Files: Added support for creating and reading relative or special path symbolic link files

modules/juce_core/files/juce_File.cpp

@@ -941,7 +941,9 @@ File File::createTempFile (StringRef fileNameEnding)
     return tempFile;
 }
 
-bool File::createSymbolicLink (const File& linkFileToCreate, bool overwriteExisting) const
+bool File::createSymbolicLink (const File& linkFileToCreate,
+                               const String& nativePathOfTarget,
+                               bool overwriteExisting)
 {
     if (linkFileToCreate.exists())
     {
@@ -959,7 +961,7 @@ bool File::createSymbolicLink (const File& linkFileToCreate, bool overwriteExist
 
    #if JUCE_MAC || JUCE_LINUX
     // one common reason for getting an error here is that the file already exists
-    if (symlink (fullPath.toRawUTF8(), linkFileToCreate.getFullPathName().toRawUTF8()) == -1)
+    if (symlink (nativePathOfTarget.toRawUTF8(), linkFileToCreate.getFullPathName().toRawUTF8()) == -1)
     {
         jassertfalse;
         return false;
@@ -967,15 +969,32 @@ bool File::createSymbolicLink (const File& linkFileToCreate, bool overwriteExist
 
     return true;
    #elif JUCE_MSVC
+    File targetFile (linkFileToCreate.getSiblingFile (nativePathOfTarget));
+
     return CreateSymbolicLink (linkFileToCreate.getFullPathName().toWideCharPointer(),
-                               fullPath.toWideCharPointer(),
-                               isDirectory() ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0) != FALSE;
+                               nativePathOfTarget.toWideCharPointer(),
+                               targetFile.isDirectory() ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0) != FALSE;
    #else
     jassertfalse; // symbolic links not supported on this platform!
     return false;
    #endif
 }
 
+bool File::createSymbolicLink (const File& linkFileToCreate, bool overwriteExisting) const
+{
+    return createSymbolicLink (linkFileToCreate, getFullPathName(), overwriteExisting);
+}
+
+#if ! JUCE_WINDOWS
+File File::getLinkedTarget() const
+{
+    if (isSymbolicLink())
+        return getSiblingFile (getNativeLinkedTarget());
+
+    return *this;
+}
+#endif
+
 //==============================================================================
 MemoryMappedFile::MemoryMappedFile (const File& file, MemoryMappedFile::AccessMode mode, bool exclusive)
     : range (0, file.getSize())

modules/juce_core/files/juce_File.h

@@ -987,12 +987,27 @@ public:
     */
     File getLinkedTarget() const;
 
+    /** Create a symbolic link to a native path and return a boolean to indicate success.
+
+        Use this method if you want to create a link to a relative path or a special native
+        file path (such as a device file on Windows).
+    */
+    static bool createSymbolicLink (const File& linkFileToCreate,
+                                    const String& nativePathOfTarget,
+                                    bool overwriteExisting);
+
+    /** This returns the native path that the symbolic link points to. The returned path
+        is a native path of the current OS and can be a relative, absolute or special path. */
+    String getNativeLinkedTarget() const;
+
    #if JUCE_WINDOWS || DOXYGEN
     /** Windows ONLY - Creates a win32 .LNK shortcut file that links to this file. */
     bool createShortcut (const String& description, const File& linkFileToCreate) const;
 
     /** Windows ONLY - Returns true if this is a win32 .LNK file. */
     bool isShortcut() const;
+   #else
+
    #endif
 
     //==============================================================================

modules/juce_core/native/juce_BasicNativeHeaders.h

@@ -143,6 +143,7 @@
  #include <shlobj.h>
  #include <shlwapi.h>
  #include <mmsystem.h>
+ #include <winioctl.h>
 
  #if JUCE_MINGW
   #include <basetyps.h>

modules/juce_core/native/juce_linux_CommonFile.cpp

@@ -55,26 +55,16 @@ bool File::isHidden() const
     return getFileName().startsWithChar ('.');
 }
 
-static String getLinkedFile (const String& file)
-{
-    HeapBlock<char> buffer (8194);
-    const int numBytes = (int) readlink (file.toRawUTF8(), buffer, 8192);
-    return String::fromUTF8 (buffer, jmax (0, numBytes));
-}
-
 bool File::isSymbolicLink() const
 {
-    return getLinkedFile (getFullPathName()).isNotEmpty();
+    return getNativeLinkedTarget().isNotEmpty();
 }
 
-File File::getLinkedTarget() const
+String File::getNativeLinkedTarget() const
 {
-    String f (getLinkedFile (getFullPathName()));
-
-    if (f.isNotEmpty())
-        return getSiblingFile (f);
-
-    return *this;
+    HeapBlock<char> buffer (8194);
+    const int numBytes = (int) readlink (getFullPathName().toRawUTF8(), buffer, 8192);
+    return String::fromUTF8 (buffer, jmax (0, numBytes));
 }
 
 //==============================================================================

modules/juce_core/native/juce_mac_Files.mm

@@ -281,12 +281,12 @@ bool File::isSymbolicLink() const
     return getFileLink (fullPath) != nil;
 }
 
-File File::getLinkedTarget() const
+String File::getNativeLinkedTarget() const
 {
     if (NSString* dest = getFileLink (fullPath))
-        return getSiblingFile (nsStringToJuce (dest));
+        return nsStringToJuce (dest);
 
-    return *this;
+    return {};
 }
 
 //==============================================================================

modules/juce_core/native/juce_win32_Files.cpp

@@ -30,6 +30,36 @@ namespace juce
 //==============================================================================
 namespace WindowsFileHelpers
 {
+    //==============================================================================
+   #if JUCE_WINDOWS
+    typedef struct _REPARSE_DATA_BUFFER {
+      ULONG  ReparseTag;
+      USHORT ReparseDataLength;
+      USHORT Reserved;
+      union {
+        struct {
+          USHORT SubstituteNameOffset;
+          USHORT SubstituteNameLength;
+          USHORT PrintNameOffset;
+          USHORT PrintNameLength;
+          ULONG  Flags;
+          WCHAR  PathBuffer[1];
+        } SymbolicLinkReparseBuffer;
+        struct {
+          USHORT SubstituteNameOffset;
+          USHORT SubstituteNameLength;
+          USHORT PrintNameOffset;
+          USHORT PrintNameLength;
+          WCHAR  PathBuffer[1];
+        } MountPointReparseBuffer;
+        struct {
+          UCHAR DataBuffer[1];
+        } GenericReparseBuffer;
+      } DUMMYUNIONNAME;
+    } *PREPARSE_DATA_BUFFER, REPARSE_DATA_BUFFER;
+   #endif
+
+    //==============================================================================
     DWORD getAtts (const String& path) noexcept
     {
         return GetFileAttributes (path.toWideCharPointer());
@@ -666,9 +696,104 @@ bool File::isShortcut() const
     return hasFileExtension (".lnk");
 }
 
-File File::getLinkedTarget() const
+static String readWindowsLnkFile (File lnkFile, bool wantsAbsolutePath)
+{
+    if (! lnkFile.exists())
+        lnkFile = File (lnkFile.getFullPathName() + ".lnk");
+
+    if (lnkFile.exists())
+    {
+        ComSmartPtr<IShellLink> shellLink;
+        ComSmartPtr<IPersistFile> persistFile;
+
+        if (SUCCEEDED (shellLink.CoCreateInstance (CLSID_ShellLink))
+             && SUCCEEDED (shellLink.QueryInterface (persistFile))
+             && SUCCEEDED (persistFile->Load (lnkFile.getFullPathName().toWideCharPointer(), STGM_READ))
+             && (! wantsAbsolutePath || SUCCEEDED (shellLink->Resolve (0, SLR_ANY_MATCH | SLR_NO_UI))))
+        {
+            WIN32_FIND_DATA winFindData;
+            WCHAR resolvedPath [MAX_PATH];
+
+            DWORD flags = SLGP_UNCPRIORITY;
+
+            if (! wantsAbsolutePath)
+                flags |= SLGP_RAWPATH;
+
+            if (SUCCEEDED (shellLink->GetPath (resolvedPath, MAX_PATH, &winFindData, flags)))
+                return resolvedPath;
+        }
+    }
+
+    return {};
+}
+
+static String readWindowsShortcutOrLink (const File& shortcut, bool wantsAbsolutePath)
 {
    #if JUCE_WINDOWS
+    if (! wantsAbsolutePath)
+    {
+        HANDLE h = CreateFile (shortcut.getFullPathName().toWideCharPointer(),
+                               GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING,
+                               FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
+                               0);
+
+        if (h != INVALID_HANDLE_VALUE)
+        {
+            HeapBlock<WindowsFileHelpers::REPARSE_DATA_BUFFER> reparseData;
+
+            reparseData.calloc (1, MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
+            DWORD bytesReturned = 0;
+
+            bool success = DeviceIoControl (h, FSCTL_GET_REPARSE_POINT, nullptr, 0,
+                                            reparseData.getData(), MAXIMUM_REPARSE_DATA_BUFFER_SIZE,
+                                            &bytesReturned, nullptr) != 0;
+             CloseHandle (h);
+
+            if (success)
+            {
+                if (IsReparseTagMicrosoft (reparseData->ReparseTag))
+                {
+                    String targetPath;
+
+                    switch (reparseData->ReparseTag)
+                    {
+                        case IO_REPARSE_TAG_SYMLINK:
+                        {
+                            auto& symlinkData = reparseData->SymbolicLinkReparseBuffer;
+                            targetPath = {symlinkData.PathBuffer + (symlinkData.SubstituteNameOffset / sizeof (WCHAR)),
+                                          symlinkData.SubstituteNameLength / sizeof (WCHAR)};
+                        }
+                        break;
+
+                        case IO_REPARSE_TAG_MOUNT_POINT:
+                        {
+                            auto& mountData = reparseData->MountPointReparseBuffer;
+                            targetPath = {mountData.PathBuffer + (mountData.SubstituteNameOffset / sizeof (WCHAR)),
+                                          mountData.SubstituteNameLength / sizeof (WCHAR)};
+                        }
+                        break;
+
+                        default:
+                            break;
+                    }
+
+                    if (targetPath.isNotEmpty())
+                    {
+                        const StringRef prefix ("\\??\\");
+
+                        if (targetPath.startsWith (prefix))
+                            targetPath = targetPath.substring (prefix.length());
+
+                        return targetPath;
+                    }
+                }
+            }
+        }
+    }
+
+    if (! wantsAbsolutePath)
+        return readWindowsLnkFile (shortcut, false);
+
     typedef DWORD (WINAPI* GetFinalPathNameByHandleFunc) (HANDLE, LPTSTR, DWORD, DWORD);
 
     static GetFinalPathNameByHandleFunc getFinalPathNameByHandle
@@ -676,7 +801,7 @@ File File::getLinkedTarget() const
 
     if (getFinalPathNameByHandle != nullptr)
     {
-        HANDLE h = CreateFile (getFullPathName().toWideCharPointer(),
+        HANDLE h = CreateFile (shortcut.getFullPathName().toWideCharPointer(),
                                GENERIC_READ, FILE_SHARE_READ, nullptr,
                                OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, 0);
 
@@ -695,8 +820,7 @@ File File::getLinkedTarget() const
 
                     // It turns out that GetFinalPathNameByHandleW prepends \\?\ to the path.
                     // This is not a bug, it's feature. See MSDN for more information.
-                    return File (path.startsWith (prefix) ? path.substring (prefix.length())
-                                                          : path);
+                    return path.startsWith (prefix) ? path.substring (prefix.length()) : path;
                 }
             }
 
@@ -705,30 +829,18 @@ File File::getLinkedTarget() const
     }
    #endif
 
-    File result (*this);
-    String p (getFullPathName());
-
-    if (! exists())
-        p += ".lnk";
-    else if (! hasFileExtension (".lnk"))
-        return result;
-
-    ComSmartPtr<IShellLink> shellLink;
-    ComSmartPtr<IPersistFile> persistFile;
-
-    if (SUCCEEDED (shellLink.CoCreateInstance (CLSID_ShellLink))
-         && SUCCEEDED (shellLink.QueryInterface (persistFile))
-         && SUCCEEDED (persistFile->Load (p.toWideCharPointer(), STGM_READ))
-         && SUCCEEDED (shellLink->Resolve (0, SLR_ANY_MATCH | SLR_NO_UI)))
-    {
-        WIN32_FIND_DATA winFindData;
-        WCHAR resolvedPath [MAX_PATH];
+    // as last resort try the resolve method of the ShellLink
+    return readWindowsLnkFile (shortcut, true);
+}
 
-        if (SUCCEEDED (shellLink->GetPath (resolvedPath, MAX_PATH, &winFindData, SLGP_UNCPRIORITY)))
-            result = File (resolvedPath);
-    }
+String File::getNativeLinkedTarget() const
+{
+    return readWindowsShortcutOrLink (*this, false);
+}
 
-    return result;
+File File::getLinkedTarget() const
+{
+    return readWindowsShortcutOrLink (*this, true);
 }
 
 bool File::createShortcut (const String& description, const File& linkFileToCreate) const