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/* * @(#)MemoryCacheImageOutputStream.java 1.19 06/01/05 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package javax.imageio.stream; import java.io.IOException; import java.io.OutputStream; /** * An implementation of <code>ImageOutputStream</code> that writes its * output to a regular <code>OutputStream</code>. A memory buffer is * used to cache at least the data between the discard position and * the current write position. The only constructor takes an * <code>OutputStream</code>, so this class may not be used for * read/modify/write operations. Reading can occur only on parts of * the stream that have already been written to the cache and not * yet flushed. * * @version 0.5 */ public class MemoryCacheImageOutputStream extends ImageOutputStreamImpl { private OutputStream stream; private MemoryCache cache = new MemoryCache(); /** * Constructs a <code>MemoryCacheImageOutputStream</code> that will write * to a given <code>OutputStream</code>. * * @param stream an <code>OutputStream</code> to write to. * * @exception IllegalArgumentException if <code>stream</code> is * <code>null</code>. */ public MemoryCacheImageOutputStream(OutputStream stream) { if (stream == null) { throw new IllegalArgumentException("stream == null!"); } this.stream = stream; } public int read() throws IOException { checkClosed(); bitOffset = 0; int val = cache.read(streamPos); if (val != -1) { ++streamPos; } return val; } public int read(byte[] b, int off, int len) throws IOException { checkClosed(); if (b == null) { throw new NullPointerException("b == null!"); } // Fix 4467608: read([B,I,I) works incorrectly if len<=0 if (off < 0 || len < 0 || off + len > b.length || off + len < 0) { throw new IndexOutOfBoundsException ("off < 0 || len < 0 || off+len > b.length || off+len < 0!"); } bitOffset = 0; if (len == 0) { return 0; } // check if we're already at/past EOF i.e. // no more bytes left to read from cache long bytesLeftInCache = cache.getLength() - streamPos; if (bytesLeftInCache <= 0) { return -1; // EOF } // guaranteed by now that bytesLeftInCache > 0 && len > 0 // and so the rest of the error checking is done by cache.read() // NOTE that alot of error checking is duplicated len = (int)Math.min(bytesLeftInCache, (long)len); cache.read(b, off, len, streamPos); streamPos += len; return len; } public void write(int b) throws IOException { flushBits(); // this will call checkClosed() for us cache.write(b, streamPos); ++streamPos; } public void write(byte[] b, int off, int len) throws IOException { flushBits(); // this will call checkClosed() for us cache.write(b, off, len, streamPos); streamPos += len; } public long length() { try { checkClosed(); return cache.getLength(); } catch (IOException e) { return -1L; } } /** * Returns <code>true</code> since this * <code>ImageOutputStream</code> caches data in order to allow * seeking backwards. * * @return <code>true</code>. * * @see #isCachedMemory * @see #isCachedFile */ public boolean isCached() { return true; } /** * Returns <code>false</code> since this * <code>ImageOutputStream</code> does not maintain a file cache. * * @return <code>false</code>. * * @see #isCached * @see #isCachedMemory */ public boolean isCachedFile() { return false; } /** * Returns <code>true</code> since this * <code>ImageOutputStream</code> maintains a main memory cache. * * @return <code>true</code>. * * @see #isCached * @see #isCachedFile */ public boolean isCachedMemory() { return true; } /** * Closes this <code>MemoryCacheImageOutputStream</code>. All * pending data is flushed to the output, and the cache * is released. The destination <code>OutputStream</code> * is not closed. */ public void close() throws IOException { long length = cache.getLength(); seek(length); flushBefore(length); super.close(); cache.reset(); cache = null; stream = null; } public void flushBefore(long pos) throws IOException { long oFlushedPos = flushedPos; super.flushBefore(pos); // this will call checkClosed() for us long flushBytes = flushedPos - oFlushedPos; cache.writeToStream(stream, oFlushedPos, flushBytes); cache.disposeBefore(flushedPos); stream.flush(); } }