模仿c的字符转整数函数 atoi

 1 #include<stdio.h>
 2 enum Status {KValid = 0, KInvalid};
 3 int g_nStatus = KValid;
 4  long StrToIntCore(char *str,bool minus)
 5 {
 6     long num = 0;
 7     while (*str !=‘\0‘)
 8     {
 9         if (*str >‘0‘ && *str<‘9‘)
10         {
11             int flag = minus ? -1:1;
12             num = num * 10 + flag*(*str - ‘0‘);
13             if ((!minus && num > 0x7FFFFFFF)||(minus && num <(signed int)0x80000000))
14             {
15                 num = 0;
16                 break;
17             }
18             str++;
19         }
20         else
21         {
22             num = 0;
23             break;
24         }
25     }
26     if (*str == ‘\0‘)
27     {
28         g_nStatus = KValid;
29     }
30     return num;
31 }
32 int StrToInt(char *str)
33 {
34     g_nStatus = KInvalid;
35       long num = 0;
36     if (*str != NULL && *str !=‘\0‘)
37     {
38         bool minus = false;
39         if(*str == ‘+‘)
40             str++;
41         else if(*str == ‘-‘)
42         {
43             str++;
44             minus = true;
45         }
46         if (*str !=‘\0‘)
47         {
48             num = StrToIntCore(str,minus);
49         }
50     }
51     return int(num);
52 }
53 
54 void main()
55 {
56     printf("%d",StrToInt("-12"));
57 }