PR icsharpcode#593

src/ICSharpCode.SharpZipLib/Core/PathUtils.cs

@@ -1,4 +1,5 @@
 using System.IO;
+using System.Linq;
 
 namespace ICSharpCode.SharpZipLib.Core
 {
@@ -12,46 +13,21 @@ public static class PathUtils
 		/// </summary>
 		/// <param name="path">A <see cref="string"/> containing path information.</param>
 		/// <returns>The path with the root removed if it was present; path otherwise.</returns>
-		/// <remarks>Unlike the <see cref="Path"/> class the path isn't otherwise checked for validity.</remarks>
 		public static string DropPathRoot(string path)
 		{
-			string result = path;
-
-			if (!string.IsNullOrEmpty(path))
-			{
-				if ((path[0] == '\\') || (path[0] == '/'))
-				{
-					// UNC name ?
-					if ((path.Length > 1) && ((path[1] == '\\') || (path[1] == '/')))
-					{
-						int index = 2;
-						int elements = 2;
-
-						// Scan for two separate elements \\machine\share\restofpath
-						while ((index <= path.Length) && (((path[index] != '\\') && (path[index] != '/')) || (--elements > 0)))
-						{
-							index++;
-						}
-
-						index++;
-
-						if (index < path.Length)
-							result = path[index..];
-						else
-							result = "";
-					}
-				}
-				else if ((path.Length > 1) && (path[1] == ':'))
-				{
-					int dropCount = 2;
-					if ((path.Length > 2) && ((path[2] == '\\') || (path[2] == '/')))
-						dropCount = 3;
-
-					result = result.Remove(0, dropCount);
-				}
-			}
-
-			return result;
+			var invalidChars = Path.GetInvalidPathChars();
+			// If the first character after the root is a ':', .NET < 4.6.2 throws
+			var cleanRootSep = path.Length >= 3 && path[1] == ':' && path[2] == ':';
+
+			// Replace any invalid path characters with '_' to prevent Path.GetPathRoot from throwing.
+			// Only pass the first 258 (should be 260, but that still throws for some reason) characters
+			// as .NET < 4.6.2 throws on longer paths
+			var cleanPath = new string(path.Take(258)
+				.Select((c, i) => invalidChars.Contains(c) || (i == 2 && cleanRootSep) ? '_' : c).ToArray());
+
+			var stripLength = Path.GetPathRoot(cleanPath).Length;
+			while (path.Length > stripLength && (path[stripLength] == '/' || path[stripLength] == '\\')) stripLength++;
+			return path.Substring(stripLength);
 		}
 
 		/// <summary>