#[repr(C)]
pub struct Instance { }
Available on crate feature runtime
only.
An instantiated WebAssembly module.
This type represents the instantiation of a Module
. Once instantiated you can access the exports
which are of type Extern
and provide the ability to call functions, set globals, read memory, etc. When interacting with any wasm code you’ll want to make an Instance
to call any code or execute anything.
Instances are owned by a Store
which is passed in at creation time. It’s recommended to create instances with Linker::instantiate
or similar Linker
methods, but a more low-level constructor is also available as Instance::new
.
Creates a new Instance
from the previously compiled Module
and list of imports
specified.
This method instantiates the module
provided with the imports
, following the procedure in the core specification to instantiate. Instantiation can fail for a number of reasons (many specified below), but if successful the start
function will be automatically run (if specified in the module
) and then the Instance
will be returned.
Per the WebAssembly spec, instantiation includes running the module’s start function, if it has one (not to be confused with the _start
function, which is not run).
Note that this is a low-level function that just performs an instantiation. See the Linker
struct for an API which provides a convenient way to link imports and provides automatic Command and Reactor behavior.
The entries in the list of imports
are intended to correspond 1:1 with the list of imports returned by Module::imports
. Before calling Instance::new
you’ll want to inspect the return value of Module::imports
and, for each import type, create an Extern
which corresponds to that type. These Extern
values are all then collected into a list and passed to this function.
Note that this function is intentionally relatively low level. For an easier time passing imports by doing name-based resolution it’s recommended to instead use the Linker
type.
This function can fail for a number of reasons, including, but not limited to:
imports
provided doesn’t match the number of imports returned by the module
’s Module::imports
method.Extern
doesn’t match the corresponding ExternType
entry that it maps to.start
function in the instance, if present, traps.When instantiation fails it’s recommended to inspect the return value to see why it failed, or bubble it upwards. If you’d like to specifically check for trap errors, you can use error.downcast::<Trap>()
. For more about error handling see the Trap
documentation.
This function will panic if called with a store associated with a asynchronous config
. This function will also panic if any Extern
supplied is not owned by store
.
Available on crate feature async
only.
Same as Instance::new
, except for usage in [asynchronous stores].
For more details about this function see the documentation on Instance::new
. The only difference between these two methods is that this one will asynchronously invoke the wasm start function in case it calls any imported function which is an asynchronous host function (e.g. created with Func::new_async
.
This function will panic if called with a store associated with a synchronous config
. This is only compatible with stores associated with an asynchronous config
.
This function will also panic, like Instance::new
, if any Extern
specified does not belong to store
.
Get this instance’s module.
SourceReturns the list of exported items from this Instance
.
Panics if store
does not own this instance.
Looks up an exported Extern
value by name.
This method will search the module for an export named name
and return the value, if found.
Returns None
if there was no export named name
.
Panics if store
does not own this instance.
get_export
take a mutable context?
This method requires a mutable context because an instance’s exports are lazily populated, and we cache them as they are accessed. This makes instantiating a module faster, but also means this method requires a mutable context.
SourceLooks up an exported Extern
value by a ModuleExport
value.
This is similar to Instance::get_export
but uses a ModuleExport
value to avoid string lookups where possible. ModuleExport
s can be obtained by calling Module::get_export_index
on the Module
that this instance was instantiated with.
This method will search the module for an export with a matching entity index and return the value, if found.
Returns None
if there was no export with a matching entity index.
Panics if store
does not own this instance.
Looks up an exported Func
value by name.
Returns None
if there was no export named name
, or if there was but it wasn’t a function.
Panics if store
does not own this instance.
Looks up an exported Func
value by name and with its type.
This function is a convenience wrapper over Instance::get_func
and Func::typed
. For more information see the linked documentation.
Returns an error if name
isn’t a function export or if the export’s type did not match Params
or Results
Panics if store
does not own this instance.
Looks up an exported Table
value by name.
Returns None
if there was no export named name
, or if there was but it wasn’t a table.
Panics if store
does not own this instance.
Looks up an exported Memory
value by name.
Returns None
if there was no export named name
, or if there was but it wasn’t a memory.
Panics if store
does not own this instance.
Looks up an exported SharedMemory
value by name.
Returns None
if there was no export named name
, or if there was but it wasn’t a shared memory.
Panics if store
does not own this instance.
Looks up an exported Global
value by name.
Returns None
if there was no export named name
, or if there was but it wasn’t a global.
Panics if store
does not own this instance.
Looks up a tag Tag
by name.
Returns None
if there was no export named name
, or if there was but it wasn’t a tag.
Panics if store
does not own this instance.
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