Home | History | Annotate | Download | only in vogar 
      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 vogar;
     18 
     19 import com.google.common.base.Charsets;
     20 
     21 import java.io.File;
     22 import java.io.FileInputStream;
     23 import java.security.MessageDigest;
     24 
     25 /**
     26  * Caches content by MD5.
     27  */
     28 public final class Md5Cache {
     29 
     30     private final Log log;
     31     private final String keyPrefix;
     32     private final FileCache fileCache;
     33 
     34     /**
     35      * Creates a new cache accessor. There's only one directory on disk, so 'keyPrefix' is really
     36      * just a convenience for humans inspecting the cache.
     37      */
     38     public Md5Cache(Log log, String keyPrefix, FileCache fileCache) {
     39         this.log = log;
     40         this.keyPrefix = keyPrefix;
     41         this.fileCache = fileCache;
     42     }
     43 
     44     public boolean getFromCache(File output, String key) {
     45         if (fileCache.existsInCache(key)) {
     46             fileCache.copyFromCache(key, output);
     47             return true;
     48         }
     49         return false;
     50     }
     51 
     52     /**
     53      * Returns an ASCII hex representation of the MD5 of the content of 'file'.
     54      */
     55     private static String md5(File file) {
     56         byte[] digest = null;
     57         try {
     58             MessageDigest digester = MessageDigest.getInstance("MD5");
     59             byte[] bytes = new byte[8192];
     60             FileInputStream in = new FileInputStream(file);
     61             try {
     62                 int byteCount;
     63                 while ((byteCount = in.read(bytes)) > 0) {
     64                     digester.update(bytes, 0, byteCount);
     65                 }
     66                 digest = digester.digest();
     67             } finally {
     68                 in.close();
     69             }
     70         } catch (Exception cause) {
     71             throw new RuntimeException("Unable to compute MD5 of \"" + file + "\"", cause);
     72         }
     73         return (digest == null) ? null : byteArrayToHexString(digest);
     74     }
     75 
     76     /**
     77      * Returns an ASCII hex representation of the MD5 of 'string'.
     78      */
     79     private static String md5(String string) {
     80         byte[] digest;
     81         try {
     82             MessageDigest digester = MessageDigest.getInstance("MD5");
     83             digester.update(string.getBytes(Charsets.UTF_8));
     84             digest = digester.digest();
     85         } catch (Exception cause) {
     86             throw new RuntimeException("Unable to compute MD5 of \"" + string + "\"", cause);
     87         }
     88         return (digest == null) ? null : byteArrayToHexString(digest);
     89     }
     90 
     91     private static String byteArrayToHexString(byte[] bytes) {
     92         StringBuilder result = new StringBuilder();
     93         for (byte b : bytes) {
     94             result.append(Integer.toHexString((b >> 4) & 0xf));
     95             result.append(Integer.toHexString(b & 0xf));
     96         }
     97         return result.toString();
     98     }
     99 
    100     /**
    101      * Returns the appropriate key for a dex file corresponding to the contents of 'classpath'.
    102      * Returns null if we don't think it's possible to cache the given classpath.
    103      */
    104     public String makeKey(Classpath classpath) {
    105         // Do we have it in cache?
    106         String key = keyPrefix;
    107         for (File element : classpath.getElements()) {
    108             // We only cache dexed .jar/.jack files, not directories.
    109             String fileName = element.getName();
    110             if (!fileName.endsWith(".jar") && !fileName.endsWith(".jack")) {
    111                 return null;
    112             }
    113             key += "-" + md5(element);
    114         }
    115         return key;
    116     }
    117 
    118     /**
    119      * Returns a key corresponding to the MD5ed contents of {@code file}.
    120      */
    121     public String makeKey(File file) {
    122         return keyPrefix + "-" + md5(file);
    123     }
    124 
    125     /**
    126      * Returns a key corresponding to the MD5ed contents of the element.
    127      */
    128     public String makeKey(String... elements) {
    129         StringBuilder sb = new StringBuilder();
    130         for (String element : elements) {
    131           sb.append(element);
    132           sb.append('|');
    133         }
    134         return keyPrefix + "-" + md5(sb.toString());
    135     }
    136 
    137     /**
    138      * Copy the file 'content' into the cache with the given 'key'.
    139      * This method assumes you're using the appropriate key for the content (and has no way to
    140      * check because the key is a function of the inputs that made the content, not the content
    141      * itself).
    142      * We accept a null so the caller doesn't have to pay attention to whether we think we can
    143      * cache the content or not.
    144      */
    145     public void insert(String key, File content) {
    146         if (key == null) {
    147             return;
    148         }
    149         log.verbose("inserting " + key);
    150         fileCache.copyToCache(content, key);
    151     }
    152 }
    153