Isolating parts of the library using Terser

[belohlavek]

Dear @101arrowz

Hey! I need to isolate parts of this library, preferably keeping the type annotations, but a JS output would be ok too.

For example, I want to "dump" the Inflate and Deflate functions into their own modules.
There are several reasons why I want to do this, including (but not limited to) having an easier time running the code through TypescriptToLua.

Normally I would just do this manually, but having all the exported members in a single file, plus using short names makes the code a bit hard to follow (at least for my extraction purposes).

Can some of this process be automated using Terser? It could be similar to those small bundles which only export a limited set of features. Is it possible to get a clean un-minified output?

Do you have a config or template project to share? I read in another thread that you already have some of these small builds but chose not to provide them due to the (understandably) wide range of possible configurations. I want to generate one of these configurations myself.

Thanks for the great lib!

[101arrowz]

To generate custom builds myself, I usually run the build through terser. You can just paste the CJS build into a text editor, then find+replace all the exports with nothing (e.g. with the regex exports.*;$ and manually removing exports.FlateErrorCode). Now, manually write the exports you want at the bottom (e.g. exports.unzipSync = unzipSync;), then plug it through terser (since I'm lazy I use terser-online). Now you have a minified file that contains the exports, and you can use the TypeScript declaration file provided with fflate to plug it through TypescriptToLua.

Unrelated, but I'm curious why you don't just use bindings to native Zlib written in Lua. They would probably be faster than fflate ported to Lua (since fflate includes a LOT of micro-optimizations that work best in JavaScript). Also, my own tests on this method don't yield working code because TypescriptToLua isn't actually very accurate: fflate assumes that 0 is falsy in a lot of places, but TypescriptToLua does not.

[belohlavek]

Whoops, good catch on that TypescriptToLua detail, probably saved my quite a bit of time, thank you.
The reason I was considering it is that I can't access or create bindings in the sandboxed environment this lua script would run on (basically an extension for another software). There's another pure lua library but I haven't yet gotten it to inflate correctly with fflate. It may be my lack of lua knowledge but it seems to be focused on strings, while I need a simple array-like structure for numbers. I will probably investigate the project further to understand how it's implemented internally and try to feed the lua table (array) directly. Just to be clear, this is me incorrectly using that lua library, not a problem with fflate.

As I mentioned before, I can still make use of isolating parts of fflate for other purposes, so thanks for the tips!

[101arrowz]

The library you linked should work; it returns binary strings instead of an array, and seems to accept binary strings as well. In a binary string, basically the character codes in the string correspond to the byte values you want. You can probably convert an array of numbers to a binary string pretty easily in Lua, you're looking for the equivalent of String.fromCharCode(code) in JS. To do the reverse, look for the equivalent of String.charCodeAt.

fflate has binary string manipulation functions as well: strToU8(binstring, true) converts binary strings to Uint8Array and strFromU8(someUint8ArrayObject, true) converts Uint8Array to binary strings.