Classic case - hexadecimal to decimal conversion

1. Method 1 uses a first-level pointer

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

int convert (char * myp, int mylen, int * Poutput)
    {
    int i = 0;
    char * pstart = myp + 1;
    char * Pstop = myp + mylen - 1;
    int ant = 0;
    int hex = 1;

    if(Pstop == NULL )
    {
        return -1;
    }

    if(myp == NULL)
        {
        return -1;
    }

    while(Pstop > pstart)
        {
        for(i = 0; i < mylen - 2; i++)
            {
            if(*Pstop >= 'A' && *Pstop <= 'F')
                {
                ant = ant + (*Pstop - 'A' + 10) * hex;
            }
            else
                {
                ant = ant + (*Pstop - '0') * hex;
                }
                Pstop -;
                hex = hex * 16;
            }
    }
    *Poutput = ant;
    return 0;
}

intmain()
    {
    char buf1[10];
    int  output = 0;
    int len ​​= 0;
    int ret = 0;

    scanf("%s",buf1);
    len = strlen (buf1);
    ret = convert(buf1,len,&output);
    if (ret! = 0)
        {
        printf("func convert() error!");
        return ret;
    }
    printf("output:%d \n",output);
    return 0;
}

2. Method 2 uses a secondary pointer

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

int convert (char * myp, int mylen, int ** Poutput)
    {
    int i = 0;
    char * pstart = myp + 1;
    char * Pstop = myp + mylen - 1;
    int ant = 0;
    int hex = 1;
    int *tmp = NULL;

    tmp = (int *)malloc(10);

    if(Pstop == NULL )
    {
        return -1;
    }

    if(myp == NULL)
        {
        return -1;
    }

    while(Pstop > pstart)
        {
        for(i = 0; i < mylen - 2; i++)
            {
            if(*Pstop >= 'A' && *Pstop <= 'F')
                {
                ant = ant + (*Pstop - 'A' + 10) * hex;
            }
            else
                {
                ant = ant + (*Pstop - '0') * hex;
                }
                Pstop -;
                hex = hex * 16;
            }
    }
    tmp = &ant;
    *Poutput = tmp;
    return 0;
}

intmain()
    {
    char buf1[10];
    int  *output = NULL;
    int len ​​= 0;
    int ret = 0;

    scanf("%s",buf1);
    len = strlen (buf1);
    ret = convert(buf1,len,&output);
    if (ret! = 0)
        {
        printf("func convert() error!");
        return ret;
    }
    printf("output:%d \n",*output);

    return 0;
}