/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2026.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU Lesser General Public License as published   *
* by the Free Software Foundation, either version 3 or (at your option)   *
* any later version. This program is distributed without any warranty.    *
* See the files COPYING.lgpl-v3 and COPYING.gpl-v3 for details.           *
\*************************************************************************/

#define _XOPEN_SOURCE 600
#include <stdlib.h>
#include <fcntl.h>
#include "pty_master_open.h"            /* Declares ptyMasterOpen() */
#include "tlpi_hdr.h"

int
ptyMasterOpen(char *slaveName, size_t snLen)
{
    int masterFd, savedErrno;
    char *p;

    masterFd = posix_openpt(O_RDWR | O_NOCTTY);         /* Open pty master */
    if (masterFd == -1)
        return -1;

    if (grantpt(masterFd) == -1) {              /* Grant access to slave pty */
        savedErrno = errno;
        close(masterFd);                        /* Might change 'errno' */
        errno = savedErrno;
        return -1;
    }

    if (unlockpt(masterFd) == -1) {             /* Unlock slave pty */
        savedErrno = errno;
        close(masterFd);                        /* Might change 'errno' */
        errno = savedErrno;
        return -1;
    }

    p = ptsname(masterFd);                      /* Get slave pty name */
    if (p == NULL) {
        savedErrno = errno;
        close(masterFd);                        /* Might change 'errno' */
        errno = savedErrno;
        return -1;
    }

    if (strlen(p) < snLen) {
        strncpy(slaveName, p, snLen);
    } else {                    /* Return an error if buffer too small */
        close(masterFd);
        errno = EOVERFLOW;
        return -1;
    }

    return masterFd;
}