winapi.l.c

/***
A useful set of Windows API functions.

 * Enumerating and accessing windows, including sending keys.
 * Enumerating processes and querying their program name, memory used, etc.
 * Reading and Writing to the Registry
 * Copying and moving files, and showing drive information.
 * Launching processes and opening documents.
 * Monitoring filesystem changes.

@author Steve Donovan  (steve.j.donovan@gmail.com)
@copyright 2011
@license MIT/X11
@module winapi
*/
#define WINDOWS_LEAN_AND_MEAN
#include <windows.h>
#include <string.h>
#ifdef __GNUC__
#include <winable.h> /* GNU GCC specific */
#endif
#include "Winnetwk.h"
#include <psapi.h>


#define WBUFF 2048
#define MAX_SHOW 100
#define THREAD_STACK_SIZE (1024 * 1024)
#define MAX_PROCESSES 1024
#define MAX_KEYS 512
#define FILE_BUFF_SIZE 2048
#define MAX_WATCH 20
#define MAX_WPATH 1024

#define TIMEOUT(timeout) timeout == 0 ? INFINITE : timeout

static wchar_t wbuff[WBUFF];

typedef LPCWSTR WStr;

module "winapi" {

#include "wutils.h"

static WStr wstring(Str text) {
  return wstring_buff(text,wbuff,sizeof(wbuff));
}

/// Text encoding.
// @section encoding

/// set the current text encoding.
// @param e one of `CP_ACP` (Windows code page; default) and `CP_UTF8`
// @function set_encoding
def set_encoding (Int e) {
  set_encoding(e);
  return 0;
}

/// get the current text encoding.
// @return either `CP_ACP` or `CP_UTF8`
// @function get_encoding
def get_encoding () {
  lua_pushinteger(L, get_encoding());
  return 1;
}

/// encode a string in another encoding.
// Note: currently there's a limit of about 2K on the string buffer.
// @param e_in `CP_ACP`, `CP_UTF8` or `CP_UTF16`
// @param e_out likewise
// @param text the string
// @function encode
def encode(Int e_in, Int e_out, Str text) {
  int ce = get_encoding();
  LPCWSTR ws;
  if (e_in != -1) {
    set_encoding(e_in);
    ws = wstring(text);
  } else {
    ws = (LPCWSTR)text;
  }
  if (e_out != -1) {
    set_encoding(e_out);
    push_wstring(L,ws);
  } else {
    lua_pushlstring(L,(LPCSTR)ws,wcslen(ws)*sizeof(WCHAR));
  }
  set_encoding(ce);
  return 1;
}

/// expand # unicode escapes in a string.
// @param text ASCII text with #XXXX, where XXXX is four hex digits. ## means # itself.
// @return text as UTF-8
// @see testu.lua
// @function utf8_expand
def utf8_expand(Str text) {
  int len = strlen(text), i = 0, enc = get_encoding();
  WCHAR wch;
  LPWSTR P = wbuff;
  if (len > sizeof(wbuff)) {
    return push_error_msg(L,"string too big");
  }
  while (i <= len) {
    if (text[i] == '#') {
      ++i;
      if (text[i] == '#') {
        wch = '#';
      } else
      if (len-i >= 4) {
        char hexnum[5];
        strncpy(hexnum,text+i,4);
        hexnum[4] = '\0';
        wch = strtol(hexnum,NULL,16);
        i += 3;
      } else {
        return push_error_msg(L,"bad # escape");
      }
    } else {
      wch = (WCHAR)text[i];
    }
    *P++ = wch;
    ++i;
  }
  *P++ = 0;
  set_encoding(CP_UTF8);
  push_wstring(L,wbuff);
  set_encoding(enc);
  return 1;
}

// forward reference to Process constructor
static int push_new_Process(lua_State *L,Int pid, HANDLE ph);

/// a class representing a Window.
// @type Window
class Window {
  HWND hwnd;

  constructor (HWND h) {
    this->hwnd = h;
  }

  static lua_State *sL;

  static BOOL CALLBACK enum_callback(HWND hwnd,LPARAM data) {
    push_ref(sL,(Ref)data);
    push_new_Window(sL,hwnd);
    lua_call(sL,1,0);
    return TRUE;
  }

  /// the handle of this window.
  // @function get_handle
  def get_handle() {
    lua_pushnumber(L,(DWORD_PTR)this->hwnd);
    return 1;
  }

  /// get the window text.
  // @function get_text
  def get_text() {
    GetWindowTextW(this->hwnd,wbuff,sizeof(wbuff));
    return push_wstring(L,wbuff);
  }

  /// set the window text.
  // @function set_text
  def set_text(Str text) {
    SetWindowTextW(this->hwnd,wstring(text));
    return 0;
  }

  /// change the visibility, state etc
  // @param flags one of `SW_SHOW`, `SW_MAXIMIZE`, etc
  // @function show
  def show(Int flags = SW_SHOW) {
    ShowWindow(this->hwnd,flags);
    return 0;
  }

  /// get the position in pixels
  // @return left position
  // @return top position
  // @function get_position
  def get_position() {
    RECT rect;
    GetWindowRect(this->hwnd,&rect);
    lua_pushinteger(L,rect.left);
    lua_pushinteger(L,rect.top);
    return 2;
  }

  /// get the bounds in pixels
  // @return width
  // @return height
  // @function get_bounds
  def get_bounds() {
    RECT rect;
    GetWindowRect(this->hwnd,&rect);
    lua_pushinteger(L,rect.right - rect.left);
    lua_pushinteger(L,rect.bottom - rect.top);
    return 2;
  }

  /// is this window visible?
  // @function is_visible
  def is_visible() {
    lua_pushboolean(L,IsWindowVisible(this->hwnd));
    return 1;
  }

  /// destroy this window.
  // @function destroy
  def destroy () {
    DestroyWindow(this->hwnd);
    return 0;
  }

  /// resize this window.
  // @param x0 left
  // @param y0 top
  // @param w width
  // @param h height
  // @function resize
  def resize(Int x0, Int y0, Int w, Int h) {
    MoveWindow(this->hwnd,x0,y0,w,h,TRUE);
    return 0;
  }

  /// send a message.
  // @param msg the message
  // @param wparam
  // @param lparam
  // @return the result
  // @function send_message
  def send_message(Int msg, Number wparam, Number lparam) {
    lua_pushinteger(L,SendMessage(this->hwnd,msg,(WPARAM)wparam,(LPARAM)lparam));
    return 1;
  }

  /// enumerate all child windows.
  // @param a callback which to receive each window object
  // @function enum_children
  def enum_children(Value callback) {
    Ref ref;
    sL = L;
    ref = make_ref(L,callback);
    EnumChildWindows(this->hwnd,&enum_callback,ref);
    release_ref(L,ref);
    return 0;
  }

  /// get the parent window.
  // @function get_parent
  def get_parent() {
    return push_new_Window(L,GetParent(this->hwnd));
  }

  /// get the name of the program owning this window.
  // @function get_module_filename
  def get_module_filename() {
    int sz = GetWindowModuleFileNameW(this->hwnd,wbuff,sizeof(wbuff));
    wbuff[sz] = 0;
    return push_wstring(L,wbuff);
  }

  /// get the window class name.
  // Useful to find all instances of a running program, when you
  // know the class of the top level window.
  // @function get_class_name
  def get_class_name() {
    static char buff[1024];
    int n = GetClassName(this->hwnd,buff,sizeof(buff));
    if (n > 0) {
      lua_pushstring(L,buff);
      return 1;
    } else {
      return push_error(L);
    }
  }

  /// bring this window to the foreground.
  // @function set_foreground
  def set_foreground () {
    lua_pushboolean(L,SetForegroundWindow(this->hwnd));
    return 1;
  }

  /// get the associated process of this window
  // @function get_process
  def get_process() {
    DWORD pid;
    DWORD res = GetWindowThreadProcessId(this->hwnd,&pid);
    return push_new_Process(L,pid,NULL);
  }

  /// this window as string (up to 100 chars).
  // @function __tostring
  def __tostring() {
    int ret;
    int sz = GetWindowTextW(this->hwnd,wbuff,sizeof(wbuff));
    if (sz > MAX_SHOW) {
      wbuff[MAX_SHOW] = '\0';
    }
    ret = push_wstring(L,wbuff);
    if (ret == 2) { // we had a conversion error
      lua_pushliteral(L,"");
    }
    return 1;
  }

  def __eq(Window other) {
    lua_pushboolean(L,this->hwnd == other->hwnd);
    return 1;
  }

}

/// Manipulating Windows.
// @section Windows

/// find a window based on classname and caption
// @param cname class name (may be nil)
// @param wname caption (may be nil)
// @return @{Window}
// @function find_window
def find_window(StrNil cname, StrNil wname) {
  HWND hwnd;
  hwnd = FindWindow(cname,wname);
  return push_new_Window(L,hwnd);
}

/// makes a function that matches against window text
// @param text
// @function make_name_matcher

/// makes a function that matches against window class name
// @param text
// @function make_class_matcher

/// find a window using a condition function.
// @param match will return true when its argument is the desired window
// @return @{Window}
// @function find_window_ex

/// return all windows matching a condition.
// @param match will return true when its argument is the desired window
// @return a list of window objects
// @function find_all_windows

/// find a window matching the given text.
// @param text the pattern to match against the caption
// @return a window object.
// @function find_window_match

/// current foreground window.
// An example of setting the caption is @{caption.lua}
// @return @{Window}
// @function get_foreground_window
def get_foreground_window() {
  return push_new_Window(L, GetForegroundWindow());
}

/// the desktop window.
// @usage winapi.get_desktop_window():get_bounds()
// @return @{Window}
// @function get_desktop_window
def get_desktop_window() {
  return push_new_Window(L, GetDesktopWindow());
}

/// enumerate over all top-level windows.
// @param callback a function to receive each window object
// @function enum_windows
def enum_windows(Value callback) {
  Ref ref;
  sL = L;
  ref  = make_ref(L,callback);
  EnumWindows(&enum_callback,ref);
  release_ref(L,ref);
  return 0;
}

/// route callback dispatch through a message window.
// You need to do this when using Winapi in a GUI application,
// since it ensures that Lua callbacks happen in the GUI thread.
// @function use_gui
def use_gui() {
  make_message_window();
  return 0;
}

static INPUT *add_input(INPUT *pi, WORD vkey, BOOL up) {
  pi->type = INPUT_KEYBOARD;
  pi->ki.dwFlags =  up ? KEYEVENTF_KEYUP : 0;
  pi->ki.wVk = vkey;
  return pi+1;
}

// The Windows SendInput() is a low-level function, and you have to
// simulate things like uppercase directly. Repeated characters need
// an explicit 'key up' keystroke to work.
// see http://stackoverflow.com/questions/2167156/sendinput-isnt-sending-the-correct-shifted-characters
// this is a case where we have to convert the parameter directly, since
// it may be an integer (virtual key code) or string of characters.

/// send a string or virtual key to the active window.
// @{input.lua} shows launching a process, waiting for it to be
// ready, and sending it some keys
// @param text either a key (like winapi.VK_SHIFT) or a string
// @return number of keys sent, or nil if an error
// @return any error string
// @function send_to_window
def send_to_window () {
  const char *text;
  int vkey, len = MAX_KEYS;
  UINT res;
  SHORT last_vk = 0;
  INPUT *input, *pi;
  if (lua_isnumber(L,1)) {
    INPUT inp;
    ZeroMemory(&inp,sizeof(INPUT));
    vkey = lua_tointeger(L,1);
    add_input(&inp,vkey,lua_toboolean(L,2));
    SendInput(1,&inp,sizeof(INPUT));
    return 0;
  } else {
    text = lua_tostring(L,1);
    if (text == NULL) {
      return push_error_msg(L,"not a string or number");
    }
  }
  input = (INPUT *)malloc(sizeof(INPUT)*len);
  pi = input;
  ZeroMemory(input, sizeof(INPUT)*len);
  for(; *text; ++text) {
    SHORT vk = VkKeyScan(*text);
    if (last_vk == vk) {
      pi = add_input(pi,last_vk & 0xFF,TRUE);
    }
    if (vk & 0x100) pi = add_input(pi,VK_SHIFT,FALSE);
    pi = add_input(pi,vk & 0xFF,FALSE);
    if (vk & 0x100) pi = add_input(pi,VK_SHIFT,TRUE);
    last_vk = vk;
  }
  res = SendInput(((DWORD_PTR)pi-(DWORD_PTR)input)/sizeof(INPUT), input, sizeof(INPUT));
  free(input);
  if (res > 0) {
    lua_pushinteger(L,res);
    return 1;
  } else {
    return push_error(L);
  }
  return 0;
}

/// tile a group of windows.
// @param parent @{Window} (can use the desktop)
// @param horiz tile vertically by default
// @param kids a table of window objects
// @param bounds a bounds table (left,top,right,bottom) - can be nil
// @function tile_windows
def tile_windows(Window parent, Boolean horiz, Value kids, Value bounds) {
  RECT rt;
  HWND *kids_arr;
  int i,n_kids;
  LPRECT lpRect = NULL;
  if (! lua_isnoneornil(L,bounds)) {
    lua_pushvalue(L,bounds);
    Int_get(rt.left,"left");
    Int_get(rt.top,"top");
    Int_get(rt.right,"right");
    Int_get(rt.bottom,"bottom");
    lua_pop(L,1);
    lpRect = &rt;
  }
  n_kids = lua_objlen(L,kids);
  kids_arr = (HWND *)malloc(sizeof(HWND)*n_kids);
  for (i = 0; i < n_kids; ++i) {
    Window *w;
    lua_rawgeti(L,kids,i+1);
    w = Window_arg(L,-1);
    kids_arr[i] = w->hwnd;
  }
  TileWindows(parent->hwnd,horiz ? MDITILE_HORIZONTAL : MDITILE_VERTICAL, lpRect, n_kids, kids_arr);
  free(kids_arr);
  return 0;
}

/// Miscellaneous functions.
// @section miscellaneous

/// sleep and use no processing time.
// @param millisec sleep period
// @function sleep
def sleep(Int millisec,Boolean lock) {
  if (lock) {
    release_mutex();
  }
  Sleep(millisec);
  if (lock) {
    lock_mutex();
  }
  return 0;
}

def locked_eval(Value fn, Value arg) {
  release_mutex();
  lock_mutex();
  lua_pushvalue(L,fn);
  lua_pushvalue(L,arg);
  lua_pcall(L,1,1,0);
  lua_pushvalue(L,-1);
  return 1;
}

/// show a message box.
// @param caption for dialog
// @param msg the message
// @param btns (default 'ok') one of 'ok','ok-cancel','yes','yes-no',
// "abort-retry-ignore", "retry-cancel", "yes-no-cancel"
// @param icon (default 'information') one of 'information','question','warning','error'
// @return a string giving the pressed button: one of 'ok','yes','no','cancel',
// 'try','abort' and 'retry'
// @see message.lua
// @function show_message
def show_message(Str caption, Str msg, Str btns = "ok", Str icon = "information") {
  int res, type;
  WCHAR capb [512];
  type = mb_const(btns) | mb_const(icon);
  wstring_buff(caption,capb,sizeof(capb));
  res = MessageBoxW( NULL, wstring(msg), capb, type);
  lua_pushstring(L,mb_result(res));
  return 1;
}

/// make a beep sound.
// @param type (default 'ok'); one of 'information','question','warning','error'
// @function beep
def beep (Str icon = "ok") {
  return push_bool(L, MessageBeep(mb_const(icon)));
}

/// copy a file.
// @param src source file
// @param dest destination file
// @param fail_if_exists if true, then cannot copy onto existing file
// @function copy_file
def copy_file(Str src, Str dest, Int fail_if_exists = 0) {
  return push_bool(L, CopyFile(src,dest,fail_if_exists));
}

/// output text to the system debugger.
// A uility such as [DebugView](http://technet.microsoft.com/en-us/sysinternals/bb896647)
// can show the output
// @param str text
// @function output_debug_string
def output_debug_string(Str str) {
   OutputDebugString(str);
   return 0;
}

/// move a file.
// @param src source file
// @param dest destination file
// @function move_file
def move_file(Str src, Str dest) {
  return push_bool(L, MoveFile(src,dest));
}

#define wconv(name) (name ? wstring_buff(name,w##name,sizeof(w##name)) : NULL)

/// execute a shell command.
// @param verb the action (e.g. 'open' or 'edit') can be nil.
// @param file the command
// @param parms any parameters (optional)
// @param dir the working directory (optional)
// @param show the window show flags (default is SW_SHOWNORMAL)
// @function shell_exec
def shell_exec(StrNil verb, Str file, StrNil parms, StrNil dir, Int show=SW_SHOWNORMAL) {
  WCHAR wverb[128], wfile[MAX_WPATH], wdir[MAX_WPATH], wparms[MAX_WPATH];
  int res = (DWORD_PTR)ShellExecuteW(NULL,wconv(verb),wconv(file),wconv(parms),wconv(dir),show) > 32;
  return push_bool(L, res);
}

/// copy text onto the clipboard.
// @param text the text
// @function set_clipboard
def set_clipboard(Str text) {
  HGLOBAL glob;
  LPWSTR p;
  int bufsize = 3*strlen(text);
  if (! OpenClipboard(NULL)) {
    return push_error(L);
  }
  EmptyClipboard();
  glob = GlobalAlloc(GMEM_MOVEABLE, bufsize);
  p = (LPWSTR)GlobalLock(glob);
  wstring_buff(text,p,bufsize);
  GlobalUnlock(glob);
  if (SetClipboardData(CF_UNICODETEXT,glob) == NULL) {
    CloseClipboard();
    return push_error(L);
  }
  CloseClipboard();
  return 0;
}

/// get the text on the clipboard.
// @return the text
// @function get_clipboard
def get_clipboard() {
  HGLOBAL glob;
  LPCWSTR p;
  if (! OpenClipboard(NULL)) {
    return push_error(L);
  }
  glob = GetClipboardData(CF_UNICODETEXT);
  if (glob == NULL) {
    CloseClipboard();
    return push_error(L);
  }
  p = GlobalLock(glob);
  push_wstring(L,p);
  GlobalUnlock(glob);
  CloseClipboard();
  return 1;
}

/// A class representing a Windows process.
// this example was [helpful](http://msdn.microsoft.com/en-us/library/ms682623%28VS.85%29.aspx)
// @type Process
class Process {
  HANDLE hProcess;
  int pid;

  constructor(Int pid, HANDLE ph) {
    if (ph) {
      this->pid = pid;
      this->hProcess = ph;
    } else {
      this->pid = pid;
      this->hProcess = OpenProcess(PROCESS_QUERY_INFORMATION |
                                  PROCESS_VM_READ,
                                  FALSE, pid );
      }
  }

  /// get the name of the process.
  // @param full true if you want the full path; otherwise returns the base name.
  // @function get_process_name
  def get_process_name(Boolean full) {
    HMODULE hMod;
    DWORD cbNeeded;
    wchar_t modname[MAX_PATH];

    if (EnumProcessModules(this->hProcess, &hMod, sizeof(hMod), &cbNeeded)) {
      if (full) {
        GetModuleFileNameExW(this->hProcess, hMod, modname, sizeof(modname));
      } else {
        GetModuleBaseNameW(this->hProcess, hMod, modname, sizeof(modname));
      }
      return push_wstring(L,modname);
    } else {
      return push_error(L);
    }
  }
  
  /// get the the pid of the process.
  // @function get_pid
  def get_pid() {
    lua_pushnumber(L, this->pid);
	return 1;
  }

  /// kill the process.
  // @{test-spawn.lua} kills a launched process after a certain amount of output.
  // @function kill
  def kill() {
    TerminateProcess(this->hProcess,0);
    return 0;
  }

  /// get the working size of the process.
  // @return minimum working set size
  // @return maximum working set size.
  // @function get_working_size
  def get_working_size() {
    SIZE_T minsize, maxsize;
    GetProcessWorkingSetSize(this->hProcess,&minsize,&maxsize);
    lua_pushnumber(L,minsize/1024);
    lua_pushnumber(L,maxsize/1024);
    return 2;
  }

  /// get the start time of this process.
  // @return a table in the same format as os.time() and os.date() expects.
  // @function get_start_time
  def get_start_time() {
    FILETIME create,exit,kernel,user,local;
    SYSTEMTIME time;
    GetProcessTimes(this->hProcess,&create,&exit,&kernel,&user);
    FileTimeToLocalFileTime(&create,&local);
    FileTimeToSystemTime(&local,&time);
    #define set(name,val) lua_pushinteger(L,val); lua_setfield(L,-2,#name);
    lua_newtable(L);
    set(year,time.wYear);
    set(month,time.wMonth);
    set(day,time.wDay);
    set(hour,time.wHour);
    set(min,time.wMinute);
    set(sec,time.wSecond);
    #undef set
    return 1;
  }

  // MS likes to be different: the 64-bit value encoded in FILETIME
  // is defined as the number of 100-nsec intervals since Jan 1, 1601 UTC
  static double fileTimeToMillisec(FILETIME *ft) {
    ULARGE_INTEGER ui;
    ui.LowPart = ft->dwLowDateTime;
    ui.HighPart = ft->dwHighDateTime;
    return (double) (ui.QuadPart/10000);
  }

  /// elapsed run time of this process.
  // @return user time in msec
  // @return system time in msec
  // @function get_run_times
  def get_run_times() {
    FILETIME create,exit,kernel,user;
    GetProcessTimes(this->hProcess,&create,&exit,&kernel,&user);
    lua_pushnumber(L,fileTimeToMillisec(&user));
    lua_pushnumber(L,fileTimeToMillisec(&kernel));
    return 2;
  }

  static int push_wait_result(lua_State *L, DWORD res) {
    if (res == WAIT_OBJECT_0) {
        lua_pushvalue(L,1);
        lua_pushliteral(L,"OK");
        return 2;
    } else if (res == WAIT_TIMEOUT) {
        lua_pushvalue(L,1);
        lua_pushliteral(L,"TIMEOUT");
        return 2;
    } else {
        return push_error(L);
    }
  }

  /// wait for this process to finish.
  // @param timeout optional timeout in millisec; defaults to waiting indefinitely.
  // @return this process object
  // @return either "OK" or "TIMEOUT"
  // @function wait
  def wait(Int timeout = 0) {
    return push_wait_result(L, WaitForSingleObject(this->hProcess, TIMEOUT(timeout)));
  }

  /// wait for this process to become idle and ready for input.
  // Only makes sense for processes with windows (will return immediately if not)
  // @param timeout optional timeout in millisec
  // @return this process object
  // @return either "OK" or "TIMEOUT"
  // @function wait_for_input_idle
  def wait_for_input_idle (Int timeout = 0) {
    return push_wait_result(L, WaitForInputIdle(this->hProcess, TIMEOUT(timeout)));
  }

  /// exit code of this process.
  // (Only makes sense if the process has in fact finished.)
  // @return exit code
  // @function get_exit_code
  def get_exit_code() {
    DWORD code;
    GetExitCodeProcess(this->hProcess, &code);
    lua_pushinteger(L,code);
    return 1;
  }

  /// close this process handle.
  // @function close
  def close() {
    CloseHandle(this->hProcess);
    this->hProcess = NULL;
    return 0;
  }

  def __gc () {
    if (this->hProcess != NULL)
      CloseHandle(this->hProcess);
    return 0;
  }
}

/// Working with processes.
// @section Processes

/// create a process object from the id.
// @param pid the process id
// @return @{Process}
// @function process_from_id
def process_from_id(Int pid) {
  return push_new_Process(L,pid,NULL);
}

/// process id of current process.
// @return integer id
// @function get_current_pid
def get_current_pid() {
  lua_pushinteger(L,GetCurrentProcessId());
  return 1;
}

/// process object of the current process.
// @return @{Process}
// @function get_current_process
def get_current_process() {
  return push_new_Process(L,0,GetCurrentProcess());
}

/// get all process ids in the system.
// @{test-processes.lua} is a simple `ps` equivalent.
// @return an array of process ids.
// @function get_processes
def get_processes() {
  DWORD processes[MAX_PROCESSES], cbNeeded, nProcess;
  int i, k = 1;

  if (! EnumProcesses (processes,sizeof(processes),&cbNeeded)) {
    return push_error(L);
  }

  nProcess = cbNeeded/sizeof (DWORD);
  lua_newtable(L);
  for (i = 0; i < nProcess; i++) {
    if (processes[i] != 0) {
      lua_pushinteger(L,processes[i]);
      lua_rawseti(L,-2,k++);
    }
  }
  return 1;
}

/// wait for a group of processes.
// @{process-wait.lua} shows a number of processes launched
// in parallel
// @param processes an array of @{Process} objects
// @param all wait for all processes to finish (default false)
// @param timeout wait upto this time in msec (default infinite)
// @function wait_for_processes
def wait_for_processes(Value processes, Boolean all, Int timeout = 0) {
  int status, i;
  Process *p;
  int n = lua_objlen(L,processes);
  HANDLE handles[MAXIMUM_WAIT_OBJECTS];
  if (n > MAXIMUM_WAIT_OBJECTS) {
    return push_error_msg(L,"cannot wait on so many processes");
  }
  for (i = 0; i < n; i++) {
    lua_rawgeti(L,processes,i+1);
    p = Process_arg(L,-1);
    handles[i] = p->hProcess;
  }
  status = WaitForMultipleObjects(n, handles, all, TIMEOUT(timeout));
  status -= WAIT_OBJECT_0 + 1;
  if (status < 1 || status > n) {
    return push_error(L);
  } else {
    lua_pushinteger(L,status);
    return 1;
  }
}

// These functions are all run in background threads, and a little bit of poor man's
// OOP helps here. This is the base struct for describing threads with callbacks,
// which may have an associated buffer and handle.

#define callback_data_ \
  lua_State *L; \
  Ref callback; \
  char *buf; \
  int bufsz; \
  HANDLE handle;

typedef struct {
  callback_data_
} LuaCallback, *PLuaCallback;

void lcb_callback(void *lcb, lua_State *L, int idx) {
  LuaCallback *data = (LuaCallback*) lcb;
  data->L = L;
  data->callback = make_ref(L,idx);
  data->buf = NULL;
  data->handle = NULL;
}

BOOL lcb_call(void *data, int idx, Str text, int persist) {
  LuaCallback *lcb = (LuaCallback*)data;
  return call_lua(lcb->L,lcb->callback,idx,text,persist);
}

void lcb_allocate_buffer(void *data, int size) {
  LuaCallback *lcb = (LuaCallback*)data;
  lcb->buf = malloc(size);
  lcb->bufsz = size;
}

void lcb_free(void *data) {
  LuaCallback *lcb = (LuaCallback*)data;
  if (! lcb) return;
  if (lcb->buf) {
    free(lcb->buf);
    lcb->buf = NULL;
  }
  if (lcb->handle) {
    CloseHandle(lcb->handle);
    lcb->handle = NULL;
  }
  release_ref(lcb->L,lcb->callback);
}

/// Thread object. This is returned by the @{File:read_async} method and the @{make_timer},
// @{make_pipe_server} and @{watch_for_file_changes} functions. Useful to kill a thread
// and free associated resources.
// @type Thread
class Thread {
  LuaCallback *lcb;
  HANDLE thread;

  constructor (PLuaCallback lcb, HANDLE thread) {
    this->lcb = lcb;
    this->thread = thread;
  }

  /// suspend this thread.
  // @function suspend
  def suspend() {
    return push_bool(L, SuspendThread(this->thread) >= 0);
  }

  /// resume a suspended thread.
  // @function resume
  def resume() {
    return push_bool(L, ResumeThread(this->thread) >= 0);
  }

  /// kill this thread. Generally considered a 'nuclear' option, but
  // this implementation will free any associated callback references, buffers
  // and handles. @{test-timer.lua} shows how a timer can be terminated.
  // @function kill
  def kill() {
    lcb_free(this->lcb);
    return push_bool(L, TerminateThread(this->thread,1));
  }

  /// set a thread's priority
  // @param p positive integer to increase thread priority
  // @function set_priority
  def set_priority(Int p) {
    return push_bool(L, SetThreadPriority(this->thread,p));
  }

  /// get a thread's priority
  // @function get_priority
  def get_priority() {
    int res = GetThreadPriority(this->thread);
    if (res != THREAD_PRIORITY_ERROR_RETURN) {
      lua_pushinteger(L,res);
      return 1;
    } else {
      return push_error(L);
    }
  }

  def __gc() {
    // lcb_free(this->lcb); concerned that this cd kick in prematurely!
    CloseHandle(this->thread);
    return 0;
  }
}

typedef LPTHREAD_START_ROUTINE  TCB;

int lcb_new_thread(TCB fun, void *data) {
  LuaCallback *lcb = (LuaCallback*)data;
  HANDLE thread = CreateThread(NULL,THREAD_STACK_SIZE,fun,data,0,NULL);
  return push_new_Thread(lcb->L,lcb,thread);
}

#define lcb_buf(data) ((LuaCallback *)data)->buf
#define lcb_bufsz(data) ((LuaCallback *)data)->bufsz
#define lcb_handle(data) ((LuaCallback *)data)->handle

/// this represents a raw Windows file handle.
// The write handle may be distinct from the read handle.
// @type File
class File {
  callback_data_
  HANDLE hWrite;

  constructor (HANDLE hread, HANDLE hwrite) {
    lcb_handle(this) = hread;
    this->hWrite = hwrite;
    this->L = L;
    lcb_allocate_buffer(this,FILE_BUFF_SIZE);
  }

  /// write to a file.
  // @param s text
  // @return number of bytes written.
  // @function write
  def write(Str s) {
    DWORD bytesWrote;
    WriteFile(this->hWrite, s, lua_objlen(L,2), &bytesWrote, NULL);
    lua_pushinteger(L,bytesWrote);
    return 1;
  }

  static BOOL raw_read (File *this) {
    DWORD bytesRead = 0;
    BOOL res = ReadFile(lcb_handle(this), lcb_buf(this), lcb_bufsz(this), &bytesRead, NULL);
    lcb_buf(this)[bytesRead] = '\0';
    return res && bytesRead;
  }

  /// read from a file.
  // Please note that this is not buffered, and you will have to
  // split into lines, etc yourself.
  // @return text if successful, nil plus error otherwise.
  // @function read
  def read() {
    if (raw_read(this)) {
      lua_pushstring(L,lcb_buf(this));
      return 1;
    } else {
      return push_error(L);
    }
  }

  static void file_reader (File *this) { // background reader thread
    int n;
    do {
      n = raw_read(this);
      lcb_call (this,0,lcb_buf(this),! n);
    } while (n);

  }

  /// asynchronous read.
  // @param callback function that will receive each chunk of text
  // as it comes in.
  // @return @{Thread}
  // @function read_async
  def read_async (Value callback) {
    this->callback = make_ref(L,callback);
    return lcb_new_thread((TCB)&file_reader,this);
  }

  def close() {
    if (this->hWrite != lcb_handle(this))
      CloseHandle(this->hWrite);
    lcb_free(this);
    return 0;
  }

  def __gc () {
    free(this->buf);
    return 0;
  }
}

/// Launching processes.
// @section Launch

/// set an environment variable for any child processes.
// @{setenv.lua} shows how this also affects processes
// launched with @{os.execute}
// Note that this can't affect any system environment variables, see
// [here](http://msdn.microsoft.com/en-us/library/ms682653%28VS.85%29.aspx)
// for how to set these.
// @param name name of variable
// @param value value to set
// @function setenv
def setenv(Str name, Str value) {
  WCHAR wname[256],wvalue[MAX_WPATH];
  return push_bool(L, SetEnvironmentVariableW(wconv(name),wconv(value)));
}

/// Spawn a process.
// @param program the command-line (program + parameters)
// @param dir the working directory for the process (optional)
// @return @{Process}
// @return @{File}
// @function spawn_process
def spawn_process(Str program, StrNil dir) {
  WCHAR wdir [MAX_WPATH];
  SECURITY_ATTRIBUTES sa = {sizeof(SECURITY_ATTRIBUTES), 0, 0};
  SECURITY_DESCRIPTOR sd;
  STARTUPINFOW si = {
           sizeof(STARTUPINFOW), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
       };
  HANDLE hPipeRead,hWriteSubProcess;
  HANDLE hRead2,hPipeWrite;
  BOOL running;
  PROCESS_INFORMATION pi;
  HANDLE hProcess = GetCurrentProcess();
  sa.bInheritHandle = TRUE;
  sa.lpSecurityDescriptor = NULL;
  InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
  SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE);
  sa.nLength = sizeof(SECURITY_ATTRIBUTES);
  sa.lpSecurityDescriptor = &sd;

  // Create pipe for output redirection
  CreatePipe(&hPipeRead, &hPipeWrite, &sa, 0);

  // Create pipe for input redirection. In this code, you do not
  // redirect the output of the child process, but you need a handle
  // to set the hStdInput field in the STARTUP_INFO struct. For safety,
  // you should not set the handles to an invalid handle.

  hRead2 = NULL;
  CreatePipe(&hRead2, &hWriteSubProcess, &sa, 0);

  SetHandleInformation(hPipeRead, HANDLE_FLAG_INHERIT, 0);
  SetHandleInformation(hWriteSubProcess, HANDLE_FLAG_INHERIT, 0);

  si.dwFlags = STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
  si.wShowWindow = SW_HIDE;
  si.hStdInput = hRead2;
  si.hStdOutput = hPipeWrite;
  si.hStdError = hPipeWrite;

  running = CreateProcessW(
        NULL,
        (LPWSTR)wstring(program),
        NULL, NULL,
        TRUE, CREATE_NEW_PROCESS_GROUP,
        NULL,
        wconv(dir),
        &si, &pi);

  if (running) {
    CloseHandle(pi.hThread);
    CloseHandle(hRead2);
    CloseHandle(hPipeWrite);
    push_new_Process(L,pi.dwProcessId,pi.hProcess);
    push_new_File(L,hPipeRead,hWriteSubProcess);
    return 2;
  } else {
    return push_error(L);
  }
}

/// execute a system command.
// This is like `os.execute()`, except that it works without ugly
// console flashing in Windows GUI applications. It additionally
// returns all text read from stdout and stderr.
// @param cmd a shell command (may include redirection, etc)
// @param unicode if 'unicode' force built-in commands to output in unicode;
// in this case the result is always UTF-8
// @return return code
// @return program output
// @function execute

// Timer support //////////
typedef struct {
  callback_data_
  int msec;
} TimerData;

static void timer_thread(TimerData *data) { // background timer thread
  while (1) {
    Sleep(data->msec);
    if (lcb_call(data,0,0,0))
      break;
  }
}

/// Asynchronous Timers.
// @section Timers

/// Create an asynchronous timer.
// The callback can return true if it wishes to cancel the timer.
// @{test-sleep.lua} shows how you need to call @{sleep} at the end of
// a console application for these timers to work in the background.
// @param msec interval in millisec
// @param callback a function to be called at each interval.
// @return @{Thread}
// @function make_timer
def make_timer(Int msec, Value callback) {
  TimerData *data = (TimerData *)malloc(sizeof(TimerData));
  data->msec = msec;
  lcb_callback(data,L,callback);
  return lcb_new_thread((TCB)&timer_thread,data);
}

#define PSIZE 512

typedef struct {
  callback_data_
  const char *pipename;
} PipeServerParms;

static void pipe_server_thread(PipeServerParms *parms) {
  while (1) {
    BOOL connected;
    HANDLE hPipe = CreateNamedPipe(
          parms->pipename,             // pipe named
          PIPE_ACCESS_DUPLEX,       // read/write access
          PIPE_WAIT,                // blocking mode
          255,
          PSIZE,                  // output buffer size
          PSIZE,                  // input buffer size
          0,                        // client time-out
          NULL);                    // default security attribute

    if (hPipe == INVALID_HANDLE_VALUE) {
      push_error(parms->L); // how to signal main thread about this?
    }
    // Wait for the client to connect; if it succeeds,
    // the function returns a nonzero value. If the function
    // returns zero, GetLastError returns ERROR_PIPE_CONNECTED.

    connected = ConnectNamedPipe(hPipe, NULL) ?
         TRUE : (GetLastError() == ERROR_PIPE_CONNECTED);

    if (connected) {
      push_new_File(parms->L,hPipe,hPipe);
      lcb_call(parms,-1,0,0);
    } else {
      CloseHandle(hPipe);
    }
  }
}

/// Dealing with named pipes.
// @section Pipes

/// open a pipe for reading and writing.
// @param pipename the pipename (default is "\\\\.\\pipe\\luawinapi")
// @function open_pipe
def open_pipe(Str pipename = "\\\\.\\pipe\\luawinapi") {
  HANDLE hPipe = CreateFile(
      pipename,
      GENERIC_READ |  // read and write access
      GENERIC_WRITE,
      0,              // no sharing
      NULL,           // default security attributes
      OPEN_EXISTING,  // opens existing pipe
      0,              // default attributes
      NULL);          // no template file
  if (hPipe == INVALID_HANDLE_VALUE) {
    return push_error(L);
  } else {
    return push_new_File(L,hPipe,hPipe);
  }
}

/// create a named pipe server.
// This goes into a background loop, and accepts client connections.
// For each new connection, the callback will be called with a File
// object for reading and writing to the client.
// @param callback a function that will be passed a File object
// @param pipename Must be of the form \\.\pipe\name, defaults to
// \\.\pipe\luawinapi.
// @return @{Thread}.
// @function make_pipe_server
def make_pipe_server(Value callback, Str pipename = "\\\\.\\pipe\\luawinapi") {
  PipeServerParms *psp = (PipeServerParms*)malloc(sizeof(PipeServerParms));
  lcb_callback(psp,L,callback);
  psp->pipename = pipename;
  return lcb_new_thread((TCB)&pipe_server_thread,psp);
}

// Directory change notification ///////

typedef struct {
  callback_data_
  DWORD how;
  DWORD subdirs;
} FileChangeParms;

static void file_change_thread(FileChangeParms *fc) { // background file monitor thread
  while (1) {
    int next;
    DWORD bytes;
    // This fills in some gaps:
    // http://qualapps.blogspot.com/2010/05/understanding-readdirectorychangesw_19.html
    if (! ReadDirectoryChangesW(lcb_handle(fc),lcb_buf(fc),lcb_bufsz(fc),
        fc->subdirs, fc->how, &bytes,NULL,NULL))  {
      throw_error(fc->L,"read dir changes failed");
    }
    next = 0;
    do {
      int i,sz, outchars;
      short *pfile;
      char outbuff[MAX_PATH];
      PFILE_NOTIFY_INFORMATION pni = (PFILE_NOTIFY_INFORMATION)(lcb_buf(fc)+next);
      outchars = WideCharToMultiByte(
        get_encoding(), 0,
        pni->FileName,
        pni->FileNameLength/2, // it's bytes, not number of characters!
        outbuff,sizeof(outbuff),
        NULL,NULL);
      if (outchars == 0) {
        throw_error(fc->L,"wide char conversion borked");
      }
      outbuff[outchars] = '\0';  // not null-terminated!
      lcb_call(fc,pni->Action,outbuff,0);
      next = pni->NextEntryOffset;
    } while (next != 0);
  }
}

/// Drive information and directories.
// @section Directories

/// the short path name of a directory or file.
// This is always in ASCII, 8.3 format. This function will create the
// file first if it does not exist; the result can be used to open
// files with unicode names (see @{testshort.lua})
// @param path multibyte encoded file path
// @return ASCII 8.3 format file path
// @function short_path
def short_path(Str path) {
  WCHAR wpath[MAX_WPATH];
  HANDLE hFile;
  int res;
  wconv(path);
  // if the file doesn't exist, then force its creation
  hFile = CreateFileW(wpath,
    GENERIC_WRITE,
    FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE, NULL,
    CREATE_NEW,
    FILE_ATTRIBUTE_NORMAL,
    NULL);
  if (hFile == INVALID_HANDLE_VALUE) {
    if (GetLastError() != ERROR_FILE_EXISTS) // that error is fine!
      return push_error(L);
  } else { // if we created it successfully, then close.
    CloseHandle(hFile);
  }
  res = GetShortPathNameW(wpath,wbuff,sizeof(wbuff));
  if (res > 0) {
    return push_wstring(L,wbuff);
  } else {
    return push_error(L);
  }
}

/// get a temporary filename.
// (Don't use os.tmpname)
// @return full path within temporary files directory.
// @function temp_name

/// delete a file or directory.
// @param file may be a wildcard
// @function delete_file_or_dir

/// make a directory.
// Will make necessary subpaths if command extensions are enabled.
// @function make_dir

/// remove a directory.
// @param dir the directory
// @param tree if true, clean out the directory tree
// @function remove_dir

/// iterator over directory contents.
// @usage for f in winapi.files 'dir\\*.txt' do print(f) end
// @param mask a file mask like "*.txt"
// @param subdirs iterate over subdirectories (default no)
// @param attrib iterate over items with given attribute (as in dir /A:)
// @see files.lua
// @function files

/// iterate over subdirectories
// @param file mask like "mydirs\\t*"
// @param subdirs iterate over subdirectories (default no)
// @see files
// @function dirs

/// get all the drives on this computer.
// An example is @{drives.lua}
// @return a table of drive names
// @function get_logical_drives
def get_logical_drives() {
  int i, lasti = 0, k = 1;
  WCHAR dbuff[MAX_WPATH];
  LPWSTR p = dbuff;
  DWORD size = GetLogicalDriveStringsW(sizeof(dbuff),dbuff);
  lua_newtable(L);
  for (i = 0; i < size; i++) {
    if (dbuff[i] == '\0') {
      push_wstring_l(L,p, i - lasti);
      lua_rawseti(L,-2,k++);
      p = dbuff + i+1;
      lasti = i+1;
    }
  }
  return 1;
}

/// get the type of the given drive.
// @param root root of drive (e.g. 'c:\\')
// @return one of the following: unknown, none, removable, fixed, remote,
// cdrom, ramdisk.
// @function get_drive_type
def get_drive_type(Str root) {
  UINT res = GetDriveType(root);
  const char *type;
  switch(res) {
    case DRIVE_UNKNOWN: type = "unknown"; break;
    case DRIVE_NO_ROOT_DIR: type = "none"; break;
    case DRIVE_REMOVABLE: type = "removable"; break;
    case DRIVE_FIXED: type = "fixed"; break;
    case DRIVE_REMOTE: type = "remote"; break;
    case DRIVE_CDROM: type = "cdrom"; break;
    case DRIVE_RAMDISK: type = "ramdisk"; break;
  }
  lua_pushstring(L,type);
  return 1;
}

/// get the free disk space.
// @param root the root of the drive (e.g. 'd:\\')
// @return free space in kB
// @return total space in kB
// @function get_disk_free_space
def get_disk_free_space(Str root) {
  ULARGE_INTEGER freebytes, totalbytes;
  if (! GetDiskFreeSpaceEx(root,&freebytes,&totalbytes,NULL)) {
    return push_error(L);
  }
  lua_pushnumber(L,freebytes.QuadPart/1024);
  lua_pushnumber(L,totalbytes.QuadPart/1024);
  return 2;
}

/// get the network resource associated with this drive.
// @param root drive name in the form 'X:'
// @return UNC name
// @function get_disk_network_name
def get_disk_network_name(Str root) {
  DWORD size = sizeof(wbuff);
  DWORD res = WNetGetConnectionW(wstring(root),wbuff,&size);
  if (res == NO_ERROR) {
    return push_wstring(L,wbuff);
  } else {
    return push_error(L);
  }
}

//// start watching a directory.
// @param dir the directory
// @param how what events to monitor. Can be a sum of these flags:
//
//  * `FILE_NOTIFY_CHANGE_FILE_NAME`
//  * `FILE_NOTIFY_CHANGE_DIR_NAME`
//  * `FILE_NOTIFY_CHANGE_LAST_WRITE`
//
// @param subdirs whether subdirectories should be monitored
// @param callback a function which will receive the kind of change
// plus the filename that changed. The change will be one of these:
//
// * `FILE_ACTION_ADDED`
// * `FILE_ACTION_REMOVED`
// * `FILE_ACTION_MODIFIED`
// * `FILE_ACTION_RENAMED_OLD_NAME`
// * `FILE_ACTION_RENAMED_NEW_NAME`
//
// @return a thread object.
// @see test-watcher.lua
// @function watch_for_file_changes
def watch_for_file_changes (Str dir, Int how, Boolean subdirs, Value callback) {
  FileChangeParms *fc = (FileChangeParms*)malloc(sizeof(FileChangeParms));
  lcb_callback(fc,L,callback);
  fc->how = how;
  fc->subdirs = subdirs;
  lcb_handle(fc) = CreateFileW(wstring(dir),
    FILE_LIST_DIRECTORY,
    FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
    NULL,
    OPEN_ALWAYS,
    FILE_FLAG_BACKUP_SEMANTICS,
    NULL
    );
  if (lcb_handle(fc) == INVALID_HANDLE_VALUE) {
    return push_error(L);
  }
  lcb_allocate_buffer(fc,2048);
  return lcb_new_thread((TCB)&file_change_thread,fc);
}

/// Class representing Windows registry keys.
// @type Regkey
class Regkey {
  HKEY key;

  constructor (HKEY k) {
    this->key = k;
  }

  /// set the string value of a name.
  // @param name the name
  // @param val the value
  // @function set_value
  def set_value(Str name, Str val) {
    return push_bool(L, RegSetValueEx(this->key,name,0,REG_SZ,val,lua_objlen(L,2)) == ERROR_SUCCESS);
  }

  /// get the value and type of a name.
  // @param name the name (can be empty for the default value)
  // @return the value (either a string or a number)
  // @return the type
  // @function get_value
  def get_value(Str name = "") {
    DWORD type,size = sizeof(wbuff);
    if (RegQueryValueExW(this->key,wstring(name),0,&type,(void *)wbuff,&size) != ERROR_SUCCESS) {
      return push_error(L);
    }
    if (type == REG_BINARY) {
      lua_pushlstring(L,(const char *)wbuff,size);
    } else if (type == REG_EXPAND_SZ || type == REG_SZ) {
      push_wstring(L,wbuff); //,size);
    } else {
      lua_pushnumber(L,*(unsigned long *)wbuff);
    }
    lua_pushinteger(L,type);
    return 2;

  }

  /// enumerate the subkeys of a key.
  // @return a table of key names
  // @function get_keys
  def get_keys() {
    int i = 0;
    LONG res;
    DWORD size;
    lua_newtable(L);
    while (1) {
      size = sizeof(wbuff);
      res = RegEnumKeyExW(this->key,i,wbuff,&size,NULL,NULL,NULL,NULL);
      if (res != ERROR_SUCCESS) break;
      push_wstring(L,wbuff);
      lua_rawseti(L,-2,i+1);
      ++i;
    }
    if (res != ERROR_NO_MORE_ITEMS) {
      lua_pop(L,1);
      return push_error(L);
    }
    return 1;
  }

  /// close this key.
  // Although this will happen when garbage collection happens, it
  // is good practice to call this explicitly.
  // @function close
  def close() {
    RegCloseKey(this->key);
    this->key = NULL;
    return 0;
  }

  /// flush the key.
  // Considered an expensive function; use it only when you have
  // to guarantee modification.
  // @function flush
  def flush() {
    return push_bool(L,RegFlushKey(this->key));
  }

  def __gc() {
    if (this->key != NULL)
      RegCloseKey(this->key);
    return 0;
  }

}

/// Registry Functions.
// @section Registry

/// Open a registry key.
// @{test-reg.lua} shows reading a registry value and enumerating subkeys.
// @param path the full registry key
// e.g `[[HKEY\_LOCAL\_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion]]`
// @param writeable true if you want to set values
// @return @{Regkey}
// @function open_reg_key
def open_reg_key(Str path, Boolean writeable) {
  HKEY hKey;
  DWORD access;
  char kbuff[1024];
  hKey = split_registry_key(path,kbuff);
  if (hKey == NULL) {
    return push_error_msg(L,"unrecognized registry key");
  }
  access = writeable ? KEY_ALL_ACCESS : (KEY_READ | KEY_ENUMERATE_SUB_KEYS);
  if (RegOpenKeyExW(hKey,wstring(kbuff),0,access,&hKey) == ERROR_SUCCESS) {
    return push_new_Regkey(L,hKey);
  } else {
    return push_error(L);
  }
}

/// Create a registry key.
// @param path the full registry key
// @return @{Regkey}
// @function create_reg_key
def create_reg_key (Str path) {
  char kbuff[1024];
  HKEY hKey = split_registry_key(path,kbuff);
  if (hKey == NULL) {
    return push_error_msg(L,"unrecognized registry key");
  }
  if (RegCreateKeyExW(hKey,wstring(kbuff),0,NULL,0,KEY_ALL_ACCESS,NULL,&hKey,NULL)) {
    return push_new_Regkey(L,hKey);
  } else {
    return push_error(L);
  }
}

lua {
function winapi.execute(cmd,unicode)
  local comspec = os.getenv('COMSPEC')
  if unicode ~= 'unicode' then
    cmd = comspec ..' /c '..cmd
    local P,f = winapi.spawn_process(cmd)
    if not P then return nil,f end
    local txt = f:read()
    local out = {}
    while txt do
      table.insert(out,txt)
      txt = f:read()
    end
    return P:wait():get_exit_code(),table.concat(out,'')
  else
    local tmpfile,res,f,out = winapi.temp_name()
    cmd = comspec..' /u /c '..cmd..' > "'..tmpfile..'"'
    local P,err = winapi.spawn_process(cmd)
    if not P then return nil,err end
    res = P:wait():get_exit_code()
    f = io.open(tmpfile)
    out = f:read '*a'
    f:close()
    os.remove(tmpfile)
    out, err = winapi.encode(winapi.CP_UTF16,winapi.CP_UTF8,out)
    if err then return nil,err end
    return res,out
  end
end
function winapi.make_name_matcher(text)
  return function(w) return tostring(w):match(text) end
end
function winapi.make_class_matcher(classname)
  return function(w) return w:get_class_name():match(classname) end
end
function winapi.find_window_ex(match)
  local res
  winapi.enum_windows(function(w)
    if match(w) then res = w end
  end)
  return res
end
function winapi.find_all_windows(match)
  local res = {}
  winapi.enum_windows(function(w)
    if match(w) then res[#res+1] = w end
  end)
  return res
end
function winapi.find_window_match(text)
  return winapi.find_window_ex(winapi.make_name_matcher(text))
end
function winapi.temp_name () return os.getenv('TEMP')..os.tmpname() end
local function exec_cmd (cmd,arg)
    local res,err = winapi.execute(cmd..' "'..arg..'"')
    if res == 0 then return true
    else return nil,err
    end
end
function winapi.make_dir(dir) return exec_cmd('mkdir',dir) end
function winapi.remove_dir(dir,tree) return exec_cmd('rmdir '.. (tree and '/S'),dir) end
function winapi.delete_file_or_dir(file) return exec_cmd('del',file) end
function winapi.files(mask,subdirs,attrib)
    local flags = '/B '
    if subdirs then flags = flags..' /S' end
    if attrib then flags = flags..' /A:'..attrib end
    local ret, text = winapi.execute('dir '..flags..' "'..mask..'"','unicode')
    if ret ~= 0 then return nil,text end
    return text:gmatch('[^\r\n]+')
end
function winapi.dirs(mask,subdirs) return winapi.files(mask,subdirs,'D') end
}


/*** Constants.
The following constants are available:

 * CP_ACP, (valid values for encoding)
 * CP_UTF8,
 * CP_UTF16,
 * SW_HIDE, (Window operations for Window.show)
 * SW_MAXIMIZE,
 * SW_MINIMIZE,
 * SW_SHOWNORMAL,
 * VK_BACK,
 * VK_TAB,
 * VK_RETURN,
 * VK_SPACE,
 * VK_PRIOR,
 * VK_NEXT,
 * VK_END,
 * VK_HOME,
 * VK_LEFT,
 * VK_UP,
 * VK_RIGHT,
 * VK_DOWN,
 * VK_INSERT,
 * VK_DELETE,
 * VK_ESCAPE,
 * VK_F1,
 * VK_F2,
 * VK_F3,
 * VK_F4,
 * VK_F5,
 * VK_F6,
 * VK_F7,
 * VK_F8,
 * VK_F9,
 * VK_F10,
 * VK_F11,
 * VK_F12,
 * FILE\_NOTIFY\_CHANGE\_FILE\_NAME  (these are input flags for watch\_for\_file\_changes)
 * FILE\_NOTIFY\_CHANGE\_DIR\_NAME
 * FILE\_NOTIFY\_CHANGE\_LAST\_WRITE
 * FILE\_ACTION\_ADDED     (these describe the change: first argument of callback)
 * FILE\_ACTION\_REMOVED
 * FILE\_ACTION\_MODIFIED
 * FILE\_ACTION\_RENAMED\_OLD\_NAME
 * FILE\_ACTION\_RENAMED\_NEW\_NAME

 @section constants
 */

 /// useful Windows API constants
 // @table constants

#define CP_UTF16 -1

constants {
  CP_ACP,
  CP_UTF8,
  CP_UTF16,
  SW_HIDE,
  SW_MAXIMIZE,
  SW_MINIMIZE,
  SW_SHOWNORMAL,
  VK_BACK,
  VK_TAB,
  VK_RETURN,
  VK_SPACE,
  VK_PRIOR,
  VK_NEXT,
  VK_END,
  VK_HOME,
  VK_LEFT,
  VK_UP,
  VK_RIGHT,
  VK_DOWN,
  VK_INSERT,
  VK_DELETE,
  VK_ESCAPE,
  VK_F1,
  VK_F2,
  VK_F3,
  VK_F4,
  VK_F5,
  VK_F6,
  VK_F7,
  VK_F8,
  VK_F9,
  VK_F10,
  VK_F11,
  VK_F12,
  FILE_NOTIFY_CHANGE_FILE_NAME,
  FILE_NOTIFY_CHANGE_DIR_NAME,
  FILE_NOTIFY_CHANGE_LAST_WRITE,
  FILE_ACTION_ADDED,
  FILE_ACTION_REMOVED,
  FILE_ACTION_MODIFIED,
  FILE_ACTION_RENAMED_OLD_NAME,
  FILE_ACTION_RENAMED_NEW_NAME
}

}