repo/luan: src/goodjava/io/BufferedInputStream.java comparison

comparison src/goodjava/io/BufferedInputStream.java @ 1478:37e582f2e266

clone BufferedInputStream

author	Franklin Schmidt <fschmidt@gmail.com>
date	Fri, 24 Apr 2020 10:45:53 -0600
parents
children	bd13aaeaf6d4

comparison

equal deleted inserted replaced

-:509736ad42e6
+:37e582f2e266
+/*
+* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
+* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*
+*/
+package goodjava.io;
+import java.io.InputStream;
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
+/**
+* A <code>BufferedInputStream</code> adds
+* functionality to another input stream-namely,
+* the ability to buffer the input and to
+* support the <code>mark</code> and <code>reset</code>
+* methods. When  the <code>BufferedInputStream</code>
+* is created, an internal buffer array is
+* created. As bytes  from the stream are read
+* or skipped, the internal buffer is refilled
+* as necessary  from the contained input stream,
+* many bytes at a time. The <code>mark</code>
+* operation  remembers a point in the input
+* stream and the <code>reset</code> operation
+* causes all the  bytes read since the most
+* recent <code>mark</code> operation to be
+* reread before new bytes are  taken from
+* the contained input stream.
+*
+* @author  Arthur van Hoff
+* @since   JDK1.0
+*/
+public
+class BufferedInputStream extends FilterInputStream {
+private static int DEFAULT_BUFFER_SIZE = 8192;
+/**
+* The maximum size of array to allocate.
+* Some VMs reserve some header words in an array.
+* Attempts to allocate larger arrays may result in
+* OutOfMemoryError: Requested array size exceeds VM limit
+*/
+private static int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
+/**
+* The internal buffer array where the data is stored. When necessary,
+* it may be replaced by another array of
+* a different size.
+*/
+protected volatile byte buf[];
+/**
+* Atomic updater to provide compareAndSet for buf. This is
+* necessary because closes can be asynchronous. We use nullness
+* of buf[] as primary indicator that this stream is closed. (The
+* "in" field is also nulled out on close.)
+*/
+private static final
+AtomicReferenceFieldUpdater<BufferedInputStream, byte[]> bufUpdater =
+AtomicReferenceFieldUpdater.newUpdater
+(BufferedInputStream.class,  byte[].class, "buf");
+/**
+* The index one greater than the index of the last valid byte in
+* the buffer.
+* This value is always
+* in the range <code>0</code> through <code>buf.length</code>;
+* elements <code>buf[0]</code>  through <code>buf[count-1]
+* </code>contain buffered input data obtained
+* from the underlying  input stream.
+*/
+protected int count;
+/**
+* The current position in the buffer. This is the index of the next
+* character to be read from the <code>buf</code> array.
+* <p>
+* This value is always in the range <code>0</code>
+* through <code>count</code>. If it is less
+* than <code>count</code>, then  <code>buf[pos]</code>
+* is the next byte to be supplied as input;
+* if it is equal to <code>count</code>, then
+* the  next <code>read</code> or <code>skip</code>
+* operation will require more bytes to be
+* read from the contained  input stream.
+*
+* @see     java.io.BufferedInputStream#buf
+*/
+protected int pos;
+/**
+* The value of the <code>pos</code> field at the time the last
+* <code>mark</code> method was called.
+* <p>
+* This value is always
+* in the range <code>-1</code> through <code>pos</code>.
+* If there is no marked position in  the input
+* stream, this field is <code>-1</code>. If
+* there is a marked position in the input
+* stream,  then <code>buf[markpos]</code>
+* is the first byte to be supplied as input
+* after a <code>reset</code> operation. If
+* <code>markpos</code> is not <code>-1</code>,
+* then all bytes from positions <code>buf[markpos]</code>
+* through  <code>buf[pos-1]</code> must remain
+* in the buffer array (though they may be
+* moved to  another place in the buffer array,
+* with suitable adjustments to the values
+* of <code>count</code>,  <code>pos</code>,
+* and <code>markpos</code>); they may not
+* be discarded unless and until the difference
+* between <code>pos</code> and <code>markpos</code>
+* exceeds <code>marklimit</code>.
+*
+* @see     java.io.BufferedInputStream#mark(int)
+* @see     java.io.BufferedInputStream#pos
+*/
+protected int markpos = -1;
+/**
+* The maximum read ahead allowed after a call to the
+* <code>mark</code> method before subsequent calls to the
+* <code>reset</code> method fail.
+* Whenever the difference between <code>pos</code>
+* and <code>markpos</code> exceeds <code>marklimit</code>,
+* then the  mark may be dropped by setting
+* <code>markpos</code> to <code>-1</code>.
+*
+* @see     java.io.BufferedInputStream#mark(int)
+* @see     java.io.BufferedInputStream#reset()
+*/
+protected int marklimit;
+/**
+* Check to make sure that underlying input stream has not been
+* nulled out due to close; if not return it;
+*/
+private InputStream getInIfOpen() throws IOException {
+InputStream input = in;
+if (input == null)
+throw new IOException("Stream closed");
+return input;
+}
+/**
+* Check to make sure that buffer has not been nulled out due to
+* close; if not return it;
+*/
+private byte[] getBufIfOpen() throws IOException {
+byte[] buffer = buf;
+if (buffer == null)
+throw new IOException("Stream closed");
+return buffer;
+}
+/**
+* Creates a <code>BufferedInputStream</code>
+* and saves its  argument, the input stream
+* <code>in</code>, for later use. An internal
+* buffer array is created and  stored in <code>buf</code>.
+*
+* @param   in   the underlying input stream.
+*/
+public BufferedInputStream(InputStream in) {
+this(in, DEFAULT_BUFFER_SIZE);
+}
+/**
+* Creates a <code>BufferedInputStream</code>
+* with the specified buffer size,
+* and saves its  argument, the input stream
+* <code>in</code>, for later use.  An internal
+* buffer array of length  <code>size</code>
+* is created and stored in <code>buf</code>.
+*
+* @param   in     the underlying input stream.
+* @param   size   the buffer size.
+* @exception IllegalArgumentException if {@code size <= 0}.
+*/
+public BufferedInputStream(InputStream in, int size) {
+super(in);
+if (size <= 0) {
+throw new IllegalArgumentException("Buffer size <= 0");
+}
+buf = new byte[size];
+}
+/**
+* Fills the buffer with more data, taking into account
+* shuffling and other tricks for dealing with marks.
+* Assumes that it is being called by a synchronized method.
+* This method also assumes that all data has already been read in,
+* hence pos > count.
+*/
+private void fill() throws IOException {
+byte[] buffer = getBufIfOpen();
+if (markpos < 0)
+pos = 0;            /* no mark: throw away the buffer */
+else if (pos >= buffer.length)  /* no room left in buffer */
+if (markpos > 0) {  /* can throw away early part of the buffer */
+int sz = pos - markpos;
+System.arraycopy(buffer, markpos, buffer, 0, sz);
+pos = sz;
+markpos = 0;
+} else if (buffer.length >= marklimit) {
+markpos = -1;   /* buffer got too big, invalidate mark */
+pos = 0;        /* drop buffer contents */
+} else if (buffer.length >= MAX_BUFFER_SIZE) {
+throw new OutOfMemoryError("Required array size too large");
+} else {            /* grow buffer */
+int nsz = (pos <= MAX_BUFFER_SIZE - pos) ?
+pos * 2 : MAX_BUFFER_SIZE;
+if (nsz > marklimit)
+nsz = marklimit;
+byte nbuf[] = new byte[nsz];
+System.arraycopy(buffer, 0, nbuf, 0, pos);
+if (!bufUpdater.compareAndSet(this, buffer, nbuf)) {
+// Can't replace buf if there was an async close.
+// Note: This would need to be changed if fill()
+// is ever made accessible to multiple threads.
+// But for now, the only way CAS can fail is via close.
+// assert buf == null;
+throw new IOException("Stream closed");
+}
+buffer = nbuf;
+}
+count = pos;
+int n = getInIfOpen().read(buffer, pos, buffer.length - pos);
+if (n > 0)
+count = n + pos;
+}
+/**
+* See
+* the general contract of the <code>read</code>
+* method of <code>InputStream</code>.
+*
+* @return     the next byte of data, or <code>-1</code> if the end of the
+*             stream is reached.
+* @exception  IOException  if this input stream has been closed by
+*                          invoking its {@link #close()} method,
+*                          or an I/O error occurs.
+* @see        java.io.FilterInputStream#in
+*/
+public synchronized int read() throws IOException {
+if (pos >= count) {
+fill();
+if (pos >= count)
+return -1;
+}
+return getBufIfOpen()[pos++] & 0xff;
+}
+/**
+* Read characters into a portion of an array, reading from the underlying
+* stream at most once if necessary.
+*/
+private int read1(byte[] b, int off, int len) throws IOException {
+int avail = count - pos;
+if (avail <= 0) {
+/* If the requested length is at least as large as the buffer, and
+if there is no mark/reset activity, do not bother to copy the
+bytes into the local buffer.  In this way buffered streams will
+cascade harmlessly. */
+if (len >= getBufIfOpen().length && markpos < 0) {
+return getInIfOpen().read(b, off, len);
+}
+fill();
+avail = count - pos;
+if (avail <= 0) return -1;
+}
+int cnt = (avail < len) ? avail : len;
+System.arraycopy(getBufIfOpen(), pos, b, off, cnt);
+pos += cnt;
+return cnt;
+}
+/**
+* Reads bytes from this byte-input stream into the specified byte array,
+* starting at the given offset.
+*
+* <p> This method implements the general contract of the corresponding
+* <code>{@link InputStream#read(byte[], int, int) read}</code> method of
+* the <code>{@link InputStream}</code> class.  As an additional
+* convenience, it attempts to read as many bytes as possible by repeatedly
+* invoking the <code>read</code> method of the underlying stream.  This
+* iterated <code>read</code> continues until one of the following
+* conditions becomes true: <ul>
+*
+*   <li> The specified number of bytes have been read,
+*
+*   <li> The <code>read</code> method of the underlying stream returns
+*   <code>-1</code>, indicating end-of-file, or
+*
+*   <li> The <code>available</code> method of the underlying stream
+*   returns zero, indicating that further input requests would block.
+*
+* </ul> If the first <code>read</code> on the underlying stream returns
+* <code>-1</code> to indicate end-of-file then this method returns
+* <code>-1</code>.  Otherwise this method returns the number of bytes
+* actually read.
+*
+* <p> Subclasses of this class are encouraged, but not required, to
+* attempt to read as many bytes as possible in the same fashion.
+*
+* @param      b     destination buffer.
+* @param      off   offset at which to start storing bytes.
+* @param      len   maximum number of bytes to read.
+* @return     the number of bytes read, or <code>-1</code> if the end of
+*             the stream has been reached.
+* @exception  IOException  if this input stream has been closed by
+*                          invoking its {@link #close()} method,
+*                          or an I/O error occurs.
+*/
+public synchronized int read(byte b[], int off, int len)
+throws IOException
+{
+getBufIfOpen(); // Check for closed stream
+if ((off | len | (off + len) | (b.length - (off + len))) < 0) {
+throw new IndexOutOfBoundsException();
+} else if (len == 0) {
+return 0;
+}
+int n = 0;
+for (;;) {
+int nread = read1(b, off + n, len - n);
+if (nread <= 0)
+return (n == 0) ? nread : n;
+n += nread;
+if (n >= len)
+return n;
+// if not closed but no bytes available, return
+InputStream input = in;
+if (input != null && input.available() <= 0)
+return n;
+}
+}
+/**
+* See the general contract of the <code>skip</code>
+* method of <code>InputStream</code>.
+*
+* @exception  IOException  if the stream does not support seek,
+*                          or if this input stream has been closed by
+*                          invoking its {@link #close()} method, or an
+*                          I/O error occurs.
+*/
+public synchronized long skip(long n) throws IOException {
+getBufIfOpen(); // Check for closed stream
+if (n <= 0) {
+return 0;
+}
+long avail = count - pos;
+if (avail <= 0) {
+// If no mark position set then don't keep in buffer
+if (markpos <0)
+return getInIfOpen().skip(n);
+// Fill in buffer to save bytes for reset
+fill();
+avail = count - pos;
+if (avail <= 0)
+return 0;
+}
+long skipped = (avail < n) ? avail : n;
+pos += skipped;
+return skipped;
+}
+/**
+* Returns an estimate of the number of 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.
+* <p>
+* This method returns the sum of the number of bytes remaining to be read in
+* the buffer (<code>count&nbsp;- pos</code>) and the result of calling the
+* {@link java.io.FilterInputStream#in in}.available().
+*
+* @return     an estimate of the number of bytes that can be read (or skipped
+*             over) from this input stream without blocking.
+* @exception  IOException  if this input stream has been closed by
+*                          invoking its {@link #close()} method,
+*                          or an I/O error occurs.
+*/
+public synchronized int available() throws IOException {
+int n = count - pos;
+int avail = getInIfOpen().available();
+return n > (Integer.MAX_VALUE - avail)
+? Integer.MAX_VALUE
+: n + avail;
+}
+/**
+* See the general contract of the <code>mark</code>
+* method of <code>InputStream</code>.
+*
+* @param   readlimit   the maximum limit of bytes that can be read before
+*                      the mark position becomes invalid.
+* @see     java.io.BufferedInputStream#reset()
+*/
+public synchronized void mark(int readlimit) {
+marklimit = readlimit;
+markpos = pos;
+}
+/**
+* See the general contract of the <code>reset</code>
+* method of <code>InputStream</code>.
+* <p>
+* If <code>markpos</code> is <code>-1</code>
+* (no mark has been set or the mark has been
+* invalidated), an <code>IOException</code>
+* is thrown. Otherwise, <code>pos</code> is
+* set equal to <code>markpos</code>.
+*
+* @exception  IOException  if this stream has not been marked or,
+*                  if the mark has been invalidated, or the stream
+*                  has been closed by invoking its {@link #close()}
+*                  method, or an I/O error occurs.
+* @see        java.io.BufferedInputStream#mark(int)
+*/
+public synchronized void reset() throws IOException {
+getBufIfOpen(); // Cause exception if closed
+if (markpos < 0)
+throw new IOException("Resetting to invalid mark");
+pos = markpos;
+}
+/**
+* Tests if this input stream supports the <code>mark</code>
+* and <code>reset</code> methods. The <code>markSupported</code>
+* method of <code>BufferedInputStream</code> returns
+* <code>true</code>.
+*
+* @return  a <code>boolean</code> indicating if this stream type supports
+*          the <code>mark</code> and <code>reset</code> methods.
+* @see     java.io.InputStream#mark(int)
+* @see     java.io.InputStream#reset()
+*/
+public boolean markSupported() {
+return true;
+}
+/**
+* Closes this input stream and releases any system resources
+* associated with the stream.
+* Once the stream has been closed, further read(), available(), reset(),
+* or skip() invocations will throw an IOException.
+* Closing a previously closed stream has no effect.
+*
+* @exception  IOException  if an I/O error occurs.
+*/
+public void close() throws IOException {
+byte[] buffer;
+while ( (buffer = buf) != null) {
+if (bufUpdater.compareAndSet(this, buffer, null)) {
+InputStream input = in;
+in = null;
+if (input != null)
+input.close();
+return;
+}
+// Else retry in case a new buf was CASed in fill()
+}
+}
+}

Mercurial Hosting > luan

comparison src/goodjava/io/BufferedInputStream.java @ 1478:37e582f2e266