/*
* 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.
*/
package java.io;
import java.util.Arrays;
/**
* Wraps an existing {@link InputStream} and <em>buffers</em> the input.
* Expensive interaction with the underlying input stream is minimized, since
* most (smaller) requests can be satisfied by accessing the buffer alone. The
* drawback is that some extra space is required to hold the buffer and that
* copying takes place when filling that buffer, but this is usually outweighed
* by the performance benefits.
*
* <p/>A typical application pattern for the class looks like this:<p/>
*
* <pre>
* BufferedInputStream buf = new BufferedInputStream(new FileInputStream("file.java"));
* </pre>
*
* @see BufferedOutputStream
*/
public class BufferedInputStream extends FilterInputStream {
/**
* The default buffer size if it is not specified.
*
* @hide
*/
public static final int DEFAULT_BUFFER_SIZE = 8192;
/**
* The buffer containing the current bytes read from the target InputStream.
*/
protected volatile byte[] buf;
/**
* The total number of bytes inside the byte array {@code buf}.
*/
protected int count;
/**
* The current limit, which when passed, invalidates the current mark.
*/
protected int marklimit;
/**
* The currently marked position. -1 indicates no mark has been set or the
* mark has been invalidated.
*/
protected int markpos = -1;
/**
* The current position within the byte array {@code buf}.
*/
protected int pos;
/**
* Constructs a new {@code BufferedInputStream}, providing {@code in} with a buffer
* of 8192 bytes.
*
* <p><strong>Warning:</strong> passing a null source creates a closed
* {@code BufferedInputStream}. All read operations on such a stream will
* fail with an IOException.
*
* @param in the {@code InputStream} the buffer reads from.
*/
public BufferedInputStream(InputStream in) {
this(in, DEFAULT_BUFFER_SIZE);
}
/**
* Constructs a new {@code BufferedInputStream}, providing {@code in} with {@code size} bytes
* of buffer.
*
* <p><strong>Warning:</strong> passing a null source creates a closed
* {@code BufferedInputStream}. All read operations on such a stream will
* fail with an IOException.
*
* @param in the {@code InputStream} the buffer reads from.
* @param size the size of buffer in bytes.
* @throws IllegalArgumentException if {@code size <= 0}.
*/
public BufferedInputStream(InputStream in, int size) {
super(in);
if (size <= 0) {
throw new IllegalArgumentException("size <= 0");
}
buf = new byte[size];
}
/**
* Returns an estimated number of bytes that can be read or skipped without blocking for more
* input. This method returns the number of bytes available in the buffer
* plus those available in the source stream, but see {@link InputStream#available} for
* important caveats.
*
* @return the estimated number of bytes available
* @throws IOException if this stream is closed or an error occurs
*/
@Override
public synchronized int available() throws IOException {
InputStream localIn = in; // 'in' could be invalidated by close()
if (buf == null || localIn == null) {
throw streamClosed();
}
return count - pos + localIn.available();
}
private IOException streamClosed() throws IOException {
throw new IOException("BufferedInputStream is closed");
}
/**
* Closes this stream. The source stream is closed and any resources
* associated with it are released.
*
* @throws IOException
* if an error occurs while closing this stream.
*/
@Override
public void close() throws IOException {
buf = null;
InputStream localIn = in;
in = null;
if (localIn != null) {
localIn.close();
}
}
private int fillbuf(InputStream localIn, byte[] localBuf)
throws IOException {
if (markpos == -1 || (pos - markpos >= marklimit)) {
/* Mark position not set or exceeded readlimit */
int result = localIn.read(localBuf);
if (result > 0) {
markpos = -1;
pos = 0;
count = result == -1 ? 0 : result;
}
return result;
}
if (markpos == 0 && marklimit > localBuf.length) {
/* Increase buffer size to accommodate the readlimit */
int newLength = localBuf.length * 2;
if (newLength > marklimit) {
newLength = marklimit;
}
byte[] newbuf = new byte[newLength];
System.arraycopy(localBuf, 0, newbuf, 0, localBuf.length);
// Reassign buf, which will invalidate any local references
// FIXME: what if buf was null?
localBuf = buf = newbuf;
} else if (markpos > 0) {
System.arraycopy(localBuf, markpos, localBuf, 0, localBuf.length
- markpos);
}
/* Set the new position and mark position */
pos -= markpos;
count = markpos = 0;
int bytesread = localIn.read(localBuf, pos, localBuf.length - pos);
count = bytesread <= 0 ? pos : pos + bytesread;
return bytesread;
}
/**
* Sets a mark position in this stream. The parameter {@code readlimit}
* indicates how many bytes can be read before a mark is invalidated.
* Calling {@code reset()} will reposition the stream back to the marked
* position if {@code readlimit} has not been surpassed. The underlying
* buffer may be increased in size to allow {@code readlimit} number of
* bytes to be supported.
*
* @param readlimit
* the number of bytes that can be read before the mark is
* invalidated.
* @see #reset()
*/
@Override
public synchronized void mark(int readlimit) {
marklimit = readlimit;
markpos = pos;
}
/**
* Indicates whether {@code BufferedInputStream} supports the {@code mark()}
* and {@code reset()} methods.
*
* @return {@code true} for BufferedInputStreams.
* @see #mark(int)
* @see #reset()
*/
@Override
public boolean markSupported() {
return true;
}
/**
* Reads a single byte from this stream and returns it as an integer in the
* range from 0 to 255. Returns -1 if the end of the source string has been
* reached. If the internal buffer does not contain any available bytes then
* it is filled from the source stream and the first byte is returned.
*
* @return the byte read or -1 if the end of the source stream has been
* reached.
* @throws IOException
* if this stream is closed or another IOException occurs.
*/
@Override
public synchronized int read() throws IOException {
// Use local refs since buf and in may be invalidated by an
// unsynchronized close()
byte[] localBuf = buf;
InputStream localIn = in;
if (localBuf == null || localIn == null) {
throw streamClosed();
}
/* Are there buffered bytes available? */
if (pos >= count && fillbuf(localIn, localBuf) == -1) {
return -1; /* no, fill buffer */
}
// localBuf may have been invalidated by fillbuf
if (localBuf != buf) {
localBuf = buf;
if (localBuf == null) {
throw streamClosed();
}
}
/* Did filling the buffer fail with -1 (EOF)? */
if (count - pos > 0) {
return localBuf[pos++] & 0xFF;
}
return -1;
}
@Override public synchronized int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
// Use local ref since buf may be invalidated by an unsynchronized
// close()
byte[] localBuf = buf;
if (localBuf == null) {
throw streamClosed();
}
Arrays.checkOffsetAndCount(buffer.length, byteOffset, byteCount);
if (byteCount == 0) {
return 0;
}
InputStream localIn = in;
if (localIn == null) {
throw streamClosed();
}
int required;
if (pos < count) {
/* There are bytes available in the buffer. */
int copylength = count - pos >= byteCount ? byteCount : count - pos;
System.arraycopy(localBuf, pos, buffer, byteOffset, copylength);
pos += copylength;
if (copylength == byteCount || localIn.available() == 0) {
return copylength;
}
byteOffset += copylength;
required = byteCount - copylength;
} else {
required = byteCount;
}
while (true) {
int read;
/*
* If we're not marked and the required size is greater than the
* buffer, simply read the bytes directly bypassing the buffer.
*/
if (markpos == -1 && required >= localBuf.length) {
read = localIn.read(buffer, byteOffset, required);
if (read == -1) {
return required == byteCount ? -1 : byteCount - required;
}
} else {
if (fillbuf(localIn, localBuf) == -1) {
return required == byteCount ? -1 : byteCount - required;
}
// localBuf may have been invalidated by fillbuf
if (localBuf != buf) {
localBuf = buf;
if (localBuf == null) {
throw streamClosed();
}
}
read = count - pos >= required ? required : count - pos;
System.arraycopy(localBuf, pos, buffer, byteOffset, read);
pos += read;
}
required -= read;
if (required == 0) {
return byteCount;
}
if (localIn.available() == 0) {
return byteCount - required;
}
byteOffset += read;
}
}
/**
* Resets this stream to the last marked location.
*
* @throws IOException
* if this stream is closed, no mark has been set or the mark is
* no longer valid because more than {@code readlimit} bytes
* have been read since setting the mark.
* @see #mark(int)
*/
@Override
public synchronized void reset() throws IOException {
if (buf == null) {
throw new IOException("Stream is closed");
}
if (markpos == -1) {
throw new IOException("Mark has been invalidated.");
}
pos = markpos;
}
/**
* Skips {@code byteCount} bytes in this stream. Subsequent calls to
* {@code read} will not return these bytes unless {@code reset} is
* used.
*
* @param byteCount
* the number of bytes to skip. {@code skip} does nothing and
* returns 0 if {@code byteCount} is less than zero.
* @return the number of bytes actually skipped.
* @throws IOException
* if this stream is closed or another IOException occurs.
*/
@Override
public synchronized long skip(long byteCount) throws IOException {
// Use local refs since buf and in may be invalidated by an
// unsynchronized close()
byte[] localBuf = buf;
InputStream localIn = in;
if (localBuf == null) {
throw streamClosed();
}
if (byteCount < 1) {
return 0;
}
if (localIn == null) {
throw streamClosed();
}
if (count - pos >= byteCount) {
pos += byteCount;
return byteCount;
}
long read = count - pos;
pos = count;
if (markpos != -1) {
if (byteCount <= marklimit) {
if (fillbuf(localIn, localBuf) == -1) {
return read;
}
if (count - pos >= byteCount - read) {
pos += byteCount - read;
return byteCount;
}
// Couldn't get all the bytes, skip what we read
read += (count - pos);
pos = count;
return read;
}
}
return read + localIn.skip(byteCount - read);
}
}