Category Archives: C++

Functional pipeline in C++11

I stumbled upon this nice blog post – pipable functions in C++14. This is realy fun idea as its usage plain for anybody who is familiar with unix pipelines. So i tried to use it in C++11 (without boost) from slightly different angle to make it more real-life concept.

First sample (fun, but not so interesting):

C++

auto add = piped([](int x, int y){ return x + y; });
auto mul = piped([](int x, int y){ return x * y; });
int y = 5 | add(2) | mul(5) | add(1); // Output: 36

auto add = piped([](int x, int y){ return x + y; });

auto mul = piped([](int x, int y){ return x * y; });

int y = 5 | add(2) | mul(5) | add(1); // Output: 36

Second sample (functional style array processing):

C++

vector<int> numbers{4,8,15,16,23,42};
auto result = numbers | where([](int x){ return (x > 10); }) | map([](int x){ return x + 5; }) | log();
// List: 20 21 28 47

vector<int> numbers{4,8,15,16,23,42};

auto result = numbers | where([](int x){ return (x > 10); }) | map([](int x){ return x + 5; }) | log();

// List: 20 21 28 47

Simple and short implementation is under the cut…

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10 ways to not shoot yourself in the foot using C++11

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Within C++, there is a much smaller and cleaner language struggling to get out (Stroustrup)

The following text could be modified – current rev.1.0

Very often i hear from java/erlang/etc people that C++ is so bad that it is very unwise to use so-old-school language now, when we have more ‘safe’ higher level languages. Everybody heard about foot-shooting using C++. What about C++11?

Bjarne said that C++11 feels like whole new language and, at first, i did not take it seriously as modifications looked more as minor additions (especially for boost users). Now i changed my mind – using new features combined together can transform your way of coding into new form. I’m talking not about adding new features to your code, but about changing your coding style.

How not to shoot yourself in the foot? Here is the list of my rules to make the C++ coding life sweet and easy. This is simple convention to follow and can be adopted very fast. Not only it gives more stable implementation but also more clean and understandable design.

This convention is composition of Scott Meyers rules, Functional programming ideas and reducing-complexity ideology by Steve McConnell.

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Writing custom protocol for nanomsg

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Nanomsg is next version of ZeroMQ lib, providing smart cross-platform sockets for implementation of distributed architectures. Here you can find basic examples of included protocols (communication patterns). Lib is simple (written in pure C) and does not have any dependencies like boost. And as this is at least 3rd iteration from same author you can expect some quality/performance here.

This is kind of solution for the hell of writing of your own serious socket server. If you already had such experience you should understand the range of problems which are not so obvious at start. But here we expect to skip all such problems and go straight to processing messages. Lib handles automatic reconnection in case of link disconnects, nonblocking receiving/sending, sockets which can handle large set of clients, etc. All this seems like perfect solution for server-side inner transport of fast distributed architectures.

But i also want to try it outside. The basic communication patterns (PAIR, BUS, REQREP, PUBSUB, PIPELINE, SURVEY) may fit large set of inner server transport schemes, but there are some minor limits in current implementation for client side application. I mean limits of protocols, not the lib itself.

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Easing functions for your animations

Dockerfile example how to compile libcurl for Android inside Docker container

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Update: 5 july 2015 – See updated version of dockerfile at the end of post with new NDK / SSL / clang toolchain.

If you never heard of Docker be sure to check it out as fast as possible. There are lot of publications out there. At first it looks like another virtualisation software but it is actually more like new paradigm. Someone may call it very advanced chroot, someone may call virtual containers with version control and building scripts, and so on. I like it as the idea of application-centric containers – your application can keep whole operating system as a coating and its making perfect separation from outside influence. As well you can easily reproduce production process environment at another location. It makes virtualisation easy and fun.

Almost everything can be done inside containers now. Recently i had to recompile curl for Android as static lib using latest NDK toolchain. Its not so complicated to do on your local machine (if it is not Windows) but now there is a more clean way to do this time-wasting operation. You can go to digital ocean, create droplet with Docker and using Dockerfile from the end of this post compile it while drinking coffee.

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TripBudget – stylish budget calculator/logger for trips – BETA Android release

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My new tool at android play market – you can find it here. This is stylish planner/tracker for your trip’s budgets – planning and logging as one fast and fancy instrument.

More information and screens can be found below…

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How to create parallax effect using accelerometer

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This is short guide how to create parallax effect using accelerometer on mobile platforms. Some code is related to Android, but all concept is applicable to iOS, etc.

What is parallax effect? There are some more complex definitions but i would define as simple as the following – you move your phone/device in space and some objects inside your application are shifting accordingly to compensate this movement. This allows to create some strong feeling of 3d interface as well as nice interaction effect.

As good example you can check out my live wallpaper (link on market), which is using this effect while rendering particle system of moving objects. More information about this application can be found here.

To create parallax effect we need to grab data from accelerometer sensor (as i found out gyroscope is not present at majority of phones while accelerometer gives enough of data to be happy with it), convert sensor data to relative rotation angles and shift some parts of application interface accordingly. 3 steps:

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Stackblur – C++ multi-threaded version of fast blur algorithm

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I found nice algorithm for blurring images – Stackblur by Mario Klingemann. It could do the job relatively fast and gives decent quality. You can check it here – web demonstration. As you can see it can be usable even in web projects.

As i wanted to include it to my cross-platform engine i found two c++ implementations:

First is SSE friendly, second contains some division optimization via static tables. However, both are not using all cpu cores. I took second one as foundation for my implementation, as i expected my code to work on mobile devices with no SSE support. Single-core processing of 1920×1200 rgba image with 100 px radius took only 219 ms (Intel Q9550, Windows 7).

I improved stackblur code to multi-threaded version – on my quad-core cpu speed results as expected showed 4x improvement – 63ms for the same task. You can download the part my lib below and use it as a foundation to your needs.

Download multi-threaded 32bit-color (RGBA) version of StackBlur: stackblur.cpp

I believe algorithm can be optimized even further – any suggestions are welcome.

Compact lib for JSON parsing (cross-platform C++)

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Recently i was in search of compact C++ source code for parsing of JSON format. This is very simple minimalistic format and its very popular – but i was surprised when found a lot of complex parsers and no simple implementation inside one cpp-h pair. So i wrote one.

Here it is – tiny C++ cross-platform solution for JSON decoding without any dependencies like boost or something: MVJSON.cpp MVJSON.h (version 1.0)

UPD: recent version could be found here: GIST

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Alive Numbers 2 – android release of my minimalistic live wallpaper with embedded widgets

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Brand new version of live wallpaper – Alive Numbers 2 for Android devices. Enjoy smooth OpenGl ES 2.0 animation of minimalistic animated background in couple with customisable embedded widgets. New version has adjustable color schemes and ability to hand-tune widget layout. You can choose from set of base animations and play with a lot of options for every widget.