Bitmasker

Bitmasker is a tool used to automate the creation of helper methods when dealing with bitmask-type constant flags. Given the name of an unsigned integer type T that has constants defined, bitmasker will create a new self-contained Go source file implementing the BitMask and fmt.Stringer interfaces.

Getting Started

To get up and running, follow the normal go install procedure:

go install github.com/go-curses/bitmasker

Example Usage

Bitmasker is intended to be used with go:generate but can operated standalone as well. For example:

Given this snippet:

package mental

//go:generate bitmasker -type=State
type State uint

const (
	Unconscious State = 0
	Conscious   State = 1 << iota
	Meditative
	Distracted
	Entertained = Distracted
)

Standalone usage:

bitmasker -type=State

Using go-generate

go generate

In both cases a new file named "state_bitmask.go" will be created with the following contents:

// Code generated by "bitmasker -type=State"; DO NOT EDIT.

package mental

import "strconv"

func _() {
	// An "invalid array index" compiler error signifies that the constant values have changed.
	// Re-run the bitmasker command to generate them again.
	var x [1]struct{}
	_ = x[Unconscious-0]
	_ = x[Conscious-2]
	_ = x[Meditative-4]
	_ = x[Distracted-8]
}

const (
	_State_name_0 = "Unconscious"
	_State_name_1 = "Conscious"
	_State_name_2 = "Meditative"
	_State_name_3 = "Distracted"
)

func (i State) String() (value string) {
	update := func(t State, n string) {
		if i.Has(t) {
			if len(value) > 0 {
				value += " | "
			}
			value += n
		}
	}
	update(State(0), _State_name_0)
	update(State(2), _State_name_1)
	update(State(4), _State_name_2)
	update(State(8), _State_name_3)
	if value == "" {
		return "State(" + strconv.FormatInt(int64(i), 10) + ")"
	}
	return
}

// Has returns TRUE if the given flag is present in the bitmask
func (i State) Has(m State) bool {
	if i == m {
		return true
	}
	return i&m != 0
}

// Set returns the bitmask with the given flag set
func (i State) Set(m State) State {
	return i | m
}

// Clear returns the bitmask with the given flag removed
func (i State) Clear(m State) State {
	return i &^ m
}

// Toggle returns the bitmask with the given flag toggled
func (i State) Toggle(m State) State {
	return i ^ m
}

Running the tests

Unit tests are provided and can be invoked using the normal Go pattern:

go test

Authors

• Kevin C. Krinke - Bitmasker author - kckrinke
• The Go Authors - Stringer derived sources - stringer

License

This project is licensed under the LGPL (specifically v3) - see the LICENSE.md file for details.

Acknowledgments

• Thanks to Golang.org for the stringer program that bitmasker sources are derived from.