com.pivotal.gemfirexd.internal.client.am.BlobLocatorInputStream Maven / Gradle / Ivy
/*
Derby - Class com.pivotal.gemfirexd.internal.client.am.BlobLocatorInputStream
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.
*/
/*
* Changes for GemFireXD distributed data platform (some marked by "GemStone changes")
*
* Portions Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
*
* Licensed 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. See accompanying
* LICENSE file.
*/
package com.pivotal.gemfirexd.internal.client.am;
import java.io.IOException;
import com.pivotal.gemfirexd.internal.shared.common.sanity.SanityManager;
/**
* An InputStream that will use an locator to fetch the
* Blob value from the server.
*
* Closing a ByteArrayInputStream has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an IOException.
*
* This InputStream implementation is pretty basic. No
* buffering of data is done. Hence, for efficieny #read(byte[])
* should be used instead of #read(). Marks are not supported, but it
* should be pretty simple to extend the implementation to support
* this. A more efficient skip implementation should also be
* straight-forward.
*/
public class BlobLocatorInputStream extends java.io.InputStream
{
/**
* Create an InputStream for reading the
* Blob value represented by the given locator based
* Blob object.
* @param connection connection to be used to read the
* Blob value from the server
* @param blob Blob object that contains locator for
* the Blob value on the server.
* @throws SqlException if an error occurs when obtaining the
* length of the Blob.
*/
public BlobLocatorInputStream(Connection connection, Blob blob)
throws SqlException
{
if (SanityManager.DEBUG) {
SanityManager.ASSERT(blob.isLocator());
}
// GemStone changes BEGIN
/* (original code)
this.connection = connection;
*/
// GemStone changes END
this.blob = blob;
this.currentPos = 1;
//In this case a subset of the Blob has
//not been requested for. We set maxPos
//to -1 and instead will call
//blob.sqlLength() each time we want
//the maximum length.
this.maxPos = -1;
}
/**
* Create an InputStream for reading the
* Blob value represented by the given locator based
* Blob object.
* @param connection connection to be used to read the
* Blob value from the server
* @param blob Blob object that contains locator for
* the Blob value on the server.
* @param position the position in the Blob of the first
* byte to read.
* @param length the maximum number of bytes to read from
* the Blob.
* @throws SqlException if an error occurs when obtaining the
* length of the Blob.
*/
public BlobLocatorInputStream(Connection connection, Blob blob,
long position, long length)
throws SqlException
{
if (SanityManager.DEBUG) {
SanityManager.ASSERT(blob.isLocator());
}
// GemStone changes BEGIN
/* (original code)
this.connection = connection;
*/
// GemStone changes END
this.blob = blob;
this.currentPos = position;
if (length != -1) {//verify if length is -1
this.maxPos = Math.min(blob.sqlLength(), position + length - 1);
}
else {
this.maxPos = -1;
}
}
/**
* @see java.io.InputStream#read()
*
* This method fetches one byte at a time from the server. For more
* efficient retrieval, use #read(byte[]).
*/
public int read() throws IOException
{
byte[] bytes = readBytes(1);
if (bytes.length == 0) { // EOF
return -1;
} else {
// convert byte in range [-128,127] to int in range [0,255]
return bytes[0] & 0xff;
}
}
/**
* @see java.io.InputStream#read(byte[], int, int)
*/
public int read(byte[] b, int off, int len) throws IOException
{
if (len == 0) return 0;
if ((off < 0) || (len < 0) || (off+len > b.length)) {
throw new IndexOutOfBoundsException();
}
byte[] bytes = readBytes(len);
if (bytes.length == 0) { // EOF
return -1;
} else {
System.arraycopy(bytes, 0, b, off, bytes.length);
return bytes.length;
}
}
/**
* Read the next len bytes of the Blob
* value from the server.
*
* @param len number of bytes to read
* @throws java.io.IOException Wrapped SqlException if reading
* from server fails.
* @return byte[] containing the read bytes
*/
private byte[] readBytes(int len) throws IOException
{
try {
//stores the actual length that can be read
//based on the value of the current position
//in the stream(currentPos) and the length of
//the stream.
int actualLength = -1;
//check if maxPos has been set and calculate actualLength
//based on that.
if(maxPos != -1) {
//maxPos has been set. use maxPos to calculate the
//actual length based on the value set for maxPos.
actualLength
= (int )Math.min(len, maxPos - currentPos + 1);
}
else {
//The subset of the Blob was not requested for
//hence maxPos is -1. Here we use blob.sqllength
//instead.
actualLength
= (int )Math.min(len, blob.sqlLength() - currentPos + 1);
}
// GemStone changes BEGIN
byte[] result = blob.locatorProcs_
/* (original code)
byte[] result = connection.locatorProcedureCall()
*/
// GemStone changes END
.blobGetBytes(blob.getLocator(), currentPos, actualLength);
currentPos += result.length;
return result;
} catch (SqlException ex) {
IOException ioEx = new IOException();
ioEx.initCause(ex);
throw ioEx;
}
}
/**
* Connection used to read Blob from server.
*/
// GemStone changes BEGIN
/* (original code)
private final Connection connection;
*/
// GemStone changes END
/**
* The Blob to be accessed.
*/
private final Blob blob;
/**
* Current position in the underlying Blob.
* Blobs are indexed from 1
*/
private long currentPos;
/**
* Position in Blob where to stop reading.
* maxPos starts counting from 1.
*/
private final long maxPos;
}