Use udev for serial device enumeration on Linux

chrome/browser/extensions/api/serial/serial_port_enumerator_posix.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "chrome/browser/extensions/api/serial/serial_port_enumerator.h"
-
-#include "base/file_util.h"
-#include "base/files/file_enumerator.h"
-#include "base/files/file_path.h"
-#include "base/strings/string_util.h"
-#include "content/public/browser/browser_thread.h"
-
-using content::BrowserThread;
-
-namespace extensions {
-
-// static
-SerialPortEnumerator::StringSet SerialPortEnumerator::GenerateValidPatterns() {
-  // TODO(miket): the set of patterns should be larger. See the rxtx project.
-  //
-  // TODO(miket): The list of patterns tested at runtime should also be
-  // OS-dependent.
-  const char* VALID_PATTERNS[] = {
-    "/dev/*Bluetooth*",
-    "/dev/*Modem*",
-    "/dev/*bluetooth*",
-    "/dev/*modem*",
-    "/dev/*serial*",
-    "/dev/ttyACM*",
-    "/dev/ttyS*",
-    "/dev/ttyUSB*",
-    "/dev/tty.SLAB_*",
-    "/dev/cu.SLAB_*",
-  };
-
-  StringSet valid_patterns;
-  for (size_t i = 0; i < arraysize(VALID_PATTERNS); ++i)
-    valid_patterns.insert(VALID_PATTERNS[i]);
-
-  return valid_patterns;
-}
-
-// static
-//
-// TODO(miket): Investigate udev. Search for equivalent solutions on OSX.
-// Continue to examine rxtx code.
-//
-// On a fairly ordinary Linux machine, ls -l /dev | wc -l returned about 200
-// items. So we're doing about N(VALID_PATTERNS) * 200 = 1,600 MatchPattern
-// calls to find maybe a dozen serial ports in a small number of milliseconds
-// (a single trial of SerialPortEnumeratorTest.ValidPortNames took 6ms to run).
-// It's not cheap, but then again, we don't expect users of this API to be
-// enumerating too often (at worst on every click of a UI element that displays
-// the generated list).
-//
-// An upside-down approach would instead take each pattern and turn it into a
-// string generator (something like /dev/ttyS[0-9]{0,3}) and then expanding
-// that into a series of possible paths, perhaps early-outing if we knew that
-// port patterns were contiguous (e.g., /dev/ttyS1 can't exist if /dev/ttyS0
-// doesn't exist).
-//
-// Caching seems undesirable. Many devices can be dynamically added to and
-// removed from the system, so we really do want to regenerate the set each
-// time.
-//
-// TODO(miket): this might be refactorable into serial_connection.cc, if
-// Windows serial-port enumeration also entails looking through a directory.
-SerialPortEnumerator::StringSet
-SerialPortEnumerator::GenerateValidSerialPortNames() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  const base::FilePath kDevRoot("/dev");
-  const int kFilesAndSymLinks =
-      base::FileEnumerator::FILES |
-      base::FileEnumerator::SHOW_SYM_LINKS;
-
-  StringSet valid_patterns = GenerateValidPatterns();
-  StringSet name_set;
-  base::FileEnumerator enumerator(kDevRoot, false, kFilesAndSymLinks);
-  do {
-    const base::FilePath next_device_path(enumerator.Next());
-    const std::string next_device = next_device_path.value();
-    if (next_device.empty())
-      break;
-
-    StringSet::const_iterator i = valid_patterns.begin();
-    for (; i != valid_patterns.end(); ++i) {
-      if (MatchPattern(next_device, *i)) {
-        name_set.insert(next_device);
-        break;
-      }
-    }
-  } while (true);
-
-  return name_set;
-}
-
-}  // namespace extensions