1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package libcore.io; 18 19 import java.io.FileDescriptor; 20 import java.io.IOException; 21 import java.io.RandomAccessFile; 22 import java.nio.ByteOrder; 23 import java.nio.NioUtils; 24 import java.nio.channels.FileChannel; 25 import libcore.io.ErrnoException; 26 import libcore.io.Libcore; 27 import libcore.io.Memory; 28 import static libcore.io.OsConstants.*; 29 30 /** 31 * A memory-mapped file. Use {@link #mmap} to map a file, {@link #close} to unmap a file, 32 * and either {@link #bigEndianIterator} or {@link #littleEndianIterator} to get a seekable 33 * {@link BufferIterator} over the mapped data. 34 */ 35 public final class MemoryMappedFile implements AutoCloseable { 36 private long address; 37 private final long size; 38 39 /** 40 * Use this if you've called {@code mmap} yourself. 41 */ 42 public MemoryMappedFile(long address, long size) { 43 this.address = address; 44 this.size = size; 45 } 46 47 /** 48 * Use this to mmap the whole file read-only. 49 */ 50 public static MemoryMappedFile mmapRO(String path) throws ErrnoException { 51 FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0); 52 long size = Libcore.os.fstat(fd).st_size; 53 long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0); 54 Libcore.os.close(fd); 55 return new MemoryMappedFile(address, size); 56 } 57 58 /** 59 * Unmaps this memory-mapped file using munmap(2). This is a no-op if close has already been 60 * called. Note that this class does <i>not</i> use finalization; you must call {@code close} 61 * yourself. 62 * 63 * Calling this method invalidates any iterators over this {@code MemoryMappedFile}. It is an 64 * error to use such an iterator after calling {@code close}. 65 */ 66 public synchronized void close() throws ErrnoException { 67 if (address != 0) { 68 Libcore.os.munmap(address, size); 69 address = 0; 70 } 71 } 72 73 /** 74 * Returns a new iterator that treats the mapped data as big-endian. 75 */ 76 public BufferIterator bigEndianIterator() { 77 return new NioBufferIterator(address, (int) size, ByteOrder.nativeOrder() != ByteOrder.BIG_ENDIAN); 78 } 79 80 /** 81 * Returns a new iterator that treats the mapped data as little-endian. 82 */ 83 public BufferIterator littleEndianIterator() { 84 return new NioBufferIterator(address, (int) size, ByteOrder.nativeOrder() != ByteOrder.LITTLE_ENDIAN); 85 } 86 87 /** 88 * Returns the size in bytes of the memory-mapped region. 89 */ 90 public long size() { 91 return size; 92 } 93 } 94
