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package android.content.pm;
import libcore.util.ArrayUtils;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* A class that limits the amount of data that is read from an InputStream. When
* the specified length is reached, the stream returns an EOF even if the
* underlying stream still has more data.
*
* @hide
*/
public class LimitedLengthInputStream extends FilterInputStream {
/**
* The end of the stream where we don't want to allow more data to be read.
*/
private final long mEnd;
/**
* Current offset in the stream.
*/
private long mOffset;
/**
* @param in underlying stream to wrap
* @param offset offset into stream where data starts
* @param length length of data at offset
* @throws IOException if an error occurred with the underlying stream
*/
public LimitedLengthInputStream(InputStream in, long offset, long length) throws IOException {
super(in);
if (in == null) {
throw new IOException("in == null");
}
if (offset < 0) {
throw new IOException("offset < 0");
}
if (length < 0) {
throw new IOException("length < 0");
}
if (length > Long.MAX_VALUE - offset) {
throw new IOException("offset + length > Long.MAX_VALUE");
}
mEnd = offset + length;
skip(offset);
mOffset = offset;
}
@Override
public synchronized int read() throws IOException {
if (mOffset >= mEnd) {
return -1;
}
mOffset++;
return super.read();
}
@Override
public int read(byte[] buffer, int offset, int byteCount) throws IOException {
if (mOffset >= mEnd) {
return -1;
}
final int arrayLength = buffer.length;
ArrayUtils.throwsIfOutOfBounds(arrayLength, offset, byteCount);
if (mOffset > Long.MAX_VALUE - byteCount) {
throw new IOException("offset out of bounds: " + mOffset + " + " + byteCount);
}
if (mOffset + byteCount > mEnd) {
byteCount = (int) (mEnd - mOffset);
}
final int numRead = super.read(buffer, offset, byteCount);
mOffset += numRead;
return numRead;
}
@Override
public int read(byte[] buffer) throws IOException {
return read(buffer, 0, buffer.length);
}
}
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