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Use zsh's builtin functions to do I/O with TTY

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Far more robust than the system tools
This commit is contained in:
Kovid Goyal 2022-03-05 10:31:00 +05:30
parent f6706a55ec
commit 30e635a934
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GPG Key ID: 06BC317B515ACE7C
1 changed files with 51 additions and 17 deletions
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68
shell-integration/ssh/bootstrap.sh
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@ -2,14 +2,61 @@
# Copyright (C) 2022 Kovid Goyal <kovid at kovidgoyal.net>
# Distributed under terms of the GPLv3 license.
# read the transmitted data from STDIN
cleanup_on_bootstrap_exit() {
[ -n "$saved_tty_settings" ] && command stty "$saved_tty_settings" 2> /dev/null < /dev/tty
saved_tty_settings=""
}
# try to use zsh's builtin functions for reading/writing to TTY fd as they are superior to the POSIX variants
tty_fd=-1
if builtin zmodload zsh/system 2> /dev/null; then
builtin sysopen -o cloexec -rwu tty_fd -- $TTY 2> /dev/null
[ $tty_fd = -1 ] && builtin sysopen -o cloexec -rwu tty_fd -- /dev/tty 2> /dev/null
fi
if [ $tty_fd -gt -1 ]; then
dcs_to_kitty() {
builtin local b64data
b64data=$(builtin printf "%s" "$2" | builtin command base64)
builtin print -nu "$tty_fd" '\eP@kitty-'"${1}|${b64data//[[:space:]]}"'\e\\'
}
read_one_byte_from_tty() {
builtin sysread -s "1" -i "$tty_fd" n 2> /dev/null
return $?
}
read_n_bytes_from_tty() {
builtin let num_left=$1
while [ $num_left -gt 0 ]; do
builtin sysread -c num_read -s "$num_left" -i "$tty_fd" -o "1" 2> /dev/null || die "Failed to read $num_left bytes from TTY using sysread"
builtin let num_left=$num_left-$num_read
done
}
else
dcs_to_kitty() { printf "\033P@kitty-$1|%s\033\\" "$(printf "%s" "$2" | command base64 | command tr -d \\n)" > /dev/tty; }
read_one_byte_from_tty() {
# We need a way to read a single byte at a time and to read a specified number of bytes in one invocation.
# The options are head -c, read -N and dd
#
# read -N is not in POSIX and dash/posh dont implement it. Also bash seems to read beyond
# the specified number of bytes into an internal buffer.
#
# head -c reads beyond the specified number of bytes into an internal buffer on macOS
#
# POSIX dd works for one byte at a time but for reading X bytes it needs the GNU iflag=count_bytes
# extension, and is anyway unsafe as it can lead to corrupt output when the read syscall is interrupted.
n=$(command dd bs=1 count=1 2> /dev/null < /dev/tty)
return $?
}
read_n_bytes_from_tty() {
# using dd with bs=1 is very slow, so use head. On non GNU coreutils head
# does not limit itself to reading -c bytes only from the pipe so we can potentially lose
# some trailing data, for instance if the user starts typing. Cant be helped.
command head -c "$1" < /dev/tty
}
fi
die() { printf "\033[31m%s\033[m\n\r" "$*" > /dev/stderr; cleanup_on_bootstrap_exit; exit 1; }
dcs_to_kitty() { printf "\033P@kitty-$1|%s\033\\" "$(printf "%s" "$2" | base64 | tr -d \\n)" > /dev/tty; }
debug() { dcs_to_kitty "print" "debug $1"; }
echo_via_kitty() { dcs_to_kitty "echo" "$1"; }
saved_tty_settings=$(command stty -g 2> /dev/null < /dev/tty)
@ -63,10 +110,7 @@ untar_and_read_env() {
tdir=$(mktemp -d "$HOME/.kitty-ssh-kitten-untar-XXXXXXXXXXXX");
[ $? = 0 ] || die "Creating temp directory failed";
# using dd with bs=1 is very slow, so use head. On non GNU coreutils head
# does not limit itself to reading -c bytes only from the pipe so we can potentially lose
# some trailing data, for instance if the user starts typing. Cant be helped.
command head -c "$1" < /dev/tty | command base64 -d | command tar xjf - --no-same-owner -C "$tdir";
read_n_bytes_from_tty "$1" | command base64 -d | command tar xjf - --no-same-owner -C "$tdir";
data_file="$tdir/data.sh";
[ -f "$data_file" ] && . "$data_file";
data_dir="$HOME/$KITTY_SSH_KITTEN_DATA_DIR"
@ -78,19 +122,9 @@ untar_and_read_env() {
}
read_record() {
# We need a way to read a single byte at a time and to read a specified number of bytes in one invocation.
# The options are head -c, read -N and dd
#
# read -N is not in POSIX and dash/posh dont implement it. Also bash seems to read beyond
# the specified number of bytes into an internal buffer.
#
# head -c reads beyond the specified number of bytes into an internal buffer on macOS
#
# POSIX dd works for one byte at a time but for reading X bytes it needs the GNU iflag=count_bytes
# extension, and is anyway unsafe as it can lead to corrupt output when the read syscall is interrupted.
record=""
while :; do
n=$(command dd bs=1 count=1 2> /dev/null < /dev/tty)
read_one_byte_from_tty || die "Reading a byte from the TTY failed"
[ "$n" = "$record_separator" ] && break
record="$record$n"
done