Crate holochain_wasmer_guest
source · [−]Re-exports
pub extern crate holochain_serialized_bytes;Modules
Macros
unidiomatic way to derive default trait implementations of TryFrom in/out of SerializedBytes
A simple macro to wrap
return_err_ptr in an analogy to the native rust ?.Helper macro for returning an error from a WASM.
Structs
A Canonical Serialized Bytes representation for data
If you have a data structure that needs a canonical byte representation use this
Always round-trip through SerializedBytes via. a single TryFrom implementation.
This ensures that the internal bytes of SerializedBytes are indeed canonical.
The corrolary is that if bytes are NOT wrapped in SerializedBytes we can assume they are NOT
canonical.
Typically we need a canonical serialization when data is to be handled at the byte level by
independently implemented and maintained systems.
UnsafeBytes the only way to implement a custom round trip through bytes for SerializedBytes
It is intended to be an internal implementation in TryFrom implementations
The assumption is that any code using UnsafeBytes is NOT valid messagepack data
This allows us to enforce that all data round-tripping through SerializedBytes is via TryFrom
and also allow for custom non-messagepack canonical representations of data types.
Wraps a WasmErrorInner with a file and line number.
The easiest way to generate this is with the
wasm_error! macro that will
insert the correct file/line and can create strings by forwarding args to
the format! macro.Enums
Enum of all possible ERROR states that wasm can encounter.
Traits
A data structure that can be deserialized from any data format supported
by Serde.
A data structure that can be serialized into any data format supported
by Serde.
Simple and safe type conversions that may fail in a controlled
way under some circumstances. It is the reciprocal of
TryInto.An attempted conversion that consumes
self, which may or may not be
expensive.Functions
Receive arguments from the host.
The guest sets the type
O that the host needs to match.
If deserialization fails then a GuestPtr to a WasmError::Deserialize is returned.
The guest should immediately return an Err back to the host.
The WasmError::Deserialize enum contains the bytes that failed to deserialize so the host can
unambiguously provide debug information.Given an extern that we expect the host to provide:
Given a pointer and a length, return a
u64 merged GuestPtrLen.
Works via a simple bitwise shift to move the pointer to high bits then OR
the length into the low bits.Convert a
WasmError to a GuestPtrLen as best we can. This is not
necessarily straightforward as the serialization process can error recursively.
In the worst case we can’t even serialize an enum variant, in which case we panic.
The casts from usize to u32 are safe as long as the guest code is compiled
for wasm32-unknown-unknown target.Convert any serializable value into a
GuestPtr that can be returned to the host.
The host is expected to know how to consume and deserialize it.Given a merged
GuestPtrLen, split out a u32 pointer and length.
Performs the inverse of merge_u64. Takes the low u32 bits as the length
then shifts the 32 high bits down and takes those as the pointer.Type Definitions
A
WasmSize that points to a position in wasm linear memory that the host
and guest are sharing to communicate across function calls.Enough bits to fit a pointer and length into so we can return it. The externs
defined as “C” don’t support multiple return values (unlike wasm). The native
Rust support for wasm externs is not stable at the time of writing.
A
WasmSize integer that represents the size of bytes to read/write to memory.Something like
usize for wasm.
Wasm has a memory limit of 4GB so offsets and lengths fit in u32.