src/main/java/com/google/devtools/build/lib/vfs/LocalPath.java - bazel - Git at Google

 // Copyright 2017 The Bazel Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //    http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 package com.google.devtools.build.lib.vfs;

 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.devtools.build.lib.util.OS;
 import com.google.devtools.build.lib.windows.WindowsShortPath;
 import com.google.devtools.build.lib.windows.jni.WindowsFileOperations;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.concurrent.atomic.AtomicReference;
 import javax.annotation.Nullable;

 /**
  * A local file path representing a file on the host machine. You should use this when you want to
  * access local files via the file system.
  *
  * <p>Paths are either absolute or relative.
  *
  * <p>Strings are normalized with '.' and '..' removed and resolved (if possible), any multiple
  * slashes ('/') removed, and any trailing slash also removed. The current implementation does not
  * touch the incoming path string unless the string actually needs to be normalized.
  *
  * <p>There is some limited support for Windows-style paths. Most importantly, drive identifiers in
  * front of a path (c:/abc) are supported and such paths are correctly recognized as absolute, as
  * are paths with backslash separators (C:\\foo\\bar). However, advanced Windows-style features like
  * \\\\network\\paths and \\\\?\\unc\\paths are not supported. We are currently using forward
  * slashes ('/') even on Windows, so backslashes '\' get converted to forward slashes during
  * normalization.
  *
  * <p>Mac and Windows file paths are case insensitive. Case is preserved.
  *
  * <p>This class is replaces {@link Path} as the way to access the host machine's file system.
  * Developers should use this class instead of {@link Path}.
  */
 public final class LocalPath implements Comparable<LocalPath> {
   private static final OsPathPolicy DEFAULT_OS = createFilePathOs();

   public static final LocalPath EMPTY = create("");

   private final String path;
   private final int driveStrLength; // 0 for relative paths, 1 on Unix, 3 on Windows
   private final OsPathPolicy os;

   /** Creates a local path that is specific to the host OS. */
   public static LocalPath create(String path) {
     return createWithOs(path, DEFAULT_OS);
   }

   @VisibleForTesting
   static LocalPath createWithOs(String path, OsPathPolicy os) {
     Preconditions.checkNotNull(path);
     int normalizationLevel = os.needsToNormalize(path);
     String normalizedPath = os.normalize(path, normalizationLevel);
     int driveStrLength = os.getDriveStrLength(normalizedPath);
     return new LocalPath(normalizedPath, driveStrLength, os);
   }

   /** This method expects path to already be normalized. */
   private LocalPath(String path, int driveStrLength, OsPathPolicy os) {
     this.path = Preconditions.checkNotNull(path);
     this.driveStrLength = driveStrLength;
     this.os = Preconditions.checkNotNull(os);
   }

   public String getPathString() {
     return path;
   }

   /**
    * If called on a {@link LocalPath} instance for a mount name (eg. '/' or 'C:/'), the empty string
    * is returned.
    */
   public String getBaseName() {
     int lastSeparator = path.lastIndexOf(os.getSeparator());
     return lastSeparator < driveStrLength
         ? path.substring(driveStrLength)
         : path.substring(lastSeparator + 1);
   }

   /**
    * Returns a {@link LocalPath} instance representing the relative path between this {@link
    * LocalPath} and the given {@link LocalPath}.
    *
    * <pre>
    *   Example:
    *
    *   LocalPath.create("/foo").getRelative(LocalPath.create("bar/baz"))
    *   -> "/foo/bar/baz"
    * </pre>
    *
    * <p>If the passed path is absolute it is returned untouched. This can be useful to resolve
    * symlinks.
    */
   public LocalPath getRelative(LocalPath other) {
     Preconditions.checkNotNull(other);
     Preconditions.checkArgument(os == other.os);
     return getRelative(other.getPathString(), other.driveStrLength);
   }

   /**
    * Returns a {@link LocalPath} instance representing the relative path between this {@link
    * LocalPath} and the given path.
    *
    * <p>See {@link #getRelative(LocalPath)} for details.
    */
   public LocalPath getRelative(String other) {
     Preconditions.checkNotNull(other);
     return getRelative(other, os.getDriveStrLength(other));
   }

   private LocalPath getRelative(String other, int otherDriveStrLength) {
     if (path.isEmpty()) {
       return create(other);
     }
     if (other.isEmpty()) {
       return this;
     }
     // Note that even if other came from a LocalPath instance we still might
     // need to normalize the result if (for instance) other is a path that
     // starts with '..'
     int normalizationLevel = os.needsToNormalize(other);
     // This is an absolute path, simply return it
     if (otherDriveStrLength > 0) {
       String normalizedPath = os.normalize(other, normalizationLevel);
       return new LocalPath(normalizedPath, otherDriveStrLength, os);
     }
     String newPath;
     if (path.length() == driveStrLength) {
       newPath = path + other;
     } else {
       newPath = path + '/' + other;
     }
     newPath = os.normalize(newPath, normalizationLevel);
     return new LocalPath(newPath, driveStrLength, os);
   }

   /**
    * Returns the parent directory of this {@link LocalPath}.
    *
    * <p>If this is called on an single directory for a relative path, this returns an empty relative
    * path. If it's called on a root (like '/') or the empty string, it returns null.
    */
   @Nullable
   public LocalPath getParentDirectory() {
     int lastSeparator = path.lastIndexOf(os.getSeparator());

     // For absolute paths we need to specially handle when we hit root
     // Relative paths can't hit this path as driveStrLength == 0
     if (driveStrLength > 0) {
       if (lastSeparator < driveStrLength) {
         if (path.length() > driveStrLength) {
           String newPath = path.substring(0, driveStrLength);
           return new LocalPath(newPath, driveStrLength, os);
         } else {
           return null;
         }
       }
     } else {
       if (lastSeparator == -1) {
         if (!path.isEmpty()) {
           return EMPTY;
         } else {
           return null;
         }
       }
     }
     String newPath = path.substring(0, lastSeparator);
     return new LocalPath(newPath, driveStrLength, os);
   }

   /**
    * Returns the {@link LocalPath} relative to the base {@link LocalPath}.
    *
    * <p>For example, <code>LocalPath.create("foo/bar/wiz").relativeTo(LocalPath.create("foo"))
    * </code> returns <code>LocalPath.create("bar/wiz")</code>.
    *
    * <p>If the {@link LocalPath} is not a child of the passed {@link LocalPath} an {@link
    * IllegalArgumentException} is thrown. In particular, this will happen whenever the two {@link
    * LocalPath} instances aren't both absolute or both relative.
    */
   public LocalPath relativeTo(LocalPath base) {
     Preconditions.checkNotNull(base);
     Preconditions.checkArgument(os == base.os);
     if (isAbsolute() != base.isAbsolute()) {
       throw new IllegalArgumentException(
           "Cannot relativize an absolute and a non-absolute path pair");
     }
     String basePath = base.path;
     if (!os.startsWith(path, basePath)) {
       throw new IllegalArgumentException(
           String.format("Path '%s' is not under '%s', cannot relativize", this, base));
     }
     int bn = basePath.length();
     if (bn == 0) {
       return this;
     }
     if (path.length() == bn) {
       return EMPTY;
     }
     final int lastSlashIndex;
     if (basePath.charAt(bn - 1) == '/') {
       lastSlashIndex = bn - 1;
     } else {
       lastSlashIndex = bn;
     }
     if (path.charAt(lastSlashIndex) != '/') {
       throw new IllegalArgumentException(
           String.format("Path '%s' is not under '%s', cannot relativize", this, base));
     }
     String newPath = path.substring(lastSlashIndex + 1);
     return new LocalPath(newPath, 0 /* Always a relative path */, os);
   }

   /**
    * Splits a path into its constituent parts. The root is not included. This is an inefficient
    * operation and should be avoided.
    */
   public String[] split() {
     String[] segments = path.split("/");
     if (driveStrLength > 0) {
       // String#split("/") for some reason returns a zero-length array
       // String#split("/hello") returns a 2-length array, so this makes little sense
       if (segments.length == 0) {
         return segments;
       }
       return Arrays.copyOfRange(segments, 1, segments.length);
     }
     return segments;
   }

   /**
    * Returns whether this path is an ancestor of another path.
    *
    * <p>A path is considered an ancestor of itself.
    *
    * <p>An absolute path can never be an ancestor of a relative path, and vice versa.
    */
   public boolean startsWith(LocalPath other) {
     Preconditions.checkNotNull(other);
     Preconditions.checkArgument(os == other.os);
     if (other.path.length() > path.length()) {
       return false;
     }
     if (driveStrLength != other.driveStrLength) {
       return false;
     }
     if (!os.startsWith(path, other.path)) {
       return false;
     }
     return path.length() == other.path.length()
         || other.path.length() == driveStrLength
         || path.charAt(other.path.length()) == os.getSeparator();
   }

   public boolean isAbsolute() {
     return driveStrLength > 0;
   }

   @Override
   public String toString() {
     return path;
   }

   @Override
   public boolean equals(Object o) {
     if (this == o) {
       return true;
     }
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
     return os.compare(this.path, ((LocalPath) o).path) == 0;
   }

   @Override
   public int hashCode() {
     return os.hashPath(this.path);
   }

   @Override
   public int compareTo(LocalPath o) {
     return os.compare(this.path, o.path);
   }

   /**
    * An interface class representing the differences in path style between different OSs.
    *
    * <p>Eg. case sensitivity, '/' mounts vs. 'C:/', etc.
    */
   @VisibleForTesting
   interface OsPathPolicy {
     int NORMALIZED = 0; // Path is normalized
     int NEEDS_NORMALIZE = 1; // Path requires normalization

     /** Returns required normalization level, passed to {@link #normalize}. */
     int needsToNormalize(String path);

     /**
      * Normalizes the passed string according to the passed normalization level.
      *
      * @param normalizationLevel The normalizationLevel from {@link #needsToNormalize}
      */
     String normalize(String path, int normalizationLevel);

     /**
      * Returns the length of the mount, eg. 1 for unix '/', 3 for Windows 'C:/'.
      *
      * <p>If the path is relative, 0 is returned
      */
     int getDriveStrLength(String path);

     /** Compares two path strings, using the given OS case sensitivity. */
     int compare(String s1, String s2);

     /** Computes the hash code for a path string. */
     int hashPath(String s);

     /**
      * Returns whether the passed string starts with the given prefix, given the OS case
      * sensitivity.
      *
      * <p>This is a pure string operation and doesn't need to worry about matching path segments.
      */
     boolean startsWith(String path, String prefix);

     char getSeparator();

     boolean isCaseSensitive();
   }

   @VisibleForTesting
   static class UnixOsPathPolicy implements OsPathPolicy {

     @Override
     public int needsToNormalize(String path) {
       int n = path.length();
       int dotCount = 0;
       char prevChar = 0;
       for (int i = 0; i < n; i++) {
         char c = path.charAt(i);
         if (c == '/') {
           if (prevChar == '/') {
             return NEEDS_NORMALIZE;
           }
           if (dotCount == 1 || dotCount == 2) {
             return NEEDS_NORMALIZE;
           }
         }
         dotCount = c == '.' ? dotCount + 1 : 0;
         prevChar = c;
       }
       if (prevChar == '/' || dotCount == 1 || dotCount == 2) {
         return NEEDS_NORMALIZE;
       }
       return NORMALIZED;
     }

     @Override
     public String normalize(String path, int normalizationLevel) {
       if (normalizationLevel == NORMALIZED) {
         return path;
       }
       if (path.isEmpty()) {
         return path;
       }
       boolean isAbsolute = path.charAt(0) == '/';
       String[] segments = path.split("/+");
       int segmentCount = removeRelativePaths(segments, isAbsolute ? 1 : 0);
       StringBuilder sb = new StringBuilder(path.length());
       if (isAbsolute) {
         sb.append('/');
       }
       for (int i = 0; i < segmentCount; ++i) {
         sb.append(segments[i]);
         sb.append('/');
       }
       if (segmentCount > 0) {
         sb.deleteCharAt(sb.length() - 1);
       }
       return sb.toString();
     }

     @Override
     public int getDriveStrLength(String path) {
       if (path.length() == 0) {
         return 0;
       }
       return (path.charAt(0) == '/') ? 1 : 0;
     }

     @Override
     public int compare(String s1, String s2) {
       return s1.compareTo(s2);
     }

     @Override
     public int hashPath(String s) {
       return s.hashCode();
     }

     @Override
     public boolean startsWith(String path, String prefix) {
       return path.startsWith(prefix);
     }

     @Override
     public char getSeparator() {
       return '/';
     }

     @Override
     public boolean isCaseSensitive() {
       return true;
     }
   }

   /** Mac is a unix file system that is case insensitive. */
   @VisibleForTesting
   static class MacOsPathPolicy extends UnixOsPathPolicy {
     @Override
     public int compare(String s1, String s2) {
       return s1.compareToIgnoreCase(s2);
     }

     @Override
     public int hashPath(String s) {
       return s.toLowerCase().hashCode();
     }

     @Override
     public boolean isCaseSensitive() {
       return false;
     }
   }

   @VisibleForTesting
   static class WindowsOsPathPolicy implements OsPathPolicy {

     private static final int NEEDS_SHORT_PATH_NORMALIZATION = NEEDS_NORMALIZE + 1;

     // msys root, used to resolve paths from msys starting with "/"
     private static final AtomicReference<String> UNIX_ROOT = new AtomicReference<>(null);
     private final ShortPathResolver shortPathResolver;

     interface ShortPathResolver {
       String resolveShortPath(String path);
     }

     static class DefaultShortPathResolver implements ShortPathResolver {
       @Override
       public String resolveShortPath(String path) {
         try {
           return WindowsFileOperations.getLongPath(path);
         } catch (IOException e) {
           return path;
         }
       }
     }

     WindowsOsPathPolicy() {
       this(new DefaultShortPathResolver());
     }

     WindowsOsPathPolicy(ShortPathResolver shortPathResolver) {
       this.shortPathResolver = shortPathResolver;
     }

     @Override
     public int needsToNormalize(String path) {
       int n = path.length();
       int normalizationLevel = 0;
       // Check for unix path
       if (n > 0 && path.charAt(0) == '/') {
         normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
       }
       int dotCount = 0;
       char prevChar = 0;
       int segmentBeginIndex = 0; // The start index of the current path index
       boolean segmentHasShortPathChar = false; // Triggers more expensive short path regex test
       for (int i = 0; i < n; i++) {
         char c = path.charAt(i);
         if (c == '/' || c == '\\') {
           if (c == '\\') {
             normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
           }
           // No need to check for '\' here because that already causes normalization
           if (prevChar == '/') {
             normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
           }
           if (dotCount == 1 || dotCount == 2) {
             normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
           }
           if (segmentHasShortPathChar) {
             if (WindowsShortPath.isShortPath(path.substring(segmentBeginIndex, i))) {
               normalizationLevel = Math.max(normalizationLevel, NEEDS_SHORT_PATH_NORMALIZATION);
             }
           }
           segmentBeginIndex = i + 1;
           segmentHasShortPathChar = false;
         } else if (c == '~') {
           // This path segment might be a Windows short path segment
           segmentHasShortPathChar = true;
         }
         dotCount = c == '.' ? dotCount + 1 : 0;
         prevChar = c;
       }
       if (prevChar == '/' || dotCount == 1 || dotCount == 2) {
         normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
       }
       return normalizationLevel;
     }

     @Override
     public String normalize(String path, int normalizationLevel) {
       if (normalizationLevel == NORMALIZED) {
         return path;
       }
       if (normalizationLevel == NEEDS_SHORT_PATH_NORMALIZATION) {
         String resolvedPath = shortPathResolver.resolveShortPath(path);
         if (resolvedPath != null) {
           path = resolvedPath;
         }
       }
       String[] segments = path.split("[\\\\/]+");
       int driveStrLength = getDriveStrLength(path);
       boolean isAbsolute = driveStrLength > 0;
       int segmentSkipCount = isAbsolute ? 1 : 0;

       StringBuilder sb = new StringBuilder(path.length());
       if (isAbsolute) {
         char driveLetter = path.charAt(0);
         sb.append(Character.toUpperCase(driveLetter));
         sb.append(":/");
       }
       // unix path support
       if (!path.isEmpty() && path.charAt(0) == '/') {
         if (path.length() == 2 || (path.length() > 2 && path.charAt(2) == '/')) {
           sb.append(Character.toUpperCase(path.charAt(1)));
           sb.append(":/");
           segmentSkipCount = 2;
         } else {
           String unixRoot = getUnixRoot();
           sb.append(unixRoot);
         }
       }
       int segmentCount = removeRelativePaths(segments, segmentSkipCount);
       for (int i = 0; i < segmentCount; ++i) {
         sb.append(segments[i]);
         sb.append('/');
       }
       if (segmentCount > 0) {
         sb.deleteCharAt(sb.length() - 1);
       }
       return sb.toString();
     }

     @Override
     public int getDriveStrLength(String path) {
       int n = path.length();
       if (n < 3) {
         return 0;
       }
       if (isDriveLetter(path.charAt(0))
           && path.charAt(1) == ':'
           && (path.charAt(2) == '/' || path.charAt(2) == '\\')) {
         return 3;
       }
       return 0;
     }

     private static boolean isDriveLetter(char c) {
       return ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z'));
     }

     @Override
     public int compare(String s1, String s2) {
       // Windows is case-insensitive
       return s1.compareToIgnoreCase(s2);
     }

     @Override
     public int hashPath(String s) {
       // Windows is case-insensitive
       return s.toLowerCase().hashCode();
     }

     @Override
     public boolean startsWith(String path, String prefix) {
       int pathn = path.length();
       int prefixn = prefix.length();
       if (pathn < prefixn) {
         return false;
       }
       for (int i = 0; i < prefixn; ++i) {
         if (Character.toLowerCase(path.charAt(i)) != Character.toLowerCase(prefix.charAt(i))) {
           return false;
         }
       }
       return true;
     }

     @Override
     public char getSeparator() {
       return '/';
     }

     @Override
     public boolean isCaseSensitive() {
       return false;
     }

     private String getUnixRoot() {
       String value = UNIX_ROOT.get();
       if (value == null) {
         String jvmFlag = "bazel.windows_unix_root";
         value = determineUnixRoot(jvmFlag);
         if (value == null) {
           throw new IllegalStateException(
               String.format(
                   "\"%1$s\" JVM flag is not set. Use the --host_jvm_args flag or export the "
                       + "BAZEL_SH environment variable. For example "
                       + "\"--host_jvm_args=-D%1$s=c:/tools/msys64\" or "
                       + "\"set BAZEL_SH=c:/tools/msys64/usr/bin/bash.exe\".",
                   jvmFlag));
         }
         if (getDriveStrLength(value) != 3) {
           throw new IllegalStateException(
               String.format("\"%s\" must be an absolute path, got: \"%s\"", jvmFlag, value));
         }
         value = value.replace('\\', '/');
         if (value.length() > 3 && value.endsWith("/")) {
           value = value.substring(0, value.length() - 1);
         }
         UNIX_ROOT.set(value);
       }
       return value;
     }

     private String determineUnixRoot(String jvmArgName) {
       // Get the path from a JVM flag, if specified.
       String path = System.getProperty(jvmArgName);
       if (path == null) {
         return null;
       }
       path = path.trim();
       if (path.isEmpty()) {
         return null;
       }
       return path;
     }
   }

   private static OsPathPolicy createFilePathOs() {
     switch (OS.getCurrent()) {
       case LINUX:
       case FREEBSD:
       case UNKNOWN:
         return new UnixOsPathPolicy();
       case DARWIN:
         return new MacOsPathPolicy();
       case WINDOWS:
         return new WindowsOsPathPolicy();
       default:
         throw new AssertionError("Not covering all OSs");
     }
   }

   /**
    * Normalizes any '.' and '..' in-place in the segment array by shifting other segments to the
    * front. Returns the remaining number of items.
    */
   private static int removeRelativePaths(String[] segments, int starti) {
     int segmentCount = 0;
     int shift = starti;
     for (int i = starti; i < segments.length; ++i) {
       String segment = segments[i];
       switch (segment) {
         case ".":
           // Just discard it
           ++shift;
           break;
         case "..":
           if (segmentCount > 0 && !segments[segmentCount - 1].equals("..")) {
             // Remove the last segment, if there is one and it is not "..". This
             // means that the resulting path can still contain ".."
             // segments at the beginning.
             segmentCount--;
             shift += 2;
             break;
           }
           // Fall through
         default:
           ++segmentCount;
           if (shift > 0) {
             segments[i - shift] = segments[i];
           }
           break;
       }
     }
     return segmentCount;
   }
 }
	// Copyright 2017 The Bazel Authors. All rights reserved.
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.
	package com.google.devtools.build.lib.vfs;

	import com.google.common.annotations.VisibleForTesting;
	import com.google.common.base.Preconditions;
	import com.google.devtools.build.lib.util.OS;
	import com.google.devtools.build.lib.windows.WindowsShortPath;
	import com.google.devtools.build.lib.windows.jni.WindowsFileOperations;
	import java.io.IOException;
	import java.util.Arrays;
	import java.util.concurrent.atomic.AtomicReference;
	import javax.annotation.Nullable;

	/**
	* A local file path representing a file on the host machine. You should use this when you want to
	* access local files via the file system.
	*
	* <p>Paths are either absolute or relative.
	*
	* <p>Strings are normalized with '.' and '..' removed and resolved (if possible), any multiple
	* slashes ('/') removed, and any trailing slash also removed. The current implementation does not
	* touch the incoming path string unless the string actually needs to be normalized.
	*
	* <p>There is some limited support for Windows-style paths. Most importantly, drive identifiers in
	* front of a path (c:/abc) are supported and such paths are correctly recognized as absolute, as
	* are paths with backslash separators (C:\\foo\\bar). However, advanced Windows-style features like
	* \\\\network\\paths and \\\\?\\unc\\paths are not supported. We are currently using forward
	* slashes ('/') even on Windows, so backslashes '\' get converted to forward slashes during
	* normalization.
	*
	* <p>Mac and Windows file paths are case insensitive. Case is preserved.
	*
	* <p>This class is replaces {@link Path} as the way to access the host machine's file system.
	* Developers should use this class instead of {@link Path}.
	*/
	public final class LocalPath implements Comparable<LocalPath> {
	private static final OsPathPolicy DEFAULT_OS = createFilePathOs();

	public static final LocalPath EMPTY = create("");

	private final String path;
	private final int driveStrLength; // 0 for relative paths, 1 on Unix, 3 on Windows
	private final OsPathPolicy os;

	/** Creates a local path that is specific to the host OS. */
	public static LocalPath create(String path) {
	return createWithOs(path, DEFAULT_OS);
	}

	@VisibleForTesting
	static LocalPath createWithOs(String path, OsPathPolicy os) {
	Preconditions.checkNotNull(path);
	int normalizationLevel = os.needsToNormalize(path);
	String normalizedPath = os.normalize(path, normalizationLevel);
	int driveStrLength = os.getDriveStrLength(normalizedPath);
	return new LocalPath(normalizedPath, driveStrLength, os);
	}

	/** This method expects path to already be normalized. */
	private LocalPath(String path, int driveStrLength, OsPathPolicy os) {
	this.path = Preconditions.checkNotNull(path);
	this.driveStrLength = driveStrLength;
	this.os = Preconditions.checkNotNull(os);
	}

	public String getPathString() {
	return path;
	}

	/**
	* If called on a {@link LocalPath} instance for a mount name (eg. '/' or 'C:/'), the empty string
	* is returned.
	*/
	public String getBaseName() {
	int lastSeparator = path.lastIndexOf(os.getSeparator());
	return lastSeparator < driveStrLength
	? path.substring(driveStrLength)
	: path.substring(lastSeparator + 1);
	}

	/**
	* Returns a {@link LocalPath} instance representing the relative path between this {@link
	* LocalPath} and the given {@link LocalPath}.
	*
	* <pre>
	* Example:
	*
	* LocalPath.create("/foo").getRelative(LocalPath.create("bar/baz"))
	* -> "/foo/bar/baz"
	* </pre>
	*
	* <p>If the passed path is absolute it is returned untouched. This can be useful to resolve
	* symlinks.
	*/
	public LocalPath getRelative(LocalPath other) {
	Preconditions.checkNotNull(other);
	Preconditions.checkArgument(os == other.os);
	return getRelative(other.getPathString(), other.driveStrLength);
	}

	/**
	* Returns a {@link LocalPath} instance representing the relative path between this {@link
	* LocalPath} and the given path.
	*
	* <p>See {@link #getRelative(LocalPath)} for details.
	*/
	public LocalPath getRelative(String other) {
	Preconditions.checkNotNull(other);
	return getRelative(other, os.getDriveStrLength(other));
	}

	private LocalPath getRelative(String other, int otherDriveStrLength) {
	if (path.isEmpty()) {
	return create(other);
	}
	if (other.isEmpty()) {
	return this;
	}
	// Note that even if other came from a LocalPath instance we still might
	// need to normalize the result if (for instance) other is a path that
	// starts with '..'
	int normalizationLevel = os.needsToNormalize(other);
	// This is an absolute path, simply return it
	if (otherDriveStrLength > 0) {
	String normalizedPath = os.normalize(other, normalizationLevel);
	return new LocalPath(normalizedPath, otherDriveStrLength, os);
	}
	String newPath;
	if (path.length() == driveStrLength) {
	newPath = path + other;
	} else {
	newPath = path + '/' + other;
	}
	newPath = os.normalize(newPath, normalizationLevel);
	return new LocalPath(newPath, driveStrLength, os);
	}

	/**
	* Returns the parent directory of this {@link LocalPath}.
	*
	* <p>If this is called on an single directory for a relative path, this returns an empty relative
	* path. If it's called on a root (like '/') or the empty string, it returns null.
	*/
	@Nullable
	public LocalPath getParentDirectory() {
	int lastSeparator = path.lastIndexOf(os.getSeparator());

	// For absolute paths we need to specially handle when we hit root
	// Relative paths can't hit this path as driveStrLength == 0
	if (driveStrLength > 0) {
	if (lastSeparator < driveStrLength) {
	if (path.length() > driveStrLength) {
	String newPath = path.substring(0, driveStrLength);
	return new LocalPath(newPath, driveStrLength, os);
	} else {
	return null;
	}
	}
	} else {
	if (lastSeparator == -1) {
	if (!path.isEmpty()) {
	return EMPTY;
	} else {
	return null;
	}
	}
	}
	String newPath = path.substring(0, lastSeparator);
	return new LocalPath(newPath, driveStrLength, os);
	}

	/**
	* Returns the {@link LocalPath} relative to the base {@link LocalPath}.
	*
	* <p>For example, <code>LocalPath.create("foo/bar/wiz").relativeTo(LocalPath.create("foo"))
	* </code> returns <code>LocalPath.create("bar/wiz")</code>.
	*
	* <p>If the {@link LocalPath} is not a child of the passed {@link LocalPath} an {@link
	* IllegalArgumentException} is thrown. In particular, this will happen whenever the two {@link
	* LocalPath} instances aren't both absolute or both relative.
	*/
	public LocalPath relativeTo(LocalPath base) {
	Preconditions.checkNotNull(base);
	Preconditions.checkArgument(os == base.os);
	if (isAbsolute() != base.isAbsolute()) {
	throw new IllegalArgumentException(
	"Cannot relativize an absolute and a non-absolute path pair");
	}
	String basePath = base.path;
	if (!os.startsWith(path, basePath)) {
	throw new IllegalArgumentException(
	String.format("Path '%s' is not under '%s', cannot relativize", this, base));
	}
	int bn = basePath.length();
	if (bn == 0) {
	return this;
	}
	if (path.length() == bn) {
	return EMPTY;
	}
	final int lastSlashIndex;
	if (basePath.charAt(bn - 1) == '/') {
	lastSlashIndex = bn - 1;
	} else {
	lastSlashIndex = bn;
	}
	if (path.charAt(lastSlashIndex) != '/') {
	throw new IllegalArgumentException(
	String.format("Path '%s' is not under '%s', cannot relativize", this, base));
	}
	String newPath = path.substring(lastSlashIndex + 1);
	return new LocalPath(newPath, 0 /* Always a relative path */, os);
	}

	/**
	* Splits a path into its constituent parts. The root is not included. This is an inefficient
	* operation and should be avoided.
	*/
	public String[] split() {
	String[] segments = path.split("/");
	if (driveStrLength > 0) {
	// String#split("/") for some reason returns a zero-length array
	// String#split("/hello") returns a 2-length array, so this makes little sense
	if (segments.length == 0) {
	return segments;
	}
	return Arrays.copyOfRange(segments, 1, segments.length);
	}
	return segments;
	}

	/**
	* Returns whether this path is an ancestor of another path.
	*
	* <p>A path is considered an ancestor of itself.
	*
	* <p>An absolute path can never be an ancestor of a relative path, and vice versa.
	*/
	public boolean startsWith(LocalPath other) {
	Preconditions.checkNotNull(other);
	Preconditions.checkArgument(os == other.os);
	if (other.path.length() > path.length()) {
	return false;
	}
	if (driveStrLength != other.driveStrLength) {
	return false;
	}
	if (!os.startsWith(path, other.path)) {
	return false;
	}
	return path.length() == other.path.length()
	\|\| other.path.length() == driveStrLength
	\|\| path.charAt(other.path.length()) == os.getSeparator();
	}

	public boolean isAbsolute() {
	return driveStrLength > 0;
	}

	@Override
	public String toString() {
	return path;
	}

	@Override
	public boolean equals(Object o) {
	if (this == o) {
	return true;
	}
	if (o == null \|\| getClass() != o.getClass()) {
	return false;
	}
	return os.compare(this.path, ((LocalPath) o).path) == 0;
	}

	@Override
	public int hashCode() {
	return os.hashPath(this.path);
	}

	@Override
	public int compareTo(LocalPath o) {
	return os.compare(this.path, o.path);
	}

	/**
	* An interface class representing the differences in path style between different OSs.
	*
	* <p>Eg. case sensitivity, '/' mounts vs. 'C:/', etc.
	*/
	@VisibleForTesting
	interface OsPathPolicy {
	int NORMALIZED = 0; // Path is normalized
	int NEEDS_NORMALIZE = 1; // Path requires normalization

	/** Returns required normalization level, passed to {@link #normalize}. */
	int needsToNormalize(String path);

	/**
	* Normalizes the passed string according to the passed normalization level.
	*
	* @param normalizationLevel The normalizationLevel from {@link #needsToNormalize}
	*/
	String normalize(String path, int normalizationLevel);

	/**
	* Returns the length of the mount, eg. 1 for unix '/', 3 for Windows 'C:/'.
	*
	* <p>If the path is relative, 0 is returned
	*/
	int getDriveStrLength(String path);

	/** Compares two path strings, using the given OS case sensitivity. */
	int compare(String s1, String s2);

	/** Computes the hash code for a path string. */
	int hashPath(String s);

	/**
	* Returns whether the passed string starts with the given prefix, given the OS case
	* sensitivity.
	*
	* <p>This is a pure string operation and doesn't need to worry about matching path segments.
	*/
	boolean startsWith(String path, String prefix);

	char getSeparator();

	boolean isCaseSensitive();
	}

	@VisibleForTesting
	static class UnixOsPathPolicy implements OsPathPolicy {

	@Override
	public int needsToNormalize(String path) {
	int n = path.length();
	int dotCount = 0;
	char prevChar = 0;
	for (int i = 0; i < n; i++) {
	char c = path.charAt(i);
	if (c == '/') {
	if (prevChar == '/') {
	return NEEDS_NORMALIZE;
	}
	if (dotCount == 1 \|\| dotCount == 2) {
	return NEEDS_NORMALIZE;
	}
	}
	dotCount = c == '.' ? dotCount + 1 : 0;
	prevChar = c;
	}
	if (prevChar == '/' \|\| dotCount == 1 \|\| dotCount == 2) {
	return NEEDS_NORMALIZE;
	}
	return NORMALIZED;
	}

	@Override
	public String normalize(String path, int normalizationLevel) {
	if (normalizationLevel == NORMALIZED) {
	return path;
	}
	if (path.isEmpty()) {
	return path;
	}
	boolean isAbsolute = path.charAt(0) == '/';
	String[] segments = path.split("/+");
	int segmentCount = removeRelativePaths(segments, isAbsolute ? 1 : 0);
	StringBuilder sb = new StringBuilder(path.length());
	if (isAbsolute) {
	sb.append('/');
	}
	for (int i = 0; i < segmentCount; ++i) {
	sb.append(segments[i]);
	sb.append('/');
	}
	if (segmentCount > 0) {
	sb.deleteCharAt(sb.length() - 1);
	}
	return sb.toString();
	}

	@Override
	public int getDriveStrLength(String path) {
	if (path.length() == 0) {
	return 0;
	}
	return (path.charAt(0) == '/') ? 1 : 0;
	}

	@Override
	public int compare(String s1, String s2) {
	return s1.compareTo(s2);
	}

	@Override
	public int hashPath(String s) {
	return s.hashCode();
	}

	@Override
	public boolean startsWith(String path, String prefix) {
	return path.startsWith(prefix);
	}

	@Override
	public char getSeparator() {
	return '/';
	}

	@Override
	public boolean isCaseSensitive() {
	return true;
	}
	}

	/** Mac is a unix file system that is case insensitive. */
	@VisibleForTesting
	static class MacOsPathPolicy extends UnixOsPathPolicy {
	@Override
	public int compare(String s1, String s2) {
	return s1.compareToIgnoreCase(s2);
	}

	@Override
	public int hashPath(String s) {
	return s.toLowerCase().hashCode();
	}

	@Override
	public boolean isCaseSensitive() {
	return false;
	}
	}

	@VisibleForTesting
	static class WindowsOsPathPolicy implements OsPathPolicy {

	private static final int NEEDS_SHORT_PATH_NORMALIZATION = NEEDS_NORMALIZE + 1;

	// msys root, used to resolve paths from msys starting with "/"
	private static final AtomicReference<String> UNIX_ROOT = new AtomicReference<>(null);
	private final ShortPathResolver shortPathResolver;

	interface ShortPathResolver {
	String resolveShortPath(String path);
	}

	static class DefaultShortPathResolver implements ShortPathResolver {
	@Override
	public String resolveShortPath(String path) {
	try {
	return WindowsFileOperations.getLongPath(path);
	} catch (IOException e) {
	return path;
	}
	}
	}

	WindowsOsPathPolicy() {
	this(new DefaultShortPathResolver());
	}

	WindowsOsPathPolicy(ShortPathResolver shortPathResolver) {
	this.shortPathResolver = shortPathResolver;
	}

	@Override
	public int needsToNormalize(String path) {
	int n = path.length();
	int normalizationLevel = 0;
	// Check for unix path
	if (n > 0 && path.charAt(0) == '/') {
	normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
	}
	int dotCount = 0;
	char prevChar = 0;
	int segmentBeginIndex = 0; // The start index of the current path index
	boolean segmentHasShortPathChar = false; // Triggers more expensive short path regex test
	for (int i = 0; i < n; i++) {
	char c = path.charAt(i);
	if (c == '/' \|\| c == '\\') {
	if (c == '\\') {
	normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
	}
	// No need to check for '\' here because that already causes normalization
	if (prevChar == '/') {
	normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
	}
	if (dotCount == 1 \|\| dotCount == 2) {
	normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
	}
	if (segmentHasShortPathChar) {
	if (WindowsShortPath.isShortPath(path.substring(segmentBeginIndex, i))) {
	normalizationLevel = Math.max(normalizationLevel, NEEDS_SHORT_PATH_NORMALIZATION);
	}
	}
	segmentBeginIndex = i + 1;
	segmentHasShortPathChar = false;
	} else if (c == '~') {
	// This path segment might be a Windows short path segment
	segmentHasShortPathChar = true;
	}
	dotCount = c == '.' ? dotCount + 1 : 0;
	prevChar = c;
	}
	if (prevChar == '/' \|\| dotCount == 1 \|\| dotCount == 2) {
	normalizationLevel = Math.max(normalizationLevel, NEEDS_NORMALIZE);
	}
	return normalizationLevel;
	}

	@Override
	public String normalize(String path, int normalizationLevel) {
	if (normalizationLevel == NORMALIZED) {
	return path;
	}
	if (normalizationLevel == NEEDS_SHORT_PATH_NORMALIZATION) {
	String resolvedPath = shortPathResolver.resolveShortPath(path);
	if (resolvedPath != null) {
	path = resolvedPath;
	}
	}
	String[] segments = path.split("[\\\\/]+");
	int driveStrLength = getDriveStrLength(path);
	boolean isAbsolute = driveStrLength > 0;
	int segmentSkipCount = isAbsolute ? 1 : 0;

	StringBuilder sb = new StringBuilder(path.length());
	if (isAbsolute) {
	char driveLetter = path.charAt(0);
	sb.append(Character.toUpperCase(driveLetter));
	sb.append(":/");
	}
	// unix path support
	if (!path.isEmpty() && path.charAt(0) == '/') {
	if (path.length() == 2 \|\| (path.length() > 2 && path.charAt(2) == '/')) {
	sb.append(Character.toUpperCase(path.charAt(1)));
	sb.append(":/");
	segmentSkipCount = 2;
	} else {
	String unixRoot = getUnixRoot();
	sb.append(unixRoot);
	}
	}
	int segmentCount = removeRelativePaths(segments, segmentSkipCount);
	for (int i = 0; i < segmentCount; ++i) {
	sb.append(segments[i]);
	sb.append('/');
	}
	if (segmentCount > 0) {
	sb.deleteCharAt(sb.length() - 1);
	}
	return sb.toString();
	}

	@Override
	public int getDriveStrLength(String path) {
	int n = path.length();
	if (n < 3) {
	return 0;
	}
	if (isDriveLetter(path.charAt(0))
	&& path.charAt(1) == ':'
	&& (path.charAt(2) == '/' \|\| path.charAt(2) == '\\')) {
	return 3;
	}
	return 0;
	}

	private static boolean isDriveLetter(char c) {
	return ((c >= 'a') && (c <= 'z')) \|\| ((c >= 'A') && (c <= 'Z'));
	}

	@Override
	public int compare(String s1, String s2) {
	// Windows is case-insensitive
	return s1.compareToIgnoreCase(s2);
	}

	@Override
	public int hashPath(String s) {
	// Windows is case-insensitive
	return s.toLowerCase().hashCode();
	}

	@Override
	public boolean startsWith(String path, String prefix) {
	int pathn = path.length();
	int prefixn = prefix.length();
	if (pathn < prefixn) {
	return false;
	}
	for (int i = 0; i < prefixn; ++i) {
	if (Character.toLowerCase(path.charAt(i)) != Character.toLowerCase(prefix.charAt(i))) {
	return false;
	}
	}
	return true;
	}

	@Override
	public char getSeparator() {
	return '/';
	}

	@Override
	public boolean isCaseSensitive() {
	return false;
	}

	private String getUnixRoot() {
	String value = UNIX_ROOT.get();
	if (value == null) {
	String jvmFlag = "bazel.windows_unix_root";
	value = determineUnixRoot(jvmFlag);
	if (value == null) {
	throw new IllegalStateException(
	String.format(
	"\"%1$s\" JVM flag is not set. Use the --host_jvm_args flag or export the "
	+ "BAZEL_SH environment variable. For example "
	+ "\"--host_jvm_args=-D%1$s=c:/tools/msys64\" or "
	+ "\"set BAZEL_SH=c:/tools/msys64/usr/bin/bash.exe\".",
	jvmFlag));
	}
	if (getDriveStrLength(value) != 3) {
	throw new IllegalStateException(
	String.format("\"%s\" must be an absolute path, got: \"%s\"", jvmFlag, value));
	}
	value = value.replace('\\', '/');
	if (value.length() > 3 && value.endsWith("/")) {
	value = value.substring(0, value.length() - 1);
	}
	UNIX_ROOT.set(value);
	}
	return value;
	}

	private String determineUnixRoot(String jvmArgName) {
	// Get the path from a JVM flag, if specified.
	String path = System.getProperty(jvmArgName);
	if (path == null) {
	return null;
	}
	path = path.trim();
	if (path.isEmpty()) {
	return null;
	}
	return path;
	}
	}

	private static OsPathPolicy createFilePathOs() {
	switch (OS.getCurrent()) {
	case LINUX:
	case FREEBSD:
	case UNKNOWN:
	return new UnixOsPathPolicy();
	case DARWIN:
	return new MacOsPathPolicy();
	case WINDOWS:
	return new WindowsOsPathPolicy();
	default:
	throw new AssertionError("Not covering all OSs");
	}
	}

	/**
	* Normalizes any '.' and '..' in-place in the segment array by shifting other segments to the
	* front. Returns the remaining number of items.
	*/
	private static int removeRelativePaths(String[] segments, int starti) {
	int segmentCount = 0;
	int shift = starti;
	for (int i = starti; i < segments.length; ++i) {
	String segment = segments[i];
	switch (segment) {
	case ".":
	// Just discard it
	++shift;
	break;
	case "..":
	if (segmentCount > 0 && !segments[segmentCount - 1].equals("..")) {
	// Remove the last segment, if there is one and it is not "..". This
	// means that the resulting path can still contain ".."
	// segments at the beginning.
	segmentCount--;
	shift += 2;
	break;
	}
	// Fall through
	default:
	++segmentCount;
	if (shift > 0) {
	segments[i - shift] = segments[i];
	}
	break;
	}
	}
	return segmentCount;
	}
	}