102 lines
3.0 KiB
Java
102 lines
3.0 KiB
Java
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/*
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* Copyright (C) 2009 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.server;
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import android.util.Slog;
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import java.io.Closeable;
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import java.io.DataOutput;
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import java.io.EOFException;
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import java.io.FileInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.RandomAccessFile;
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/**
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* A 4k block of random {@code byte}s.
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*/
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class RandomBlock {
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private static final String TAG = "RandomBlock";
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private static final boolean DEBUG = false;
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private static final int BLOCK_SIZE = 4096;
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private byte[] block = new byte[BLOCK_SIZE];
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private RandomBlock() { }
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static RandomBlock fromFile(String filename) throws IOException {
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if (DEBUG) Slog.v(TAG, "reading from file " + filename);
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InputStream stream = null;
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try {
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stream = new FileInputStream(filename);
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return fromStream(stream);
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} finally {
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close(stream);
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}
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}
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private static RandomBlock fromStream(InputStream in) throws IOException {
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RandomBlock retval = new RandomBlock();
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int total = 0;
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while(total < BLOCK_SIZE) {
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int result = in.read(retval.block, total, BLOCK_SIZE - total);
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if (result == -1) {
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throw new EOFException();
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}
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total += result;
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}
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return retval;
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}
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void toFile(String filename) throws IOException {
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if (DEBUG) Slog.v(TAG, "writing to file " + filename);
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RandomAccessFile out = null;
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try {
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out = new RandomAccessFile(filename, "rws");
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toDataOut(out);
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truncateIfPossible(out);
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} finally {
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close(out);
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}
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}
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private static void truncateIfPossible(RandomAccessFile f) {
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try {
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f.setLength(BLOCK_SIZE);
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} catch (IOException e) {
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// ignore this exception. Sometimes, the file we're trying to
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// write is a character device, such as /dev/urandom, and
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// these character devices do not support setting the length.
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}
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}
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private void toDataOut(DataOutput out) throws IOException {
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out.write(block);
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}
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private static void close(Closeable c) {
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try {
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if (c == null) {
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return;
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}
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c.close();
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} catch (IOException e) {
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Slog.w(TAG, "IOException thrown while closing Closeable", e);
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}
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}
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}
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