Expand description
Tree data structure.
§Concepts
§Tree
Tree consists of one or more nodes. Empty tree cannot exist since a tree must have just one root node.
§Reference counting
Lifetime of a tree is managed by references to a tree and its nodes.
An object of Tree
type refers to a tree and makes the tree live longer
than the reference.
Objects of node types (Node
, FrozenNode
, and HotNode
types)
refer to nodes. They make the node (and the tree it belongs to) live longer
than the references.
These four types are similar to trees created by node types and
Rc
, but this crate neither leaks the nodes nor releases
the nodes if they are connected to other nodes referred by the user.
See examples below for detail.
use dendron::Node;
let root = Node::new_tree("root");
let grant = root.tree().grant_hierarchy_edit().unwrap();
let child0 = root.create_as_last_child(&grant, "child0");
let child1 = root.create_as_last_child(&grant, "child1");
let child1_0 = child1.create_as_last_child(&grant, "child1_0");
// root
// |-- child0
// `-- child1
// `-- child1_0
drop(grant);
drop(root);
drop(child0);
drop(child1);
// Now only `child1_0` is alive.
// `child1_0` makes the entire tree and belonging nodes alive,
// so `root` is still alive.
assert_eq!(*child1_0.root().borrow_data(), "root");
let tree = child1_0.tree();
drop(child1_0);
// Now all node references are dropped and only `tree` is alive.
// `tree` makes the entire tree and belonging nodes alive,
// so `child0` is still alive.
assert_eq!(
*tree.root().first_child().unwrap().borrow_data(),
"child0"
);
drop(tree);
// Now all tree references and node references are dropped, so all objects
// in the tree is released. No memory leaks!
§Hierarchy edit prohibitions and grants
Sometimes users may wish tree hierarchy to be preserved, especially when they are iterating nodes.
use dendron::tree_node;
let root = tree_node! {
"root", [
"0",
"1",
"2",
]
};
let grant = root.tree().grant_hierarchy_edit().unwrap();
let mut children = root.children();
// Detach the first child from `root`.
root.first_child().unwrap().detach_subtree(&grant);
// Next node is... not "1"! This is because `children` have a cache of
// "next node" at the creation of the iterator.
assert_eq!(children.next().map(|node| *node.borrow_data()), Some("0"));
assert_eq!(children.next(), None);
To enable “freezing” hierarchy, this crate requires users to have a “grant” to edit hierarchy, and also provides capability to “prohibit” hierarchy editing (for arbitrary duration).
use dendron::tree;
let tree = tree! { "root" };
// This "prohibition" prohibits tree hierarchy editing
// (and grant acquisition).
let freezer = tree.prohibit_hierarchy_edit().unwrap();
// This `grant_hierarchy_edit()` fails, so you can ensure
// the hierarchy is stable until `freezer` is dropped!
let grant = tree.grant_hierarchy_edit().unwrap();
“Grant” (HierarchyEditGrant
) and “prohibition” (HierarchyEditProhibition
)
works in ways similar to MutexGuard
.
The grants and prohibitions work like scoped locks; trees are editable or
non-editable during grants or prohibitions exist, and once they are dropped,
trees become neutral.
Note that grants and prohibitions are mutually exclusive, but only multiple grants or only multiple prohibitions can coexist for a tree, like reader locks. In other words, you can have multiple grants for a tree, and also can have multiple prohibitions for a tree, but not both at the same time.
use dendron::tree;
let tree = tree! { "root" };
let freezer1 = tree.prohibit_hierarchy_edit().unwrap();
// You can have multiple prohibitions at the same time.
let freezer2 = tree.prohibit_hierarchy_edit().unwrap();
let freezer3 = tree.prohibit_hierarchy_edit().unwrap();
// But not both prohibitions and grants.
assert!(tree.grant_hierarchy_edit().is_err());
// Release the locks.
drop(freezer1);
drop(freezer2);
drop(freezer3);
// Now the tree is neutral. You can re-prohibit or grant hierarchy edit.
let grant = tree.grant_hierarchy_edit().unwrap();
// Again, prohibitions and grants cannot coexist for the same tree.
assert!(tree.prohibit_hierarchy_edit().is_err());
§Nodes
The crate provides three node types: Node
, FrozenNode
, and
HotNode
. They all have shared ownerships of the tree they belong to.
Node
is the basic neutral plain node. It can be turned into FrozenNode
or HotNode
by generating or bundling a prohibition or a grant to edit
hierarchy.
FrozenNode
is a Node
with a hierarchy edit prohibition bundled. This
exposes some extra methods to create tree traversal iterators, for example
FrozenNode::children_stable
and
FrozenNode::allocating_breadth_first_traverse_stable
.
HotNode
is a Node
with a hierarchy edit grant bundled. This exposes
some extra methods to edit tree hierarchy without passing grants as
arguments, for example HotNode::detach_subtree
and
HotNode::try_create_node_as
.
§Usage
To create tree directly, use tree_node!
or tree!
.
use dendron::{tree, tree_node};
let root1 = tree_node! {
"root", [
"0",
/("1", [
/("1-0", [
"1-0-0"
]),
"1-1",
]),
]
};
let tree1 = root1.tree();
let tree2 = tree! {
"root", [
"0",
/("1", [
/("1-0", [
"1-0-0"
]),
"1-1",
]),
]
};
let root2 = tree2.root();
assert_eq!(root1, root2);
assert_eq!(tree1, tree2);
To create a new orphan (root) node, use Node::new_tree
or
HotNode::new_tree
.
use dendron::Node;
let root = Node::new_tree("root");
For other operations (creating a node that is connected to other nodes,
moving nodes to other places, iterating nodes, getting and setting data,
etc.), see methods of node types (Node
, FrozenNode
, and HotNode
).
Re-exports§
pub use self::node::FrozenNode;
pub use self::node::HierarchyError;
pub use self::node::HotNode;
pub use self::node::Node;
pub use self::node::NodeWeak;
pub use self::tree::HierarchyEditGrant;
pub use self::tree::HierarchyEditProhibition;
pub use self::tree::Tree;
pub use self::tree::TreeWeak;
Modules§
Macros§
- tree
- A macro that evaluates to the root node of a new tree of type
Tree
. - tree_
node - A macro that evaluates to the root node (of type
Node
) of a new tree.
Enums§
- AdoptAs
- Relation of the node being adopted.
- Insert
As - Target destination to insert, append, or prepend a node.
Type Aliases§
- Debug
Pretty Print Deprecated - Deprecated re-export of
node::DebugPrettyPrint
. - Hierarchy
Edit Grant Error Deprecated - Deprecated re-export of
tree::HierarchyEditGrantError
. - Hierarchy
Edit Prohibition Error Deprecated - Deprecated re-export of
tree::HierarchyEditProhibitionError
.