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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
/*
Sonic Visualiser
An audio file viewer and annotation editor.
Centre for Digital Music, Queen Mary, University of London.
This file copyright 2006 QMUL.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version. See the file
COPYING included with this distribution for more information.
*/
#ifndef SV_STORAGE_ADVISER_H
#define SV_STORAGE_ADVISER_H
#include <cstdlib>
#include <QString>
namespace sv {
/**
* A utility class designed to help decide whether to store cache data
* (for example FFT outputs) in memory or on disk in the TempDirectory.
* This is basically a compendium of simple rules of thumb.
*/
class StorageAdviser
{
public:
// pass to recommend() zero or more of these OR'd together
enum Criteria {
NoCriteria = 0,
SpeedCritical = 1,
PrecisionCritical = 2,
LongRetentionLikely = 4,
FrequentLookupLikely = 8
};
// recommend() returns one or two of these OR'd together
enum Recommendation {
NoRecommendation = 0,
UseMemory = 1, // Disc is strongly contraindicated
PreferMemory = 2, // Either would do; memory probably better
PreferDisc = 4, // Either would do; disc probably better
UseDisc = 8, // Probably won't fit in memory
ConserveSpace = 16,// Whatever you choose, keep it compact
UseAsMuchAsYouLike = 32 // Take my advice and there'll be space for all
};
/**
* Recommend where to store some data, given certain storage and
* recall criteria. The minimum size is the approximate amount of
* data in kilobytes that will be stored if the recommendation is
* to ConserveSpace; the maximum size is approximately the amount
* that will be used if UseAsMuchAsYouLike is returned.
*
* May throw InsufficientDiscSpace exception if there appears to
* be nowhere the minimum amount of data can be stored.
*/
static Recommendation recommend(Criteria criteria,
size_t minimumSize,
size_t maximumSize);
enum AllocationArea {
MemoryAllocation,
DiscAllocation
};
/**
* Specify that we are planning to use a given amount of storage
* (in kilobytes), but haven't allocated it yet.
*/
static void notifyPlannedAllocation(AllocationArea area, size_t size);
/**
* Specify that we have now allocated, or abandoned the allocation
* of, the given amount (in kilobytes) of a storage area that was
* previously notified using notifyPlannedAllocation.
*/
static void notifyDoneAllocation(AllocationArea area, size_t size);
/**
* Force all subsequent recommendations to use the (perhaps
* partial) specification given here. If NoRecommendation given
* here, this will reset to the default free behaviour.
*/
static void setFixedRecommendation(Recommendation recommendation);
/**
* Set the greed level for RAM. This is a value from 0 to 1, by
* which we scale the measured amount of free RAM before using it
* in any heuristics. A value of 1 (the default) indicates that we
* should behave as if we are the main thing the user is running
* and that the free RAM is generally available to us. A value of
* 0 indicates that we should act as if there is never any free
* RAM at all.
*/
static void setRAMGreed(double greed);
private:
static size_t m_discPlanned;
static size_t m_memoryPlanned;
static Recommendation m_baseRecommendation;
static double m_greed;
enum StorageStatus {
Unknown,
Insufficient,
Marginal,
Sufficient
};
static QString criteriaToString(int);
static QString recommendationToString(int);
static QString storageStatusToString(StorageStatus);
};
} // end namespace sv
#endif
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