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      1 /*
      2  * Copyright 2013, Google Inc.
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are
      7  * met:
      8  *
      9  *     * Redistributions of source code must retain the above copyright
     10  * notice, this list of conditions and the following disclaimer.
     11  *     * Redistributions in binary form must reproduce the above
     12  * copyright notice, this list of conditions and the following disclaimer
     13  * in the documentation and/or other materials provided with the
     14  * distribution.
     15  *     * Neither the name of Google Inc. nor the names of its
     16  * contributors may be used to endorse or promote products derived from
     17  * this software without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     22  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     23  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 package org.jf.dexlib2.dexbacked.raw;
     33 
     34 import org.jf.dexlib2.dexbacked.BaseDexBuffer;
     35 
     36 public class OdexHeaderItem {
     37     public static final int ITEM_SIZE = 40;
     38 
     39     private static final byte[] MAGIC_VALUE = new byte[] { 0x64, 0x65, 0x79, 0x0A, 0x00, 0x00, 0x00, 0x00 };
     40     private static final int[] SUPPORTED_ODEX_VERSIONS = new int[] { 35, 36 };
     41 
     42     public static final int MAGIC_OFFSET = 0;
     43     public static final int MAGIC_LENGTH = 8;
     44     public static final int DEX_OFFSET = 8;
     45     public static final int DEX_LENGTH_OFFSET = 12;
     46     public static final int DEPENDENCIES_OFFSET = 16;
     47     public static final int DEPENDENCIES_LENGTH_OFFSET = 20;
     48     public static final int AUX_OFFSET = 24;
     49     public static final int AUX_LENGTH_OFFSET = 28;
     50     public static final int FLAGS_OFFSET = 32;
     51 
     52     /**
     53      * Verifies the magic value at the beginning of an odex file
     54      *
     55      * @param buf A byte array containing at least the first 8 bytes of an odex file
     56      * @param offset The offset within the buffer to the beginning of the odex header
     57      * @return True if the magic value is valid
     58      */
     59     public static boolean verifyMagic(byte[] buf, int offset) {
     60         if (buf.length - offset < 8) {
     61             return false;
     62         }
     63 
     64         for (int i=0; i<4; i++) {
     65             if (buf[offset + i] != MAGIC_VALUE[i]) {
     66                 return false;
     67             }
     68         }
     69         for (int i=4; i<7; i++) {
     70             if (buf[offset + i] < '0' ||
     71                     buf[offset + i] > '9') {
     72                 return false;
     73             }
     74         }
     75         if (buf[offset + 7] != MAGIC_VALUE[7]) {
     76             return false;
     77         }
     78 
     79         return true;
     80     }
     81 
     82     /**
     83      * Gets the dex version from an odex header
     84      *
     85      * @param buf A byte array containing at least the first 7 bytes of an odex file
     86      * @param offset The offset within the buffer to the beginning of the odex header
     87      * @return The odex version if the header is valid or -1 if the header is invalid
     88      */
     89     public static int getVersion(byte[] buf, int offset) {
     90         if (!verifyMagic(buf, offset)) {
     91             return -1;
     92         }
     93 
     94         return getVersionUnchecked(buf, offset);
     95     }
     96 
     97     private static int getVersionUnchecked(byte[] buf, int offset) {
     98         int version = (buf[offset + 4] - '0') * 100;
     99         version += (buf[offset + 5] - '0') * 10;
    100         version += buf[offset + 6] - '0';
    101 
    102         return version;
    103     }
    104 
    105     public static boolean isSupportedOdexVersion(int version) {
    106         for (int i=0; i<SUPPORTED_ODEX_VERSIONS.length; i++) {
    107             if (SUPPORTED_ODEX_VERSIONS[i] == version) {
    108                 return true;
    109             }
    110         }
    111         return false;
    112     }
    113 
    114     public static int getDexOffset(byte[] buf) {
    115         BaseDexBuffer bdb = new BaseDexBuffer(buf);
    116         return bdb.readSmallUint(DEX_OFFSET);
    117     }
    118 
    119     public static int getDependenciesOffset(byte[] buf) {
    120         BaseDexBuffer bdb = new BaseDexBuffer(buf);
    121         return bdb.readSmallUint(DEPENDENCIES_OFFSET);
    122     }
    123 }
    124