| /* |
| * Copyright (C) 2011 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 com.android.dx.io; |
| |
| import java.io.IOException; |
| import java.security.MessageDigest; |
| import java.security.NoSuchAlgorithmException; |
| import java.util.zip.Adler32; |
| |
| /** |
| * Generates and stores the checksum and signature of a dex file. |
| */ |
| public final class DexHasher { |
| private static final int CHECKSUM_OFFSET = 8; |
| private static final int CHECKSUM_SIZE = 4; |
| private static final int SIGNATURE_OFFSET = CHECKSUM_OFFSET + CHECKSUM_SIZE; |
| private static final int SIGNATURE_SIZE = 20; |
| |
| /** |
| * Returns the signature of all but the first 32 bytes of {@code dex}. The |
| * first 32 bytes of dex files are not specified to be included in the |
| * signature. |
| */ |
| public byte[] computeSignature(DexBuffer dex) throws IOException { |
| MessageDigest digest; |
| try { |
| digest = MessageDigest.getInstance("SHA-1"); |
| } catch (NoSuchAlgorithmException e) { |
| throw new AssertionError(); |
| } |
| int offset = SIGNATURE_OFFSET + SIGNATURE_SIZE; |
| |
| byte[] bytes = dex.getBytes(); |
| digest.update(bytes, offset, bytes.length - offset); |
| return digest.digest(); |
| } |
| |
| /** |
| * Returns the checksum of all but the first 12 bytes of {@code dex}. |
| */ |
| public int computeChecksum(DexBuffer dex) throws IOException { |
| Adler32 adler32 = new Adler32(); |
| int offset = CHECKSUM_OFFSET + CHECKSUM_SIZE; |
| |
| byte[] bytes = dex.getBytes(); |
| adler32.update(bytes, offset, bytes.length - offset); |
| return (int) adler32.getValue(); |
| } |
| |
| /** |
| * Generates the signature and checksum of the dex file {@code out} and |
| * writes them to the file. |
| */ |
| public void writeHashes(DexBuffer dex) throws IOException { |
| byte[] signature = computeSignature(dex); |
| dex.open(SIGNATURE_OFFSET).write(signature); |
| |
| int checksum = computeChecksum(dex); |
| dex.open(CHECKSUM_OFFSET).writeInt(checksum); |
| } |
| } |