com.bigdata.bfs.FileVersionInputStream Maven / Gradle / Ivy
package com.bigdata.bfs;
import java.io.DataInput;
import java.io.IOException;
import java.io.InputStream;
import com.bigdata.btree.ITuple;
import com.bigdata.btree.ITupleIterator;
import com.bigdata.btree.keys.KeyBuilder;
import com.bigdata.rawstore.IBlock;
import com.bigdata.util.Bytes;
/**
* Reads from blocks visited by a range scan for a file and version.
*
* @author Bryan Thompson
* @version $Id$
*/
public class FileVersionInputStream extends InputStream {
protected final String id;
protected final int version;
private final ITupleIterator src;
/**
* The current block# whose data are being read.
*/
private long block;
/**
* A buffer holding the current block's data. This is initially filled
* from the first block by the ctor. When no more data is available it
* is set to null to indicate that the input stream has
* been exhausted.
*
* @todo reuse buffers sized out to the block size.
*/
private byte[] b;
/**
* The next byte to be returned from the current block's data.
*/
private int off;
/**
* The #of bytes remaining in the current block's data.
*/
private int len;
/**
* The file identifier.
*/
public String getId() {
return id;
}
/**
* The file version identifer.
*/
public int getVersion() {
return version;
}
/**
* The current block identifier.
*/
public long getBlock() {
return block;
}
public FileVersionInputStream(String id, int version, ITupleIterator src) {
this.id = id;
this.version = version;
this.src = src;
// read the first block of data.
nextBlock();
}
/**
* Reads the next block of data from the iterator and sets it on the
* internal buffer. If the iterator is exhausted then the internal
* buffer is set to null.
*
* @return true iff another block of data was read.
*/
private boolean nextBlock() {
assert b == null || off == len;
if (!src.hasNext()) {
BigdataFileSystem.log.info("No more blocks: id=" + id
+ ", version=" + version);
b = null;
off = 0;
len = 0;
return false;
}
final ITuple tuple = src.next();
/*
* decode the block address.
*/
final long addr;
try {
DataInput in = tuple.getValueStream();
addr = in.readLong();
} catch (IOException e) {
throw new RuntimeException(e);
}
if (addr == 0L) {
/*
* Note: empty blocks are allowed and are recorded with 0L as
* their address.
*/
b = new byte[] {};
off = 0;
len = 0;
BigdataFileSystem.log.info("Read zero bytes: id=" + id
+ ", version=" + version + ", block=" + block);
} else {
byte[] key = tuple.getKey();
// decode the block identifier from the key.
// block = KeyBuilder.decodeLong(tuple.getKeyBuffer().array(),
// tuple.getKeyBuffer().pos() - Bytes.SIZEOF_LONG);
block = KeyBuilder.decodeLong(key, key.length - Bytes.SIZEOF_LONG);
final IBlock tmp = tuple.readBlock(addr);
final int nbytes = tmp.length();
// @todo reuse buffer!
b = new byte[nbytes];
off = 0;
len = nbytes;
try {
final int nread = tmp.inputStream().read(b, off, len);
if (nread != len) {
throw new RuntimeException("Expecting " + len
+ " bytes but read " + nread);
}
} catch (IOException e) {
throw new RuntimeException(e);
}
BigdataFileSystem.log.info("Read " + b.length + " bytes: id=" + id
+ ", version=" + version + ", block=" + block);
}
return true;
}
public int read() throws IOException {
if (b == null) {
// nothing left to read.
return -1;
}
if (off == len) {
if (!nextBlock()) {
// no more blocks so nothing left to read.
return -1;
}
}
// the next byte.
int v = (0xff & b[off++]);
return v;
}
/**
* Overriden for greater efficiency.
*/
public int read(byte[] b, int off, int len) throws IOException {
if (b == null) {
// nothing left to read.
return -1;
}
if (this.off == this.len) {
if (!nextBlock()) {
// no more blocks so nothing left to read.
return -1;
}
}
/*
* Copy everything in our internal buffer up to the #of bytes
* remaining in the caller's buffer.
*/
final int n = Math.min(this.len, len);
System.arraycopy(this.b, this.off, b, off, n);
this.off += n;
return n;
}
}
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