Compiler: Add support for substacks

Author: adazem009

src/engine/compiler.cpp

@@ -24,11 +24,21 @@ void Compiler::compile()
 
     m_block = m_block->next();
     while (m_block) {
+        size_t substacks = m_substackTree.size();
+
         if (m_block->compileFunction())
             m_block->compile(this);
         else
             std::cout << "warning: unsupported block: " << m_block->opcode() << std::endl;
-        m_block = m_block->next();
+
+        if (substacks != m_substackTree.size())
+            continue;
+
+        if (m_block)
+            m_block = m_block->next();
+
+        if (!m_block && !m_substackTree.empty())
+            substackEnd();
     }
 
     // Add end instruction (halt)
@@ -107,6 +117,10 @@ void Compiler::addInstruction(Opcode opcode, std::initializer_list<unsigned int>
 void Compiler::addInput(int id)
 {
     auto in = input(id);
+    if (!in) {
+        addInstruction(OP_NULL);
+        return;
+    }
     switch (in->type()) {
         case Input::Type::Shadow:
             addInstruction(OP_CONST, { constIndex(in->primaryValue()) });
@@ -128,6 +142,21 @@ void Compiler::addFunctionCall(BlockFunc f)
     addInstruction(OP_EXEC, { m_engine->functionIndex(f) });
 }
 
+/*! Jumps to the given substack. The second substack is used for example for the if/else block. */
+void Compiler::moveToSubstack(std::shared_ptr<Block> substack1, std::shared_ptr<Block> substack2, SubstackType type)
+{
+    m_substackTree.push_back({ { m_block, substack2 }, type });
+    m_block = substack1;
+    if (!m_block)
+        substackEnd();
+}
+
+/*! Jumps to the given substack. */
+void Compiler::moveToSubstack(std::shared_ptr<Block> substack, SubstackType type)
+{
+    moveToSubstack(substack, nullptr, type);
+}
+
 /*! Returns the input with the given ID. */
 Input *Compiler::input(int id) const
 {
@@ -140,6 +169,13 @@ Field *Compiler::field(int id) const
     return m_block->findFieldById(id);
 }
 
+/*! Returns the block in the given input. Same as input(id)->valueBlock(), but with a null pointer check. */
+std::shared_ptr<Block> Compiler::inputBlock(int id) const
+{
+    auto in = input(id);
+    return in ? in->valueBlock() : nullptr;
+}
+
 /*! Returns the index of the given variable. */
 unsigned int Compiler::variableIndex(std::shared_ptr<IEntity> varEntity)
 {
@@ -170,3 +206,26 @@ unsigned int Compiler::constIndex(InputValue *value)
     m_constValues.push_back(value);
     return m_constValues.size() - 1;
 }
+
+void Compiler::substackEnd()
+{
+    auto parent = m_substackTree.back();
+    switch (parent.second) {
+        case SubstackType::Loop:
+            addInstruction(OP_LOOP_END);
+            break;
+        case SubstackType::IfStatement:
+            if (parent.first.second) {
+                addInstruction(OP_ELSE);
+                m_block = parent.first.second;
+                m_substackTree[m_substackTree.size() - 1].first.second = nullptr;
+                return;
+            } else
+                addInstruction(OP_ENDIF);
+            break;
+    }
+    m_block = parent.first.first->next();
+    m_substackTree.pop_back();
+    if (!m_block && !m_substackTree.empty())
+        substackEnd();
+}

src/engine/compiler.h

@@ -12,6 +12,12 @@ namespace libscratchcpp
 class LIBSCRATCHCPP_EXPORT Compiler
 {
     public:
+        enum class SubstackType
+        {
+            Loop,
+            IfStatement
+        };
+
         Compiler(Engine *engine, std::shared_ptr<Block> topLevelBlock);
         Compiler(const Compiler &) = delete;
 
@@ -33,17 +39,22 @@ class LIBSCRATCHCPP_EXPORT Compiler
         void addInstruction(vm::Opcode opcode, std::initializer_list<unsigned int> args = {});
         void addInput(int id);
         void addFunctionCall(BlockFunc f);
+        void moveToSubstack(std::shared_ptr<Block> substack1, std::shared_ptr<Block> substack2, SubstackType type);
+        void moveToSubstack(std::shared_ptr<Block> substack, SubstackType type);
 
         Input *input(int id) const;
         Field *field(int id) const;
+        std::shared_ptr<Block> inputBlock(int id) const;
         unsigned int variableIndex(std::shared_ptr<IEntity> varEntity);
         unsigned int listIndex(std::shared_ptr<IEntity> listEntity);
 
     private:
         unsigned int constIndex(InputValue *value);
+        void substackEnd();
 
         Engine *m_engine;
         std::shared_ptr<Block>(m_block);
+        std::vector<std::pair<std::pair<std::shared_ptr<Block>, std::shared_ptr<Block>>, SubstackType>> m_substackTree;
 
         std::vector<unsigned int> m_bytecode;
         std::vector<InputValue *> m_constValues;