CrunchCache.h

   1 //
   2 // Copyright 2011 The Android Open Source Project
   3 //
   4 // Cache manager for pre-processed PNG files.
   5 // Contains code for managing which PNG files get processed
   6 // at build time.
   7 //
   8
   9 #ifndef CRUNCHCACHE_H
  10 #define CRUNCHCACHE_H
  11
  12 #include <utils/KeyedVector.h>
  13 #include <utils/String8.h>
  14 #include "FileFinder.h"
  15 #include "CacheUpdater.h"
  16
  17 using namespace android;
  18
  19 /** CrunchCache
  20  *  This class is a cache manager which can pre-process PNG files and store
  21  *  them in a mirror-cache. It's capable of doing incremental updates to its
  22  *  cache.
  23  *
  24  *  Usage:
  25  *      Create an instance initialized with the root of the source tree, the
  26  *      root location to store the cache files, and an instance of a file finder.
  27  *      Then update the cache by calling crunch.
  28  */
  29 class CrunchCache {
  30 public:
  31     // Constructor
  32     CrunchCache(String8 sourcePath, String8 destPath, FileFinder* ff);
  33
  34     // Nobody should be calling the default constructor
  35     // So this space is intentionally left blank
  36
  37     // Default Copy Constructor and Destructor are fine
  38
  39     /** crunch is the workhorse of this class.
  40      * It goes through all the files found in the sourcePath and compares
  41      * them to the cached versions in the destPath. If the optional
  42      * argument forceOverwrite is set to true, then all source files are
  43      * re-crunched even if they have not been modified recently. Otherwise,
  44      * source files are only crunched when they needUpdating. Afterwards,
  45      * we delete any leftover files in the cache that are no longer present
  46      * in source.
  47      *
  48      * PRECONDITIONS:
  49      *      No setup besides construction is needed
  50      * POSTCONDITIONS:
  51      *      The cache is updated to fully reflect all changes in source.
  52      *      The function then returns the number of files changed in cache
  53      *      (counting deletions).
  54      */
  55     size_t crunch(CacheUpdater* cu, bool forceOverwrite=false);
  56
  57 private:
  58     /** loadFiles is a wrapper to the FileFinder that places matching
  59      * files into mSourceFiles and mDestFiles.
  60      *
  61      *  POSTCONDITIONS
  62      *      mDestFiles and mSourceFiles are refreshed to reflect the current
  63      *      state of the files in the source and dest directories.
  64      *      Any previous contents of mSourceFiles and mDestFiles are cleared.
  65      */
  66     void loadFiles();
  67
  68     /** needsUpdating takes a file path
  69      * and returns true if the file represented by this path is newer in the
  70      * sourceFiles than in the cache (mDestFiles).
  71      *
  72      * PRECONDITIONS:
  73      *      mSourceFiles and mDestFiles must be initialized and filled.
  74      * POSTCONDITIONS:
  75      *      returns true if and only if source file's modification time
  76      *      is greater than the cached file's mod-time. Otherwise returns false.
  77      *
  78      * USAGE:
  79      *      Should be used something like the following:
  80      *      if (needsUpdating(filePath))
  81      *          // Recrunch sourceFile out to destFile.
  82      *
  83      */
  84     bool needsUpdating(String8 relativePath) const;
  85
  86     // DATA MEMBERS ====================================================
  87
  88     String8 mSourcePath;
  89     String8 mDestPath;
  90
  91     Vector<String8> mExtensions;
  92
  93     // Each vector of paths contains one entry per PNG file encountered.
  94     // Each entry consists of a path pointing to that PNG.
  95     DefaultKeyedVector<String8,time_t> mSourceFiles;
  96     DefaultKeyedVector<String8,time_t> mDestFiles;
  97
  98     // Pointer to a FileFinder to use
  99     FileFinder* mFileFinder;
 100 };
 101
 102 #endif // CRUNCHCACHE_H