io.milton.zsync.MakeContextEx Maven / Gradle / Ivy
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/*
* 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.
*/
package io.milton.zsync;
import java.util.LinkedList;
import java.util.List;
/**
* An extension of MakeContext that stores block matches in a way more suitable for upload.
*
* This object differs from a MakeContext in that it allows multiple local blocks to be matched to a single remote block.
* It does this by overriding the put method to save matches to an array of Lists, rather than
* to fileMap, which only allows one entry per remote block. It also overrides the delete
* method to do nothing, instead of removing the ChecksumPair from the ChainingHash.
*
* MakeContextEx is used internally by UploadMakerEx in place of MakeContext as an argument to MapMatcher.mapMatcher.
*
* @see UploadMakerEx
* @author Nick
*
*/
public class MakeContextEx extends MakeContext {
/* An array storing a List of matches for each remote block */
private final List[] matchMap;
/* The minimum local offset of the next match */
private long nextOffset;
private final int blocksize;
/**
* Constructs a MakeContextEx from an already-initialized ChainingHash.
*
* @param hashtable The hashtable obtained from a MetaFileReader
* @param blockcount The number of blocks in the remote file
* @param blocksize The number of bytes per block
*/
public MakeContextEx(ChainingHash hashtable, int blockcount, int blocksize) {
super(hashtable, null);
this.matchMap = new LinkedList[blockcount];
this.blocksize = blocksize;
this.nextOffset = 0;
}
/**
* Returns a list of OffsetPairs representing the block-matches between the local and
* remote file.
*
* @return The list of block matches
* @see OffsetPair
*/
public List getReverseMap() {
/*
* Concatenates the Lists of OffsetPairs in matchMap into a single List
*/
List reverseMap = new LinkedList<>();
for (List item : matchMap) {
if (item != null) {
reverseMap.addAll(item);
}
}
return reverseMap;
}
/**
* Adds a match to the list of block matches. Matching of overlapping client-side blocks
* is prevented.
*
* @param blockIndex Index of the remote block
* @param offset Byte offset of the local block
*/
@Override
public void put(int blockIndex, long offset){
/* Currently, a match to the last block of the remote file is not permitted */
if (blockIndex >= matchMap.length - 1){
return;
}
/*
* Prevents matching a local block that overlaps the previous one, in case MapMatcher.mapMatcher
* does not already prevent this.
*/
if (offset < nextOffset){
return;
}
if ( matchMap[blockIndex] == null ) {
matchMap[blockIndex] = new LinkedList<>();
}
matchMap[blockIndex].add( new OffsetPair(offset, blockIndex) );
nextOffset = offset + blocksize; //Set nextOffset to past the end of the previous match
}
/**
* Overrides delete in MakeContext to do nothing. Local blocks
* with the identical checksums will all then match to the first matching ChecksumPair in ChainingHash
*
* @param key Unused in this override. Can be null
*/
@Override
public void delete(ChecksumPair key){
return;
}
@Override
public boolean matched(int blockIndex) {
if (blockIndex > 0 && blockIndex < this.blockcount()) {
return matchMap[blockIndex] != null;
}
return false;
}
@Override
public void removematch(int blockIndex) {
if (blockIndex > 0 && blockIndex < this.blockcount()) {
matchMap[blockIndex] = null;
}
}
@Override
public int blockcount() {
return matchMap.length;
}
}