/*
* Copyright (C) 2014 Indeed Inc.
*
* 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.
*/
package com.indeed.flamdex.simple;
import com.indeed.util.core.reference.SharedReference;
import com.indeed.flamdex.api.DocIdStream;
import com.indeed.flamdex.api.TermIterator;
import com.indeed.util.mmap.DirectMemory;
import com.indeed.util.mmap.MMapBuffer;
import org.apache.log4j.Logger;
import java.io.IOException;
/**
* @author jsgroth
*/
final class SimpleDocIdStream implements DocIdStream {
private static final Logger log = Logger.getLogger(SimpleDocIdStream.class);
public static final int BUFFER_SIZE = 8192;
private final MapCache mapCache;
private final byte[] buffer;
private long bufferOffset;
private int bufferLen;
private int bufferPtr;
private DirectMemory memory;
private SharedReference<MMapBuffer> file;
private int docsRemaining;
private int lastDoc;
private String currentFileOpen;
SimpleDocIdStream(MapCache mapCache) {
this(mapCache, new byte[BUFFER_SIZE]);
}
SimpleDocIdStream(MapCache mapCache, byte[] buffer) {
this.mapCache = mapCache;
this.buffer = buffer;
bufferOffset = 0L;
bufferLen = 0;
bufferPtr = 0;
}
@Override
public void reset(TermIterator term) {
if (!(term instanceof SimpleTermIterator)) throw new IllegalArgumentException("invalid term iterator");
try {
internalReset((SimpleTermIterator)term);
} catch (IOException e) {
close();
throw new RuntimeException(e);
}
}
private void internalReset(SimpleTermIterator term) throws IOException {
final String filename = term.getFilename();
if (!filename.equals(currentFileOpen)) {
if (file != null) file.close();
file = mapCache.copyOrOpen(filename);
memory = file.get().memory();
currentFileOpen = filename;
// to force a refill
bufferOffset = 0L;
bufferLen = 0;
bufferPtr = 0;
}
final long offset = term.getOffset();
if (offset >= bufferOffset && offset < bufferOffset + bufferLen) {
bufferPtr = (int) (offset - bufferOffset);
} else {
refillBuffer(offset);
}
docsRemaining = term.docFreq();
lastDoc = 0;
}
@Override
public int fillDocIdBuffer(int[] docIdBuffer) {
if (docsRemaining == 0) return 0;
try {
final int n = Math.min(docsRemaining, docIdBuffer.length);
for (int i = 0; i < n; ++i) {
final int docDelta = readVInt();
lastDoc += docDelta;
docIdBuffer[i] = lastDoc;
}
docsRemaining -= n;
return n;
} catch (IOException e) {
close();
throw new RuntimeException(e);
}
}
@Override
public void close() {
try {
if (file != null) {
file.close();
file = null;
}
} catch (IOException e) {
log.error("error closing file", e);
}
}
private int readVInt() throws IOException {
int ret = 0;
int shift = 0;
do {
if (bufferPtr == bufferLen) refillBuffer(bufferOffset + bufferLen);
byte b = buffer[bufferPtr++];
ret |= ((b & 0x7F) << shift);
if (b >= 0) return ret;
shift += 7;
} while (true);
}
private void refillBuffer(long offset) throws IOException {
bufferLen = (int)Math.min(buffer.length, memory.length() - offset);
if (bufferLen > 0) {
memory.getBytes(offset, buffer, 0, bufferLen);
}
bufferOffset = offset;
bufferPtr = 0;
}
}