What is the maximum length that can be set for the bitmap of redis? Why is the maximum length bit that can be set 2 ^ 32? How to calculate how much space the bitmap will occupy

Premise :  actually , redis Only support 5 Type of data . did not bitmap. That is to say bitmap Is based on redis Of string type . A string type can store up to 512M.

First : First understand the unit conversion of computer

         8 bit = 1byte  

         1024 byte = 1kb

         1024 kb = 1Mb

secondly :

      What we use bitmap Instructions SETBIT  key  offset value, This instruction is to put the offset Set to 0 or 1.  such as  SETBIT  ss  1000 1 // Will be 1000 The position is 1.  1 bit Namely 1 position ,  So we just need to 512M The conversion bit, Then I know bitmap The maximum set length supported .  The calculation is as follows

      8 * 1024 * 1024 * 512  =  2^32    ( So that's the result ) 

How to calculate your own bitmap How much storage space will it take ?  

Take a chestnut : There is one today bitmap Maximum length 1024, How much space does it take ?

Explain : length 1024 That is, he needs 1024 bits (bit),  Or the unit is byte Just need 1024 / 8, That is to say 128byte