C实现itoa函数的的一种方式

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

void my_toupper(char * str)
{
    while(*str != '\0')
    {
        if((*str >= 'a') && (*str <= 'z'))
            *str += 'A' - 'a';
        str++;
    }
    return ;
}

void my_tolower(char * str)
{
    while(*str != '\0')
    {
        if((*str >= 'A') && (*str <= 'Z'))
            *str -= 'A' - 'a';
        str++;
    }
    return ;
}

int my_itoa(int intger, char * str)
{
	int i       = 0;
    int j       = 0;
    int flag    = 0;
    int len     = 0;
    char * head = NULL;
    char * tail = NULL;
    
    flag = intger;
    
	if(flag < 0)
	{
		intger = -intger;
	}
    
	do{
		str[i++]=intger%10 + '0'; 
	}while((intger/=10)>0); 
 
	if(flag < 0)
		str[i++]='-';
    
	str[i]='\0';
    len  = strlen(str);
    head = str;
    tail = str + len - 1;
    while(head < tail)
    {
        *head ^= *tail;
        *tail ^= *head;
        *head ^= *tail;
        head ++;
        tail --;
    }
    
    return 0;
}
    
int main(int argc, const char * argv[])
{

    char str[1024] = { 0 };    
#if 0
    char str[] = "dfjdflkdsfhWQJWHASDKJSD";
    printf("before str: %s\n", str);
    my_toupper(str);
    my_tolower(str);
    printf("after str: %s\n", str);
#else
    if(argc < 2)
    {
        fprintf(stderr, "Usage %s <int_num>\n", argv[0]);
        return -1;
    }
    
    my_itoa(atoi(argv[1]), str);
    puts(str);
    
#endif

    return 0;
}


           

测试结果