Adds USB writing for OS X.

chrome/utility/image_writer/image_writer_mac.cc

+// Copyright 2014 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 <sys/socket.h>

[Robert Sesek, 2014/06/16 19:32:54]

nit: s > I (assuming capitalization doesn't matter, do whatever PRESUBMIT.py
says).

[Drew Haven, 2014/06/16 21:51:39]

Done.  I don't think the 'git cl upload' presubmit checks complained either way.
 They might not care about the order of system includes because those may have
ordering constraints (like they do on windows).

+#include <IOKit/storage/IOStorageProtocolCharacteristics.h>
+
+#include "base/command_line.h"
+#include "base/files/scoped_file.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/process/kill.h"
+#include "base/process/launch.h"
+#include "base/strings/stringprintf.h"
+#include "chrome/utility/image_writer/disk_unmounter_mac.h"
+#include "chrome/utility/image_writer/error_messages.h"
+#include "chrome/utility/image_writer/image_writer.h"
+
+namespace image_writer {
+
+static const char kAuthOpenPath[] = "/usr/libexec/authopen";
+static const size_t kDataBufferSize = 1024;
+
+bool ImageWriter::IsValidDevice() {
+  base::ScopedCFTypeRef<DASessionRef> session(DASessionCreate(NULL));
+  base::ScopedCFTypeRef<DADiskRef> disk(DADiskCreateFromBSDName(
+      kCFAllocatorDefault, session, device_path_.value().c_str()));
+
+  if (!disk)
+    return false;
+
+  base::ScopedCFTypeRef<CFDictionaryRef> disk_description(
+      DADiskCopyDescription(disk));
+
+  CFBooleanRef ejectable = base::mac::GetValueFromDictionary<CFBooleanRef>(
+      disk_description, kDADiskDescriptionMediaEjectableKey);
+  CFBooleanRef removable = base::mac::GetValueFromDictionary<CFBooleanRef>(
+      disk_description, kDADiskDescriptionMediaRemovableKey);
+  CFBooleanRef writable = base::mac::GetValueFromDictionary<CFBooleanRef>(
+      disk_description, kDADiskDescriptionMediaWritableKey);
+  CFBooleanRef whole = base::mac::GetValueFromDictionary<CFBooleanRef>(
+      disk_description, kDADiskDescriptionMediaWholeKey);
+  CFStringRef kind = base::mac::GetValueFromDictionary<CFStringRef>(
+      disk_description, kDADiskDescriptionMediaKindKey);
+
+  // A drive is valid if it is
+  // - ejectable
+  // - removable
+  // - writable
+  // - a whole drive
+  // - it is of type IOMedia (external DVD drives and the like are IOCDMedia or
+  //   IODVDMedia)
+  return CFBooleanGetValue(ejectable) && CFBooleanGetValue(removable) &&
+         CFBooleanGetValue(writable) && CFBooleanGetValue(whole) &&
+         CFStringCompare(kind, CFSTR("IOMedia"), 0) == kCFCompareEqualTo;
+}
+
+void ImageWriter::UnmountVolumes(const base::Closure& continuation) {
+  if (unmounter_ == NULL) {
+    unmounter_.reset(new DiskUnmounterMac());
+  }
+
+  unmounter_->Unmount(
+      device_path_.value(),
+      continuation,
+      base::Bind(
+          &ImageWriter::Error, base::Unretained(this), error::kUnmountVolumes));
+}
+
+bool ImageWriter::OpenDevice() {
+  base::LaunchOptions options = base::LaunchOptions();
+  options.wait = false;
+
+  // Create a socket pair for communication.
+  int sockets[2];
+  int result = socketpair(AF_UNIX, SOCK_STREAM, 0, sockets);
+  if (result == -1) {
+    LOG(ERROR) << "Unable to allocate socket pair.";

[Robert Sesek, 2014/06/16 19:32:53]

Use PLOG to capture errno in the output.

[Drew Haven, 2014/06/16 21:51:39]

Done.

+    return false;
+  }
+  base::ScopedFD parent_socket(sockets[0]);
+  base::ScopedFD child_socket(sockets[1]);
+
+  // Map the client socket to the client's STDOUT.
+  base::FileHandleMappingVector fd_map;
+  fd_map.push_back(std::pair<int, int>(child_socket.get(), STDOUT_FILENO));
+  options.fds_to_remap = &fd_map;
+
+  // Find the file path to open.
+  base::FilePath real_device_path;
+  if (device_path_.IsAbsolute()) {
+    real_device_path = device_path_;
+  } else {
+    real_device_path = base::FilePath("/dev").Append(device_path_);
+  }
+
+  // Build the command line.
+  std::string rdwr = base::StringPrintf("%d", O_RDWR);
+
+  base::CommandLine cmd_line((base::FilePath(kAuthOpenPath)));
+  cmd_line.AppendSwitch("-stdoutpipe");
+  // Using AppendSwitchNative will use an equal-symbol which we don't want.
+  cmd_line.AppendArg("-o");
+  cmd_line.AppendArg(rdwr);
+  cmd_line.AppendArgPath(real_device_path);
+
+  // Launch the process.
+  base::ProcessHandle process_handle;
+  if (!base::LaunchProcess(cmd_line, options, &process_handle)) {
+    LOG(ERROR) << "Failed to launch authopen process.";
+    return false;
+  }
+
+  // Receive a file descriptor from authopen which sends a single FD via
+  // sendmsg and the SCM_RIGHTS extension.
+  int fd = -1;
+  char data_buffer[kDataBufferSize];

[Robert Sesek, 2014/06/16 19:32:53]

What is data_buffer used for and where did the value for |kDataBufferSize| come
from?

[Drew Haven, 2014/06/16 21:51:39]

So, I looked into it.  What we want is the size of the header plus enough room
for the file handle, I've adjusted accordingly and tested on my system to verify
it's true.

+
+  iovec io_vec[1];

[Robert Sesek, 2014/06/16 19:32:54]

I know it's not necessary in C++, but since this is a C struct, I like using
|struct iovec io_vec|.

[Drew Haven, 2014/06/16 21:51:39]

Done.

+  io_vec[0].iov_base = data_buffer;
+  io_vec[0].iov_len = kDataBufferSize;
+
+  const socklen_t kCmsgSocketSize =
+      static_cast<socklen_t>(CMSG_SPACE(sizeof(int)));
+  char cmsgSocket[kCmsgSocketSize];

[Robert Sesek, 2014/06/16 19:32:54]

naming: cmsg_socket

[Drew Haven, 2014/06/16 21:51:39]

Done.

+
+  msghdr message = {0};

[Robert Sesek, 2014/06/16 19:32:54]

Same, |struct msghdr|.

[Drew Haven, 2014/06/16 21:51:39]

Done.

+  message.msg_iov = io_vec;
+  message.msg_iovlen = sizeof(io_vec);
+  message.msg_control = cmsgSocket;
+  message.msg_controllen = kCmsgSocketSize;
+
+  ssize_t size = HANDLE_EINTR(recvmsg(parent_socket.get(), &message, 0));
+  if (size > 0) {
+    cmsghdr* cmsgSocketHeader = CMSG_FIRSTHDR(&message);

[Robert Sesek, 2014/06/16 19:32:53]

Same, |struct smsghdr|.

[Drew Haven, 2014/06/16 21:51:39]

Done.  Variable name as well.

+
+    if (cmsgSocketHeader && cmsgSocketHeader->cmsg_level == SOL_SOCKET &&
+        cmsgSocketHeader->cmsg_type == SCM_RIGHTS)
+      fd = *reinterpret_cast<int*>(CMSG_DATA(cmsgSocketHeader));
+  }
+
+  device_file_ = base::File(fd);
+
+  // Wait for the child.
+  int child_exit_status;
+  if (!base::WaitForExitCode(process_handle, &child_exit_status)) {
+    LOG(ERROR) << "Unable to wait for child.";
+    return false;
+  }
+
+  if (child_exit_status) {
+    LOG(ERROR) << "Child process returned failure.";
+    return false;
+  }
+
+  return device_file_.IsValid();
+}
+
+}  // namespace image_writer