itoa()和atoi()/atol()的源码(转…
来源:互联网 发布:海岛奇兵攻略软件 编辑:程序博客网 时间:2024/06/03 07:17
- #include
- #include
- #include
- long __cdecl atol(
- const char *nptr
- )
- {
- int c;
- long total;
- int sign;
- while ( isspace((int)(unsigned char)*nptr) )
- ++nptr;
- c = (int)(unsigned char)*nptr++;
- sign = c;
- if (c == ''-'' || c == ''+'')
- c = (int)(unsigned char)*nptr++;
- total = 0;
- while (isdigit(c)) {
- total = 10 * total + (c - ''0'');
- c = (int)(unsigned char)*nptr++;
- }
- if (sign == ''-'')
- return -total;
- else
- return total;
- }
- int __cdecl atoi(
- const char *nptr
- )
- {
- return (int)atol(nptr);
- }
- #ifndef _NO_INT64
- __int64 __cdecl _atoi64(
- const char *nptr
- )
- {
- int c;
- __int64 total;
- int sign;
- while ( isspace((int)(unsigned char)*nptr) )
- ++nptr;
- c = (int)(unsigned char)*nptr++;
- sign = c;
- if (c == ''-'' || c == ''+'')
- c = (int)(unsigned char)*nptr++;
- total = 0;
- while (isdigit(c)) {
- total = 10 * total + (c - ''0'');
- c = (int)(unsigned char)*nptr++;
- }
- if (sign == ''-'')
- return -total;
- else
- return total;
- }
- #endif
- #include
- #include
- #include
- char* _itoa(int value, char* string, int radix)
- {
- char tmp[33];
- char* tp = tmp;
- int i;
- unsigned v;
- int sign;
- char* sp;
- if (radix > 36 || radix <= 1)
- {
- __set_errno(EDOM);
- return 0;
- }
- sign = (radix == 10 && value < 0);
- if (sign)
- v = -value;
- else
- v = (unsigned)value;
- while (v || tp == tmp)
- {
- i = v % radix;
- v = v / radix;
- if (i < 10)
- *tp++ = i+''0'';
- else
- *tp++ = i + ''a'' - 10;
- }
- if (string == 0)
- string = (char*)malloc((tp-tmp)+sign+1);
- sp = string;
- if (sign)
- *sp++ = ''-'';
- while (tp > tmp)
- *sp++ = *--tp;
- *sp = 0;
- return string;
- }
- PS1: atoi()可以用二维数组的索引来实现,避免*10的循环。
- PS2: itoa()采用返回堆指针的方式得到结果,不会造成memory leak和指针问题。但是不可以通过传入的char*string返回结果,会造成指针问题。(可以改写为char**string,因此微软的sdk中实现的方式有问题)
- 注:源码可在VC目录下找到