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Merged
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Jan 21, 2026
Merged

Use C++20 iterator concepts in our format headers #497

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15 changes: 15 additions & 0 deletions libbroker/broker/detail/type_traits.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include "broker/fwd.hh"

#include <cstddef>
#include <iterator>
#include <list>
#include <map>
#include <optional>
Expand All @@ -13,6 +14,10 @@
#include <variant>
#include <vector>

namespace caf {
enum class byte : uint8_t;
}

namespace broker {

class data;
Expand Down Expand Up @@ -246,6 +251,16 @@ concept has_string_getter = requires(const T& t) {
{ t.string() } -> std::convertible_to<std::string_view>;
};

template <class T>
concept byte_output_iterator =
std::output_iterator<T, std::byte> || std::output_iterator<T, caf::byte>;

template <class T>
concept char_output_iterator = std::output_iterator<T, char>;

template <class T>
concept arithmetic = std::is_arithmetic_v<T>;

} // namespace broker::detail

#define BROKER_DEF_HAS_ENCODE_IN_NS(ns_name) \
Expand Down
80 changes: 37 additions & 43 deletions libbroker/broker/format/bin.hh
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Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
#pragma once

#include "broker/config.hh"
#include "broker/data.hh"
#include "broker/detail/type_traits.hh"
#include "broker/variant.hh"
Expand All @@ -12,7 +11,6 @@
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <vector>

namespace broker::format::bin::v1 {

Expand All @@ -23,9 +21,8 @@ uint32_t to_network_order_impl(uint32_t value);
uint64_t to_network_order_impl(uint64_t value);

/// Converts `value` from native to network byte order.
template <class T>
template <std::unsigned_integral T>
T to_network_order(T value) {
static_assert(std::is_unsigned_v<T>);
if constexpr (sizeof(T) == 2) {
auto res = to_network_order_impl(static_cast<uint16_t>(value));
return static_cast<T>(res);
Expand All @@ -40,7 +37,7 @@ T to_network_order(T value) {
}

/// Converts `value` from network to native byte order.
template <class T>
template <std::unsigned_integral T>
T from_network_order(T value) {
// swapping the bytes again gives the native order
return to_network_order(value);
Expand Down Expand Up @@ -95,7 +92,7 @@ bool read(const_byte_pointer& first, const_byte_pointer last, double& result);
bool read_varbyte(const_byte_pointer& first, const_byte_pointer last,
size_t& result);

template <class OutIter>
template <detail::byte_output_iterator OutIter>
struct value_type_oracle {
using type = typename std::iterator_traits<OutIter>::value_type;
};
Expand All @@ -106,7 +103,7 @@ struct value_type_oracle<std::back_insert_iterator<Container>> {
};

/// Deduces the value type of an output iterator.
template <class OutIter>
template <detail::byte_output_iterator OutIter>
using iter_value_t = typename value_type_oracle<OutIter>::type;

template <class WriteFn>
Expand Down Expand Up @@ -134,7 +131,7 @@ inline size_t varbyte_size(size_t value) {
}

/// Encodes `value` to a variable-length byte sequence and appends it to `out`.
template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter write_varbyte(size_t value, OutIter out) {
return write_varbyte_impl(value, [out](auto* begin, auto* end) {
using value_type = iter_value_t<OutIter>;
Expand All @@ -144,7 +141,7 @@ OutIter write_varbyte(size_t value, OutIter out) {
}

/// Encodes `value` to its binary representation and appends it to `out`.
template <class T, class OutIter>
template <class T, detail::byte_output_iterator OutIter>
OutIter write_unsigned(T value, OutIter out) {
if constexpr (std::is_enum_v<T>) {
return write_unsigned(static_cast<std::underlying_type_t<T>>(value), out);
Expand All @@ -160,15 +157,15 @@ OutIter write_unsigned(T value, OutIter out) {
}
}

template <class T, class OutIter>
template <class T, detail::byte_output_iterator OutIter>
OutIter write_bytes(const T* first, const T* last, OutIter out) {
static_assert(sizeof(T) == 1);
using val_t = iter_value_t<OutIter>;
return std::copy(reinterpret_cast<const val_t*>(first),
reinterpret_cast<const val_t*>(last), out);
}

template <class Container, class OutIter>
template <class Container, detail::byte_output_iterator OutIter>
OutIter write_bytes(const Container& in, OutIter out) {
return write_bytes(in.data(), in.data() + in.size(), out);
}
Expand Down Expand Up @@ -209,19 +206,18 @@ auto encoded_values(const Buffer& buf) {
return std::make_pair(begin, end);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(none, OutIter out) {
return out;
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(std::byte value, OutIter out) {
return write_unsigned(value, out);
}

/// Encodes `value` to its binary representation and appends it to `out`.
template <class T, class OutIter>
requires(std::is_arithmetic_v<T>)
template <detail::arithmetic T, detail::byte_output_iterator OutIter>
OutIter encode(T value, OutIter out) {
if constexpr (std::is_same_v<T, bool>) {
return write_unsigned(static_cast<uint8_t>(value), out);
Expand All @@ -236,68 +232,68 @@ OutIter encode(T value, OutIter out) {
}
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(std::string_view value, OutIter out) {
out = write_varbyte(value.size(), out);
return write_bytes(value, out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const address& value, OutIter out) {
return write_bytes(value.bytes(), out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const subnet& value, OutIter out) {
out = write_bytes(value.network().bytes(), out);
return write_unsigned(value.raw_len(), out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(port value, OutIter out) {
out = write_unsigned(value.number(), out);
return write_unsigned(value.type(), out);
}

template <class Rep, class Period, class OutIter>
template <class Rep, class Period, detail::byte_output_iterator OutIter>
OutIter encode(std::chrono::duration<Rep, Period> value, OutIter out) {
return encode(value.count(), out);
}

template <class Clock, class Duration, class OutIter>
template <class Clock, class Duration, detail::byte_output_iterator OutIter>
OutIter encode(std::chrono::time_point<Clock, Duration> value, OutIter out) {
return encode(value.time_since_epoch(), out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const enum_value& value, OutIter out) {
out = write_varbyte(value.name.size(), out);
return write_bytes(value.name, out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(enum_value_view value, OutIter out) {
out = write_varbyte(value.name.size(), out);
return write_bytes(value.name, out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_data& value, OutIter out);

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant& value, OutIter out) {
return encode(*value.raw(), out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_data::set* values, OutIter out) {
out = write_varbyte(values->size(), out);
for (const auto& x : *values)
out = encode(x, out);
return out;
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_data::table* values, OutIter out) {
out = write_varbyte(values->size(), out);
for (const auto& [key, val] : *values) {
Expand All @@ -307,49 +303,48 @@ OutIter encode(const variant_data::table* values, OutIter out) {
return out;
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_data::list* values, OutIter out) {
out = write_varbyte(values->size(), out);
for (const auto& x : *values)
out = encode(x, out);
return out;
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_list& values, OutIter out) {
return encode(values.raw(), out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_set& values, OutIter out) {
return encode(values.raw(), out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_table& values, OutIter out) {
return encode(values.raw(), out);
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const variant_data& value, OutIter out) {
out = write_unsigned(value.get_tag(), out);
return std::visit([&](const auto& x) { return encode(x, out); }, value.value);
}

// Note: enable_if trickery to suppress implicit conversions.
template <class Data, class OutIter>
requires std::is_same_v<Data, data>
template <std::same_as<data> Data, detail::byte_output_iterator OutIter>
OutIter encode(const Data& value, OutIter out);

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const broker::set& values, OutIter out) {
out = write_varbyte(values.size(), out);
for (const auto& x : values)
out = encode(x, out);
return out;
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const broker::table& values, OutIter out) {
out = write_varbyte(values.size(), out);
for (const auto& [key, val] : values) {
Expand All @@ -359,16 +354,15 @@ OutIter encode(const broker::table& values, OutIter out) {
return out;
}

template <class OutIter>
template <detail::byte_output_iterator OutIter>
OutIter encode(const broker::vector& values, OutIter out) {
out = write_varbyte(values.size(), out);
for (const auto& x : values)
out = encode(x, out);
return out;
}

template <class Data, class OutIter>
requires std::is_same_v<Data, data>
template <std::same_as<data> Data, detail::byte_output_iterator OutIter>
OutIter encode(const Data& value, OutIter out) {
return std::visit(
[&](const auto& x) {
Expand All @@ -386,7 +380,7 @@ OutIter encode(const Data& value, OutIter out) {
/// @param last The last byte of the encoded sequence.
/// @param out The buffer to write to.
/// @pre `first` and `last` must be a valid range.
template <class InputIter, class Sentinel, class OutIter>
template <class InputIter, class Sentinel, detail::byte_output_iterator OutIter>
OutIter write_sequence(data::type tag, size_t num_elements, InputIter first,
Sentinel last, OutIter out) {
out = write_unsigned(tag, out);
Expand All @@ -397,7 +391,7 @@ OutIter write_sequence(data::type tag, size_t num_elements, InputIter first,
BROKER_DEF_HAS_ENCODE_IN_NS(broker::format::bin::v1);

/// Adapter for the `inspect` API.
template <class OutIter>
template <detail::byte_output_iterator OutIter>
class encoder {
public:
static constexpr bool is_loading = false;
Expand Down Expand Up @@ -503,7 +497,7 @@ public:
return fields(values...);
}

template <class Iterator, class Sentinel>
template <std::input_iterator Iterator, std::sentinel_for<Iterator> Sentinel>
void append(Iterator first, Sentinel last) {
out_ = std::copy(first, last, out_);
}
Expand Down Expand Up @@ -892,7 +886,7 @@ private:
const_byte_pointer end_;
};

template <class OutIter, class T>
template <detail::byte_output_iterator OutIter, class T>
auto encode_with_tag(const T& x, OutIter out) -> decltype(encode(x, out)) {
return encode(x, write_unsigned(data_tag_v<T>, out));
}
Expand Down
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