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

static inline long long strtonum(const char *nptr, long long minval,
                                  long long maxval, const char **errstr) {
    const char *p = nptr;
    char *endptr;
    long long result;
    int saved_errno;

    if (errstr != NULL)
        *errstr = NULL;

    if (nptr == NULL || *nptr == '\0') {
        if (errstr != NULL)
            *errstr = "invalid";
        errno = EINVAL;
        return 0;
    }

    if (minval > maxval) {
        if (errstr != NULL)
            *errstr = "invalid";
        errno = EINVAL;
        return 0;
    }

    while (isspace((unsigned char)*p))
        p++;

    saved_errno = errno;
    errno = 0;

    result = strtoll(p, &endptr, 10);

    if (errno == ERANGE) {
        if (errstr != NULL) {
            *errstr = (result == LLONG_MIN || result < minval) ?
                      "too small" : "too large";
        }
        errno = ERANGE;
        return 0;
    }

    if (endptr == p) {
        if (errstr != NULL)
            *errstr = "invalid";
        errno = EINVAL;
        return 0;
    }

    while (isspace((unsigned char)*endptr))
        endptr++;
    if (*endptr != '\0') {
        if (errstr != NULL)
            *errstr = "invalid";
        errno = EINVAL;
        return 0;
    }

    if (result < minval) {
        if (errstr != NULL)
            *errstr = "too small";
        errno = ERANGE;
        return 0;
    }
    if (result > maxval) {
        if (errstr != NULL)
            *errstr = "too large";
        errno = ERANGE;
        return 0;
    }

    if (errstr != NULL)
        *errstr = NULL;
    return result;
}

static inline void *reallocf(void *ptr, size_t size) {
    void *new_ptr = realloc(ptr, size);
    if (new_ptr == NULL && size != 0) {
        free(ptr);
    }
    return new_ptr;
}