File	Doc	Category	Size	Date	Package
FileCacheImageInputStream.java	API Doc	Java SE 6 API	8183	Tue Jun 10 00:26:08 BST 2008	javax.imageio.stream

FileCacheImageInputStream

• java.lang.Object
  • javax.imageio.stream.ImageInputStreamImpl

Fields Summary
private InputStream	stream
private File	cacheFile
private RandomAccessFile	cache
private static final int	BUFFER_LENGTH
private byte[]	buf
private long	length
private boolean	foundEOF
private final Object	disposerReferent The referent to be registered with the Disposer.
private final DisposerRecord	disposerRecord The DisposerRecord that closes the underlying cache.

Constructors Summary

public FileCacheImageInputStream(InputStream stream, File cacheDir) Constructs a FileCacheImageInputStream that will read from a given InputStream. A temporary file is used as a cache. If cacheDiris non-null and is a directory, the file will be created there. If it is null, the system-dependent default temporary-file directory will be used (see the documentation for File.createTempFile for details). param stream an InputStream to read from. param cacheDir a File indicating where the cache file should be created, or null to use the system directory. exception IllegalArgumentException if stream is null. exception IllegalArgumentException if cacheDir is non-null but is not a directory. exception IOException if a cache file cannot be created. if (stream == null) { throw new IllegalArgumentException("stream == null!"); } if ((cacheDir != null) && !(cacheDir.isDirectory())) { throw new IllegalArgumentException("Not a directory!"); } this.stream = stream; this.cacheFile = File.createTempFile("imageio", ".tmp", cacheDir); this.cache = new RandomAccessFile(cacheFile, "rw"); StreamCloser.addToQueue(this); disposerRecord = new StreamDisposerRecord(cacheFile, cache); if (getClass() == FileCacheImageInputStream.class) { disposerReferent = new Object(); Disposer.addRecord(disposerReferent, disposerRecord); } else { disposerReferent = new StreamFinalizer(this); }

Methods Summary
public void	close() Closes this FileCacheImageInputStream, closing and removing the cache file. The source InputStream is not closed. exception IOException if an error occurs. super.close(); disposerRecord.dispose(); // this will close/delete the cache file stream = null; cache = null; cacheFile = null; StreamCloser.removeFromQueue(this);
protected void	finalize() {@inheritDoc} // Empty finalizer: for performance reasons we instead use the // Disposer mechanism for ensuring that the underlying // RandomAccessFile is closed/deleted prior to garbage collection
public boolean	isCached() Returns true since this ImageInputStream caches data in order to allow seeking backwards. return true. see #isCachedMemory see #isCachedFile return true;
public boolean	isCachedFile() Returns true since this ImageInputStream maintains a file cache. return true. see #isCached see #isCachedMemory return true;
public boolean	isCachedMemory() Returns false since this ImageInputStream does not maintain a main memory cache. return false. see #isCached see #isCachedFile return false;
public int	read() checkClosed(); bitOffset = 0; long next = streamPos + 1; long pos = readUntil(next); if (pos >= next) { cache.seek(streamPos++); return cache.read(); } else { return -1; }
public int	read(byte[] b, int off, int len) checkClosed(); if (b == null) { throw new NullPointerException("b == null!"); } // Fix 4430357 - if off + len < 0, overflow occurred 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; } long pos = readUntil(streamPos + len); // len will always fit into an int so this is safe len = (int)Math.min((long)len, pos - streamPos); if (len > 0) { cache.seek(streamPos); cache.readFully(b, off, len); streamPos += len; return len; } else { return -1; }
private long	readUntil(long pos) Ensures that at least pos bytes are cached, or the end of the source is reached. The return value is equal to the smaller of pos and the length of the source file. // We've already got enough data cached if (pos < length) { return pos; } // pos >= length but length isn't getting any bigger, so return it if (foundEOF) { return length; } long len = pos - length; cache.seek(length); while (len > 0) { // Copy a buffer's worth of data from the source to the cache // BUFFER_LENGTH will always fit into an int so this is safe int nbytes = stream.read(buf, 0, (int)Math.min(len, (long)BUFFER_LENGTH)); if (nbytes == -1) { foundEOF = true; return length; } cache.write(buf, 0, nbytes); len -= nbytes; length += nbytes; } return pos;