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/*
* Copyright (C) 2017 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.annotation.NonNull;
import android.os.incremental.IncrementalManager;
import java.io.FileDescriptor;
import java.io.IOException;
import java.security.DigestException;
/** Source of data to be digested. */
interface DataSource {
/**
* Returns the size (in bytes) of the data offered by this source.
*/
long size();
/**
* Feeds the specified region of this source's data into the provided digester.
*
* @param offset offset of the region inside this data source.
* @param size size (in bytes) of the region.
*/
void feedIntoDataDigester(DataDigester md, long offset, int size)
throws IOException, DigestException;
/**
* Creates a DataSource that can handle the passed fd in the most efficient and safe manner.
* @param fd file descriptor to read from
* @param pos starting offset
* @param size size of the region
* @return created DataSource object
*/
static @NonNull DataSource create(@NonNull FileDescriptor fd, long pos, long size) {
if (IncrementalManager.isIncrementalFileFd(fd)) {
// IncFS-based files may have missing pages, and reading those via mmap() results
// in a SIGBUS signal. Java doesn't have a good way of catching it, ending up killing
// the process by default. Going back to read() is the safest option for these files.
return new ReadFileDataSource(fd, pos, size);
} else {
return new MemoryMappedFileDataSource(fd, pos, size);
}
}
}
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