/hudson-utils/src/main/java/org/hudsonci/utils/io/FileBeheader.java
http://github.com/hudson/hudson · Java · 110 lines · 56 code · 10 blank · 44 comment · 4 complexity · ccb0e267a220b211c7a6fd154a35caa5 MD5 · raw file
- /**
- * The MIT License
- *
- * Copyright (c) 2010-2011 Sonatype, Inc. All rights reserved.
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
- package org.hudsonci.utils.io;
- import java.io.File;
- import java.io.FileInputStream;
- import java.io.FileOutputStream;
- import java.io.IOException;
- import java.nio.channels.FileChannel;
- /**
- * Removes the beginning of a file.
- *
- * @author Jamie Whitehouse
- * @since 2.1.0
- */
- public class FileBeheader
- {
- /**
- * Beware, the original file is modified when chopping; you relinquish
- * all control of the original file.
- *
- * Requires write access to the same directory as the original.
- *
- * @param original the original file
- * @param tailToKeep the number of bytes to keep at the end of the file
- *
- * @return the original file chopped; for convenience
- *
- * @throws IllegalArgumentException if original is a directory
- * @throws IllegalStateException if some error occurs; it's unreasonable to try and recover from this
- */
- public static File chop( final File original, final long tailToKeep )
- {
- if ( !original.isFile() )
- {
- throw new IllegalArgumentException( "Cannot behead directories: " + original );
- }
- File truncatedFile = new File( original.getParentFile(), original.getName() + ".truncated" );
- FileChannel whole = null;
- FileChannel chopped = null;
- try
- {
- whole = new FileInputStream( original ).getChannel();
- chopped = new FileOutputStream( truncatedFile ).getChannel();
- long originalLength = original.length();
- long lengthToKeep = originalLength < tailToKeep ? 0 : originalLength - tailToKeep;
- whole.transferTo( lengthToKeep, originalLength, chopped );
- }
- catch ( IOException e )
- {
- throw new IllegalStateException( "Cannot behead file due to inconsistent internal state.", e );
- }
- finally
- {
- Closer.close( whole, chopped );
- }
- // Replace original with chopped file.
- boolean isRenamed = truncatedFile.renameTo( original );
- if ( !( isRenamed ) )
- {
- IllegalStateException renameException =
- new IllegalStateException( "Cannot replace original with chopped file to: " + original );
- String originalPath = original.getAbsolutePath();
- boolean isDeleted = original.delete();
- if ( isDeleted )
- {
- boolean isRenamedAgain = truncatedFile.renameTo( new File( originalPath ) );
- if ( !isRenamedAgain )
- {
- throw renameException;
- }
- }
- else
- {
- throw renameException;
- }
- }
- return original;
- }
- }