1 /* 2 * Copyright (C) 2016 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 com.android.documentsui.archives; 18 19 import android.os.ProxyFileDescriptorCallback; 20 import android.system.ErrnoException; 21 import android.system.OsConstants; 22 import android.util.Log; 23 import android.util.jar.StrictJarFile; 24 25 import java.io.IOException; 26 import java.io.InputStream; 27 import java.util.zip.ZipEntry; 28 29 import libcore.io.IoUtils; 30 31 /** 32 * Provides a backend for a seekable file descriptors for files in archives. 33 */ 34 public class Proxy extends ProxyFileDescriptorCallback { 35 private final StrictJarFile mFile; 36 private final ZipEntry mEntry; 37 private InputStream mInputStream = null; 38 private long mOffset = 0; 39 Proxy(StrictJarFile file, ZipEntry entry)40 Proxy(StrictJarFile file, ZipEntry entry) throws IOException { 41 mFile = file; 42 mEntry = entry; 43 recreateInputStream(); 44 } 45 46 @Override onGetSize()47 public long onGetSize() throws ErrnoException { 48 return mEntry.getSize(); 49 } 50 51 @Override onRead(long offset, int size, byte[] data)52 public int onRead(long offset, int size, byte[] data) throws ErrnoException { 53 // TODO: Add a ring buffer to prevent expensive seeks. 54 if (offset < mOffset) { 55 try { 56 recreateInputStream(); 57 } catch (IOException e) { 58 throw new ErrnoException("onRead", OsConstants.EIO); 59 } 60 } 61 62 while (mOffset < offset) { 63 try { 64 mOffset += mInputStream.skip(offset - mOffset); 65 } catch (IOException e) { 66 throw new ErrnoException("onRead", OsConstants.EIO); 67 } 68 } 69 70 int remainingSize = size; 71 while (remainingSize > 0) { 72 try { 73 int bytes = mInputStream.read(data, size - remainingSize, remainingSize); 74 if (bytes <= 0) { 75 return size - remainingSize; 76 } 77 remainingSize -= bytes; 78 mOffset += bytes; 79 } catch (IOException e) { 80 throw new ErrnoException("onRead", OsConstants.EIO); 81 } 82 } 83 84 return size - remainingSize; 85 } 86 onRelease()87 @Override public void onRelease() { 88 IoUtils.closeQuietly(mInputStream); 89 } 90 recreateInputStream()91 private void recreateInputStream() throws IOException { 92 IoUtils.closeQuietly(mInputStream); 93 mInputStream = mFile.getInputStream(mEntry); 94 mOffset = 0; 95 } 96 } 97