Packing for mytar

packing.c

#define UID_PACKING_LEN 8

int header_insert_special_int(char* where, size_t size, int32_t val)
{
    int err = 0;
    if (val < 0 || size < sizeof(val))
    {
        err++;
    }
    else
    {
        memset(where, 0, size);
        *(int32_t *)(where+size-sizeof(val)) = htonl(val);
        *where |= 0x80;
    }
    return err;
}

int header_extract_special_int(char* where, int len)
{
    int32_t val = -1;
    if ( (len>=sizeof(val)) && (where[0] & 0x80))
    {
        val = *(int32_t *)(where + len - sizeof(val));
        val = ntohl(val);
    }
    return val;
}


void header_set_uid_bigsafe(char* buf, int32_t uid)
{
    int toobig = 07777777;

    /* Tests if bitpacking is needed */
    if(uid > toobig)
    {
        header_insert_special_int(buf,UID_PACKING_LEN,uid);
    }
    else
    {
        /* Do normal formatting as octal */
    }
}

void header_parse_uid_bigsafe(char* uidstring, uid_t* uid)
{   

    /* Tests if bitpacking was used */
    if(uidstring[0] == '\0')
    {
        *uid = header_extract_special_int(uidstring, UID_PACKING_LEN);
    }
    else
    {
        /* Do normal parsing from octal */
    }
}