Struct ExportFunctionMetadata 

pub struct ExportFunctionMetadata {
    pub host_env: *mut c_void,
    pub import_init_function_ptr: Option<ImportInitializerFuncPtr>,
    pub host_env_clone_fn: fn(*mut c_void) -> *mut c_void,
    pub host_env_drop_fn: unsafe fn(*mut c_void),
}

Extra metadata about ExportFunctions.

The metadata acts as a kind of manual virtual dispatch. We store the user-supplied WasmerEnv as a void pointer and have methods on it that have been adapted to accept a void pointer.

This struct owns the original host_env, thus when it gets dropped it calls the drop function on it.

Fields

host_env: *mut c_void

This field is stored here to be accessible by Drop.

At the time it was added, it’s not accessed anywhere outside of the Drop implementation. This field is the “master copy” of the env, that is, the original env passed in by the user. Every time we create an Instance we clone this with the host_env_clone_fn field.

Thus, we only bother to store the master copy at all here so that we can free it.

See near_vm_vm::export::VMFunction::vmctx for the version of this pointer that is used by the VM when creating an Instance.

import_init_function_ptr: Option<ImportInitializerFuncPtr>

Function pointer to WasmerEnv::init_with_instance(&mut self, instance: &Instance).

This function is called to finish setting up the environment after we create the api::Instance.

host_env_clone_fn: fn(*mut c_void) -> *mut c_void

A function analogous to Clone::clone that returns a leaked Box.

host_env_drop_fn: unsafe fn(*mut c_void)

The destructor to free the host environment.

Safety

• This function should only be called in when properly synchronized. For example, in the Drop implementation of this type.

Implementations

impl ExportFunctionMetadata

pub unsafe fn new( host_env: *mut c_void, import_init_function_ptr: Option<ImportInitializerFuncPtr>, host_env_clone_fn: fn(*mut c_void) -> *mut c_void, host_env_drop_fn: fn(*mut c_void), ) -> Self

Create an ExportFunctionMetadata type with information about the exported function.

Safety

• the host_env must be Send.
• all function pointers must work on any thread.

Trait Implementations

impl Debug for ExportFunctionMetadata

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Drop for ExportFunctionMetadata

fn drop(&mut self)

Executes the destructor for this type.

impl PartialEq for ExportFunctionMetadata

fn eq(&self, other: &ExportFunctionMetadata) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Send for ExportFunctionMetadata

This can be Send because host_env comes from WasmerEnv which is Send. Therefore all operations should work on any thread.

impl StructuralPartialEq for ExportFunctionMetadata

impl Sync for ExportFunctionMetadata

This data may be shared across threads, drop is an unsafe function pointer, so care must be taken when calling it.