Struct holochain_wasmer_host::prelude::WasmPtr [−][src]
Expand description
A zero-cost type that represents a pointer to something in Wasm linear memory.
This type can be used directly in the host function arguments:
pub fn host_import(memory: Memory, ptr: WasmPtr<u32>) { let derefed_ptr = ptr.deref(&memory).expect("pointer in bounds"); let inner_val: u32 = derefed_ptr.get(); println!("Got {} from Wasm memory address 0x{:X}", inner_val, ptr.offset()); // update the value being pointed to derefed_ptr.set(inner_val + 1); }
This type can also be used with primitive-filled structs, but be careful of
guarantees required by ValueType
.
#[derive(Copy, Clone, Debug)] #[repr(C)] struct V3 { x: f32, y: f32, z: f32 } // This is safe as the 12 bytes represented by this struct // are valid for all bit combinations. unsafe impl ValueType for V3 { } fn update_vector_3(memory: Memory, ptr: WasmPtr<V3>) { let derefed_ptr = ptr.deref(&memory).expect("pointer in bounds"); let mut inner_val: V3 = derefed_ptr.get(); println!("Got {:?} from Wasm memory address 0x{:X}", inner_val, ptr.offset()); // update the value being pointed to inner_val.x = 10.4; derefed_ptr.set(inner_val); }
Implementations
Methods relevant to all types of WasmPtr
.
Methods for WasmPtr
s to data that can be dereferenced, namely to types
that implement ValueType
, meaning that they’re valid for all possible
bit patterns.
Dereference the WasmPtr
getting access to a &Cell<T>
allowing for
reading and mutating of the inner value.
This method is unsound if used with unsynchronized shared memory. If you’re unsure what that means, it likely does not apply to you. This invariant will be enforced in the future.
Mutably dereference this WasmPtr
getting a &mut Cell<T>
allowing for
direct access to a &mut T
.
Safety
- This method does not do any aliasing checks: it’s possible to create
&mut T
that point to the same memory. You should ensure that you have exclusive access to Wasm linear memory before calling this method.
Methods for WasmPtr
s to arrays of data that can be dereferenced, namely to
types that implement ValueType
, meaning that they’re valid for all
possible bit patterns.
Dereference the WasmPtr
getting access to a &[Cell<T>]
allowing for
reading and mutating of the inner values.
This method is unsound if used with unsynchronized shared memory. If you’re unsure what that means, it likely does not apply to you. This invariant will be enforced in the future.
Mutably dereference this WasmPtr
getting a &mut [Cell<T>]
allowing for
direct access to a &mut [T]
.
Safety
- This method does not do any aliasing checks: it’s possible to create
&mut T
that point to the same memory. You should ensure that you have exclusive access to Wasm linear memory before calling this method.
Get a UTF-8 string from the WasmPtr
with the given length.
Note that . The
underlying data can be mutated if the Wasm is allowed to execute or
an aliasing WasmPtr
is used to mutate memory.
Safety
This method returns a reference to Wasm linear memory. The underlying
data can be mutated if the Wasm is allowed to execute or an aliasing
WasmPtr
is used to mutate memory.
str
has invariants that must not be broken by mutating Wasm memory.
Thus the caller must ensure that the backing memory is not modified
while the reference is held.
Additionally, if memory
is dynamic, the caller must also ensure that memory
is not grown while the reference is held.
Get a UTF-8 String
from the WasmPtr
with the given length.
an aliasing WasmPtr
is used to mutate memory.
Get a UTF-8 string from the WasmPtr
, where the string is nul-terminated.
Note that this does not account for UTF-8 strings that contain nul themselves,
WasmPtr::get_utf8_str
has to be used for those.
Safety
This method behaves similarly to WasmPtr::get_utf8_str
, all safety invariants on
that method must also be upheld here.
Get a UTF-8 String
from the WasmPtr
, where the string is nul-terminated.
Note that this does not account for UTF-8 strings that contain nul themselves,
WasmPtr::get_utf8_string
has to be used for those.
Trait Implementations
Auto Trait Implementations
impl<T, Ty> RefUnwindSafe for WasmPtr<T, Ty> where
T: RefUnwindSafe,
Ty: RefUnwindSafe,
impl<T, Ty> UnwindSafe for WasmPtr<T, Ty> where
T: UnwindSafe,
Ty: UnwindSafe,
Blanket Implementations
type ArchivedMetadata = ()
type ArchivedMetadata = ()
The archived version of the pointer metadata for this type.
pub fn pointer_metadata(
&<T as ArchivePointee>::ArchivedMetadata
) -> <T as Pointee>::Metadata
pub fn pointer_metadata(
&<T as ArchivePointee>::ArchivedMetadata
) -> <T as Pointee>::Metadata
Converts some archived metadata to the pointer metadata for itself.
Mutably borrows from an owned value. Read more
Compare self to key
and return true
if they are equal.
Instruments this type with the provided Span
, returning an
Instrumented
wrapper. Read more
pub fn vzip(self) -> V
type CStruct = S1<A1>
type CStruct = S1<A1>
The C type (a struct) that can hold/represent all the represented values. Read more
Constructs Self
based on an array of values.
Constructs Self
based on a slice of values. Read more
Builds and returns an array of type Array
from a tuple
(list) of values. Read more
Allocates and return an empty array of type Array
that
will hold a tuple (list) of values, usually to hold the
returned values of a WebAssembly function call. Read more
Builds a tuple (list) of values from a C struct of type
CStruct
. Read more
Builds and returns a C struct of type CStruct
from a
tuple (list) of values. Read more