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btcsignals: use a single shared_ptr for liveness and callback

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This simplifies the implementation and eliminates an unnecessary shared_ptr.

Suggested by Marco Falke.

<Co-authored-by: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>
This commit is contained in:
Cory Fields
2026-03-06 19:09:03 +00:00
parent b12f43a0a8
commit 242b0ebb5c
1 changed files with 24 additions and 23 deletions
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47
src/btcsignals.h
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@@ -56,23 +56,28 @@ class connection
{
template <typename Signature, typename Combiner>
friend class signal;
/*
* Tag for the constructor used by signal.
/**
* Track liveness. Also serves as a tag for the constructor used by signal.
*/
struct enabled_tag_type {
class liveness
{
friend class connection;
std::atomic_bool m_connected{true};
void disconnect() { m_connected.store(false); }
public:
bool connected() const { return m_connected.load(); }
};
static constexpr enabled_tag_type enabled_tag{};
/**
* connections have shared_ptr-like copy and move semantics.
*/
std::shared_ptr<std::atomic_bool> m_connected{};
std::shared_ptr<liveness> m_state{};
/**
* Only a signal can create an enabled connection.
*/
explicit connection(enabled_tag_type /*unused*/) : m_connected{std::make_shared<std::atomic_bool>(true)} {}
explicit connection(std::shared_ptr<liveness>&& state) : m_state{std::move(state)}{}
public:
/**
@@ -92,8 +97,8 @@ public:
*/
void disconnect()
{
if (m_connected) {
m_connected->store(false);
if (m_state) {
m_state->disconnect();
}
}
@@ -103,7 +108,7 @@ public:
*/
bool connected() const
{
return m_connected && m_connected->load();
return m_state && m_state->connected();
}
};
@@ -148,23 +153,19 @@ class signal
static_assert(std::is_same_v<Combiner, optional_last_value<typename function_type::result_type>>, "only the optional_last_value combiner is supported");
/*
* Helper struct for maintaining a callback and its associated connection
* Helper struct for maintaining a callback and its associated connection liveness
*/
struct connection_holder {
struct connection_holder : connection::liveness {
template <typename Callable>
connection_holder(Callable&& callback) : m_callback{std::forward<Callable>(callback)}
{
}
connection m_connection{connection::enabled_tag};
function_type m_callback;
const function_type m_callback;
};
mutable Mutex m_mutex;
/* Store connection_holders as shared_ptrs to avoid having to copy them by
* value in operator().
*/
std::vector<std::shared_ptr<connection_holder>> m_connections GUARDED_BY(m_mutex){};
public:
@@ -208,14 +209,14 @@ public:
}
if constexpr (std::is_void_v<result_type>) {
for (const auto& connection : connections) {
if (connection->m_connection.connected()) {
if (connection->connected()) {
connection->m_callback(args...);
}
}
} else {
result_type ret{std::nullopt};
for (const auto& connection : connections) {
if (connection->m_connection.connected()) {
if (connection->connected()) {
ret.emplace(connection->m_callback(args...));
}
}
@@ -233,10 +234,10 @@ public:
LOCK(m_mutex);
// Garbage-collect disconnected connections to prevent unbounded growth
std::erase_if(m_connections, [](const auto& holder) { return !holder->m_connection.connected(); });
std::erase_if(m_connections, [](const auto& holder) { return !holder->connected(); });
const auto& connection = m_connections.emplace_back(std::make_shared<connection_holder>(std::forward<Callable>(func)));
return connection->m_connection;
const auto& entry = m_connections.emplace_back(std::make_shared<connection_holder>(std::forward<Callable>(func)));
return connection(entry);
}
/*
@@ -246,7 +247,7 @@ public:
{
LOCK(m_mutex);
return std::ranges::none_of(m_connections, [](const auto& holder) {
return holder->m_connection.connected();
return holder->connected();
});
}
};