Java tutorial
/* * Copyright 2008 The Closure Compiler Authors. * * 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.javascript.jscomp.deps; import static com.google.common.base.StandardSystemProperty.USER_DIR; import com.google.common.base.CharMatcher; import com.google.common.base.Joiner; import com.google.common.base.Splitter; import com.google.common.base.Strings; import com.google.common.collect.Lists; import java.util.ArrayList; import java.util.Arrays; import java.util.List; /** * Utility methods for manipulation of UNIX-like paths. * NOTE: According to kevinb, equivalent methods will be in the standard library once * jsr203 is ready. * */ public final class PathUtil { private static final CharMatcher SLASH_MATCHER = CharMatcher.is('/'); private static final CharMatcher NON_SLASH_MATCHER = CharMatcher.isNot('/'); private PathUtil() { } /** * Removes all ../ and ./ entries from within the given path. If there are extra ..s that move * beyond the first directory given, they are removed. * * Examples: * "a/b/../c" results in "a/c" * "./foo/./../bar" results in "bar" * "a/.." results in "" * "a/../../foo" results in "foo" * * @param path The path to remove dots from. * @return The path with all dots collapsed. */ public static String collapseDots(String path) { path = removeExtraneousSlashes(path); // Optimization: Most paths don't contain dots. if (!path.contains(".")) { return path; } List<String> dstFragments = new ArrayList<>(); for (String fragment : Splitter.on('/').split(path)) { if (fragment.equals("..")) { if (!dstFragments.isEmpty()) { dstFragments.remove(dstFragments.size() - 1); } } else if (!fragment.equals(".")) { dstFragments.add(fragment); } } // Special case for Join.join([""]); -> "/" if (dstFragments.size() == 1 && dstFragments.get(0).isEmpty()) { return "/"; } return Joiner.on("/").join(dstFragments); } /** * Determines if a path is absolute or not by testing for the presence of "/" * at the front of the string. * * @param path The path to test * @return true if the path starts with DELIMITER, false otherwise. */ static boolean isAbsolute(String path) { return path.startsWith("/"); } /** * Removes extra slashes from a path. Leading slash is preserved, trailing * slash is stripped, and any runs of more than one slash in the middle is * replaced by a single slash. */ static String removeExtraneousSlashes(String s) { int lastNonSlash = NON_SLASH_MATCHER.lastIndexIn(s); if (lastNonSlash != -1) { s = s.substring(0, lastNonSlash + 1); } return SLASH_MATCHER.collapseFrom(s, '/'); } /** * Converts the given path into an absolute one. This prepends the current * working directory and removes all .'s from the path. If an absolute path * is given, it will not be prefixed. * * <p>Unlike File.getAbsolutePath(), this function does remove .'s from the * path and unlike File.getCanonicalPath(), this function does not resolve * symlinks and does not use filesystem calls.</p> * * @param path The path to make absolute. * @return The path made absolute. */ public static String makeAbsolute(String path) { return makeAbsolute(path, USER_DIR.value()); } /** * Converts the given path into an absolute one. This prepends the given * rootPath and removes all .'s from the path. If an absolute path is given, * it will not be prefixed. * * <p>Unlike File.getAbsolutePath(), this function does remove .'s from the * path and unlike File.getCanonicalPath(), this function does not resolve * symlinks and does not use filesystem calls.</p> * * @param rootPath The path to prefix to path if path is not already absolute. * @param path The path to make absolute. * @return The path made absolute. */ public static String makeAbsolute(String path, String rootPath) { if (!isAbsolute(path)) { path = rootPath + "/" + path; } return collapseDots(path); } /** * Returns targetPath relative to basePath. * * <p>basePath and targetPath must either both be relative, or both be * absolute paths.</p> * * <p>This function is different from makeRelative * in that it is able to add in ../ components and collapse existing ones as well.</p> * * Examples: * base="some/relative/path" target="some/relative/path/foo" return="foo" * base="some/relative/path" target="some/relative" return=".." * base="some/relative/path" target="foo/bar" return="../../../foo/bar" * base="/some/abs/path" target="/foo/bar" return="../../../foo/bar" * * @param basePath The path to make targetPath relative to. * @param targetPath The path to make relative. * @return A path relative to targetPath. The returned value will never start * with a slash. */ public static String makeRelative(String basePath, String targetPath) { // Ensure the paths are both absolute or both relative. if (isAbsolute(basePath) != isAbsolute(targetPath)) { throw new IllegalArgumentException("Paths must both be relative or both absolute.\n" + " basePath: " + basePath + "\n" + " targetPath: " + targetPath); } basePath = collapseDots(basePath); targetPath = collapseDots(targetPath); String[] baseFragments = basePath.split("/"); String[] targetFragments = targetPath.split("/"); int i = -1; do { i += 1; if (i == baseFragments.length && i == targetFragments.length) { // Eg) base: /java/com/google // target: /java/com/google // result: . <-- . is better than "" since "" + "/path" = "/path" return "."; } else if (i == baseFragments.length) { // Eg) base: /java/com/google // target: /java/com/google/c/ui // result: c/ui return Joiner.on("/").join(Lists.newArrayList(Arrays.asList(targetFragments).listIterator(i))); } else if (i == targetFragments.length) { // Eg) base: /java/com/google/c/ui // target: /java/com/google // result: ../.. return Strings.repeat("../", baseFragments.length - i - 1) + ".."; } } while (baseFragments[i].equals(targetFragments[i])); // Eg) base: /java/com/google/c // target: /java/com/google/common/base // result: ../common/base return Strings.repeat("../", baseFragments.length - i) + Joiner.on("/").join(Lists.newArrayList(Arrays.asList(targetFragments).listIterator(i))); } }