From 137d862d9b275209b3d62a413396a15e9e14b4b4 Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow <fsahmkow27@gmail.com>
Date: Thu, 27 Feb 2020 16:32:47 -0400
Subject: Common/Fiber: Implement Rewinding.

---
 src/common/fiber.cpp | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

(limited to 'src/common/fiber.cpp')

diff --git a/src/common/fiber.cpp b/src/common/fiber.cpp
index e4ecc73df..f61479e13 100644
--- a/src/common/fiber.cpp
+++ b/src/common/fiber.cpp
@@ -12,10 +12,13 @@
 
 namespace Common {
 
+constexpr std::size_t default_stack_size = 256 * 1024; // 256kb
+
 #if defined(_WIN32) || defined(WIN32)
 
 struct Fiber::FiberImpl {
     LPVOID handle = nullptr;
+    LPVOID rewind_handle = nullptr;
 };
 
 void Fiber::start() {
@@ -26,15 +29,29 @@ void Fiber::start() {
     UNREACHABLE();
 }
 
+void Fiber::onRewind() {
+    ASSERT(impl->handle != nullptr);
+    DeleteFiber(impl->handle);
+    impl->handle = impl->rewind_handle;
+    impl->rewind_handle = nullptr;
+    rewind_point(rewind_parameter);
+    UNREACHABLE();
+}
+
 void __stdcall Fiber::FiberStartFunc(void* fiber_parameter) {
     auto fiber = static_cast<Fiber*>(fiber_parameter);
     fiber->start();
 }
 
+void __stdcall Fiber::RewindStartFunc(void* fiber_parameter) {
+    auto fiber = static_cast<Fiber*>(fiber_parameter);
+    fiber->onRewind();
+}
+
 Fiber::Fiber(std::function<void(void*)>&& entry_point_func, void* start_parameter)
     : entry_point{std::move(entry_point_func)}, start_parameter{start_parameter} {
     impl = std::make_unique<FiberImpl>();
-    impl->handle = CreateFiber(0, &FiberStartFunc, this);
+    impl->handle = CreateFiber(default_stack_size, &FiberStartFunc, this);
 }
 
 Fiber::Fiber() {
@@ -60,6 +77,18 @@ void Fiber::Exit() {
     guard.unlock();
 }
 
+void Fiber::SetRewindPoint(std::function<void(void*)>&& rewind_func, void* start_parameter) {
+    rewind_point = std::move(rewind_func);
+    rewind_parameter = start_parameter;
+}
+
+void Fiber::Rewind() {
+    ASSERT(rewind_point);
+    ASSERT(impl->rewind_handle == nullptr);
+    impl->rewind_handle = CreateFiber(default_stack_size, &RewindStartFunc, this);
+    SwitchToFiber(impl->rewind_handle);
+}
+
 void Fiber::YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to) {
     ASSERT_MSG(from != nullptr, "Yielding fiber is null!");
     ASSERT_MSG(to != nullptr, "Next fiber is null!");
@@ -81,7 +110,6 @@ std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
 }
 
 #else
-constexpr std::size_t default_stack_size = 1024 * 1024; // 1MB
 
 struct Fiber::FiberImpl {
     alignas(64) std::array<u8, default_stack_size> stack;
-- 
cgit v1.2.3