dom/system/OSFileConstants.cpp
author Nagarjuna Varma <junky.argonaut@gmail.com>
Sat, 22 Dec 2012 18:35:07 -0500
changeset 116910 bab7ae06e579d274c81c5701ee87e35df8e14265
parent 116221 a0f9ff3c98944638044f854468412bd0f5f11d95
child 123035 7c638eba3a46b48ebdcb70e6dadf8f281c01bb96
permissions -rw-r--r--
Bug 785060 - Check for allocation failure in JS_NewUCStringCopyZ calls; r=Ms2ger

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/DebugOnly.h"

#include "fcntl.h"
#include "errno.h"

#include "prsystem.h"

#if defined(XP_UNIX)
#include "unistd.h"
#include "dirent.h"
#include "sys/stat.h"
#endif // defined(XP_UNIX)

#if defined(XP_MACOSX)
#include "copyfile.h"
#endif // defined(XP_MACOSX)

#if defined(XP_WIN)
#include <windows.h>
#endif // defined(XP_WIN)

#include "jsapi.h"
#include "jsfriendapi.h"
#include "BindingUtils.h"

// Used to provide information on the OS

#include "nsThreadUtils.h"
#include "nsIObserverService.h"
#include "nsIObserver.h"
#include "nsDirectoryServiceUtils.h"
#include "nsIXULRuntime.h"
#include "nsXPCOMCIDInternal.h"
#include "nsServiceManagerUtils.h"
#include "nsString.h"
#include "nsAutoPtr.h"
#include "nsDirectoryServiceDefs.h"
#include "nsAppDirectoryServiceDefs.h"
#include "mozJSComponentLoader.h"

#include "OSFileConstants.h"
#include "nsIOSFileConstantsService.h"

#if defined(__DragonFly__) || defined(__FreeBSD__) \
  || defined(__NetBSD__) || defined(__OpenBSD__)
#define __dd_fd dd_fd
#endif

/**
 * This module defines the basic libc constants (error numbers, open modes,
 * etc.) used by OS.File and possibly other OS-bound JavaScript libraries.
 */


namespace mozilla {

// Use an anonymous namespace to hide the symbols and avoid any collision
// with, for instance, |extern bool gInitialized;|
namespace {
/**
 * |true| if this module has been initialized, |false| otherwise
 */
bool gInitialized = false;

struct Paths {
  /**
   * The name of the directory holding all the libraries (libxpcom, libnss, etc.)
   */
  nsString libDir;
  nsString tmpDir;
  nsString profileDir;
  nsString localProfileDir;

  Paths()
  {
    libDir.SetIsVoid(true);
    tmpDir.SetIsVoid(true);
    profileDir.SetIsVoid(true);
    localProfileDir.SetIsVoid(true);
  }
};

/**
 * System directories.
 */
Paths* gPaths = NULL;

}

/**
 * Return the path to one of the special directories.
 *
 * @param aKey The key to the special directory (e.g. "TmpD", "ProfD", ...)
 * @param aOutPath The path to the special directory. In case of error,
 * the string is set to void.
 */
nsresult GetPathToSpecialDir(const char *aKey, nsString& aOutPath)
{
  nsCOMPtr<nsIFile> file;
  nsresult rv = NS_GetSpecialDirectory(aKey, getter_AddRefs(file));
  if (NS_FAILED(rv) || !file) {
    return rv;
  }

  return file->GetPath(aOutPath);
}

/**
 * In some cases, OSFileConstants may be instantiated before the
 * profile is setup. In such cases, |OS.Constants.Path.profileDir| and
 * |OS.Constants.Path.localProfileDir| are undefined. However, we want
 * to ensure that this does not break existing code, so that future
 * workers spawned after the profile is setup have these constants.
 *
 * For this purpose, we register an observer to set |gPaths->profileDir|
 * and |gPaths->localProfileDir| once the profile is setup.
 */
class DelayedPathSetter MOZ_FINAL: public nsIObserver
{
  NS_DECL_ISUPPORTS
  NS_DECL_NSIOBSERVER

  DelayedPathSetter() {}
};

NS_IMPL_ISUPPORTS1(DelayedPathSetter, nsIObserver)

NS_IMETHODIMP
DelayedPathSetter::Observe(nsISupports*, const char * aTopic, const PRUnichar*)
{
  if (gPaths == nullptr) {
    // Initialization of gPaths has not taken place, something is wrong,
    // don't make things worse.
    return NS_OK;
  }
  nsresult rv = GetPathToSpecialDir(NS_APP_USER_PROFILE_50_DIR, gPaths->profileDir);
  if (NS_FAILED(rv)) {
    return rv;
  }
  rv = GetPathToSpecialDir(NS_APP_USER_PROFILE_LOCAL_50_DIR, gPaths->localProfileDir);
  if (NS_FAILED(rv)) {
    return rv;
  }

  return NS_OK;
}

/**
 * Perform the part of initialization that can only be
 * executed on the main thread.
 */
nsresult InitOSFileConstants()
{
  MOZ_ASSERT(NS_IsMainThread());
  if (gInitialized) {
    return NS_OK;
  }

  gInitialized = true;

  nsAutoPtr<Paths> paths(new Paths);

  // Initialize paths->libDir
  nsCOMPtr<nsIFile> file;
  nsresult rv = NS_GetSpecialDirectory("XpcomLib", getter_AddRefs(file));
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsCOMPtr<nsIFile> libDir;
  rv = file->GetParent(getter_AddRefs(libDir));
  if (NS_FAILED(rv)) {
    return rv;
  }

  rv = libDir->GetPath(paths->libDir);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Setup profileDir and localProfileDir immediately if possible (we
  // assume that NS_APP_USER_PROFILE_50_DIR and
  // NS_APP_USER_PROFILE_LOCAL_50_DIR are set simultaneously)
  rv = GetPathToSpecialDir(NS_APP_USER_PROFILE_50_DIR, paths->profileDir);
  if (NS_SUCCEEDED(rv)) {
    rv = GetPathToSpecialDir(NS_APP_USER_PROFILE_LOCAL_50_DIR, paths->localProfileDir);
  }

  // Otherwise, delay setup of profileDir/localProfileDir until they
  // become available.
  if (NS_FAILED(rv)) {
    nsCOMPtr<nsIObserverService> obsService = do_GetService(NS_OBSERVERSERVICE_CONTRACTID, &rv);
    if (NS_FAILED(rv)) {
      return rv;
    }
    nsRefPtr<DelayedPathSetter> pathSetter = new DelayedPathSetter();
    rv = obsService->AddObserver(pathSetter, "profile-do-change", false);
    if (NS_FAILED(rv)) {
      return rv;
    }
  }

  // For other directories, ignore errors (they may be undefined on
  // some platforms or in non-Firefox embeddings of Gecko).

  GetPathToSpecialDir(NS_OS_TEMP_DIR, paths->tmpDir);

  gPaths = paths.forget();
  return NS_OK;
}

/**
 * Perform the cleaning up that can only be executed on the main thread.
 */
void CleanupOSFileConstants()
{
  MOZ_ASSERT(NS_IsMainThread());
  if (!gInitialized) {
    return;
  }

  gInitialized = false;
  delete gPaths;
}


/**
 * Define a simple read-only property holding an integer.
 *
 * @param name The name of the constant. Used both as the JS name for the
 * constant and to access its value. Must be defined.
 *
 * Produces a |ConstantSpec|.
 */
#define INT_CONSTANT(name)      \
  { #name, INT_TO_JSVAL(name) }

/**
 * End marker for ConstantSpec
 */
#define PROP_END { NULL, JSVAL_VOID }


// Define missing constants for Android
#if !defined(S_IRGRP)
#define S_IXOTH 0001
#define S_IWOTH 0002
#define S_IROTH 0004
#define S_IRWXO 0007
#define S_IXGRP 0010
#define S_IWGRP 0020
#define S_IRGRP 0040
#define S_IRWXG 0070
#define S_IXUSR 0100
#define S_IWUSR 0200
#define S_IRUSR 0400
#define S_IRWXU 0700
#endif // !defined(S_IRGRP)

/**
 * The properties defined in libc.
 *
 * If you extend this list of properties, please
 * separate categories ("errors", "open", etc.),
 * keep properties organized by alphabetical order
 * and #ifdef-away properties that are not portable.
 */
static dom::ConstantSpec gLibcProperties[] =
{
  // Arguments for open
  INT_CONSTANT(O_APPEND),
  INT_CONSTANT(O_CREAT),
#if defined(O_DIRECTORY)
  INT_CONSTANT(O_DIRECTORY),
#endif // defined(O_DIRECTORY)
#if defined(O_EVTONLY)
  INT_CONSTANT(O_EVTONLY),
#endif // defined(O_EVTONLY)
  INT_CONSTANT(O_EXCL),
#if defined(O_EXLOCK)
  INT_CONSTANT(O_EXLOCK),
#endif // defined(O_EXLOCK)
#if defined(O_LARGEFILE)
  INT_CONSTANT(O_LARGEFILE),
#endif // defined(O_LARGEFILE)
#if defined(O_NOFOLLOW)
  INT_CONSTANT(O_NOFOLLOW),
#endif // defined(O_NOFOLLOW)
#if defined(O_NONBLOCK)
  INT_CONSTANT(O_NONBLOCK),
#endif // defined(O_NONBLOCK)
  INT_CONSTANT(O_RDONLY),
  INT_CONSTANT(O_RDWR),
#if defined(O_RSYNC)
  INT_CONSTANT(O_RSYNC),
#endif // defined(O_RSYNC)
#if defined(O_SHLOCK)
  INT_CONSTANT(O_SHLOCK),
#endif // defined(O_SHLOCK)
#if defined(O_SYMLINK)
  INT_CONSTANT(O_SYMLINK),
#endif // defined(O_SYMLINK)
#if defined(O_SYNC)
  INT_CONSTANT(O_SYNC),
#endif // defined(O_SYNC)
  INT_CONSTANT(O_TRUNC),
  INT_CONSTANT(O_WRONLY),

#if defined(AT_EACCESS)
  INT_CONSTANT(AT_EACCESS),
#endif //defined(AT_EACCESS)
#if defined(AT_FDCWD)
  INT_CONSTANT(AT_FDCWD),
#endif //defined(AT_FDCWD)
#if defined(AT_SYMLINK_NOFOLLOW)
  INT_CONSTANT(AT_SYMLINK_NOFOLLOW),
#endif //defined(AT_SYMLINK_NOFOLLOW)

  // access
#if defined(F_OK)
  INT_CONSTANT(F_OK),
  INT_CONSTANT(R_OK),
  INT_CONSTANT(W_OK),
  INT_CONSTANT(X_OK),
#endif // defined(F_OK)

  // modes
  INT_CONSTANT(S_IRGRP),
  INT_CONSTANT(S_IROTH),
  INT_CONSTANT(S_IRUSR),
  INT_CONSTANT(S_IRWXG),
  INT_CONSTANT(S_IRWXO),
  INT_CONSTANT(S_IRWXU),
  INT_CONSTANT(S_IWGRP),
  INT_CONSTANT(S_IWOTH),
  INT_CONSTANT(S_IWUSR),
  INT_CONSTANT(S_IXOTH),
  INT_CONSTANT(S_IXGRP),
  INT_CONSTANT(S_IXUSR),

  // seek
  INT_CONSTANT(SEEK_CUR),
  INT_CONSTANT(SEEK_END),
  INT_CONSTANT(SEEK_SET),

  // copyfile
#if defined(COPYFILE_DATA)
  INT_CONSTANT(COPYFILE_DATA),
  INT_CONSTANT(COPYFILE_EXCL),
  INT_CONSTANT(COPYFILE_XATTR),
  INT_CONSTANT(COPYFILE_STAT),
  INT_CONSTANT(COPYFILE_ACL),
  INT_CONSTANT(COPYFILE_MOVE),
#endif // defined(COPYFILE_DATA)

  // error values
  INT_CONSTANT(EACCES),
  INT_CONSTANT(EAGAIN),
  INT_CONSTANT(EBADF),
  INT_CONSTANT(EEXIST),
  INT_CONSTANT(EFAULT),
  INT_CONSTANT(EFBIG),
  INT_CONSTANT(EINVAL),
  INT_CONSTANT(EIO),
  INT_CONSTANT(EISDIR),
#if defined(ELOOP) // not defined with VC9
  INT_CONSTANT(ELOOP),
#endif // defined(ELOOP)
  INT_CONSTANT(EMFILE),
  INT_CONSTANT(ENAMETOOLONG),
  INT_CONSTANT(ENFILE),
  INT_CONSTANT(ENOENT),
  INT_CONSTANT(ENOMEM),
  INT_CONSTANT(ENOSPC),
  INT_CONSTANT(ENOTDIR),
  INT_CONSTANT(ENXIO),
#if defined(EOPNOTSUPP) // not defined with VC 9
  INT_CONSTANT(EOPNOTSUPP),
#endif // defined(EOPNOTSUPP)
#if defined(EOVERFLOW) // not defined with VC 9
  INT_CONSTANT(EOVERFLOW),
#endif // defined(EOVERFLOW)
  INT_CONSTANT(EPERM),
  INT_CONSTANT(ERANGE),
#if defined(ETIMEDOUT) // not defined with VC 9
  INT_CONSTANT(ETIMEDOUT),
#endif // defined(ETIMEDOUT)
#if defined(EWOULDBLOCK) // not defined with VC 9
  INT_CONSTANT(EWOULDBLOCK),
#endif // defined(EWOULDBLOCK)
  INT_CONSTANT(EXDEV),

#if defined(DT_UNKNOWN)
  // Constants for |readdir|
  INT_CONSTANT(DT_UNKNOWN),
  INT_CONSTANT(DT_FIFO),
  INT_CONSTANT(DT_CHR),
  INT_CONSTANT(DT_DIR),
  INT_CONSTANT(DT_BLK),
  INT_CONSTANT(DT_REG),
  INT_CONSTANT(DT_LNK),
  INT_CONSTANT(DT_SOCK),
#endif // defined(DT_UNKNOWN)

#if defined(S_IFIFO)
  // Constants for |stat|
  INT_CONSTANT(S_IFMT),
  INT_CONSTANT(S_IFIFO),
  INT_CONSTANT(S_IFCHR),
  INT_CONSTANT(S_IFDIR),
  INT_CONSTANT(S_IFBLK),
  INT_CONSTANT(S_IFREG),
  INT_CONSTANT(S_IFLNK),
  INT_CONSTANT(S_IFSOCK),
#endif // defined(S_IFIFO)

  // Constants used to define data structures
  //
  // Many data structures have different fields/sizes/etc. on
  // various OSes / versions of the same OS / platforms. For these
  // data structures, we need to compute and export from C the size
  // and, if necessary, the offset of fields, so as to be able to
  // define the structure in JS.

#if defined(XP_UNIX)
  // The size of |mode_t|.
  { "OSFILE_SIZEOF_MODE_T", INT_TO_JSVAL(sizeof (mode_t)) },

  // The size of |gid_t|.
  { "OSFILE_SIZEOF_GID_T", INT_TO_JSVAL(sizeof (gid_t)) },

  // The size of |uid_t|.
  { "OSFILE_SIZEOF_UID_T", INT_TO_JSVAL(sizeof (uid_t)) },

  // The size of |time_t|.
  { "OSFILE_SIZEOF_TIME_T", INT_TO_JSVAL(sizeof (time_t)) },

  // Defining |dirent|.
  // Size
  { "OSFILE_SIZEOF_DIRENT", INT_TO_JSVAL(sizeof (dirent)) },

  // Offset of field |d_name|.
  { "OSFILE_OFFSETOF_DIRENT_D_NAME", INT_TO_JSVAL(offsetof (struct dirent, d_name)) },
  // An upper bound to the length of field |d_name| of struct |dirent|.
  // (may not be exact, depending on padding).
  { "OSFILE_SIZEOF_DIRENT_D_NAME", INT_TO_JSVAL(sizeof (struct dirent) - offsetof (struct dirent, d_name)) },

#if defined(DT_UNKNOWN)
  // Position of field |d_type| in |dirent|
  // Not strictly posix, but seems defined on all platforms
  // except mingw32.
  { "OSFILE_OFFSETOF_DIRENT_D_TYPE", INT_TO_JSVAL(offsetof (struct dirent, d_type)) },
#endif // defined(DT_UNKNOWN)

  // Under MacOS X and BSDs, |dirfd| is a macro rather than a
  // function, so we need a little help to get it to work
#if defined(dirfd)
  { "OSFILE_SIZEOF_DIR", INT_TO_JSVAL(sizeof (DIR)) },

  { "OSFILE_OFFSETOF_DIR_DD_FD", INT_TO_JSVAL(offsetof (DIR, __dd_fd)) },
#endif

  // Defining |stat|

  { "OSFILE_SIZEOF_STAT", INT_TO_JSVAL(sizeof (struct stat)) },

  { "OSFILE_OFFSETOF_STAT_ST_MODE", INT_TO_JSVAL(offsetof (struct stat, st_mode)) },
  { "OSFILE_OFFSETOF_STAT_ST_UID", INT_TO_JSVAL(offsetof (struct stat, st_uid)) },
  { "OSFILE_OFFSETOF_STAT_ST_GID", INT_TO_JSVAL(offsetof (struct stat, st_gid)) },
  { "OSFILE_OFFSETOF_STAT_ST_SIZE", INT_TO_JSVAL(offsetof (struct stat, st_size)) },

#if defined(HAVE_ST_ATIMESPEC)
  { "OSFILE_OFFSETOF_STAT_ST_ATIME", INT_TO_JSVAL(offsetof (struct stat, st_atimespec)) },
  { "OSFILE_OFFSETOF_STAT_ST_MTIME", INT_TO_JSVAL(offsetof (struct stat, st_mtimespec)) },
  { "OSFILE_OFFSETOF_STAT_ST_CTIME", INT_TO_JSVAL(offsetof (struct stat, st_ctimespec)) },
#else
  { "OSFILE_OFFSETOF_STAT_ST_ATIME", INT_TO_JSVAL(offsetof (struct stat, st_atime)) },
  { "OSFILE_OFFSETOF_STAT_ST_MTIME", INT_TO_JSVAL(offsetof (struct stat, st_mtime)) },
  { "OSFILE_OFFSETOF_STAT_ST_CTIME", INT_TO_JSVAL(offsetof (struct stat, st_ctime)) },
#endif // defined(HAVE_ST_ATIME)

  // Several OSes have a birthtime field. For the moment, supporting only Darwin.
#if defined(_DARWIN_FEATURE_64_BIT_INODE)
  { "OSFILE_OFFSETOF_STAT_ST_BIRTHTIME", INT_TO_JSVAL(offsetof (struct stat, st_birthtime)) },
#endif // defined(_DARWIN_FEATURE_64_BIT_INODE)

#endif // defined(XP_UNIX)



  // System configuration

  // Under MacOSX, to avoid using deprecated functions that do not
  // match the constants we define in this object (including
  // |sizeof|/|offsetof| stuff, but not only), for a number of
  // functions, we need to adapt the name of the symbols we are using,
  // whenever macro _DARWIN_FEATURE_64_BIT_INODE is set. We export
  // this value to be able to do so from JavaScript.
#if defined(_DARWIN_FEATURE_64_BIT_INODE)
   { "_DARWIN_FEATURE_64_BIT_INODE", INT_TO_JSVAL(1) },
#endif // defined(_DARWIN_FEATURE_64_BIT_INODE)

  // Similar feature for Linux
#if defined(_STAT_VER)
  INT_CONSTANT(_STAT_VER),
#endif // defined(_STAT_VER)

  PROP_END
};


#if defined(XP_WIN)
/**
 * The properties defined in windows.h.
 *
 * If you extend this list of properties, please
 * separate categories ("errors", "open", etc.),
 * keep properties organized by alphabetical order
 * and #ifdef-away properties that are not portable.
 */
static dom::ConstantSpec gWinProperties[] =
{
  // FormatMessage flags
  INT_CONSTANT(FORMAT_MESSAGE_FROM_SYSTEM),
  INT_CONSTANT(FORMAT_MESSAGE_IGNORE_INSERTS),

  // The max length of paths
  INT_CONSTANT(MAX_PATH),

  // CreateFile desired access
  INT_CONSTANT(GENERIC_ALL),
  INT_CONSTANT(GENERIC_EXECUTE),
  INT_CONSTANT(GENERIC_READ),
  INT_CONSTANT(GENERIC_WRITE),

  // CreateFile share mode
  INT_CONSTANT(FILE_SHARE_DELETE),
  INT_CONSTANT(FILE_SHARE_READ),
  INT_CONSTANT(FILE_SHARE_WRITE),

  // CreateFile creation disposition
  INT_CONSTANT(CREATE_ALWAYS),
  INT_CONSTANT(CREATE_NEW),
  INT_CONSTANT(OPEN_ALWAYS),
  INT_CONSTANT(OPEN_EXISTING),
  INT_CONSTANT(TRUNCATE_EXISTING),

  // CreateFile attributes
  INT_CONSTANT(FILE_ATTRIBUTE_ARCHIVE),
  INT_CONSTANT(FILE_ATTRIBUTE_DIRECTORY),
  INT_CONSTANT(FILE_ATTRIBUTE_NORMAL),
  INT_CONSTANT(FILE_ATTRIBUTE_READONLY),
  INT_CONSTANT(FILE_ATTRIBUTE_REPARSE_POINT),
  INT_CONSTANT(FILE_ATTRIBUTE_TEMPORARY),
  INT_CONSTANT(FILE_FLAG_BACKUP_SEMANTICS),

  // CreateFile error constant
  { "INVALID_HANDLE_VALUE", INT_TO_JSVAL(INT_PTR(INVALID_HANDLE_VALUE)) },


  // CreateFile flags
  INT_CONSTANT(FILE_FLAG_DELETE_ON_CLOSE),

  // SetFilePointer methods
  INT_CONSTANT(FILE_BEGIN),
  INT_CONSTANT(FILE_CURRENT),
  INT_CONSTANT(FILE_END),

  // SetFilePointer error constant
  INT_CONSTANT(INVALID_SET_FILE_POINTER),

  // File attributes
  INT_CONSTANT(FILE_ATTRIBUTE_DIRECTORY),


  // MoveFile flags
  INT_CONSTANT(MOVEFILE_COPY_ALLOWED),
  INT_CONSTANT(MOVEFILE_REPLACE_EXISTING),

  // Errors
  INT_CONSTANT(ERROR_ACCESS_DENIED),
  INT_CONSTANT(ERROR_DIR_NOT_EMPTY),
  INT_CONSTANT(ERROR_FILE_EXISTS),
  INT_CONSTANT(ERROR_ALREADY_EXISTS),
  INT_CONSTANT(ERROR_FILE_NOT_FOUND),
  INT_CONSTANT(ERROR_NO_MORE_FILES),

  PROP_END
};
#endif // defined(XP_WIN)


/**
 * Get a field of an object as an object.
 *
 * If the field does not exist, create it. If it exists but is not an
 * object, throw a JS error.
 */
JSObject *GetOrCreateObjectProperty(JSContext *cx, JSObject *aObject,
                                    const char *aProperty)
{
  JS::Value val;
  if (!JS_GetProperty(cx, aObject, aProperty, &val)) {
    return NULL;
  }
  if (!val.isUndefined()) {
    if (val.isObject()) {
      return &val.toObject();
    }

    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
      JSMSG_UNEXPECTED_TYPE, aProperty, "not an object");
    return NULL;
  }
  return JS_DefineObject(cx, aObject, aProperty, NULL, NULL, JSPROP_ENUMERATE);
}

/**
 * Set a property of an object from a nsString.
 *
 * If the nsString is void (i.e. IsVoid is true), do nothing.
 */
bool SetStringProperty(JSContext *cx, JSObject *aObject, const char *aProperty,
                       const nsString aValue)
{
  if (aValue.IsVoid()) {
    return true;
  }
  JSString* strValue = JS_NewUCStringCopyZ(cx, aValue.get());
  NS_ENSURE_TRUE(strValue, false);
  jsval valValue = STRING_TO_JSVAL(strValue);
  return JS_SetProperty(cx, aObject, aProperty, &valValue);
}

/**
 * Define OS-specific constants.
 *
 * This function creates or uses JS object |OS.Constants| to store
 * all its constants.
 */
bool DefineOSFileConstants(JSContext *cx, JSObject *global)
{
  MOZ_ASSERT(gInitialized);

  if (gPaths == NULL) {
    // If an initialization error was ignored, we may end up with
    // |gInitialized == true| but |gPaths == NULL|. We cannot
    // |MOZ_ASSERT| this, as this would kill precompile_cache.js,
    // so we simply return an error.
    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
      JSMSG_CANT_OPEN, "OSFileConstants", "initialization has failed");
    return false;
  }

  JSObject *objOS;
  if (!(objOS = GetOrCreateObjectProperty(cx, global, "OS"))) {
    return false;
  }
  JSObject *objConstants;
  if (!(objConstants = GetOrCreateObjectProperty(cx, objOS, "Constants"))) {
    return false;
  }

  // Build OS.Constants.libc

  JSObject *objLibc;
  if (!(objLibc = GetOrCreateObjectProperty(cx, objConstants, "libc"))) {
    return false;
  }
  if (!dom::DefineConstants(cx, objLibc, gLibcProperties)) {
    return false;
  }

#if defined(XP_WIN)
  // Build OS.Constants.Win

  JSObject *objWin;
  if (!(objWin = GetOrCreateObjectProperty(cx, objConstants, "Win"))) {
    return false;
  }
  if (!dom::DefineConstants(cx, objWin, gWinProperties)) {
    return false;
  }
#endif // defined(XP_WIN)

  // Build OS.Constants.Sys

  JSObject *objSys;
  if (!(objSys = GetOrCreateObjectProperty(cx, objConstants, "Sys"))) {
    return false;
  }

  nsCOMPtr<nsIXULRuntime> runtime = do_GetService(XULRUNTIME_SERVICE_CONTRACTID);
  if (runtime) {
    nsAutoCString os;
    DebugOnly<nsresult> rv = runtime->GetOS(os);
    MOZ_ASSERT(NS_SUCCEEDED(rv));

    JSString* strVersion = JS_NewStringCopyZ(cx, os.get());
    if (!strVersion) {
      return false;
    }

    jsval valVersion = STRING_TO_JSVAL(strVersion);
    if (!JS_SetProperty(cx, objSys, "Name", &valVersion)) {
      return false;
    }
  }

  // Build OS.Constants.Path

  JSObject *objPath;
  if (!(objPath = GetOrCreateObjectProperty(cx, objConstants, "Path"))) {
    return false;
  }

  // Locate libxul
  {
    nsAutoString xulPath(gPaths->libDir);

    xulPath.Append(PR_GetDirectorySeparator());

#if defined(XP_MACOSX)
    // Under MacOS X, for some reason, libxul is called simply "XUL"
    xulPath.Append(NS_LITERAL_STRING("XUL"));
#else
    // On other platforms, libxul is a library "xul" with regular
    // library prefix/suffix
    xulPath.Append(NS_LITERAL_STRING(DLL_PREFIX));
    xulPath.Append(NS_LITERAL_STRING("xul"));
    xulPath.Append(NS_LITERAL_STRING(DLL_SUFFIX));
#endif // defined(XP_MACOSX)

    if (!SetStringProperty(cx, objPath, "libxul", xulPath)) {
      return false;
    }
  }

  if (!SetStringProperty(cx, objPath, "libDir", gPaths->libDir)) {
    return false;
  }

  if (!SetStringProperty(cx, objPath, "tmpDir", gPaths->tmpDir)) {
    return false;
  }

  // Configure profileDir only if it is available at this stage
  if (!gPaths->profileDir.IsVoid()
    && !SetStringProperty(cx, objPath, "profileDir", gPaths->profileDir)) {
    return false;
  }

  // Configure localProfileDir only if it is available at this stage
  if (!gPaths->localProfileDir.IsVoid()
    && !SetStringProperty(cx, objPath, "localProfileDir", gPaths->localProfileDir)) {
    return false;
  }

  return true;
}

NS_IMPL_ISUPPORTS1(OSFileConstantsService, nsIOSFileConstantsService)

OSFileConstantsService::OSFileConstantsService()
{
  MOZ_ASSERT(NS_IsMainThread());
}

OSFileConstantsService::~OSFileConstantsService()
{
  mozilla::CleanupOSFileConstants();
}


NS_IMETHODIMP
OSFileConstantsService::Init(JSContext *aCx)
{
  nsresult rv = mozilla::InitOSFileConstants();
  if (NS_FAILED(rv)) {
    return rv;
  }

  JSObject *targetObj = nullptr;

  mozJSComponentLoader* loader = mozJSComponentLoader::Get();
  rv = loader->FindTargetObject(aCx, &targetObj);
  NS_ENSURE_SUCCESS(rv, rv);

  if (!mozilla::DefineOSFileConstants(aCx, targetObj)) {
    return NS_ERROR_FAILURE;
  }

  return NS_OK;
}

} // namespace mozilla