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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.
package com.google.archivepatcher.applier;
import com.google.archivepatcher.applier.bsdiff.BsDiffDeltaApplier;
import com.google.archivepatcher.shared.DeltaFriendlyFile;
import com.google.archivepatcher.shared.RandomAccessFileOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* Applies V1 patches.
*/
public class FileByFileV1DeltaApplier implements DeltaApplier {
/**
* Default size of the buffer to use for copying bytes in the recompression stream.
*/
private static final int DEFAULT_COPY_BUFFER_SIZE = 32768;
/**
* The temp directory to use.
*/
private final File tempDir;
/**
* Creates a new delta applier that will use the specified temp directory.
* @param tempDir a temp directory where the delta-friendly old blob can be written during the
* patch application process
*/
public FileByFileV1DeltaApplier(File tempDir) {
this.tempDir = tempDir;
}
@Override
public void applyDelta(File oldBlob, InputStream deltaIn, OutputStream newBlobOut)
throws IOException {
if (!tempDir.exists()) {
// Be nice, try to create the temp directory. Don't bother to check return value as the code
// will fail when it tries to create the file in a few more lines anyways.
tempDir.mkdirs();
}
File tempFile = File.createTempFile("gfbfv1", "old", tempDir);
try {
applyDeltaInternal(oldBlob, tempFile, deltaIn, newBlobOut);
} finally {
tempFile.delete();
}
}
/**
* Does the work for applying a delta.
* @param oldBlob the old blob
* @param deltaFriendlyOldBlob the location in which to store the delta-friendly old blob
* @param deltaIn the patch stream
* @param newBlobOut the stream to write the new blob to after applying the delta
* @throws IOException if anything goes wrong
*/
private void applyDeltaInternal(
File oldBlob, File deltaFriendlyOldBlob, InputStream deltaIn, OutputStream newBlobOut)
throws IOException {
// First, read the patch plan from the patch stream.
PatchReader patchReader = new PatchReader();
PatchApplyPlan plan = patchReader.readPatchApplyPlan(deltaIn);
writeDeltaFriendlyOldBlob(plan, oldBlob, deltaFriendlyOldBlob);
// Apply the delta. In v1 there is always exactly one delta descriptor, it is bsdiff, and it
// takes up the rest of the patch stream - so there is no need to examine the list of
// DeltaDescriptors in the patch at all.
long deltaLength = plan.getDeltaDescriptors().get(0).getDeltaLength();
DeltaApplier deltaApplier = getDeltaApplier();
// Don't close this stream, as it is just a limiting wrapper.
@SuppressWarnings("resource")
LimitedInputStream limitedDeltaIn = new LimitedInputStream(deltaIn, deltaLength);
// Don't close this stream, as it would close the underlying OutputStream (that we don't own).
@SuppressWarnings("resource")
PartiallyCompressingOutputStream recompressingNewBlobOut =
new PartiallyCompressingOutputStream(
plan.getDeltaFriendlyNewFileRecompressionPlan(),
newBlobOut,
DEFAULT_COPY_BUFFER_SIZE);
deltaApplier.applyDelta(deltaFriendlyOldBlob, limitedDeltaIn, recompressingNewBlobOut);
recompressingNewBlobOut.flush();
}
/**
* Writes the delta-friendly old blob to temporary storage.
* @param plan the plan to use for uncompressing
* @param oldBlob the blob to turn into a delta-friendly blob
* @param deltaFriendlyOldBlob where to write the blob
* @throws IOException if anything goes wrong
*/
private void writeDeltaFriendlyOldBlob(
PatchApplyPlan plan, File oldBlob, File deltaFriendlyOldBlob) throws IOException {
RandomAccessFileOutputStream deltaFriendlyOldFileOut = null;
try {
deltaFriendlyOldFileOut =
new RandomAccessFileOutputStream(
deltaFriendlyOldBlob, plan.getDeltaFriendlyOldFileSize());
DeltaFriendlyFile.generateDeltaFriendlyFile(
plan.getOldFileUncompressionPlan(),
oldBlob,
deltaFriendlyOldFileOut,
false,
DEFAULT_COPY_BUFFER_SIZE);
} finally {
try {
deltaFriendlyOldFileOut.close();
} catch (Exception ignored) {
// Nothing
}
}
}
/**
* Return an instance of a {@link DeltaApplier} suitable for applying the deltas within the patch
* stream.
* @return the applier
*/
// Visible for testing only
protected DeltaApplier getDeltaApplier() {
return new BsDiffDeltaApplier();
}
}
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