Questions tagged [bitwise]

Bitwise refers to a bitwise operation which operates on one or more bit patterns or binary numerals at the level of their individual bits.

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78 views

Bit Vector implementation

Looking for a general review. ...
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1answer
396 views

Count bits in VBScript

I'm trying to write a function that returns the number of bits set in a 32-bit integer in VBScript, it's just for practising the language. The function I've written so far looks okay, but I'm ...
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Calculating CRC using arbitrary polynomials

This is my implementation of calculating CRCs which supports arbitrary polynomials specified in different representations (according to the explanations given here and here). My concerns are: I don'...
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1answer
311 views

Decoding 32-bit MIPS instructions

For a homework assignment I've been given the task of parsing out information from an 32-bit MIPS instruction. (For more information on the instruction formats, see here). The instructor has provided ...
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2answers
590 views

Compute the XOR of all the elements in the upper left triangular of a square matrix

Given a dimension \$D\$. We generate a \$D\times D\$ matrix with elements that start from \$0\$. For example, if we're given a dimension \$4\$ this is what our matrix looks like: $$ \begin{bmatrix}...
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1answer
472 views

Hackerrank Sum vs XoR

I'm in the process of improving my coding style and performance hence I decided to delve into bit manipulation on Hackerrank. I thought the question was straight forward but on large input, my ...
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1answer
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Using bitwise operators with (unsigned long) instead of bitfields

Here is my solution to Programming Exercise 15-7 from Stephen Prata's C Primer Plus, 6th Edition. This problem asks the reader to: 15-7 Write a program with the same behavior as described in ...
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3answers
572 views

Counting the number of “on” bits in an int

Here is some code I wrote as a solution to Programming Exercise 15.3 in Stephen Prata's C Primer Plus, 6th Edition. It is probably worth pointing out that the title of the chapter is Bit Fiddling. The ...
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1answer
374 views

K&R 2.6 Exercise setbits(x,p,n,y) function

Write a function setbits(x,p,n,y) that returns x with the n bits that begin at position <...
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1answer
470 views

Xoring in constant time in Java

I was inspired by this answer and the explanation and decided to support negative numbers. While testing, I noticed that the solution didn't handle the case with one number in the given range. A quick ...
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5answers
483 views

Print the next smallest and next largest number that have the same number of 1 bits in their binary representation

Given an integer , print the next smallest and next largest number that have the same number of 1 bits in their binary representation. How can I improve this? ...
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Maximize result of bitwise AND

This was the problem from "30 Days of Code" on Hackerrank: Given set \$S = \lbrace{1,2,3,\dots,N}\rbrace\$, find two integers \$A\$ and \$B\$ (where \$A \lt B\$), from set \$S\$ such that the ...
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Getting TLE for SPOJ Bitplay challenge program

I have tried a naive way to solve this problem: Given a even number N (N ≤ 109) and an integer K, you have to find the greatest odd number M less than N such that the sum of digits in binary ...
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Binary permissions system with bitwise operators + properties

I've written a simple permissions system that I need to be rather fast, yet useable by other developers who primarily use Java. Is a bitwise permissions system with properties a good compromise. Any ...
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Return the next power of two

Given an unsigned integer \$N\$, I want to return \$P\$ with \$P\$ being a power of two such that \$P \ge N\$. Examples: 1 -> 1 2 -> 2 3 -> 4 5 -> 8 The goal is to provide a very fast ...
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3answers
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Addition of two IEEE754-32bit single precision floating point numbers in C++

I made a C++ program which takes a list of triplets with S.No. from a text file, where the triplet, i.e. a,b,c correspond to a+b=c (addition done using float data type). Now I convert a and b from hex ...
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1answer
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Start an EventHandler in different Thread

I just stumbeled accross some code and I would do it in a different way. Since I am quite new to programming, I just wanted to know if I understand it right. Original Code: ...
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1answer
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ANDing ints in Java [closed]

Is there any better way than doing: if ((newState & InputState.DEFAULT) == InputState.DEFAULT) ? My InputState.class defines static int variables to the ...
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4answers
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Codility binary gap solution using regex

Below is the code I implemented to solve the binary gap problem: Find longest sequence of zeros, bounded by ones, in binary representation of an integer. However, it seems to be different from ...
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2answers
337 views

K&R 2-7 - Invert a bitfield from a number

This is my solution to the Exercise 2-7 of K&R C book. The assignment is: Write a function invert(x,p,n) that returns x ...
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1answer
292 views

Implementing checksum add without carry in C

I need to write a function in C which performs a checksum using the rule "add without carry". As I understand it, the "add without carry" concept is equivalent to the bitxor operator and given that ...
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1answer
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Bit shifting and masking

I was wondering if someone could review this simple bit of code that originally was in C++, but now converted to C# as practice in using bit-shifting and creating a sort of a quasi-array functionality....
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4answers
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A simple assembly program to count the number of ones in a register

I made a simple assembly program to count the number of ones in a register. Since this is basically my first ever, I would like to hear what I can improve or if there are some major flaws in this one: ...
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2answers
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Packing and unpacking bits (2)

Part 1 here. I improved my code from my previous question (linked above). ...
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Packing and unpacking bits

Part 2 here. I wrote this class for packing data. Would it benefit from being named BitPacker rather than BitStream (and change write/read to pack/unpack), or it works as is? How can I improve it? ...
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Using JavaScript-bitwise AND and -bitwise NOT for setting a number to 0

Obviously is the XOR-operator is used in low-level programming-languages used a lot for setting a value back to all bits 0. For example: 11010 ^ 11010 => 00000 Brought my teacher to figuring a out ...
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5answers
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Test four int of commonality in the lower four bits

The four parameters a, b, c and d can be ...
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1answer
482 views

Bit string builder for Java

I have this Java class for building bit strings. The set of methods it provides resembles that of java.lang.StringBuilder. See what I have: BitStringBuilder.java: ...
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1answer
143 views

LEB128 in Haskell

I have implemented the LEB128 encoding for unsigned integers. I'm fairly new to Haskell so I have some doubt about the coding style I'm using, particularly the definition of ...
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Convert tri-gram of type wchar_t to an integer type

I am trying to convert a tri-gram containing 3 characters of type wchar_t to an integer type (an uint64_t at the present time). ...
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3answers
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Calculating the 'binary gap' of a number

Inspired by this question and therefore this one I decided that clearly the best most readable way to solve this is with Regular Expressions. A binary gap within a positive integer N is any maximal ...
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Implement “at” lens for Data.Map

I've been working on adding an operation like Data.Lens.At.at to Data.Map. This uses an extremely fast, extremely small, and ...
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3answers
627 views

Byte array to floating point such as FPE2 in Java

Apple's System Management Controller uses FPE2 and SP78 as floating-point formats. While writing a Java library that that interfaces with the SMC, I ported someone's C function to convert read a FPE2-...
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3answers
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Finding the fastest common prefix of 2 strings in Python

I'm comparing my algorithms, slice_prefix and bit_prefix, with existing ones to find the common prefix length of 2 strings as ...
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1answer
116 views

A bitwise common prefix algorithm in Python

Is my algorithm slow because it has problems? Or, is any bitwise common prefix solution not going to give me the performance I'm looking for? After profiling my algorithm, I found that over 60% of ...
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1answer
263 views

Console app to teach bitwise operators

I'm creating a console app that has the purpose to teach you how to use C# bitwise operators. I have several classes which contain info about the different operators and I instantiate/add them in the ...
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1answer
351 views

Parsing an IP address (Bit manipulation)

Given a string representing of an IP address, such as "127.43.23.59", return a 32 bit integer representation of this string. The 32 bit integer is separated into four bytes, where each byte is one of ...
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1answer
314 views

Calculating the results of bit operations

I have a simple program that calculates and outputs the results of all the bit operators. I'm planning to send it to my friend and to explain some stuff about them to him. Before I do that, I want to ...
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2answers
7k views

Printing longest sequence of zeroes

I am doing a coding exercise in codility and I came across this question: A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ...
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2answers
690 views

Concatenate three 16-bit integers in one 64-bit integer with C++

I am looking for an elegant alternative of the following code where wordXX contains always 16 bits: ...
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2answers
921 views

Portable byte order conversion

I'm trying to improve the portability of a file format converter, specifically to POSIX platforms other than Linux. I'd appreciate a review of the following functions used for converting between ...
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0answers
114 views

Parallel popcount of packed bytes

I want to do a popcount of bytes in an array. Not a total popcount of everything, but lots of little popcounts for every individual byte to determine the neighborhood count in GoL. The following ...
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2answers
751 views

BMP writer in C

I recently wrote a BMP writer in C: bmpWriter.h ...
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3answers
459 views

Bit manipulation tool set

I made a tool set to facilitate bit manipulation as follows. Any comments are welcome, be it about the interface design, the implementation, or even the naming. Also, I want to make sure that the tool ...
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1answer
170 views

Speeding up the generation all bit strings with Hamming distance one

I'm playing around with hypercubes. For this, I need to create its edge set. Specifically, the edge set is the set of all bit strings with Hamming distance 1. An important property is that I want to ...
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1answer
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Saturated signed addition

So this a exercise from the book COMPUTERS SYSTEMS A PROGRAMMERS PERSPECTIVE I need to add two signed numbers and in case it overflows or underflows return ...
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2answers
200 views

Simulation of image transfer over noisy channel

Following this question, I've tried to rewrite some core methods to avoid using String for bit operations, and I ended up using ...
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1answer
216 views

Solution to part 1 of Day 7 Advent of Code in Scala

Does someone want to review my solution to part 1 of Day 7 Advent of Code in Scala? The assignment is here: http://adventofcode.com/day/7 Without repeating the whole text, in short: Given a text file ...
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1answer
127 views

Routine for convert decimal digits to Densely Packed Decimal

I've written an amd64 assembly routine (in gas syntax using the System V calling convention) to convert three decimal digits to Densely packed decimal because I wasn't satisfied by the performance of ...
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5answers
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Toggle four relays on/off based on bitmap stored in uint8_t

I am using a one-byte bitmap to control four relays. I am writing a function which will take the bitmap stored as uint8_t, look to see which bits are set/cleared, ...