Method realloc

crates/wasmtime/src/runtime/component/func/options.rs:140–189

Invokes the memory allocation function (which is style after `realloc`) with the specified parameters. # Panics This will panic if realloc hasn't been configured for this lowering via its canonical options.

(
        &mut self,
        old: usize,
        old_size: usize,
        old_align: u32,
        new_size: usize,
    )

    /// This will panic if realloc hasn't been configured for this lowering via
    /// its canonical options.
    pub fn realloc(
        &mut self,
        old: usize,
        old_size: usize,
        old_align: u32,
        new_size: usize,
    ) -> Result<usize> {
        assert!(self.allow_realloc);

        let (component, store) = self.instance.component_and_store_mut(self.store.0);
        let instance = self.instance.id().get(store);
        let options = &component.env_component().options[self.options];
        let realloc_ty = component.realloc_func_ty();
        let realloc = match options.data_model {
            CanonicalOptionsDataModel::Gc {} => unreachable!(),
            CanonicalOptionsDataModel::LinearMemory(m) => m.realloc.unwrap(),
        };
        let realloc = instance.runtime_realloc(realloc);

        let params = (
            u32::try_from(old)?,
            u32::try_from(old_size)?,
            old_align,
            u32::try_from(new_size)?,
        );

        type ReallocFunc = crate::TypedFunc<(u32, u32, u32, u32), u32>;

        // Invoke the wasm malloc function using its raw and statically known
        // signature.
        let result = unsafe {
            ReallocFunc::call_raw(&mut StoreContextMut(store), &realloc_ty, realloc, params)?
        };

        if result % old_align != 0 {
            bail!("realloc return: result not aligned");
        }
        let result = usize::try_from(result)?;

        if self
            .as_slice_mut()
            .get_mut(result..)
            .and_then(|s| s.get_mut(..new_size))
            .is_none()
        {
            bail!("realloc return: beyond end of memory")
        }

        Ok(result)
    }

    /// Returns a fixed mutable slice of memory `N` bytes large starting at
    /// offset `N`, panicking on out-of-bounds.