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/*
* Copyright (C) 2016 The Android Open Source Project
*
* 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.android.apkzlib.sign.v2;
import com.android.apkzlib.zip.ZFile;
import com.google.common.base.Preconditions;
import java.io.IOException;
import java.security.MessageDigest;
import javax.annotation.Nonnull;
/**
* Contiguous section of {@link ZFile} which is fed into {@link MessageDigest} instances.
*/
public class ZFileDigestSource implements DigestSource {
private final ZFile mFile;
private final long mOffset;
private final long mSize;
/**
* Constructs a new {@code ZFileDigestSource} representing the section of the file starting
* at the provided {@code offset} and extending for the provided {@code size} number of bytes.
*/
public ZFileDigestSource(@Nonnull ZFile file, long offset, long size) {
Preconditions.checkArgument(offset >= 0, "offset: %s", offset);
Preconditions.checkArgument(size >= 0, "size: %s", size);
mFile = file;
mOffset = offset;
mSize = size;
}
@Override
public long size() {
return mSize;
}
@Override
public void feedDigests(long offset, int size, @Nonnull MessageDigest[] digests)
throws IOException {
Preconditions.checkArgument(offset >= 0, "offset: %s", offset);
Preconditions.checkArgument(size >= 0, "size: %s", size);
Preconditions.checkArgument(offset <= mSize, "offset: %s, file size: %s", offset, mSize);
long chunkStartOffset = mOffset + offset;
long availableSize = mSize - offset;
Preconditions.checkArgument(
size <= availableSize, "offset: %s, size: %s, file size: %s", offset, size, mSize);
byte[] chunk = new byte[size];
mFile.directFullyRead(chunkStartOffset, chunk);
for (MessageDigest md : digests) {
md.update(chunk);
}
}
}
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