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Merge pull request #8 from amorris13/master
Upstream changes to archive patcher:
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118 changes: 118 additions & 0 deletions
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...or/src/main/java/com/google/archivepatcher/generator/DeltaFriendlyOldBlobSizeLimiter.java
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| // Copyright 2016 Google Inc. All rights reserved. | ||
| // | ||
| // 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. | ||
|
|
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| package com.google.archivepatcher.generator; | ||
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| import java.io.File; | ||
| import java.util.ArrayList; | ||
| import java.util.Collections; | ||
| import java.util.Comparator; | ||
| import java.util.List; | ||
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|
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| /** | ||
| * Limits the size of the delta-friendly old blob, which is an implicit limitation on the amount of | ||
| * temp space required to apply a patch. | ||
| * | ||
| * <p>This class implements the following algorithm: | ||
| * | ||
| * <ol> | ||
| * <li>Check the size of the old archive and subtract it from the maximum size, this is the number | ||
| * of bytes that can be used to uncompress entries in the delta-friendly old file. | ||
| * <li>Identify all of the {@link QualifiedRecommendation}s that have {@link | ||
| * Recommendation#uncompressOldEntry} set to <code>true</code>. These identify all the entries | ||
| * that would be uncompressed in the delta-friendly old file. | ||
| * <li>Sort those {@link QualifiedRecommendation}s in order of decreasing uncompressed size. | ||
| * <li>Iterate over the list in order. For each entry, calculate the difference between the | ||
| * uncompressed size and the compressed size; this is the number of bytes that would be | ||
| * consumed to transform the data from compressed to uncompressed in the delta-friendly old | ||
| * file. If the number of bytes that would be consumed is less than the number of bytes | ||
| * remaining before hitting the cap, retain it; else, discard it. | ||
| * <li>Return the resulting list of the retained entries. Note that the order of this list may not | ||
| * be the same as the input order (i.e., it has been sorted in order of decreasing compressed | ||
| * size). | ||
| * </ol> | ||
| */ | ||
| public class DeltaFriendlyOldBlobSizeLimiter implements RecommendationModifier { | ||
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| /** The maximum size of the delta-friendly old blob. */ | ||
| private final long maxSizeBytes; | ||
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| private static final Comparator<QualifiedRecommendation> COMPARATOR = | ||
| new UncompressedOldEntrySizeComparator(); | ||
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| /** | ||
| * Create a new limiter that will restrict the total size of the delta-friendly old blob. | ||
| * | ||
| * @param maxSizeBytes the maximum size of the delta-friendly old blob | ||
| */ | ||
| public DeltaFriendlyOldBlobSizeLimiter(long maxSizeBytes) { | ||
| if (maxSizeBytes < 0) { | ||
| throw new IllegalArgumentException("maxSizeBytes must be non-negative: " + maxSizeBytes); | ||
| } | ||
| this.maxSizeBytes = maxSizeBytes; | ||
| } | ||
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| @Override | ||
| public List<QualifiedRecommendation> getModifiedRecommendations( | ||
| File oldFile, File newFile, List<QualifiedRecommendation> originalRecommendations) { | ||
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| List<QualifiedRecommendation> sorted = sortRecommendations(originalRecommendations); | ||
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| List<QualifiedRecommendation> result = new ArrayList<>(sorted.size()); | ||
| long bytesRemaining = maxSizeBytes - oldFile.length(); | ||
| for (QualifiedRecommendation originalRecommendation : sorted) { | ||
| if (!originalRecommendation.getRecommendation().uncompressOldEntry) { | ||
| // Keep the original recommendation, no need to track size since it won't be uncompressed. | ||
| result.add(originalRecommendation); | ||
| } else { | ||
| long extraBytesConsumed = | ||
| originalRecommendation.getOldEntry().getUncompressedSize() | ||
| - originalRecommendation.getOldEntry().getCompressedSize(); | ||
| if (bytesRemaining - extraBytesConsumed >= 0) { | ||
| // Keep the original recommendation, but also subtract from the remaining space. | ||
| result.add(originalRecommendation); | ||
| bytesRemaining -= extraBytesConsumed; | ||
| } else { | ||
| // Update the recommendation to prevent uncompressing this tuple. | ||
| result.add( | ||
| new QualifiedRecommendation( | ||
| originalRecommendation.getOldEntry(), | ||
| originalRecommendation.getNewEntry(), | ||
| Recommendation.UNCOMPRESS_NEITHER, | ||
| RecommendationReason.RESOURCE_CONSTRAINED)); | ||
| } | ||
| } | ||
| } | ||
| return result; | ||
| } | ||
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| private static List<QualifiedRecommendation> sortRecommendations( | ||
| List<QualifiedRecommendation> originalRecommendations) { | ||
| List<QualifiedRecommendation> sorted = | ||
| new ArrayList<QualifiedRecommendation>(originalRecommendations); | ||
| Collections.sort(sorted, COMPARATOR); | ||
| Collections.reverse(sorted); | ||
| return sorted; | ||
| } | ||
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| /** Helper class implementing the sort order described in the class documentation. */ | ||
| private static class UncompressedOldEntrySizeComparator | ||
| implements Comparator<QualifiedRecommendation> { | ||
| @Override | ||
| public int compare(QualifiedRecommendation qr1, QualifiedRecommendation qr2) { | ||
| return Long.compare( | ||
| qr1.getOldEntry().getUncompressedSize(), qr2.getOldEntry().getUncompressedSize()); | ||
| } | ||
| } | ||
| } |
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