[interval_tree]: Add structures definitions

* Add initial structures definitions.

Signed-off-by: AlexandruCihodaru <[email protected]>
Co-authored-by: Liu Jiang <[email protected]>

Author: AlexandruCihodaru

src/allocation_engine/interval_tree.rs

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+// Copyright (C) 2022 Alibaba Cloud. All rights reserved.
+// Copyright 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2
+
+/// Policy for resource allocation.
+#[derive(Copy, Clone, Debug)]
+pub enum AllocPolicy {
+    /// Allocate from the first matched entry.
+    FirstMatch,
+    /// Allocate first matched entry from the end of the range.
+    LastMatch,
+    // Allocate a memory slot starting with the specified addrres
+    // if it is available.
+    ExactMatch,
+}
+
+impl Default for AllocPolicy {
+    fn default() -> Self {
+        AllocPolicy::FirstMatch
+    }
+}
+
+/// Struct to describe resource allocation constraints.
+#[derive(Copy, Clone, Debug)]
+pub struct Constraint {
+    /// Size to allocate.
+    pub size: u64,
+    /// Lower boundary for the allocated resource.
+    pub min: u64,
+    /// Upper boundary for the allocated resource.
+    pub max: u64,
+    /// Alignment for the allocated resource.
+    pub align: u64,
+    /// Resource allocation policy.
+    pub policy: AllocPolicy,
+}
+
+/// A closed interval range [min, max] used to describe a
+/// memory slot that will be assigned to a device by the VMM.
+/// This structure represents the key of the Node object in
+/// the interval tree implementation.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash)]
+pub struct Range {
+    pub min: u64,
+    pub max: u64,
+}
+
+// Node state for interval tree nodes.
+///
+/// Valid state transition:
+/// - None -> Free: IntervalTree::insert()
+/// - Free -> Allocated: IntervalTree::allocate()
+/// - Allocated -> Free: IntervalTree::free()
+/// - * -> None: IntervalTree::delete()
+#[derive(Clone, Copy, Debug, PartialEq, PartialOrd, Eq, Ord)]
+pub enum NodeState {
+    /// Node is free.
+    Free,
+    /// Node is allocated.
+    Allocated,
+}
+
+/// Internal tree node to implement interval tree.
+#[derive(Debug, PartialEq)]
+pub(crate) struct InnerNode {
+    /// Interval handled by this node.
+    pub(crate) key: Range,
+    /// Optional contained data, None if the node is free.
+    pub(crate) node_state: NodeState,
+    /// Optional left child of current node.
+    pub(crate) left: Option<Box<InnerNode>>,
+    /// Optional right child of current node.
+    pub(crate) right: Option<Box<InnerNode>>,
+    /// Cached height of the node.
+    pub(crate) height: u64,
+    /// Cached maximum valued covered by this node.
+    pub(crate) max_key: u64,
+}

src/allocation_engine/mod.rs

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+// Copyright (C) 2022 Alibaba Cloud. All rights reserved.
+// Copyright 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2
+
+mod interval_tree;
+
+pub use interval_tree::{AllocPolicy, NodeState, Range};