Rust in the browser with WebAssembly

WebAssembly (wasm) is a compact binary instruction format that every modern browser can run at close to native speed. Rust can compile to it, so the same engine code that runs in the terminal also runs inside a web page, with no server.

How Fishbowl's browser build works:

1. cargo build --target wasm32-unknown-unknown compiles the fishbowl-wasm crate to a .wasm file.
2. wasm-bindgen generates a small JavaScript wrapper, so TypeScript can write new Fishbowl() and db.run(sql) without touching raw memory.
3. Vite bundles the wrapper and the .wasm file into the static site.

Crossing the boundary

JavaScript and wasm share only numbers and raw memory. Passing a string means copying bytes into wasm memory and back out, which wasm-bindgen handles. Fishbowl keeps the boundary narrow: run(sql) returns one JSON string holding every statement's result, the plan trees and the table list. TypeScript parses it into types defined in web/src/engine.ts. A Rust test pins the JSON shape so the two sides cannot drift apart silently.

Integers travel as text inside that JSON. JavaScript numbers lose precision above 2^53, and SQL integers go up to 2^63.

Size

The download is about 700 KB compressed. Most of it is the SQL parser. A separate Cargo profile builds the browser version optimized for size (opt-level = "s") instead of speed.

Code: crates/wasm/src/lib.rs, web/scripts/build-wasm.mjs, web/src/engine.ts.