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// This source code is released into the public domain.
module;
#include <ucl.h>
export module nihil.ucl:emit;
import nihil.std;
import :object;
namespace nihil::ucl {
export enum struct emitter : std::uint8_t {
configuration = UCL_EMIT_CONFIG,
compact_json = UCL_EMIT_JSON_COMPACT,
json = UCL_EMIT_JSON,
yaml = UCL_EMIT_YAML,
};
// Wrap ucl_emitter_functions for a particular output iterator type.
//
// We can't throw exceptions here since we're called from C code. The emit
// functions return an integer value, but it's not really clear what this is
// for and the C API seems to mostly ignore it. So, we just eat errors and
// keep going.
template <std::output_iterator<char> Iterator>
struct emit_wrapper
{
explicit emit_wrapper(Iterator iterator)
: m_iterator(std::move(iterator))
{
}
static auto
append_character(unsigned char const c, std::size_t nchars, void *const ud) noexcept -> int
try {
auto &self = check_magic(ud);
self.m_iterator =
std::ranges::fill_n(self.m_iterator, nchars, static_cast<char>(c));
return 0;
} catch (...) {
return 0;
}
static auto append_len(unsigned char const *const str, std::size_t const len,
void *const ud) noexcept -> int
try {
auto &self = check_magic(ud);
self.m_iterator = std::ranges::copy(std::span(str, len), self.m_iterator).out;
return 0;
} catch (...) {
return 0;
}
static auto append_int(std::int64_t const value, void *const ud) noexcept -> int
try {
auto &self = check_magic(ud);
auto buf = std::array<char, std::numeric_limits<std::int64_t>::digits10>();
auto result = std::to_chars(begin(buf), end(buf), value, 10);
if (result.ec == std::errc()) {
auto chars = std::span(buf.data(), result.ptr);
self.m_iterator = std::ranges::copy(chars, self.m_iterator).out;
}
return 0;
} catch (...) {
return 0;
}
static auto append_double(double const value, void *const ud) noexcept -> int
try {
auto &self = check_magic(ud);
auto buf = std::array<char, std::numeric_limits<double>::digits10>();
auto result = std::to_chars(begin(buf), end(buf), value);
if (result.ec == std::errc()) {
auto chars = std::span(buf.data(), result.ptr);
self.m_iterator = std::ranges::copy(chars, self.m_iterator).out;
}
return 0;
} catch (...) {
return 0;
}
auto get_functions(this emit_wrapper &self) -> ucl_emitter_functions
{
auto ret = ucl_emitter_functions{};
ret.ucl_emitter_append_character = &emit_wrapper::append_character;
ret.ucl_emitter_append_len = &emit_wrapper::append_len;
ret.ucl_emitter_append_int = &emit_wrapper::append_int;
ret.ucl_emitter_append_double = &emit_wrapper::append_double;
ret.ud = &self;
return ret;
}
[[nodiscard]] auto iterator(this emit_wrapper &self) -> Iterator &
{
return self.m_iterator;
}
[[nodiscard]] auto iterator(this emit_wrapper const &self) -> Iterator const &
{
return self.m_iterator;
}
private:
Iterator m_iterator{};
std::uint64_t m_magic = wrapper_magic;
// Harden against memory errors.
static constexpr auto wrapper_magic = std::uint32_t{0x57524150};
static auto check_magic(void *p) -> emit_wrapper &
{
auto *ret = static_cast<emit_wrapper *>(p);
if (ret->m_magic != wrapper_magic)
throw std::runtime_error("Invalid emit_wrapper pointer");
return *ret;
}
};
export auto
emit(object const &object, emitter const format, std::output_iterator<char> auto &&it) -> void
{
auto ucl_format = static_cast<ucl_emitter>(format);
auto wrapper = emit_wrapper(it);
auto functions = wrapper.get_functions();
::ucl_object_emit_full(object.get_ucl_object(), ucl_format, &functions, nullptr);
}
// Basic ostream printer for UCL; default to JSON since it's probably what
// most people expect. Note that most derived UCL types override this.
export auto operator<<(std::ostream &stream, object const &o) -> std::ostream &
{
emit(o, emitter::json, std::ostream_iterator<char>(stream));
return stream;
}
} // namespace nihil::ucl
// Specialisation of std::formatter<> for object. Note that most derived
// UCL types override this.
template <std::derived_from<nihil::ucl::object> T>
struct std::formatter<T, char>
{
nihil::ucl::emitter emitter = nihil::ucl::emitter::json;
template <class ParseContext>
constexpr auto parse(ParseContext &ctx) -> ParseContext::iterator
{
auto it = ctx.begin();
auto end = ctx.end();
while (it != end) {
switch (*it) {
case 'j':
emitter = nihil::ucl::emitter::json;
break;
case 'J':
emitter = nihil::ucl::emitter::compact_json;
break;
case 'c':
emitter = nihil::ucl::emitter::configuration;
break;
case 'y':
emitter = nihil::ucl::emitter::yaml;
break;
case '}':
return it;
default:
throw std::format_error("Invalid format string for UCL object");
}
++it;
}
return it;
}
template <class FmtContext>
auto format(nihil::ucl::object const &o, FmtContext &ctx) const -> FmtContext::iterator
{
// We can't use emit() here since the context iterator is not
// an std::output_iterator.
auto out = ctx.out();
auto ucl_format = static_cast<::ucl_emitter>(emitter);
auto wrapper = nihil::ucl::emit_wrapper(out);
auto functions = wrapper.get_functions();
::ucl_object_emit_full(o.get_ucl_object(), ucl_format, &functions, nullptr);
return wrapper.iterator();
}
};
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