| 🛟 Updated. 28d5985 k33g 17h ago | 1 | //go:build windows |
| 2 | |
| 3 | package terminal |
| 4 | |
| 5 | import ( |
| 6 | "fmt" |
| 7 | "os" |
| 8 | "sync" |
| 9 | "unsafe" |
| 10 | |
| 11 | "golang.org/x/sys/windows" |
| 12 | ) |
| 13 | |
| 14 | // windowsChild is a shell behind a Windows pseudo-console. |
| 15 | // |
| 16 | // A pseudo-console is not a device this process can read and write: it is an |
| 17 | // object owned by conhost.exe, wired to two pipes of ours. What the shell |
| 18 | // prints arrives on the output pipe as the same VT sequences a Unix shell |
| 19 | // writes to a pty, which is the whole reason the emulator on this side needs |
| 20 | // no Windows code at all; what we write to the input pipe reaches the shell |
| 21 | // as keystrokes. |
| 22 | // |
| 23 | // Go's exec cannot start a process attached to a pseudo-console — the |
| 24 | // attribute has to go through an extended STARTUPINFO — so the process is |
| 25 | // created with CreateProcess directly and waited for with a handle. |
| 26 | type windowsChild struct { |
| 27 | console windows.Handle |
| 28 | process windows.Handle |
| 29 | input *os.File // our end of the shell's standard input |
| 30 | output *os.File // our end of the shell's standard output and error |
| 31 | program string |
| 32 | |
| 33 | closeConsole sync.Once |
| 34 | closeOnce sync.Once |
| 35 | closeErr error |
| 36 | } |
| 37 | |
| 38 | // updateProcThreadAttribute is called by hand rather than through x/sys, |
| 39 | // because the pseudo-console attribute's value is the handle *itself*, and |
| 40 | // x/sys's wrapper takes an unsafe.Pointer — which would mean converting a |
| 41 | // handle to one, the very conversion `go vet` exists to flag. |
| 42 | var updateProcThreadAttribute = windows.NewLazySystemDLL("kernel32.dll").NewProc("UpdateProcThreadAttribute") |
| 43 | |
| 44 | // startChild creates a pseudo-console and starts the shell attached to it. |
| 45 | func startChild(options Options) (child, error) { |
| 46 | var inputRead, inputWrite, outputRead, outputWrite windows.Handle |
| 47 | if err := windows.CreatePipe(&inputRead, &inputWrite, nil, 0); err != nil { |
| 48 | return nil, fmt.Errorf("terminal: creating the input pipe: %w", err) |
| 49 | } |
| 50 | if err := windows.CreatePipe(&outputRead, &outputWrite, nil, 0); err != nil { |
| 51 | closeHandles(inputRead, inputWrite) |
| 52 | return nil, fmt.Errorf("terminal: creating the output pipe: %w", err) |
| 53 | } |
| 54 | |
| 55 | var console windows.Handle |
| 56 | size := coord(options.Width, options.Height) |
| 57 | if err := windows.CreatePseudoConsole(size, inputRead, outputWrite, 0, &console); err != nil { |
| 58 | closeHandles(inputRead, inputWrite, outputRead, outputWrite) |
| 59 | return nil, fmt.Errorf("terminal: creating the pseudo-console: %w", err) |
| 60 | } |
| 61 | // The console has duplicated the two ends it uses; ours are the other two. |
| 62 | closeHandles(inputRead, outputWrite) |
| 63 | |
| 64 | program := shellOrDefault(options.Shell) |
| 65 | process, err := createProcess(console, program, options) |
| 66 | if err != nil { |
| 67 | windows.ClosePseudoConsole(console) |
| 68 | closeHandles(inputWrite, outputRead) |
| 69 | return nil, err |
| 70 | } |
| 71 | |
| 72 | c := &windowsChild{ |
| 73 | console: console, |
| 74 | process: process, |
| 75 | input: os.NewFile(uintptr(inputWrite), "pseudo-console input"), |
| 76 | output: os.NewFile(uintptr(outputRead), "pseudo-console output"), |
| 77 | program: program, |
| 78 | } |
| 79 | // conhost keeps the output pipe open for as long as the console exists, |
| 80 | // whether or not the shell is still running. Without this, a shell that |
| 81 | // exited would never give the reader its EOF, and a command run in a |
| 82 | // window would never be seen to finish. |
| 83 | go c.closeConsoleWhenTheShellExits() |
| 84 | return c, nil |
| 85 | } |
| 86 | |
| 87 | // createProcess starts the shell attached to the pseudo-console. |
| 88 | func createProcess(console windows.Handle, program string, options Options) (windows.Handle, error) { |
| 89 | attributes, err := pseudoConsoleAttributes(console) |
| 90 | if err != nil { |
| 91 | return 0, err |
| 92 | } |
| 93 | defer attributes.Delete() |
| 94 | |
| 95 | commandLine, directory, err := encodedArguments(program, options) |
| 96 | if err != nil { |
| 97 | return 0, err |
| 98 | } |
| 99 | block := environmentBlock(environment(options.Env)) |
| 100 | |
| 101 | startup := windows.StartupInfoEx{ProcThreadAttributeList: attributes.List()} |
| 102 | startup.Cb = uint32(unsafe.Sizeof(startup)) |
| 103 | var info windows.ProcessInformation |
| 104 | |
| 105 | flags := uint32(windows.EXTENDED_STARTUPINFO_PRESENT | windows.CREATE_UNICODE_ENVIRONMENT) |
| 106 | if err := windows.CreateProcess(nil, commandLine, nil, nil, false, flags, &block[0], directory, &startup.StartupInfo, &info); err != nil { |
| 107 | return 0, fmt.Errorf("terminal: starting %s: %w", program, err) |
| 108 | } |
| 109 | windows.CloseHandle(info.Thread) |
| 110 | return info.Process, nil |
| 111 | } |
| 112 | |
| 113 | // pseudoConsoleAttributes builds the one process attribute that attaches the |
| 114 | // child to the console. The caller deletes it once the process has started. |
| 115 | func pseudoConsoleAttributes(console windows.Handle) (*windows.ProcThreadAttributeListContainer, error) { |
| 116 | attributes, err := windows.NewProcThreadAttributeList(1) |
| 117 | if err != nil { |
| 118 | return nil, fmt.Errorf("terminal: preparing the process attributes: %w", err) |
| 119 | } |
| 120 | |
| 121 | // The attribute's value is the console handle itself, sizeof(HPCON) wide. |
| 122 | if ret, _, err := updateProcThreadAttribute.Call( |
| 123 | uintptr(unsafe.Pointer(attributes.List())), 0, windows.PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE, |
| 124 | uintptr(console), unsafe.Sizeof(console), 0, 0, |
| 125 | ); ret == 0 { |
| 126 | attributes.Delete() |
| 127 | return nil, fmt.Errorf("terminal: attaching the pseudo-console: %w", err) |
| 128 | } |
| 129 | return attributes, nil |
| 130 | } |
| 131 | |
| 132 | // encodedArguments returns the command line and the working directory as the |
| 133 | // UTF-16 strings CreateProcess reads; a nil directory means the current one. |
| 134 | func encodedArguments(program string, options Options) (commandLine, directory *uint16, err error) { |
| 135 | commandLine, err = windows.UTF16PtrFromString(windowsCommandLine(program, options.Args)) |
| 136 | if err != nil { |
| 137 | return nil, nil, fmt.Errorf("terminal: encoding the command line: %w", err) |
| 138 | } |
| 139 | if options.Dir == "" { |
| 140 | return commandLine, nil, nil |
| 141 | } |
| 142 | directory, err = windows.UTF16PtrFromString(options.Dir) |
| 143 | if err != nil { |
| 144 | return nil, nil, fmt.Errorf("terminal: encoding the directory: %w", err) |
| 145 | } |
| 146 | return commandLine, directory, nil |
| 147 | } |
| 148 | |
| 149 | // closeConsoleWhenTheShellExits waits for the process and then closes the |
| 150 | // pseudo-console, which is what makes conhost close its end of the output pipe |
| 151 | // and the reader see io.EOF. |
| 152 | func (c *windowsChild) closeConsoleWhenTheShellExits() { |
| 153 | _, _ = windows.WaitForSingleObject(c.process, windows.INFINITE) |
| 154 | c.closeConsole.Do(func() { windows.ClosePseudoConsole(c.console) }) |
| 155 | } |
| 156 | |
| 157 | // coord is a terminal size in the shape ResizePseudoConsole wants. |
| 158 | func coord(width, height int) windows.Coord { |
| 159 | return windows.Coord{X: int16(max(width, 1)), Y: int16(max(height, 1))} |
| 160 | } |
| 161 | |
| 162 | // closeHandles closes what it is given, ignoring handles that are already zero. |
| 163 | func closeHandles(handles ...windows.Handle) { |
| 164 | for _, handle := range handles { |
| 165 | if handle != 0 { |
| 166 | windows.CloseHandle(handle) |
| 167 | } |
| 168 | } |
| 169 | } |
| 170 | |
| 171 | // defaultShell returns the shell Windows names as the user's: %COMSPEC%, |
| 172 | // which is cmd.exe. There is no $SHELL on Windows. |
| 173 | func defaultShell() string { return windowsShell(os.Getenv("COMSPEC")) } |
| 174 | |
| 175 | func (c *windowsChild) Read(b []byte) (int, error) { return c.output.Read(b) } |
| 176 | func (c *windowsChild) Write(b []byte) (int, error) { return c.input.Write(b) } |
| 177 | |
| 178 | // Resize tells conhost the console has changed size; it passes that on to the |
| 179 | // shell as a window-size event, which is what a full-screen program repaints |
| 180 | // on. |
| 181 | func (c *windowsChild) Resize(width, height int) error { |
| 182 | return windows.ResizePseudoConsole(c.console, coord(width, height)) |
| 183 | } |
| 184 | |
| 185 | // Close ends the shell, the console and the pipes, in that order. |
| 186 | // |
| 187 | // The process goes first, so that closing the console does not wait on a |
| 188 | // shell that ignores the end of its input; the console second, which is what |
| 189 | // gives the reading goroutine its EOF; the pipes last. Closing twice is safe, |
| 190 | // because the view closes the session and the waiter may already have closed |
| 191 | // the console. |
| 192 | func (c *windowsChild) Close() error { |
| 193 | c.closeOnce.Do(func() { |
| 194 | _ = windows.TerminateProcess(c.process, 1) |
| 195 | _, _ = windows.WaitForSingleObject(c.process, 5000) |
| 196 | c.closeConsole.Do(func() { windows.ClosePseudoConsole(c.console) }) |
| 197 | c.closeErr = c.input.Close() |
| 198 | _ = c.output.Close() |
| 199 | windows.CloseHandle(c.process) |
| 200 | }) |
| 201 | return c.closeErr |
| 202 | } |
| 203 | |
| 204 | // Command returns the shell's name without its path. |
| 205 | func (c *windowsChild) Command() string { return programName(c.program) } |