author | chegar |
Sun, 17 Aug 2014 15:54:13 +0100 | |
changeset 25859 | 3317bb8137f4 |
parent 23306 | jdk/src/share/classes/javax/imageio/stream/MemoryCache.java@679ac7841e8d |
child 26755 | 70eafa5df34b |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 2000, 2003, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package javax.imageio.stream; |
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import java.util.ArrayList; |
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import java.io.InputStream; |
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import java.io.OutputStream; |
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import java.io.IOException; |
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/** |
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* Package-visible class consolidating common code for |
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* <code>MemoryCacheImageInputStream</code> and |
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* <code>MemoryCacheImageOutputStream</code>. |
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* This class keeps an <code>ArrayList</code> of 8K blocks, |
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* loaded sequentially. Blocks may only be disposed of |
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* from the index 0 forward. As blocks are freed, the |
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* corresponding entries in the array list are set to |
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* <code>null</code>, but no compacting is performed. |
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* This allows the index for each block to never change, |
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* and the length of the cache is always the same as the |
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* total amount of data ever cached. Cached data is |
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* therefore always contiguous from the point of last |
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* disposal to the current length. |
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* |
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* <p> The total number of blocks resident in the cache must not |
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* exceed <code>Integer.MAX_VALUE</code>. In practice, the limit of |
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* available memory will be exceeded long before this becomes an |
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* issue, since a full cache would contain 8192*2^31 = 16 terabytes of |
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* data. |
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* |
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* A <code>MemoryCache</code> may be reused after a call |
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* to <code>reset()</code>. |
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*/ |
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class MemoryCache { |
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private static final int BUFFER_LENGTH = 8192; |
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private ArrayList<byte[]> cache = new ArrayList<>(); |
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private long cacheStart = 0L; |
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/** |
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* The largest position ever written to the cache. |
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*/ |
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private long length = 0L; |
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private byte[] getCacheBlock(long blockNum) throws IOException { |
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long blockOffset = blockNum - cacheStart; |
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if (blockOffset > Integer.MAX_VALUE) { |
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// This can only happen when the cache hits 16 terabytes of |
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// contiguous data... |
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throw new IOException("Cache addressing limit exceeded!"); |
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} |
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8034998: Fix raw and unchecked lint warnings in javax.imageio
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return cache.get((int)blockOffset); |
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} |
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/** |
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* Ensures that at least <code>pos</code> bytes are cached, |
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* or the end of the source is reached. The return value |
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* is equal to the smaller of <code>pos</code> and the |
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* length of the source. |
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*/ |
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public long loadFromStream(InputStream stream, long pos) |
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throws IOException { |
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// We've already got enough data cached |
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if (pos < length) { |
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return pos; |
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} |
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int offset = (int)(length % BUFFER_LENGTH); |
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byte [] buf = null; |
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long len = pos - length; |
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if (offset != 0) { |
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buf = getCacheBlock(length/BUFFER_LENGTH); |
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} |
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while (len > 0) { |
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if (buf == null) { |
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try { |
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buf = new byte[BUFFER_LENGTH]; |
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} catch (OutOfMemoryError e) { |
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throw new IOException("No memory left for cache!"); |
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} |
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offset = 0; |
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} |
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int left = BUFFER_LENGTH - offset; |
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int nbytes = (int)Math.min(len, (long)left); |
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nbytes = stream.read(buf, offset, nbytes); |
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if (nbytes == -1) { |
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return length; // EOF |
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} |
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if (offset == 0) { |
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cache.add(buf); |
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} |
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len -= nbytes; |
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length += nbytes; |
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offset += nbytes; |
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if (offset >= BUFFER_LENGTH) { |
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// we've filled the current buffer, so a new one will be |
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// allocated next time around (and offset will be reset to 0) |
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buf = null; |
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} |
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} |
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return pos; |
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} |
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/** |
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* Writes out a portion of the cache to an <code>OutputStream</code>. |
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* This method preserves no state about the output stream, and does |
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* not dispose of any blocks containing bytes written. To dispose |
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* blocks, use {@link #disposeBefore <code>disposeBefore()</code>}. |
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* |
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* @exception IndexOutOfBoundsException if any portion of |
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* the requested data is not in the cache (including if <code>pos</code> |
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* is in a block already disposed), or if either <code>pos</code> or |
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* <code>len</code> is < 0. |
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*/ |
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public void writeToStream(OutputStream stream, long pos, long len) |
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throws IOException { |
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if (pos + len > length) { |
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throw new IndexOutOfBoundsException("Argument out of cache"); |
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} |
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if ((pos < 0) || (len < 0)) { |
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throw new IndexOutOfBoundsException("Negative pos or len"); |
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} |
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if (len == 0) { |
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return; |
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} |
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long bufIndex = pos/BUFFER_LENGTH; |
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if (bufIndex < cacheStart) { |
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throw new IndexOutOfBoundsException("pos already disposed"); |
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} |
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int offset = (int)(pos % BUFFER_LENGTH); |
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byte[] buf = getCacheBlock(bufIndex++); |
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while (len > 0) { |
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if (buf == null) { |
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buf = getCacheBlock(bufIndex++); |
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offset = 0; |
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} |
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int nbytes = (int)Math.min(len, (long)(BUFFER_LENGTH - offset)); |
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stream.write(buf, offset, nbytes); |
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buf = null; |
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len -= nbytes; |
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} |
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} |
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/** |
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* Ensure that there is space to write a byte at the given position. |
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*/ |
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private void pad(long pos) throws IOException { |
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long currIndex = cacheStart + cache.size() - 1; |
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long lastIndex = pos/BUFFER_LENGTH; |
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long numNewBuffers = lastIndex - currIndex; |
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for (long i = 0; i < numNewBuffers; i++) { |
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try { |
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cache.add(new byte[BUFFER_LENGTH]); |
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} catch (OutOfMemoryError e) { |
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throw new IOException("No memory left for cache!"); |
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} |
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} |
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} |
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/** |
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* Overwrites and/or appends the cache from a byte array. |
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* The length of the cache will be extended as needed to hold |
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* the incoming data. |
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* |
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* @param b an array of bytes containing data to be written. |
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* @param off the starting offset withing the data array. |
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* @param len the number of bytes to be written. |
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* @param pos the cache position at which to begin writing. |
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* |
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* @exception NullPointerException if <code>b</code> is <code>null</code>. |
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* @exception IndexOutOfBoundsException if <code>off</code>, |
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* <code>len</code>, or <code>pos</code> are negative, |
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* or if <code>off+len > b.length</code>. |
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*/ |
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public void write(byte[] b, int off, int len, long pos) |
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throws IOException { |
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if (b == null) { |
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throw new NullPointerException("b == null!"); |
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} |
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// Fix 4430357 - if off + len < 0, overflow occurred |
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if ((off < 0) || (len < 0) || (pos < 0) || |
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(off + len > b.length) || (off + len < 0)) { |
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throw new IndexOutOfBoundsException(); |
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} |
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// Ensure there is space for the incoming data |
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long lastPos = pos + len - 1; |
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if (lastPos >= length) { |
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pad(lastPos); |
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length = lastPos + 1; |
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} |
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// Copy the data into the cache, block by block |
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int offset = (int)(pos % BUFFER_LENGTH); |
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while (len > 0) { |
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byte[] buf = getCacheBlock(pos/BUFFER_LENGTH); |
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int nbytes = Math.min(len, BUFFER_LENGTH - offset); |
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System.arraycopy(b, off, buf, offset, nbytes); |
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pos += nbytes; |
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off += nbytes; |
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len -= nbytes; |
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offset = 0; // Always after the first time |
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} |
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} |
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/** |
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* Overwrites or appends a single byte to the cache. |
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* The length of the cache will be extended as needed to hold |
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* the incoming data. |
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* |
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* @param b an <code>int</code> whose 8 least significant bits |
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* will be written. |
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* @param pos the cache position at which to begin writing. |
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* |
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* @exception IndexOutOfBoundsException if <code>pos</code> is negative. |
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*/ |
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public void write(int b, long pos) throws IOException { |
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if (pos < 0) { |
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throw new ArrayIndexOutOfBoundsException("pos < 0"); |
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} |
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// Ensure there is space for the incoming data |
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if (pos >= length) { |
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pad(pos); |
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length = pos + 1; |
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} |
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// Insert the data. |
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byte[] buf = getCacheBlock(pos/BUFFER_LENGTH); |
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int offset = (int)(pos % BUFFER_LENGTH); |
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buf[offset] = (byte)b; |
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} |
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/** |
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* Returns the total length of data that has been cached, |
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* regardless of whether any early blocks have been disposed. |
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* This value will only ever increase. |
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*/ |
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public long getLength() { |
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return length; |
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} |
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/** |
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* Returns the single byte at the given position, as an |
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* <code>int</code>. Returns -1 if this position has |
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* not been cached or has been disposed. |
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*/ |
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public int read(long pos) throws IOException { |
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if (pos >= length) { |
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return -1; |
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} |
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byte[] buf = getCacheBlock(pos/BUFFER_LENGTH); |
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if (buf == null) { |
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return -1; |
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} |
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return buf[(int)(pos % BUFFER_LENGTH)] & 0xff; |
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} |
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/** |
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* Copy <code>len</code> bytes from the cache, starting |
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* at cache position <code>pos</code>, into the array |
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* <code>b</code> at offset <code>off</code>. |
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* |
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* @exception NullPointerException if b is <code>null</code> |
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* @exception IndexOutOfBoundsException if <code>off</code>, |
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* <code>len</code> or <code>pos</code> are negative or if |
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* <code>off + len > b.length</code> or if any portion of the |
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* requested data is not in the cache (including if |
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* <code>pos</code> is in a block that has already been disposed). |
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*/ |
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public void read(byte[] b, int off, int len, long pos) |
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throws IOException { |
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if (b == null) { |
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throw new NullPointerException("b == null!"); |
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} |
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// Fix 4430357 - if off + len < 0, overflow occurred |
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if ((off < 0) || (len < 0) || (pos < 0) || |
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(off + len > b.length) || (off + len < 0)) { |
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throw new IndexOutOfBoundsException(); |
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} |
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if (pos + len > length) { |
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throw new IndexOutOfBoundsException(); |
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} |
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long index = pos/BUFFER_LENGTH; |
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int offset = (int)pos % BUFFER_LENGTH; |
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while (len > 0) { |
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int nbytes = Math.min(len, BUFFER_LENGTH - offset); |
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byte[] buf = getCacheBlock(index++); |
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System.arraycopy(buf, offset, b, off, nbytes); |
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len -= nbytes; |
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off += nbytes; |
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offset = 0; // Always after the first time |
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} |
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} |
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/** |
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* Free the blocks up to the position <code>pos</code>. |
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* The byte at <code>pos</code> remains available. |
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* |
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* @exception IndexOutOfBoundsException if <code>pos</code> |
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* is in a block that has already been disposed. |
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*/ |
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public void disposeBefore(long pos) { |
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long index = pos/BUFFER_LENGTH; |
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if (index < cacheStart) { |
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throw new IndexOutOfBoundsException("pos already disposed"); |
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} |
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long numBlocks = Math.min(index - cacheStart, cache.size()); |
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for (long i = 0; i < numBlocks; i++) { |
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cache.remove(0); |
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} |
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this.cacheStart = index; |
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} |
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/** |
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* Erase the entire cache contents and reset the length to 0. |
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* The cache object may subsequently be reused as though it had just |
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* been allocated. |
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*/ |
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public void reset() { |
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cache.clear(); |
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cacheStart = 0; |
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length = 0L; |
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} |
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364 |
} |