readline windows terminal support (#950)

- update the readline package to have basic support on windows, this is not full feature parity with the unix cli yet

readline/term_windows.go

@@ -0,0 +1,62 @@
+package readline
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const (
+	enableLineInput       = 2
+	enableWindowInput     = 8
+	enableMouseInput      = 16
+	enableInsertMode      = 32
+	enableQuickEditMode   = 64
+	enableExtendedFlags   = 128
+	enableProcessedOutput = 1
+	enableWrapAtEolOutput = 2
+	enableAutoPosition    = 256 // Cursor position is not affected by writing data to the console.
+	enableEchoInput       = 4   // Characters are written to the console as they're read.
+	enableProcessedInput  = 1   // Enables input processing (like recognizing Ctrl+C).
+)
+
+var kernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+var (
+	procGetConsoleMode = kernel32.NewProc("GetConsoleMode")
+	procSetConsoleMode = kernel32.NewProc("SetConsoleMode")
+)
+
+type State struct {
+	mode uint32
+}
+
+// IsTerminal checks if the given file descriptor is associated with a terminal
+func IsTerminal(fd int) bool {
+	var st uint32
+	r, _, e := syscall.SyscallN(procGetConsoleMode.Addr(), uintptr(fd), uintptr(unsafe.Pointer(&st)), 0)
+	// if the call succeeds and doesn't produce an error, it's a terminal
+	return r != 0 && e == 0
+}
+
+func SetRawMode(fd int) (*State, error) {
+	var st uint32
+	// retrieve the current mode of the terminal
+	_, _, e := syscall.SyscallN(procGetConsoleMode.Addr(), uintptr(fd), uintptr(unsafe.Pointer(&st)), 0)
+	if e != 0 {
+		return nil, error(e)
+	}
+	// modify the mode to set it to raw
+	raw := st &^ (enableEchoInput | enableProcessedInput | enableLineInput | enableProcessedOutput)
+	// apply the new mode to the terminal
+	_, _, e = syscall.SyscallN(procSetConsoleMode.Addr(), uintptr(fd), uintptr(raw), 0)
+	if e != 0 {
+		return nil, error(e)
+	}
+	// return the original state so that it can be restored later
+	return &State{st}, nil
+}
+
+func UnsetRawMode(fd int, state *State) error {
+	_, _, err := syscall.SyscallN(procSetConsoleMode.Addr(), uintptr(fd), uintptr(state.mode), 0)
+	return err
+}