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|
// 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.InteropServices;
using System.Text;
namespace System.IO
{
// Provides methods for processing file system strings in a cross-platform manner.
// Most of the methods don't do a complete parsing (such as examining a UNC hostname),
// but they will handle most string operations.
public static partial class Path
{
// Public static readonly variant of the separators. The Path implementation itself is using
// internal const variant of the separators for better performance.
public static readonly char DirectorySeparatorChar = PathInternal.DirectorySeparatorChar;
public static readonly char AltDirectorySeparatorChar = PathInternal.AltDirectorySeparatorChar;
public static readonly char VolumeSeparatorChar = PathInternal.VolumeSeparatorChar;
public static readonly char PathSeparator = PathInternal.PathSeparator;
// For generating random file names
// 8 random bytes provides 12 chars in our encoding for the 8.3 name.
private const int KeyLength = 8;
[Obsolete("Please use GetInvalidPathChars or GetInvalidFileNameChars instead.")]
public static readonly char[] InvalidPathChars = GetInvalidPathChars();
// Changes the extension of a file path. The path parameter
// specifies a file path, and the extension parameter
// specifies a file extension (with a leading period, such as
// ".exe" or ".cs").
//
// The function returns a file path with the same root, directory, and base
// name parts as path, but with the file extension changed to
// the specified extension. If path is null, the function
// returns null. If path does not contain a file extension,
// the new file extension is appended to the path. If extension
// is null, any existing extension is removed from path.
public static string ChangeExtension(string path, string extension)
{
if (path != null)
{
string s = path;
for (int i = path.Length - 1; i >= 0; i--)
{
char ch = path[i];
if (ch == '.')
{
s = path.Substring(0, i);
break;
}
if (PathInternal.IsDirectorySeparator(ch)) break;
}
if (extension != null && path.Length != 0)
{
s = (extension.Length == 0 || extension[0] != '.') ?
s + "." + extension :
s + extension;
}
return s;
}
return null;
}
/// <summary>
/// Returns the directory portion of a file path. This method effectively
/// removes the last segment of the given file path, i.e. it returns a
/// string consisting of all characters up to but not including the last
/// backslash ("\") in the file path. The returned value is null if the
/// specified path is null, empty, or a root (such as "\", "C:", or
/// "\\server\share").
/// </summary>
/// <remarks>
/// Directory separators are normalized in the returned string.
/// </remarks>
public static string GetDirectoryName(string path)
{
if (path == null || PathInternal.IsEffectivelyEmpty(path))
return null;
int end = GetDirectoryNameOffset(path);
return end >= 0 ? PathInternal.NormalizeDirectorySeparators(path.Substring(0, end)) : null;
}
/// <summary>
/// Returns the directory portion of a file path. The returned value is empty
/// if the specified path is null, empty, or a root (such as "\", "C:", or
/// "\\server\share").
/// </summary>
/// <remarks>
/// Unlike the string overload, this method will not normalize directory separators.
/// </remarks>
public static ReadOnlySpan<char> GetDirectoryName(ReadOnlySpan<char> path)
{
if (PathInternal.IsEffectivelyEmpty(path))
return ReadOnlySpan<char>.Empty;
int end = GetDirectoryNameOffset(path);
return end >= 0 ? path.Slice(0, end) : ReadOnlySpan<char>.Empty;
}
private static int GetDirectoryNameOffset(ReadOnlySpan<char> path)
{
int rootLength = PathInternal.GetRootLength(path);
int end = path.Length;
if (end <= rootLength)
return -1;
while (end > rootLength && !PathInternal.IsDirectorySeparator(path[--end]));
// Trim off any remaining separators (to deal with C:\foo\\bar)
while (end > rootLength && PathInternal.IsDirectorySeparator(path[end - 1]))
end--;
return end;
}
/// <summary>
/// Returns the extension of the given path. The returned value includes the period (".") character of the
/// extension except when you have a terminal period when you get string.Empty, such as ".exe" or ".cpp".
/// The returned value is null if the given path is null or empty if the given path does not include an
/// extension.
/// </summary>
public static string GetExtension(string path)
{
if (path == null)
return null;
return new string(GetExtension(path.AsSpan()));
}
/// <summary>
/// Returns the extension of the given path.
/// </summary>
/// <remarks>
/// The returned value is an empty ReadOnlySpan if the given path does not include an extension.
/// </remarks>
public static ReadOnlySpan<char> GetExtension(ReadOnlySpan<char> path)
{
int length = path.Length;
for (int i = length - 1; i >= 0; i--)
{
char ch = path[i];
if (ch == '.')
{
if (i != length - 1)
return path.Slice(i, length - i);
else
return ReadOnlySpan<char>.Empty;
}
if (PathInternal.IsDirectorySeparator(ch))
break;
}
return ReadOnlySpan<char>.Empty;
}
/// <summary>
/// Returns the name and extension parts of the given path. The resulting string contains
/// the characters of path that follow the last separator in path. The resulting string is
/// null if path is null.
/// </summary>
public static string GetFileName(string path)
{
if (path == null)
return null;
ReadOnlySpan<char> result = GetFileName(path.AsSpan());
if (path.Length == result.Length)
return path;
return new string(result);
}
/// <summary>
/// The returned ReadOnlySpan contains the characters of the path that follows the last separator in path.
/// </summary>
public static ReadOnlySpan<char> GetFileName(ReadOnlySpan<char> path)
{
int root = GetPathRoot(path).Length;
// We don't want to cut off "C:\file.txt:stream" (i.e. should be "file.txt:stream")
// but we *do* want "C:Foo" => "Foo". This necessitates checking for the root.
for (int i = path.Length; --i >= 0;)
{
if (i < root || PathInternal.IsDirectorySeparator(path[i]))
return path.Slice(i + 1, path.Length - i - 1);
}
return path;
}
public static string GetFileNameWithoutExtension(string path)
{
if (path == null)
return null;
ReadOnlySpan<char> result = GetFileNameWithoutExtension(path.AsSpan());
if (path.Length == result.Length)
return path;
return new string(result);
}
/// <summary>
/// Returns the characters between the last separator and last (.) in the path.
/// </summary>
public static ReadOnlySpan<char> GetFileNameWithoutExtension(ReadOnlySpan<char> path)
{
ReadOnlySpan<char> fileName = GetFileName(path);
int lastPeriod = fileName.LastIndexOf('.');
return lastPeriod == -1 ?
fileName : // No extension was found
fileName.Slice(0, lastPeriod);
}
/// <summary>
/// Returns a cryptographically strong random 8.3 string that can be
/// used as either a folder name or a file name.
/// </summary>
public static unsafe string GetRandomFileName()
{
byte* pKey = stackalloc byte[KeyLength];
Interop.GetRandomBytes(pKey, KeyLength);
const int RandomFileNameLength = 12;
char* pRandomFileName = stackalloc char[RandomFileNameLength];
Populate83FileNameFromRandomBytes(pKey, KeyLength, pRandomFileName, RandomFileNameLength);
return new string(pRandomFileName, 0, RandomFileNameLength);
}
/// <summary>
/// Returns true 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).
/// Returns false if the path specified is relative to the current drive or working directory.
/// </summary>
/// <remarks>
/// Handles paths that use the alternate directory separator. It is a frequent mistake to
/// assume that rooted paths <see cref="Path.IsPathRooted(string)"/> 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>
/// <exception cref="ArgumentNullException">
/// Thrown if <paramref name="path"/> is null.
/// </exception>
public static bool IsPathFullyQualified(string path)
{
if (path == null)
throw new ArgumentNullException(nameof(path));
return IsPathFullyQualified(path.AsSpan());
}
public static bool IsPathFullyQualified(ReadOnlySpan<char> path)
{
return !PathInternal.IsPartiallyQualified(path);
}
/// <summary>
/// Tests if a path's file name includes a file extension. A trailing period
/// is not considered an extension.
/// </summary>
public static bool HasExtension(string path)
{
if (path != null)
{
return HasExtension(path.AsSpan());
}
return false;
}
public static bool HasExtension(ReadOnlySpan<char> path)
{
for (int i = path.Length - 1; i >= 0; i--)
{
char ch = path[i];
if (ch == '.')
{
return i != path.Length - 1;
}
if (PathInternal.IsDirectorySeparator(ch))
break;
}
return false;
}
public static string Combine(string path1, string path2)
{
if (path1 == null || path2 == null)
throw new ArgumentNullException((path1 == null) ? nameof(path1) : nameof(path2));
return CombineInternal(path1, path2);
}
public static string Combine(string path1, string path2, string path3)
{
if (path1 == null || path2 == null || path3 == null)
throw new ArgumentNullException((path1 == null) ? nameof(path1) : (path2 == null) ? nameof(path2) : nameof(path3));
return CombineInternal(path1, path2, path3);
}
public static string Combine(string path1, string path2, string path3, string path4)
{
if (path1 == null || path2 == null || path3 == null || path4 == null)
throw new ArgumentNullException((path1 == null) ? nameof(path1) : (path2 == null) ? nameof(path2) : (path3 == null) ? nameof(path3) : nameof(path4));
return CombineInternal(path1, path2, path3, path4);
}
public static string Combine(params string[] paths)
{
if (paths == null)
{
throw new ArgumentNullException(nameof(paths));
}
int finalSize = 0;
int firstComponent = 0;
// We have two passes, the first calculates how large a buffer to allocate and does some precondition
// checks on the paths passed in. The second actually does the combination.
for (int i = 0; i < paths.Length; i++)
{
if (paths[i] == null)
{
throw new ArgumentNullException(nameof(paths));
}
if (paths[i].Length == 0)
{
continue;
}
if (IsPathRooted(paths[i]))
{
firstComponent = i;
finalSize = paths[i].Length;
}
else
{
finalSize += paths[i].Length;
}
char ch = paths[i][paths[i].Length - 1];
if (!PathInternal.IsDirectorySeparator(ch))
finalSize++;
}
StringBuilder finalPath = StringBuilderCache.Acquire(finalSize);
for (int i = firstComponent; i < paths.Length; i++)
{
if (paths[i].Length == 0)
{
continue;
}
if (finalPath.Length == 0)
{
finalPath.Append(paths[i]);
}
else
{
char ch = finalPath[finalPath.Length - 1];
if (!PathInternal.IsDirectorySeparator(ch))
{
finalPath.Append(PathInternal.DirectorySeparatorChar);
}
finalPath.Append(paths[i]);
}
}
return StringBuilderCache.GetStringAndRelease(finalPath);
}
// Unlike Combine(), Join() methods do not consider rooting. They simply combine paths, ensuring that there
// is a directory separator between them.
public static string Join(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2)
{
if (path1.Length == 0)
return new string(path2);
if (path2.Length == 0)
return new string(path1);
return JoinInternal(path1, path2);
}
public static string Join(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, ReadOnlySpan<char> path3)
{
if (path1.Length == 0)
return Join(path2, path3);
if (path2.Length == 0)
return Join(path1, path3);
if (path3.Length == 0)
return Join(path1, path2);
return JoinInternal(path1, path2, path3);
}
public static bool TryJoin(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, Span<char> destination, out int charsWritten)
{
charsWritten = 0;
if (path1.Length == 0 && path2.Length == 0)
return true;
if (path1.Length == 0 || path2.Length == 0)
{
ref ReadOnlySpan<char> pathToUse = ref path1.Length == 0 ? ref path2 : ref path1;
if (destination.Length < pathToUse.Length)
{
return false;
}
pathToUse.CopyTo(destination);
charsWritten = pathToUse.Length;
return true;
}
bool needsSeparator = !(PathInternal.EndsInDirectorySeparator(path1) || PathInternal.StartsWithDirectorySeparator(path2));
int charsNeeded = path1.Length + path2.Length + (needsSeparator ? 1 : 0);
if (destination.Length < charsNeeded)
return false;
path1.CopyTo(destination);
if (needsSeparator)
destination[path1.Length] = DirectorySeparatorChar;
path2.CopyTo(destination.Slice(path1.Length + (needsSeparator ? 1 : 0)));
charsWritten = charsNeeded;
return true;
}
public static bool TryJoin(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, ReadOnlySpan<char> path3, Span<char> destination, out int charsWritten)
{
charsWritten = 0;
if (path1.Length == 0 && path2.Length == 0 && path3.Length == 0)
return true;
if (path1.Length == 0)
return TryJoin(path2, path3, destination, out charsWritten);
if (path2.Length == 0)
return TryJoin(path1, path3, destination, out charsWritten);
if (path3.Length == 0)
return TryJoin(path1, path2, destination, out charsWritten);
int neededSeparators = PathInternal.EndsInDirectorySeparator(path1) || PathInternal.StartsWithDirectorySeparator(path2) ? 0 : 1;
bool needsSecondSeparator = !(PathInternal.EndsInDirectorySeparator(path2) || PathInternal.StartsWithDirectorySeparator(path3));
if (needsSecondSeparator)
neededSeparators++;
int charsNeeded = path1.Length + path2.Length + path3.Length + neededSeparators;
if (destination.Length < charsNeeded)
return false;
bool result = TryJoin(path1, path2, destination, out charsWritten);
Debug.Assert(result, "should never fail joining first two paths");
if (needsSecondSeparator)
destination[charsWritten++] = DirectorySeparatorChar;
path3.CopyTo(destination.Slice(charsWritten));
charsWritten += path3.Length;
return true;
}
private static string CombineInternal(ReadOnlySpan<char> first, ReadOnlySpan<char> second)
{
if (first.Length == 0)
return second.Length == 0
? string.Empty
: new string(second);
if (second.Length == 0)
return new string(first);
if (IsPathRooted(second))
return new string(second);
return JoinInternal(first, second);
}
private static string CombineInternal(string first, string second)
{
if (string.IsNullOrEmpty(first))
return second;
if (string.IsNullOrEmpty(second))
return first;
if (IsPathRooted(second.AsSpan()))
return second;
return JoinInternal(first, second);
}
private static string CombineInternal(string first, string second, string third)
{
if (string.IsNullOrEmpty(first))
return CombineInternal(second, third);
if (string.IsNullOrEmpty(second))
return CombineInternal(first, third);
if (string.IsNullOrEmpty(third))
return CombineInternal(first, second);
if (IsPathRooted(third.AsSpan()))
return third;
if (IsPathRooted(second.AsSpan()))
return CombineInternal(second, third);
return JoinInternal(first, second, third);
}
private static string CombineInternal(string first, string second, string third, string fourth)
{
if (string.IsNullOrEmpty(first))
return CombineInternal(second, third, fourth);
if (string.IsNullOrEmpty(second))
return CombineInternal(first, third, fourth);
if (string.IsNullOrEmpty(third))
return CombineInternal(first, second, fourth);
if (string.IsNullOrEmpty(fourth))
return CombineInternal(first, second, third);
if (IsPathRooted(fourth.AsSpan()))
return fourth;
if (IsPathRooted(third.AsSpan()))
return CombineInternal(third, fourth);
if (IsPathRooted(second.AsSpan()))
return CombineInternal(second, third, fourth);
return JoinInternal(first, second, third, fourth);
}
private unsafe static string JoinInternal(ReadOnlySpan<char> first, ReadOnlySpan<char> second)
{
Debug.Assert(first.Length > 0 && second.Length > 0, "should have dealt with empty paths");
bool hasSeparator = PathInternal.IsDirectorySeparator(first[first.Length - 1])
|| PathInternal.IsDirectorySeparator(second[0]);
fixed (char* f = &MemoryMarshal.GetReference(first), s = &MemoryMarshal.GetReference(second))
{
return string.Create(
first.Length + second.Length + (hasSeparator ? 0 : 1),
(First: (IntPtr)f, FirstLength: first.Length, Second: (IntPtr)s, SecondLength: second.Length, HasSeparator: hasSeparator),
(destination, state) =>
{
new Span<char>((char*)state.First, state.FirstLength).CopyTo(destination);
if (!state.HasSeparator)
destination[state.FirstLength] = PathInternal.DirectorySeparatorChar;
new Span<char>((char*)state.Second, state.SecondLength).CopyTo(destination.Slice(state.FirstLength + (state.HasSeparator ? 0 : 1)));
});
}
}
private unsafe static string JoinInternal(ReadOnlySpan<char> first, ReadOnlySpan<char> second, ReadOnlySpan<char> third)
{
Debug.Assert(first.Length > 0 && second.Length > 0 && third.Length > 0, "should have dealt with empty paths");
bool firstHasSeparator = PathInternal.IsDirectorySeparator(first[first.Length - 1])
|| PathInternal.IsDirectorySeparator(second[0]);
bool thirdHasSeparator = PathInternal.IsDirectorySeparator(second[second.Length - 1])
|| PathInternal.IsDirectorySeparator(third[0]);
fixed (char* f = &MemoryMarshal.GetReference(first), s = &MemoryMarshal.GetReference(second), t = &MemoryMarshal.GetReference(third))
{
return string.Create(
first.Length + second.Length + third.Length + (firstHasSeparator ? 0 : 1) + (thirdHasSeparator ? 0 : 1),
(First: (IntPtr)f, FirstLength: first.Length, Second: (IntPtr)s, SecondLength: second.Length,
Third: (IntPtr)t, ThirdLength: third.Length, FirstHasSeparator: firstHasSeparator, ThirdHasSeparator: thirdHasSeparator),
(destination, state) =>
{
new Span<char>((char*)state.First, state.FirstLength).CopyTo(destination);
if (!state.FirstHasSeparator)
destination[state.FirstLength] = PathInternal.DirectorySeparatorChar;
new Span<char>((char*)state.Second, state.SecondLength).CopyTo(destination.Slice(state.FirstLength + (state.FirstHasSeparator ? 0 : 1)));
if (!state.ThirdHasSeparator)
destination[destination.Length - state.ThirdLength - 1] = PathInternal.DirectorySeparatorChar;
new Span<char>((char*)state.Third, state.ThirdLength).CopyTo(destination.Slice(destination.Length - state.ThirdLength));
});
}
}
private unsafe static string JoinInternal(ReadOnlySpan<char> first, ReadOnlySpan<char> second, ReadOnlySpan<char> third, ReadOnlySpan<char> fourth)
{
Debug.Assert(first.Length > 0 && second.Length > 0 && third.Length > 0 && fourth.Length > 0, "should have dealt with empty paths");
bool firstHasSeparator = PathInternal.IsDirectorySeparator(first[first.Length - 1])
|| PathInternal.IsDirectorySeparator(second[0]);
bool thirdHasSeparator = PathInternal.IsDirectorySeparator(second[second.Length - 1])
|| PathInternal.IsDirectorySeparator(third[0]);
bool fourthHasSeparator = PathInternal.IsDirectorySeparator(third[third.Length - 1])
|| PathInternal.IsDirectorySeparator(fourth[0]);
fixed (char* f = &MemoryMarshal.GetReference(first), s = &MemoryMarshal.GetReference(second), t = &MemoryMarshal.GetReference(third), u = &MemoryMarshal.GetReference(fourth))
{
return string.Create(
first.Length + second.Length + third.Length + fourth.Length + (firstHasSeparator ? 0 : 1) + (thirdHasSeparator ? 0 : 1) + (fourthHasSeparator ? 0 : 1),
(First: (IntPtr)f, FirstLength: first.Length, Second: (IntPtr)s, SecondLength: second.Length,
Third: (IntPtr)t, ThirdLength: third.Length, Fourth: (IntPtr)u, FourthLength:fourth.Length,
FirstHasSeparator: firstHasSeparator, ThirdHasSeparator: thirdHasSeparator, FourthHasSeparator: fourthHasSeparator),
(destination, state) =>
{
new Span<char>((char*)state.First, state.FirstLength).CopyTo(destination);
if (!state.FirstHasSeparator)
destination[state.FirstLength] = PathInternal.DirectorySeparatorChar;
new Span<char>((char*)state.Second, state.SecondLength).CopyTo(destination.Slice(state.FirstLength + (state.FirstHasSeparator ? 0 : 1)));
if (!state.ThirdHasSeparator)
destination[state.FirstLength + state.SecondLength + (state.FirstHasSeparator ? 0 : 1)] = PathInternal.DirectorySeparatorChar;
new Span<char>((char*)state.Third, state.ThirdLength).CopyTo(destination.Slice(state.FirstLength + state.SecondLength + (state.FirstHasSeparator ? 0 : 1) + (state.ThirdHasSeparator ? 0 : 1)));
if (!state.FourthHasSeparator)
destination[destination.Length - state.FourthLength - 1] = PathInternal.DirectorySeparatorChar;
new Span<char>((char*)state.Fourth, state.FourthLength).CopyTo(destination.Slice(destination.Length - state.FourthLength));
});
}
}
private static readonly char[] s_base32Char = {
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
'y', 'z', '0', '1', '2', '3', '4', '5'};
private static unsafe void Populate83FileNameFromRandomBytes(byte* bytes, int byteCount, char* chars, int charCount)
{
Debug.Assert(bytes != null);
Debug.Assert(chars != null);
// This method requires bytes of length 8 and chars of length 12.
Debug.Assert(byteCount == 8, $"Unexpected {nameof(byteCount)}");
Debug.Assert(charCount == 12, $"Unexpected {nameof(charCount)}");
byte b0 = bytes[0];
byte b1 = bytes[1];
byte b2 = bytes[2];
byte b3 = bytes[3];
byte b4 = bytes[4];
// Consume the 5 Least significant bits of the first 5 bytes
chars[0] = s_base32Char[b0 & 0x1F];
chars[1] = s_base32Char[b1 & 0x1F];
chars[2] = s_base32Char[b2 & 0x1F];
chars[3] = s_base32Char[b3 & 0x1F];
chars[4] = s_base32Char[b4 & 0x1F];
// Consume 3 MSB of b0, b1, MSB bits 6, 7 of b3, b4
chars[5] = s_base32Char[(
((b0 & 0xE0) >> 5) |
((b3 & 0x60) >> 2))];
chars[6] = s_base32Char[(
((b1 & 0xE0) >> 5) |
((b4 & 0x60) >> 2))];
// Consume 3 MSB bits of b2, 1 MSB bit of b3, b4
b2 >>= 5;
Debug.Assert(((b2 & 0xF8) == 0), "Unexpected set bits");
if ((b3 & 0x80) != 0)
b2 |= 0x08;
if ((b4 & 0x80) != 0)
b2 |= 0x10;
chars[7] = s_base32Char[b2];
// Set the file extension separator
chars[8] = '.';
// Consume the 5 Least significant bits of the remaining 3 bytes
chars[9] = s_base32Char[(bytes[5] & 0x1F)];
chars[10] = s_base32Char[(bytes[6] & 0x1F)];
chars[11] = s_base32Char[(bytes[7] & 0x1F)];
}
/// <summary>
/// Try to remove relative segments from the given path (without combining with a root).
/// </summary>
/// <param name="skip">Skip the specified number of characters before evaluating.</param>
private static string RemoveRelativeSegments(string path, int skip = 0)
{
bool flippedSeparator = false;
// Remove "//", "/./", and "/../" from the path by copying each character to the output,
// except the ones we're removing, such that the builder contains the normalized path
// at the end.
StringBuilder sb = StringBuilderCache.Acquire(path.Length);
if (skip > 0)
{
sb.Append(path, 0, skip);
}
for (int i = skip; i < path.Length; i++)
{
char c = path[i];
if (PathInternal.IsDirectorySeparator(c) && i + 1 < path.Length)
{
// Skip this character if it's a directory separator and if the next character is, too,
// e.g. "parent//child" => "parent/child"
if (PathInternal.IsDirectorySeparator(path[i + 1]))
{
continue;
}
// Skip this character and the next if it's referring to the current directory,
// e.g. "parent/./child" => "parent/child"
if ((i + 2 == path.Length || PathInternal.IsDirectorySeparator(path[i + 2])) &&
path[i + 1] == '.')
{
i++;
continue;
}
// Skip this character and the next two if it's referring to the parent directory,
// e.g. "parent/child/../grandchild" => "parent/grandchild"
if (i + 2 < path.Length &&
(i + 3 == path.Length || PathInternal.IsDirectorySeparator(path[i + 3])) &&
path[i + 1] == '.' && path[i + 2] == '.')
{
// Unwind back to the last slash (and if there isn't one, clear out everything).
int s;
for (s = sb.Length - 1; s >= 0; s--)
{
if (PathInternal.IsDirectorySeparator(sb[s]))
{
sb.Length = (i + 3 >= path.Length && s <= skip ) ? s + 1 : s; // to avoid removing the complete "\tmp\" segment in cases like \\?\C:\tmp\..\, C:\tmp\..
break;
}
}
if (s < 0)
{
sb.Length = 0;
}
i += 2;
continue;
}
}
// Normalize the directory separator if needed
if (c != PathInternal.DirectorySeparatorChar && c == PathInternal.AltDirectorySeparatorChar)
{
c = PathInternal.DirectorySeparatorChar;
flippedSeparator = true;
}
sb.Append(c);
}
if (flippedSeparator || sb.Length != path.Length)
{
return StringBuilderCache.GetStringAndRelease(sb);
}
else
{
// We haven't changed the source path, return the original
StringBuilderCache.Release(sb);
return path;
}
}
/// <summary>
/// Create a relative path from one path to another. Paths will be resolved before calculating the difference.
/// Default path comparison for the active platform will be used (OrdinalIgnoreCase for Windows or Mac, Ordinal for Unix).
/// </summary>
/// <param name="relativeTo">The source path the output should be relative to. This path is always considered to be a directory.</param>
/// <param name="path">The destination path.</param>
/// <returns>The relative path or <paramref name="path"/> if the paths don't share the same root.</returns>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="relativeTo"/> or <paramref name="path"/> is <c>null</c> or an empty string.</exception>
public static string GetRelativePath(string relativeTo, string path)
{
return GetRelativePath(relativeTo, path, StringComparison);
}
private static string GetRelativePath(string relativeTo, string path, StringComparison comparisonType)
{
if (string.IsNullOrEmpty(relativeTo)) throw new ArgumentNullException(nameof(relativeTo));
if (PathInternal.IsEffectivelyEmpty(path)) throw new ArgumentNullException(nameof(path));
Debug.Assert(comparisonType == StringComparison.Ordinal || comparisonType == StringComparison.OrdinalIgnoreCase);
relativeTo = GetFullPath(relativeTo);
path = GetFullPath(path);
// Need to check if the roots are different- if they are we need to return the "to" path.
if (!PathInternal.AreRootsEqual(relativeTo, path, comparisonType))
return path;
int commonLength = PathInternal.GetCommonPathLength(relativeTo, path, ignoreCase: comparisonType == StringComparison.OrdinalIgnoreCase);
// If there is nothing in common they can't share the same root, return the "to" path as is.
if (commonLength == 0)
return path;
// Trailing separators aren't significant for comparison
int relativeToLength = relativeTo.Length;
if (PathInternal.EndsInDirectorySeparator(relativeTo))
relativeToLength--;
bool pathEndsInSeparator = PathInternal.EndsInDirectorySeparator(path);
int pathLength = path.Length;
if (pathEndsInSeparator)
pathLength--;
// If we have effectively the same path, return "."
if (relativeToLength == pathLength && commonLength >= relativeToLength) return ".";
// We have the same root, we need to calculate the difference now using the
// common Length and Segment count past the length.
//
// Some examples:
//
// C:\Foo C:\Bar L3, S1 -> ..\Bar
// C:\Foo C:\Foo\Bar L6, S0 -> Bar
// C:\Foo\Bar C:\Bar\Bar L3, S2 -> ..\..\Bar\Bar
// C:\Foo\Foo C:\Foo\Bar L7, S1 -> ..\Bar
StringBuilder sb = StringBuilderCache.Acquire(Math.Max(relativeTo.Length, path.Length));
// Add parent segments for segments past the common on the "from" path
if (commonLength < relativeToLength)
{
sb.Append(PathInternal.ParentDirectoryPrefix);
for (int i = commonLength; i < relativeToLength; i++)
{
if (PathInternal.IsDirectorySeparator(relativeTo[i]))
{
sb.Append(PathInternal.ParentDirectoryPrefix);
}
}
}
else if (PathInternal.IsDirectorySeparator(path[commonLength]))
{
// No parent segments and we need to eat the initial separator
// (C:\Foo C:\Foo\Bar case)
commonLength++;
}
// Now add the rest of the "to" path, adding back the trailing separator
int count = pathLength - commonLength;
if (pathEndsInSeparator)
count++;
sb.Append(path, commonLength, count);
return StringBuilderCache.GetStringAndRelease(sb);
}
/// <summary>Returns a comparison that can be used to compare file and directory names for equality.</summary>
internal static StringComparison StringComparison
{
get
{
return IsCaseSensitive ?
StringComparison.Ordinal :
StringComparison.OrdinalIgnoreCase;
}
}
}
}
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