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/*
* Copyright (C) 2021 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 android.util.apk;
import android.system.ErrnoException;
import android.system.Os;
import java.io.FileDescriptor;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.security.DigestException;
/**
* {@link DataSource} which provides data from a file descriptor by reading the sections
* of the file via raw read() syscall. This is slower than memory-mapping but safer.
*/
class ReadFileDataSource implements DataSource {
private final FileDescriptor mFd;
private final long mFilePosition;
private final long mSize;
private static final int CHUNK_SIZE = 1024 * 1024;
/**
* Constructs a new {@code ReadFileDataSource} for the specified region of the file.
*
* @param fd file descriptor to read from.
* @param position start position of the region in the file.
* @param size size (in bytes) of the region.
*/
ReadFileDataSource(FileDescriptor fd, long position, long size) {
mFd = fd;
mFilePosition = position;
mSize = size;
}
@Override
public long size() {
return mSize;
}
@Override
public void feedIntoDataDigester(DataDigester md, long offset, int size)
throws IOException, DigestException {
try {
final byte[] buffer = new byte[Math.min(size, CHUNK_SIZE)];
final long start = mFilePosition + offset;
final long end = start + size;
for (long pos = start, curSize = Math.min(size, CHUNK_SIZE);
pos < end; curSize = Math.min(end - pos, CHUNK_SIZE)) {
final int readSize = Os.pread(mFd, buffer, 0, (int) curSize, pos);
md.consume(ByteBuffer.wrap(buffer, 0, readSize));
pos += readSize;
}
} catch (ErrnoException e) {
throw new IOException(e);
}
}
}
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