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      1 /*
      2  * Copyright (C) 2012 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 android.content.pm;
     18 
     19 import android.os.Parcel;
     20 import android.os.Parcelable;
     21 import android.util.Slog;
     22 
     23 import java.io.BufferedInputStream;
     24 import java.io.IOException;
     25 import java.io.InputStream;
     26 import java.security.DigestInputStream;
     27 import java.security.MessageDigest;
     28 import java.security.NoSuchAlgorithmException;
     29 import java.util.Arrays;
     30 
     31 import libcore.io.IoUtils;
     32 
     33 /**
     34  * Represents the manifest digest for a package. This is suitable for comparison
     35  * of two packages to know whether the manifests are identical.
     36  *
     37  * @hide
     38  */
     39 public class ManifestDigest implements Parcelable {
     40     private static final String TAG = "ManifestDigest";
     41 
     42     /** The digest of the manifest in our preferred order. */
     43     private final byte[] mDigest;
     44 
     45     /** What we print out first when toString() is called. */
     46     private static final String TO_STRING_PREFIX = "ManifestDigest {mDigest=";
     47 
     48     /** Digest algorithm to use. */
     49     private static final String DIGEST_ALGORITHM = "SHA-256";
     50 
     51     ManifestDigest(byte[] digest) {
     52         mDigest = digest;
     53     }
     54 
     55     private ManifestDigest(Parcel source) {
     56         mDigest = source.createByteArray();
     57     }
     58 
     59     static ManifestDigest fromInputStream(InputStream fileIs) {
     60         if (fileIs == null) {
     61             return null;
     62         }
     63 
     64         final MessageDigest md;
     65         try {
     66             md = MessageDigest.getInstance(DIGEST_ALGORITHM);
     67         } catch (NoSuchAlgorithmException e) {
     68             throw new RuntimeException(DIGEST_ALGORITHM + " must be available", e);
     69         }
     70 
     71         final DigestInputStream dis = new DigestInputStream(new BufferedInputStream(fileIs), md);
     72         try {
     73             byte[] readBuffer = new byte[8192];
     74             while (dis.read(readBuffer, 0, readBuffer.length) != -1) {
     75                 // not using
     76             }
     77         } catch (IOException e) {
     78             Slog.w(TAG, "Could not read manifest");
     79             return null;
     80         } finally {
     81             IoUtils.closeQuietly(dis);
     82         }
     83 
     84         final byte[] digest = md.digest();
     85         return new ManifestDigest(digest);
     86     }
     87 
     88     @Override
     89     public int describeContents() {
     90         return 0;
     91     }
     92 
     93     @Override
     94     public boolean equals(Object o) {
     95         if (!(o instanceof ManifestDigest)) {
     96             return false;
     97         }
     98 
     99         final ManifestDigest other = (ManifestDigest) o;
    100 
    101         return this == other || Arrays.equals(mDigest, other.mDigest);
    102     }
    103 
    104     @Override
    105     public int hashCode() {
    106         return Arrays.hashCode(mDigest);
    107     }
    108 
    109     @Override
    110     public String toString() {
    111         final StringBuilder sb = new StringBuilder(TO_STRING_PREFIX.length()
    112                 + (mDigest.length * 3) + 1);
    113 
    114         sb.append(TO_STRING_PREFIX);
    115 
    116         final int N = mDigest.length;
    117         for (int i = 0; i < N; i++) {
    118             final byte b = mDigest[i];
    119             IntegralToString.appendByteAsHex(sb, b, false);
    120             sb.append(',');
    121         }
    122         sb.append('}');
    123 
    124         return sb.toString();
    125     }
    126 
    127     @Override
    128     public void writeToParcel(Parcel dest, int flags) {
    129         dest.writeByteArray(mDigest);
    130     }
    131 
    132     public static final Parcelable.Creator<ManifestDigest> CREATOR
    133             = new Parcelable.Creator<ManifestDigest>() {
    134         public ManifestDigest createFromParcel(Parcel source) {
    135             return new ManifestDigest(source);
    136         }
    137 
    138         public ManifestDigest[] newArray(int size) {
    139             return new ManifestDigest[size];
    140         }
    141     };
    142 
    143 }