit strings
constexpr char DELIMITER = '\0';
// write a delimited string to the output
auto write(std::string_view str, std::output_iterator<char> auto out)
{
out = std::copy(str.begin(), str.end(), out);
*(out++) = DELIMITER;
return out;
}
// return the encoded size of a label
inline std::size_t label_size(const label_pair& l)
{
return l.first.size() + sizeof(DELIMITER)
+ l.second.size() + sizeof(DELIMITER);
}
// an output iterator that writes label_pairs to a flat buffer
template <std::contiguous_iterator Iterator>
class label_insert_iterator {
using base_iterator = Iterator;
struct label_writer {
base_iterator pos; // write position
label_writer& operator=(const label_pair& l) {
pos = write(l.first, pos);
pos = write(l.second, pos);
return *this;
}
};
label_writer label;
public:
using difference_type = std::ptrdiff_t;
using value_type = label_writer;
using reference = value_type&;
label_insert_iterator() = default;
label_insert_iterator(base_iterator begin) : label{begin} {
static_assert(std::output_iterator<label_insert_iterator, label_pair>);
}
// increments are noops
label_insert_iterator& operator++() { return *this; }
label_insert_iterator operator++(int) { return *this; }
// can only dereference to assign
reference operator*() { return label; }
// return the wrapped iterator position
base_iterator base() { return label.pos; }
};
// compare label_pairs by their key only
bool label_key_less(const label_pair& lhs, const label_pair& rhs)
{
return lhs.first < rhs.first;
}
bool label_key_equal(const label_pair& lhs, const label_pair& rhs)
{
return lhs.first == rhs.first;
}
std::string create(std::string_view counter_name,
label_pair* begin, label_pair* end)
{
// sort the input labels and remove duplicate keys
std::sort(begin, end, label_key_less);
end = std::unique(begin, end, label_key_equal);
// calculate the total size and preallocate the buffer
auto size = std::accumulate(begin, end,
counter_name.size() + sizeof(DELIMITER),
[] (std::size_t sum, const label_pair& l) {
return sum + label_size(l);
});
std::string result;
result.resize(size);
// copy out the counter name and labels
auto out = result.begin();
out = write(counter_name, out);
std::copy(begin, end, label_insert_iterator{out});
return result;
}
std::string insert(const char* begin1, const char* end1,
label_pair* begin2, label_pair* end2)
{
// sort the input labels and remove duplicate keys
std::sort(begin2, end2, label_key_less);
end2 = std::unique(begin2, end2, label_key_equal);
// find the first delimiter that marks the end of the counter name
auto pos = std::find(begin1, end1, DELIMITER);
// calculate the total size and preallocate the buffer
auto size = std::distance(begin1, end1);
if (pos == end1) { // add a delimiter if the key doesn't have one
size += sizeof(DELIMITER);
}
size = std::accumulate(begin2, end2, size,
[] (std::size_t sum, const label_pair& l) {
return sum + label_size(l);
});
std::string result;
result.resize(size);
// copy the counter name without the delimiter
auto out = std::copy(begin1, pos, result.begin());
if (pos != end1) {
++pos; // advance past the delimiter
}
*(out++) = DELIMITER;
// merge the two sorted input ranges, drop any duplicate keys, and write
// them to output. the begin2 range is first so that new input labels can
// replace existing duplicates
auto end = std::set_union(begin2, end2,
label_iterator{pos, end1},
label_iterator{end1, end1},
label_insert_iterator{out},
label_key_less);
// fix up the size in case set_union() removed any duplicates
result.resize(std::distance(result.begin(), end.base()));
return result;
}
std::string_view name(const char* begin, const char* end)
{
auto pos = std::find(begin, end, DELIMITER);
return {begin, pos};
}
std::string_view labels(const char* begin, const char* end)
{
auto pos = std::find(begin, end, DELIMITER);
if (pos == end) {
return {};
}
return {std::next(pos), end};
}
} // namespace detail
std::string key_create(std::string_view counter_name)
{
label_pair* end = nullptr;
return detail::create(counter_name, end, end);
}
std::string_view key_name(std::string_view key)
{
return detail::name(key.begin(), key.end());
}
label_range key_labels(std::string_view key)
{
return detail::labels(key.begin(), key.end());
}
label_iterator::label_iterator(base_iterator begin, base_iterator end)
: state(make_state(begin, end))
{
static_assert(std::forward_iterator<label_iterator>);
}
void label_iterator::advance(std::optional<iterator_state>& s)
{
auto d = std::find(s->pos, s->end, detail::DELIMITER);
if (d == s->end) { // no delimiter for label key
s = std::nullopt;
return;
}
s->label.first = std::string_view{s->pos, d};
s->pos = std::next(d);
d = std::find(s->pos, s->end, detail::DELIMITER);
if (d == s->end) { // no delimiter for label name
s = std::nullopt;
return;
}
s->label.second = std::string_view{s->pos, d};
s->pos = std::next(d);
}
auto label_iterator::make_state(base_iterator begin, base_iterator end)
-> std::optional<iterator_state>
{
std::optional state = iterator_state{begin, end};
advance(state);
return state;
}
label_iterator& label_iterator::operator++()
{
advance(state);
return *this;
}
label_iterator label_iterator::operator++(int)
{
label_iterator tmp = *this;
advance(state);
return tmp;
}
} // namespace ceph::perf_counters
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