BITOP

The BITOP command in DiceDB is used to perform bitwise operations between strings. This command supports several bitwise operations such as AND, OR, XOR, and NOT. The result of the operation is stored in a destination key.

Syntax

BITOP operation destkey key [key ...]

Parameters

Parameter	Description	Type	Required
AND	Perform a bitwise AND operation.	Operation	Yes
OR	Perform a bitwise OR operation.	Operation	Yes
XOR	Perform a bitwise XOR operation.	Operation	Yes
NOT	Perform a bitwise NOT operation (only one key is allowed for this operation).	Operation	Yes
destkey	The key where the result of the bitwise operation will be stored.	String	Yes
key [key ...]	One or more keys containing the strings to be used in the bitwise operation. For the NOT operation, only one key is allowed.	String	Yes

Return Value

Condition	Return Value
Integer	The command returns an integer value representing the length of the resulting string.
Error	An error is returned if the command fails.

Behaviour

When the BITOP command is executed, it performs the specified bitwise operation on the provided keys and stores the result in the destination key. The length of the resulting string is determined by the longest input string. If the input strings are of different lengths, the shorter strings are implicitly padded with zero-bytes to match the length of the longest string.

Bitwise Operations

• AND: Each bit in the result is set to 1 if the corresponding bits of all input strings are 1. Otherwise, it is set to 0.
• OR: Each bit in the result is set to 1 if at least one of the corresponding bits of the input strings is 1. Otherwise, it is set to 0.
• XOR: Each bit in the result is set to 1 if an odd number of the corresponding bits of the input strings are 1. Otherwise, it is set to 0.
• NOT: Each bit in the result is set to the complement of the corresponding bit in the input string (only one input string is allowed).

Error Handling

The BITOP command can raise errors in the following cases:

1. Wrong number of arguments: If the number of arguments is incorrect, DiceDB will return an error.

   • Error Message: ERR wrong number of arguments for 'bitop' command

2. Invalid operation: If the specified operation is not one of AND, OR, XOR, or NOT, DiceDB will return an error.

   • Error Message: ERR syntax error

3. Invalid number of keys for NOT operation: If more than one key is provided for the NOT operation, DiceDB will return an error.

   • Error Message: ERR BITOP NOT must be called with a single source key

4. Non-string keys: If any of the provided keys are not strings, DiceDB will return an error.

   • Error Message: WRONGTYPE Operation against a key holding the wrong kind of value

Example Usage

Example 1: Bitwise AND Operation

127.0.0.1:7379> SET key1 "foo"
OK
127.0.0.1:7379> SET key2 "bar"
OK
127.0.0.1:7379> BITOP AND result key1 key2
(integer) 3
127.0.0.1:7379> GET result
"bab"

Explanation:

• SET key1 "foo": Sets the value of key1 to “foo”.
• SET key2 "bar": Sets the value of key2 to “bar”.
• BITOP AND result key1 key2: Performs a bitwise AND operation between the values of key1 and key2, and stores the result in result.
• GET result: Retrieves the value of result.

Example 2: Bitwise OR Operation

127.0.0.1:7379> SET key1 "foo"
OK
127.0.0.1:7379> SET key2 "bar"
OK
127.0.0.1:7379> BITOP OR result key1 key2
(integer) 3
127.0.0.1:7379> GET result
"fo\x7f"

Explanation:

• SET key1 "foo": Sets the value of key1 to “foo”.
• SET key2 "bar": Sets the value of key2 to “bar”.
• BITOP OR result key1 key2: Performs a bitwise OR operation between the values of key1 and key2, and stores the result in result.
• GET result: Retrieves the value of result.

Example 3: Bitwise XOR Operation

127.0.0.1:7379> SET key1 "foo"
OK
127.0.0.1:7379> SET key2 "bar"
OK
127.0.0.1:7379> BITOP XOR result key1 key2
(integer) 3
127.0.0.1:7379> GET result
"\x04\x0e\x1d"

Explanation:

• SET key1 "foo": Sets the value of key1 to “foo”.
• SET key2 "bar": Sets the value of key2 to “bar”.
• BITOP XOR result key1 key2: Performs a bitwise XOR operation between the values of key1 and key2, and stores the result in result.
• GET result: Retrieves the value of result.

Example 4: Bitwise NOT Operation

127.0.0.1:7379> SET key1 "foo"
OK
127.0.0.1:7379> BITOP NOT result key1
(integer) 3
127.0.0.1:7379> GET result
"\x99\x90\x90"

Explanation:

• SET key1 "foo": Sets the value of key1 to “foo”.
• BITOP NOT result key1: Performs a bitwise NOT operation on the value of key1, and stores the result in result.
• GET result: Retrieves the value of result.