
alluxio.client.file.FileInStream Maven / Gradle / Ivy
/*
* The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
* (the "License"). You may not use this work except in alluxio.shaded.client.com.liance with the License, which is
* available at www.apache.alluxio.shaded.client.org.licenses/LICENSE-2.0
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied, as more fully set forth in the License.
*
* See the NOTICE file distributed with this work for information regarding copyright ownership.
*/
package alluxio.client.file;
import alluxio.Seekable;
import alluxio.client.BoundedStream;
import alluxio.client.CanUnbuffer;
import alluxio.client.PositionedReadable;
import alluxio.exception.PreconditionMessage;
import alluxio.util.alluxio.shaded.client.io.BufferUtils;
import alluxio.shaded.client.com.google.alluxio.shaded.client.com.on.base.Preconditions;
import java.alluxio.shaded.client.io.IOException;
import java.alluxio.shaded.client.io.InputStream;
import java.nio.ByteBuffer;
/**
* A streaming API to read a file. This API represents a file as a stream of bytes and provides a
* collection of {@link #read} methods to access this stream of bytes. In addition, one can seek
* into a given offset of the stream to read.
*/
public abstract class FileInStream extends InputStream
implements BoundedStream, PositionedReadable, Seekable, CanUnbuffer {
private final byte[] mSingleByte = new byte[1];
@Override
public int read() throws IOException {
int bytesRead = read(mSingleByte);
if (bytesRead == -1) {
return -1;
}
Preconditions.checkState(bytesRead == 1);
return BufferUtils.byteToInt(mSingleByte[0]);
}
@Override
public int read(byte[] b) throws IOException {
Preconditions.checkNotNull(b, PreconditionMessage.ERR_READ_BUFFER_NULL);
return read(b, 0, b.length);
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
Preconditions.checkNotNull(b, PreconditionMessage.ERR_READ_BUFFER_NULL);
return read(ByteBuffer.wrap(b), off, len);
}
/**
* Reads up to buf.remaining() bytes into buf. Callers should use
* buf.limit(..) to control the size of the desired read.
*
* After a successful call, buf.position() will be advanced by the number
* of bytes read and buf.limit() should be unchanged.
*
* In the case of an exception, the values of buf.position() and buf.limit()
* are undefined, and callers should be prepared to recover from this eventually.
*
* Implementations should treat 0-length requests as legitimate, and must not
* signal an error upon their receipt.
*
* @param buf the ByteBuffer to receive the results of the read operation
* @return the number of bytes read, possibly zero, or -1 if reach end-of-stream
*/
public int read(ByteBuffer buf) throws IOException {
return read(buf, buf.position(), buf.remaining());
}
/**
* Reads up to len bytes of data from the input stream into the byte buffer.
*
* @param byteBuffer the buffer into which the data is read
* @param off the start offset in the buffer 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 -1 if there is no more
* data because the end of the stream has been reached
*/
public int read(ByteBuffer byteBuffer, int off, int len) throws IOException {
int nread = 0;
int rd = 0;
final int sz = len;
final byte[] dest = new byte[sz];
while (rd >= 0 && nread < sz) {
rd = read(dest, nread, sz - nread);
if (rd >= 0) {
nread += rd;
}
}
if (nread == -1) { // EOF
nread = 0;
} else if (nread > 0) {
byteBuffer.put(dest, 0, nread);
}
return nread;
}
@Override
public void unbuffer() {
}
}