build.sh

#!/bin/bash
git clone https://github.com/just-js/lo.git
cd lo/
make lo
export LO_HOME=$(pwd)
./lo build binding bestlines
cd ..
lo/lo build runtime test-dlopen
./test-dlopen 

test-dlopen.config.js

const bindings = ['core']
const libs = []
const target = 'test-dlopen' 
const index = 'test-dlopen.js'
const embeds = ['lib/bestlines/bestlines.so']

export default { bindings, libs, embeds, target, index }

test-dlopen.js

import { stringify } from 'lib/stringify.js'

// create a memfd. the name can be whatever you want and is not shared among processes
const fd = lo.core.memfd_create('/vfs/bestlines.so', lo.core.MFD_CLOEXEC)
// look up the start and size of the embedded shared library
const start = lo.core.dlsym(0, '_binary_lib_bestlines_bestlines_so_start')
const size = lo.core.dlsym(0, '_binary_lib_bestlines_bestlines_so_end') - start
// wrap the memory (zero copy) in an arraybuffer. by default, the memory won't 
// be freed when the ab goes out of scope, which is what we want in this case
const b = new Uint8Array(lo.wrap_memory(start, size))
// if we just want to load it from disk, we can do this
//const b = lo.core.read_file('./lib/bestlines/bestlines.so')
// write the shared library contents to the memfd
lo.core.write(fd, b, b.length)
// use dlopen to open the shared library from the procfs virtual file that is
// created for the memfd
const handle = lo.core.dlopen(`/proc/self/fd/${fd}`, 2)
// lookup the binding register symbol in the shared library and load the
// binding using it
const lib = lo.library(lo.core.dlsym(handle, '_register_bestlines'))
// we now have a "lo" binding loaded and ready to use. the same as loading a
// shared library from disk
console.log(stringify(lib))

/*
# dumps the bestlines library to the console

{
  bestlines: {
    bestline: "bestline (...0)",
    bestline_raw: "bestline_raw (...0)",
    cls: "cls (...0)",
    add: "add (...0)",
    save: "save (...0)",
    load: "load (...0)"
  }
}
*/