Jonathan G

1595192385

Aurora OS developers included a memcpy fix in Glibc

The developers of the AuroraOS mobile operating system (a fork of the Sailfish operating system, developed by the Open Mobile Platform company) shared a solution for a vulnerability they detected in memcpy. The removal of the critical vulnerability (CVE-2020-6096) in Glibc, which manifests itself only in the ARMv7 platform.

Orginal article here: https://d0z.me/aurora-os-developers-included-memcpy-fix-in-glibc/

#linux #security

What is GEEK

Buddha Community

Fredy  Larson

Fredy Larson

1595059664

How long does it take to develop/build an app?

With more of us using smartphones, the popularity of mobile applications has exploded. In the digital era, the number of people looking for products and services online is growing rapidly. Smartphone owners look for mobile applications that give them quick access to companies’ products and services. As a result, mobile apps provide customers with a lot of benefits in just one device.

Likewise, companies use mobile apps to increase customer loyalty and improve their services. Mobile Developers are in high demand as companies use apps not only to create brand awareness but also to gather information. For that reason, mobile apps are used as tools to collect valuable data from customers to help companies improve their offer.

There are many types of mobile applications, each with its own advantages. For example, native apps perform better, while web apps don’t need to be customized for the platform or operating system (OS). Likewise, hybrid apps provide users with comfortable user experience. However, you may be wondering how long it takes to develop an app.

To give you an idea of how long the app development process takes, here’s a short guide.

App Idea & Research

app-idea-research

_Average time spent: two to five weeks _

This is the initial stage and a crucial step in setting the project in the right direction. In this stage, you brainstorm ideas and select the best one. Apart from that, you’ll need to do some research to see if your idea is viable. Remember that coming up with an idea is easy; the hard part is to make it a reality.

All your ideas may seem viable, but you still have to run some tests to keep it as real as possible. For that reason, when Web Developers are building a web app, they analyze the available ideas to see which one is the best match for the targeted audience.

Targeting the right audience is crucial when you are developing an app. It saves time when shaping the app in the right direction as you have a clear set of objectives. Likewise, analyzing how the app affects the market is essential. During the research process, App Developers must gather information about potential competitors and threats. This helps the app owners develop strategies to tackle difficulties that come up after the launch.

The research process can take several weeks, but it determines how successful your app can be. For that reason, you must take your time to know all the weaknesses and strengths of the competitors, possible app strategies, and targeted audience.

The outcomes of this stage are app prototypes and the minimum feasible product.

#android app #frontend #ios app #minimum viable product (mvp) #mobile app development #web development #android app development #app development #app development for ios and android #app development process #ios and android app development #ios app development #stages in app development

Mitchel  Carter

Mitchel Carter

1602979200

Developer Career Path: To Become a Team Lead or Stay a Developer?

For a developer, becoming a team leader can be a trap or open up opportunities for creating software. Two years ago, when I was a developer, I was thinking, “I want to be a team leader. It’s so cool, he’s in charge of everything and gets more money. It’s the next step after a senior.” Back then, no one could tell me how wrong I was. I had to find it out myself.

I Got to Be a Team Leader — Twice

I’m naturally very organized. Whatever I do, I try to put things in order, create systems and processes. So I’ve always been inclined to take on more responsibilities than just coding. My first startup job, let’s call it T, was complete chaos in terms of development processes.

Now I probably wouldn’t work in a place like that, but at the time, I enjoyed the vibe. Just imagine it — numerous clients and a team leader who set tasks to the developers in person (and often privately). We would often miss deadlines and had to work late. Once, my boss called and asked me to come back to work at 8 p.m. to finish one feature — all because the deadline was “the next morning.” But at T, we were a family.

We also did everything ourselves — or at least tried to. I’ll never forget how I had to install Ubuntu on a rack server that we got from one of our investors. When I would turn it on, it sounded like a helicopter taking off!

At T, I became a CTO and managed a team of 10 people. So it was my first experience as a team leader.

Then I came to work at D — as a developer. And it was so different in every way when it came to processes.

They employed classic Scrum with sprints, burndown charts, demos, story points, planning, and backlog grooming. I was amazed by the quality of processes, but at first, I was just coding and minding my own business. Then I became friends with the Scrum master. I would ask him lots of questions, and he would willingly answer them and recommend good books.

My favorite was Scrum and XP from the Trenches by Henrik Kniberg. The process at D was based on its methods. As a result, both managers and sellers knew when to expect the result.

Then I joined Skyeng, also as a developer. Unlike my other jobs, it excels at continuous integration with features shipped every day. Within my team, we used a Kanban-like method.

We were also lucky to have our team leader, Petya. At our F2F meetings, we could discuss anything, from missing deadlines to setting up a task tracker. Sometimes I would just give feedback or he would give me advice.

That’s how Petya got to know I’d had some management experience at T and learned Scrum at D.

So one day, he offered me to host a stand-up.

#software-development #developer #dev-team-leadership #agile-software-development #web-development #mobile-app-development #ios-development #android-development

Joel  Hawkins

Joel Hawkins

1632538163

Elk: A Low Footprint JavaScript Engine for Embedded Systems

Elk: a tiny JS engine for embedded systems

Elk is a tiny embeddable JavaScript engine that implements a small but usable subset of ES6. It is designed for microcontroller development. Instead of writing firmware code in C/C++, Elk allows to develop in JavaScript. Another use case is providing customers with a secure, protected scripting environment for product customisation.

Elk features include:

  • Cross platform. Works anywhere from 8-bit microcontrollers to 64-bit servers
  • Zero dependencies. Builds cleanly by ISO C or ISO C++ compilers
  • Easy to embed: just copy elk.c and elk.h to your source tree
  • Very small and simple embedding API
  • Can call native C/C++ functions from JavaScript and vice versa
  • Does not use malloc. Operates with a given memory buffer only
  • Small footprint: about 20KB on flash/disk, about 100 bytes RAM for core VM
  • No bytecode. Interprets JS code directly

Below is a demonstration on a classic Arduino Nano board which has 2K RAM and 30K flash (see full sketch):

Elk on Arduino Nano

JavaScript on ESP32

The Esp32JS Arduino sketch is an example of Elk integration with ESP32. Flash this sketch on your ESP32 board, go to http://elk-js.com, and get a JavaScript development environment instantly! Reloading your script takes a fraction of a second - compare that with a regular reflashing.. Here how it looks like:

The example JS firmware implements:

  • Blinks an LED periodically
  • Connects to the HiveMQ MQTT server
  • Subscribes to the elk/rx topic
  • When an MQTT message is received, sends some stats to the elk/tx topic:

That's screenshot is taken from the MQTT server which shows that we sent a hello JS! message and received stats in response:

Call JavaScript from C

#include <stdio.h>
#include "elk.h"

int main(void) {
  char mem[200];
  struct js *js = js_create(mem, sizeof(mem));  // Create JS instance
  jsval_t v = js_eval(js, "1 + 2 * 3", ~0);     // Execute JS code
  printf("result: %s\n", js_str(js, v));        // result: 7
  return 0;
}

Call C from JavaScript

This demonstrates how JS code can import and call existing C functions:

#include <stdio.h>
#include "elk.h"

// C function that adds two numbers. Will be called from JS
int sum(int a, int b) {
  return a + b;
}

int main(void) {
  char mem[200];
  struct js *js = js_create(mem, sizeof(mem));  // Create JS instance
  jsval_t v = js_import(js, sum, "iii");        // Import C function "sum"
  js_set(js, js_glob(js), "f", v);              // Under the name "f"
  jsval_t result = js_eval(js, "f(3, 4);", ~0); // Call "f"
  printf("result: %s\n", js_str(js, result));   // result: 7
  return 0;
}

Supported features

  • Operations: all standard JS operations except:
    • !=, ==. Use strict comparison !==, ===
    • No ternary operator a ? b : c
    • No computed member access a[b]
  • Typeof: typeof('a') === 'string'
  • While: while (...) { ... }
  • Conditional: if (...) ... else ...
  • Simple types: let a, b, c = 12.3, d = 'a', e = null, f = true, g = false;
  • Functions: let f = function(x, y) { return x + y; };
  • Objects: let obj = {f: function(x) { return x * 2}}; obj.f(3);
  • Every statement must end with a semicolon ;
  • Strings are binary data chunks, not Unicode strings: 'Київ'.length === 8

Not supported features

  • No var, no const. Use let (strict mode only)
  • No do, switch, for. Use while
  • No => functions. Use let f = function(...) {...};
  • No arrays, closures, prototypes, this, new, delete
  • No standard library: no Date, Regexp, Function, String, Number

Performance

Since Elk parses and interprets JS code on the fly, it is not meant to be used in a performance-critical scenarios. For example, below are the numbers for a simple loop code on a different architectures.

let a = 0;        // 97 milliseconds on a 16Mhz 8-bit Atmega328P (Arduino Uno and alike)
while (a < 100)   // 16 milliseconds on a 48Mhz SAMD21
  a++;            //  5 milliseconds on a 133Mhz Raspberry RP2040
                  //  2 milliseconds on a 240Mhz ESP32

Build options

Available preprocessor definitions:

NameDefaultDescription
JS_EXPR_MAX20Maximum tokens in expression. Expression evaluation function declares an on-stack array jsval_t stk[JS_EXPR_MAX];. Increase to allow very long expressions. Reduce to save C stack space.
JS_DUMPundefinedDefine to enable js_dump(struct js *) function which prints JS memory internals to stdout

Note: on ESP32 or ESP8266, compiled functions go into the .text ELF section and subsequently into the IRAM MCU memory. It is possible to save IRAM space by copying Elk code into the irom section before linking. First, compile the object file, then rename .text section, e.g. for ESP32:

$ xtensa-esp32-elf-gcc $CFLAGS elk.c -c elk.tmp
$ xtensa-esp32-elf-objcopy --rename-section .text=.irom0.text elk.tmp elk.o

API reference

js_create()

struct js *js_create(void *buf, size_t len);

Initialize JS engine in a given memory block. Elk will only use that memory block to hold its runtime, and never use any extra memory. Return: a non-NULL opaque pointer on success, or NULL when len is too small. The minimum len is about 100 bytes.

The given memory buffer is laid out in the following way:

  | <-------------------------------- len ------------------------------> |
  | struct js, ~100 bytes  |   runtime vars    |    free memory           | 

js_eval()

jsval_t js_eval(struct js *, const char *buf, size_t len);

Evaluate JS code in buf, len and return result of the evaluation. During the evaluation, Elk stores variables in the "runtime" memory section. When js_eval() returns, Elk does not keep any reference to the evaluated code: all strings, functions, etc, are copied to the runtime.

Important note: the returned result is valid only before the next call to js_eval(). The reason is that js_eval() triggers a garbage collection. A garbage collection is mark-and-sweep, run before every top-level statement gets executed.

The runtime footprint is as follows:

  • An empty object is 8 bytes
  • Each object property is 16 bytes
  • A string is 4 bytes + string length, aligned to 4 byte boundary
  • A C stack usage is ~200 bytes per nested expression evaluation

js_str()

const char *js_str(struct js *, jsval_t val);

Stringify JS value val and return a pointer to a 0-terminated result. The string is allocated in the "free" memory section. If there is no enough space there, an empty string is returned. The returned pointer is valid until the next js_eval() call.

js_import()

jsval_t js_import(struct js *js, uintptr_t funcaddr, const char *signature);

Import an existing C function with address funcaddr and signature signature. Return imported function, suitable for subsequent js_set().

  • js: JS instance
  • funcaddr: C function address: (uintptr_t) &my_function
  • signature: specifies C function signature that tells how JS engine should marshal JS arguments to the C function. First letter specifies return value type, following letters - parameters:
    • b: a C bool type
    • d: a C double type
    • i: a C integer type: char, short, int, long
    • s: a C string, a 0-terminated char *
    • j: a jsval_t
    • m: a current struct js *. In JS, pass null
    • p: any C pointer
    • v: valid only for the return value, means void

The imported C function must satisfy the following requirements:

  • A function must have maximum 6 parameters
  • C double parameters could be only 1st or 2nd. For example, function void foo(double x, double y, struct bar *) could be imported, but void foo(struct bar *, double x, double y) could not
  • C++ functions must be declared as extern "C"
  • Functions with float params cannot be imported. Write wrappers with double

Here are some example of the import specifications:

  • int sum(int) -> js_import(js, (uintptr_t) sum, "ii")
  • double sub(double a, double b) -> js_import(js, (uintptr_t) sub, "ddd")
  • int rand(void) -> js_import(js, (uintptr_t) rand, "i")
  • unsigned long strlen(char *s) -> js_import(js, (uintptr_t) strlen, "is")
  • char *js_str(struct js *, js_val_t) -> js_import(js, (uintptr_t) js_str, "smj")

In some cases, C APIs use callback functions. For example, a timer C API could specify a time interval, a C function to call, and a function parameter. It is possible to marshal JS function as a C callback - in other words, it is possible to pass JS functions as C callbacks.

A C callback function should take between 1 and 6 arguments. One of these arguments must be a void * pointer, that is passed to the C callback by the imported function. We call this void * parameter a "userdata" parameter.

The C callback specification is enclosed into the square brackets [...]. In addition to the signature letters above, a new letter u is available that specifies userdata parameter. In JS, pass null for u param. Here is a complete example:

#include <stdio.h>
#include "elk.h"

// C function that invokes a callback and returns the result of invocation
int f(int (*fn)(int a, int b, void *userdata), void *userdata) {
  return fn(1, 2, userdata);
}

int main(void) {
  char mem[500];
  struct js *js = js_create(mem, sizeof(mem));
  js_set(js, js_glob(js), "f", js_import(js, f, "i[iiiu]u"));
  jsval_t v = js_eval(js, "f(function(a,b,c){return a + b;}, 0);", ~0);
  printf("result: %s\n", js_str(js, v));  // result: 3
  return 0;
}

js_set(), js_glob(), js_mkobj()

jsval_t js_glob(struct js *);   // Return global object
jsval_t js_mkobj(struct js *);  // Create a new object
void js_set(struct js *, jsval_t obj, const char *key, jsval_t val);  // Assign property to an object

These are helper functions for assigning properties to objects. The anticipated use case is to give names to imported C functions.

Importing a C function sum into the global namespace:

  jsval_t global_namespace = js_glob(js);
  jsval_t imported_function = js_import(js, (uintptr_t) sum, "iii");
  js_set(js, global_namespace, "f", imported_function);

Use js_mkobj() to create a dedicated object to hold groups of functions and keep a global namespace tidy. For example, all GPIO related functions can go into the gpio object:

  jsval_t gpio = js_mkobj(js);              // Equivalent to:
  js_set(js, js_glob(js), "gpio", gpio);    // let gpio = {};

  js_set(js, gpio, "mode",  js_import(js, (uintptr_t) func1, "iii");  // Create gpio.mode(pin, mode)
  js_set(js, gpio, "read",  js_import(js, (uintptr_t) func2, "ii");   // Create gpio.read(pin)
  js_set(js, gpio, "write", js_import(js, (uintptr_t) func3, "iii");  // Create gpio.write(pin, value)

js_usage()

int js_usage(struct js *);

Return memory usage percentage - a number between 0 and 100.

Download Details:
Author: cesanta
Download Link: Download The Source Code
Official Website: https://github.com/cesanta/elk 
License: GPLv2

#javascript

 

Christa  Stehr

Christa Stehr

1594456938

Offshore Software Development - Best Practices

With the rise of globalization and the worldwide lockdown due to the pandemic, most of the work has been done by remote working processes and professionals from their homes. This lockdown has proved the efficiency of remote development and enhanced the trust in offshore software development industry.

To make the most out of the benefits of offshore software development, you should understand the crucial factors that affect offshore development. This is why you should read this guide for the best practices when hiring an offshore software development company. Despite the size and the industry of the business, offshore software development is not beneficial for every entrepreneur in many aspects to make the optimum use of talents in technology across the globe.

Here are some of the top reasons why offshore development is beneficial for your business.

  • Offshore development teams can work on flexible timing to provide you with the best possible software development practices.
  • Get access to the talents across the world from your home to develop the top of the line software with the help of offshore development companies.
  • Assured high quality and next-generation technology expertise with duly NDA signed with respect to the priorities of the business.
  • With flexible recruitment models, you can hire the freelance developers, remote development team, or an entire offshore development company with respect to the size of your business.
  • Build high-end software applications from one corner of the world by hiring software developers across the world.
  • Get immediate access to the best resources without hiring them on a permanent basis.

To avail of all these benefits, you should have clear goals, a list of requirements, and features that are mandatory for your software product.

Here are a few tips to help you find the best offshore software development company. Build a top-notch software application by following the listed best practices.

#web development #how to start offshore software development company #offshore meaning #offshore software development best practices #offshore software development company #offshore software development company in india #offshore software development cost #offshore software development statistics #outsource software development

aviana farren

aviana farren

1623067115

IDO Development | Initial DEX Offering Development | IDO Development Platform

Initial DEX offering, commonly abbreviated as IDO, is a digital fundraising opportunity for the investors and business developers in a decentralized platform. IDO is the representation of the digital assets, with zero exchange fees being paid. Distributing tokens and fundraising are at ease through the IDO platform. IDO is considered as the combination of both ICO & IEO.

The benefits of IDO are as follows:

  • Fair & open fundraising opportunity
  • Immediate trading
  • Immediate liquidity
  • Safe & faster transaction
  • Affordable price
  • Low exchange fee

The steps involved in the Initial DEX offering development are as follows:

  • Roadmap creation: This step includes analyzing & characterizing the model, for making the model user-friendly and targeting the audience’s needs. It should also be beginner-friendly to make the beginner comfortable with the model…
  • White paper creation: The creation of the White paper should be carefully done as this is the important step. The creation means the features and the functionalities of the product. The features must satisfy the user demands at a convenient price.
  • Token development: The developers will specially design the tokens according to the customer request. The smart contact enabled, and blockchain like Ethereum makes the transaction more secure.
  • Listing tokens & marketing: It is necessary to choose the right decentralized exchange to list the tokens so as to reach the right audience. The marketing technique enables the selling of tokens to the next level.

Infinite Block Tech offers the Initial DEX offering development with a team of highly specialized blockchain engineers, and marketing specialists to deliver the best for the users. The cost of IDO development depends upon the features and functions demanded by the users. Thus, the cost may increase or decrease from one IDO development project to another. So, it’s the right time to step into our IDO development marketplace to raise the funds effectively.

#initial dex offering development #ido development #ido development platform #cost of ido development #ido development project #ido development marketplace