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@webassemblyjs/wasm-edit

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    @webassemblyjs/wasm-edit

> Rewrite a WASM binary


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23M
increased by7.93%
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739 kB
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Package description

What is @webassemblyjs/wasm-edit?

The @webassemblyjs/wasm-edit package is a toolchain for WebAssembly that allows you to manipulate WASM binaries. It provides functionalities to parse, edit, and generate WASM binaries, making it useful for tasks such as optimizing, instrumenting, or simply understanding the structure of a WebAssembly module.

What are @webassemblyjs/wasm-edit's main functionalities?

Parsing WebAssembly binaries

This feature allows you to parse a WebAssembly binary and turn it into an Abstract Syntax Tree (AST) that can be manipulated or analyzed.

const { decode } = require('@webassemblyjs/wasm-parser');
const { readFileSync } = require('fs');

const wasmBuffer = readFileSync('module.wasm');
const ast = decode(wasmBuffer);

console.log(ast);

Modifying the AST

After parsing a WASM binary into an AST, you can traverse and modify the AST. This example shows how to change the module imports.

const { traverse } = require('@webassemblyjs/ast');

traverse(ast, {
  ModuleImport(path) {
    // Modify the AST by changing module imports
    path.node.module = 'new_module';
  }
});

Generating WebAssembly binaries

Once you have an AST—either from parsing a binary or constructing it manually—you can generate a new WebAssembly binary.

const { encode } = require('@webassemblyjs/wasm-gen');

const newWasmBuffer = encode(ast);

writeFileSync('modified.wasm', newWasmBuffer);

Other packages similar to @webassemblyjs/wasm-edit

Readme

Source

@webassemblyjs/wasm-edit

Rewrite a WASM binary

Replace in-place an AST node in the binary.

Installation

yarn add @webassemblyjs/wasm-edit

Usage

Update:

import { edit } from "@webassemblyjs/wasm-edit";

const binary = [/*...*/];

const visitors = {
  ModuleImport({ node }) {
    node.module = "foo";
    node.name = "bar";
  }
};

const newBinary = edit(binary, visitors);

Replace:

import { edit } from "@webassemblyjs/wasm-edit";

const binary = [/*...*/];

const visitors = {
  Instr(path) {
    const newNode = t.callInstruction(t.indexLiteral(0));
    path.replaceWith(newNode);
  }
};

const newBinary = edit(binary, visitors);

Remove:

import { edit } from "@webassemblyjs/wasm-edit";

const binary = [/*...*/];

const visitors = {
  ModuleExport({ node }) {
    path.remove()
  }
};

const newBinary = edit(binary, visitors);

Insert:

import { add } from "@webassemblyjs/wasm-edit";

const binary = [/*...*/];

const newBinary = add(actualBinary, [
  t.moduleImport("env", "mem", t.memory(t.limit(1)))
]);

Providing the AST

Providing an AST allows you to handle the decoding yourself, here is the API:

addWithAST(Program, ArrayBuffer, Array<Node>): ArrayBuffer;
editWithAST(Program, ArrayBuffer, visitors): ArrayBuffer;

Note that the AST will be updated in-place.

FAQs

Last updated on 13 Mar 2024

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