ealloc 0.10.0

no_std memory allocator with pluggable free-block management strategies (TLSF, first-fit, half-tree)
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278

use core::{
    hint::{assert_unchecked, unreachable_unchecked},
    marker::PhantomData,
    ptr::NonNull,
};

use const_default::ConstDefault;

use ecore::int::{CInt, PrimaryUInt};

use super::{
    ElementCount, FreeBlockManager,
    ptr::{OptimizedPtr, Ptr},
};

/// [Half Tree allocator](https://trepo.tuni.fi/bitstream/handle/10024/140229/AuvinenEetu.pdf),
/// **not include DV, requires wrapped by** [crate::DesignatedVictim] **to get DV**
/// * `StateElement` see [FreeBlockManager::StateElement]
/// * `Element` [FreeBlockManager::Element]
/// * `OptiPtr` ptr for free block, maybe narrowed, see `OptimizedPtr`, affects [FreeBlockManager::address_range] and [FreeBlockManager::Node],
///   actually [FreeBlockManager::Node] is three `OptiPtr`
pub struct HalfTree<StateElement, Element, OptiPtr: OptimizedPtr<Element>, const BINS_COUNT: usize> {
    bins: [Option<OptiPtr>; BINS_COUNT],
    bins_map: StateElement,
    base: OptiPtr::VirtualBase,
}

#[derive(Clone, Copy)]
pub struct Node<OptiPtr> {
    llink: Option<OptiPtr>,
    rlink: Option<OptiPtr>,
    siblink: Option<OptiPtr>,
}
impl<OptiPtr> Node<OptiPtr> {
    const NULL: Self = Self { llink: None, rlink: None, siblink: None };
}
impl<OptiPtr> Ptr<Node<OptiPtr>> {
    fn llink(self) -> Ptr<Option<OptiPtr>> {
        Ptr::from(unsafe { &mut self.raw().as_mut().llink })
    }

    fn rlink(self) -> Ptr<Option<OptiPtr>> {
        Ptr::from(unsafe { &mut self.raw().as_mut().rlink })
    }

    fn siblink(self) -> Ptr<Option<OptiPtr>> {
        Ptr::from(unsafe { &mut self.raw().as_mut().siblink })
    }
}

impl<StateElement: PrimaryUInt, Element, OptiPtr: OptimizedPtr<Element>, const BINS_COUNT: usize> Default
    for HalfTree<StateElement, Element, OptiPtr, BINS_COUNT>
{
    fn default() -> Self {
        Self::new()
    }
}

impl<StateElement: PrimaryUInt, Element, OptiPtr: OptimizedPtr<Element>, const BINS_COUNT: usize> HalfTree<StateElement, Element, OptiPtr, BINS_COUNT> {
    const MIN_ELEMENT_COUNT: usize = ElementCount::<StateElement, Element>::min_for::<Node<OptiPtr>>().to_count();

    pub const fn new() -> Self {
        const { assert!((BINS_COUNT as u32) < StateElement::BITS) };
        Self { bins: [None; BINS_COUNT], bins_map: StateElement::ZERO, base: ConstDefault::DEFAULT }
    }

    fn get_element_count(node: Ptr<Node<OptiPtr>>) -> usize {
        ElementCount::<StateElement, Element>::get_from_block(node.raw().cast()).to_count()
    }

    fn base(&self) -> Base<Element, OptiPtr> {
        Base { element: PhantomData, base: self.base }
    }

    /// unlink link's node must ensure link is not empty
    fn unlink_node(base: Base<Element, OptiPtr>, mut link: Ptr<Option<OptiPtr>>) {
        let node = base.get_node(link.read().unwrap_or_else(|| unsafe { unreachable_unchecked() }));
        if let Some(optr) = node.siblink().read() {
            let sibnode = base.get_node(optr);
            *sibnode.llink().as_mut() = node.llink().read();
            *sibnode.rlink().as_mut() = node.rlink().read();
            *link.as_mut() = Some(optr); // replace with sibling
        } else {
            let mut leaf_link = link;
            let mut leaf_node = node;
            loop {
                if let Some(loptr) = leaf_node.llink().read() {
                    leaf_link = leaf_node.llink();
                    leaf_node = base.get_node(loptr)
                } else if let Some(roptr) = leaf_node.rlink().read() {
                    leaf_link = leaf_node.rlink();
                    leaf_node = base.get_node(roptr)
                } else {
                    break;
                }
            }
            if leaf_link != link {
                *link.as_mut() = leaf_link.as_mut().take(); // leaf_link maybe node's llink or rlink, should take first
                *leaf_node.llink().as_mut() = node.llink().read();
                *leaf_node.rlink().as_mut() = node.rlink().read();
            } else {
                *leaf_link.as_mut() = None;
            }
        }
    }
}

impl<StateElement: PrimaryUInt, Element, OptiPtr: OptimizedPtr<Element>, const BINS_COUNT: usize> FreeBlockManager
    for HalfTree<StateElement, Element, OptiPtr, BINS_COUNT>
{
    type StateElement = StateElement;
    type Element = Element;
    type Node = Node<OptiPtr>;

    const MAX_ELEMENT_COUNT: ElementCount<Self::StateElement, Self::Element> = ElementCount::max_for_bits::<BINS_COUNT>();

    fn take_out(&mut self, element_count: super::ElementCount<Self::StateElement, Self::Element>) -> Option<NonNull<Self::Node>> {
        let base = self.base();
        let Self { bins, bins_map, .. } = self;
        let count = element_count.to_count();
        unsafe { assert_unchecked(count >= Self::MIN_ELEMENT_COUNT && count <= Self::MAX_ELEMENT_COUNT.to_count()) };
        let bid = count.ilog2(); // most set bit
        {
            let bin = Ptr::from(bins.get_mut(bid as usize).unwrap_or_else(|| unsafe { unreachable_unchecked() }));
            let mut link = bin;
            let mut pos = bid;
            while let Some(optr) = link.read() {
                let node = base.get_node(optr);
                if Self::get_element_count(node) < count {
                    let Some(next_pos) = pos.checked_sub(1) else { break };
                    if node.rlink().read().is_some() {
                        link = node.rlink();
                    } else if count & 1 << next_pos != 0 {
                        break;
                    } else if node.llink().read().is_some() {
                        link = node.llink();
                    } else {
                        break;
                    }
                    pos = next_pos;
                } else {
                    Self::unlink_node(base, link);
                    if bin.read().is_none() {
                        *bins_map &= !(StateElement::ONE << bid);
                    }
                    return Some(node.raw());
                }
            }
        }
        let bid = bid + 1;
        let bid = CInt::trailing_zeros(*bins_map >> bid) + bid;
        let bin = Ptr::from(bins.get_mut(bid as usize)?);
        let optr = bin.read().unwrap_or_else(|| unsafe { unreachable_unchecked() });
        Self::unlink_node(base, bin);
        if bin.read().is_none() {
            *bins_map &= !(StateElement::ONE << bid);
        }
        Some(base.get_node(optr).raw())
    }

    unsafe fn register(&mut self, node: NonNull<Self::Node>) {
        let base = self.base();
        let mut node = Ptr::new(node);
        let count = Self::get_element_count(node);
        unsafe { assert_unchecked(count >= Self::MIN_ELEMENT_COUNT && count <= Self::MAX_ELEMENT_COUNT.to_count()) };
        let mut pos = count.ilog2(); // most set bit
        self.bins_map |= StateElement::ONE << pos;
        let bin = self.bins.get_mut(pos as usize).unwrap_or_else(|| unsafe { unreachable_unchecked() });
        let Some(optr) = *bin else {
            *node.as_mut() = Node::NULL;
            *bin = Some(base.new_ptr(node));
            return;
        };
        let mut itnode = base.get_node(optr);
        loop {
            if Self::get_element_count(itnode) == count {
                *node.as_mut() = Node::NULL;
                *node.siblink().as_mut() = itnode.siblink().read();
                *itnode.siblink().as_mut() = Some(base.new_ptr(node));
                return;
            }
            unsafe { assert_unchecked(pos != 0) }; //count always equals to block count when pos == 0
            pos -= 1;
            let optr = if count & 1 << pos == 0 {
                if let Some(loptr) = itnode.llink().read() {
                    loptr
                } else {
                    *node.as_mut() = Node::NULL;
                    *itnode.llink().as_mut() = Some(base.new_ptr(node));
                    return;
                }
            } else {
                if let Some(roptr) = itnode.rlink().read() {
                    roptr
                } else {
                    *node.as_mut() = Node::NULL;
                    *itnode.rlink().as_mut() = Some(base.new_ptr(node));
                    return;
                }
            };
            itnode = base.get_node(optr);
        }
    }

    unsafe fn unregister(&mut self, node: NonNull<Self::Node>) {
        let base = self.base();
        let Self { bins, bins_map, .. } = self;
        let node = Ptr::new(node);
        let count = Self::get_element_count(node);
        unsafe { assert_unchecked(count >= Self::MIN_ELEMENT_COUNT && count <= Self::MAX_ELEMENT_COUNT.to_count()) };
        let bid = count.ilog2(); // most set bit
        let bin = Ptr::from(bins.get_mut(bid as usize).unwrap_or_else(|| unsafe { unreachable_unchecked() }));
        let mut link = bin;
        let mut pos = bid;
        loop {
            let mut itnode = base.get_node(link.read().unwrap_or_else(|| unsafe { unreachable_unchecked() }));
            if Self::get_element_count(itnode) == count {
                if itnode == node {
                    Self::unlink_node(base, link);
                    if bin.read().is_none() {
                        *bins_map &= !(StateElement::ONE << bid);
                    }
                    return;
                } else {
                    let optr = base.new_ptr(node);
                    loop {
                        let sibling = itnode.siblink().read().unwrap_or_else(|| unsafe { unreachable_unchecked() });
                        if sibling == optr {
                            *itnode.siblink().as_mut() = node.siblink().read();
                            return;
                        } else {
                            itnode = base.get_node(sibling);
                        }
                    }
                }
            }
            unsafe { assert_unchecked(pos != 0) }; // must founded when pos == 0
            pos -= 1;
            link = if count & 1 << pos == 0 { itnode.llink() } else { itnode.rlink() };
        }
    }

    unsafe fn init(&mut self, ptr: NonNull<Self::Element>) {
        self.base = OptiPtr::new_base(ptr);
        unsafe { self.register(ptr.cast()) };
    }

    unsafe fn extend(&mut self, ptr: NonNull<Self::Element>) {
        unsafe { self.register(ptr.cast()) };
    }

    fn address_range(&self) -> (usize, usize) {
        OptiPtr::address_range(self.base)
    }
}

#[repr(transparent)]
struct Base<Element, OptiPtr: OptimizedPtr<Element>> {
    element: PhantomData<Element>,
    base: OptiPtr::VirtualBase,
}

impl<Element, OptiPtr: OptimizedPtr<Element>> Copy for Base<Element, OptiPtr> {}
impl<Element, OptiPtr: OptimizedPtr<Element>> Clone for Base<Element, OptiPtr> {
    fn clone(&self) -> Self {
        *self
    }
}

impl<Element, OptiPtr: OptimizedPtr<Element>> Base<Element, OptiPtr> {
    fn get_node(self, opti_ptr: OptiPtr) -> Ptr<Node<OptiPtr>> {
        Ptr::new(opti_ptr.get(self.base).cast())
    }

    fn new_ptr(self, node: Ptr<Node<OptiPtr>>) -> OptiPtr {
        OptiPtr::new(self.base, node.raw().cast())
    }
}