fase 4+5: fibers cooperatius substitueixen el game thread, sense mutex ni cv

source/core/system/fiber.cpp

@@ -0,0 +1,141 @@
+#include "core/system/fiber.hpp"
+
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+
+#if defined(_WIN32)
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#else
+// ucontext_t està marcat com a obsolet a POSIX.1-2008 però continua
+// funcional a glibc Linux i macOS. Si en el futur migrem a una alternativa
+// (boost::context, makecontext personalitzat) només cal tocar aquest fitxer.
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+#elif defined(__GNUC__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
+#include <ucontext.h>
+#endif
+
+namespace GameFiber {
+
+namespace {
+
+bool initialized_ = false;
+bool done_ = false;
+EntryFn entry_fn_ = nullptr;
+
+#if defined(_WIN32)
+
+LPVOID main_fiber_ = nullptr;
+LPVOID game_fiber_ = nullptr;
+
+void __stdcall trampoline(void* /*param*/) {
+    if (entry_fn_) entry_fn_();
+    done_ = true;
+    SwitchToFiber(main_fiber_);
+}
+
+#else
+
+ucontext_t main_ctx_{};
+ucontext_t fiber_ctx_{};
+void* fiber_stack_ = nullptr;
+
+void trampoline() {
+    if (entry_fn_) entry_fn_();
+    done_ = true;
+    // Retornar al main: uc_link apunta a main_ctx_ en init().
+}
+
+#endif
+
+}  // namespace
+
+void init(EntryFn entry, std::size_t stack_size) {
+    if (initialized_) destroy();
+    entry_fn_ = entry;
+    done_ = false;
+
+#if defined(_WIN32)
+    main_fiber_ = ConvertThreadToFiber(nullptr);
+    if (!main_fiber_) {
+        // Ja era un fiber (no sol passar en el main thread d'una app SDL).
+        main_fiber_ = GetCurrentFiber();
+    }
+    game_fiber_ = CreateFiber(stack_size, trampoline, nullptr);
+    if (!game_fiber_) {
+        std::cerr << "GameFiber::init: CreateFiber failed\n";
+        return;
+    }
+#else
+    fiber_stack_ = std::malloc(stack_size);
+    if (!fiber_stack_) {
+        std::cerr << "GameFiber::init: malloc failed\n";
+        return;
+    }
+    getcontext(&fiber_ctx_);
+    fiber_ctx_.uc_stack.ss_sp = fiber_stack_;
+    fiber_ctx_.uc_stack.ss_size = stack_size;
+    fiber_ctx_.uc_link = &main_ctx_;
+    makecontext(&fiber_ctx_, trampoline, 0);
+#endif
+
+    initialized_ = true;
+}
+
+void destroy() {
+    if (!initialized_) return;
+#if defined(_WIN32)
+    if (game_fiber_) {
+        DeleteFiber(game_fiber_);
+        game_fiber_ = nullptr;
+    }
+    // No desconvertim el main thread: SDL pot estar-ne pendent i ja no
+    // tornem a crear fibers en aquesta execució. ConvertFiberToThread()
+    // només cal si volguerem reutilitzar el main com a thread normal.
+#else
+    if (fiber_stack_) {
+        std::free(fiber_stack_);
+        fiber_stack_ = nullptr;
+    }
+#endif
+    initialized_ = false;
+    done_ = false;
+    entry_fn_ = nullptr;
+}
+
+void resume() {
+    if (!initialized_ || done_) return;
+#if defined(_WIN32)
+    SwitchToFiber(game_fiber_);
+#else
+    swapcontext(&main_ctx_, &fiber_ctx_);
+#endif
+}
+
+void yield() {
+    if (!initialized_) return;
+#if defined(_WIN32)
+    SwitchToFiber(main_fiber_);
+#else
+    swapcontext(&fiber_ctx_, &main_ctx_);
+#endif
+}
+
+bool is_done() { return done_; }
+bool is_initialized() { return initialized_; }
+
+}  // namespace GameFiber
+
+#if !defined(_WIN32)
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#elif defined(__GNUC__)
+#pragma GCC diagnostic pop
+#endif
+#endif