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/*
* Copyright (C) 2009 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 com.android.server;
import android.util.Slog;
import java.io.Closeable;
import java.io.DataOutput;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
/**
* A block of 512 random {@code byte}s.
*/
class RandomBlock {
private static final String TAG = "RandomBlock";
private static final boolean DEBUG = false;
private static final int BLOCK_SIZE = 512;
private byte[] block = new byte[BLOCK_SIZE];
private RandomBlock() { }
static RandomBlock fromFile(String filename) throws IOException {
if (DEBUG) Slog.v(TAG, "reading from file " + filename);
InputStream stream = null;
try {
stream = new FileInputStream(filename);
return fromStream(stream);
} finally {
close(stream);
}
}
private static RandomBlock fromStream(InputStream in) throws IOException {
RandomBlock retval = new RandomBlock();
int total = 0;
while(total < BLOCK_SIZE) {
int result = in.read(retval.block, total, BLOCK_SIZE - total);
if (result == -1) {
throw new EOFException();
}
total += result;
}
return retval;
}
void toFile(String filename, boolean sync) throws IOException {
if (DEBUG) Slog.v(TAG, "writing to file " + filename);
RandomAccessFile out = null;
try {
out = new RandomAccessFile(filename, sync ? "rws" : "rw");
toDataOut(out);
truncateIfPossible(out);
} finally {
close(out);
}
}
private static void truncateIfPossible(RandomAccessFile f) {
try {
f.setLength(BLOCK_SIZE);
} catch (IOException e) {
// ignore this exception. Sometimes, the file we're trying to
// write is a character device, such as /dev/urandom, and
// these character devices do not support setting the length.
}
}
private void toDataOut(DataOutput out) throws IOException {
out.write(block);
}
private static void close(Closeable c) {
try {
if (c == null) {
return;
}
c.close();
} catch (IOException e) {
Slog.w(TAG, "IOException thrown while closing Closeable", e);
}
}
}
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