Binary array command of redis

1. redis Binary array command
   1. getbit command
   2. setbit command
   3. bitcount command
   4. summary
   5. ️ Thank you for your

redis Binary array command

redis The binary array of is in SDS To represent the ,sds Of len The value of the property represents SDS How many byte long bit groups are saved ,buf Each byte of the array is represented by a row , Each row 8 And the array is stored in reverse order

getbit command

getbit The command obviously returns the value of the binary bits of the specified offset of the bit array ,

redis> GETBIT bit 10086(integer) 1

The execution process is to divide the offset by 8 The binary bits specified by the calculated offset are stored in the byte of the bit array , Then offset mod8 Add another one to calculate the number of bits in the binary system , Get the value of this bit and return

setbit command

setbit The command is to set a new value for the specified offset , And return the old value . If the offset is greater than the current one, it will be expanded

redis> SETBIT bit 10086 1(integer) 0

bitcount command

bitcount The command is used to count the values in an array 1 The number of

redis> BITCOUNT bits(integer) 0redis> SETBIT bits 0 1          # 0001(integer) 0redis> BITCOUNT bits(integer) 1redis> SETBIT bits 3 1          # 1001(integer) 0redis> BITCOUNT bits(integer) 2

bitcount Implementation of commands redis Table lookup method and Hamming algorithm are used , The number of binary bits is greater than or equal to 128 Bit uses Hamming Algorithm , Less than 128 Bit use look-up table .

bitop and Is to carry out and operate

bitop or To do or operate

bitop xor Is an XOR operation

bitop not Yes no operation

summary

This article mainly introduces redis Binary array of ,redis The binary array of SDS To express ,getbit Command returns the value of the binary bit of the specified offset of the bit array ,setbit The command sets a new value for the specified offset , And return the old value ,bitcount The command counts the values in the array as 1 The number of , When the number of binary bits is greater than or equal to 128 Bit using Hamming algorithm , Less than 128 Bit using the look-up table method ,bitop Command performs bit operations on binary arrays , It has various parameters ,and Representation and operation ,or To express or operate ,xor The XOR operation indicates ,not Indicates non operation , These commands are all commands that operate on binary arrays , Mastering binary array commands can make us more familiar with redis Binary array of .

️ Thank you for your

If you think this is helpful for you ：

1. Welcome to follow me ️, give the thumbs-up , Comment on , forward
2. Focus on Panpan small class , Push good articles for you regularly , There are also group chat and irregular lottery activities , You can say what you want , Communicate with the great gods , Learning together .
3. If there is anything inappropriate, you are welcome to criticize and correct .