bitmasks are data used for bitwise operations.
Questions tagged [bit-masks]
54 questions
2
votes
3 answers
How to ignore bits in a variable
I would like to know how to delete bits in a bit value.
I receive a 10 bits value (bit 0 to bit 9) and I have to send a variable which ignore bit 0, bit 2, bit 4 and bit 6 of the received value then my variable will be : bit 987531. How can I do ? I…
user8451061
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- 3
2
votes
2 answers
Physics contacts in SpriteKit
Is it possible to explain how bitmasking works for just this simplistic situation:
A big (blue) ball. Contact BitMask 0b0001
A medium (red) ball. Contact BitMask 0b0010
A small (white) ball. Contact BitMask 0b0100
They have no collisions…
Confused
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2
votes
1 answer
sprite kit swift, detecting collision for game over
I am currently making my first game. I have a collision function ballCollideWithWall(_:Ball:) which is called as expected, but the game over scene is not presenting. I verified that the collision function is called by using NSLog.
// game over…
joey2308
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- 1
2
votes
1 answer
64bit bitmask and javascript
I am currently fighting with a javascript problem where I have a 62bit bitmask that should be used as filter.
I used the snippet from here but I cant get it to work for some cases.
How to do bitwise AND in javascript on variables that are longer…
Max Melcher
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2
votes
1 answer
Bitmasking small numeric values over a byte array without wasting space in c#?
I'm trying to extend this topic a bit by expanding it to cover 5-bit values packed into a byte[] data structure.
The specific objective I'm trying to achieve would be to store a total of 128 5-bit (0-31) numeric values in a 80-byte array with a…
CoryG
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2
votes
1 answer
Is is possible to set an NS_OPTION as a value in an NSMutableDictionary?
I'm trying to set up a dictionary of rules; the keys are strings, and I'd love to set up the values to be bitmaps.
I'm using NS_OPTION to declare items as such :
typedef NS_OPTIONS(NSInteger, PermittedDirection) {
LeftDirection = 1 << 0,
…
pikovayadama
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2
votes
1 answer
what is diffrence bettween masking a char with 0xFF and casting (unsigned char)
unsigned char Mid;
if( (data[2]) == 0x9A){
Mid = data[5];
if( (Mid == 1) || (Mid == 2) || (Mid == 3) )
return(Mid);
The code above gives:
warning: comparison is always false due to limited range of data type
error as I…
roll
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1
vote
1 answer
32-bit int struct bits don't seem to match up (nodejs)
I have a file that defines a set of tiles (used in an online game). The format for each tile is as follows:
x: 12 bits
y: 12 bits
tile: 8 bits
32 bits in total, so each tile can be expressed as a 32 bit integer.
More info about the file…
samstr
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1
vote
1 answer
How to translate from decimal to bit-mask?
I have a ACLs system previously built by someone else and I am trying to understand how bit-masking works there. I have this 4 constants defined:
const NONE = 0;
const READ = 1;
const WRITE = 2;
const UPDATE = 4;
const DELETE = 8;
Then in DB I am…
ReynierPM
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1
vote
1 answer
What is the optimal way to choose a set of features for excluding items based on a bitmask when matching against a large set?
Suppose I have a large, static set of objects, and I have an object that I want to match against all of them according to a complicated set of criteria that entails an expensive test.
Suppose also that it's possible to identify a large set of…
samgak
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1
vote
1 answer
Multiple collision bitmasks on 1 physics object?
Can one physics body have 2 different collision bit masks?
I have this code:
bo.physicsBody?.collisionBitMask = noneCategory
But I'd like "bo" to also collide with "bumperCategory". So, I imagine it could look something like this:
…
Alan Scarpa
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1
vote
1 answer
Bitmask Permissions - Extending/Revoking permissions
I have a bitmask permissions + roles set:
{
EDIT: '1',
DELETE: '2',
ADD: '4',
VIEW: '8',
}
I'm looking for the simplest way to Extend and Revoke user permissions using bitwise operations.
For example a user has 7 set as permissions…
Maruf
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1
vote
1 answer
Rails: A database-independent datatype that's suitable for bitwise operations
I have a Rails app with a couple resources that I need to run queries on that involve bitwise operations. Right now, I'm using PostgreSQL, and I created a migration for my 'user' model that uses the postgres-specific 'BIT VARYING' datatype, since…
Andrew
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1
vote
1 answer
Convert long string to integer without parseLong or parseInt
Here's is the situation ... i have a binary file which contains 32-bit binary strings of characters (e.g 1011011100100110101010101011010 ) and i want to convert this to integer ... I have already tried to do it with parse-Int but if the most…
Marios Filipidis
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vote
0 answers
Bitmask comparisons Mongo queries
For a Blog webapp, I am trying to model a set of users, blogs and actions on resources in mongo. Users can perform a no of actions such as 'like', 'star', 'feature' resources of a blog post such as 'blog posts' ,'links', 'images', etc.
The model…
Skynet
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