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Diffstat (limited to 'src/mscorlib/corefx/System/IO/PathInternal.Windows.cs')
| -rw-r--r-- | src/mscorlib/corefx/System/IO/PathInternal.Windows.cs | 482 |
1 files changed, 482 insertions, 0 deletions
diff --git a/src/mscorlib/corefx/System/IO/PathInternal.Windows.cs b/src/mscorlib/corefx/System/IO/PathInternal.Windows.cs new file mode 100644 index 0000000000..bd7f1eae41 --- /dev/null +++ b/src/mscorlib/corefx/System/IO/PathInternal.Windows.cs @@ -0,0 +1,482 @@ +// Licensed to the .NET Foundation under one or more agreements. +// The .NET Foundation licenses this file to you under the MIT license. +// See the LICENSE file in the project root for more information. + +using System.Diagnostics; +using System.Runtime.CompilerServices; +using System.Text; + +namespace System.IO +{ + /// <summary>Contains internal path helpers that are shared between many projects.</summary> + internal static partial class PathInternal + { + // All paths in Win32 ultimately end up becoming a path to a File object in the Windows object manager. Passed in paths get mapped through + // DosDevice symbolic links in the object tree to actual File objects under \Devices. To illustrate, this is what happens with a typical + // path "Foo" passed as a filename to any Win32 API: + // + // 1. "Foo" is recognized as a relative path and is appended to the current directory (say, "C:\" in our example) + // 2. "C:\Foo" is prepended with the DosDevice namespace "\??\" + // 3. CreateFile tries to create an object handle to the requested file "\??\C:\Foo" + // 4. The Object Manager recognizes the DosDevices prefix and looks + // a. First in the current session DosDevices ("\Sessions\1\DosDevices\" for example, mapped network drives go here) + // b. If not found in the session, it looks in the Global DosDevices ("\GLOBAL??\") + // 5. "C:" is found in DosDevices (in our case "\GLOBAL??\C:", which is a symbolic link to "\Device\HarddiskVolume6") + // 6. The full path is now "\Device\HarddiskVolume6\Foo", "\Device\HarddiskVolume6" is a File object and parsing is handed off + // to the registered parsing method for Files + // 7. The registered open method for File objects is invoked to create the file handle which is then returned + // + // There are multiple ways to directly specify a DosDevices path. The final format of "\??\" is one way. It can also be specified + // as "\\.\" (the most commonly documented way) and "\\?\". If the question mark syntax is used the path will skip normalization + // (essentially GetFullPathName()) and path length checks. + + // Windows Kernel-Mode Object Manager + // https://msdn.microsoft.com/en-us/library/windows/hardware/ff565763.aspx + // https://channel9.msdn.com/Shows/Going+Deep/Windows-NT-Object-Manager + // + // Introduction to MS-DOS Device Names + // https://msdn.microsoft.com/en-us/library/windows/hardware/ff548088.aspx + // + // Local and Global MS-DOS Device Names + // https://msdn.microsoft.com/en-us/library/windows/hardware/ff554302.aspx + + internal const string ExtendedPathPrefix = @"\\?\"; + internal const string UncPathPrefix = @"\\"; + internal const string UncExtendedPrefixToInsert = @"?\UNC\"; + internal const string UncExtendedPathPrefix = @"\\?\UNC\"; + internal const string DevicePathPrefix = @"\\.\"; + internal const string ParentDirectoryPrefix = @"..\"; + + internal const int MaxShortPath = 260; + internal const int MaxShortDirectoryPath = 248; + internal const int MaxLongPath = short.MaxValue; + // \\?\, \\.\, \??\ + internal const int DevicePrefixLength = 4; + // \\ + internal const int UncPrefixLength = 2; + // \\?\UNC\, \\.\UNC\ + internal const int UncExtendedPrefixLength = 8; + internal const int MaxComponentLength = 255; + + internal static char[] GetInvalidPathChars() => new char[] + { + '|', '\0', + (char)1, (char)2, (char)3, (char)4, (char)5, (char)6, (char)7, (char)8, (char)9, (char)10, + (char)11, (char)12, (char)13, (char)14, (char)15, (char)16, (char)17, (char)18, (char)19, (char)20, + (char)21, (char)22, (char)23, (char)24, (char)25, (char)26, (char)27, (char)28, (char)29, (char)30, + (char)31 + }; + + // [MS - FSA] 2.1.4.4 Algorithm for Determining if a FileName Is in an Expression + // https://msdn.microsoft.com/en-us/library/ff469270.aspx + private static readonly char[] s_wildcardChars = + { + '\"', '<', '>', '*', '?' + }; + + /// <summary> + /// Returns true if the given character is a valid drive letter + /// </summary> + internal static bool IsValidDriveChar(char value) + { + return ((value >= 'A' && value <= 'Z') || (value >= 'a' && value <= 'z')); + } + + /// <summary> + /// Returns true if the path is too long + /// </summary> + internal static bool IsPathTooLong(string fullPath) + { + // We'll never know precisely what will fail as paths get changed internally in Windows and + // may grow to exceed MaxLongPath. + return fullPath.Length >= MaxLongPath; + } + + /// <summary> + /// Returns true if the directory is too long + /// </summary> + internal static bool IsDirectoryTooLong(string fullPath) + { + return IsPathTooLong(fullPath); + } + + /// <summary> + /// Adds the extended path prefix (\\?\) if not already a device path, IF the path is not relative, + /// AND the path is more than 259 characters. (> MAX_PATH + null) + /// </summary> + internal static string EnsureExtendedPrefixOverMaxPath(string path) + { + if (path != null && path.Length >= MaxShortPath) + { + return EnsureExtendedPrefix(path); + } + else + { + return path; + } + } + + /// <summary> + /// Adds the extended path prefix (\\?\) if not relative or already a device path. + /// </summary> + internal static string EnsureExtendedPrefix(string path) + { + // Putting the extended prefix on the path changes the processing of the path. It won't get normalized, which + // means adding to relative paths will prevent them from getting the appropriate current directory inserted. + + // If it already has some variant of a device path (\??\, \\?\, \\.\, //./, etc.) we don't need to change it + // as it is either correct or we will be changing the behavior. When/if Windows supports long paths implicitly + // in the future we wouldn't want normalization to come back and break existing code. + + // In any case, all internal usages should be hitting normalize path (Path.GetFullPath) before they hit this + // shimming method. (Or making a change that doesn't impact normalization, such as adding a filename to a + // normalized base path.) + if (IsPartiallyQualified(path) || IsDevice(path)) + return path; + + // Given \\server\share in longpath becomes \\?\UNC\server\share + if (path.StartsWith(UncPathPrefix, StringComparison.OrdinalIgnoreCase)) + return path.Insert(2, UncExtendedPrefixToInsert); + + return ExtendedPathPrefix + path; + } + + /// <summary> + /// Returns true if the path uses any of the DOS device path syntaxes. ("\\.\", "\\?\", or "\??\") + /// </summary> + internal static bool IsDevice(string path) + { + // If the path begins with any two separators is will be recognized and normalized and prepped with + // "\??\" for internal usage correctly. "\??\" is recognized and handled, "/??/" is not. + return IsExtended(path) + || + ( + path.Length >= DevicePrefixLength + && IsDirectorySeparator(path[0]) + && IsDirectorySeparator(path[1]) + && (path[2] == '.' || path[2] == '?') + && IsDirectorySeparator(path[3]) + ); + } + + /// <summary> + /// Returns true if the path uses the canonical form of extended syntax ("\\?\" or "\??\"). If the + /// path matches exactly (cannot use alternate directory separators) Windows will skip normalization + /// and path length checks. + /// </summary> + internal static bool IsExtended(string path) + { + // While paths like "//?/C:/" will work, they're treated the same as "\\.\" paths. + // Skipping of normalization will *only* occur if back slashes ('\') are used. + return path.Length >= DevicePrefixLength + && path[0] == '\\' + && (path[1] == '\\' || path[1] == '?') + && path[2] == '?' + && path[3] == '\\'; + } + + /// <summary> + /// Returns a value indicating if the given path contains invalid characters (", <, >, | + /// NUL, or any ASCII char whose integer representation is in the range of 1 through 31). + /// Does not check for wild card characters ? and *. + /// </summary> + internal static bool HasIllegalCharacters(string path) + { + // This is equivalent to IndexOfAny(InvalidPathChars) >= 0, + // except faster since IndexOfAny grows slower as the input + // array grows larger. + // Since we know that some of the characters we're looking + // for are contiguous in the alphabet-- the path cannot contain + // characters 0-31-- we can optimize this for our specific use + // case and use simple comparison operations. + + for (int i = 0; i < path.Length; i++) + { + char c = path[i]; + + if (c <= '\u001f' || c == '|') + { + return true; + } + } + + return false; + } + + /// <summary> + /// Check for known wildcard characters. '*' and '?' are the most common ones. + /// </summary> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + internal unsafe static bool HasWildCardCharacters(string path) + { + // Question mark is part of dos device syntax so we have to skip if we are + int startIndex = IsDevice(path) ? ExtendedPathPrefix.Length : 0; + + return path.IndexOfAny(s_wildcardChars, startIndex) >= 0; + } + + /// <summary> + /// Gets the length of the root of the path (drive, share, etc.). + /// </summary> + internal unsafe static int GetRootLength(string path) + { + fixed(char* value = path) + { + return (int)GetRootLength(value, (uint)path.Length); + } + } + + private unsafe static uint GetRootLength(char* path, uint pathLength) + { + uint i = 0; + uint volumeSeparatorLength = 2; // Length to the colon "C:" + uint uncRootLength = 2; // Length to the start of the server name "\\" + + bool extendedSyntax = StartsWithOrdinal(path, pathLength, ExtendedPathPrefix); + bool extendedUncSyntax = StartsWithOrdinal(path, pathLength, UncExtendedPathPrefix); + if (extendedSyntax) + { + // Shift the position we look for the root from to account for the extended prefix + if (extendedUncSyntax) + { + // "\\" -> "\\?\UNC\" + uncRootLength = (uint)UncExtendedPathPrefix.Length; + } + else + { + // "C:" -> "\\?\C:" + volumeSeparatorLength += (uint)ExtendedPathPrefix.Length; + } + } + + if ((!extendedSyntax || extendedUncSyntax) && pathLength > 0 && IsDirectorySeparator(path[0])) + { + // UNC or simple rooted path (e.g. "\foo", NOT "\\?\C:\foo") + + i = 1; // Drive rooted (\foo) is one character + if (extendedUncSyntax || (pathLength > 1 && IsDirectorySeparator(path[1]))) + { + // UNC (\\?\UNC\ or \\), scan past the next two directory separators at most + // (e.g. to \\?\UNC\Server\Share or \\Server\Share\) + i = uncRootLength; + int n = 2; // Maximum separators to skip + while (i < pathLength && (!IsDirectorySeparator(path[i]) || --n > 0)) i++; + } + } + else if (pathLength >= volumeSeparatorLength && path[volumeSeparatorLength - 1] == Path.VolumeSeparatorChar) + { + // Path is at least longer than where we expect a colon, and has a colon (\\?\A:, A:) + // If the colon is followed by a directory separator, move past it + i = volumeSeparatorLength; + if (pathLength >= volumeSeparatorLength + 1 && IsDirectorySeparator(path[volumeSeparatorLength])) i++; + } + return i; + } + + private unsafe static bool StartsWithOrdinal(char* source, uint sourceLength, string value) + { + if (sourceLength < (uint)value.Length) return false; + for (int i = 0; i < value.Length; i++) + { + if (value[i] != source[i]) return false; + } + return true; + } + + /// <summary> + /// Returns true if the path specified is relative to the current drive or working directory. + /// Returns false if the path is fixed to a specific drive or UNC path. This method does no + /// validation of the path (URIs will be returned as relative as a result). + /// </summary> + /// <remarks> + /// Handles paths that use the alternate directory separator. It is a frequent mistake to + /// assume that rooted paths (Path.IsPathRooted) are not relative. This isn't the case. + /// "C:a" is drive relative- meaning that it will be resolved against the current directory + /// for C: (rooted, but relative). "C:\a" is rooted and not relative (the current directory + /// will not be used to modify the path). + /// </remarks> + internal static bool IsPartiallyQualified(string path) + { + if (path.Length < 2) + { + // It isn't fixed, it must be relative. There is no way to specify a fixed + // path with one character (or less). + return true; + } + + if (IsDirectorySeparator(path[0])) + { + // There is no valid way to specify a relative path with two initial slashes or + // \? as ? isn't valid for drive relative paths and \??\ is equivalent to \\?\ + return !(path[1] == '?' || IsDirectorySeparator(path[1])); + } + + // The only way to specify a fixed path that doesn't begin with two slashes + // is the drive, colon, slash format- i.e. C:\ + return !((path.Length >= 3) + && (path[1] == Path.VolumeSeparatorChar) + && IsDirectorySeparator(path[2]) + // To match old behavior we'll check the drive character for validity as the path is technically + // not qualified if you don't have a valid drive. "=:\" is the "=" file's default data stream. + && IsValidDriveChar(path[0])); + } + + /// <summary> + /// Returns the characters to skip at the start of the path if it starts with space(s) and a drive or directory separator. + /// (examples are " C:", " \") + /// This is a legacy behavior of Path.GetFullPath(). + /// </summary> + /// <remarks> + /// Note that this conflicts with IsPathRooted() which doesn't (and never did) such a skip. + /// </remarks> + internal static int PathStartSkip(string path) + { + int startIndex = 0; + while (startIndex < path.Length && path[startIndex] == ' ') startIndex++; + + if (startIndex > 0 && (startIndex < path.Length && IsDirectorySeparator(path[startIndex])) + || (startIndex + 1 < path.Length && path[startIndex + 1] == ':' && IsValidDriveChar(path[startIndex]))) + { + // Go ahead and skip spaces as we're either " C:" or " \" + return startIndex; + } + + return 0; + } + + /// <summary> + /// True if the given character is a directory separator. + /// </summary> + [MethodImpl(MethodImplOptions.AggressiveInlining)] + internal static bool IsDirectorySeparator(char c) + { + return c == Path.DirectorySeparatorChar || c == Path.AltDirectorySeparatorChar; + } + + /// <summary> + /// Normalize separators in the given path. Converts forward slashes into back slashes and compresses slash runs, keeping initial 2 if present. + /// Also trims initial whitespace in front of "rooted" paths (see PathStartSkip). + /// + /// This effectively replicates the behavior of the legacy NormalizePath when it was called with fullCheck=false and expandShortpaths=false. + /// The current NormalizePath gets directory separator normalization from Win32's GetFullPathName(), which will resolve relative paths and as + /// such can't be used here (and is overkill for our uses). + /// + /// Like the current NormalizePath this will not try and analyze periods/spaces within directory segments. + /// </summary> + /// <remarks> + /// The only callers that used to use Path.Normalize(fullCheck=false) were Path.GetDirectoryName() and Path.GetPathRoot(). Both usages do + /// not need trimming of trailing whitespace here. + /// + /// GetPathRoot() could technically skip normalizing separators after the second segment- consider as a future optimization. + /// + /// For legacy desktop behavior with ExpandShortPaths: + /// - It has no impact on GetPathRoot() so doesn't need consideration. + /// - It could impact GetDirectoryName(), but only if the path isn't relative (C:\ or \\Server\Share). + /// + /// In the case of GetDirectoryName() the ExpandShortPaths behavior was undocumented and provided inconsistent results if the path was + /// fixed/relative. For example: "C:\PROGRA~1\A.TXT" would return "C:\Program Files" while ".\PROGRA~1\A.TXT" would return ".\PROGRA~1". If you + /// ultimately call GetFullPath() this doesn't matter, but if you don't or have any intermediate string handling could easily be tripped up by + /// this undocumented behavior. + /// + /// We won't match this old behavior because: + /// + /// 1. It was undocumented + /// 2. It was costly (extremely so if it actually contained '~') + /// 3. Doesn't play nice with string logic + /// 4. Isn't a cross-plat friendly concept/behavior + /// </remarks> + internal static string NormalizeDirectorySeparators(string path) + { + if (string.IsNullOrEmpty(path)) return path; + + char current; + int start = PathStartSkip(path); + + if (start == 0) + { + // Make a pass to see if we need to normalize so we can potentially skip allocating + bool normalized = true; + + for (int i = 0; i < path.Length; i++) + { + current = path[i]; + if (IsDirectorySeparator(current) + && (current != Path.DirectorySeparatorChar + // Check for sequential separators past the first position (we need to keep initial two for UNC/extended) + || (i > 0 && i + 1 < path.Length && IsDirectorySeparator(path[i + 1])))) + { + normalized = false; + break; + } + } + + if (normalized) return path; + } + + StringBuilder builder = new StringBuilder(path.Length); + + if (IsDirectorySeparator(path[start])) + { + start++; + builder.Append(Path.DirectorySeparatorChar); + } + + for (int i = start; i < path.Length; i++) + { + current = path[i]; + + // If we have a separator + if (IsDirectorySeparator(current)) + { + // If the next is a separator, skip adding this + if (i + 1 < path.Length && IsDirectorySeparator(path[i + 1])) + { + continue; + } + + // Ensure it is the primary separator + current = Path.DirectorySeparatorChar; + } + + builder.Append(current); + } + + return builder.ToString(); + } + + /// <summary> + /// Returns true if the character is a directory or volume separator. + /// </summary> + /// <param name="ch">The character to test.</param> + internal static bool IsDirectoryOrVolumeSeparator(char ch) + { + return IsDirectorySeparator(ch) || Path.VolumeSeparatorChar == ch; + } + + /// <summary> + /// Validates volume separator only occurs as C: or \\?\C:. This logic is meant to filter out Alternate Data Streams. + /// </summary> + /// <returns>True if the path has an invalid volume separator.</returns> + internal static bool HasInvalidVolumeSeparator(string path) + { + // Toss out paths with colons that aren't a valid drive specifier. + // Cannot start with a colon and can only be of the form "C:" or "\\?\C:". + // (Note that we used to explicitly check "http:" and "file:"- these are caught by this check now.) + + // We don't care about skipping starting space for extended paths. Assume no knowledge of extended paths if we're forcing old path behavior. + int startIndex = IsExtended(path) ? ExtendedPathPrefix.Length : PathStartSkip(path); + + // If we start with a colon + if ((path.Length > startIndex && path[startIndex] == Path.VolumeSeparatorChar) + // Or have an invalid drive letter and colon + || (path.Length >= startIndex + 2 && path[startIndex + 1] == Path.VolumeSeparatorChar && !IsValidDriveChar(path[startIndex])) + // Or have any colons beyond the drive colon + || (path.Length > startIndex + 2 && path.IndexOf(Path.VolumeSeparatorChar, startIndex + 2) != -1)) + { + return true; + } + + return false; + } + } +} |