General Purpose library for Freestanding C++ and POSIX systems
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#pragma once
#include "gp/algorithm/foreach.hpp"
#include "gp/algorithm/reference.hpp"
#include "gp/allocator/allocator.hpp"
#include "gp/vector.hpp"
#include "gp/vfs/file_description.hpp"
#include "gp/vfs/filesystem.hpp"
#include "gp/vfs/runqueue.hpp"
#include "gp/vfs/scheduler.hpp"
namespace gp{
// TODO: thread safety
class scheduling_scheme {
public:
virtual topic_list::node_ptr one(size_t token) = 0;
virtual topic_list::node_ptr next(size_t token, topic_list::node_ptr current) = 0;
virtual void push(topic_list::node_ptr current) = 0;
virtual void link(class system&) = 0;
virtual scheduler& current_scheduler() = 0;
};
class system {
friend struct scheduler;
public:
gp::reference_wrapper<gp::allocator> system_allocator;
gp::vector<gp::filesystem*> filesystems{system_allocator};
gp::vector<gp::scheduler> process_managers;
scheduling_scheme& scheme;
topic_list::node main_context;
system(allocator& v, scheduling_scheme& scheme_, gp::buffer<char> stack_estimate = gp::buffer<char>{nullptr, nullptr})
: system_allocator{v}
, process_managers{system_allocator}
, scheme{scheme_}
{
[[maybe_unused]] volatile char a;
if(stack_estimate.size() == 0) {
auto seed = (char*)&a;
auto jump = (uintptr_t)seed % gp_config::limits::process_stack;
seed -= jump + (jump == 0)*gp_config::limits::process_stack;
auto page_cnt = 1;
if(jump == 0) page_cnt++;
stack_estimate = gp::buffer<char>{seed, (size_t)(gp_config::limits::process_stack*page_cnt)};
}
main_context.value = (process_data*)system_allocator.get().allocate(sizeof(process_data));
new(main_context.value) process_data(gp::function<void()>([]() -> void{}, nullopt), stack_estimate.begin().data, stack_estimate.size());
gp_config::assertion(main_context.value != nullptr, "failed to allocate return to main switch");
scheme.link(*this);
}
size_t spawn(gp::function<void()> fn) {
constexpr size_t stack_sz = gp_config::limits::process_stack;
void* stack = system_allocator.get().allocate(stack_sz);
gp_config::assertion(stack != nullptr, "failed to allocate a stack");
process_data* created_process = (process_data*)system_allocator.get().allocate(sizeof(process_data));
gp_config::assertion(stack != nullptr, "failed to allocate a process data");
new(created_process) process_data(fn, stack, stack_sz);
topic_list::node_ptr pp = (topic_list::node_ptr)system_allocator.get().allocate(
sizeof(topic_list::node)
);
new(pp) topic_list::node();
pp->value = created_process;
auto pid = pp->value->pid;
scheme.push(pp);
return pid;
}
template<typename threading_function>
void run(threading_function thread_starter) {
for(auto& i : process_managers) {
gp::function<void(void)> runner{
[&](){
i.run();
},
system_allocator
};
thread_starter(
runner
);
}
}
void yield() {
scheme.current_scheduler().yield();
}
};
scheduler::scheduler(class system& v, size_t token)
: id(token)
, sys(v)
, main_context_data{gp::function<void()>{[](){}, v.system_allocator}, nullptr, size_t(0)}
, main_context()
{
main_context.value = &main_context_data;
gp_config::assertion(!main_context.try_acquire(), "node should be not aquired on creation");
}
no_inline_decl(inline scheduler* spawner (scheduler* new_p)) {
auto& proc = *new_p->current->value;
if(proc.state == gp::process_status::inactive) {
proc.state = gp::process_status::running;
proc.fn();
proc.state = gp::process_status::finished;
}
return new_p;
}
void scheduler::yield_to(topic_list::node_ptr target)
{
previous = current;
current->value->specifics.pull();
current = target;
auto new_p = this;
do{
new_p = spawner(static_cast<scheduler*>(target->value->specifics.push(new_p)));
target = new_p->sys.scheme.next(new_p->id, new_p->current);
new_p->previous = new_p->current;
new_p->current->value->specifics.pull();
new_p->current = target;
} while(true);
}
void scheduler::yield(){
current = sys.scheme.next(id, current);
yield_to(current);
}
void scheduler::run()
{
main_context_data.pid = 0;
main_context_data.state = process_status::running;
main_context_data.specifics.pull();
current = &main_context;
sys.scheme.push(&main_context);
auto new_p = spawner(static_cast<scheduler*>(current->value->specifics.push(this)));
new_p->yield_to(new_p->sys.scheme.next(new_p->id, new_p->current));
}
}