From 50473e5ab573d85b1a555874332f6aecdd36f659 Mon Sep 17 00:00:00 2001
From: Tom Willemse <tom@ryuslash.org>
Date: Thu, 22 Jul 2021 01:09:11 -0700
Subject: [PATCH] Chapter 15.1

---
 clox/src/CMakeLists.txt |  2 ++
 clox/src/common.h       |  2 ++
 clox/src/main.c         |  9 +++++++--
 clox/src/vm.c           | 44 +++++++++++++++++++++++++++++++++++++++++
 clox/src/vm.h           | 21 ++++++++++++++++++++
 5 files changed, 76 insertions(+), 2 deletions(-)
 create mode 100644 clox/src/vm.c
 create mode 100644 clox/src/vm.h

diff --git a/clox/src/CMakeLists.txt b/clox/src/CMakeLists.txt
index 6d7e73b..435a82e 100644
--- a/clox/src/CMakeLists.txt
+++ b/clox/src/CMakeLists.txt
@@ -8,4 +8,6 @@ add_executable(Lox
   debug.c
   value.h
   value.c
+  vm.h
+  vm.c
   main.c)
diff --git a/clox/src/common.h b/clox/src/common.h
index c827b76..ddab699 100644
--- a/clox/src/common.h
+++ b/clox/src/common.h
@@ -5,4 +5,6 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#define DEBUG_TRACE_EXECUTION
+
 #endif
diff --git a/clox/src/main.c b/clox/src/main.c
index 9aeb8fd..0f810ba 100644
--- a/clox/src/main.c
+++ b/clox/src/main.c
@@ -1,8 +1,11 @@
-#include "common.h"
 #include "chunk.h"
+#include "common.h"
 #include "debug.h"
+#include "vm.h"
+
+int main(int argc, const char *argv[]) {
+  initVM();
 
-int main(int argc, const char* argv[]) {
   Chunk chunk;
   initChunk(&chunk);
 
@@ -13,6 +16,8 @@ int main(int argc, const char* argv[]) {
   writeChunk(&chunk, OP_RETURN, 123);
 
   disassembleChunk(&chunk, "test chunk");
+  interpret(&chunk);
+  freeVM();
   freeChunk(&chunk);
   return 0;
 }
diff --git a/clox/src/vm.c b/clox/src/vm.c
new file mode 100644
index 0000000..14a206e
--- /dev/null
+++ b/clox/src/vm.c
@@ -0,0 +1,44 @@
+#include <stdio.h>
+
+#include "common.h"
+#include "debug.h"
+#include "vm.h"
+
+VM vm;
+
+void initVM() {}
+
+void freeVM() {}
+
+static InterpretResult run() {
+#define READ_BYTE() (*vm.ip++)
+#define READ_CONSTANT() (vm.chunk->constants.values[READ_BYTE()])
+
+  for (;;) {
+#ifdef DEBUG_TRACE_EXECUTION
+    disassembleInstruction(vm.chunk, (int)(vm.ip - vm.chunk->code));
+#endif
+
+    uint8_t instruction;
+    switch (instruction = READ_BYTE()) {
+    case OP_CONSTANT: {
+      Value constant = READ_CONSTANT();
+      printValue(constant);
+      printf("\n");
+      break;
+    }
+    case OP_RETURN: {
+      return INTERPRET_OK;
+    }
+    }
+  }
+
+#undef READ_BYTE
+#undef READ_CONSTANT
+}
+
+InterpretResult interpret(Chunk *chunk) {
+  vm.chunk = chunk;
+  vm.ip = vm.chunk->code;
+  return run();
+}
diff --git a/clox/src/vm.h b/clox/src/vm.h
new file mode 100644
index 0000000..d11ae70
--- /dev/null
+++ b/clox/src/vm.h
@@ -0,0 +1,21 @@
+#ifndef clox_vm_h
+#define clox_vm_h
+
+#include "chunk.h"
+
+typedef struct {
+  Chunk *chunk;
+  uint8_t *ip;
+} VM;
+
+typedef enum {
+  INTERPRET_OK,
+  INTERPRET_COMPILE_ERROR,
+  INTERPRET_RUNTIME_ERROR
+} InterpretResult;
+
+void initVM();
+void freeVM();
+InterpretResult interpret(Chunk *chunk);
+
+#endif