@teradataprebuilt/fastcall-linux-node-v59/lib/FastCallback.js

fastcall - Very fast, asynchronous, dyncall based foreign function interface library for Node.js

/*
Copyright 2016 Gábor Mező (gabor.mezo@outlook.com)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

'use strict';
const _ = require('lodash');
const assert = require('assert');
const verify = require('./verify');
const a = verify.a;
const ert = verify.ert;
const native = require('./native');
const util = require('util');
const FunctionDefinition = require('./FunctionDefinition');
const ref = require('./ref-libs/ref');

class FastCallback extends FunctionDefinition {
    constructor(library, def) {
        assert(_.isObject(library), '"library" is not an object.');
        super(library, def);
        this.library = library;
        this._def = new FunctionDefinition(library, def);
        this._processArgs = null;
        this._setResult = null;
        this._type.callback = this;
    }

    initialize() {
        this._execute = this._makeExecuteMethod();
    }

    get execute() {
        assert(this._execute, 'FastCallback is not initialized.');
        return this._execute;
    }

    getFactory() {
        const factory = value => this.makePtr(value);
        factory.callback = this;
        factory.type = this.type;
        return factory;
    }

    makePtr(value) {
        if (value) {
            if (value.callback === this) {
                return value;
            }
            if (_.isFunction(value)) {
                const ptr = native.callback.makePtr(this, this.library._loop, this.signature, this.execute, value);
                a&&ert(ptr.callback === this);
                ptr.type = this.type;
                return ptr;
            }
            if (value instanceof Buffer) {
                if (value.type === undefined) {
                    value.type = this.type;
                }
                if (value.callback === undefined) {
                    value.callback = this;
                }
                if (value.callback === this) {
                    return value;
                }
                throw new TypeError('Buffer is not a callback pointer.');
            }
        }
        else if (value === null) {
            return null;
        }
        throw new TypeError('Cannot make callback from: ' + value);
    }

    _makeExecuteMethod() {
        const processArgsFunc = this._makeProcessArgsFunc();
        const resultTypeCode = this.resultType.code;
        const callArgs = new Array(this.args.length);
        if (resultTypeCode !== 'v') {
            const setResultFunc = this._findSetResultFunc();
            return (argsPtr, resultPtr, func) => {
                processArgsFunc(argsPtr, callArgs);
                const result = func(...callArgs);
                setResultFunc(resultPtr, result);
            };
        }
        return (argsPtr, resultPtr, func) => {
            processArgsFunc(argsPtr, callArgs);
            func(...callArgs);
        };
    }

    _makeProcessArgsFunc() {
        const processArgFuncs = this.args.map(arg => this._findProcessArgFunc(arg.type));
        const funcArgs = ['argsPtr', 'callArgs'];
        let funcBody = '';
        for (let i = 0; i < processArgFuncs.length; i++) {
            funcBody += `callArgs[${ i }] = this.processArgFunc${ i }(argsPtr);`;
        }

        class Ctx {
            constructor(callback) {
                let i = 0;
                for (const processArgFunc of processArgFuncs) {
                    this['processArgFunc' + i++] = processArgFunc.func;
                }
            }
        }

        const ctx = new Ctx(this);

        let innerFunc;
        try {
            innerFunc = new Function(...funcArgs.concat([funcBody]));
        }
        catch (err) {
            throw Error('Invalid function body: ' + funcBody);
        }

        const func = function () {
            return innerFunc.apply(ctx, arguments);
        };
        func.callback = this;
        return func;
    }

     _findProcessArgFunc(type) {
        return this.findFastcallFunc(native.callback, 'arg', type);
    }

    _findSetResultFunc() {
        return this.findFastcallFunc(native.callback, 'set', this.resultType).func;
    }
}

module.exports = FastCallback;