1 files changed, 309 insertions, 0 deletions
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/FileModeCache.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/FileModeCache.java
new file mode 100644
index 0000000000..073bf7a0ca
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+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/FileModeCache.java
@@ -0,0 +1,309 @@
+/*
+ * Copyright (C) 2023, Thomas Wolf <twolf@apache.org> and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.lib;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.InvalidPathException;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.attribute.BasicFileAttributeView;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.eclipse.jgit.annotations.NonNull;
+import org.eclipse.jgit.util.FS;
+import org.eclipse.jgit.util.FileUtils;
+
+/**
+ * A hierarchical cache of {@link FileMode}s per git path.
+ *
+ * @since 6.6.1
+ */
+public class FileModeCache {
+
+	@NonNull
+	private final CacheItem root = new CacheItem(FileMode.TREE);
+
+	@NonNull
+	private final Repository repo;
+
+	/**
+	 * Creates a new {@link FileModeCache} for a {@link Repository}.
+	 *
+	 * @param repo
+	 *            {@link Repository} this cache is for
+	 */
+	public FileModeCache(@NonNull Repository repo) {
+		this.repo = repo;
+	}
+
+	/**
+	 * Retrieves the {@link Repository}.
+	 *
+	 * @return the {@link Repository} this {@link FileModeCache} was created for
+	 */
+	@NonNull
+	public Repository getRepository() {
+		return repo;
+	}
+
+	/**
+	 * Obtains the {@link CacheItem} for the working tree root.
+	 *
+	 * @return the {@link CacheItem}
+	 */
+	@NonNull
+	public CacheItem getRoot() {
+		return root;
+	}
+
+	/**
+	 * Ensure that the given parent directory exists, and cache the information
+	 * that gitPath refers to a file.
+	 *
+	 * @param gitPath
+	 *            of the file to be written
+	 * @param parentDir
+	 *            directory in which the file shall be placed, assumed to be the
+	 *            parent of the {@code gitPath}
+	 * @param makeSpace
+	 *            whether to delete a possibly existing file at
+	 *            {@code parentDir}
+	 * @throws IOException
+	 *             if the directory cannot be created, if necessary
+	 */
+	public void safeCreateParentDirectory(String gitPath, File parentDir,
+			boolean makeSpace) throws IOException {
+		CacheItem cachedParent = safeCreateDirectory(gitPath, parentDir,
+				makeSpace);
+		cachedParent.remove(gitPath.substring(gitPath.lastIndexOf('/') + 1));
+	}
+
+	/**
+	 * Ensures the given directory {@code dir} with the given git path exists.
+	 *
+	 * @param gitPath
+	 *            of a file to be written
+	 * @param dir
+	 *            directory in which the file shall be placed, assumed to be the
+	 *            parent of the {@code gitPath}
+	 * @param makeSpace
+	 *            whether to remove a file that already at that name
+	 * @return A {@link CacheItem} describing the directory, which is guaranteed
+	 *         to exist
+	 * @throws IOException
+	 *             if the directory cannot be made to exist at the given
+	 *             location
+	 */
+	public CacheItem safeCreateDirectory(String gitPath, File dir,
+			boolean makeSpace) throws IOException {
+		FS fs = repo.getFS();
+		int i = gitPath.lastIndexOf('/');
+		String parentPath = null;
+		if (i >= 0) {
+			if ((makeSpace && dir.isFile()) || fs.isSymLink(dir)) {
+				FileUtils.delete(dir);
+			}
+			parentPath = gitPath.substring(0, i);
+			deleteSymlinkParent(fs, parentPath, repo.getWorkTree());
+		}
+		FileUtils.mkdirs(dir, true);
+		CacheItem cachedParent = getRoot();
+		if (parentPath != null) {
+			cachedParent = add(parentPath, FileMode.TREE);
+		}
+		return cachedParent;
+	}
+
+	private void deleteSymlinkParent(FS fs, String gitPath, File workingTree)
+			throws IOException {
+		if (!fs.supportsSymlinks()) {
+			return;
+		}
+		String[] parts = gitPath.split("/"); //$NON-NLS-1$
+		int n = parts.length;
+		CacheItem cached = getRoot();
+		File p = workingTree;
+		for (int i = 0; i < n; i++) {
+			p = new File(p, parts[i]);
+			CacheItem cachedChild = cached != null ? cached.child(parts[i])
+					: null;
+			boolean delete = false;
+			if (cachedChild != null) {
+				if (FileMode.SYMLINK.equals(cachedChild.getMode())) {
+					delete = true;
+				}
+			} else {
+				try {
+					Path nioPath = FileUtils.toPath(p);
+					BasicFileAttributes attributes = nioPath.getFileSystem()
+							.provider()
+							.getFileAttributeView(nioPath,
+									BasicFileAttributeView.class,
+									LinkOption.NOFOLLOW_LINKS)
+							.readAttributes();
+					if (attributes.isSymbolicLink()) {
+						delete = p.isDirectory();
+					} else if (attributes.isRegularFile()) {
+						break;
+					}
+				} catch (InvalidPathException | IOException e) {
+					// If we can't get the attributes the path does not exist,
+					// or if it does a subsequent mkdirs() will also throw an
+					// exception.
+					break;
+				}
+			}
+			if (delete) {
+				// Deletes the symlink
+				FileUtils.delete(p, FileUtils.SKIP_MISSING);
+				if (cached != null) {
+					cached.remove(parts[i]);
+				}
+				break;
+			}
+			cached = cachedChild;
+		}
+	}
+
+	/**
+	 * Records the given {@link FileMode} for the given git path in the cache.
+	 * If an entry already exists for the given path, the previously cached file
+	 * mode is overwritten.
+	 *
+	 * @param gitPath
+	 *            to cache the {@link FileMode} for
+	 * @param finalMode
+	 *            {@link FileMode} to cache
+	 * @return the {@link CacheItem} for the path
+	 */
+	@NonNull
+	private CacheItem add(String gitPath, FileMode finalMode) {
+		if (gitPath.isEmpty()) {
+			throw new IllegalArgumentException();
+		}
+		String[] parts = gitPath.split("/"); //$NON-NLS-1$
+		int n = parts.length;
+		int i = 0;
+		CacheItem curr = getRoot();
+		while (i < n) {
+			CacheItem next = curr.child(parts[i]);
+			if (next == null) {
+				break;
+			}
+			curr = next;
+			i++;
+		}
+		if (i == n) {
+			curr.setMode(finalMode);
+		} else {
+			while (i < n) {
+				curr = curr.insert(parts[i],
+						i + 1 == n ? finalMode : FileMode.TREE);
+				i++;
+			}
+		}
+		return curr;
+	}
+
+	/**
+	 * An item from a {@link FileModeCache}, recording information about a git
+	 * path (known from context).
+	 */
+	public static class CacheItem {
+
+		@NonNull
+		private FileMode mode;
+
+		private Map<String, CacheItem> children;
+
+		/**
+		 * Creates a new {@link CacheItem}.
+		 *
+		 * @param mode
+		 *            {@link FileMode} to cache
+		 */
+		public CacheItem(@NonNull FileMode mode) {
+			this.mode = mode;
+		}
+
+		/**
+		 * Retrieves the cached {@link FileMode}.
+		 *
+		 * @return the {@link FileMode}
+		 */
+		@NonNull
+		public FileMode getMode() {
+			return mode;
+		}
+
+		/**
+		 * Retrieves an immediate child of this {@link CacheItem} by name.
+		 *
+		 * @param childName
+		 *            name of the child to get
+		 * @return the {@link CacheItem}, or {@code null} if no such child is
+		 *         known
+		 */
+		public CacheItem child(String childName) {
+			if (children == null) {
+				return null;
+			}
+			return children.get(childName);
+		}
+
+		/**
+		 * Inserts a new cached {@link FileMode} as an immediate child of this
+		 * {@link CacheItem}. If there is already a child with the same name, it
+		 * is overwritten.
+		 *
+		 * @param childName
+		 *            name of the child to create
+		 * @param childMode
+		 *            {@link FileMode} to cache
+		 * @return the new {@link CacheItem} created for the child
+		 */
+		public CacheItem insert(String childName, @NonNull FileMode childMode) {
+			if (!FileMode.TREE.equals(mode)) {
+				throw new IllegalArgumentException();
+			}
+			if (children == null) {
+				children = new HashMap<>();
+			}
+			CacheItem newItem = new CacheItem(childMode);
+			children.put(childName, newItem);
+			return newItem;
+		}
+
+		/**
+		 * Removes the immediate child with the given name.
+		 *
+		 * @param childName
+		 *            name of the child to remove
+		 * @return the previously cached {@link CacheItem}, if any
+		 */
+		public CacheItem remove(String childName) {
+			if (children == null) {
+				return null;
+			}
+			return children.remove(childName);
+		}
+
+		void setMode(@NonNull FileMode mode) {
+			this.mode = mode;
+			if (!FileMode.TREE.equals(mode)) {
+				children = null;
+			}
+		}
+	}
+
+}