C语言实现int转换string

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

int string2int(const char * string)
{
    int value = 0;
    int index = 0;
    for(;string[index] >= ‘0‘ && string[index] <= ‘9‘; index ++)
    {
        value = value * 10 + string[index] - ‘0‘;
    }
    return value;
}

int string_reverse(char * strSrc)
{
    int len = 0;
    int i = 0;
    char * output = NULL;
    char * pstr = strSrc;  
    while(* pstr)
    {
        pstr++;
        len++;
    }
    output = (char *)malloc(len);
    if(output == NULL)
    {
        perror("malloc");
        return -1;
    }
    for(i = 0; i < len ;i++)
    {
        output[i] = strSrc[len - i -1];    
        printf("output[%d] = %c\n",len - i -1,strSrc[len - i - 1]);
    }
    output[len] = ‘\0‘;
    strcpy(strSrc, output);
    return 0;
}

int  int2string(int value, char * output)
{
    int index = 0;
    if(value == 0)
    {
        output[0] = value + ‘0‘;
        return 1;
    }
    else
    {
        while(value)
        {
            output[index] = value % 10 + ‘0‘;
            index ++;    
            value /= 10;
        }
        string_reverse(output);
        return 1;
    }
}
int main()
{    
#if 0
    char string[12] = "1234";
    int value = string2int(string);
    printf("value = %d\n", value);
#endif
    
    char string[128] = {0};
int value  = 123;
    int2string(value, string);
    printf("int_to_string=============:%s\n",string);

    return 0;
}