java.io.FileInputStream Maven / Gradle / Ivy
/* * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code 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 * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.io; /** * A
positionFileInputStream
obtains input bytes * from a file in a file system. What files * are available depends on the host environment. * *
FileInputStream
is meant for reading streams of raw bytes * such as image data. For reading streams of characters, consider using *FileReader
. * * @author Arthur van Hoff * @see java.io.File * @see java.io.FileDescriptor * @see java.io.FileOutputStream * @see java.nio.file.Files#newInputStream * @since JDK1.0 */ public class FileInputStream extends InputStream { /* File Descriptor - handle to the open file */ private final FileDescriptor fd; // private FileChannel channel = null; private final Object closeLock = new Object(); private volatile boolean closed = false; private static final ThreadLocalrunningFinalize = new ThreadLocal<>(); private static boolean isRunningFinalize() { Boolean val; if ((val = runningFinalize.get()) != null) return val.booleanValue(); return false; } /** * Creates a FileInputStream
by * opening a connection to an actual file, * the file named by the path namename
* in the file system. A newFileDescriptor
* object is created to represent this file * connection. ** First, if there is a security * manager, its
checkRead
method * is called with thename
argument * as its argument. ** If the named file does not exist, is a directory rather than a regular * file, or for some other reason cannot be opened for reading then a *
FileNotFoundException
is thrown. * * @param name the system-dependent file name. * @exception FileNotFoundException if the file does not exist, * is a directory rather than a regular file, * or for some other reason cannot be opened for * reading. * @exception SecurityException if a security manager exists and its *checkRead
method denies read access * to the file. * @see java.lang.SecurityManager#checkRead(java.lang.String) */ public FileInputStream(String name) throws FileNotFoundException { this(name != null ? new File(name) : null); } /** * Creates aFileInputStream
by * opening a connection to an actual file, * the file named by theFile
* objectfile
in the file system. * A newFileDescriptor
object * is created to represent this file connection. ** First, if there is a security manager, * its
checkRead
method is called * with the path represented by thefile
* argument as its argument. ** If the named file does not exist, is a directory rather than a regular * file, or for some other reason cannot be opened for reading then a *
FileNotFoundException
is thrown. * * @param file the file to be opened for reading. * @exception FileNotFoundException if the file does not exist, * is a directory rather than a regular file, * or for some other reason cannot be opened for * reading. * @exception SecurityException if a security manager exists and its *checkRead
method denies read access to the file. * @see java.io.File#getPath() * @see java.lang.SecurityManager#checkRead(java.lang.String) */ public FileInputStream(File file) throws FileNotFoundException { throw new SecurityException(); } /** * Creates aFileInputStream
by using the file descriptor *fdObj
, which represents an existing connection to an * actual file in the file system. ** If there is a security manager, its
checkRead
method is * called with the file descriptorfdObj
as its argument to * see if it's ok to read the file descriptor. If read access is denied * to the file descriptor aSecurityException
is thrown. ** If
fdObj
is null then aNullPointerException
* is thrown. ** This constructor does not throw an exception if
fdObj
* is {@link java.io.FileDescriptor#valid() invalid}. * However, if the methods are invoked on the resulting stream to attempt * I/O on the stream, anIOException
is thrown. * * @param fdObj the file descriptor to be opened for reading. * @throws SecurityException if a security manager exists and its *checkRead
method denies read access to the * file descriptor. * @see SecurityManager#checkRead(java.io.FileDescriptor) */ public FileInputStream(FileDescriptor fdObj) { throw new SecurityException(); } /** * Opens the specified file for reading. * @param name the name of the file */ private native void open(String name) throws FileNotFoundException; /** * Reads a byte of data from this input stream. This method blocks * if no input is yet available. * * @return the next byte of data, or-1
if the end of the * file is reached. * @exception IOException if an I/O error occurs. */ public native int read() throws IOException; /** * Reads a subarray as a sequence of bytes. * @param b the data to be written * @param off the start offset in the data * @param len the number of bytes that are written * @exception IOException If an I/O error has occurred. */ private native int readBytes(byte b[], int off, int len) throws IOException; /** * Reads up tob.length
bytes of data from this input * stream into an array of bytes. This method blocks until some input * is available. * * @param b the buffer into which the data is read. * @return the total number of bytes read into the buffer, or *-1
if there is no more data because the end of * the file has been reached. * @exception IOException if an I/O error occurs. */ public int read(byte b[]) throws IOException { return readBytes(b, 0, b.length); } /** * Reads up tolen
bytes of data from this input stream * into an array of bytes. Iflen
is not zero, the method * blocks until some input is available; otherwise, no * bytes are read and0
is returned. * * @param b the buffer into which the data is read. * @param off the start offset in the destination arrayb
* @param len the maximum number of bytes read. * @return the total number of bytes read into the buffer, or *-1
if there is no more data because the end of * the file has been reached. * @exception NullPointerException Ifb
isnull
. * @exception IndexOutOfBoundsException Ifoff
is negative, *len
is negative, orlen
is greater than *b.length - off
* @exception IOException if an I/O error occurs. */ public int read(byte b[], int off, int len) throws IOException { return readBytes(b, off, len); } /** * Skips over and discardsn
bytes of data from the * input stream. * *The
skip
method may, for a variety of * reasons, end up skipping over some smaller number of bytes, * possibly0
. Ifn
is negative, an *IOException
is thrown, even though theskip
* method of the {@link InputStream} superclass does nothing in this case. * The actual number of bytes skipped is returned. * *This method may skip more bytes than are remaining in the backing * file. This produces no exception and the number of bytes skipped * may include some number of bytes that were beyond the EOF of the * backing file. Attempting to read from the stream after skipping past * the end will result in -1 indicating the end of the file. * * @param n the number of bytes to be skipped. * @return the actual number of bytes skipped. * @exception IOException if n is negative, if the stream does not * support seek, or if an I/O error occurs. */ public native long skip(long n) throws IOException; /** * Returns an estimate of the number of remaining bytes that can be read (or * skipped over) from this input stream without blocking by the next * invocation of a method for this input stream. The next invocation might be * the same thread or another thread. A single read or skip of this * many bytes will not block, but may read or skip fewer bytes. * *
In some cases, a non-blocking read (or skip) may appear to be * blocked when it is merely slow, for example when reading large * files over slow networks. * * @return an estimate of the number of remaining bytes that can be read * (or skipped over) from this input stream without blocking. * @exception IOException if this file input stream has been closed by calling * {@code close} or an I/O error occurs. */ public native int available() throws IOException; /** * Closes this file input stream and releases any system resources * associated with the stream. * *
If this stream has an associated channel then the channel is closed * as well. * * @exception IOException if an I/O error occurs. * * @revised 1.4 * @spec JSR-51 */ public void close() throws IOException { synchronized (closeLock) { if (closed) { return; } closed = true; } // if (channel != null) { // /* // * Decrement the FD use count associated with the channel // * The use count is incremented whenever a new channel // * is obtained from this stream. // */ // fd.decrementAndGetUseCount(); // channel.close(); // } /* * Decrement the FD use count associated with this stream */ int useCount = fd.decrementAndGetUseCount(); /* * If FileDescriptor is still in use by another stream, the finalizer * will not close it. */ if ((useCount <= 0) || !isRunningFinalize()) { close0(); } } /** * Returns the
FileDescriptor
* object that represents the connection to * the actual file in the file system being * used by thisFileInputStream
. * * @return the file descriptor object associated with this stream. * @exception IOException if an I/O error occurs. * @see java.io.FileDescriptor */ public final FileDescriptor getFD() throws IOException { if (fd != null) return fd; throw new IOException(); } /** * Returns the unique {@link java.nio.channels.FileChannel FileChannel} * object associated with this file input stream. * *The initial {@link java.nio.channels.FileChannel#position() *
} of the returned channel will be equal to the * number of bytes read from the file so far. Reading bytes from this * stream will increment the channel's position. Changing the channel's * position, either explicitly or by reading, will change this stream's * file position. * * @return the file channel associated with this file input stream * * @since 1.4 * @spec JSR-51 */ // public FileChannel getChannel() { // synchronized (this) { // if (channel == null) { // channel = FileChannelImpl.open(fd, true, false, this); // // /* // * Increment fd's use count. Invoking the channel's close() // * method will result in decrementing the use count set for // * the channel. // */ // fd.incrementAndGetUseCount(); // } // return channel; // } // } private static native void initIDs(); private native void close0() throws IOException; static { initIDs(); } /** * Ensures that the
close
method of this file input stream is * called when there are no more references to it. * * @exception IOException if an I/O error occurs. * @see java.io.FileInputStream#close() */ protected void finalize() throws IOException { if ((fd != null) && (fd != FileDescriptor.in)) { /* * Finalizer should not release the FileDescriptor if another * stream is still using it. If the user directly invokes * close() then the FileDescriptor is also released. */ runningFinalize.set(Boolean.TRUE); try { close(); } finally { runningFinalize.set(Boolean.FALSE); } } } }