// Copyright 2016 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.windows.jni; import java.io.IOException; /** File operations on Windows. */ public class WindowsFileOperations { // A note about UNC paths and path prefixes on Windows. The prefixes can be: // - "\\?\", meaning it's a UNC path that is passed to user mode unicode WinAPI functions // (e.g. CreateFileW) or a return value of theirs (e.g. GetLongPathNameW); this is the // prefix we'll most often see // - "\??\", meaning it's Device Object path; it's mostly only used by kernel/driver functions // but we may come across it when resolving junction targets, as the target's path is // specified with this prefix, see usages of DeviceIoControl with FSCTL_GET_REPARSE_POINT // - "\\.\", meaning it's a Device Object path again; both "\??\" and "\\.\" are shorthands // for the "\DosDevices\" Object Directory, so "\\.\C:" and "\??\C:" and "\DosDevices\C:" // and "C:\" all mean the same thing, but functions like CreateFileW don't understand the // fully qualified device path, only the shorthand versions; the difference between "\\.\" // is "\??\" is not entirely clear (one is not available while Windows is booting, but // that only concerns device drivers) but we most likely won't come across them anyway // Some of this is documented here: // - https://msdn.microsoft.com/en-us/library/windows/hardware/ff557762(v=vs.85).aspx // - https://msdn.microsoft.com/en-us/library/windows/hardware/ff565384(v=vs.85).aspx // - http://stackoverflow.com/questions/23041983 // - http://stackoverflow.com/questions/14482421 private WindowsFileOperations() { // Prevent construction } private static final int MAX_PATH = 260; // Keep IS_JUNCTION_* values in sync with src/main/native/windows/file.cc. private static final int IS_JUNCTION_YES = 0; private static final int IS_JUNCTION_NO = 1; private static final int IS_JUNCTION_ERROR = 2; // Keep CREATE_JUNCTION_* values in sync with src/main/native/windows/file.cc. private static final int CREATE_JUNCTION_SUCCESS = 0; private static final int CREATE_JUNCTION_ERROR = 1; private static final int CREATE_JUNCTION_TARGET_NAME_TOO_LONG = 2; private static final int CREATE_JUNCTION_ALREADY_EXISTS_WITH_DIFFERENT_TARGET = 3; private static final int CREATE_JUNCTION_ALREADY_EXISTS_BUT_NOT_A_JUNCTION = 4; private static final int CREATE_JUNCTION_ACCESS_DENIED = 5; private static final int CREATE_JUNCTION_DISAPPEARED = 6; // Keep DELETE_PATH_* values in sync with src/main/native/windows/file.cc. private static final int DELETE_PATH_SUCCESS = 0; private static final int DELETE_PATH_ERROR = 1; private static final int DELETE_PATH_DOES_NOT_EXIST = 2; private static final int DELETE_PATH_DIRECTORY_NOT_EMPTY = 3; private static final int DELETE_PATH_ACCESS_DENIED = 4; private static native int nativeIsJunction(String path, String[] error); private static native boolean nativeGetLongPath(String path, String[] result, String[] error); private static native int nativeCreateJunction(String name, String target, String[] error); private static native int nativeDeletePath(String path, String[] error); /** Determines whether `path` is a junction point or directory symlink. */ public static boolean isJunction(String path) throws IOException { WindowsJniLoader.loadJni(); String[] error = new String[] {null}; switch (nativeIsJunction(asLongPath(path), error)) { case IS_JUNCTION_YES: return true; case IS_JUNCTION_NO: return false; default: throw new IOException(error[0]); } } /** * Returns the long path associated with the input `path`. * *
This method resolves all 8dot3 style components of the path and returns the long format. For * example, if the input is "C:/progra~1/micros~1" the result may be "C:\Program Files\Microsoft * Visual Studio 14.0". The returned path is Windows-style in that it uses backslashes, even if * the input uses forward slashes. * *
May return an UNC path if `path` or its resolution is sufficiently long. * * @throws IOException if the `path` is not found or some other I/O error occurs */ public static String getLongPath(String path) throws IOException { WindowsJniLoader.loadJni(); String[] result = new String[] {null}; String[] error = new String[] {null}; if (nativeGetLongPath(asLongPath(path), result, error)) { return result[0]; } else { throw new IOException(error[0]); } } /** * Returns a Windows-style path suitable to pass to unicode WinAPI functions. * *
Returns an UNC path if `path` is at least `MAX_PATH` long. If it's shorter or is already an * UNC path, then this method returns `path` itself. */ static String asLongPath(String path) { return path.length() >= MAX_PATH && !path.startsWith("\\\\?\\") ? ("\\\\?\\" + path.replace('/', '\\')) : path; } /** * Creates a junction at `name`, pointing to `target`. * *
Both `name` and `target` may be Unix-style Windows paths (i.e. use forward slashes), and * they don't need to have a UNC prefix, not even if they are longer than `MAX_PATH`. The * underlying logic will take care of adding the prefixes if necessary. * * @throws IOException if some error occurs */ public static void createJunction(String name, String target) throws IOException { WindowsJniLoader.loadJni(); String[] error = new String[] {null}; int result = nativeCreateJunction(name.replace('/', '\\'), target.replace('/', '\\'), error); if (result != CREATE_JUNCTION_SUCCESS) { switch (result) { case CREATE_JUNCTION_TARGET_NAME_TOO_LONG: error[0] = "target name is too long"; break; case CREATE_JUNCTION_ALREADY_EXISTS_WITH_DIFFERENT_TARGET: error[0] = "junction already exists with different target"; break; case CREATE_JUNCTION_ALREADY_EXISTS_BUT_NOT_A_JUNCTION: error[0] = "a file or directory already exists at the junction's path"; break; case CREATE_JUNCTION_ACCESS_DENIED: error[0] = "access is denied"; break; case CREATE_JUNCTION_DISAPPEARED: error[0] = "the junction's path got modified unexpectedly"; break; default: break; } throw new IOException( String.format("Cannot create junction (name=%s, target=%s): %s", name, target, error[0])); } } public static boolean deletePath(String path) throws IOException { WindowsJniLoader.loadJni(); String[] error = new String[] {null}; int result = nativeDeletePath(asLongPath(path), error); switch (result) { case DELETE_PATH_SUCCESS: return true; case DELETE_PATH_DOES_NOT_EXIST: return false; case DELETE_PATH_DIRECTORY_NOT_EMPTY: throw new java.nio.file.DirectoryNotEmptyException(path); case DELETE_PATH_ACCESS_DENIED: throw new java.nio.file.AccessDeniedException(path); default: throw new IOException(String.format("Cannot delete path '%s': %s", path, error[0])); } } }