#include <string.h>
#include <stdio.h>
#include <errno.h>

static const char *sys_errlist[] = {
    [EPERM]           = "Operation not permitted",
    [ENOENT]          = "No such file or directory",
    [ESRCH]           = "No such process",
    [EINTR]           = "Interrupted system call",
    [EIO]             = "Input/output error",
    [ENXIO]           = "No such device or address",
    [E2BIG]           = "Argument list too long",
    [ENOEXEC]         = "Exec format error",
    [EBADF]           = "Bad file descriptor",
    [ECHILD]          = "No child processes",
    [EAGAIN]          = "Resource temporarily unavailable",
    [ENOMEM]          = "Cannot allocate memory",
    [EACCES]          = "Permission denied",
    [EFAULT]          = "Bad address",
    [ENOTBLK]         = "Block device required",
    [EBUSY]           = "Device or resource busy",
    [EEXIST]          = "File exists",
    [EXDEV]           = "Invalid cross-device link",
    [ENODEV]          = "No such device",
    [ENOTDIR]         = "Not a directory",
    [EISDIR]          = "Is a directory",
    [EINVAL]          = "Invalid argument",
    [ENFILE]          = "Too many open files in system",
    [EMFILE]          = "Too many open files",
    [ENOTTY]          = "Inappropriate ioctl for device",
    [ETXTBSY]         = "Text file busy",
    [EFBIG]           = "File too large",
    [ENOSPC]          = "No space left on device",
    [ESPIPE]          = "Illegal seek",
    [EROFS]           = "Read-only file system",
    [EMLINK]          = "Too many links",
    [EPIPE]           = "Broken pipe",
    [EDOM]            = "Numerical argument out of domain",
    [ERANGE]          = "Numerical result out of range",
    [EDEADLK]         = "Resource deadlock avoided",
    [ENAMETOOLONG]    = "File name too long",
    [ENOLCK]          = "No locks available",
    [ENOSYS]          = "Function not implemented",
    [ENOTEMPTY]       = "Directory not empty",
    [ELOOP]           = "Too many levels of symbolic links",
    [ENOMSG]          = "No message of desired type",
    [EIDRM]           = "Identifier removed",
    [ECHRNG]          = "Channel number out of range",
    [EL2NSYNC]        = "Level 2 not synchronized",
    [EL3HLT]          = "Level 3 halted",
    [EL3RST]          = "Level 3 reset",
    [ELNRNG]          = "Link number out of range",
    [EUNATCH]         = "Protocol driver not attached",
    [ENOCSI]          = "No CSI structure available",
    [EL2HLT]          = "Level 2 halted",
    [EBADE]           = "Invalid exchange",
    [EBADR]           = "Invalid request descriptor",
    [EXFULL]          = "Exchange full",
    [ENOANO]          = "No anode",
    [EBADRQC]         = "Invalid request code",
    [EBADSLT]         = "Invalid slot",
    [EBFONT]          = "Bad font file format",
    [ENOSTR]          = "Device not a stream",
    [ENODATA]         = "No data available",
    [ETIME]           = "Timer expired",
    [ENOSR]           = "Out of streams resources",
    [ENONET]          = "Machine is not on the network",
    [ENOPKG]          = "Package not installed",
    [EREMOTE]         = "Object is remote",
    [ENOLINK]         = "Link has been severed",
    [EADV]            = "Advertise error",
    [ESRMNT]          = "Srmount error",
    [ECOMM]           = "Communication error on send",
    [EPROTO]          = "Protocol error",
    [EMULTIHOP]       = "Multihop attempted",
    [EDOTDOT]         = "RFS specific error",
    [EBADMSG]         = "Bad message",
    [EOVERFLOW]       = "Value too large for defined data type",
    [ENOTUNIQ]        = "Name not unique on network",
    [EBADFD]          = "File descriptor in bad state",
    [EREMCHG]         = "Remote address changed",
    [ELIBACC]         = "Can not access a needed shared library",
    [ELIBBAD]         = "Accessing a corrupted shared library",
    [ELIBSCN]         = ".lib section in a.out corrupted",
    [ELIBMAX]         = "Attempting to link in too many shared libraries",
    [ELIBEXEC]        = "Cannot exec a shared library directly",
    [EILSEQ]          = "Invalid or incomplete multibyte or wide character",
    [ERESTART]        = "Interrupted system call should be restarted",
    [ESTRPIPE]        = "Streams pipe error",
    [EUSERS]          = "Too many users",
    [ENOTSOCK]        = "Socket operation on non-socket",
    [EDESTADDRREQ]    = "Destination address required",
    [EMSGSIZE]        = "Message too long",
    [EPROTOTYPE]      = "Protocol wrong type for socket",
    [ENOPROTOOPT]     = "Protocol not available",
    [EPROTONOSUPPORT] = "Protocol not supported",
    [ESOCKTNOSUPPORT] = "Socket type not supported",
    [ENOTSUP]         = "Operation not supported",
    [EPFNOSUPPORT]    = "Protocol family not supported",
    [EAFNOSUPPORT]    = "Address family not supported by protocol",
    [EADDRINUSE]      = "Address already in use",
    [EADDRNOTAVAIL]   = "Cannot assign requested address",
    [ENETDOWN]        = "Network is down",
    [ENETUNREACH]     = "Network is unreachable",
    [ENETRESET]       = "Network dropped connection on reset",
    [ECONNABORTED]    = "Software caused connection abort",
    [ECONNRESET]      = "Connection reset by peer",
    [ENOBUFS]         = "No buffer space available",
    [EISCONN]         = "Transport endpoint is already connected",
    [ENOTCONN]        = "Transport endpoint is not connected",
    [ESHUTDOWN]       = "Cannot send after transport endpoint shutdown",
    [ETOOMANYREFS]    = "Too many references: cannot splice",
    [ETIMEDOUT]       = "Connection timed out",
    [ECONNREFUSED]    = "Connection refused",
    [EHOSTDOWN]       = "Host is down",
    [EHOSTUNREACH]    = "No route to host",
    [EALREADY]        = "Operation already in progress",
    [EINPROGRESS]     = "Operation now in progress",
    [ESTALE]          = "Stale file handle",
    [EUCLEAN]         = "Structure needs cleaning",
    [ENOTNAM]         = "Not a XENIX named type file",
    [ENAVAIL]         = "No XENIX semaphores available",
    [EISNAM]          = "Is a named type file",
    [EREMOTEIO]       = "Remote I/O error",
    [EDQUOT]          = "Disk quota exceeded",
    [ENOMEDIUM]       = "No medium found",
    [EMEDIUMTYPE]     = "Wrong medium type",
    [ECANCELED]       = "Operation canceled",
    [ENOKEY]          = "Required key not available",
    [EKEYEXPIRED]     = "Key has expired",
    [EKEYREVOKED]     = "Key has been revoked",
    [EKEYREJECTED]    = "Key was rejected by service",
    [EOWNERDEAD]      = "Owner died",
    [ENOTRECOVERABLE] = "State not recoverable",
    [ERFKILL]         = "Operation not possible due to RF-kill",
    [EHWPOISON]       = "Memory page has hardware error",
};
static int n_sys_errlist = sizeof sys_errlist / sizeof sys_errlist[0];

static char g_msg_buf[128];

char *strerror(int errnum)
{
    if (errnum <= 0 || errnum >= n_sys_errlist) {
        snprintf(g_msg_buf, sizeof g_msg_buf, "Unknown error: %d", errnum);
    } else {
        strncpy(g_msg_buf, sys_errlist[errnum], sizeof g_msg_buf - 1);
        g_msg_buf[sizeof g_msg_buf - 1] = '\0';
    }

    return g_msg_buf;
}