clox/vm.c

/**
  ******************************************************************************
  * @file           : vm.c
  * @author         : simon
  * @brief          : Interpret the bytecode from chunk
  * @attention      : None
  * @date           : 2023/8/17
  ******************************************************************************
  */
#include "vm.h"
#include "common.h"
#include "compiler.h"
#include "debug.h"
#include "memory.h"
#include <stdarg.h>

VM vm;

/// \brief 重置栈
static void resetStack() {
  vm.stackTop = vm.stack;// 指针指向栈底
}

static void runtimeError(const char *format, ...) {
  va_list args;
  va_start(args, format);
  vfprintf(stderr, format, args);
  va_end(args);
  fputs("\n", stderr);

  size_t instruction = vm.ip - vm.chunk->code - 1;
  int line = vm.chunk->lines[instruction];
  fprintf(stderr, "[line %d] in script\n", line);
  resetStack();
}

void initVM() {
  resetStack();
  vm.objects = NULL;
  initTable(&vm.strings);
}

static Value peek(int distance) {
  return vm.stackTop[-1 - distance];
}
static bool isFalse(Value value) {
  // the  nil and false will return true
  return IS_NIL(value) || (IS_BOOL(value) && !AS_BOOL(value));
}
static void concatenate() {
  ObjString *b = AS_STRING(pop());
  ObjString *a = AS_STRING(pop());

  int length = a->length + b->length;
  char *chars = ALLOCATE(char, length + 1);
  memcpy(chars, a->chars, a->length);
  memcpy(chars + a->length, b->chars, b->length);
  chars[length] = '\0';

  ObjString *result = takeString(chars, length);
  push(OBJ_VAL(result));
}
static InterpretResult run() {
//! <macro> reads the byte currently pointed at by ip
//! and then advances the instruction pointer
#define READ_BYTE() (*vm.ip++)
//! reads the next byte from the bytecode
//! treats the resulting number as an index
#define READ_CONSTANT() (vm.chunk->constants.values[READ_BYTE()])
#define BINARY_OP(valueType, op)                      \
  do {                                                \
    if (!IS_NUMBER(peek(0)) || !IS_NUMBER(peek(1))) { \
      runtimeError("Operands must be numbers.");      \
      return INTERPRET_RUNTIME_ERROR;                 \
    }                                                 \
    double b = AS_NUMBER(pop());                      \
    double a = AS_NUMBER(pop());                      \
    push(valueType(a op b));                          \
  } while (false)

  for (;;) {
#ifdef DEBUG_TRACE_EXECUTION
    //! <Stack tracing> start
    printf("------------------------\n|");
    for (Value *slot = vm.stack; slot < vm.stackTop; slot++) {
      printf("[ ");
      printValue(*slot);
      printf(" ]");
    }
    printf("\n------------------------");
    printf("\n");
    //! <Stack tracing> end
    disassembleInstruction(vm.chunk, (int) (vm.ip - vm.chunk->code));
#endif
    switch (READ_BYTE()) {
      case OP_CONSTANT: {
        Value constant = READ_CONSTANT();
        push(constant);
        break;
      }
      case OP_NIL:
        push(NIL_VAL);
        break;
      case OP_TRUE:
        push(BOOL_VAL(true));
        break;
      case OP_FALSE:
        push(BOOL_VAL(false));
        break;
      case OP_ADD: {
        if (IS_STRING(peek(0)) && IS_STRING(peek(1))) {
          // 字串拼接
          concatenate();
        } else if (IS_NUMBER(peek(0)) && IS_NUMBER(peek(1))) {
          double b = AS_NUMBER(pop());
          double a = AS_NUMBER(pop());
          push(NUMBER_VAL(a + b));
        } else {
          runtimeError("Operands must be two numbers or two strings.");
          return INTERPRET_RUNTIME_ERROR;
        }
        break;
      }
      case OP_SUBTRACT:
        BINARY_OP(NUMBER_VAL, -);
        break;
      case OP_MULTIPLY:
        BINARY_OP(NUMBER_VAL, *);
        break;
      case OP_DIVIDE:
        BINARY_OP(NUMBER_VAL, /);
        break;
      case OP_NOT:
        push(BOOL_VAL(isFalse(pop())));
        break;
      case OP_NEGATE:
        if (!IS_NUMBER(peek(0))) {
          runtimeError("Operand must be a number.");
          return INTERPRET_RUNTIME_ERROR;
        }
        push(NUMBER_VAL(-AS_NUMBER(pop())));
        break;
      case OP_EQUAL: {
        Value b = pop();
        Value a = pop();
        push(BOOL_VAL(valuesEqual(a, b)));
        break;
      }
      case OP_GREATER:
        BINARY_OP(BOOL_VAL, >);
        break;
      case OP_LESS:
        BINARY_OP(BOOL_VAL, <);
        break;
      case OP_RETURN: {
        printValue(pop());
        printf("\n");
        return INTERPRET_OK;
      }
    }
  }

#undef READ_BYTE
#undef READ_CONSTANT
#undef BINARY_OP
}

void freeVM() {
  freeTable(&vm.strings);
  freeObjects();
}

InterpretResult interpret(const char *source) {
  Chunk chunk;
  initChunk(&chunk);

  if (!compile(source, &chunk)) {
    freeChunk(&chunk);
    return INTERPRET_COMPILE_ERROR;
  }

  vm.chunk = &chunk;
  vm.ip = vm.chunk->code;

  InterpretResult result = run();

  freeChunk(&chunk);
  return result;
}

void push(Value value) {
  *vm.stackTop = value;
  vm.stackTop++;
}

Value pop() {
  vm.stackTop--;
  //! NOTE： 出栈后，里面的值没有清除
  return *vm.stackTop;
}