将duktape 2.1.0中的本机C模块加载到

Question

I am still lost after reading the how-to article.

• https://github.com/svaarala/duktape/tree/master/extras/module-node

It is said that

The load callback is a Duktape/C function which takes the resolved module ID and: (1) returns the Ecmascript source code for the module or undefined if there's no source code, eg for pure C modules, (2) can populate module.exports itself, and (3) can replace module.exports.

But when loading a native C module,

• what should be pushed into the value stack? duk_push_undefined(ctx) instead of duk_push_string(ctx, module_source) ?
• what should be returned by the load callback to its caller? return 0 instead of return 1 ?

I tried to call myobject_init (using the default instance in http://wiki.duktape.org/HowtoNativeConstructor.html ) in the load callback cb_load_module . But duktape complains

TypeError: [object Object] not constructable

when I evaluate var MyObject = require("MyObject") , no matter if I

• push undefined into the value stack and return 1,
• or push nothing into the value stack and return 0.

Answer 1

Problem solved. There are a few more details scattered in

• https://github.com/svaarala/duktape/blob/master/doc/c-module-convention.rst
• http://wiki.duktape.org/HowtoModules.html It is about duktape 1.x module loading framework, but it helps understanding 2.x framework.

The most important tricks are:

• The module init function should return a function (constructor is also a function). Do NOT register the function using duk_put_global_string .

   duk_ret_t module_init(duk_context* ctx) { duk_push_c_function(ctx, module_constructor, num_arguments_for_constructor); // set properties for the constructor return 1; // stack: [ ... constructor ] } 

• The function cb_load_module must push the module init function into the value stack, then use duk_call to call it and set module.exports . Do NOT call the module init function directly.

   duk_ret_t cb_load_module(duk_context *ctx) { // stack: [ resolved_id exports module ] ... duk_push_c_function(ctx, module_init, 0); duk_call(ctx, 0); duk_put_prop_string(ctx, 2, "exports"); // obj_idx(module) = 2 return 0; // no .js source for native modules }