Crate wasm_encoder

A WebAssembly encoder.

The main builder is the Module. You can build a section with a section-specific builder, like TypeSection or ImportSection, and then add it to the module with Module::section. When you are finished building the module, call either Module::as_slice or Module::finish to get the encoded bytes. The former gives a shared reference to the underlying bytes as a slice, while the latter gives you ownership of them as a vector.

Example

If we wanted to build this module:

(module
  (type (func (param i32 i32) (result i32)))
  (func (type 0)
    local.get 0
    local.get 1
    i32.add)
  (export "f" (func 0)))

then we would do this:

use wasm_encoder::{
    CodeSection, Export, ExportSection, Function, FunctionSection, Instruction,
    Module, TypeSection, ValType,
};

let mut module = Module::new();

// Encode the type section.
let mut types = TypeSection::new();
let params = vec![ValType::I32, ValType::I32];
let results = vec![ValType::I32];
types.function(params, results);
module.section(&types);

// Encode the function section.
let mut functions = FunctionSection::new();
let type_index = 0;
functions.function(type_index);
module.section(&functions);

// Encode the export section.
let mut exports = ExportSection::new();
exports.export("f", Export::Function(0));
module.section(&exports);

// Encode the code section.
let mut codes = CodeSection::new();
let locals = vec![];
let mut f = Function::new(locals);
f.instruction(Instruction::LocalGet(0));
f.instruction(Instruction::LocalGet(1));
f.instruction(Instruction::I32Add);
f.instruction(Instruction::End);
codes.function(&f);
module.section(&codes);

// Extract the encoded Wasm bytes for this module.
let wasm_bytes = module.finish();

// We generated a valid Wasm module!
assert!(wasmparser::validate(&wasm_bytes).is_ok());

Modules

encoders

Low-level encoders.

Structs

AliasSection	An encoder for the alias section.
CodeSection	An encoder for the code section.
CustomSection	A custom section holding arbitrary data.
DataCountSection	An encoder for the data count section.
DataSection	An encoder for the data section.
DataSegment	A segment in the data section.
DataSymbolDefinition	The definition of a data symbol within a symbol table.
ElementSection	An encoder for the element section.
ElementSegment	An element segment in the element section.
ExportSection	An encoder for the export section.
Function	An encoder for a function body within the code section.
FunctionSection	An encoder for the function section.
GlobalSection	An encoder for the global section.
GlobalType	A global’s type.
ImportSection	An encoder for the import section.
InstanceSection	An encoder for the instance section.
Limits	Limits for a table or memory.
LinkingSection	An encoder for the linking custom section.
MemArg	The immediate for a memory instruction.
MemorySection	An encoder for the memory section.
MemoryType	A memory’s type.
Module	A Wasm module that is being encoded.
ModuleSection	An encoder for the module section.
RawSection	A section made up of uninterpreted, raw bytes.
StartSection	An encoder for the start section.
SymbolTable	A subsection of the linking custom section that provides extra information about the symbols present in this Wasm object file.
TableSection	An encoder for the table section.
TableType	A table’s type.
TypeSection	An encoder for the type section.

Enums

BlockType	The type for a block/if/loop.
DataSegmentMode	A data segment’s mode.
Element	An element in a segment in the element section.
ElementMode	An element segment’s mode.
Elements	A sequence of elements in a segment in the element section.
EntityType	The type of an entity.
Export	A WebAssembly export.
Instruction	WebAssembly instructions.
ItemKind	Kinds of WebAssembly items
SectionId	Known section IDs.
ValType	The type of a value.

Traits

Section

A WebAssembly section.