bsearch extension

void *lowerbound(void *key, void *base, size_t count, size_t itemsize, int(*compare)(const void *, const void *)){
    size_t lo = 0, hi = count - 1, mid = 0;
    if(compare(key, (char *)base + hi * itemsize) > 0){
        return (char *)base + count * itemsize;
    }
    char *pmid = 0;
    while(lo < hi){
        mid = (lo + hi) >> 1;
        pmid = ((char *)base) + mid * itemsize;
        if(compare(pmid, key) < 0){
            lo = mid + 1;
        }
        else{
            hi = mid;
        }
    }
    return (char *)base + lo * itemsize;
}
void *upperbound(void *key, void *base, size_t count, size_t itemsize, int(*compare)(const void *, const void *)){
    size_t lo = 0, hi = count - 1, mid;
    if(compare(key, (char *)base + hi * itemsize) >= 0){
        return (char *)base + count * itemsize;
    }
    char *pmid = 0;
    while(lo < hi){
        mid = (lo + hi) >> 1;
        char *pmid = ((char *)base) + mid * itemsize;
        if(compare(pmid, key) <= 0){
            lo = mid + 1;
        }
        else{
            hi = mid;
        }
    }
    return (char *)base + lo * itemsize;
}