`core:container/lru`dev-2022-02

1 files changed, 183 insertions, 0 deletions

diff --git a/core/container/lru/lru_cache.odin b/core/container/lru/lru_cache.odin
new file mode 100644
index 000000000..02bb20da0
--- /dev/null
+++ b/core/container/lru/lru_cache.odin
@@ -0,0 +1,183 @@
+package container_lru
+
+import "core:intrinsics"
+import "core:mem"
+_ :: intrinsics
+_ :: mem
+
+Node :: struct($Key, $Value: typeid) where intrinsics.type_is_valid_map_key(Key) {
+	prev, next: ^Node(Key, Value),
+	key:   Key,
+	value: Value,
+}
+
+// Cache is an LRU cache. It automatically removes entries as new entries are
+// added if the capacity is reached. Entries are removed based on how recently
+// they were used where the oldest entries are removed first.
+Cache :: struct($Key, $Value: typeid) where intrinsics.type_is_valid_map_key(Key) {
+	head: ^Node(Key, Value),
+	tail: ^Node(Key, Value),
+
+	entries: map[Key]^Node(Key, Value),
+
+	count:    int,
+	capacity: int,
+
+	node_allocator: mem.Allocator,
+
+	on_remove: proc(key: Key, value: Value, user_data: rawptr),
+	on_remove_user_data: rawptr,
+	call_on_remove_on_destroy: bool,
+}
+
+// init initializes a Cache
+init :: proc(c: ^$C/Cache($Key, $Value), capacity: int, entries_allocator := context.allocator, node_allocator := context.allocator) {
+	c.entries.allocator = entries_allocator
+	c.node_allocator = node_allocator
+	c.capacity = capacity
+}
+
+// destroy deinitializes a Cache
+destroy :: proc(c: ^$C/Cache($Key, $Value)) {
+	for _, node in c.entries {
+		if c.call_on_remove_on_destroy && c.on_remove != nil {
+			c.on_remove(node.key, node.value, c.on_remove_user_data)
+		}
+		free(node, c.node_allocator)
+	}
+	clear(&c.entries)
+	delete(c.entries)
+	c.head = nil
+	c.tail = nil
+	c.count = 0
+}
+
+// set the given key value pair. This operation updates the recent usage of the item.
+set :: proc(c: ^$C/Cache($Key, $Value), key: Key, value: Value) -> mem.Allocator_Error {
+	if e, ok := c.entries[key]; ok {
+		e.value = value
+		return nil
+	}
+
+	e := new(Node(Key, Value), c.node_allocator) or_return
+	e.key = key
+	e.value = value
+
+	_push_front_node(c, e)
+	if c.count > c.capacity {
+		_remove_node(c, c.tail)
+	}
+
+	c.entries[key] = e
+	return nil
+}
+
+// get a value from the cache from a given key. This operation updates the usage of the item.
+get :: proc(c: ^$C/Cache($Key, $Value), key: Key) -> (value: Value, ok: bool) #optional_ok {
+	e: ^Node(Key, Value)
+	e, ok = c.entries[key]
+	if !ok {
+		return
+	}
+	_pop_node(c, e)
+	_push_front_node(c, e)
+	return e.value, true
+}
+
+// get_ptr gets the pointer to a value the cache from a given key. This operation updates the usage of the item.
+get_ptr :: proc(c: ^$C/Cache($Key, $Value), key: Key) -> (value: ^Value, ok: bool) #optional_ok {
+	e: ^Node(Key, Value)
+	e, ok = c.entries[key]
+	if !ok {
+		return
+	}
+	_pop_node(c, e)
+	_push_front_node(c, e)
+	return &e.value, true
+}
+
+// peek gets the value from the cache from a given key without updating the recent usage.
+peek :: proc(c: ^$C/Cache($Key, $Value), key: Key) -> (value: Value, ok: bool) #optional_ok {
+	e: ^Node(Key, Value)
+	e, ok = c.entries[key]
+	if !ok {
+		return
+	}
+	return e.value, true
+}
+
+// exists checks for the existence of a value from a given key without updating the recent usage.
+exists :: proc(c: ^$C/Cache($Key, $Value), key: Key) -> bool {
+	return key in c.entries
+}
+
+// remove removes an item from the cache.
+remove :: proc(c: ^$C/Cache($Key, $Value), key: Key) -> bool {
+	e, ok := c.entries[key]
+	if !ok {
+		return false
+	}
+	_remove_node(c, e)
+	return true
+}
+
+
+@(private)
+_remove_node :: proc(c: ^$C/Cache($Key, $Value), node: ^Node(Key, Value)) {
+	if c.head == node {
+		c.head = node.next
+	}
+	if c.tail == node {
+		c.tail = node.prev
+	}
+	if node.prev != nil {
+		node.prev.next = node.next
+	}
+	if node.next != nil {
+		node.next.prev = node.prev
+	}
+	node.prev = nil
+	node.next = nil
+
+	c.count -= 1
+
+	delete_key(&c.entries, node.key)
+
+	if c.on_remove != nil {
+		c.on_remove(node.key, node.value, c.on_remove_user_data)
+	}
+
+	free(node, c.node_allocator)
+
+}
+
+@(private)
+_push_front_node :: proc(c: ^$C/Cache($Key, $Value), e: ^Node(Key, Value)) {
+	if c.head != nil {
+		e.next = c.head
+		e.next.prev = e
+	}
+	c.head = e
+	if c.tail == nil {
+		c.tail = e
+	}
+	e.prev = nil
+
+	c.count += 1
+}
+
+@(private)
+_pop_node :: proc(c: ^$C/Cache($Key, $Value), e: ^Node(Key, Value)) {
+	if e == nil {
+		return
+	}
+	if e.prev != nil {
+		e.prev.next = e.next
+	}
+
+	if e.next != nil {
+		e.next.prev = e.prev
+	}
+	e.prev = nil
+	e.next = nil
+}
\ No newline at end of file