Support UNC path capacity on Windows #22202

DoubleSpicy · 2025-01-24T22:04:46Z

Add UNC path capacity calculation capability by invoking Windows API directly.

For #21954,
Can we get a confirmation on linux as well?

DoubleSpicy · 2025-01-24T22:33:21Z

QT seems doesn't have full support of UNC paths in general, a workaround is to mount it as a drive, mentioned at PCSX2/pcsx2#6258 and https://forum.qt.io/topic/96418/how-to-create-a-folder-and-write-a-file-in-it-using-the-unc-path/2

src/gui/addnewtorrentdialog.cpp

DoubleSpicy · 2025-01-28T19:40:56Z

hi @glassez I have reworked this feature and added a bunch of testcases to avoid impacting normal path handling.

Chocobo1 · 2025-01-29T08:05:06Z

src/base/utils/fs.cpp

@@ -209,6 +209,17 @@ Path Utils::Fs::toValidPath(const QString &name, const QString &pad)

 qint64 Utils::Fs::freeDiskSpaceOnPath(const Path &path)
 {
+#if defined(Q_OS_WIN)


Is it possible to further simplify this PR?
I suppose you only need the following to make it work:

bool Path::isUNCPath() const
It will check if the path is a valid UNC path.

This code at Utils::Fs::freeDiskSpaceOnPath()

I especially would like to retain the old QString cleanPath(const QString &path) code if it won't block/get in the way of UNC paths.

Agree perhaps that the cleanPath(path) can be done in an more elegant way. Something like path.toStdWString().find_last_not_of(u"\\"_s)+1 can replace the loops.

Few tricky things to consider when distinguishing UNC paths from normal paths:

QDir::cleanPath is designed for "normal paths", it normalizes all back slashes into forward slashes and try to eliminate extra slashes.
\\host\drive\folder will become //host/drive/folder

PathIsUNCW() from win32 api in my 1st iteration is not reliable as well, it returns true whenever the string starts with double back slashes \\

Path::rootItem() and Path::parentPath() is required in queryFreeDiskSpace(const Path &path) in order to traverse through folders for capacity and create new folders when input path does not exist, but the current version depends on forward slashes /

Wouldn't it be better to just declare UNC paths officially unsupported?

src/base/path.cpp

glassez · 2025-01-30T09:02:35Z

src/base/path.h

@@ -51,6 +51,11 @@ class Path final
    bool isAbsolute() const;
    bool isRelative() const;

+#if defined(Q_OS_WIN)
+    bool isUNCPath() const;
+    QString getUNCRootPathStr() const;


I believe it is part of implementation.

I believe it is part of implementation.

So?

src/base/path.h

src/base/path.cpp

src/base/utils/fs.cpp

src/base/path.cpp

glassez · 2025-01-30T09:29:51Z

test/testpath.cpp

+
+        QCOMPARE(Path(uR"(\\nas01\drive)"_s).rootItem(), Path(uR"(\\nas01\drive)"_s));
+        QCOMPARE(Path(uR"(\\nas01\drive\xxx)"_s).rootItem(), Path(uR"(\\nas01\drive)"_s));
+        QCOMPARE(Path(uR"(\\nas01\drive\xxx\yyy)"_s).rootItem(), Path(uR"(\\nas01\drive)"_s));


Why \\nas01\drive is root item?

It is the ordinary usecase where we mount a network drive on windows, are there usecases where a UNC path is usable in form of \\host without specifying the share component?

I don't have a nas at home handy, the test is done by mounting 2 folder as network drive

C:\Users\Z>net use New connections will be remembered. Status Local Remote Network ------------------------------------------------------------------------------- OK X: \\mydesktop\mount1 Microsoft Windows Network OK Y: \\mydesktop\mount2 Microsoft Windows Network The command completed successfully.

edit: Found a doc from microsoft stating that it must have >= 2 components: https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-dfsc/149a3039-98ce-491a-9268-2f5ddef08192

Haven't done any tests with this PR yet, but here's what net use returns on my setup (xxx.xxx.xxx.xxx = IP) with 3x NAS connected.

C:\WINDOWS\system32>net use New connections will be remembered. Status Local Remote Network ------------------------------------------------------------------------------- OK T: \\xxx.xxx.xxx.xxx\Movies Microsoft Windows Network OK V: \\xxx.xxx.xxx.xxx\NAS3 Microsoft Windows Network OK W: \\xxx.xxx.xxx.xxx\Tv Shows Microsoft Windows Network The command completed successfully.

Why \\nas01\drive is root item?

Can \\servername\share not be used like the docs show?

Chocobo1

ps. Some preliminary review. Haven't done a full round.

Chocobo1 · 2025-01-30T15:06:39Z

src/base/path.cpp

+    if (isUNCPath())
+        return true;


Suggested change

if (isUNCPath())

return true;

#if defined(Q_OS_WIN)

if (isUNCPath())

return true;

#endif

Chocobo1 · 2025-01-30T15:11:00Z

src/base/path.cpp

    QString cleanPath(const QString &path)
    {
+#if defined(Q_OS_WIN)
+        // QT's cleanPath does not support UNC path
+        if (isQStrUNCPath(path))


IMO this is full validation which is too expensive here. You should use fast/lightweight checks instead. This function doesn't need validation for constructing paths.

Chocobo1 · 2025-01-30T15:16:08Z

src/base/path.cpp

+    bool isQStrUNCPath(const QString &path)
+    {
+        // strict format of \\host\drive\folder with no forbidden char to avoid conflict with normal path
+        if (path.left(2) != uR"(\\)"_s)


use QStringView::startsWith

Chocobo1 · 2025-01-30T15:16:31Z

src/base/path.cpp

+        // strict format of \\host\drive\folder with no forbidden char to avoid conflict with normal path
+        if (path.left(2) != uR"(\\)"_s)
+            return false;
+        const auto lastSlash = path.lastIndexOf(u'\\');


no auto here please.

Chocobo1 · 2025-01-30T15:16:48Z

src/base/path.cpp

+        const auto lastSlash = path.lastIndexOf(u'\\');
+        if ((lastSlash - 1) <= 2)
+            return false;
+        const QRegularExpression regex {u"[\\0-\\37:?\"*<>|:/]"_s}; // no drive letter allowed C:/


Suggested change

const QRegularExpression regex {u"[\\0-\\37:?\"*<>|:/]"_s}; // no drive letter allowed C:/

static const QRegularExpression regex {u"[\\0-\\37:?\"*<>|:/]"_s}; // no drive letter allowed C:/

Chocobo1 · 2025-01-30T15:17:36Z

src/base/path.cpp

+        if ((lastSlash - 1) <= 2)
+            return false;
+        const QRegularExpression regex {u"[\\0-\\37:?\"*<>|:/]"_s}; // no drive letter allowed C:/
+        return !regex.match(path.data()).hasMatch();


use QStringView::contains

Chocobo1 · 2025-01-30T15:24:31Z

src/base/path.cpp

    QString cleanPath(const QString &path)
    {
+#if defined(Q_OS_WIN)
+        // QT's cleanPath does not support UNC path


Another idea.
You could try to split the UNC path into 2 fields. First is host-name and the second is the rest of the path. host-name will have its own private QString variable in Path class and the second part will be stored in m_pathStr. The second part will look like a relative path.
This way you could reuse existing code and you only need to concat the host-name back when full path is expected in various methods.

https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-dtyp/62e862f4-2a51-452e-8eeb-dc4ff5ee33cc

Chocobo1 · 2025-01-30T15:28:29Z

src/base/path.cpp

@@ -52,8 +52,35 @@ const int PATHLIST_TYPEID = qRegisterMetaType<PathList>("PathList");

 namespace
 {
+#if defined(Q_OS_WIN)
+    bool isQStrUNCPath(const QString &path)


Try to use QStringView as input parameter type.

Chocobo1 · 2025-01-30T15:35:14Z

src/base/path.cpp

+            // only trim off trailing \ which is meaningless
+            int index = path.size();
+            while (path[index - 1] == u'\\')
+                --index;
+            if (index <= (path.size() - 1))
+                return path.left(index);
+            return path;


I don't really like this way. All paths are QDir::cleanPath processed except UNC paths. This creates discrepancy behavior which might create unforeseen surprises in the future.

Chocobo1 · 2025-01-30T15:38:47Z

src/base/path.h

+#if defined(Q_OS_WIN)
+    bool isUNCPath() const;
+    QString getUNCRootPathStr() const;
+#endif


Please move them to the bottom of public: section. To right before private: section.

glassez · 2025-01-30T16:59:03Z

src/base/path.cpp

@@ -52,8 +52,35 @@ const int PATHLIST_TYPEID = qRegisterMetaType<PathList>("PathList");

 namespace
 {
+#if defined(Q_OS_WIN)
+    bool isQStrUNCPath(const QString &path)


Suggested change

bool isQStrUNCPath(const QString &path)

bool isUNCPath(const QString &path)

Neustradamus · 2025-01-31T02:15:06Z

WinDirStat supports it, maybe you can look how it has been done:

https://github.com/search?q=repo%3Awindirstat%2Fwindirstat+unc&type=code

glassez changed the title ~~Support UNC path capacity on windows~~ Support UNC path capacity on Windows Jan 25, 2025

glassez reviewed Jan 25, 2025

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DoubleSpicy force-pushed the UNC branch 7 times, most recently from c66a932 to 4a58443 Compare January 28, 2025 19:39

DoubleSpicy force-pushed the UNC branch from 4a58443 to 2583114 Compare January 28, 2025 19:45

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DoubleSpicy force-pushed the UNC branch from 8cefbd8 to 19f3b8d Compare January 30, 2025 10:02

Support UNC path capacity on windows

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DoubleSpicy force-pushed the UNC branch from 19f3b8d to ccc2bad Compare January 30, 2025 10:37

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Support UNC path capacity on Windows #22202

Support UNC path capacity on Windows #22202

DoubleSpicy commented Jan 24, 2025 •

edited by glassez

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Neustradamus commented Jan 31, 2025

	const QRegularExpression regex {u"[\\0-\\37:?\"*<>\|:/]"_s}; // no drive letter allowed C:/
	static const QRegularExpression regex {u"[\\0-\\37:?\"*<>\|:/]"_s}; // no drive letter allowed C:/

	bool isQStrUNCPath(const QString &path)
	bool isUNCPath(const QString &path)

Support UNC path capacity on Windows #22202

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