/* $OpenBSD: strerror_r.c,v 1.8 2013/06/01 21:26:18 stsp Exp $ */
/* Public Domain <marc@snafu.org> */

#include <errno.h>
#include <limits.h>
#include <string.h>
extern int sys_nerr;
extern const char *const sys_errlist[];

static size_t
__digits10(unsigned int num)
{
    size_t i = 0;

    do {
        num /= 10;
        i++;
    } while (num != 0);

    return i;
}

static int
__itoa(int num, int sign, char *buffer, size_t start, size_t end)
{
    size_t pos;
    unsigned int a;
    int neg;

    if (sign && num < 0) {
        a = -num;
        neg = 1;
    }
    else {
        a = num;
        neg = 0;
    }

    pos = start + __digits10(a);
    if (neg)
        pos++;

    if (pos < end)
        buffer[pos] = '\0';
    else
        return ERANGE;
    pos--;
    do {
        buffer[pos] = (a % 10) + '0';
        pos--;
        a /= 10;
    } while (a != 0);
    if (neg)
        buffer[pos] = '-';
    return 0;
}


static int
__num2string(int num, int sign, int setid, char *buf, size_t buflen,
    const char *const list[], size_t max, const char *def)
{
    int ret = 0;
    size_t len;

    (void *)&setid;
    if (0 <= num && num < max) {
        len = strlcpy(buf, list[num], buflen);
        if (len >= buflen)
            ret = ERANGE;
    } else {
        len = strlcpy(buf, def, buflen);
        if (len >= buflen)
            ret = ERANGE;
        else {
            ret = __itoa(num, sign, buf, len, buflen);
            if (ret == 0)
                ret = EINVAL;
        }
    }

    return ret;
}

#define UPREFIX "Unknown error: "

int
strerror_r(int errnum, char *strerrbuf, size_t buflen)
{
    int save_errno;
    int ret_errno;

    save_errno = errno;

    ret_errno = __num2string(errnum, 1, 1, strerrbuf, buflen,
        sys_errlist, sys_nerr, UPREFIX);

    errno = ret_errno ? ret_errno : save_errno;
    return (ret_errno);
}