Chapter  3

Advanced NDK

Chapter 2 showed you how to set up a project using the Android NDK and how you could use C or C++ code in your Android application. In many cases, this is as far as you will need to go. However, there may be times when digging a little deeper is required to find what can be optimized even more.

In this chapter, you will get your hands dirty and learn how you can use a low-level language to take advantage of all the bells and whistles the CPU has to offer, which may not be possible to use from plain C or C++ code. The first part of the chapter shows you several examples of how you can optimize functions using the assembly language and gives you an overview of the ARM instruction set. The second part covers some of the C extensions the GCC compiler supports that you can take advantage of to improve your application’s performance. Finally, the chapter concludes with a few very simple tips for optimizing code relatively quickly.

While the latest Android NDK supports the armeabi, armeabi-v7a, and x86 ABIs, this chapter will focus on the first two as Android is mostly deployed on ARM-based devices. If you plan on writing assembly code, then ARM should be your first target. While the first Google TV devices were Intel-based, Google TV does not yet support the NDK.