A Virtual Machine 15

src/clox/vm.d

@@ -0,0 +1,59 @@
+module clox.vm;
+
+import std.stdio;
+
+import clox.chunk;
+import clox.value;
+import clox.dbg;
+import clox.util;
+
+enum stackMax = 256;
+
+struct VM{
+	const(ubyte)* ip;
+	Stack!(Value, stackMax) stack;
+	Chunk* chunk;
+	enum InterpretResult{ Ok, CompileError, RunetimeError }
+	this(int _) @nogc nothrow {
+		stack = typeof(stack)(0);
+	}
+	InterpretResult interpret(Chunk* chunk) @nogc nothrow {
+		this.chunk = chunk;
+		ip = &chunk.code[0];
+		return run();
+	}
+	private InterpretResult run() @nogc nothrow {
+		auto readByte() => *ip++;
+		auto readIns() => cast(OpCode)readByte();
+		auto readConstant() => chunk.constants[readByte()];
+		while(true){
+			debug(traceExec){
+				writeln("          ", stack.live);
+				debug disassembleInstruction(chunk, ip - &chunk.code[0]);
+			}
+			OpCode instruction = readIns();
+			with(OpCode) opSwitch: final switch(instruction){
+				case Constant:
+					Value constant = readConstant();
+					stack.push(constant);
+					break;
+				static foreach(k, op; [ Add: "+", Subtract: "-", Multiply: "*", Divide: "/" ]){
+					case k:
+						Value b = stack.pop();
+						Value a = stack.pop();
+						stack.push(mixin("a", op, "b"));
+						break opSwitch;
+				}
+				case Negate:
+					stack.push(-stack.pop());
+					break;
+				case Return:
+					debug printValue(stack.pop());
+					debug writeln();
+					return InterpretResult.Ok;
+			}
+		}
+		assert(0);
+	}
+}
+