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Diffstat (limited to 'src/core/src/data/filters/MVDataCombiner.java')
-rw-r--r-- | src/core/src/data/filters/MVDataCombiner.java | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/src/core/src/data/filters/MVDataCombiner.java b/src/core/src/data/filters/MVDataCombiner.java new file mode 100644 index 0000000..1b2eb3f --- /dev/null +++ b/src/core/src/data/filters/MVDataCombiner.java @@ -0,0 +1,164 @@ +/* + * SSSync, a Simple and Stupid Synchronizer for data with multi-valued attributes + * Copyright (C) 2014 Ludovic Pouzenc <ludovic@pouzenc.fr> + * + * This file is part of SSSync. + * + * SSSync is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * SSSync is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with SSSync. If not, see <http://www.gnu.org/licenses/> + */ + +package data.filters; + +import java.util.Iterator; +import java.util.NoSuchElementException; + +import data.MVDataEntry; +import data.io.AbstractMVDataReader; +import data.io.MVDataReader; + +/** + * Combines arbitrary number of MVData* sources while behaving same as AbstractMVDataReader. + * This could enable a sync implementation to merge multiple sources + * before sync'ing in a transparent manner. + * To prevent memory consumption, this assumes that all sources will be read + * with lexicographical ascending order on the "key" field. + * + * @author lpouzenc + */ +public class MVDataCombiner extends AbstractMVDataReader { + + public enum MVDataCombineMode { PRIMARY_SOURCE, MERGE_APPEND, MERGE_REPLACE, OVERRIDE }; + + private final MVDataReader[] readers; + private final MVDataCombineMode[] mergeModes; + + private transient Iterator<MVDataEntry>[] readerIterators; + private transient MVDataEntry[] lookAheadData; + private transient String lastKey; + + + public MVDataCombiner(String dataSourceName, MVDataReader[] readers, MVDataCombineMode mergeModes[]) { + if ( readers == null || mergeModes == null || (mergeModes.length != readers.length) ) { + throw new IllegalArgumentException("readers and mergeModes arrays should have same size"); + } + if ( ! (mergeModes.length > 0) || mergeModes[0] != MVDataCombineMode.PRIMARY_SOURCE ) { + throw new IllegalArgumentException("MVDataCombiner first mergeModes should always be PRIMARY_SOURCE"); + } + + this.dataSourceName = dataSourceName; + this.readers = readers.clone(); + this.mergeModes = mergeModes.clone(); + } + + /** + * {@inheritDoc} + */ + @Override + @SuppressWarnings("unchecked") /* for new Iterator[...] */ + public Iterator<MVDataEntry> iterator() { + // Be cautious to reset everything + readerIterators = new Iterator[readers.length]; + for (int i=0; i<readers.length;i++) { + readerIterators[i] = readers[i].iterator(); + } + lookAheadData = new MVDataEntry[readers.length]; + lastKey = null; + + return this; + } + + /** + * {@inheritDoc} + */ + @Override + public boolean hasNext() { + for ( MVDataEntry line : lookAheadData ) { + if ( line != null ) { return true; } + } + for ( MVDataReader reader : readers ) { + if ( reader.hasNext() ) { return true; } + } + return false; + } + + /** + * {@inheritDoc} + */ + @Override + public MVDataEntry next() { + + final String currentKey = lookAheadAll(); + + // Check if there was unsorted lines in source data + if ( lastKey != null && (currentKey.compareTo(lastKey) < 0) ) { + //XXX : this is checked here and in SafeDataReader (redundant), but both are optionnal... + throw new UnsupportedOperationException("At least one data source is out of order. " + + "Data sources are excepted to be read sorted by MVDataEntry key (ascending lexicogrpahical order)"); + } + + // Merge all data sources for key currentKey + MVDataEntry result = null; + for ( int i=0; i<lookAheadData.length; i++) { + if ( lookAheadData[i] != null && lookAheadData[i].getKey().equals(currentKey) ) { + if ( result == null ) { + result = lookAheadData[i]; + } else { + //XXX : some items in LDAP could have constrains like : "not multi-valued". Force MERGE_REPLACE mode ? + //FIXME : honor all Combine modes + result.mergeValues( (mergeModes[i] == MVDataCombineMode.MERGE_APPEND ),lookAheadData[i]); + } + lookAheadData[i]=null; // "Pop" the used entry + } + } + + lastKey = currentKey; + + return result; + } + + private String lookAheadAll() { + String minKey=null; + + // Feed the look-ahead buffer (look forward by 1 value for each reader) + for ( int i=0; i<lookAheadData.length; i++) { + if ( lookAheadData[i] == null && readerIterators[i].hasNext() ) { + lookAheadData[i] = readerIterators[i].next(); + } + } + + // Find the least RelData key from look-ahead buffers + for (MVDataEntry entry: lookAheadData) { + if ( entry != null ) { + final String minKeyCandidate = entry.getKey(); + if ( minKey == null || minKey.compareTo(minKeyCandidate) > 0 ) { + minKey = minKeyCandidate; + } + } + } + + // Sanity checks + if ( minKey == null ) { + // Every reader is empty and look-ahead buffer is empty (hasNext() should have said false) + throw new NoSuchElementException(); + } + + return minKey; + } + + // Boring accessors + + public String getLastKey() { + return lastKey; + } +} |