wasmtime/runtime/vm/memory/
static_.rs

1//! Support for implementing the [`RuntimeLinearMemory`] trait in terms of a
2//! fixed allocation that cannot move.
3
4use crate::prelude::*;
5use crate::runtime::vm::MemoryBase;
6use crate::runtime::vm::memory::RuntimeLinearMemory;
7
8/// A "static" memory where the lifetime of the backing memory is managed
9/// elsewhere. Currently used with the pooling allocator.
10pub struct StaticMemory {
11    /// The base pointer of this static memory, wrapped up in a send/sync
12    /// wrapper.
13    base: MemoryBase,
14
15    /// The byte capacity of the `base` pointer.
16    capacity: usize,
17
18    /// The current size, in bytes, of this memory.
19    size: usize,
20}
21
22impl StaticMemory {
23    pub fn new(
24        base: MemoryBase,
25        base_capacity: usize,
26        initial_size: usize,
27        maximum_size: Option<usize>,
28    ) -> Result<Self> {
29        if base_capacity < initial_size {
30            bail!(
31                "initial memory size of {initial_size} exceeds the pooling allocator's \
32                 configured maximum memory size of {base_capacity} bytes",
33            );
34        }
35
36        // Only use the part of the slice that is necessary.
37        let base_capacity = match maximum_size {
38            Some(max) if max < base_capacity => max,
39            _ => base_capacity,
40        };
41
42        Ok(Self {
43            base,
44            capacity: base_capacity,
45            size: initial_size,
46        })
47    }
48}
49
50impl RuntimeLinearMemory for StaticMemory {
51    fn byte_size(&self) -> usize {
52        self.size
53    }
54
55    fn byte_capacity(&self) -> usize {
56        self.capacity
57    }
58
59    fn grow_to(&mut self, new_byte_size: usize) -> Result<()> {
60        // Never exceed the static memory size; this check should have been made
61        // prior to arriving here.
62        assert!(new_byte_size <= self.capacity);
63
64        // Update our accounting of the available size.
65        self.size = new_byte_size;
66        Ok(())
67    }
68
69    fn set_byte_size(&mut self, len: usize) {
70        self.size = len;
71    }
72
73    fn base(&self) -> MemoryBase {
74        self.base.clone()
75    }
76
77    fn vmmemory(&self) -> crate::vm::VMMemoryDefinition {
78        crate::vm::VMMemoryDefinition {
79            base: self.base.as_non_null().into(),
80            current_length: self.size.into(),
81        }
82    }
83}
wasmtime/runtime/vm/memory/static_.rs

wasmtime/runtime/vm/memory/
static_.rs
