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StreamFilesRecursive.java
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StreamFilesRecursive.java
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/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.io.fs;
import java.io.File;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.NoSuchFileException;
import java.util.List;
import java.util.stream.Stream;
import static java.util.stream.Collectors.toList;
public class StreamFilesRecursive
{
private StreamFilesRecursive()
{
//This is a helper class, do not instantiate it.
}
/**
* Static implementation of {@link FileSystemAbstraction#streamFilesRecursive(File)} that does not require
* any external state, other than what is presented through the given {@link FileSystemAbstraction}.
*
* Return a stream of {@link FileHandle file handles} for every file in the given directory, and its
* sub-directories.
* <p>
* Alternatively, if the {@link File} given as an argument refers to a file instead of a directory, then a stream
* will be returned with a file handle for just that file.
* <p>
* The stream is based on a snapshot of the file tree, so changes made to the tree using the returned file handles
* will not be reflected in the stream.
* <p>
* No directories will be returned. Only files. If a file handle ends up leaving a directory empty through a
* rename or a delete, then the empty directory will automatically be deleted as well.
* Likewise, if a file is moved to a path where not all of the directories in the path exists, then those missing
* directories will be created prior to the file rename.
*
* @param directory The base directory to start streaming files from, or the specific individual file to stream.
* @param fs The {@link FileSystemAbstraction} to use for manipulating files.
* @return A {@link Stream} of {@link FileHandle}s
* @throws NoSuchFileException If the given base directory or file does not exists.
* @throws IOException If an I/O error occurs, possibly with the canonicalisation of the paths.
*/
public static Stream<FileHandle> streamFilesRecursive( File directory, FileSystemAbstraction fs ) throws IOException
{
try
{
// We grab a snapshot of the file tree to avoid seeing the same file twice or more due to renames.
List<File> snapshot = streamFilesRecursiveInner( directory.getCanonicalFile(), fs ).collect( toList() );
return snapshot.stream().map( f -> new WrappingFileHandle( f, directory, fs ) );
}
catch ( UncheckedIOException e )
{
// We sneak checked IOExceptions through UncheckedIOExceptions due to our use of streams and lambdas.
throw e.getCause();
}
}
private static Stream<File> streamFilesRecursiveInner( File directory, FileSystemAbstraction fs )
{
File[] files = fs.listFiles( directory );
if ( files == null )
{
if ( !fs.fileExists( directory ) )
{
throw new UncheckedIOException( new NoSuchFileException( directory.getPath() ) );
}
return Stream.of( directory );
}
else
{
return Stream.of( files )
.flatMap( f -> fs.isDirectory( f ) ? streamFilesRecursiveInner( f, fs ) : Stream.of( f ) );
}
}
}