How to overcome PathTooLongException?
-
01-01-2021 - |
Question
So I am writing a program that will scan for duplicate files on a computer as the programs that I've seen are really slow, and/or memory hogs, but I was running into a PathTooLongException
when I tried to the whole drive. After reading PathTooLongException in C# code I became curious about the following two questions.
Would it hurt my performance if I were to switch my current directory every time I changed levels?
Is there a better way to get the directory structure of all the files (perhaps by calling something like tree.exe and then parsing that)?
Solution
See this Library!
OTHER TIPS
or do it yourself,
using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;
[DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
internal static extern IntPtr FindFirstFile(string lpFileName, out
WIN32_FIND_DATA lpFindFileData);
[DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
internal static extern bool FindNextFile(IntPtr hFindFile, out
WIN32_FIND_DATA lpFindFileData);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern bool FindClose(IntPtr hFindFile);
// Assume dirName passed in is already prefixed with \\?\
public static IEnumerable<string> EnumerateEntries(string directory)
{
WIN32_FIND_DATA findData;
IntPtr findHandle = FindFirstFile(dirName + @"\*", out findData);
try
{
if (findHandle != INVALID_HANDLE_VALUE)
{
bool found;
do
{
string currentFileName = findData.cFileName;
// if this is a directory, find its contents
if (((int)findData.dwFileAttributes &
FILE_ATTRIBUTE_DIRECTORY) != 0)
{
if (currentFileName != "." && currentFileName != "..")
{
foreach(var child in FindFilesAndDirs(
Path.Combine(dirName, currentFileName))
{
yield return child;
}
}
}
yield return Path.Combine(dirName, currentFileName);
// find next
found = FindNextFile(findHandle, out findData);
}
while (found);
}
}
finally
{
// close the find handle
FindClose(findHandle);
}
}
I haven't verified this code and obviously not all the types are defined but it should point us in the right direction.
Pure C#, needs optimization but will give people a headstart without using an external library or p/invoking..
public static class DirectoryEx
{
static char driveLetter;
static string longPath;
static List<string> directories;
static DirectoryEx()
{
longPath = String.Empty;
}
private static char GetAvailableDrive()
{
var all = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray().Reverse();
var occupied = DriveInfo.GetDrives()
.OrderByDescending(d => d.Name)
.Select(d => (char)d.Name.ToUpper().First());
var free = all.Except(occupied).First();
return free;
}
public static List<string> GetDirectories(string path)
{
directories = new List<string>();
// recursive call
FindDirectories(path);
return directories;
}
static void FindDirectories(string path)
{
try
{
foreach (var directory in Directory.GetDirectories(path))
{
var di = new DirectoryInfo(directory);
if(!String.IsNullOrEmpty(longPath))
directories.Add(di.FullName.Replace(driveLetter + ":\\", longPath + "\\"));
else
directories.Add(di.FullName);
FindDirectories(di.FullName);
}
}
catch (UnauthorizedAccessException uaex) { Debug.WriteLine(uaex.Message); }
catch (PathTooLongException ptlex)
{
Debug.WriteLine(ptlex.Message);
longPath = path;
Task t = new Task(new Action(() =>
{
CreateVirtualDrive(longPath);
FindDirectories(driveLetter + ":\\");
DeleteVirtualDrive();
longPath = String.Empty;
}));
if (!String.IsNullOrEmpty(longPath))
t.RunSynchronously();
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
}
static void CreateVirtualDrive(string path)
{
driveLetter = GetAvailableDrive();
Process.Start(new ProcessStartInfo() {
FileName = "cmd.exe",
WindowStyle = ProcessWindowStyle.Hidden,
Arguments = String.Format("/c subst {0}: {1}", driveLetter.ToString(), path)
});
while (!DriveInfo.GetDrives().Select(d => d.Name.ToUpper().First()).Contains(driveLetter))
{
System.Threading.Thread.Sleep(1);
}
}
static void DeleteVirtualDrive()
{
Process.Start(new ProcessStartInfo()
{
FileName = "cmd.exe",
WindowStyle = ProcessWindowStyle.Hidden,
Arguments = String.Format("/c subst {0}: /D", driveLetter.ToString())
});
while (DriveInfo.GetDrives().Select(d => d.Name.ToUpper().First()).Contains(driveLetter))
{
System.Threading.Thread.Sleep(1);
}
}
}