lv_cache.h

Functions

lv_cache_t *lv_cache_create(const lv_cache_class_t *cache_class, size_t node_size, size_t max_size, lv_cache_ops_t ops)

Create a cache object with the given parameters.

参数:

cache_class -- The class of the cache. Currently only support one two builtin classes: @lv_cache_class_lru_rb_count for LRU-based cache with count-based eviction policy. @lv_cache_class_lru_rb_size for LRU-based cache with size-based eviction policy.
node_size -- The node size is the size of the data stored in the cache..
max_size -- The max size is the maximum amount of memory or count that the cache can hold. @lv_cache_class_lru_rb_count: max_size is the maximum count of nodes in the cache. @lv_cache_class_lru_rb_size: max_size is the maximum size of the cache in bytes.
ops -- A set of operations that can be performed on the cache. See @lv_cache_ops_t for details.

返回:

Returns a pointer to the created cache object on success, @NULL on error.

void lv_cache_destroy(lv_cache_t *cache, void *user_data)

Destroy a cache object.

参数:

cache -- The cache object pointer to destroy.
user_data -- A user data pointer that will be passed to the free callback.

lv_cache_entry_t *lv_cache_acquire(lv_cache_t *cache, const void *key, void *user_data)

Acquire a cache entry with the given key. If the entry is not in the cache, it will return @NULL as it is not found. If the entry is found, it's priority will be changed by the cache's policy. And the @lv_entry_t::ref count will be incremented.

参数:

cache -- The cache object pointer to acquire the entry.
key -- The key of the entry to acquire.
user_data -- A user data pointer that will be passed to the create callback.

返回:

Returns a pointer to the acquired cache entry on success with @lv_entry_t::ref count incremented, @NULL on error.

lv_cache_entry_t *lv_cache_acquire_or_create(lv_cache_t *cache, const void *key, void *user_data)

Acquire a cache entry with the given key. If the entry is not in the cache, it will create a new entry with the given key. If the entry is found, it's priority will be changed by the cache's policy. And the @lv_entry_t::ref count will be incremented. If you want to use this API to simplify the code, you should provide a @lv_cache_ops_t::create_cb that creates a new entry with the given key. This API is a combination of @lv_cache_acquire and @lv_cache_add. The effect is the same as calling @lv_cache_acquire and @lv_cache_add separately. And the internal impact on cache is also consistent with these two APIs.

参数:

cache -- The cache object pointer to acquire the entry.
key -- The key of the entry to acquire or create.
user_data -- A user data pointer that will be passed to the create callback.

返回:

Returns a pointer to the acquired or created cache entry on success with @lv_entry_t::ref count incremented, @NULL on error.

lv_cache_entry_t *lv_cache_add(lv_cache_t *cache, const void *key, void *user_data)

Add a new cache entry with the given key and data. If the cache is full, the cache's policy will be used to evict an entry.

参数:

cache -- The cache object pointer to add the entry.
key -- The key of the entry to add.
user_data -- A user data pointer that will be passed to the create callback.

返回:

Returns a pointer to the added cache entry on success with @lv_entry_t::ref count incremented, @NULL on error.

void lv_cache_release(lv_cache_t *cache, lv_cache_entry_t *entry, void *user_data)

Release a cache entry. The @lv_entry_t::ref count will be decremented. If the @lv_entry_t::ref count is zero, it will issue an error. If the entry passed to this function is the last reference to the data and the entry is marked as invalid, the cache's policy will be used to evict the entry.

参数:

cache -- The cache object pointer to release the entry.
entry -- The cache entry pointer to release.
user_data -- A user data pointer that will be passed to the free callback.

void lv_cache_reserve(lv_cache_t *cache, uint32_t reserved_size, void *user_data)

Reserve a certain amount of memory/count in the cache. This function is useful when you want to reserve a certain amount of memory/count in advance, for example, when you know that you will need it later. When the current cache size is max than the reserved size, the function will evict entries until the reserved size is reached.

参数:

cache -- The cache object pointer to reserve.
reserved_size -- The amount of memory/count to reserve.
user_data -- A user data pointer that will be passed to the free callback.

void lv_cache_drop(lv_cache_t *cache, const void *key, void *user_data)

Drop a cache entry with the given key. If the entry is not in the cache, nothing will happen to it. If the entry is found, it will be removed from the cache and its data will be freed when the last reference to it is released.

备注

The data will not be freed immediately but when the last reference to it is released. But this entry will not be found by @lv_cache_acquire. If you want cache a same key again, you should use @lv_cache_add or @lv_cache_acquire_or_create.

参数:

cache -- The cache object pointer to drop the entry.
key -- The key of the entry to drop.
user_data -- A user data pointer that will be passed to the free callback.

void lv_cache_drop_all(lv_cache_t *cache, void *user_data)

Drop all cache entries. All entries will be removed from the cache and their data will be freed when the last reference to them is released.

备注

If some entries are still referenced by other objects, it will issue an error. And this case shouldn't happen in normal cases..

参数:

cache -- The cache object pointer to drop all entries.
user_data -- A user data pointer that will be passed to the free callback.

bool lv_cache_evict_one(lv_cache_t *cache, void *user_data)

Evict one entry from the cache. The eviction policy will be used to select the entry to evict.

参数:

cache -- The cache object pointer to evict an entry.
user_data -- A user data pointer that will be passed to the free callback.

返回:

Returns true if an entry is evicted, false if no entry is evicted.

void lv_cache_set_max_size(lv_cache_t *cache, size_t max_size, void *user_data)

Set the maximum size of the cache. If the current cache size is greater than the new maximum size, the cache's policy will be used to evict entries until the new maximum size is reached. If set to 0, the cache will be disabled.

备注

But this behavior will happen only new entries are added to the cache.

参数:

cache -- The cache object pointer to set the maximum size.
max_size -- The new maximum size of the cache.
user_data -- A user data pointer that will be passed to the free callback.

size_t lv_cache_get_max_size(lv_cache_t *cache, void *user_data)

Get the maximum size of the cache.

参数:

cache -- The cache object pointer to get the maximum size.
user_data -- A user data pointer that will be passed to the free callback.

返回:

Returns the maximum size of the cache.

size_t lv_cache_get_size(lv_cache_t *cache, void *user_data)

Get the current size of the cache.

参数:

cache -- The cache object pointer to get the current size.
user_data -- A user data pointer that will be passed to the free callback.

返回:

Returns the current size of the cache.

size_t lv_cache_get_free_size(lv_cache_t *cache, void *user_data)

Get the free size of the cache.

参数:

cache -- The cache object pointer to get the free size.
user_data -- A user data pointer that will be passed to the free callback.

返回:

Returns the free size of the cache.

bool lv_cache_is_enabled(lv_cache_t *cache)

Return true if the cache is enabled. Disabled cache means that when the max_size of the cache is 0. In this case, all cache operations will be no-op.

参数:: cache -- The cache object pointer to check if it's disabled.
返回:: Returns true if the cache is enabled, false otherwise.

void lv_cache_set_compare_cb(lv_cache_t *cache, lv_cache_compare_cb_t compare_cb, void *user_data)

Set the compare callback of the cache.

参数:

cache -- The cache object pointer to set the compare callback.
compare_cb -- The compare callback to set.
user_data -- A user data pointer.

void lv_cache_set_create_cb(lv_cache_t *cache, lv_cache_create_cb_t alloc_cb, void *user_data)

Set the create callback of the cache.

参数:

cache -- The cache object pointer to set the create callback.
alloc_cb -- The create callback to set.
user_data -- A user data pointer.

void lv_cache_set_free_cb(lv_cache_t *cache, lv_cache_free_cb_t free_cb, void *user_data)

Set the free callback of the cache.

参数:

cache -- The cache object pointer to set the free callback.
free_cb -- The free callback to set.
user_data -- A user data pointer.

void lv_cache_set_name(lv_cache_t *cache, const char *name)

Give a name for a cache object. Only the pointer of the string is saved.

参数:

cache -- The cache object pointer to set the name.
name -- The name of the cache.

const char *lv_cache_get_name(lv_cache_t *cache)

Get the name of a cache object.

参数:: cache -- The cache object pointer to get the name.
返回:: Returns the name of the cache.