When browsing the source code of Guava, I came across the following piece of code (part of the implementation of hashCode for the inner class CartesianSet): int adjust = size() – 1; for (int i = 0; i < axes.size(); i++) { adjust *= 31; adjust = ~~adjust; // in GWT, we have to deal … Read more
I need to convert an int to a byte[] one way of doing it is to use BitConverter.GetBytes(). But im unsure if that matches the following specification: An XDR signed integer is a 32-bit datum that encodes an integer in the range [-2147483648,2147483647]. The integer is represented in two’s complement notation. The most and least … Read more
For the life of me, I can’t remember how to set, delete, toggle or test a bit in a bitfield. Either I’m unsure or I mix them up because I rarely need these. So a “bit-cheat-sheet” would be nice to have. For example: flags = flags | FlagsEnum.Bit4; // Set bit 4. or if ((flags … Read more
var attr = ~’input,textarea’.indexOf( target.tagName.toLowerCase() ) ? ‘value’ : ‘innerHTML’ I saw it in an answer, and I’ve never seen it before. What does it mean? 5 Answers 5
A colleague of mine stumbled upon a method to floor float numbers using a bitwise or: var a = 13.6 | 0; //a == 13 We were talking about it and wondering a few things. How does it work? Our theory was that using such an operator casts the number to an integer, thus removing … Read more
I want to write a function that returns the nearest next power of 2 number. For example if my input is 789, the output should be 1024. Is there any way of achieving this without using any loops but just using some bitwise operators? 31 Answers 31 Check the Bit Twiddling Hacks. You need to … Read more
I am fairly new to C programming, and I encountered bit masking. Can someone explain to me the general concept and function of bit masking? Examples are much appreciated. 2 Answers 2
What is the most efficient algorithm to achieve the following: 0010 0000 => 0000 0100 The conversion is from MSB->LSB to LSB->MSB. All bits must be reversed; that is, this is not endianness-swapping. 26 Answers 26
I saw an interesting technique used in an answer to another question, and would like to understand it a little better. We’re given an unsigned 64-bit integer, and we are interested in the following bits: 1…….2…….3…….4…….5…….6…….7…….8……. Specifically, we’d like to move them to the top eight positions, like so: 12345678……………………………………………….. We don’t care about the … Read more
I’m in a computer systems course and have been struggling, in part, with Two’s Complement. I want to understand it but everything I’ve read hasn’t brought the picture together for me. I’ve read the wikipedia article and various other articles, including my text book. Hence, I wanted to start this community wiki post to define … Read more
