/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id: FileCacheSeekableStream.java 447277 2006-09-18 06:19:34Z jeremias $ */
package info.guardianproject.iocipher.player;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import android.content.Context;
/**
* A subclass of <code>SeekableStream</code> that may be used to wrap
* a regular <code>InputStream</code>. Seeking backwards is supported
* by means of a file cache. In circumstances that do not allow the
* creation of a temporary file (for example, due to security
* consideration or the absence of local disk), the
* <code>MemoryCacheSeekableStream</code> class may be used instead.
*
* <p> The <code>mark()</code> and <code>reset()</code> methods are
* supported.
*
* <p><b> This class is not a committed part of the JAI API. It may
* be removed or changed in future releases of JAI.</b>
*/
public final class FileCacheSeekableStream extends SeekableStream {
/** The source stream. */
private InputStream stream;
/** The cache File. */
private File cacheFile;
/** The cache as a RandomAcessFile. */
private RandomAccessFile cache;
/** The length of the read buffer. */
private int bufLen = 1024;
/** The read buffer. */
private byte[] buf = new byte[bufLen];
/** Number of bytes in the cache. */
private long length = 0;
/** Next byte to be read. */
private long pointer = 0;
/** True if we've encountered the end of the source stream. */
private boolean foundEOF = false;
public FileCacheSeekableStream(InputStream stream) throws IOException {
this(stream, null);
}
/**
* Constructs a <code>MemoryCacheSeekableStream</code> that takes
* its source data from a regular <code>InputStream</code>.
* Seeking backwards is supported by means of an file cache.
*
* <p> An <code>IOException</code> will be thrown if the
* attempt to create the cache file fails for any reason.
*/
public FileCacheSeekableStream(InputStream stream, File cacheDir) throws IOException {
this.stream = stream;
this.cacheFile = File.createTempFile("cta-cache", ".tmp", cacheDir);
cacheFile.deleteOnExit();
this.cache = new RandomAccessFile(cacheFile, "rw");
}
/**
* 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 file.
*/
private long readUntil(long pos) throws IOException {
// 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
// bufLen will always fit into an int so this is safe
int nbytes = stream.read(buf, 0, (int)Math.min(len, bufLen));
if (nbytes == -1) {
foundEOF = true;
return length;
}
cache.setLength(cache.length() + nbytes);
cache.write(buf, 0, nbytes);
len -= nbytes;
length += nbytes;
}
return pos;
}
/**
* Returns <code>true</code> since all
* <code>FileCacheSeekableStream</code> instances support seeking
* backwards.
*/
public boolean canSeekBackwards() {
return true;
}
/**
* Returns the current offset in this file.
*
* @return the offset from the beginning of the file, in bytes,
* at which the next read occurs.
*/
public long getFilePointer() {
return pointer;
}
/**
* Sets the file-pointer offset, measured from the beginning of this
* file, at which the next read occurs.
*
* @param pos the offset position, measured in bytes from the
* beginning of the file, at which to set the file
* pointer.
* @exception IOException if <code>pos</code> is less than
* <code>0</code> or if an I/O error occurs.
*/
public void seek(long pos) throws IOException {
if (pos < 0) {
throw new IOException("FileCacheSeekableStream position < 0 ---> pos=" +pos);
}
pointer = pos;
}
/**
* Reads the next byte of data from the input stream. The value byte is
* returned as an <code>int</code> in the range <code>0</code> to
* <code>255</code>. If no byte is available because the end of the stream
* has been reached, the value <code>-1</code> is returned. This method
* blocks until input data is available, the end of the stream is detected,
* or an exception is thrown.
*
* @return the next byte of data, or <code>-1</code> if the end of the
* stream is reached.
* @exception IOException if an I/O error occurs.
*/
public int read() throws IOException {
long next = pointer + 1;
long pos = readUntil(next);
if (pos >= next) {
cache.seek(pointer++);
return cache.read();
} else {
return -1;
}
}
/**
* Reads up to <code>len</code> bytes of data from the input stream into
* an array of bytes. An attempt is made to read as many as
* <code>len</code> bytes, but a smaller number may be read, possibly
* zero. The number of bytes actually read is returned as an integer.
*
* <p> This method blocks until input data is available, end of file is
* detected, or an exception is thrown.
*
* <p> If <code>b</code> is <code>null</code>, a
* <code>NullPointerException</code> is thrown.
*
* <p> If <code>off</code> is negative, or <code>len</code> is negative, or
* <code>off+len</code> is greater than the length of the array
* <code>b</code>, then an <code>IndexOutOfBoundsException</code> is
* thrown.
*
* <p> If <code>len</code> is zero, then no bytes are read and
* <code>0</code> is returned; otherwise, there is an attempt to read at
* least one byte. If no byte is available because the stream is at end of
* file, the value <code>-1</code> is returned; otherwise, at least one
* byte is read and stored into <code>b</code>.
*
* <p> The first byte read is stored into element <code>b[off]</code>, the
* next one into <code>b[off+1]</code>, and so on. The number of bytes read
* is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
* bytes actually read; these bytes will be stored in elements
* <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
* leaving elements <code>b[off+</code><i>k</i><code>]</code> through
* <code>b[off+len-1]</code> unaffected.
*
* <p> In every case, elements <code>b[0]</code> through
* <code>b[off]</code> and elements <code>b[off+len]</code> through
* <code>b[b.length-1]</code> are unaffected.
*
* <p> If the first byte cannot be read for any reason other than end of
* file, then an <code>IOException</code> is thrown. In particular, an
* <code>IOException</code> is thrown if the input stream has been closed.
*
* @param b the buffer into which the data is read.
* @param off the start offset in array <code>b</code>
* at which the data is written.
* @param len the maximum number of bytes to read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of
* the stream has been reached.
* @exception IOException if an I/O error occurs.
*/
public int read(byte[] b, int off, int len) throws IOException {
if (b == null) {
throw new NullPointerException();
}
if ((off < 0) || (len < 0) || (off + len > b.length)) {
throw new IndexOutOfBoundsException();
}
if (len == 0) {
return 0;
}
long pos = readUntil(pointer + len);
// len will always fit into an int so this is safe
len = (int)Math.min(len, pos - pointer);
if (len > 0) {
cache.seek(pointer);
cache.readFully(b, off, len);
pointer += len;
return len;
} else {
return -1;
}
}
/**
* Closes this stream and releases any system resources
* associated with the stream.
*
* @throws IOException if an I/O error occurs.
*/
public void close() throws IOException {
super.close();
cache.close();
cacheFile.delete();
}
}