initial wasm support

src/common/fiber.cpp

@@ -11,7 +11,12 @@
 #include "common/fiber.h"
 #include "common/virtual_buffer.h"
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#include <emscripten/fiber.h>
+#else
 #include <boost/context/detail/fcontext.hpp>
+#endif
 
 namespace Common {
 
@@ -22,36 +27,103 @@ constexpr size_t DEFAULT_STACK_SIZE = 512 * 4096;
 #endif
 constexpr u32 CANARY_VALUE = 0xDEADBEEF;
 
+#ifdef __EMSCRIPTEN__
 struct Fiber::FiberImpl {
     FiberImpl() {}
 
     u32 canary_1 = CANARY_VALUE;
     std::array<u8, DEFAULT_STACK_SIZE> stack{};
-    std::array<u8, DEFAULT_STACK_SIZE> rewind_stack{};
+    std::array<u8, DEFAULT_STACK_SIZE> astack{};
     u32 canary_2 = CANARY_VALUE;
 
-    boost::context::detail::fcontext_t context{};
-    boost::context::detail::fcontext_t rewind_context{};
+    emscripten_fiber_t* context{nullptr};
 
     std::mutex guard;
     std::function<void()> entry_point;
-    std::function<void()> rewind_point;
     std::shared_ptr<Fiber> previous_fiber;
-
-    u8* stack_limit = nullptr;
-    u8* rewind_stack_limit = nullptr;
     bool is_thread_fiber = false;
     bool released = false;
 };
 
-void Fiber::SetRewindPoint(std::function<void()>&& rewind_func) {
-    impl->rewind_point = std::move(rewind_func);
+Fiber::Fiber(std::function<void()>&& entry_point_func) : impl{std::make_unique<FiberImpl>()} {
+    impl->entry_point = std::move(entry_point_func);
+    emscripten_fiber_init(impl->context, [](void *user_data) -> void {
+        auto* fiber = static_cast<Fiber*>(user_data);
+        ASSERT(fiber && fiber->impl && fiber->impl->previous_fiber && fiber->impl->previous_fiber->impl);
+        ASSERT(fiber->impl->canary_1 == CANARY_VALUE);
+        ASSERT(fiber->impl->canary_2 == CANARY_VALUE);
+        fiber->impl->previous_fiber->impl->context = fiber->impl->context;
+        fiber->impl->previous_fiber->impl->guard.unlock();
+        fiber->impl->previous_fiber.reset();
+        fiber->impl->entry_point();
+        UNREACHABLE();
+    }, impl.get(), impl->stack.data(), impl->stack.size(), impl->astack.data(), impl->astack.size());
 }
 
+Fiber::Fiber() : impl{std::make_unique<FiberImpl>()} {}
+
+Fiber::~Fiber() {
+    if (!impl->released) {
+        // Make sure the Fiber is not being used
+        const bool locked = impl->guard.try_lock();
+        ASSERT(locked && "Destroying a fiber that's still running");
+        if (locked) {
+            impl->guard.unlock();
+        }
+    }
+}
+
+void Fiber::Exit() {
+    ASSERT(impl->is_thread_fiber && "Exiting non main thread fiber");
+    if (impl->is_thread_fiber) {
+        impl->guard.unlock();
+        impl->released = true;
+    }
+}
+
+void Fiber::YieldTo(std::weak_ptr<Fiber> weak_from, Fiber& to) {
+    to.impl->guard.lock();
+    to.impl->previous_fiber = weak_from.lock();
+    emscripten_fiber_swap(to.impl->context, to.impl->previous_fiber->impl->context);
+    // "from" might no longer be valid if the thread was killed
+    if (auto from = weak_from.lock()) {
+        if (from->impl->previous_fiber == nullptr) {
+            ASSERT(false && "previous_fiber is nullptr!");
+        } else {
+            from->impl->previous_fiber->impl->guard.unlock();
+            from->impl->previous_fiber.reset();
+        }
+    }
+}
+
+std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
+    std::shared_ptr<Fiber> fiber = std::shared_ptr<Fiber>{new Fiber()};
+    fiber->impl->guard.lock();
+    fiber->impl->is_thread_fiber = true;
+    return fiber;
+}
+#else
+struct Fiber::FiberImpl {
+    FiberImpl() {}
+
+    u32 canary_1 = CANARY_VALUE;
+    std::array<u8, DEFAULT_STACK_SIZE> stack{};
+    u32 canary_2 = CANARY_VALUE;
+
+    boost::context::detail::fcontext_t context{};
+
+    std::mutex guard;
+    std::function<void()> entry_point;
+    std::shared_ptr<Fiber> previous_fiber;
+
+    u8* stack_limit = nullptr;
+    bool is_thread_fiber = false;
+    bool released = false;
+};
+
 Fiber::Fiber(std::function<void()>&& entry_point_func) : impl{std::make_unique<FiberImpl>()} {
     impl->entry_point = std::move(entry_point_func);
     impl->stack_limit = impl->stack.data();
-    impl->rewind_stack_limit = impl->rewind_stack.data();
     u8* stack_base = impl->stack_limit + DEFAULT_STACK_SIZE;
     impl->context = boost::context::detail::make_fcontext(stack_base, impl->stack.size(), [](boost::context::detail::transfer_t transfer) -> void {
         auto* fiber = static_cast<Fiber*>(transfer.data);
@@ -72,7 +144,7 @@ Fiber::~Fiber() {
     if (!impl->released) {
         // Make sure the Fiber is not being used
         const bool locked = impl->guard.try_lock();
-        ASSERT_MSG(locked, "Destroying a fiber that's still running");
+        ASSERT(locked && "Destroying a fiber that's still running");
         if (locked) {
             impl->guard.unlock();
         }
@@ -80,7 +152,7 @@ Fiber::~Fiber() {
 }
 
 void Fiber::Exit() {
-    ASSERT_MSG(impl->is_thread_fiber, "Exiting non main thread fiber");
+    ASSERT(impl->is_thread_fiber && "Exiting non main thread fiber");
     if (impl->is_thread_fiber) {
         impl->guard.unlock();
         impl->released = true;
@@ -110,5 +182,6 @@ std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
     fiber->impl->is_thread_fiber = true;
     return fiber;
 }
+#endif
 
 } // namespace Common