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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.fsa;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.ByteOrder;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.nio.charset.Charset;
import com.yahoo.fsa.FSA;
/**
* Class for accessing meta-data (dat-files) used by FSA applications.
*
* @author <a href="mailto:boros@yahoo-inc.com">Peter Boros</a>
**/
public class MetaData {
private boolean _ok = false;
private MappedByteBuffer _header;
private MappedByteBuffer _data;
private Charset _charset;
public MetaData(String filename){
init(filename, "utf-8");
}
public MetaData(String filename, String charsetname){
init(filename, charsetname);
}
public boolean isOk(){
return _ok;
}
private void init(String filename, String charsetname){
_charset = Charset.forName(charsetname);
FileInputStream file;
try {
file = new FileInputStream(filename);
}
catch (FileNotFoundException e) {
System.out.print("MetaData file " + filename + " not found.\n");
return;
}
try {
_header = file.getChannel().map(MapMode.READ_ONLY,0,256);
_header.order(ByteOrder.LITTLE_ENDIAN);
if(h_magic()!=-2025936501){
System.out.print("MetaData bad magic " + h_magic() +"\n");
return;
}
_data = file.getChannel().map(MapMode.READ_ONLY,
256,
h_size());
_data.order(ByteOrder.LITTLE_ENDIAN);
_ok=true;
}
catch (IOException e) {
System.out.print("MetaData IO exception.\n");
return;
}
}
private int h_magic(){
return _header.getInt(0);
}
private int h_version(){
return _header.getInt(4);
}
private int h_checksum(){
return _header.getInt(8);
}
private int h_size(){
return _header.getInt(12);
}
private int h_reserved(int i){
if(i<0||i>9){
return 0;
}
return _header.getInt(16+4*i);
}
private int h_user(int i){
if(i<0||i>49){
return 0;
}
return _header.getInt(56+4*i);
}
private ByteBuffer encode(CharBuffer chrbuf){
return _charset.encode(chrbuf);
}
private String decode(ByteBuffer buf){
return _charset.decode(buf).toString();
}
public int user(int i){
if(!_ok){
return 0;
}
return h_user(i);
}
public int getIntEntry(int idx)
{
if(_ok){
return _data.getInt(idx*4);
}
else
return 0;
}
public ByteBuffer getDirectRecordEntry(int idx, int size)
{
if(_ok){
ByteBuffer meta = ByteBuffer.allocate(size);
meta.order(ByteOrder.LITTLE_ENDIAN);
_data.position(idx*size);
_data.get(meta.array(),0,size);
return meta;
}
else
return null;
}
public ByteBuffer getIndirectRecordEntry(int idx, int size)
{
if(_ok){
int offset = _data.getInt(idx*4);
ByteBuffer meta = ByteBuffer.allocate(size);
meta.order(ByteOrder.LITTLE_ENDIAN);
_data.position(offset);
_data.get(meta.array(),0,size);
return meta;
}
else
return null;
}
public ByteBuffer getIndirectRecordEntry(int idx)
{
if(_ok){
int offset = _data.getInt(idx*4);
int size = _data.getInt(offset);
ByteBuffer meta = ByteBuffer.allocate(size);
meta.order(ByteOrder.LITTLE_ENDIAN);
_data.position(offset+4);
_data.get(meta.array(),0,size);
return meta;
}
else
return null;
}
public String getStringEntry(int stringOffset){
if(_ok){
int length = 0;
_data.position(stringOffset);
while(_data.get()!=0){
length++;
}
ByteBuffer meta = ByteBuffer.allocate(length);
meta.order(ByteOrder.LITTLE_ENDIAN);
_data.position(stringOffset);
_data.get(meta.array(),0,length);
return decode(meta);
}
return null;
}
public String[] getStringArrayEntry(int stringOffset, int numStrings){
if(_ok && numStrings>0){
String[] stringArray = new String[numStrings];
int pos=stringOffset;
for(int i=0;i<numStrings;i++){
int length = 0;
_data.position(pos);
while(_data.get()!=0){
length++;
}
ByteBuffer meta = ByteBuffer.allocate(length);
meta.order(ByteOrder.LITTLE_ENDIAN);
_data.position(pos);
_data.get(meta.array(),0,length);
stringArray[i] = decode(meta);
pos += length+1;
}
return stringArray;
}
return null;
}
//// test ////
public static void main(String[] args) {
String file = "dmozPred_2.dat";
MetaData metaData = new MetaData(file);
System.out.println("Loading MetaData "+file+": "+metaData.isOk());
}
}
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