Pour un processus prenant en charge les longs chemins sur Windows 10, j'essaie de comprendre quelles sont les restrictions d'argument lors de l'utilisation de la méthode shell Windows PathRelativePathTo .
Dans mon exemple ci-dessous, j'utilise C # via pinvoke pour appeler la méthode.
J'ai donné plusieurs exemples ci-dessous et leur sortie. Remarque:
- Tous les exemples donnent des chemins de répertoire pour "de" et des chemins de fichier pour "vers" (aucun de ces chemins n'existe réellement sur le disque)
- Mes observations sont que
- Les chemins sous la longueur "courte" MAX_PATH (260) renvoient le succès avec le résultat attendu.
- Certains chemins sur le "court" MAX_PATH renvoient le succès avec le résultat correct.
- Certains chemins sur le "court" MAX_PATH retournent le succès avec la mauvaise réponse (ouais!)
- Certains chemins beaucoup plus longs renvoient une erreur. Cependant, il n'est pas à une certaine longueur maximale fixe.
La source:
class Program
{
static class Native
{
// https://www.pinvoke.net/default.aspx/shlwapi.pathrelativepathto
// https://docs.microsoft.com/en-us/windows/win32/api/shlwapi/nf-shlwapi-pathrelativepathtoa
[DllImport("shlwapi.dll", SetLastError = true, CharSet = CharSet.Auto)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern bool PathRelativePathTo([Out] StringBuilder pszPath, [In] string pszFrom, [In] int dwAttrFrom, [In] string pszTo, [In] int dwAttrTo);
}
static void Main(string[] args)
{
string pszFrom, pszTo;
int i = 0;
// #1 At "short" max path (259)
// Succeeds with right answer
pszFrom = @"c:\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCD123456789";
pszTo = @"c:\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCD123456789\abcdefghijklmnop.txt";
TestPathRelativePathTo(++i, pszFrom, pszTo);
// #2 One over "short" max path
// Succeeds with right answer
pszFrom = @"c:\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCD1234567890";
pszTo = @"c:\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCD1234567890\abcdefghijklmnop.txt";
TestPathRelativePathTo(++i, pszFrom, pszTo);
// #3 Shortest path (by experiment) that returned the wrong answer
pszFrom = @"c:\ABCDEFGHIJKLMNOPQRS\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCD1234567890";
pszTo = @"c:\ABCDEFGHIJKLMNOPQRS\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCD1234567890\b.txt";
TestPathRelativePathTo(++i, pszFrom, pszTo);
// #4: Long path that errors out
// Errors out
pszFrom = @"c:\ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGH\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
pszTo = @"c:\ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGH\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\b.txt";
TestPathRelativePathTo(++i, pszFrom, pszTo);
// #5: Same as previous except one character removed from beginning of first folder
// Succeeds, but wrong return result
pszFrom = @"c:\BCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGH\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
pszTo = @"c:\BCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGH\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\b.txt";
TestPathRelativePathTo(++i, pszFrom, pszTo);
// #6: Same as previous except 3 characters added to filename.
// Succeeds, but wrong return result
pszFrom = @"c:\BCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGH\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
pszTo = @"c:\BCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGH\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\b123.txt";
TestPathRelativePathTo(++i, pszFrom, pszTo);
}
static void TestPathRelativePathTo(int i, string pszFromDir, string pszToFile)
{
int maxResult = 10000;
StringBuilder result = new StringBuilder(maxResult);
Console.WriteLine($"#{i}: Calling PathRelativePathTo(...): pszFrom.Length: {pszFromDir.Length}; pszTo.Length {pszToFile.Length} ");
bool bRet = Native.PathRelativePathTo(result, pszFromDir, (int)FileAttributes.Directory, pszToFile, (int)FileAttributes.Normal);
if (!bRet)
{
// *Edit*: As pointed out in the comments, PathRelativePathTo does not set last error, so this part of the code is incorrect, it should really just print out that the method returned false.
// https://blogs.msdn.microsoft.com/shawnfa/2004/09/10/formatmessage-shortcut-for-win32-error-codes/
int currentError = Marshal.GetLastWin32Error();
var errorMessage = new Win32Exception(currentError).Message;
Console.WriteLine($" Error: {errorMessage}");
}
else
{
Console.WriteLine($" Result: {result}");
}
}
}
Production:
#1: Calling PathRelativePathTo(...): pszFrom.Length: 238; pszTo.Length 259
Result: .\abcdefghijklmnop.txt
#2: Calling PathRelativePathTo(...): pszFrom.Length: 239; pszTo.Length 260
Result: .\abcdefghijklmnop.txt
#3: Calling PathRelativePathTo(...): pszFrom.Length: 259; pszTo.Length 265
Result: ..\ABCD1234567890\b.txt
#4: Calling PathRelativePathTo(...): pszFrom.Length: 481; pszTo.Length 487
Error: The system cannot find the file specified
#5: Calling PathRelativePathTo(...): pszFrom.Length: 480; pszTo.Length 486
Result: .\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\b.txt
#6: Calling PathRelativePathTo(...): pszFrom.Length: 480; pszTo.Length 489
Result: .\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890\b123.txt
Des questions:
- Quel est le comportement attendu de
PathRelativePathTo
ce qui précède? - Est-il uniquement censé fonctionner correctement avec des chemins sous la limite "courte" MAX_PATH (et le reste du comportement n'est pas défini)?
- Y a-t-il autre chose dans le framework .net que je peux utiliser à la place (Remarque: je vois que .NET Core a Path.GetRelativePath , mais je ne peux pas (encore) l'utiliser)?
PathRelativePathTo
, ce n'est pas destiné aux longs chemins. Il n'est en fait pas sûr de l'utiliser, car vous ne pouvez pas indiquer la taille du tampon de destination, la documentation indique seulement qu'il "doit avoir au moins MAX_PATH caractères."