Circular cache

Fixed-size, array-backed cache that evicts its oldest item. More...

Data Structures
struct	CircularCache
	Circular cache state. More...

Typedefs
typedef void(*	CircularCacheItemDestructor) (void *item)
	Destructor called on an item about to be evicted or flushed.

Functions
void	circular_cache_init (CircularCache *c, uint8_t *buffer, size_t item_size, int total_items, Comparator compare_cb)
	Initialize a circular cache.
void	circular_cache_set_item_destructor (CircularCache *c, CircularCacheItemDestructor destructor)
	Set the destructor called on items when they are evicted or flushed.
bool	circular_cache_contains (CircularCache *c, void *item)
	Check whether the cache contains an item.
void *	circular_cache_get (CircularCache *c, void *theirs)
	Find an item in the cache.
void	circular_cache_push (CircularCache *c, void *item)
	Copy an item into the cache, evicting the oldest one.
void	circular_cache_fill (CircularCache *c, uint8_t *item)
	Set every slot of the cache to a copy of an item.
void	circular_cache_flush (CircularCache *c)
	Call the destructor on every slot and restart eviction from the first one.

Detailed Description

Fixed-size, array-backed cache that evicts its oldest item.

Items are found by linear search with a comparator. See also Keyed circular cache.

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Data Structure Documentation

CircularCache

struct CircularCache

Circular cache state.

Data Fields
uint8_t *	cache	Item array.
Comparator	compare_cb	Comparator, returns 0 for matching items.
CircularCacheItemDestructor	item_destructor	Optional item destructor.
size_t	item_size	Size of an item in bytes.
int	next_erased_item_idx	Index of the next item to evict.
int	total_items	Number of items in cache.

Typedef Documentation

CircularCacheItemDestructor

typedef void(* CircularCacheItemDestructor) (void *item)

Destructor called on an item about to be evicted or flushed.

It is also called on slots that never held an item, so it must recognize those (e.g. all zeros).

Parameters

item

Item.

Function Documentation

circular_cache_contains()

bool circular_cache_contains	(	CircularCache *	c,
		void *	item
	)

Check whether the cache contains an item.

Parameters

c	Circular cache.
item	Item to compare against, of the cache's item size.

Returns

true if an item matches.

circular_cache_fill()

void circular_cache_fill	(	CircularCache *	c,
		uint8_t *	item
	)

Set every slot of the cache to a copy of an item.

Useful to clear a cache to a non-zero value. Asserts if an item destructor is set.

Parameters

c	Circular cache.
item	Item, of the cache's item size.

circular_cache_flush()

void circular_cache_flush

(

CircularCache *

c

)

Call the destructor on every slot and restart eviction from the first one.

The item data is left in place.

Parameters

c	Circular cache.

circular_cache_get()

void * circular_cache_get	(	CircularCache *	c,
		void *	theirs
	)

Find an item in the cache.

Parameters

c	Circular cache.
theirs	Item to compare against, of the cache's item size.

Returns

Matching item in the cache, or NULL.

circular_cache_init()

void circular_cache_init	(	CircularCache *	c,
		uint8_t *	buffer,
		size_t	item_size,
		int	total_items,
		Comparator	compare_cb
	)

Initialize a circular cache.

Parameters

[out]	c	Circular cache.
	buffer	Item array of total_items items of item_size bytes, initialized by the caller.
	item_size	Size of an item in bytes.
	total_items	Number of items.
	compare_cb	Comparator, returns 0 for matching items.

circular_cache_push()

void circular_cache_push	(	CircularCache *	c,
		void *	item
	)

Copy an item into the cache, evicting the oldest one.

Parameters

c	Circular cache.
item	Item, of the cache's item size.

circular_cache_set_item_destructor()

void circular_cache_set_item_destructor	(	CircularCache *	c,
		CircularCacheItemDestructor	destructor
	)

Set the destructor called on items when they are evicted or flushed.

Parameters

c	Circular cache.
destructor	Destructor, NULL for none.