wasmtime_environ/
stack_map.rs

1use serde::{Deserialize, Serialize};
2
3/// A map for determining where live GC references live in a stack frame.
4///
5/// Note that this is currently primarily documented as cranelift's
6/// `binemit::StackMap`, so for detailed documentation about this please read
7/// the docs over there.
8#[derive(Debug, Serialize, Deserialize)]
9pub struct StackMap {
10    bits: Box<[u32]>,
11    mapped_words: u32,
12}
13
14impl StackMap {
15    /// Creates a new `StackMap`, typically from a preexisting
16    /// `binemit::StackMap`.
17    pub fn new(mapped_words: u32, bits: impl Iterator<Item = u32>) -> StackMap {
18        StackMap {
19            bits: bits.collect(),
20            mapped_words,
21        }
22    }
23
24    /// Returns a specified bit.
25    pub fn get_bit(&self, bit_index: usize) -> bool {
26        assert!(bit_index < 32 * self.bits.len());
27        let word_index = bit_index / 32;
28        let word_offset = bit_index % 32;
29        (self.bits[word_index] & (1 << word_offset)) != 0
30    }
31
32    /// Returns the number of words represented by this stack map.
33    pub fn mapped_words(&self) -> u32 {
34        self.mapped_words
35    }
36}
wasmtime_environ/stack_map.rs

wasmtime_environ/
stack_map.rs
