1 2 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */ 3 4 /* 5 Sonic Visualiser 6 An audio file viewer and annotation editor. 7 Centre for Digital Music, Queen Mary, University of London. 8 This file copyright 2006 QMUL. 9 10 This program is free software; you can redistribute it and/or 11 modify it under the terms of the GNU General Public License as 12 published by the Free Software Foundation; either version 2 of the 13 License, or (at your option) any later version. See the file 14 COPYING included with this distribution for more information. 15 */ 16 17 #ifndef SV_STORAGE_ADVISER_H 18 #define SV_STORAGE_ADVISER_H 19 20 #include <cstdlib> 21 22 #include <QString> 23 24 /** 25 * A utility class designed to help decide whether to store cache data 26 * (for example FFT outputs) in memory or on disk in the TempDirectory. 27 * This is basically a compendium of simple rules of thumb. 28 */ 29 30 class StorageAdviser 31 { 32 public: 33 // pass to recommend() zero or more of these OR'd together 34 enum Criteria { 35 NoCriteria = 0, 36 SpeedCritical = 1, 37 PrecisionCritical = 2, 38 LongRetentionLikely = 4, 39 FrequentLookupLikely = 8 40 }; 41 42 // recommend() returns one or two of these OR'd together 43 enum Recommendation { 44 NoRecommendation = 0, 45 UseMemory = 1, // Disc is strongly contraindicated 46 PreferMemory = 2, // Either would do; memory probably better 47 PreferDisc = 4, // Either would do; disc probably better 48 UseDisc = 8, // Probably won't fit in memory 49 ConserveSpace = 16,// Whatever you choose, keep it compact 50 UseAsMuchAsYouLike = 32 // Take my advice and there'll be space for all 51 }; 52 53 /** 54 * Recommend where to store some data, given certain storage and 55 * recall criteria. The minimum size is the approximate amount of 56 * data in kilobytes that will be stored if the recommendation is 57 * to ConserveSpace; the maximum size is approximately the amount 58 * that will be used if UseAsMuchAsYouLike is returned. 59 * 60 * May throw InsufficientDiscSpace exception if there appears to 61 * be nowhere the minimum amount of data can be stored. 62 */ 63 static Recommendation recommend(Criteria criteria, 64 size_t minimumSize, 65 size_t maximumSize); 66 67 enum AllocationArea { 68 MemoryAllocation, 69 DiscAllocation 70 }; 71 72 /** 73 * Specify that we are planning to use a given amount of storage 74 * (in kilobytes), but haven't allocated it yet. 75 */ 76 static void notifyPlannedAllocation(AllocationArea area, size_t size); 77 78 /** 79 * Specify that we have now allocated, or abandoned the allocation 80 * of, the given amount (in kilobytes) of a storage area that was 81 * previously notified using notifyPlannedAllocation. 82 */ 83 static void notifyDoneAllocation(AllocationArea area, size_t size); 84 85 /** 86 * Force all subsequent recommendations to use the (perhaps 87 * partial) specification given here. If NoRecommendation given 88 * here, this will reset to the default free behaviour. 89 */ 90 static void setFixedRecommendation(Recommendation recommendation); 91 92 private: 93 static size_t m_discPlanned; 94 static size_t m_memoryPlanned; 95 static Recommendation m_baseRecommendation; 96 97 enum StorageStatus { 98 Unknown, 99 Insufficient, 100 Marginal, 101 Sufficient 102 }; 103 104 static QString criteriaToString(int); 105 static QString recommendationToString(int); 106 static QString storageStatusToString(StorageStatus); 107 }; 108 109 #endif 110 111