Struct wasmer_vm::InstanceAllocator
source · pub struct InstanceAllocator {
instance_ptr: NonNull<Instance>,
instance_layout: Layout,
offsets: VMOffsets,
consumed: bool,
}
Expand description
This is an intermediate type that manages the raw allocation and
metadata when creating an Instance
.
This type will free the allocated memory if it’s dropped before being used.
It is important to remind that Instance
is dynamically-sized
based on VMOffsets
: The Instance.vmctx
field represents a
dynamically-sized array that extends beyond the nominal end of the
type. So in order to create an instance of it, we must:
- Define the correct layout for
Instance
(size and alignment), - Allocate it properly.
The InstanceAllocator::instance_layout
computes the correct
layout to represent the wanted Instance
.
Then we use this layout to allocate an empty Instance
properly.
Fields§
§instance_ptr: NonNull<Instance>
The buffer that will contain the Instance
and dynamic fields.
instance_layout: Layout
The layout of the instance_ptr
buffer.
offsets: VMOffsets
Information about the offsets into the instance_ptr
buffer for
the dynamic fields.
consumed: bool
Whether or not this type has transferred ownership of the
instance_ptr
buffer. If it has not when being dropped,
the buffer should be freed.
Implementations§
source§impl InstanceAllocator
impl InstanceAllocator
sourcepub fn new(
module: &ModuleInfo,
) -> (Self, Vec<NonNull<VMMemoryDefinition>>, Vec<NonNull<VMTableDefinition>>)
pub fn new( module: &ModuleInfo, ) -> (Self, Vec<NonNull<VMMemoryDefinition>>, Vec<NonNull<VMTableDefinition>>)
Allocates instance data for use with VMInstance::new
.
Returns a wrapper type around the allocation and 2 vectors of
pointers into the allocated buffer. These lists of pointers
correspond to the location in memory for the local memories and
tables respectively. These pointers should be written to before
calling VMInstance::new
.
sourcefn instance_layout(offsets: &VMOffsets) -> Layout
fn instance_layout(offsets: &VMOffsets) -> Layout
Calculate the appropriate layout for the Instance
.
sourceunsafe fn memory_definition_locations(&self) -> Vec<NonNull<VMMemoryDefinition>>
unsafe fn memory_definition_locations(&self) -> Vec<NonNull<VMMemoryDefinition>>
Get the locations of where the local VMMemoryDefinition
s should be stored.
This function lets us create Memory
objects on the host with backing
memory in the VM.
§Safety
Self.instance_ptr
must point to enough memory that all of the offsets inSelf.offsets
point to valid locations in memory, i.e.Self.instance_ptr
must have been allocated bySelf::new
.
sourceunsafe fn table_definition_locations(&self) -> Vec<NonNull<VMTableDefinition>>
unsafe fn table_definition_locations(&self) -> Vec<NonNull<VMTableDefinition>>
Get the locations of where the VMTableDefinition
s should be stored.
This function lets us create [Table
] objects on the host with backing
memory in the VM.
§Safety
Self.instance_ptr
must point to enough memory that all of the offsets inSelf.offsets
point to valid locations in memory, i.e.Self.instance_ptr
must have been allocated bySelf::new
.
sourcepub(crate) fn into_vminstance(self, instance: Instance) -> VMInstance
pub(crate) fn into_vminstance(self, instance: Instance) -> VMInstance
Finish preparing by writing the Instance
into memory, and
consume this InstanceAllocator
.