67 lines
2.4 KiB
Java
67 lines
2.4 KiB
Java
|
/*
|
||
|
|
* 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 java.io.IOException;
|
||
|
|
import java.nio.ByteBuffer;
|
||
|
|
import java.security.DigestException;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* {@link DataSource} which provides data from a {@link ByteBuffer}.
|
||
|
|
*/
|
||
|
|
class ByteBufferDataSource implements DataSource {
|
||
|
|
/**
|
||
|
|
* Underlying buffer. The data is stored between position 0 and the buffer's capacity.
|
||
|
|
* The buffer's position is 0 and limit is equal to capacity.
|
||
|
|
*/
|
||
|
|
private final ByteBuffer mBuf;
|
||
|
|
|
||
|
|
ByteBufferDataSource(ByteBuffer buf) {
|
||
|
|
// Defensive copy, to avoid changes to mBuf being visible in buf, and to ensure position is
|
||
|
|
// 0 and limit == capacity.
|
||
|
|
mBuf = buf.slice();
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public long size() {
|
||
|
|
return mBuf.capacity();
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public void feedIntoDataDigester(DataDigester md, long offset, int size)
|
||
|
|
throws IOException, DigestException {
|
||
|
|
// There's no way to tell MessageDigest to read data from ByteBuffer from a position
|
||
|
|
// other than the buffer's current position. We thus need to change the buffer's
|
||
|
|
// position to match the requested offset.
|
||
|
|
//
|
||
|
|
// In the future, it may be necessary to compute digests of multiple regions in
|
||
|
|
// parallel. Given that digest computation is a slow operation, we enable multiple
|
||
|
|
// such requests to be fulfilled by this instance. This is achieved by serially
|
||
|
|
// creating a new ByteBuffer corresponding to the requested data range and then,
|
||
|
|
// potentially concurrently, feeding these buffers into MessageDigest instances.
|
||
|
|
ByteBuffer region;
|
||
|
|
synchronized (mBuf) {
|
||
|
|
mBuf.position(0);
|
||
|
|
mBuf.limit((int) offset + size);
|
||
|
|
mBuf.position((int) offset);
|
||
|
|
region = mBuf.slice();
|
||
|
|
}
|
||
|
|
|
||
|
|
md.consume(region);
|
||
|
|
}
|
||
|
|
}
|