字符串转换成整形值

字符串转换成整形值，能够考虑的异常因素有很多。编写代码之前设计测试用例很有帮助。
  1 enum STATUS{STRNULL=0, STREMPTY, STRINVALID, STROVERFLOW, STRVALID};
  2 enum SIGN{NEGATIVE=0, POSITIVE};
  3 enum STATUS status = STRVALID;
  4 enum SIGN sign = POSITIVE;
  5 int str2int(const char *str)
  6 {
  7     long long num = 0;
  8 
  9     if (str == NULL)
 10     {
 11         status = STRNULL;
 12 
 13         return 0; 
 14     }
 15     while (*str == ' ')
 16     {
 17         str++;
 18     }
 19 
 20     if (*str == '-' || *str == '+')
 21     {    
 22         if (*str == '-')
 23         {
 24             sign = NEGATIVE;
 25         }
 26         if ( *(str+1) == '')
 27         {
 28             status = STREMPTY;
 29 
 30             return 0; 
 31         }
 32 
 33         str++;
 34     }
 35     else if (*str == '')
 36     {
 37         status = STREMPTY;
 38 
 39         return 0; 
 40     }
 41     else
 42     {
 43         while(*str != '')
 44         {
 45             if (*str >= '0' && *str <= '9')
 46             {
 47                 num = num * 10 + *str - '0';
 48 
 49                 if (num > 0x80000000)
 50                 {
 51                     status = STROVERFLOW;
 52 
 53                     return 0; 
 54                 }
 55             }
 56             else
 57             {
 58                 status = STRINVALID;
 59 
 60                 return 0; 
 61             }
 62 
 63             str++;
 64         }
 65 
 66     }
 67     
 68     if (sign == NEGATIVE)
 69     {
 70         num = -num;
 71     }
 72 
 73     return (int)num;
 74 
 75 }
 76 
 77 int main(int argc, char** argv)
 78 {
 79         char *pString = "   -2147483648";
 80     
 81         int num = str2int(pString);
 82 
 83     switch (status)
 84     {
 85     case STRVALID:
 86         {
 87             cout << num << endl;
 88         }
 89         break;
 90     case STREMPTY:
 91         {
 92             cout << "Empty str" << endl;
 93         }
 94         break;
 95     case STRNULL:
 96         {
 97             cout << "NULL str" << endl;
 98         }
 99         break;
100     case STROVERFLOW:
101         {
102             cout << "Overflow str" << endl;
103         }
104         break;
105     default:
106         {
107             cout << "NONE digit str" << endl;
108         }
109     }
110     
111     system("pause");
112 
113     return 0;
114 }