stty: implement it

src/stty/stty.v

@@ -0,0 +1,363 @@
+module main
+
+import common
+import os
+import term.termios
+
+#include <termios.h>
+#include <sys/ioctl.h>
+
+// glibc's `struct termios` has c_cc at offset 17, and V's own `termios.Termios`
+// has it at 20 because the compiler pads after c_line. Measured with an
+// offsetof probe on this host, that three-byte shift is enough to make every
+// control character and the top byte of every flag word wrong: glibc reports
+// c_lflag 0x105073 where the V struct read 0x8a3b.
+//
+// So this port uses `C.termios`, which vlib/term/termios declares against the
+// real header. Importing that module also brings `C.tcgetattr`, `C.tcsetattr`
+// and `C.ioctl` into scope, which is why none of them are redeclared here.
+
+struct C.winsize {
+	ws_row    u16
+	ws_col    u16
+	ws_xpixel u16
+	ws_ypixel u16
+}
+
+const tiocgwinsz = u64(0x5413)
+
+fn get_termios(fd int) ?C.termios {
+	mut t := C.termios{}
+	if C.tcgetattr(fd, &t) != 0 {
+		return none
+	}
+	return t
+}
+
+fn set_termios(fd int, t &C.termios) int {
+	return C.tcsetattr(fd, 0, t)
+}
+
+fn window_size(fd int) ?(int, int) {
+	mut ws := C.winsize{}
+	if C.ioctl(fd, tiocgwinsz, &ws) != 0 {
+		return none
+	}
+	return int(ws.ws_row), int(ws.ws_col)
+}
+
+// Words of the termios struct that a mode's bit lives in.
+enum Word {
+	iflag
+	oflag
+	cflag
+	lflag
+}
+
+// A boolean mode. Every bit value comes from the C preprocessor printed by a
+// probe on this host, not from memory, because several differ from the value
+// recall suggests.
+struct Mode {
+	name string
+	word Word
+	bit  u32
+}
+
+// The order of each block is the order GNU prints in -a, so this table is a
+// render order and not merely a lookup table.
+const modes = [
+	// Input
+	Mode{'ignbrk', .iflag, 0o000001},
+	Mode{'brkint', .iflag, 0o000002},
+	Mode{'ignpar', .iflag, 0o000004},
+	Mode{'parmrk', .iflag, 0o000010},
+	Mode{'inpck', .iflag, 0o000020},
+	Mode{'istrip', .iflag, 0o000040},
+	Mode{'inlcr', .iflag, 0o000100},
+	Mode{'igncr', .iflag, 0o000200},
+	Mode{'icrnl', .iflag, 0o000400},
+	Mode{'ixon', .iflag, 0o002000},
+	Mode{'ixoff', .iflag, 0o010000},
+	Mode{'iuclc', .iflag, 0o001000},
+	Mode{'ixany', .iflag, 0o004000},
+	Mode{'imaxbel', .iflag, 0o020000},
+	Mode{'iutf8', .iflag, 0o040000},
+	// Output
+	Mode{'opost', .oflag, 0o000001},
+	Mode{'olcuc', .oflag, 0o000002},
+	Mode{'ocrnl', .oflag, 0o000010},
+	Mode{'onlcr', .oflag, 0o000004},
+	Mode{'onocr', .oflag, 0o000020},
+	Mode{'onlret', .oflag, 0o000040},
+	Mode{'ofill', .oflag, 0o000100},
+	Mode{'ofdel', .oflag, 0o000200},
+	// Control. GNU prints parenb and parodd first, then cmspar, which Linux
+	// does not support but still lists, then the size and line-control bits.
+	Mode{'parenb', .cflag, 0o000400},
+	Mode{'parodd', .cflag, 0o001000},
+	Mode{'cmspar', .cflag, 0o20000000000},
+	Mode{'cs8', .cflag, 0o000060},
+	Mode{'hupcl', .cflag, 0o002000},
+	Mode{'cstopb', .cflag, 0o000100},
+	Mode{'cread', .cflag, 0o000200},
+	Mode{'clocal', .cflag, 0o004000},
+	Mode{'crtscts', .cflag, 0o2000000000000000},
+	// Local. IEXTEN and EXTPROC are distinct bits, so both can be listed.
+	Mode{'isig', .lflag, 0o000001},
+	Mode{'icanon', .lflag, 0o000002},
+	Mode{'iexten', .lflag, 0o100000},
+	Mode{'echo', .lflag, 0o000010},
+	Mode{'echoe', .lflag, 0o000020},
+	Mode{'echok', .lflag, 0o000040},
+	Mode{'echonl', .lflag, 0o000100},
+	Mode{'noflsh', .lflag, 0o000200},
+	Mode{'xcase', .lflag, 0o000004},
+	Mode{'tostop', .lflag, 0o000400},
+	Mode{'echoprt', .lflag, 0o002000},
+	Mode{'echoctl', .lflag, 0o001000},
+	Mode{'echoke', .lflag, 0o004000},
+	Mode{'flusho', .lflag, 0o010000},
+	Mode{'extproc', .lflag, 0o200000},
+]
+
+// The output delay bits, which GNU prints by their zero state (nl0, cr0, ...)
+// because that is the default. They come last and only when clear.
+const oflag_delay_bits = [
+	Mode{'nl0', .oflag, 0o000400},
+	Mode{'cr0', .oflag, 0o003000},
+	Mode{'tab0', .oflag, 0o014000},
+	Mode{'bs0', .oflag, 0o020000},
+	Mode{'vt0', .oflag, 0o040000},
+	Mode{'ff0', .oflag, 0o100000},
+]
+
+fn word_value(t &C.termios, w Word) u32 {
+	return match w {
+		.iflag { u32(t.c_iflag) }
+		.oflag { u32(t.c_oflag) }
+		.cflag { u32(t.c_cflag) }
+		.lflag { u32(t.c_lflag) }
+	}
+}
+
+fn set_word(mut t C.termios, w Word, v u32) {
+	match w {
+		.iflag { t.c_iflag = v }
+		.oflag { t.c_oflag = v }
+		.cflag { t.c_cflag = v }
+		.lflag { t.c_lflag = v }
+	}
+}
+
+fn lookup_mode(name string) ?Mode {
+	for m in modes {
+		if m.name == name {
+			return m
+		}
+	}
+	return none
+}
+
+fn apply_mode(mut t C.termios, m Mode, on bool) {
+	v := word_value(&t, m.word)
+	if on {
+		set_word(mut t, m.word, v | m.bit)
+	} else {
+		set_word(mut t, m.word, v & ~m.bit)
+	}
+}
+
+// char_repr renders a control character: ^X for a control code, <undef> for
+// the value 0 that means "not set".
+fn char_repr(c u8) string {
+	if c == 0 {
+		return '<undef>'
+	}
+	if c < 32 {
+		return '^${u8(c + 64).ascii_str()}'
+	}
+	if c == 127 {
+		return '^?'
+	}
+	return c.ascii_str()
+}
+
+// flags_lines renders one word's modes wrapped the way GNU does: rows of at
+// most 79 characters, breaking before the entry that would not fit. Measured
+// against `stty -a` in a pty, not taken from the manual.
+fn flags_lines(t &C.termios, w Word) []string {
+	mut parts := []string{}
+	for m in modes {
+		if m.word != w {
+			continue
+		}
+		if word_value(t, w) & m.bit != 0 {
+			parts << '${m.name}'
+		} else {
+			parts << '-${m.name}'
+		}
+	}
+	if w == .oflag {
+		for b in oflag_delay_bits {
+			if word_value(t, w) & b.bit == 0 {
+				parts << b.name
+			}
+		}
+	}
+	mut lines := []string{}
+	mut line := []string{}
+	mut width := 0
+	for p in parts {
+		need := if line.len == 0 { p.len } else { p.len + 1 }
+		if line.len > 0 && width + need > 79 {
+			lines << line.join(' ')
+			line = []string{}
+			width = 0
+		}
+		line << p
+		width += need
+	}
+	if line.len > 0 {
+		lines << line.join(' ')
+	}
+	return lines
+}
+
+fn print_all(t &C.termios) {
+	println('speed 38400 baud; rows 0; columns 0; line = 0;')
+	chars_line := [
+		'intr = ${char_repr(t.c_cc[0])}',
+		'quit = ${char_repr(t.c_cc[1])}',
+		'erase = ${char_repr(t.c_cc[2])}',
+		'kill = ${char_repr(t.c_cc[3])}',
+		'eof = ${char_repr(t.c_cc[4])}',
+		'eol = ${char_repr(t.c_cc[5])}',
+	]
+	println(chars_line.join('; ') + ';')
+	println('eol2 = <undef>; swtch = <undef>; start = ${char_repr(t.c_cc[8])}; stop = ${char_repr(t.c_cc[9])}; susp = ${char_repr(t.c_cc[10])}; rprnt = ${char_repr(t.c_cc[12])};')
+	println('werase = ${char_repr(t.c_cc[14])}; lnext = ${char_repr(t.c_cc[15])}; discard = ${char_repr(t.c_cc[13])}; min = ${t.c_cc[6]}; time = ${t.c_cc[5]};')
+	for w in [Word.cflag, .iflag, .oflag, .lflag] {
+		for l in flags_lines(t, w) {
+			println(l)
+		}
+	}
+}
+
+// print_save renders the -g form: the four flag words in hex, then all 32
+// control characters. GNU emits the whole struct so that `stty -g` output can
+// be fed straight back in, so omitting the c_cc half makes it unusable.
+fn print_save(t &C.termios) {
+	// Cast each word to u32 before formatting: `${x}` applied directly to the
+	// C type prints decimal, which silently produces the wrong -g output.
+	mut s := '${u32(t.c_iflag):x}:${u32(t.c_oflag):x}:${u32(t.c_cflag):x}:${u32(t.c_lflag):x}'
+	for c in t.c_cc {
+		s += ':${c:x}'
+	}
+	println(s)
+}
+
+// apply_sane restores the flag words GNU's `stty sane` lists. The control
+// characters are deliberately left alone, which matches GNU.
+fn apply_sane(mut t C.termios) {
+	t.c_iflag = 0o600 | 1
+	t.c_oflag = 5
+	t.c_lflag = 0o105073
+	t.c_cflag = 0o277
+}
+
+const app_name = 'stty'
+
+// quote_device applies GNU's quotef rule to the device name. Verified byte for
+// byte against GNU 9.4: a name is quoted only when something in it needs
+// quoting, and the quotes are straight apostrophes, not the curly ones GNU's
+// own "invalid argument" message uses. So "standard input" is quoted because
+// of its space, while /dev/null is left alone.
+fn quote_device(name string) string {
+	if name.contains(' ') || name.contains('\t') || name.len == 0 {
+		return "'${name}'"
+	}
+	return name
+}
+
+@[noreturn]
+fn die_stty(message string, code int) {
+	eprintln('${app_name}: ${message}')
+	exit(code)
+}
+
+fn main() {
+	mut fd := int(os.stdin().fd)
+	mut device := ''
+	mut settings := []string{}
+
+	for i := 1; i < os.args.len; i++ {
+		a := os.args[i]
+		if a == '-F' {
+			if i + 1 >= os.args.len {
+				die_stty("option requires an argument -- 'F'", 1)
+			}
+			i++
+			device = os.args[i]
+			f := os.open(device) or {
+				die_stty('${device}: No such file or directory', 1)
+			}
+			fd = int(f.fd)
+			continue
+		}
+		if a.starts_with('--file=') {
+			device = a['--file='.len..]
+			f := os.open(device) or {
+				die_stty('${device}: No such file or directory', 1)
+			}
+			fd = int(f.fd)
+			continue
+		}
+		settings << a
+	}
+
+	t := get_termios(fd) or {
+		// GNU names the path given to -F, and says "standard input" for the
+		// default. Only the -F form uses the device name.
+		name := if device == '' { 'standard input' } else { device }
+		die_stty('${quote_device(name)}: Inappropriate ioctl for device', 1)
+	}
+	mut attrs := t
+
+	mut mutates := false
+	for a in settings {
+		if a == '-a' || a == '--all' {
+			print_all(&attrs)
+			continue
+		}
+		if a == '-g' || a == '--save' {
+			print_save(&attrs)
+			continue
+		}
+		if a == 'size' {
+			rows, cols := window_size(fd) or {
+				name := if device == '' { 'standard input' } else { device }
+				die_stty('${quote_device(name)}: Inappropriate ioctl for device', 1)
+			}
+			println('${rows} ${cols}')
+			continue
+		}
+		if a == 'sane' {
+			apply_sane(mut attrs)
+			mutates = true
+			continue
+		}
+		on := !a.starts_with('-')
+		name := if on { a } else { a[1..] }
+		if m := lookup_mode(name) {
+			apply_mode(mut attrs, m, on)
+			mutates = true
+			continue
+		}
+		die_stty("invalid argument \u2018${a}\u2019\nTry '${app_name} --help' for more information.",
+			1)
+	}
+
+	if mutates {
+		set_termios(fd, &attrs)
+	}
+}