extism/node/index.js

import ffi from 'ffi-napi';
import path from 'path';
import url from 'url';

const __dirname = url.fileURLToPath(new URL('.', import.meta.url));

let _functions = {
  extism_plugin_register: ['int32', ['string', 'uint64', 'bool']],
  extism_error: ['char*', ['int32']],
  extism_call: ['int32', ['int32', 'string', 'string', 'uint64']],
  extism_output_length: ['uint64', ['int32']],
  extism_output_get: ['void', ['int32', 'char*', 'uint64']],
  extism_log_file: ['bool', ['string', 'char*']],
  extism_plugin_config: ['void', ['int32', 'char*', 'uint64']],
};

function locate(paths) {
  for (var i = 0; i < paths.length; i++) {
    try {
      return ffi.Library(
        path.join(paths[i], 'libextism'),
        _functions
      )
    } catch (exn) {
      continue;
    }
  }


  throw "Unable to locate libextism";
}

var searchPath =
  [__dirname, "/usr/local/lib", "/usr/lib", path.join(process.env.HOME, ".local")]

if (process.env.EXTISM_PATH) {
  searchPath.unshift(path.join(process.env.EXTISM_PATH, "lib"));
}

var lib = locate(searchPath);
export function set_log_file(filename, level = null) {
  lib.extism_log_file(filename, level)
}

export class Plugin {
  constructor(data, wasi = false, config = null) {
    if (typeof data === "object" && data.wasm) {
      data = JSON.stringify(data);
    }
    let plugin = lib.extism_plugin_register(data, data.length, wasi);
    if (plugin < 0) {
      throw "Unable to load plugin";
    }
    this.id = plugin;

    if (config != null) {
      let s = JSON.stringify(config);
      lib.extism_plugin_config(this.id, s, s.length);
    }
  }

  call(name, input) {
    var rc = lib.extism_call(this.id, name, input, input.length);
    if (rc != 0) {
      var err = lib.extism_error(this.id);
      if (err.length == 0) {
        throw "extism_call failed";
      }
      throw err.toString();
    }

    var out_len = lib.extism_output_length(this.id);
    var buf = new Buffer.alloc(out_len);
    lib.extism_output_get(this.id, buf, out_len);
    return buf;
  }
}