模拟实现atoi函数

#include<stdio.h>
#include<ctype.h>
#include<limits.h>
enum Statue
{
  normal,
  abnormal
 
};
Statue statue = abnormal;
int my_auti(const char* str)
{
  int flag = 0;
  if (*str == NULL || *str == '\0')
  {
    return 0;
  }
  while (isspace(*str))
  {
    str++;//对空格进行跳跃
  }
  if (*str == '-')
  {
    flag = -1;
    str++;
 
  }
  else if (*str == '+')
  {
    flag = 1;
    str++;
  }
  else
  {
    flag = 1;
  }
  
  long long sum = 0;
  while (isdigit(*str))
  {
  
    sum = (*str-'0') * flag + sum * 10;
    if (sum<INT_MIN || sum>INT_MAX)
    {
      return 0;
    }
    str++;
  }
  if (*str == '\0')
  {
    statue = normal;
    return sum;
  }
  else
  {
    return sum;
  }
}
int main()
{
  char str[30] = "  -499";
  int ret = my_auti(str);
  if (statue == normal)
  {
    printf("正常转换：%d\n", ret);
  }
  else
  {
    printf("异常转换：%d\n", ret);
  }
  return 0;
}