bsearch2

#include <stdio.h>

struct BSearchResult {
    size_t low;
    size_t high;
    int result;
};

struct BSearchResult
bsearch2(const void *key, const void *base, size_t nmemb, size_t size,
         int (*compar)(const void *p1, const void *p2, void *user),
         void *user) {
    size_t low = 0, high = nmemb - 1, mid;
    struct BSearchResult res;
    if (nmemb == 0) {
        res.result = 0;
        res.low = 0;
        res.high = 0;
        return res;
    }
    while (low <= high) {
        mid = low + (high - low) / 2;
        if (compar(key, base + size * mid, user) == 0) {
            res.low = mid;
            while (res.low != -1 &&
                   compar(key, base + size * res.low, user) == 0) {
                res.low--;
            }
            res.low++;
            res.high = mid;
            while (res.high != nmemb &&
                   compar(key, base + size * res.high, user) == 0) {
                res.high++;
            }
            res.result = 1;
            return res;
        } else if (compar(key, base + size * mid, user) > 0) {
            low = mid + 1;
        } else {
            if (mid == 0) {
                low = 0;
                break;
            }
            high = mid - 1;
        }
    }
    res.result = 0;
    res.low = low;
    res.high = low;
    return res;
}