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