- /*
- * @(#)MemoryCache.java 1.13 03/01/23
- *
- * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- */
-
- package javax.imageio.stream;
-
- import java.util.ArrayList;
- import java.io.InputStream;
- import java.io.OutputStream;
- import java.io.IOException;
-
- /**
- * Package-visible class consolidating common code for
- * <code>MemoryCacheImageInputStream</code> and
- * <code>MemoryCacheImageOutputStream</code>.
- * This class keeps an <code>ArrayList</code> of 8K blocks,
- * loaded sequentially. Blocks may only be disposed of
- * from the index 0 forward. As blocks are freed, the
- * corresponding entries in the array list are set to
- * <code>null</code>, but no compacting is performed.
- * This allows the index for each block to never change,
- * and the length of the cache is always the same as the
- * total amount of data ever cached. Cached data is
- * therefore always contiguous from the point of last
- * disposal to the current length.
- *
- * <p> The total number of blocks resident in the cache must not
- * exceed <code>Integer.MAX_VALUE</code>. In practice, the limit of
- * available memory will be exceeded long before this becomes an
- * issue, since a full cache would contain 8192*2^31 = 16 terabytes of
- * data.
- *
- * A <code>MemoryCache</code> may be reused after a call
- * to <code>reset()</code>.
- */
- class MemoryCache {
-
- private static final int BUFFER_LENGTH = 8192;
-
- private ArrayList cache = new ArrayList();
-
- private long cacheStart = 0L;
-
- /**
- * The largest position ever written to the cache.
- */
- private long length = 0L;
-
- private byte[] getCacheBlock(long blockNum) throws IOException {
- long blockOffset = blockNum - cacheStart;
- if (blockOffset > Integer.MAX_VALUE) {
- // This can only happen when the cache hits 16 terabytes of
- // contiguous data...
- throw new IOException("Cache addressing limit exceeded!");
- }
- return (byte[])cache.get((int)blockOffset);
- }
-
- /**
- * Ensures that at least <code>pos</code> bytes are cached,
- * or the end of the source is reached. The return value
- * is equal to the smaller of <code>pos</code> and the
- * length of the source.
- */
- public long loadFromStream(InputStream stream, long pos)
- throws IOException {
- // We've already got enough data cached
- if (pos < length) {
- return pos;
- }
-
- int offset = (int)(length % BUFFER_LENGTH);
- byte [] buf = null;
-
- long len = pos - length;
- if (offset != 0) {
- buf = getCacheBlock(lengthBUFFER_LENGTH);
- }
-
- while (len > 0) {
- if (buf == null) {
- try {
- buf = new byte[BUFFER_LENGTH];
- } catch (OutOfMemoryError e) {
- throw new IOException("No memory left for cache!");
- }
- offset = 0;
- }
-
- int left = BUFFER_LENGTH - offset;
- int nbytes = (int)Math.min(len, (long)left);
- nbytes = stream.read(buf, offset, nbytes);
- if (nbytes == -1) {
- return length; // EOF
- }
-
- if (offset == 0) {
- cache.add(buf);
- }
- buf = null;
-
- len -= nbytes;
- length += nbytes;
- }
-
- return pos;
- }
-
- /**
- * Writes out a portion of the cache to an <code>OutputStream</code>.
- * This method preserves no state about the output stream, and does
- * not dispose of any blocks containing bytes written. To dispose
- * blocks, use {@link #disposeBefore <code>disposeBefore()</code>}.
- *
- * @exception IndexOutOfBoundsException if any portion of
- * the requested data is not in the cache (including if <code>pos</code>
- * is in a block already disposed), or if either <code>pos</code> or
- * <code>len</code> is < 0.
- */
- public void writeToStream(OutputStream stream, long pos, long len)
- throws IOException {
- if (pos + len > length) {
- throw new IndexOutOfBoundsException("Argument out of cache");
- }
- if ((pos < 0) || (len < 0)) {
- throw new IndexOutOfBoundsException("Negative pos or len");
- }
- if (len == 0) {
- return;
- }
-
- long bufIndex = posBUFFER_LENGTH;
- if (bufIndex < cacheStart) {
- throw new IndexOutOfBoundsException("pos already disposed");
- }
- int offset = (int)(pos % BUFFER_LENGTH);
-
- byte[] buf = getCacheBlock(bufIndex++);
- while (len > 0) {
- if (buf == null) {
- buf = getCacheBlock(bufIndex++);
- offset = 0;
- }
- int nbytes = (int)Math.min(len, (long)(BUFFER_LENGTH - offset));
- stream.write(buf, offset, nbytes);
- buf = null;
- len -= nbytes;
- }
- }
-
- /**
- * Ensure that there is space to write a byte at the given position.
- */
- private void pad(long pos) throws IOException {
- long currIndex = cacheStart + cache.size() - 1;
- long lastIndex = posBUFFER_LENGTH;
- long numNewBuffers = lastIndex - currIndex;
- for (long i = 0; i < numNewBuffers; i++) {
- try {
- cache.add(new byte[BUFFER_LENGTH]);
- } catch (OutOfMemoryError e) {
- throw new IOException("No memory left for cache!");
- }
- }
- }
-
- /**
- * Overwrites and/or appends the cache from a byte array.
- * The length of the cache will be extended as needed to hold
- * the incoming data.
- *
- * @param b an array of bytes containing data to be written.
- * @param off the starting offset withing the data array.
- * @param len the number of bytes to be written.
- * @param pos the cache position at which to begin writing.
- *
- * @exception NullPointerException if <code>b</code> is <code>null</code>.
- * @exception IndexOutOfBoundsException if <code>off</code>,
- * <code>len</code>, or <code>pos</code> are negative,
- * or if <code>off+len > b.length</code>.
- */
- public void write(byte[] b, int off, int len, long pos)
- throws IOException {
- if (b == null) {
- throw new NullPointerException("b == null!");
- }
- // Fix 4430357 - if off + len < 0, overflow occurred
- if ((off < 0) || (len < 0) || (pos < 0) ||
- (off + len > b.length) || (off + len < 0)) {
- throw new IndexOutOfBoundsException();
- }
-
- // Ensure there is space for the incoming data
- long lastPos = pos + len - 1;
- if (lastPos >= length) {
- pad(lastPos);
- length = lastPos + 1;
- }
-
- // Copy the data into the cache, block by block
- int offset = (int)(pos % BUFFER_LENGTH);
- while (len > 0) {
- byte[] buf = getCacheBlock(posBUFFER_LENGTH);
- int nbytes = Math.min(len, BUFFER_LENGTH - offset);
- System.arraycopy(b, off, buf, offset, nbytes);
-
- pos += nbytes;
- off += nbytes;
- len -= nbytes;
- offset = 0; // Always after the first time
- }
- }
-
- /**
- * Overwrites or appends a single byte to the cache.
- * The length of the cache will be extended as needed to hold
- * the incoming data.
- *
- * @param b an <code>int</code> whose 8 least significant bits
- * will be written.
- * @param pos the cache position at which to begin writing.
- *
- * @exception IndexOutOfBoundsException if <code>pos</code> is negative.
- */
- public void write(int b, long pos) throws IOException {
- if (pos < 0) {
- throw new ArrayIndexOutOfBoundsException("pos < 0");
- }
-
- // Ensure there is space for the incoming data
- if (pos >= length) {
- pad(pos);
- length = pos + 1;
- }
-
- // Insert the data.
- byte[] buf = getCacheBlock(posBUFFER_LENGTH);
- int offset = (int)(pos % BUFFER_LENGTH);
- buf[offset] = (byte)b;
- }
-
- /**
- * Returns the total length of data that has been cached,
- * regardless of whether any early blocks have been disposed.
- * This value will only ever increase.
- */
- public long getLength() {
- return length;
- }
-
- /**
- * Returns the single byte at the given position, as an
- * <code>int</code>. Returns -1 if this position has
- * not been cached or has been disposed.
- */
- public int read(long pos) throws IOException {
- if (pos >= length) {
- return -1;
- }
-
- byte[] buf = getCacheBlock(posBUFFER_LENGTH);
- if (buf == null) {
- return -1;
- }
-
- return buf[(int)(pos % BUFFER_LENGTH)] & 0xff;
- }
-
- /**
- * Copy <code>len</code> bytes from the cache, starting
- * at cache position <code>pos</code>, into the array
- * <code>b</code> at offset <code>off</code>.
- *
- * @exception NullPointerException if b is <code>null</code>
- * @exception IndexOutOfBoundsException if <code>off</code>,
- * <code>len</code> or <code>pos</code> are negative or if
- * <code>off + len > b.length</code> or if any portion of the
- * requested data is not in the cache (including if
- * <code>pos</code> is in a block that has already been disposed).
- */
- public void read(byte[] b, int off, int len, long pos)
- throws IOException {
- if (b == null) {
- throw new NullPointerException("b == null!");
- }
- // Fix 4430357 - if off + len < 0, overflow occurred
- if ((off < 0) || (len < 0) || (pos < 0) ||
- (off + len > b.length) || (off + len < 0)) {
- throw new IndexOutOfBoundsException();
- }
- if (pos + len > length) {
- throw new IndexOutOfBoundsException();
- }
-
- long index = posBUFFER_LENGTH;
- int offset = (int)pos % BUFFER_LENGTH;
- while (len > 0) {
- int nbytes = Math.min(len, BUFFER_LENGTH - offset);
- byte[] buf = getCacheBlock(index++);
- System.arraycopy(buf, offset, b, off, nbytes);
-
- len -= nbytes;
- off += nbytes;
- offset = 0; // Always after the first time
- }
- }
-
- /**
- * Free the blocks up to the position <code>pos</code>.
- * The byte at <code>pos</code> remains available.
- *
- * @exception IndexOutOfBoundsException if <code>pos</code>
- * is in a block that has already been disposed.
- */
- public void disposeBefore(long pos) {
- long index = posBUFFER_LENGTH;
- if (index < cacheStart) {
- throw new IndexOutOfBoundsException("pos already disposed");
- }
- long numBlocks = Math.min(index - cacheStart, cache.size());
- for (long i = 0; i < numBlocks; i++) {
- cache.remove(0);
- }
- this.cacheStart = index;
- }
-
- /**
- * Erase the entire cache contents and reset the length to 0.
- * The cache object may subsequently be reused as though it had just
- * been allocated.
- */
- public void reset() {
- cache.clear();
- cacheStart = 0;
- length = 0L;
- }
- }