helper/wrappedreadline: helper for dealing with wrapped standard streams

helper/wrappedreadline/wrappedreadline.go

@@ -0,0 +1,84 @@
+// wrappedreadline is a package that has helpers for interacting with
+// readline from a panicwrap executable.
+//
+// panicwrap overrides the standard file descriptors so that the child process
+// no longer looks like a TTY. The helpers here access the extra file descriptors
+// passed by panicwrap to fix that.
+package wrappedreadline
+
+import (
+	"os"
+	"runtime"
+
+	"github.com/chzyer/readline"
+)
+
+// These are the file descriptor numbers for the original stdin, stdout, stderr
+// streams from the parent process.
+const (
+	StdinFd  = 3
+	StdoutFd = 4
+	StderrFd = 5
+)
+
+// These are the *os.File values for the standard streams.
+var (
+	Stdin  = os.NewFile(uintptr(StdinFd), "stdin")
+	Stdout = os.NewFile(uintptr(StdoutFd), "stdout")
+	Stderr = os.NewFile(uintptr(StderrFd), "stderr")
+)
+
+// Override overrides the values in readline.Config that need to be
+// set with wrapped values.
+func Override(cfg *readline.Config) *readline.Config {
+	cfg.Stdin = Stdin
+	cfg.Stdout = Stdout
+	cfg.Stderr = Stderr
+
+	cfg.FuncGetWidth = TerminalWidth
+	cfg.FuncIsTerminal = IsTerminal
+
+	var rm RawMode
+	cfg.FuncMakeRaw = rm.Enter
+	cfg.FuncExitRaw = rm.Exit
+
+	return cfg
+}
+
+// IsTerminal determines if this process is attached to a TTY.
+func IsTerminal() bool {
+	// Windows is always a terminal
+	if runtime.GOOS == "windows" {
+		return true
+	}
+
+	// Same implementation as readline but with our custom fds
+	return readline.IsTerminal(StdinFd) && (readline.IsTerminal(StdoutFd) || readline.IsTerminal(StderrFd))
+}
+
+// TerminalWidth gets the terminal width in characters.
+func TerminalWidth() int {
+	if runtime.GOOS == "windows" {
+		return readline.GetScreenWidth()
+	}
+
+	return getWidth()
+}
+
+// RawMode is a helper for entering and exiting raw mode.
+type RawMode struct {
+	state *readline.State
+}
+
+func (r *RawMode) Enter() (err error) {
+	r.state, err = readline.MakeRaw(StdinFd)
+	return err
+}
+
+func (r *RawMode) Exit() error {
+	if r.state == nil {
+		return nil
+	}
+
+	return readline.Restore(StdinFd, r.state)
+}

helper/wrappedreadline/wrappedreadline_unix.go

@@ -0,0 +1,41 @@
+// +build darwin dragonfly freebsd linux,!appengine netbsd openbsd
+
+package wrappedreadline
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// getWidth impl for Unix
+func getWidth() int {
+	w := getWidthFd(StdoutFd)
+	if w < 0 {
+		w = getWidthFd(StderrFd)
+	}
+
+	return w
+}
+
+type winsize struct {
+	Row    uint16
+	Col    uint16
+	Xpixel uint16
+	Ypixel uint16
+}
+
+// get width of the terminal
+func getWidthFd(stdoutFd int) int {
+	ws := &winsize{}
+	retCode, _, errno := syscall.Syscall(syscall.SYS_IOCTL,
+		uintptr(stdoutFd),
+		uintptr(syscall.TIOCGWINSZ),
+		uintptr(unsafe.Pointer(ws)))
+
+	if int(retCode) == -1 {
+		_ = errno
+		return -1
+	}
+
+	return int(ws.Col)
+}

helper/wrappedreadline/wrappedreadline_windows.go

@@ -0,0 +1,8 @@
+// +build windows
+
+package wrappedreadline
+
+// getWidth impl for other
+func getWidth() int {
+	return 0
+}