85 lines
2.3 KiB
JavaScript
85 lines
2.3 KiB
JavaScript
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'use strict';
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/**
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* Module dependencies.
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*/
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const ref = require('ref-napi');
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const CIF = require('./cif');
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const assert = require('assert');
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const debug = require('debug')('ffi:Callback');
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const _Callback = require('./bindings').Callback;
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// Function used to report errors to the current process event loop,
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// When user callback function gets gced.
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function errorReportCallback (err) {
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if (err) {
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process.nextTick(function () {
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if (typeof err === 'string') {
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throw new Error(err);
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} else {
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throw err;
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}
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})
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}
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}
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/**
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* Turns a JavaScript function into a C function pointer.
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* The function pointer may be used in other C functions that
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* accept C callback functions.
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*/
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function Callback (retType, argTypes, abi, func) {
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debug('creating new Callback');
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if (typeof abi === 'function') {
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func = abi;
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abi = undefined;
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}
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// check args
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assert(!!retType, 'expected a return "type" object as the first argument');
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assert(Array.isArray(argTypes), 'expected Array of arg "type" objects as the second argument');
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assert.equal(typeof func, 'function', 'expected a function as the third argument');
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// normalize the "types" (they could be strings, so turn into real type
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// instances)
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retType = ref.coerceType(retType);
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argTypes = argTypes.map(ref.coerceType);
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// create the `ffi_cif *` instance
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const cif = CIF(retType, argTypes, abi);
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const argc = argTypes.length;
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const callback = _Callback(cif, retType.size, argc, errorReportCallback, (retval, params) => {
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debug('Callback function being invoked')
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try {
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const args = [];
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for (var i = 0; i < argc; i++) {
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const type = argTypes[i];
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const argPtr = params.readPointer(i * ref.sizeof.pointer, type.size);
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argPtr.type = type;
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args.push(argPtr.deref());
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}
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// Invoke the user-given function
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const result = func.apply(null, args);
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try {
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ref.set(retval, 0, result, retType);
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} catch (e) {
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e.message = 'error setting return value - ' + e.message;
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throw e;
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}
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} catch (e) {
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return e;
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}
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});
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// store reference to the CIF Buffer so that it doesn't get
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// garbage collected before the callback Buffer does
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callback._cif = cif;
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return callback;
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}
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module.exports = Callback;
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