bitfield

package module
v2.3.0 Latest Latest
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 Go to latest Published: Jun 13, 2020 License: GPL-3.0 Imports: 2 Imported by: 1

Documentation

Overview

Package bitfield is for storing and manipulating bit-data.

There are two structs defined: BitField64 is in case you want to store 64 or less bits, while BitField is for storing arbitrary number of bits.

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type BitField 

type BitField struct {
	// contains filtered or unexported fields
}

BitField is a flexible size version of BitField64.

Most functions are chainable, positions outside the [0,len) range will get the modulo treatment, so Get(len) will return the 0th bit, Get(-1) will return the last bit: Get(len-1)

Most methods do not modify the underlying bitfield but create a new and return that. You can change this behaviour by calling .Mut() method. In this case all methods explicitely marked as 'Mutable.' will be modified in-place. This reduces allocations (for cases where speed does matter).

func New 

func New(len int) *BitField

New creates a new BitField of length len

func NewBitField added in v2.1.0 

func NewBitField(len int) *BitField

NewBitField creates a new BitField of length len and returns it. Panics if len<0

func (*BitField) And 

func (bf *BitField) And(bfOther *BitField) *BitField

And does a binary AND with bfOther. Panics if lengths differ. Mutable.

func (*BitField) Append 

func (bf *BitField) Append(other *BitField) *BitField

Append appends 'other' BitField to the end A newly created bitfield will be returned

func (*BitField) Clear 

func (bf *BitField) Clear(pos ...int) *BitField

Clear clears the bit(s) at position pos. Mutable.

Example 
bf := NewBitField(4).SetAll().Clear(0, -1)
fmt.Println(bf)

Output:

0110

func (*BitField) ClearAll 

func (bf *BitField) ClearAll() *BitField

ClearAll sets all bits to 1. Mutable.

func (*BitField) Clone 

func (bf *BitField) Clone() *BitField

Clone creates a copy of the bitfield and returns it

func (*BitField) Copy 

func (bf *BitField) Copy(dest *BitField) bool

Copy copies the content of BitField bf to dest. Returns false if the two bitfields differ in size, true otherwise

func (*BitField) Equal 

func (bf *BitField) Equal(bfOther *BitField) bool

Equal tells if two bitfields are equal or not

func (*BitField) Flip 

func (bf *BitField) Flip(pos ...int) *BitField

Flip inverts the bit(s) at position pos. Mutable.

func (*BitField) Get 

func (bf *BitField) Get(pos int) bool

Get returns the bit (as a boolean) at position pos

func (*BitField) Left 

func (bf *BitField) Left(count int) *BitField

Left returns count bits in the range of [0,count-1] as a new BitField Panics if count<0

func (*BitField) Len 

func (bf *BitField) Len() int

Len returns the number of bits the BitField holds

func (*BitField) Mid 

func (bf *BitField) Mid(pos, count int) *BitField

Mid returns counts bits from position pos as a new BitField Panics if count<0

func (*BitField) Mut 

func (bf *BitField) Mut() *BitField

Mut sets the mutable flag. This can reduce number of copying if execution time is important. Methods where description contains 'Mutable.' will modify content in-place.

Example 
bf := NewBitField(4).Set(0)
bf.Set(1) // this is set then discarded!
fmt.Println("without Mut():", bf)

bf.Mut().Set(1)
fmt.Println("with Mut():", bf)

Output:

without Mut(): 1000
with Mut(): 1100

func (*BitField) Not 

func (bf *BitField) Not() *BitField

Not does a binary NOT (inverts all bits). Mutable.

func (*BitField) OnesCount 

func (bf *BitField) OnesCount() int

OnesCount returns the number of bits set

func (*BitField) Or 

func (bf *BitField) Or(bfOther *BitField) *BitField

Or does a binary OR with bfOther. Panics if lengths differ. Mutable.

func (*BitField) Resize 

func (bf *BitField) Resize(newLen int) *BitField

Resize resizes the bitfield to newLen in size. Panics is newLen<0 Returns a newly allocated one, leaves the original intact. If newLen < Len() bits are lost at the end. If newLen > Len() the newly added bits will be zeroed. Mutable.

func (*BitField) Right 

func (bf *BitField) Right(count int) *BitField

Right returns count bits in the range of [63-count,63] as a new BitField Panics if count<0

func (*BitField) Rotate 

func (bf *BitField) Rotate(amount int) *BitField

Rotate rotates by amount bits and returns it If amount>0 it rotates towards higher bit positions, otherwise it rotates towards lower bit positions. Mutable.

func (*BitField) Set 

func (bf *BitField) Set(pos ...int) *BitField

Set sets the bit(s) at position pos. Mutable.

func (*BitField) SetAll 

func (bf *BitField) SetAll() *BitField

SetAll sets all bits to 1. Mutable.

func (*BitField) Shift 

func (bf *BitField) Shift(count int) *BitField

Shift shifts thes bitfield by count bits and returns it. If count is positive it shifts towards higher bit positions; If negative it shifts towards lower bit positions. Bits exiting at one end are discarded; bits entering at the other end are zeroed. Mutable.

Example (E1) 
bf := NewBitField(3).Set(0).Shift(1)
fmt.Println(bf)

Output:

010
Example (E2) 
bf := NewBitField(3).Set(0).Shift(3)
fmt.Println(bf)

Output:

000

func (*BitField) String added in v2.2.0 

func (bf *BitField) String() string

func (*BitField) Xor 

func (bf *BitField) Xor(bfOther *BitField) *BitField

Xor does a binary XOR with bfOther. Panics if lengths differ. Mutable.

type BitField64 added in v2.3.0 

type BitField64 uint64

BitField64 is a simple, quick, stack-based bit-field manipulator for 64 bits (or less) in length.

Methods are stateless and free from side-effects.

It was designed to be chainable. Range for position must be [0, 63]. position outside this range will get the modulo treatment, so 64 will point to the 0th element, -1 will address the last element (i.e. 63rd), -2 the one before (i.e. 62nd), etc.

func New64 added in v2.3.0 

func New64() BitField64

New64 returns a zeroed (all false) bit-field that can store 64 elements

func (BitField64) And added in v2.3.0 

func (bf64 BitField64) And(bfo BitField64) BitField64

And returns the binary AND of the two bitfields

func (BitField64) Clear added in v2.3.0 

func (bf64 BitField64) Clear(pos int) BitField64

Clear clears the bit at position pos

func (BitField64) ClearAll added in v2.3.0 

func (bf64 BitField64) ClearAll() BitField64

ClearAll returns a bitfield where all 64 bits are set

func (BitField64) ClearMul added in v2.3.0 

func (bf64 BitField64) ClearMul(pos ...int) BitField64

ClearMul sets the bits at position pos

func (BitField64) Flip added in v2.3.0 

func (bf64 BitField64) Flip(pos int) BitField64

Flip inverts the bit at position pos

Example 
a := New64().SetAll().Flip(0)
fmt.Println(a.String())

Output:

0111111111111111111111111111111111111111111111111111111111111111

func (BitField64) Get added in v2.3.0 

func (bf64 BitField64) Get(pos int) bool

Get returns true if bit at position pos is set, false otherwise

func (BitField64) Left added in v2.3.0 

func (bf64 BitField64) Left(count int) BitField64

Left returns leftmost count bits: [0, count-1]

func (BitField64) Mid added in v2.3.0 

func (bf64 BitField64) Mid(pos, count int) BitField64

Mid returns count bits from position pos

func (BitField64) Not added in v2.3.0 

func (bf64 BitField64) Not() BitField64

Not returns the bitfield with each bit inverted: 0 becomes 1, 1 becomes 0

func (BitField64) OnesCount added in v2.3.0 

func (bf64 BitField64) OnesCount() int

OnesCount returns the number of bits set

func (BitField64) Or added in v2.3.0 

func (bf64 BitField64) Or(bfo BitField64) BitField64

Or returns the binary OR of the two bitfields

func (BitField64) Right added in v2.3.0 

func (bf64 BitField64) Right(count int) BitField64

Right returns rightmost count bits [63-count, 63]

func (BitField64) Rotate added in v2.3.0 

func (bf64 BitField64) Rotate(count int) BitField64

Rotate rotates by count bits: Bits exiting at one end entering at the other end. If count is positive it rotates towards higher positions; If negative it rotates towards lower positions.

func (BitField64) Set added in v2.3.0 

func (bf64 BitField64) Set(pos int) BitField64

Set sets the bit at position pos

func (BitField64) SetAll added in v2.3.0 

func (bf64 BitField64) SetAll() BitField64

SetAll returns a bitfield where all 64 bits are set

func (BitField64) SetMul added in v2.3.0 

func (bf64 BitField64) SetMul(pos ...int) BitField64

SetMul sets the bits at position pos

Example 
a := New64().SetMul(2, 4)
fmt.Println(a.StringPretty())

Output:

00101

func (BitField64) Shift added in v2.3.0 

func (bf64 BitField64) Shift(count int) BitField64

Shift shift bits by count positions. Bits exiting at one end are discarded; bits entering at the other end are zeroed. If count is positive it shifts towards higher positions; If negative it shifts towards lower positions.

Example 
// SetAll(): all bits are 1
// Shift(3): 3 zeroes enter from left
// Left(5): takes first 3 zero bits and two 1s.
a := New64().SetAll().Shift(3).Left(5)
fmt.Println(a.StringPretty())

Output:

00011

func (BitField64) Shift2 added in v2.3.0 

func (bf64 BitField64) Shift2(count int) (ret, discarded BitField64)

Shift2 is same as Shift but it returns the discarded bits as well

func (BitField64) String added in v2.3.0 

func (bf64 BitField64) String() string

String returns the bit-representation of the bitfield Unlike in number to binary conversion here everything is reversed as position grows from 0 to 63, left to right So e.g. New().Set(2) print 0010000000000000000000000000000000000000000000000000000000000000

func (BitField64) StringPretty added in v2.3.0 

func (bf64 BitField64) StringPretty() string

StringPretty converts the bitfield to a string, but tailing zeros are dropped. So e.g. New().Set(2) will print "001"

func (BitField64) Xor added in v2.3.0 

func (bf64 BitField64) Xor(bfo BitField64) BitField64

Xor returns the binary XOR of the two bitfields

Example 
a := New64().SetMul(0, 3)
b := New64().Set(1)
fmt.Println(a.Xor(b).StringPretty())

Output:

1101

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