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/*
* Copyright (C) 2010 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 libcore.io;
import android.system.ErrnoException;
import java.io.FileDescriptor;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteOrder;
import java.nio.channels.FileChannel;
import java.nio.NioUtils;
import libcore.io.Libcore;
import libcore.io.Memory;
import static android.system.OsConstants.*;
/**
* A memory-mapped file. Use {@link #mmap} to map a file, {@link #close} to unmap a file,
* and either {@link #bigEndianIterator} or {@link #littleEndianIterator} to get a seekable
* {@link BufferIterator} over the mapped data.
*/
public final class MemoryMappedFile implements AutoCloseable {
private long address;
private final long size;
/**
* Use this if you've called {@code mmap} yourself.
*/
public MemoryMappedFile(long address, long size) {
this.address = address;
this.size = size;
}
/**
* Use this to mmap the whole file read-only.
*/
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
long size = Libcore.os.fstat(fd).st_size;
long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
Libcore.os.close(fd);
return new MemoryMappedFile(address, size);
}
/**
* Unmaps this memory-mapped file using munmap(2). This is a no-op if close has already been
* called. Note that this class does <i>not</i> use finalization; you must call {@code close}
* yourself.
*
* Calling this method invalidates any iterators over this {@code MemoryMappedFile}. It is an
* error to use such an iterator after calling {@code close}.
*/
public synchronized void close() throws ErrnoException {
if (address != 0) {
Libcore.os.munmap(address, size);
address = 0;
}
}
/**
* Returns a new iterator that treats the mapped data as big-endian.
*/
public BufferIterator bigEndianIterator() {
return new NioBufferIterator(address, (int) size, ByteOrder.nativeOrder() != ByteOrder.BIG_ENDIAN);
}
/**
* Returns a new iterator that treats the mapped data as little-endian.
*/
public BufferIterator littleEndianIterator() {
return new NioBufferIterator(address, (int) size, ByteOrder.nativeOrder() != ByteOrder.LITTLE_ENDIAN);
}
/**
* Returns the size in bytes of the memory-mapped region.
*/
public long size() {
return size;
}
}
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