| // Copyright 2014 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.actions.cache; |
| |
| /** |
| * An interface to represent the state of a file (or directory). This is used to determine whether a |
| * file has changed or not. |
| * |
| * <p>NB! Several other parts of Blaze are relying on the fact that metadata uses mtime and not |
| * ctime. If metadata is ever changed to use ctime, all uses of Metadata must be carefully examined. |
| */ |
| public interface Metadata { |
| /** |
| * Marker interface for singleton implementations of the Metadata interface. This is only needed |
| * for a correct implementation of {@code equals}. |
| */ |
| public interface Singleton { |
| } |
| |
| /** |
| * Whether the underlying file system object is a file or a symlink to a file, rather than a |
| * directory. All files are guaranteed to have a digest, and {@link #getDigest} must only be |
| * called on files. |
| */ |
| boolean isFile(); |
| |
| /** |
| * Returns the file's digest; must only be called on objects for which {@link #isFile} returns |
| * true. |
| * |
| * <p>The return value is owned by the cache and must not be modified. |
| */ |
| byte[] getDigest(); |
| |
| /** Returns the file's size, or 0 if the underlying file system object is not a file. */ |
| // TODO(ulfjack): Throw an exception if it's not a file. |
| long getSize(); |
| |
| /** |
| * Returns the last modified time; must only be called on objects for which {@link #isFile} |
| * returns false. |
| */ |
| long getModifiedTime(); |
| } |