js-spark-md5 VS hermes

ActiveStorage uses the SparkMD5 library for MD5 hashing. I don't know enough about the library to know if MD5 is necessary or if we could use SHA-x hashing or similar. SparkMD5 is roughly 2.5kb and ActiveStorage is ~5kb overall, which means MD5 hashing accounts for roughly half the library.

However, RN has still a lack of binary support. Unlike NodeJS, RN doesn't come with native modules for dealing with binary data out of the box, like crypto and Buffer. When it comes to processing binary data, calculating a digest hash like SHA-1 and MD5 and converting from/to hex and base64 are popular tasks. To accomplish those tasks, you have to use JavaScript libraries like spark-md5 and buffer. If you need crypto module, you have to install rn-nodeify and a bunch of polyfill libraries, which eventually messes up your project and makes it hard to maintain. So, implementing the end-to-end encryption in React Native has been a big challenge for me.

Hermes is a big one as well: low startup latency, low memory

https://hermesengine.dev/

Hermes

InstagramBundle.js.hbc.spk.xz is likely a compressed version of Hermes bytecode (js.hbc)"

In React Native's case, it uses an engine called Hermes:

📜 I made JSON.parse() 2x faster: Radek proposes to improve the performance of Hermes by using very fast C++ libs based on SIMD instructions. Interesting to read even if you don't use React-Native. Ongoing discussions on the Hermes PR.

Thanks! There's a preliminary PR with a discussion here: https://github.com/facebook/hermes/pull/933 (and broader context here: https://github.com/facebook/hermes/issues/811 ). But we'll see if there's any interest on Hermes' side to merging it. They definitely want to improve the parser, but it's unclear to me if they want to take on the simdjson/simdutf dependencies.