TrixelCache< content > Class Template Reference

#include <trixelcache.h>

Inheritance diagram for TrixelCache< content >:

Classes
class	element

Public Member Functions
	TrixelCache (const size_t data_size, const size_t cache_size)
void	clear () noexcept
size_t	current_usage ()
bool	noop () const
element &	operator[] (const size_t index) noexcept
std::list< size_t >	primed_indices ()
void	prune (size_t keep=0) noexcept
void	set_size (const size_t size)
size_t	size () const

Detailed Description

template<typename content>
class TrixelCache< content >

A simple integer indexed elastically cached wrapper around std::vector to hold container types content which are cheap to construct empty and provide a default constructor, as well as [], size and swap members (think std::vector and std::list).

The caching mechanism will be short-circuited if the cache size equals the data size.

The container is resized to a given data_size by default initializing its elements. The elements are stored as TrixelCache::element objects and retrieved by index and LRU cached on the fly. To test if a given element is cached (or not empty) the TrixelCache::element::is_set() can be queried. Setting an element works by just assigning it with the new data. The data from an element can be retrieved through the TrixelCache::element::data() member. Modifying the data through that reference is allowed.

Setting an element is done by assigning it the new data.

When it is convenient TrixelCache::prune() may be called, which clears the least recently used elements (by default initializing them) until the number of elements does not exceed the cache size. This is expensive relative to setting an elment which has almost no cost.

Template Parameters

content

The content type to use. Most likely a QList, std::vector or std::list.

Todo

Use std::optional when C++17 is adopted in kstars.

Example

TrixelCache<std::vector<int>> cache(100, 10);
auto& element = chache[0];
 
if(!elmenent.is_set())
  elment = std::vector<int> {1, 2, 3, 4};
 
std::cout << cache[0].data(); // {1, 2, 3, 4}

Definition at line 59 of file trixelcache.h.

Constructor & Destructor Documentation

TrixelCache()

template<typename content >

TrixelCache< content >::TrixelCache ( const size_t data_size, const size_t cache_size )

inline

Constructs a cache with data_size default constructed elements with an elastic ceiling capacity of cache_size.

Definition at line 108 of file trixelcache.h.

Member Function Documentation

clear()

template<typename content >

void TrixelCache< content >::clear ( )

inlinenoexcept

Clear the cache without changing it's size.

Definition at line 187 of file trixelcache.h.

current_usage()

template<typename content >

size_t TrixelCache< content >::current_usage ( )

inline

Returns

the number of set elements in the cache, slow

Definition at line 170 of file trixelcache.h.

noop()

template<typename content >

bool TrixelCache< content >::noop ( ) const

inline

Returns

wether the cache is just a wrapped vector

Definition at line 184 of file trixelcache.h.

operator[]()

template<typename content >

element & TrixelCache< content >::operator[] ( const size_t index )

inlinenoexcept

Retrieve an element at index.

Definition at line 118 of file trixelcache.h.

primed_indices()

template<typename content >

std::list< size_t > TrixelCache< content >::primed_indices ( )

inline

Returns

a list of currently primed indices, slow

Definition at line 177 of file trixelcache.h.

prune()

template<typename content >

void TrixelCache< content >::prune ( size_t keep = 0 )

inlinenoexcept

Remove excess elements from the cache The capacity can be temporarily readjusted to keep.

keep must be greater than the cache size to be of effect.

Definition at line 131 of file trixelcache.h.

set_size()

template<typename content >

void TrixelCache< content >::set_size ( const size_t size )

inline

Reset the cache size to size.

This does clear the cache.

Definition at line 155 of file trixelcache.h.

size()

template<typename content >

size_t TrixelCache< content >::size ( ) const

inline

Returns

the size of the cache

Definition at line 167 of file trixelcache.h.

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The documentation for this class was generated from the following file:

• trixelcache.h