Recursively find the bounding box of mismatched bytes between two arrays

check_range.c

unsigned check_range(const char *bad, const char *good, size_t len, size_t bounds[2])
{
    if (len < 2) {
        if (len)
            return *bad != *good;
        return 0;
    } else if (memcmp(bad, good, len)) {
        size_t subbounds[2][2] = { { 0 } };
        int  leftbad = check_range(&bad[0      ], &good[0      ],       len / 2, subbounds[0]);
        int rightbad = check_range(&bad[len / 2], &good[len / 2], len - len / 2, subbounds[1]);

        // return leftmost and rightmost bad bounds
        bounds[0] = subbounds[ leftbad ? 0 : 1][0] + ( leftbad ?             0 : len - len / 2);
        bounds[1] = subbounds[rightbad ? 1 : 0][1] + (rightbad ? len - len / 2 :             0);

        return leftbad + rightbad;
    } else {
        return 0;
    }
}