From e1f18ffca70d4c8be056322de71d543ba9987a28 Mon Sep 17 00:00:00 2001
From: Sebastiaan Fernandez <fernandezsebastiaan@gmail.com>
Date: Sun, 28 Jan 2024 00:45:13 +0100
Subject: [PATCH] Add simple java.lang.Thread.currentThread native
 implementation

---
 src/Library/java/lang/Thread.cpp | 10 ++++++++++
 src/Library/java/lang/Thread.h   |  3 ++-
 src/VM/JavaStack.h               |  5 +++++
 src/VM/VM.cpp                    |  1 +
 4 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/Library/java/lang/Thread.cpp b/src/Library/java/lang/Thread.cpp
index 8e331cc..e1ca572 100644
--- a/src/Library/java/lang/Thread.cpp
+++ b/src/Library/java/lang/Thread.cpp
@@ -17,5 +17,15 @@
 
 JCALL void lib_java_lang_Thread_registerNatives(NATIVE_ARGS)
 {
+    registerNative("java/lang/Thread/currentThread", "()Ljava/lang/Thread;", lib_java_lang_Thread_currentThread);
+}
+
+JCALL void lib_java_lang_Thread_currentThread(NATIVE_ARGS)
+{
+    // TODO: Maybe check if an object was already created?
+    ClassInfo* threadClass = VM->getClass("java/lang/Thread", thread);
+    const u4 objectReference = heap->createObject(threadClass, VM);
+    StackFrame* returnFrame = thread->getTopFrameNonNative();
+    returnFrame->pushObject(objectReference);
 }
 
diff --git a/src/Library/java/lang/Thread.h b/src/Library/java/lang/Thread.h
index c3db132..31f7e65 100644
--- a/src/Library/java/lang/Thread.h
+++ b/src/Library/java/lang/Thread.h
@@ -2,4 +2,5 @@
 
 #include "Library/NativeDefs.h"
 
-JCALL void lib_java_lang_Thread_registerNatives(NATIVE_ARGS);
\ No newline at end of file
+JCALL void lib_java_lang_Thread_registerNatives(NATIVE_ARGS);
+JCALL void lib_java_lang_Thread_currentThread(NATIVE_ARGS);
\ No newline at end of file
diff --git a/src/VM/JavaStack.h b/src/VM/JavaStack.h
index d855d7b..1e3b84e 100644
--- a/src/VM/JavaStack.h
+++ b/src/VM/JavaStack.h
@@ -79,6 +79,11 @@ struct StackFrame {
         operands.emplace_back(VariableType_FLOAT, std::bit_cast<u4>(value));
     }
 
+    void pushObject(const u4 objectRef)
+    {
+        operands.emplace_back(VariableType_REFERENCE, objectRef);
+    }
+
     [[nodiscard]] Variable peekOperand() const
     {
         return operands.back();
diff --git a/src/VM/VM.cpp b/src/VM/VM.cpp
index a56fb20..423137e 100644
--- a/src/VM/VM.cpp
+++ b/src/VM/VM.cpp
@@ -40,6 +40,7 @@ void VM::start()
     getClass("java/lang/Class", &m_mainThread);
     getClass("java/lang/String", &m_mainThread);
     getClass("java/lang/System", &m_mainThread);
+    getClass("java/lang/Thread", &m_mainThread);
 }
 
 std::vector<Variable> VM::createVariableForDescriptor(const char* descriptor)