bytecode_reader.c

//
// Created by zhoubing on 2017/6/12.
//

#include <memory.h>
#include <stdlib.h>
#include "bytecode_reader.h"

uint8_t vm_read_8bit (struct vm_bytecode_reader *reader)
{
  uint8_t val = 0;
  memcpy(&val, reader->buf + reader->index, sizeof (uint8_t));
  //reader->buf += sizeof(uint8_t);
  val &= 0xff;
  reader->index += sizeof (uint8_t);
  return val;
}

uint16_t vm_read_16bit (struct vm_bytecode_reader *reader)
{
  uint16_t val = 0;
  uint8_t high = vm_read_8bit (reader);
  uint8_t low = vm_read_8bit (reader);
  val |= low;
  val |= high << 8;
  val &= 0xffff;
  return val;
}

uint32_t vm_read_32bit (struct vm_bytecode_reader *reader)
{
  uint32_t val = 0;
  uint16_t high = vm_read_16bit (reader);
  uint16_t low = vm_read_16bit (reader);
  val |= low;
  val |= high << 16;
  val &= 0xffffffff;
  return val;
}

uint8_t *vm_read_bytes (struct vm_bytecode_reader *reader, int bytes)
{
  size_t len = bytes * sizeof (uint8_t);
  uint8_t *str = (uint8_t *) malloc (len);
  //指针指向原数据还是重新分配内存拷贝出来？
  memcpy(str, reader->buf + reader->index, len);
  reader->index += len;
  return str;
}

struct vm_bytecode_reader *new_bytecode_reader (char *bytecode, uint32_t len)
{
  struct vm_bytecode_reader *reader = malloc (sizeof (struct vm_bytecode_reader));
  memset (reader, 0x00, sizeof (struct vm_bytecode_reader));
  reader->buf = bytecode;
  reader->size = len;
  reader->index = 0;
  return reader;
}