glibc/sysdeps/unix/sysv/linux/termios_internals.h

/* termios functions internal implementation header for Linux

   Copyright (C) 1991-2025 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#ifndef TERMIOS_INTERNALS_H
#define TERMIOS_INTERNALS_H 1

#include <stddef.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sysdep.h>
#include <shlib-compat.h>

#include <termios-kernel-consts.h>

/* Alpha got termios2 late, but TCGETS has exactly the same structure
   format and function as TCGETS2. On all other platforms, the termios2
   interface exists as far back as this version of glibc supports.

   For TCSETS* it is more complicated; this is handled in tcsetattr.c.  */
#ifdef __ASSUME_TERMIOS2
# define ARCH_TCGETS KERNEL_TCGETS2
#else
# define ARCH_TCGETS KERNEL_TCGETS
#endif

/* ---- Kernel interface definitions ---- */

/* The the termios2 structure used in the kernel interfaces is not the
   same as the termios structure we use in the libc.  Therefore we
   must translate it here.  */

struct termios2
{
  tcflag_t c_iflag;		/* input mode flags */
  tcflag_t c_oflag;		/* output mode flags */
  tcflag_t c_cflag;		/* control mode flags */
  tcflag_t c_lflag;		/* local mode flags */
#if KERNEL_TERMIOS2_CC_OFFSET < KERNEL_TERMIOS2_LINE_OFFSET
  cc_t c_cc[_TERMIOS2_NCCS];	/* control characters */
  cc_t c_line;			/* line discipline */
#else
  cc_t c_line;			/* line discipline */
  cc_t c_cc[_TERMIOS2_NCCS];	/* control characters */
#endif
  speed_t c_ispeed;		/* input speed */
  speed_t c_ospeed;		/* output speed */
};

/* ---- Application interface definitions ---- */

/*
 * Should old speed_t and struct termios (if applicable) compatibility
 * functions be included?
 */
#define _TERMIOS_OLD_COMPAT SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_42)

/*
 * Old struct termios (without c_ispeed and c_ospeed fields) if
 * applicable. The new struct termios *must* be binary identical up to
 * the sizeof the old structure.
 *
 * This only applies to SPARC and MIPS; for other architectures the
 * new and old speed_t interfaces both use the same struct termios.
 */
#include <old_termios.h>

/* ---- Internal function definitions ---- */

/*
 * Copy a set of c_cc fields of possibly different width. If the target
 * field is longer, then fill with _POSIX_VDISABLE == -1.
 */
static inline void
copy_c_cc (cc_t *to, size_t nto, const cc_t *from, size_t nfrom)
{
  if (nto < nfrom)
    nfrom = nto;

  to = __mempcpy (to, from, nfrom * sizeof(cc_t));
  if (nto > nfrom)
    memset (to, _POSIX_VDISABLE, (nto - nfrom) * sizeof(cc_t));
}

/* Extract the output and input legacy speed fields from c_cflag. */
static inline tcflag_t
cbaud (tcflag_t c_cflag)
{
  return c_cflag & CBAUD;
}

static inline tcflag_t
cibaud (tcflag_t c_cflag)
{
  return cbaud (c_cflag >> IBSHIFT);
}

extern speed_t
___cbaud_to_speed (tcflag_t c_cflag, speed_t other)
    __attribute_const__ attribute_hidden;

extern tcflag_t
___speed_to_cbaud (speed_t speed)
    __attribute_const__ attribute_hidden;

extern void
___termios2_canonicalize_speeds (struct termios2 *k_termios_p)
    attribute_hidden;

#endif /* TERMIOS_INTERNALS_H */