Strtol see progress

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>

long strtol(char* nPtr, char **endPtr , int base)
{

char *string;
long returnedNumber = 0;
int numberSign;

assert(nPtr); /* quits if string is empty */
string = nPtr; /* string points to the same place as nPtr*/

while(isspace(* string)) /* omitt white numbers*/
{
    string++;
}

if(*string =='-')
{
    numberSign = 1;
    string++;
}
else
{
    if(*string =='+')
    {
        numberSign = 0;
        string++;
    }
    else numberSign = 0;
}


if((base == 8) && (*string =='0'))
{
    string++;
}

if((base == 16) && (*string =='0'))
{
    string++;

    if((*string =='x')||(*string =='X'))
    {
        string++;
    }
    else
    {
        string--;
    }
}
if((*string =='0') && (base == 0))
{
    base = 8;
    string++;

    if((*string =='x')||(*string =='X'))
    {
        base = 16;
        string++;
    }

}
else if(base == 0) /*if the base is 0 and the beginning of string is not 0, 0x or 0X then the base is 10*/
{
    base = 10;
}
if(base < 2 || base > 36)
{
    errno = EINVAL;
    return 0;
}
if((base == 8)&&((*string < '0')||(*string > '7')))

{
    *endPtr = string;
    return 0;
}

if((base == 16) && ((*string < '0')||((*string >'9')&&(*string < 'A'))||((*string > 'F')&&(*string < 'a'))||(*string > 'f')))
{
    string--;
    *endPtr = string;
    return 0;
}



return returnedNumber;
}