nodemcu-firmware/docs/modules/bit.md

bit Module

Since	Origin / Contributor	Maintainer	Source
2014-12-24	https://github.com/LuaDist/bitlib, Zeroday	Zeroday	bit.c

Bit manipulation support, on 32bit integers.

bit.arshift()

Arithmetic right shift a number equivalent to value >> shift in C.

Syntax

bit.arshift(value, shift)

Parameters

• value the value to shift
• shift positions to shift

Returns

the number shifted right (arithmetically)

Example

bit.arshift(3, 1) -- returns 1
-- Using a 4 bits representation: 0011 >> 1 == 0001

bit.band()

Bitwise AND, equivalent to val1 & val2 & ... & valn in C.

Syntax

bit.band(val1, val2 [, ... valn])

Parameters

• val1 first AND argument
• val2 second AND argument
• ...valn ...nth AND argument

Returns

the bitwise AND of all the arguments (number)

Example

bit.band(3, 2) -- returns 2
-- Using a 4 bits representation: 0011 & 0010 == 0010

bit.bit()

Generate a number with a 1 bit (used for mask generation). Equivalent to 1 << position in C.

Syntax

bit.bit(position)

Parameters

position position of the bit that will be set to 1

Returns

a number with only one 1 bit at position (the rest are set to 0)

Example

bit.bit(4) -- returns 16

bit.bnot()

Bitwise negation, equivalent to ~value in C.

Syntax

bit.bnot(value)

Parameters

value the number to negate

Returns

the bitwise negated value of the number

bit.bor()

Bitwise OR, equivalent to val1 | val2 | ... | valn in C.

Syntax

bit.bor(val1, val2 [, ... valn])

Parameters

• val1 first OR argument.
• val2 second OR argument.
• ...valn ...nth OR argument

Returns

the bitwise OR of all the arguments (number)

Example

bit.bor(3, 2) -- returns 3
-- Using a 4 bits representation: 0011 | 0010 == 0011

bit.bxor()

Bitwise XOR, equivalent to val1 ^ val2 ^ ... ^ valn in C.

Syntax

bit.bxor(val1, val2 [, ... valn])

Parameters

• val1 first XOR argument
• val2 second XOR argument
• ...valn ...nth XOR argument

Returns

the bitwise XOR of all the arguments (number)

Example

bit.bxor(3, 2) -- returns 1
-- Using a 4 bits representation: 0011 ^ 0010 == 0001

bit.clear()

Clear bits in a number.

Syntax

bit.clear(value, pos1 [, ... posn])

Parameters

• value the base number
• pos1 position of the first bit to clear
• ...posn position of thet nth bit to clear

Returns

the number with the bit(s) cleared in the given position(s)

Example

bit.clear(3, 0) -- returns 2

bit.isclear()

Test if a given bit is cleared.

Syntax

bit.isclear(value, position)

Parameters

• value the value to test
• position bit position to test

Returns

true if the bit at the given position is 0, false otherwise

Example

bit.isclear(2, 0) -- returns true

bit.isset()

Test if a given bit is set.

Syntax

bit.isset(value, position)

Parameters

• value the value to test
• position bit position to test

Returns

true if the bit at the given position is 1, false otherwise

Example

bit.isset(2, 0) -- returns false

bit.lshift()

Left-shift a number, equivalent to value << shift in C.

Syntax

bit.lshift(value, shift)

Parameters

• value the value to shift
• shift positions to shift

Returns

the number shifted left

Example

bit.lshift(2, 2) -- returns 8
-- Using a 4 bits representation: 0010 << 2 == 1000

bit.rshift()

Logical right shift a number, equivalent to ( unsigned )value >> shift in C.

Syntax

bit.rshift(value, shift)

Parameters

• value the value to shift.
• shift positions to shift.

Returns

the number shifted right (logically)

Example

bit.rshift(2, 1) -- returns 1
-- Using a 4 bits representation: 0010 >> 1 == 0001

bit.set()

Set bits in a number.

Syntax

bit.set(value, pos1 [, ... posn ])

Parameters

• value the base number.
• pos1 position of the first bit to set.
• ...posn position of the nth bit to set.

Returns

the number with the bit(s) set in the given position(s)

Example

bit.set(2, 0) -- returns 3