initial implementation

This commit is contained in:
Roland Conybeare 2023-10-10 12:32:34 -04:00
commit 487f516a3f
5 changed files with 402 additions and 0 deletions

48
CMakeLists.txt Normal file
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# callback/CMakeLists.txt
cmake_minimum_required(VERSION 3.10)
project(callback VERSION 0.1)
enable_language(CXX)
# common XO cmake macros (see proj/xo-cmake)
include(xo_macros/xo_cxx)
include(xo_macros/code-coverage)
# ----------------------------------------------------------------
# unit test setup
enable_testing()
# activate code coverage for all executables + libraries (when configured with -DCODE_COVERAGE=ON)
add_code_coverage()
# 1. assuming that /nix/store/ prefixes .hpp files belonging to gcc, catch2 etc.
# we're not interested in code coverage for these sources.
# 2. exclude the utest/ subdir, we don't need coverage on the unit tests themselves;
# rather, want coverage on the code that the unit tests exercise.
#
# NOTE: this seems to work only with the 'ccov-all' target. In particular, doesn't seem to do anything with the 'ccov' target
#
add_code_coverage_all_targets(EXCLUDE /nix/store/* ${PROJECT_SOURCE_DIR}/utest/* ${PROJECT_BINARY_DIR}/local/* ${PROJECT_SOURCE_DIR}/repo/*)
# ----------------------------------------------------------------
# c++ settings
# PROJECT_CXX_FLAGS: bespoke for this project - usually empty
set(PROJECT_CXX_FLAGS "")
#set(PROJECT_CXX_FLAGS "-fconcepts-diagnostics-depth=2")
add_definitions(${PROJECT_CXX_FLAGS})
xo_toplevel_compile_options()
# ----------------------------------------------------------------
# sources
add_subdirectory(src/callback)
#add_subdirectory(utest)
# ----------------------------------------------------------------
# provide find_package() support to customers
xo_export_cmake_config(${PROJECT_NAME} ${PROJECT_VERSION} ${PROJECT_NAME}Targets)
# end CMakeLists.txt

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@PACKAGE_INIT@
include(CMakeFindDependencyMacro)
find_dependency(refcnt)
include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")
check_required_components("@PROJECT_NAME@")

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/* @file CallbackSet.hpp */
#pragma once
#include "xo/refcnt/Refcounted.hpp"
//#include "indentlog/scope.hpp"
//#include "indentlog/print/tag.hpp"
#include <functional>
#include <vector>
namespace xo {
namespace fn {
/* identifies a particular callback in a CallbackSet (see below).
* an unique id is created:
* CallbackSetImpl cbset = ...;
* CallbackId cb_id = cbset.add_callback(..);
*
* can use id to remove callback later:
* cbset.remove_callback(cb_id);
*/
class CallbackId {
public:
CallbackId() = default;
explicit CallbackId(uint32_t id) : id_{id} {}
/* generate a globally-unique id (not threadsafe) */
static CallbackId generate();
uint32_t id() const { return id_; }
private:
uint32_t id_ = 0;
}; /*CallbackId*/
inline bool operator==(CallbackId lhs, CallbackId rhs) { return lhs.id() == rhs.id(); }
inline bool operator!=(CallbackId lhs, CallbackId rhs) { return lhs.id() != rhs.id(); }
/* queue add/remove callback instructions encountered during callback
* execution, to avoid invalidating vector iterator.
*
*/
template<typename Fn>
struct ReentrantCbsetCmd {
enum CbsetCmdEnum { AddCallback, RemoveCallback };
ReentrantCbsetCmd() = default;
ReentrantCbsetCmd(CbsetCmdEnum cmd, CallbackId id, Fn const & fn)
: cmd_{cmd}, id_{id}, fn_{fn} {}
static ReentrantCbsetCmd add(CallbackId id, Fn const & fn) {
return ReentrantCbsetCmd{AddCallback, id, fn};
} /*add*/
static ReentrantCbsetCmd remove(CallbackId id) {
return ReentrantCbsetCmd{RemoveCallback, id, Fn()};
} /*remove*/
bool is_add() const { return cmd_ == AddCallback; }
bool is_remove() const { return cmd_ == RemoveCallback; }
CallbackId id() const { return id_; }
Fn const & fn() const { return fn_; }
private:
/* AddCallback: deferred CallbackSet<Fn>::add_callback(.fn)
* RemoveCallback: deferred CallbackSet<Fn>::remove_callback(.fn)
*/
CbsetCmdEnum cmd_ = AddCallback;
CallbackId id_;
Fn fn_;
}; /*ReentrantCbsetCmd*/
/* record for remembering a single callback.
* callbacks are given unique ids so they can be removed later
*/
template<typename Fn>
struct CbRecd {
CbRecd(CallbackId id, Fn const & fn) : id_{id}, fn_{fn} {}
CallbackId id_;
Fn fn_;
}; /*CbRecd*/
/* If Fnptr is a type such that this works:
* Fnptr fn = ...;
* using Fn = Fnptr::destination_type;
* Fn * native_fn = fn.get();
* (native_fn->*member_fn)(args ...);
*
* then
* CallbackSet<Fnptr> cbset = ...;
* cbset.invoke(&Fn::member_fn, args...)
*
* calls
* (cb->*member_fn)(args...)
*
* for each callback cb in this set.
*
* In addition, calls hook methods:
* cb->notify_add_callback()
* cb->notify_remove_callback()
* when adding/removing callback.
*
* Require:
* - can invoke (Fnptr->*member_fn)(...)
*
* implementation is reentrant: running callbacks can safely make
* add/remove calls on the cbset that invoked them.
*
* not threadsafe.
*/
template<typename Fn>
class CallbackSetImpl {
public:
using callback_type = typename Fn::element_type;
//using scope = xo::scope;
public:
CallbackSetImpl() = default;
/* support for range iterators */
typename std::vector<CbRecd<Fn>>::const_iterator begin() const { return cb_v_.begin(); }
typename std::vector<CbRecd<Fn>>::const_iterator end() const { return cb_v_.end(); }
/* invoke callbacks registered with this callback set */
template<typename ... Tn, typename ... Sn>
void invoke(void (callback_type::* member_fn)(Sn... args), Tn&&... args) {
this->cb_running_ = true;
try {
for(CbRecd<Fn> const & cb_recd : this->cb_v_) {
callback_type * native_cb = cb_recd.fn_.get();
/* clang11 doesn't like
* cb->*member_fn
* when cb-> is overloaded
*/
(native_cb->*member_fn)(args...);
}
this->make_deferred_changes();
} catch(...) {
this->make_deferred_changes();
throw;
}
} /*operator()*/
/* call fn(cb) for each callback present in this set */
void visit_callbacks(std::function<void (Fn const &)> fn) const {
CallbackSetImpl * self = const_cast<CallbackSetImpl *>(this);
self->cb_running_ = true;
try {
for(Fn const & cb : this->cb_v_)
fn(cb);
this->make_deferred_changes();
} catch(...) {
this->make_deferred_changes();
throw;
}
} /*visit_callbacks*/
/* add callback target_fn to this callback set.
* reentrant
*/
CallbackId add_callback(Fn const & target_fn) {
CallbackId id = CallbackId::generate();
if(this->cb_running_) {
/* defer until callback execution completes */
this->reentrant_cmd_v_.push_back(ReentrantCbsetCmd<Fn>::add(id, target_fn));
} else {
#ifdef NOT_USING
constexpr bool c_debug_enabled_flag = false;
scope lscope(reflect::type_name<CallbackSetImpl>(),
"::add_callback", c_debug_enabled_flag);
if (c_debug_enabled_flag) {
lscope.log("before appending .cb_v[]",
xo::xtag("target_fn", (void*)target_fn.get()),
xo::xtag("target_fn.refcnt",
target_fn->reference_counter()));
}
#endif
this->cb_v_.push_back(CbRecd(id, target_fn));
#ifdef NOT_USING
if (c_debug_enabled_flag) {
lscope.log("after appending .cb_v[]",
xo::xtag("target_fn", (void *)target_fn.get()),
xo::xtag("target_fn.refcnt",
target_fn->reference_counter()));
}
#endif
}
return id;
} /*add_callback*/
void remove_callback(CallbackId id) {
if(this->cb_running_) {
/* defer until callback execution completes */
this->reentrant_cmd_v_.push_back(ReentrantCbsetCmd<Fn>::remove(id));
} else {
this->remove_callback_impl(id);
}
} /*remove_callback*/
#ifdef NOT_USING
/* remove callback target_fn from this callback set.
* noop if callback is not present
*/
void remove_callback(Fn const & target_fn) {
if(this->cb_running_) {
/* defer until callback execution completes */
this->reentrant_cmd_v_.push_back(ReentrantCbsetCmd<Fn>::remove(target_fn));
} else {
this->remove_callback_impl(target_fn);
}
} /*remove_callback*/
#endif
private:
/* apply deferred changes to .cb_v[] */
void make_deferred_changes() {
this->cb_running_ = false;
std::vector<ReentrantCbsetCmd<Fn>> cmd_v;
std::swap(cmd_v, this->reentrant_cmd_v_);
for(ReentrantCbsetCmd<Fn> const & cmd : cmd_v) {
if(cmd.is_add()) {
this->cb_v_.push_back(CbRecd(cmd.id(), cmd.fn()));
cmd.fn()->notify_add_callback();
} else if(cmd.is_remove()) {
this->remove_callback_impl(cmd.id());
}
}
} /*make_deferred_changes*/
void remove_callback_impl(CallbackId target_id) {
for (auto ix = this->cb_v_.begin(); ix != this->cb_v_.end(); ++ix) {
if (ix->id_ == target_id) {
Fn target_fn = ix->fn_;
this->cb_v_.erase(ix);
target_fn->notify_remove_callback();
break;
}
}
} /*remove_callback_impl*/
#ifdef NOT_USING
void remove_callback_impl(Fn const & target_fn) {
auto ix = std::find(this->cb_v_.begin(), this->cb_v_.end(), target_fn);
if(ix != this->cb_v_.end())
this->cb_v_.erase(ix);
target_fn->notify_remove_callback();
} /*remove_callback_impl*/
#endif
private:
bool cb_running_ = false;
/* collection of callback functions */
std::vector<CbRecd<Fn>> cb_v_;
/* when a callback registered with *this, while running,
* attempts to add/remove a callback to/from this set
* (including removing itself),
* must defer until all callbacks have executed.
* remember deferred instructions here.
*/
std::vector<ReentrantCbsetCmd<Fn>> reentrant_cmd_v_;
}; /*CallbackSetImpl*/
template<typename NativeFn>
using RpCallbackSet = CallbackSetImpl<xo::ref::rp<NativeFn>>;
/* like RpCallbackSet<NativeFn>,
* but also provides overload(s) for operator()(..)
*/
template<typename NativeFn, typename MemberFn>
class NotifyCallbackSet : public RpCallbackSet<NativeFn> {
public:
NotifyCallbackSet(MemberFn fn)
: privileged_member_fn_{fn} {}
template<typename ... Tn>
void operator()(Tn&&... args) {
this->invoke(this->privileged_member_fn_, args...);
} /*operator()*/
private:
/* implements operator()(...) */
MemberFn privileged_member_fn_;
}; /*NotifyCallbackSet*/
template<typename NativeFn, typename Sret, typename ... Sn>
inline NotifyCallbackSet<NativeFn, Sret (NativeFn::*)(Sn...)>
make_notify_cbset(Sret (NativeFn::* member_fn)(Sn...)) {
return NotifyCallbackSet<NativeFn, Sret (NativeFn::*)(Sn...)>(member_fn);
} /*make_notify_cbset*/
} /*namespace fn*/
} /*namespace xo*/
/* end CallbackSet.hpp */

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# callback/CMakeLists.txt
set(SELF_LIB callback)
set(SELF_SRCS CallbackSet.cpp)
# reminder: can't be header-only library, because depends on non-header-only refcnt
xo_add_shared_library(${SELF_LIB} ${PROJECT_VERSION} 1 ${SELF_SRCS})
# ----------------------------------------------------------------
# external dependencies:
xo_dependency(${SELF_LIB} refcnt)
# end CMakeLists.txt

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/* file CallbackSet.cpp
*
* author: Roland Conybeare, Sep 2022
*/
#include "CallbackSet.hpp"
namespace xo {
namespace fn {
CallbackId
CallbackId::generate()
{
static CallbackId s_last_id;
s_last_id = CallbackId(s_last_id.id() + 1);
return s_last_id;
} /*generate*/
} /*namespace fn*/
} /*namespace xo*/
/* end CallbackSet.cpp */