bitmask

How to use bitmask? [closed]

由 泄露秘密 提交于 2019-11-26 22:30:26
问题 How do i use it in C++ ? when is it useful to use ? Please give me an example of a problem where bitmask is used , how it actually works . Thanks! 回答1: Bit masking is "useful" to use when you want to store (and subsequently extract) different data within a single data value. An example application I've used before is imagine you were storing colour RGB values in a 16 bit value. So something that looks like this: RRRR RGGG GGGB BBBB You could then use bit masking to retrieve the colour

Mask and aggregate bits

由 无人久伴 提交于 2019-11-26 21:24:02
问题 I'm trying to efficiently execute the following task: INPUT VALUE: 01101011 MASK: 00110010 MASK RESULT: --10--1- AGGREGATED: 00000101 I hope this examples explains clearly what I'm trying to achieve. What's the best way to do this in a non-naive way? 回答1: This operation is called compress_right or just compress , and it is moderately terrible to implement without hardware support. The non-naive code from Hacker's Delight "7–4 Compress, or Generalized Extract" to implement this function is

When is it better to store flags as a bitmask rather than using an associative table?

由 梦想与她 提交于 2019-11-26 19:07:07
问题 I’m working on an application where users have different permissions to use different features (e.g. Read, Create, Download, Print, Approve, etc.). The list of permissions isn’t expected to change often. I have a couple of options of how to store these permissions in the database. In what cases would Option 2 be better? Option 1 Use an associative table. User ---- UserId (PK) Name Department Permission ---- PermissionId (PK) Name User_Permission ---- UserId (FK) PermissionId (FK) Option 2

Comparing two bitmasks in SQL to see if any of the bits match

由 為{幸葍}努か 提交于 2019-11-26 19:01:56
问题 Is there a way of comparing two bitmasks in Transact-SQL to see if any of the bits match? I've got a User table with a bitmask for all the roles the user belongs to, and I'd like to select all the users that have any of the roles in the supplied bitmask. So using the data below, a roles bitmask of 6 (designer+programmer) should select Dave, Charlie and Susan, but not Nick. User Table ---------- ID Username Roles 1 Dave 6 2 Charlie 2 3 Susan 4 4 Nick 1 Roles Table ----------- ID Role 1 Admin 2

How to implement a bitmask in php?

由 谁说胖子不能爱 提交于 2019-11-26 18:50:28
问题 I'm not sure if bitmask is the correct term. Let me explain: In php, the error_reporting function can be called multiple ways: // Report simple running errors error_reporting(E_ERROR | E_WARNING | E_PARSE); // Reporting E_NOTICE can be good too (to report uninitialized // variables or catch variable name misspellings ...) error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE); // Report all errors except E_NOTICE // This is the default value set in php.ini error_reporting(E_ALL ^ E_NOTICE)

What to do when bit mask (flags) enum gets too large

由 自闭症网瘾萝莉.ら 提交于 2019-11-26 18:50:24
问题 I have a very large set of permissions in my application that I represent with a Flags enumeration. It is quickly approaching the practical upper bound of the long data type. And I am forced to come up with a strategy to transition to a different structure soon. Now, I could break this list down into smaller pieces, however, this is already just a subset of the overall permissions for our application, based on our applications layout. We use this distinction extensively for display purposes

Using Layers and Bitmask with Raycast in Unity

由 烂漫一生 提交于 2019-11-26 16:42:38
Unity's Raycast functions has a parameter you could use to raycast to a particular GameObject. You can also use that parameter to ignore particular GameObject. For exmple the Raycast function: public static bool Raycast(Vector3 origin, Vector3 direction, float maxDistance = Mathf.Infinity, int layerMask = DefaultRaycastLayers, QueryTriggerInteraction queryTriggerInteraction = QueryTriggerInteraction.UseGlobal); The layerMask parameter is used to specified which Objects should/should not receive the raycast. 1 .How do you raycast to a particular GameObject which is in a layer called "cube"? 2

Using a bitmask in C#

由 自闭症网瘾萝莉.ら 提交于 2019-11-26 15:46:43
Let's say I have the following int susan = 2; //0010 int bob = 4; //0100 int karen = 8; //1000 and I pass 10 (8 + 2) as a parameter to a method and I want to decode this to mean susan and karen I know that 10 is 1010 but how can I do some logic to see if a specific bit is checked as in if (condition_for_karen) // How to quickly check whether effective karen bit is 1 Right now all i can think of is to check whether the number i passed is 14 // 1110 12 // 1100 10 // 1010 8 // 1000 When I have a larger number of actual bits in my real world scenario, this seems impractical, what is a better way

Why should I use bitwise/bitmask in PHP?

由 三世轮回 提交于 2019-11-26 11:58:44
问题 I am working on a user-role / permission system in PHP for a script. Below is a code using a bitmask method for permissions that I found on phpbuilder.com. Below that part is a much simpler version w3hich could do basicly the same thing without the bit part. Many people have recommended using bit operators and such for settings and other things in PHP, I have never understood why though. In the code below is there ANY benefit from using the first code instead of the second? <?php /** *

Using Layers and Bitmask with Raycast in Unity

由 最后都变了- 提交于 2019-11-26 06:02:55
问题 Unity\'s Raycast functions has a parameter you could use to raycast to a particular GameObject. You can also use that parameter to ignore particular GameObject. For exmple the Raycast function: public static bool Raycast(Vector3 origin, Vector3 direction, float maxDistance = Mathf.Infinity, int layerMask = DefaultRaycastLayers, QueryTriggerInteraction queryTriggerInteraction = QueryTriggerInteraction.UseGlobal); The layerMask parameter is used to specified which Objects should/should not
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