wasmtime_environ/
hostcall.rs

1use crate::BuiltinFunctionIndex;
2#[cfg(feature = "component-model")]
3use crate::component::ComponentBuiltinFunctionIndex;
4
5/// Enumeration of all possible ways that wasm may execute code in the
6/// host.
7///
8/// This type is intended to be serialized into a 32-bit index (or smaller) and
9/// is used by Pulley for example to identify how transitions from the guest to
10/// the host are performed.
11#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
12pub enum HostCall {
13    /// An "array call" is being done which means that the wasm is calling the
14    /// host using the array calling convention (e.g. `VMArrayCallNative`).
15    ArrayCall,
16
17    /// A builtin function, e.g. for `memory.grow`, is being called. Each
18    /// builtin has its own ABI.
19    Builtin(BuiltinFunctionIndex),
20
21    /// A lowered component function is being called. This is done by a
22    /// trampoline generated by Cranelift and is distinct from the array calling
23    /// convention.
24    ///
25    /// This correspond to `VMLoweringCallee`.
26    #[cfg(feature = "component-model")]
27    ComponentLowerImport,
28
29    /// A builtin function, but specifically for components. For example string
30    /// transcoders.
31    #[cfg(feature = "component-model")]
32    ComponentBuiltin(ComponentBuiltinFunctionIndex),
33}
34
35impl HostCall {
36    /// Returns a 32-bit index for this hostcall.
37    pub const fn index(&self) -> u32 {
38        match self {
39            HostCall::ArrayCall => 0,
40            HostCall::Builtin(i) => 1 + i.index(),
41            #[cfg(feature = "component-model")]
42            HostCall::ComponentLowerImport => 1 + BuiltinFunctionIndex::len(),
43            #[cfg(feature = "component-model")]
44            HostCall::ComponentBuiltin(i) => 2 + BuiltinFunctionIndex::len() + i.index(),
45        }
46    }
47
48    /// Create a `HostCall` from the result of an earlier call to
49    /// `HostCall::index`.
50    pub fn from_index(index: u32) -> Self {
51        let host_call = match index {
52            0 => Self::ArrayCall,
53            _ if index < 1 + BuiltinFunctionIndex::len() => {
54                Self::Builtin(BuiltinFunctionIndex::from_u32(index - 1))
55            }
56            #[cfg(feature = "component-model")]
57            _ if index == 1 + BuiltinFunctionIndex::len() => Self::ComponentLowerImport,
58            #[cfg(feature = "component-model")]
59            _ if index < 2 + BuiltinFunctionIndex::len() + ComponentBuiltinFunctionIndex::len() => {
60                Self::ComponentBuiltin(ComponentBuiltinFunctionIndex::from_u32(
61                    index - 2 - BuiltinFunctionIndex::len(),
62                ))
63            }
64            _ => panic!("bad host call index: {index}"),
65        };
66        debug_assert_eq!(index, host_call.index());
67        host_call
68    }
69}
70
71impl From<BuiltinFunctionIndex> for HostCall {
72    fn from(idx: BuiltinFunctionIndex) -> HostCall {
73        HostCall::Builtin(idx)
74    }
75}
76
77#[cfg(feature = "component-model")]
78impl From<ComponentBuiltinFunctionIndex> for HostCall {
79    fn from(idx: ComponentBuiltinFunctionIndex) -> HostCall {
80        HostCall::ComponentBuiltin(idx)
81    }
82}
wasmtime_environ/hostcall.rs

wasmtime_environ/
hostcall.rs
