CrunchCache.h revision 8a39da80b33691b0c82458c3b7727e13ff71277e 
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
17using 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 */
29class CrunchCache {
30public:
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
57private:
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
103