js

ZSV in web assembly example

Overview

Two examples here demonstrate how the zsv CSV parser can be compiled to web assembly and called via javascript via a static page in a browser or a Node module.

Most of the operative code is in js/foot.js which effectively just converts between Javascript and emscripten.

Browser

To run the browser demo, run make run. Static files will be built in a subdirectory of the build directory, and a python local https server will be started to serve them on https://127.0.0.1:8888

You can view a demo of the built example here

Node module

To build a node module, run make node. Module files will be placed in node/node_modules/zsv-parser

Node example and test

To run a test via node, run make test. The node module will be built, a sample program will be copied to node/index.js, which reads CSV from stdin and outputs JSON, and a test will be run

Prerequisites

To build, you need emscripten. To run the example web server, you need python3. Unlike some of the other examples, this example does not require that libzsv is already installed

Quick start

1. From the zsv base directory, run configure in your emscripten environment and save the config output to config.emcc:

   emconfigure ./configure CONFIGFILE=config.emcc
   

2. Change back to this directory (examples/wasm), then run emmake make run. You should see output messages ending with Listening on https://127.0.0.1:8888

3. Navigate to https://127.0.0.1:8888. If you get a browser warning, then using Chrome you can type "thisisunsafe" to proceed

4. Click the button to upload a file

Performance

Running ZSV lib from Javascript is still experimental and is not yet fully optimized. Some performance challenges are particular to web assembly + Javascript, e.g. where a lot of string data is being passed between Javascript and the library (see e.g. https://hacks.mozilla.org/2019/08/webassembly-interface-types/).

However, initial results are promising:

• Running only "count", zsv-lib is ~90%+ faster than csv-parser and papaparse
• The more cell data that is fetched, the more this advantage diminishes due to the aforementioned Javascript/wasm memory overhead. Our benchmarking suggests that if the entire row's data is fetched, performance is about on par with both csv-parser and papaparse. If only a portion is fetched, performance is about the same for papaparse, and faster than csv-parser (how much faster being roughly proportional to the difference between count (~90% faster) and the amount of total data fetched)

All the build commands

Separate commands can be used for build, run and clean:

make build
make node
make run
make clean

Add MINIFY=1 to any of the above to generate minified code

To run benchmark tests:

make benchmark

To see all make options:

make