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    1   /*
    2    * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package java.io;
   27   
   28   import java.nio.channels.FileChannel;
   29   import sun.nio.ch.FileChannelImpl;
   30   
   31   
   32   /**
   33    * A file output stream is an output stream for writing data to a
   34    * <code>File</code> or to a <code>FileDescriptor</code>. Whether or not
   35    * a file is available or may be created depends upon the underlying
   36    * platform.  Some platforms, in particular, allow a file to be opened
   37    * for writing by only one <tt>FileOutputStream</tt> (or other
   38    * file-writing object) at a time.  In such situations the constructors in
   39    * this class will fail if the file involved is already open.
   40    *
   41    * <p><code>FileOutputStream</code> is meant for writing streams of raw bytes
   42    * such as image data. For writing streams of characters, consider using
   43    * <code>FileWriter</code>.
   44    *
   45    * @author  Arthur van Hoff
   46    * @see     java.io.File
   47    * @see     java.io.FileDescriptor
   48    * @see     java.io.FileInputStream
   49    * @see     java.nio.file.Files#newOutputStream
   50    * @since   JDK1.0
   51    */
   52   public
   53   class FileOutputStream extends OutputStream
   54   {
   55       /**
   56        * The system dependent file descriptor.
   57        */
   58       private final FileDescriptor fd;
   59   
   60       /**
   61        * True if the file is opened for append.
   62        */
   63       private final boolean append;
   64   
   65       /**
   66        * The associated channel, initalized lazily.
   67        */
   68       private FileChannel channel;
   69   
   70       private final Object closeLock = new Object();
   71       private volatile boolean closed = false;
   72       private static final ThreadLocal<Boolean> runningFinalize =
   73           new ThreadLocal<>();
   74   
   75       private static boolean isRunningFinalize() {
   76           Boolean val;
   77           if ((val = runningFinalize.get()) != null)
   78               return val.booleanValue();
   79           return false;
   80       }
   81   
   82       /**
   83        * Creates a file output stream to write to the file with the
   84        * specified name. A new <code>FileDescriptor</code> object is
   85        * created to represent this file connection.
   86        * <p>
   87        * First, if there is a security manager, its <code>checkWrite</code>
   88        * method is called with <code>name</code> as its argument.
   89        * <p>
   90        * If the file exists but is a directory rather than a regular file, does
   91        * not exist but cannot be created, or cannot be opened for any other
   92        * reason then a <code>FileNotFoundException</code> is thrown.
   93        *
   94        * @param      name   the system-dependent filename
   95        * @exception  FileNotFoundException  if the file exists but is a directory
   96        *                   rather than a regular file, does not exist but cannot
   97        *                   be created, or cannot be opened for any other reason
   98        * @exception  SecurityException  if a security manager exists and its
   99        *               <code>checkWrite</code> method denies write access
  100        *               to the file.
  101        * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
  102        */
  103       public FileOutputStream(String name) throws FileNotFoundException {
  104           this(name != null ? new File(name) : null, false);
  105       }
  106   
  107       /**
  108        * Creates a file output stream to write to the file with the specified
  109        * name.  If the second argument is <code>true</code>, then
  110        * bytes will be written to the end of the file rather than the beginning.
  111        * A new <code>FileDescriptor</code> object is created to represent this
  112        * file connection.
  113        * <p>
  114        * First, if there is a security manager, its <code>checkWrite</code>
  115        * method is called with <code>name</code> as its argument.
  116        * <p>
  117        * If the file exists but is a directory rather than a regular file, does
  118        * not exist but cannot be created, or cannot be opened for any other
  119        * reason then a <code>FileNotFoundException</code> is thrown.
  120        *
  121        * @param     name        the system-dependent file name
  122        * @param     append      if <code>true</code>, then bytes will be written
  123        *                   to the end of the file rather than the beginning
  124        * @exception  FileNotFoundException  if the file exists but is a directory
  125        *                   rather than a regular file, does not exist but cannot
  126        *                   be created, or cannot be opened for any other reason.
  127        * @exception  SecurityException  if a security manager exists and its
  128        *               <code>checkWrite</code> method denies write access
  129        *               to the file.
  130        * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
  131        * @since     JDK1.1
  132        */
  133       public FileOutputStream(String name, boolean append)
  134           throws FileNotFoundException
  135       {
  136           this(name != null ? new File(name) : null, append);
  137       }
  138   
  139       /**
  140        * Creates a file output stream to write to the file represented by
  141        * the specified <code>File</code> object. A new
  142        * <code>FileDescriptor</code> object is created to represent this
  143        * file connection.
  144        * <p>
  145        * First, if there is a security manager, its <code>checkWrite</code>
  146        * method is called with the path represented by the <code>file</code>
  147        * argument as its argument.
  148        * <p>
  149        * If the file exists but is a directory rather than a regular file, does
  150        * not exist but cannot be created, or cannot be opened for any other
  151        * reason then a <code>FileNotFoundException</code> is thrown.
  152        *
  153        * @param      file               the file to be opened for writing.
  154        * @exception  FileNotFoundException  if the file exists but is a directory
  155        *                   rather than a regular file, does not exist but cannot
  156        *                   be created, or cannot be opened for any other reason
  157        * @exception  SecurityException  if a security manager exists and its
  158        *               <code>checkWrite</code> method denies write access
  159        *               to the file.
  160        * @see        java.io.File#getPath()
  161        * @see        java.lang.SecurityException
  162        * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
  163        */
  164       public FileOutputStream(File file) throws FileNotFoundException {
  165           this(file, false);
  166       }
  167   
  168       /**
  169        * Creates a file output stream to write to the file represented by
  170        * the specified <code>File</code> object. If the second argument is
  171        * <code>true</code>, then bytes will be written to the end of the file
  172        * rather than the beginning. A new <code>FileDescriptor</code> object is
  173        * created to represent this file connection.
  174        * <p>
  175        * First, if there is a security manager, its <code>checkWrite</code>
  176        * method is called with the path represented by the <code>file</code>
  177        * argument as its argument.
  178        * <p>
  179        * If the file exists but is a directory rather than a regular file, does
  180        * not exist but cannot be created, or cannot be opened for any other
  181        * reason then a <code>FileNotFoundException</code> is thrown.
  182        *
  183        * @param      file               the file to be opened for writing.
  184        * @param     append      if <code>true</code>, then bytes will be written
  185        *                   to the end of the file rather than the beginning
  186        * @exception  FileNotFoundException  if the file exists but is a directory
  187        *                   rather than a regular file, does not exist but cannot
  188        *                   be created, or cannot be opened for any other reason
  189        * @exception  SecurityException  if a security manager exists and its
  190        *               <code>checkWrite</code> method denies write access
  191        *               to the file.
  192        * @see        java.io.File#getPath()
  193        * @see        java.lang.SecurityException
  194        * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
  195        * @since 1.4
  196        */
  197       public FileOutputStream(File file, boolean append)
  198           throws FileNotFoundException
  199       {
  200           String name = (file != null ? file.getPath() : null);
  201           SecurityManager security = System.getSecurityManager();
  202           if (security != null) {
  203               security.checkWrite(name);
  204           }
  205           if (name == null) {
  206               throw new NullPointerException();
  207           }
  208           this.fd = new FileDescriptor();
  209           this.append = append;
  210   
  211           fd.incrementAndGetUseCount();
  212           open(name, append);
  213       }
  214   
  215       /**
  216        * Creates a file output stream to write to the specified file
  217        * descriptor, which represents an existing connection to an actual
  218        * file in the file system.
  219        * <p>
  220        * First, if there is a security manager, its <code>checkWrite</code>
  221        * method is called with the file descriptor <code>fdObj</code>
  222        * argument as its argument.
  223        * <p>
  224        * If <code>fdObj</code> is null then a <code>NullPointerException</code>
  225        * is thrown.
  226        * <p>
  227        * This constructor does not throw an exception if <code>fdObj</code>
  228        * is {@link java.io.FileDescriptor#valid() invalid}.
  229        * However, if the methods are invoked on the resulting stream to attempt
  230        * I/O on the stream, an <code>IOException</code> is thrown.
  231        *
  232        * @param      fdObj   the file descriptor to be opened for writing
  233        * @exception  SecurityException  if a security manager exists and its
  234        *               <code>checkWrite</code> method denies
  235        *               write access to the file descriptor
  236        * @see        java.lang.SecurityManager#checkWrite(java.io.FileDescriptor)
  237        */
  238       public FileOutputStream(FileDescriptor fdObj) {
  239           SecurityManager security = System.getSecurityManager();
  240           if (fdObj == null) {
  241               throw new NullPointerException();
  242           }
  243           if (security != null) {
  244               security.checkWrite(fdObj);
  245           }
  246           this.fd = fdObj;
  247           this.append = false;
  248   
  249           /*
  250            * FileDescriptor is being shared by streams.
  251            * Ensure that it's GC'ed only when all the streams/channels are done
  252            * using it.
  253            */
  254           fd.incrementAndGetUseCount();
  255       }
  256   
  257       /**
  258        * Opens a file, with the specified name, for overwriting or appending.
  259        * @param name name of file to be opened
  260        * @param append whether the file is to be opened in append mode
  261        */
  262       private native void open(String name, boolean append)
  263           throws FileNotFoundException;
  264   
  265       /**
  266        * Writes the specified byte to this file output stream.
  267        *
  268        * @param   b   the byte to be written.
  269        * @param   append   {@code true} if the write operation first
  270        *     advances the position to the end of file
  271        */
  272       private native void write(int b, boolean append) throws IOException;
  273   
  274       /**
  275        * Writes the specified byte to this file output stream. Implements
  276        * the <code>write</code> method of <code>OutputStream</code>.
  277        *
  278        * @param      b   the byte to be written.
  279        * @exception  IOException  if an I/O error occurs.
  280        */
  281       public void write(int b) throws IOException {
  282           write(b, append);
  283       }
  284   
  285       /**
  286        * Writes a sub array as a sequence of bytes.
  287        * @param b the data to be written
  288        * @param off the start offset in the data
  289        * @param len the number of bytes that are written
  290        * @param append {@code true} to first advance the position to the
  291        *     end of file
  292        * @exception IOException If an I/O error has occurred.
  293        */
  294       private native void writeBytes(byte b[], int off, int len, boolean append)
  295           throws IOException;
  296   
  297       /**
  298        * Writes <code>b.length</code> bytes from the specified byte array
  299        * to this file output stream.
  300        *
  301        * @param      b   the data.
  302        * @exception  IOException  if an I/O error occurs.
  303        */
  304       public void write(byte b[]) throws IOException {
  305           writeBytes(b, 0, b.length, append);
  306       }
  307   
  308       /**
  309        * Writes <code>len</code> bytes from the specified byte array
  310        * starting at offset <code>off</code> to this file output stream.
  311        *
  312        * @param      b     the data.
  313        * @param      off   the start offset in the data.
  314        * @param      len   the number of bytes to write.
  315        * @exception  IOException  if an I/O error occurs.
  316        */
  317       public void write(byte b[], int off, int len) throws IOException {
  318           writeBytes(b, off, len, append);
  319       }
  320   
  321       /**
  322        * Closes this file output stream and releases any system resources
  323        * associated with this stream. This file output stream may no longer
  324        * be used for writing bytes.
  325        *
  326        * <p> If this stream has an associated channel then the channel is closed
  327        * as well.
  328        *
  329        * @exception  IOException  if an I/O error occurs.
  330        *
  331        * @revised 1.4
  332        * @spec JSR-51
  333        */
  334       public void close() throws IOException {
  335           synchronized (closeLock) {
  336               if (closed) {
  337                   return;
  338               }
  339               closed = true;
  340           }
  341   
  342           if (channel != null) {
  343               /*
  344                * Decrement FD use count associated with the channel
  345                * The use count is incremented whenever a new channel
  346                * is obtained from this stream.
  347                */
  348               fd.decrementAndGetUseCount();
  349               channel.close();
  350           }
  351   
  352           /*
  353            * Decrement FD use count associated with this stream
  354            */
  355           int useCount = fd.decrementAndGetUseCount();
  356   
  357           /*
  358            * If FileDescriptor is still in use by another stream, the finalizer
  359            * will not close it.
  360            */
  361           if ((useCount <= 0) || !isRunningFinalize()) {
  362               close0();
  363           }
  364       }
  365   
  366       /**
  367        * Returns the file descriptor associated with this stream.
  368        *
  369        * @return  the <code>FileDescriptor</code> object that represents
  370        *          the connection to the file in the file system being used
  371        *          by this <code>FileOutputStream</code> object.
  372        *
  373        * @exception  IOException  if an I/O error occurs.
  374        * @see        java.io.FileDescriptor
  375        */
  376        public final FileDescriptor getFD()  throws IOException {
  377           if (fd != null) return fd;
  378           throw new IOException();
  379        }
  380   
  381       /**
  382        * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
  383        * object associated with this file output stream. </p>
  384        *
  385        * <p> The initial {@link java.nio.channels.FileChannel#position()
  386        * </code>position<code>} of the returned channel will be equal to the
  387        * number of bytes written to the file so far unless this stream is in
  388        * append mode, in which case it will be equal to the size of the file.
  389        * Writing bytes to this stream will increment the channel's position
  390        * accordingly.  Changing the channel's position, either explicitly or by
  391        * writing, will change this stream's file position.
  392        *
  393        * @return  the file channel associated with this file output stream
  394        *
  395        * @since 1.4
  396        * @spec JSR-51
  397        */
  398       public FileChannel getChannel() {
  399           synchronized (this) {
  400               if (channel == null) {
  401                   channel = FileChannelImpl.open(fd, false, true, append, this);
  402   
  403                   /*
  404                    * Increment fd's use count. Invoking the channel's close()
  405                    * method will result in decrementing the use count set for
  406                    * the channel.
  407                    */
  408                   fd.incrementAndGetUseCount();
  409               }
  410               return channel;
  411           }
  412       }
  413   
  414       /**
  415        * Cleans up the connection to the file, and ensures that the
  416        * <code>close</code> method of this file output stream is
  417        * called when there are no more references to this stream.
  418        *
  419        * @exception  IOException  if an I/O error occurs.
  420        * @see        java.io.FileInputStream#close()
  421        */
  422       protected void finalize() throws IOException {
  423           if (fd != null) {
  424               if (fd == FileDescriptor.out || fd == FileDescriptor.err) {
  425                   flush();
  426               } else {
  427   
  428                   /*
  429                    * Finalizer should not release the FileDescriptor if another
  430                    * stream is still using it. If the user directly invokes
  431                    * close() then the FileDescriptor is also released.
  432                    */
  433                   runningFinalize.set(Boolean.TRUE);
  434                   try {
  435                       close();
  436                   } finally {
  437                       runningFinalize.set(Boolean.FALSE);
  438                   }
  439               }
  440           }
  441       }
  442   
  443       private native void close0() throws IOException;
  444   
  445       private static native void initIDs();
  446   
  447       static {
  448           initIDs();
  449       }
  450   
  451   }

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