Add disk writer tool.

3 files changed, 798 insertions, 0 deletions

diff --git a/src/tools/dcpomatic_disk.cc b/src/tools/dcpomatic_disk.cc
new file mode 100644
index 000000000..baccdbce3
--- /dev/null
+++ b/src/tools/dcpomatic_disk.cc
@@ -0,0 +1,309 @@
+/*
+    Copyright (C) 2019-2020 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+#include "wx/wx_signal_manager.h"
+#include "wx/wx_util.h"
+#include "wx/job_manager_view.h"
+#include "wx/drive_wipe_warning_dialog.h"
+#include "lib/file_log.h"
+#include "lib/dcpomatic_log.h"
+#include "lib/util.h"
+#include "lib/config.h"
+#include "lib/signal_manager.h"
+#include "lib/cross.h"
+#include "lib/copy_to_drive_job.h"
+#include "lib/job_manager.h"
+#include "lib/disk_writer_messages.h"
+#include <wx/wx.h>
+#include <boost/process.hpp>
+#ifdef DCPOMATIC_WINDOWS
+#include <boost/process/windows.hpp>
+#endif
+#ifdef DCPOMATIC_OSX
+#include <ApplicationServices/ApplicationServices.h>
+#endif
+
+using std::string;
+using std::exception;
+using std::cout;
+using std::cerr;
+using std::runtime_error;
+using boost::shared_ptr;
+
+class DOMFrame : public wxFrame
+{
+public:
+	explicit DOMFrame (wxString const & title)
+		: wxFrame (0, -1, title)
+		, _nanomsg (true)
+		, _sizer (new wxBoxSizer(wxVERTICAL))
+	{
+		/* Use a panel as the only child of the Frame so that we avoid
+		   the dark-grey background on Windows.
+		*/
+		wxPanel* overall_panel = new wxPanel (this);
+		wxSizer* s = new wxBoxSizer (wxHORIZONTAL);
+		s->Add (overall_panel, 1, wxEXPAND);
+		SetSizer (s);
+
+		wxGridBagSizer* grid = new wxGridBagSizer (DCPOMATIC_SIZER_X_GAP, DCPOMATIC_SIZER_Y_GAP);
+
+		int r = 0;
+		add_label_to_sizer (grid, overall_panel, _("DCP"), true, wxGBPosition(r, 0));
+		wxBoxSizer* dcp_name_sizer = new wxBoxSizer (wxHORIZONTAL);
+		_dcp_name = new wxStaticText (overall_panel, wxID_ANY, wxEmptyString);
+		dcp_name_sizer->Add (_dcp_name, 1, wxALIGN_CENTER_VERTICAL | wxRIGHT, DCPOMATIC_SIZER_X_GAP);
+		_dcp_open = new wxButton (overall_panel, wxID_ANY, _("Open..."));
+		dcp_name_sizer->Add (_dcp_open, 0);
+		grid->Add (dcp_name_sizer, wxGBPosition(r, 1), wxDefaultSpan, wxEXPAND);
+		++r;
+
+		add_label_to_sizer (grid, overall_panel, _("Drive"), true, wxGBPosition(r, 0));
+		wxBoxSizer* drive_sizer = new wxBoxSizer (wxHORIZONTAL);
+		_drive = new wxChoice (overall_panel, wxID_ANY);
+		drive_sizer->Add (_drive, 1, wxALIGN_CENTER_VERTICAL | wxRIGHT, DCPOMATIC_SIZER_X_GAP);
+		_drive_refresh = new wxButton (overall_panel, wxID_ANY, _("Refresh"));
+		drive_sizer->Add (_drive_refresh, 0);
+		grid->Add (drive_sizer, wxGBPosition(r, 1), wxDefaultSpan, wxEXPAND);
+		++r;
+
+		_jobs = new JobManagerView (overall_panel, false);
+		grid->Add (_jobs, wxGBPosition(r, 0), wxGBSpan(6, 2), wxEXPAND);
+		r += 6;
+
+		_copy = new wxButton (overall_panel, wxID_ANY, _("Copy DCP"));
+		grid->Add (_copy, wxGBPosition(r, 0), wxGBSpan(1, 2), wxEXPAND);
+		++r;
+
+		grid->AddGrowableCol (1);
+
+		_dcp_open->Bind (wxEVT_BUTTON, boost::bind(&DOMFrame::open, this));
+		_copy->Bind (wxEVT_BUTTON, boost::bind(&DOMFrame::copy, this));
+		_drive->Bind (wxEVT_CHOICE, boost::bind(&DOMFrame::setup_sensitivity, this));
+		_drive_refresh->Bind (wxEVT_BUTTON, boost::bind(&DOMFrame::drive_refresh, this));
+
+		_sizer->Add (grid, 1, wxALL | wxEXPAND, DCPOMATIC_DIALOG_BORDER);
+		overall_panel->SetSizer (_sizer);
+		Fit ();
+		SetSize (768, GetSize().GetHeight() + 32);
+
+		/* XXX: this is a hack, but I expect we'll need logs and I'm not sure if there's
+		 * a better place to put them.
+		 */
+		dcpomatic_log.reset(new FileLog(config_path() / "disk.log"));
+		dcpomatic_log->set_types (dcpomatic_log->types() | LogEntry::TYPE_DISK);
+		LOG_DISK_NC("dcpomatic_disk started");
+
+		drive_refresh ();
+
+		Bind (wxEVT_SIZE, boost::bind (&DOMFrame::sized, this, _1));
+
+		JobManager::instance()->ActiveJobsChanged.connect(boost::bind(&DOMFrame::setup_sensitivity, this));
+
+#ifdef DCPOMATIC_WINDOWS
+		/* We must use ::shell here, it seems, to avoid error code 740 (related to privilege escalation) */
+		LOG_DISK("Starting writer process %1", disk_writer_path().string());
+		_writer = new boost::process::child (disk_writer_path(), boost::process::shell, boost::process::windows::hide);
+#endif
+
+#ifdef DCPOMATIC_LINUX
+		LOG_DISK("Starting writer process %1", disk_writer_path().string());
+		_writer = new boost::process::child (disk_writer_path());
+#endif
+
+		/* _writer is always running on macOS at the moment */
+	}
+
+	~DOMFrame ()
+	{
+		_nanomsg.blocking_send(DISK_WRITER_QUIT "\n");
+	}
+
+private:
+	void sized (wxSizeEvent& ev)
+	{
+		_sizer->Layout ();
+		ev.Skip ();
+	}
+
+	void open ()
+	{
+		wxDirDialog* d = new wxDirDialog (this, _("Choose a DCP folder"), wxT(""), wxDD_DIR_MUST_EXIST);
+		int r = d->ShowModal ();
+		boost::filesystem::path const path (wx_to_std(d->GetPath()));
+		d->Destroy ();
+
+		if (r != wxID_OK) {
+			return;
+		}
+
+		_dcp_path = path;
+		_dcp_name->SetLabel (std_to_wx(_dcp_path->filename().string()));
+		setup_sensitivity ();
+	}
+
+	void copy ()
+	{
+		DCPOMATIC_ASSERT (_drive->GetSelection() != wxNOT_FOUND);
+		DCPOMATIC_ASSERT (static_cast<bool>(_dcp_path));
+		DriveWipeWarningDialog* d = new DriveWipeWarningDialog (this, _drive->GetString(_drive->GetSelection()));
+		int const r = d->ShowModal ();
+		bool ok = r == wxID_OK && d->confirmed();
+		d->Destroy ();
+
+		if (!ok) {
+			return;
+		}
+
+		JobManager::instance()->add(shared_ptr<Job>(new CopyToDriveJob(*_dcp_path, _drives[_drive->GetSelection()], _nanomsg)));
+		setup_sensitivity ();
+	}
+
+	void drive_refresh ()
+	{
+		int const sel = _drive->GetSelection ();
+		wxString current;
+		if (sel != wxNOT_FOUND) {
+			current = _drive->GetString (sel);
+		}
+		_drive->Clear ();
+		int re_select = wxNOT_FOUND;
+		int j = 0;
+		_drives.clear ();
+		BOOST_FOREACH (Drive i, get_drives()) {
+			if (!i.mounted()) {
+				_drives.push_back (i);
+			}
+		}
+		BOOST_FOREACH (Drive i, _drives) {
+			wxString const s = std_to_wx(i.description());
+			if (s == current) {
+				re_select = j;
+			}
+			_drive->Append(s);
+			++j;
+		}
+		_drive->SetSelection (re_select);
+		setup_sensitivity ();
+	}
+
+	void setup_sensitivity ()
+	{
+		_copy->Enable (static_cast<bool>(_dcp_path) && _drive->GetSelection() != wxNOT_FOUND && !JobManager::instance()->work_to_do());
+	}
+
+	wxStaticText* _dcp_name;
+	wxButton* _dcp_open;
+	wxChoice* _drive;
+	wxButton* _drive_refresh;
+	wxButton* _copy;
+	JobManagerView* _jobs;
+	boost::optional<boost::filesystem::path> _dcp_path;
+	std::vector<Drive> _drives;
+	boost::process::child* _writer;
+	Nanomsg _nanomsg;
+	wxSizer* _sizer;
+};
+
+class App : public wxApp
+{
+public:
+	App ()
+		: _frame (0)
+	{}
+
+	bool OnInit ()
+	{
+		try {
+			Config::FailedToLoad.connect (boost::bind (&App::config_failed_to_load, this));
+			Config::Warning.connect (boost::bind (&App::config_warning, this, _1));
+
+			SetAppName (_("DCP-o-matic Disk Writer"));
+
+			if (!wxApp::OnInit()) {
+				return false;
+			}
+
+#ifdef DCPOMATIC_LINUX
+			unsetenv ("UBUNTU_MENUPROXY");
+#endif
+
+#ifdef __WXOSX__
+			ProcessSerialNumber serial;
+			GetCurrentProcess (&serial);
+			TransformProcessType (&serial, kProcessTransformToForegroundApplication);
+#endif
+
+			dcpomatic_setup_path_encoding ();
+
+			/* Enable i18n; this will create a Config object
+			   to look for a force-configured language.  This Config
+			   object will be wrong, however, because dcpomatic_setup
+			   hasn't yet been called and there aren't any filters etc.
+			   set up yet.
+			*/
+			dcpomatic_setup_i18n ();
+
+			/* Set things up, including filters etc.
+			   which will now be internationalised correctly.
+			*/
+			dcpomatic_setup ();
+
+			/* Force the configuration to be re-loaded correctly next
+			   time it is needed.
+			*/
+			Config::drop ();
+
+			_frame = new DOMFrame (_("DCP-o-matic Disk Writer"));
+			SetTopWindow (_frame);
+
+			_frame->Show ();
+
+			signal_manager = new wxSignalManager (this);
+			Bind (wxEVT_IDLE, boost::bind (&App::idle, this, _1));
+		}
+		catch (exception& e)
+		{
+			error_dialog (0, wxString::Format ("DCP-o-matic could not start."), std_to_wx(e.what()));
+		}
+
+		return true;
+	}
+
+	void config_failed_to_load ()
+	{
+		message_dialog (_frame, _("The existing configuration failed to load.  Default values will be used instead.  These may take a short time to create."));
+	}
+
+	void config_warning (string m)
+	{
+		message_dialog (_frame, std_to_wx(m));
+	}
+
+	void idle (wxIdleEvent& ev)
+	{
+		signal_manager->ui_idle ();
+		ev.Skip ();
+	}
+
+	DOMFrame* _frame;
+};
+
+IMPLEMENT_APP (App)
diff --git a/src/tools/dcpomatic_disk_writer.cc b/src/tools/dcpomatic_disk_writer.cc
new file mode 100644
index 000000000..0bd5dcbc4
--- /dev/null
+++ b/src/tools/dcpomatic_disk_writer.cc
@@ -0,0 +1,474 @@
+/*
+    Copyright (C) 2019-2020 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+#include "lib/disk_writer_messages.h"
+#include "lib/compose.hpp"
+#include "lib/exceptions.h"
+#include "lib/cross.h"
+#include "lib/digester.h"
+#include "lib/file_log.h"
+#include "lib/dcpomatic_log.h"
+#include "lib/nanomsg.h"
+extern "C" {
+#include <lwext4/ext4_mbr.h>
+#include <lwext4/ext4_fs.h>
+#include <lwext4/ext4_mkfs.h>
+#include <lwext4/ext4_errno.h>
+#include <lwext4/ext4_debug.h>
+#include <lwext4/ext4.h>
+}
+
+#ifdef DCPOMATIC_POSIX
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#endif
+
+#ifdef DCPOMATIC_OSX
+#undef nil
+extern "C" {
+#include <lwext4/file_dev.h>
+}
+#endif
+
+#ifdef DCPOMATIC_LINUX
+#include <linux/fs.h>
+#include <polkit/polkit.h>
+extern "C" {
+#include <lwext4/file_dev.h>
+}
+#include <poll.h>
+#endif
+
+#ifdef DCPOMATIC_WINDOWS
+extern "C" {
+#include <lwext4/file_windows.h>
+}
+#endif
+
+#include <glibmm.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <boost/filesystem.hpp>
+#include <boost/algorithm/string.hpp>
+#include <iostream>
+
+using std::cin;
+using std::min;
+using std::string;
+using std::runtime_error;
+using std::exception;
+using boost::optional;
+
+#ifdef DCPOMATIC_LINUX
+static PolkitAuthority* polkit_authority = 0;
+#endif
+static boost::filesystem::path dcp_path;
+static std::string device;
+static uint64_t const block_size = 4096;
+static Nanomsg* nanomsg = 0;
+
+static
+void
+count (boost::filesystem::path dir, uint64_t& total_bytes)
+{
+	using namespace boost::filesystem;
+	for (directory_iterator i = directory_iterator(dir); i != directory_iterator(); ++i) {
+		if (is_directory(*i)) {
+			count (*i, total_bytes);
+		} else {
+			total_bytes += file_size (*i);
+		}
+	}
+}
+
+static
+string
+write (boost::filesystem::path from, boost::filesystem::path to, uint64_t& total_remaining, uint64_t total)
+{
+	ext4_file out;
+	int r = ext4_fopen(&out, to.generic_string().c_str(), "wb");
+	if (r != EOK) {
+		throw CopyError (String::compose("Failed to open file %1", to.generic_string()), r);
+	}
+
+	FILE* in = fopen_boost (from, "rb");
+	if (!in) {
+		ext4_fclose (&out);
+		throw CopyError (String::compose("Failed to open file %1", from.string()), 0);
+	}
+
+	uint8_t* buffer = new uint8_t[block_size];
+	Digester digester;
+
+	uint64_t remaining = file_size (from);
+	while (remaining > 0) {
+		uint64_t const this_time = min(remaining, block_size);
+		size_t read = fread (buffer, 1, this_time, in);
+		if (read != this_time) {
+			fclose (in);
+			ext4_fclose (&out);
+			delete[] buffer;
+			throw CopyError (String::compose("Short read; expected %1 but read %2", this_time, read), 0);
+		}
+
+		digester.add (buffer, this_time);
+
+		size_t written;
+		r = ext4_fwrite (&out, buffer, this_time, &written);
+		if (r != EOK) {
+			fclose (in);
+			ext4_fclose (&out);
+			delete[] buffer;
+			throw CopyError ("Write failed", r);
+		}
+		if (written != this_time) {
+			fclose (in);
+			ext4_fclose (&out);
+			delete[] buffer;
+			throw CopyError (String::compose("Short write; expected %1 but wrote %2", this_time, written), 0);
+		}
+		remaining -= this_time;
+		total_remaining -= this_time;
+		nanomsg->blocking_send(String::compose(DISK_WRITER_PROGRESS "\n%1\n", (1 - float(total_remaining) / total)));
+	}
+
+	fclose (in);
+	ext4_fclose (&out);
+	delete[] buffer;
+
+	return digester.get ();
+}
+
+static
+string
+read (boost::filesystem::path from, boost::filesystem::path to, uint64_t& total_remaining, uint64_t total)
+{
+	ext4_file in;
+	LOG_DISK("Opening %1 for read", to.generic_string());
+	int r = ext4_fopen(&in, to.generic_string().c_str(), "rb");
+	if (r != EOK) {
+		throw VerifyError (String::compose("Failed to open file %1", to.generic_string()), r);
+	}
+	LOG_DISK("Opened %1 for read", to.generic_string());
+
+	uint8_t* buffer = new uint8_t[block_size];
+	Digester digester;
+
+	uint64_t remaining = file_size (from);
+	while (remaining > 0) {
+		uint64_t const this_time = min(remaining, block_size);
+		size_t read;
+		r = ext4_fread (&in, buffer, this_time, &read);
+		if (read != this_time) {
+			ext4_fclose (&in);
+			delete[] buffer;
+			throw VerifyError (String::compose("Short read; expected %1 but read %2", this_time, read), 0);
+		}
+
+		digester.add (buffer, this_time);
+		remaining -= this_time;
+		total_remaining -= this_time;
+		nanomsg->blocking_send(String::compose(DISK_WRITER_PROGRESS "\n%1\n", (1 - float(total_remaining) / total)));
+	}
+
+	ext4_fclose (&in);
+	delete[] buffer;
+
+	return digester.get ();
+}
+
+
+/** @param from File to copy from.
+ *  @param to Directory to copy to.
+ */
+static
+void
+copy (boost::filesystem::path from, boost::filesystem::path to, uint64_t& total_remaining, uint64_t total)
+{
+	LOG_DISK ("Copy %1 -> %2", from.string(), to.generic_string());
+
+	using namespace boost::filesystem;
+
+	path const cr = to / from.filename();
+
+	if (is_directory(from)) {
+		int r = ext4_dir_mk (cr.generic_string().c_str());
+		if (r != EOK) {
+			throw CopyError (String::compose("Failed to create directory %1", cr.generic_string()), r);
+		}
+
+		for (directory_iterator i = directory_iterator(from); i != directory_iterator(); ++i) {
+			copy (i->path(), cr, total_remaining, total);
+		}
+	} else {
+		string const write_digest = write (from, cr, total_remaining, total);
+		LOG_DISK ("Wrote %1 %2 with %3", from.string(), cr.generic_string(), write_digest);
+		string const read_digest = read (from, cr, total_remaining, total);
+		LOG_DISK ("Read %1 %2 with %3", from.string(), cr.generic_string(), write_digest);
+		if (write_digest != read_digest) {
+			throw VerifyError ("Hash of written data is incorrect", 0);
+		}
+	}
+}
+
+static
+void
+write ()
+try
+{
+//	ext4_dmask_set (DEBUG_ALL);
+
+	/* We rely on static initialization for these */
+	static struct ext4_fs fs;
+	static struct ext4_mkfs_info info;
+	info.block_size = 1024;
+	info.inode_size = 128;
+	info.journal = false;
+
+#ifdef WIN32
+	file_windows_name_set(device.c_str());
+	struct ext4_blockdev* bd = file_windows_dev_get();
+#else
+	file_dev_name_set (device.c_str());
+	struct ext4_blockdev* bd = file_dev_get ();
+#endif
+
+	if (!bd) {
+		throw CopyError ("Failed to open drive", 0);
+	}
+	LOG_DISK_NC ("Opened drive");
+
+	struct ext4_mbr_parts parts;
+	parts.division[0] = 100;
+	parts.division[1] = 0;
+	parts.division[2] = 0;
+	parts.division[3] = 0;
+
+#ifdef DCPOMATIC_LINUX
+	PrivilegeEscalator e;
+#endif
+
+	/* XXX: not sure if disk_id matters */
+	int r = ext4_mbr_write (bd, &parts, 0);
+
+	if (r) {
+		throw CopyError ("Failed to write MBR", r);
+	}
+	LOG_DISK_NC ("Wrote MBR");
+
+#ifdef DCPOMATIC_WINDOWS
+	struct ext4_mbr_bdevs bdevs;
+	r = ext4_mbr_scan (bd, &bdevs);
+	if (r != EOK) {
+		throw CopyError ("Failed to read MBR", r);
+	}
+
+	file_windows_partition_set (bdevs.partitions[0].part_offset, bdevs.partitions[0].part_size);
+#endif
+
+#ifdef DCPOMATIC_LINUX
+	/* Re-read the partition table */
+	int fd = open(device.c_str(), O_RDONLY);
+	ioctl(fd, BLKRRPART, NULL);
+	close(fd);
+#endif
+
+#ifdef DCPOMATIC_LINUX
+	string partition = device;
+	/* XXX: don't know if this logic is sensible */
+	if (partition.size() > 0 && isdigit(partition[partition.length() - 1])) {
+		partition += "p1";
+	} else {
+		partition += "1";
+	}
+	file_dev_name_set (partition.c_str());
+	bd = file_dev_get ();
+#endif
+
+#ifdef DCPOMATIC_OSX
+	string partition = device + "s1";
+	file_dev_name_set (partition.c_str());
+	bd = file_dev_get ();
+#endif
+
+	if (!bd) {
+		throw CopyError ("Failed to open partition", 0);
+	}
+	LOG_DISK_NC ("Opened partition");
+
+	nanomsg->blocking_send(DISK_WRITER_FORMATTING "\n");
+
+	r = ext4_mkfs(&fs, bd, &info, F_SET_EXT4);
+	if (r != EOK) {
+		throw CopyError ("Failed to make filesystem", r);
+	}
+	LOG_DISK_NC ("Made filesystem");
+
+	r = ext4_device_register(bd, "ext4_fs");
+	if (r != EOK) {
+		throw CopyError ("Failed to register device", r);
+	}
+	LOG_DISK_NC ("Registered device");
+
+	r = ext4_mount("ext4_fs", "/mp/", false);
+	if (r != EOK) {
+		throw CopyError ("Failed to mount device", r);
+	}
+	LOG_DISK_NC ("Mounted device");
+
+	uint64_t total_bytes = 0;
+	count (dcp_path, total_bytes);
+
+	/* XXX: this is a hack.  We are going to "treat" every byte twice; write it, and then verify it.  Double the
+	 * bytes totals so that progress works itself out (assuming write is the same speed as read).
+	 */
+	total_bytes *= 2;
+	copy (dcp_path, "/mp", total_bytes, total_bytes);
+
+	r = ext4_umount("/mp/");
+	if (r != EOK) {
+		throw CopyError ("Failed to unmount device", r);
+	}
+
+	ext4_device_unregister("ext4_fs");
+	nanomsg->blocking_send(DISK_WRITER_OK "\n");
+} catch (CopyError& e) {
+	LOG_DISK("CopyError: %1 %2", e.message(), e.number());
+	nanomsg->blocking_send(String::compose(DISK_WRITER_ERROR "\n%1\n%2\n", e.message(), e.number()));
+} catch (VerifyError& e) {
+	LOG_DISK("VerifyError: %1 %2", e.message(), e.number());
+	nanomsg->blocking_send(String::compose(DISK_WRITER_ERROR "\n%1\n%2\n", e.message(), e.number()));
+} catch (exception& e) {
+	LOG_DISK("Exception: %1", e.what());
+	nanomsg->blocking_send(String::compose(DISK_WRITER_ERROR "\n%1\n0\n", e.what()));
+}
+
+#ifdef DCPOMATIC_LINUX
+static
+void
+polkit_callback (GObject *, GAsyncResult* res, gpointer)
+{
+	PolkitAuthorizationResult* result = polkit_authority_check_authorization_finish (polkit_authority, res, 0);
+	if (result && polkit_authorization_result_get_is_authorized(result)) {
+		write ();
+	}
+	if (result) {
+		g_object_unref (result);
+	}
+}
+#endif
+
+bool
+idle ()
+{
+	using namespace boost::algorithm;
+
+	optional<string> s = nanomsg->nonblocking_get ();
+	if (!s) {
+		return true;
+	}
+
+	if (*s == "Q") {
+		exit (EXIT_SUCCESS);
+	} else if (*s == "W") {
+		dcp_path = nanomsg->blocking_get();
+		device = nanomsg->blocking_get();
+
+		/* Do some basic sanity checks; this is a bit belt-and-braces but it can't hurt... */
+
+#ifdef DCPOMATIC_OSX
+		if (!starts_with(device, "/dev/disk")) {
+			LOG_DISK ("Will not write to %1", device);
+			nanomsg->blocking_send(DISK_WRITER_ERROR "\nRefusing to write to this drive\n1\n");
+			return true;
+		}
+#endif
+#ifdef DCPOMATIC_LINUX
+		if (!starts_with(device, "/dev/sd") && !starts_with(device, "/dev/hd")) {
+			LOG_DISK ("Will not write to %1", device);
+			nanomsg->blocking_send(DISK_WRITER_ERROR "\nRefusing to write to this drive\n1\n");
+			return true;
+		}
+#endif
+#ifdef DCPOMATIC_WINDOWS
+		if (!starts_with(device, "\\\\.\\PHYSICALDRIVE")) {
+			LOG_DISK ("Will not write to %1", device);
+			nanomsg->blocking_send(DISK_WRITER_ERROR "\nRefusing to write to this drive\n1\n");
+			return true;
+		}
+#endif
+
+		bool on_drive_list = false;
+		bool mounted = false;
+		for (auto const& i: get_drives()) {
+			if (i.internal_name() == device) {
+				on_drive_list = true;
+				mounted = i.mounted();
+			}
+		}
+
+		if (!on_drive_list) {
+			LOG_DISK ("Will not write to %1 as it's not recognised as a drive", device);
+			nanomsg->blocking_send(DISK_WRITER_ERROR "\nRefusing to write to this drive\n1\n");
+			return true;
+		}
+		if (mounted) {
+			LOG_DISK ("Will not write to %1 as it's mounted", device);
+			nanomsg->blocking_send(DISK_WRITER_ERROR "\nRefusing to write to this drive\n1\n");
+			return true;
+		}
+
+		LOG_DISK ("Here we go writing %1 to %2", dcp_path, device);
+
+#ifdef DCPOMATIC_LINUX
+		polkit_authority = polkit_authority_get_sync (0, 0);
+		PolkitSubject* subject = polkit_unix_process_new (getppid());
+		polkit_authority_check_authorization (
+				polkit_authority, subject, "com.dcpomatic.write-drive", 0, POLKIT_CHECK_AUTHORIZATION_FLAGS_ALLOW_USER_INTERACTION, 0, polkit_callback, 0
+				);
+#else
+		write ();
+#endif
+	}
+
+	return true;
+}
+
+int
+main ()
+{
+	/* XXX: this is a hack, but I expect we'll need logs and I'm not sure if there's
+	 * a better place to put them.
+	 */
+	dcpomatic_log.reset(new FileLog(config_path() / "disk_writer.log", LogEntry::TYPE_DISK));
+	LOG_DISK_NC("dcpomatic_disk_writer started");
+
+	try {
+		nanomsg = new Nanomsg (false);
+	} catch (runtime_error& e) {
+		LOG_DISK_NC("Could not set up nanomsg socket");
+		exit (EXIT_FAILURE);
+	}
+
+	Glib::RefPtr<Glib::MainLoop> ml = Glib::MainLoop::create ();
+	Glib::signal_timeout().connect(sigc::ptr_fun(&idle), 500);
+	ml->run ();
+}
diff --git a/src/tools/wscript b/src/tools/wscript
index 8af9e7589..c7c953a31 100644
--- a/src/tools/wscript
+++ b/src/tools/wscript
@@ -32,8 +32,15 @@ def build(bld):
     uselib += 'AVUTIL SWSCALE SWRESAMPLE POSTPROC CURL BOOST_FILESYSTEM SSH ZIP CAIROMM FONTCONFIG PANGOMM SUB '
     uselib += 'SNDFILE SAMPLERATE BOOST_REGEX ICU NETTLE RTAUDIO PNG '
 
+    if bld.env.ENABLE_DISK:
+        if bld.env.TARGET_LINUX:
+            uselib += 'POLKIT '
+        uselib += 'LWEXT4 NANOMSG '
+
     if bld.env.TARGET_WINDOWS:
         uselib += 'WINSOCK2 DBGHELP SHLWAPI MSWSOCK BOOST_LOCALE WINSOCK2 OLE32 DSOUND WINMM KSUSER '
+    if bld.env.TARGET_LINUX:
+        uselib += 'DL '
 
     cli_tools = []
     if bld.env.VARIANT == 'swaroop-theater':
@@ -42,6 +49,8 @@ def build(bld):
         cli_tools = ['dcpomatic_cli', 'dcpomatic_server_cli', 'server_test', 'dcpomatic_kdm_cli', 'dcpomatic_create', 'swaroop_dcpomatic_ecinema', 'swaroop_dcpomatic_uuid']
     else:
         cli_tools = ['dcpomatic_cli', 'dcpomatic_server_cli', 'server_test', 'dcpomatic_kdm_cli', 'dcpomatic_create']
+        if bld.env.ENABLE_DISK:
+            cli_tools.append('dcpomatic_disk_writer')
 
     for t in cli_tools:
         obj = bld(features='cxx cxxprogram')
@@ -49,6 +58,10 @@ def build(bld):
         obj.includes = ['..']
         obj.use    = ['libdcpomatic2']
         obj.source = '%s.cc' % t
+        if bld.env.TARGET_WINDOWS and t == 'dcpomatic_disk_writer':
+            obj.source += ' ../../platform/windows/%s.rc' % t
+            # Prevent a console window opening when we start dcpomatic2_disk_writer
+            bld.env.LINKFLAGS.append('-Wl,-subsystem,windows')
         obj.target = t.replace('dcpomatic', 'dcpomatic2').replace('swaroop_', '')
         if t == 'server_test':
             obj.install_path = None
@@ -61,6 +74,8 @@ def build(bld):
             gui_tools = ['dcpomatic', 'dcpomatic_batch', 'dcpomatic_server', 'dcpomatic_kdm', 'dcpomatic_player', 'swaroop_dcpomatic_playlist']
         else:
             gui_tools = ['dcpomatic', 'dcpomatic_batch', 'dcpomatic_server', 'dcpomatic_kdm', 'dcpomatic_player', 'dcpomatic_playlist']
+            if bld.env.ENABLE_DISK:
+                gui_tools.append('dcpomatic_disk')
 
     for t in gui_tools:
         obj = bld(features='cxx cxxprogram')