vlibc/include/termios.h

#ifndef VLIBC_TERMIOS_H
#define VLIBC_TERMIOS_H

/*
 * vlibc — <termios.h>.
 *
 * General terminal interface (POSIX.1-2008 base): the termios structure and
 * the tcgetattr/tcsetattr/tcsendbreak/tcdrain/tcflush/tcflow query-and-set
 * functions plus the cfgetispeed/cfgetospeed/cfsetispeed/cfsetospeed baud
 * helpers, over the kernel's TCGETS/TCSETS ioctls (SYS_ioctl).
 *
 *   Level 1 (onlyposix): tcgetattr, tcsetattr, tcsendbreak, tcdrain,
 *                        tcflush, tcflow, cfgetispeed, cfgetospeed,
 *                        cfsetispeed, cfsetospeed (POSIX base).
 *   Level 2 (muslmimic): cfmakeraw, cfsetspeed (BSD/glibc extensions),
 *                        tcgetsid (XSI [CX] — glibc declares it only under
 *                        __USE_XOPEN2K8, not base __USE_POSIX).
 *
 * struct termios is a byte-for-byte copy of the x86_64 kernel termios
 * (asm-generic/termbits.h), pinned by the static assertions below. The
 * kernel TCGETS/TCSETS ioctls copy exactly sizeof(struct termios) bytes of
 * this layout (verified empirically on this host: TCGETS writes 36 bytes);
 * any divergence would silently corrupt c_cc. Unlike glibc's 60-byte
 * userspace struct (NCCS 32 + trailing ispeed/ospeed members), the speed
 * is carried only in the c_cflag CBAUD/CIBAUD bit fields, exactly as the
 * kernel encodes it — so the ioctl copies the whole structure both ways
 * with nothing left stale.
 *
 * The baud-rate constants B0..B4000000 are the KERNEL CBAUD encodings
 * (B9600 is 0x0d, B38400 is 0x0f, B57600 is 0x1001, ...), NOT glibc's
 * real-numbers-in-speed_t scheme. cfgetospeed()/cfgetispeed() return these
 * constants and cfsetospeed()/cfsetispeed()/cfsetspeed() accept them, so
 * a speed round-trips through the c_cflag bits untouched. This is the same
 * choice musl makes.
 *
 * All flag, control-character, baud, and action constants below are Linux
 * x86_64 kernel-UAPI facts transcribed from asm-generic/termbits.h and
 * asm-generic/termbits-common.h. The ioctl request numbers (TCGETS,
 * TCSETS, TCSBRK, TCXONC, TCFLSH, TIOCGSID) are Linux-only and stay
 * private to src/termios/termios.c, matching the sys/ioctl.h-less layout
 * of the tree today (they belong to a future <sys/ioctl.h>).
 *
 * No declaration carries an intent attribute: tcgetattr/tcsetattr &c
 * perform I/O, and the cf* speed helpers read or write the caller's
 * termios through a pointer that may alias arbitrary memory — const/pure
 * would be unsound (same rationale as <fcntl.h>).
 */

#include <vlibc/features.h>

#include <stddef.h>

#include <sys/types.h>

#ifdef __cplusplus
extern "C" {
#endif

/* ---- Basic types ---- */

typedef unsigned char cc_t;    /* control-character value */
typedef unsigned int speed_t;  /* baud rate (a B* constant) */
typedef unsigned int tcflag_t; /* mode-flag bit mask */

/* ---- struct termios (x86_64 kernel layout) ---- */

#define NCCS 19 /* control-character slots (kernel UAPI) */

struct termios
{
    tcflag_t c_iflag; /* 0: input mode flags */
    tcflag_t c_oflag; /* 4: output mode flags */
    tcflag_t c_cflag; /* 8: control mode flags */
    tcflag_t c_lflag; /* 12: local mode flags */
    cc_t c_line;      /* 16: line discipline */
    cc_t c_cc[NCCS];  /* 17: control characters */
};

/* Pin the kernel layout (TCGETS/TCSETS copy this exact size and shape). */
_Static_assert(sizeof(struct termios) == 36, "struct termios must match the x86_64 kernel layout");
_Static_assert(offsetof(struct termios, c_lflag) == 12, "c_lflag must sit at offset 12");
_Static_assert(offsetof(struct termios, c_line) == 16, "c_line must sit at offset 16");
_Static_assert(offsetof(struct termios, c_cc) == 17, "c_cc must sit at offset 17");

/* ---- Control characters (indices into c_cc) ---- */

#define VINTR 0     /* interrupt character */
#define VQUIT 1     /* quit character */
#define VERASE 2    /* erase character */
#define VKILL 3     /* kill character */
#define VEOF 4      /* end-of-file character */
#define VTIME 5     /* timeout for non-canonical read */
#define VMIN 6      /* min characters for non-canonical read */
#define VSWTC 7     /* switch character (System V) */
#define VSTART 8    /* start character */
#define VSTOP 9     /* stop character */
#define VSUSP 10    /* suspend character */
#define VEOL 11     /* alternate end-of-line character */
#define VREPRINT 12 /* reprint character */
#define VDISCARD 13 /* discard character */
#define VWERASE 14  /* word-erase character */
#define VLNEXT 15   /* literal-next character */
#define VEOL2 16    /* alternate end-of-line character */

/* ---- c_iflag: input mode flags ---- */

#define IGNBRK 0x0001  /* ignore break condition */
#define BRKINT 0x0002  /* signal interrupt on break */
#define IGNPAR 0x0004  /* ignore characters with parity errors */
#define PARMRK 0x0008  /* mark parity and framing errors */
#define INPCK 0x0010   /* enable input parity check */
#define ISTRIP 0x0020  /* strip 8th bit off characters */
#define INLCR 0x0040   /* map NL to CR on input */
#define IGNCR 0x0080   /* ignore CR */
#define ICRNL 0x0100   /* map CR to NL on input */
#define IUCLC 0x0200   /* map uppercase to lowercase on input */
#define IXON 0x0400    /* enable start/stop output control */
#define IXANY 0x0800   /* any character will restart after stop */
#define IXOFF 0x1000   /* enable start/stop input control */
#define IMAXBEL 0x2000 /* ring bell on input queue full */
#define IUTF8 0x4000   /* input is UTF-8 */

/* ---- c_oflag: output mode flags ---- */

#define OPOST 0x0001  /* perform output processing */
#define OLCUC 0x0002  /* map lowercase to uppercase on output */
#define ONLCR 0x0004  /* map NL to CR-NL on output */
#define OCRNL 0x0008  /* map CR to NL on output */
#define ONOCR 0x0010  /* no CR output at column 0 */
#define ONLRET 0x0020 /* NL performs CR function on output */
#define OFILL 0x0040  /* use fill characters for delay */
#define OFDEL 0x0080  /* fill is DEL, else NUL */
#define NLDLY 0x0100  /* newline delay mask */
#define NL0 0x0000
#define NL1 0x0100
#define CRDLY 0x0600 /* carriage-return delay mask */
#define CR0 0x0000
#define CR1 0x0200
#define CR2 0x0400
#define CR3 0x0600
#define TABDLY 0x1800 /* horizontal-tab delay mask */
#define TAB0 0x0000
#define TAB1 0x0800
#define TAB2 0x1000
#define TAB3 0x1800
#define XTABS 0x1800 /* TAB3: expand tabs to spaces */
#define BSDLY 0x2000 /* backspace delay mask */
#define BS0 0x0000
#define BS1 0x2000
#define VTDLY 0x4000 /* vertical-tab delay mask */
#define VT0 0x0000
#define VT1 0x4000
#define FFDLY 0x8000 /* form-feed delay mask */
#define FF0 0x0000
#define FF1 0x8000

/* ---- c_cflag: control mode flags ---- */

#define CBAUD 0x100f       /* baud-rate mask (includes CBAUDEX) */
#define CSIZE 0x0030       /* character-size mask */
#define CS5 0x0000         /* 5 bits */
#define CS6 0x0010         /* 6 bits */
#define CS7 0x0020         /* 7 bits */
#define CS8 0x0030         /* 8 bits */
#define CSTOPB 0x0040      /* two stop bits, else one */
#define CREAD 0x0080       /* enable receiver */
#define PARENB 0x0100      /* enable parity */
#define PARODD 0x0200      /* odd parity, else even */
#define HUPCL 0x0400       /* hang up on last close */
#define CLOCAL 0x0800      /* ignore modem status lines */
#define CBAUDEX 0x1000     /* extended baud-rate mask (above B38400) */
#define CRTSCTS 0x80000000 /* enable RTS/CTS flow control */

/* ---- c_lflag: local mode flags ---- */

#define ISIG 0x0001     /* enable signals */
#define ICANON 0x0002   /* canonical mode (line-buffered) */
#define XCASE 0x0004    /* canonical uppercase/lowercase presentation */
#define ECHO 0x0008     /* enable echo */
#define ECHOE 0x0010    /* echo erase as backspace */
#define ECHOK 0x0020    /* echo KILL */
#define ECHONL 0x0040   /* echo NL */
#define NOFLSH 0x0080   /* disable flush after interrupt/quit/suspend */
#define TOSTOP 0x0100   /* send SIGTTOU on background output */
#define ECHOCTL 0x0200  /* echo control characters as ^X */
#define ECHOPRT 0x0400  /* echo erase as backspace-print-backspace */
#define ECHOKE 0x0800   /* BSD: erase entire line on KILL */
#define FLUSHO 0x1000   /* output is being flushed */
#define PENDIN 0x4000   /* reprint pending input at next read */
#define IEXTEN 0x8000   /* enable implementation-defined input processing */
#define EXTPROC 0x10000 /* external processing */

/* ---- Baud rates (kernel CBAUD encodings — see the header comment) ---- */

#define B0 0x00000000 /* hang up */
#define B50 0x00000001
#define B75 0x00000002
#define B110 0x00000003
#define B134 0x00000004
#define B150 0x00000005
#define B200 0x00000006
#define B300 0x00000007
#define B600 0x00000008
#define B1200 0x00000009
#define B1800 0x0000000a
#define B2400 0x0000000b
#define B4800 0x0000000c
#define B9600 0x0000000d
#define B19200 0x0000000e
#define B38400 0x0000000f
#define B57600 0x00001001 /* CBAUDEX | 1 */
#define B115200 0x00001002
#define B230400 0x00001003
#define B460800 0x00001004
#define B500000 0x00001005
#define B576000 0x00001006
#define B921600 0x00001007
#define B1000000 0x00001008
#define B1152000 0x00001009
#define B1500000 0x0000100a
#define B2000000 0x0000100b
#define B2500000 0x0000100c
#define B3000000 0x0000100d
#define B3500000 0x0000100e
#define B4000000 0x0000100f

/* ---- tcsetattr optional_actions ---- */

#define TCSANOW 0   /* change immediately */
#define TCSADRAIN 1 /* change after output drains */
#define TCSAFLUSH 2 /* drain output and discard input */

/* ---- tcflush queue_selector ---- */

#define TCIFLUSH 0  /* discard data received but not yet read */
#define TCOFLUSH 1  /* discard data written but not yet transmitted */
#define TCIOFLUSH 2 /* discard both */

/* ---- tcflow action ---- */

#define TCOOFF 0 /* suspend output */
#define TCOON 1  /* restart suspended output */
#define TCIOFF 2 /* transmit a STOP character */
#define TCION 3  /* transmit a START character */

/* ---- Level 1 (POSIX base) ---- */

/*
 * Store the terminal attributes of the terminal open on fildes into
 * *termios_p. Return 0 on success, or -1 with errno set (ENOTTY when
 * fildes is not a terminal, EBADF on a bad descriptor).
 */
int
tcgetattr(int fildes, struct termios *termios_p);

/*
 * Set the terminal attributes of the terminal open on fildes from
 * *termios_p, applying optional_actions (TCSANOW apply immediately,
 * TCSADRAIN wait for output to drain, TCSAFLUSH drain and then discard
 * unread input). Return 0 on success, or -1 with errno set (EINVAL for an
 * invalid optional_actions, ENOTTY/EBADF as for tcgetattr).
 */
int
tcsetattr(int fildes, int optional_actions, const struct termios *termios_p);

/*
 * Transmit a break condition on the terminal open on fildes. The duration
 * argument is ignored (POSIX leaves a nonzero duration
 * implementation-defined). Return 0 on success or -1 with errno set.
 */
int
tcsendbreak(int fildes, int duration);

/*
 * Wait until all output written to the terminal open on fildes has been
 * transmitted. Return 0 on success or -1 with errno set.
 */
int
tcdrain(int fildes);

/*
 * Discard data written but not yet transmitted (TCOFLUSH), data received
 * but not yet read (TCIFLUSH), or both (TCIOFLUSH) on the terminal open on
 * fildes. Return 0 on success or -1 with errno set (EINVAL for an invalid
 * queue_selector).
 */
int
tcflush(int fildes, int queue_selector);

/*
 * Suspend or restart transmission (TCOOFF/TCOON) or transmit a STOP/START
 * character (TCIOFF/TCION) on the terminal open on fildes. Return 0 on
 * success or -1 with errno set (EINVAL for an invalid action).
 */
int
tcflow(int fildes, int action);

/*
 * Return the input baud rate stored in *termios_p (a B* constant), as
 * encoded in the c_cflag CIBAUD field, or B0 when the input rate is not
 * separately stored (the kernel then treats it as equal to the output
 * rate, and cfsetispeed with B0 selects exactly that).
 */
speed_t
cfgetispeed(const struct termios *termios_p);

/*
 * Return the output baud rate stored in *termios_p (a B* constant), as
 * encoded in the c_cflag CBAUD field.
 */
speed_t
cfgetospeed(const struct termios *termios_p);

/*
 * Store speed as the input baud rate of *termios_p. Accept any value that
 * fits the CBAUD encoding (B0 means "input rate follows the output rate");
 * an out-of-range speed yields -1 with errno EINVAL.
 */
int
cfsetispeed(struct termios *termios_p, speed_t speed);

/*
 * Store speed as the output baud rate of *termios_p. Accept any value that
 * fits the CBAUD encoding (see cfsetispeed); an out-of-range speed yields
 * -1 with errno EINVAL.
 */
int
cfsetospeed(struct termios *termios_p, speed_t speed);

#if VLIBC_LEVEL_GE(2)

/* Level 2 (muslmimic): BSD/glibc extensions and XSI [CX] additions. */

/*
 * Set *termios_p to the "raw" mode of the old Version-7 terminal driver:
 * input available character by character, echoing and all special
 * processing of input and output characters disabled (clear IGNBRK BRKINT
 * PARMRK ISTRIP INLCR IGNCR ICRNL IXON, clear OPOST, clear ECHO ECHONL
 * ICANON ISIG IEXTEN, select CS8 and no parity). Does not report errors.
 */
void
cfmakeraw(struct termios *termios_p);

/*
 * Store speed as both the input and the output baud rate of *termios_p
 * (cfsetospeed then cfsetispeed with the same value). Return 0 on success
 * or -1 with errno EINVAL for an out-of-range speed.
 */
int
cfsetspeed(struct termios *termios_p, speed_t speed);

/*
 * Return the session id of the session that has the terminal open on
 * fildes as its controlling terminal, or -1 with errno set when fildes is
 * not a controlling terminal (ENOTTY).
 */
pid_t
tcgetsid(int fildes);

#endif /* VLIBC_LEVEL_GE(2) */

#ifdef __cplusplus
}
#endif

#endif /* VLIBC_TERMIOS_H */