Add support for generating enums as bitfields

README.md

@@ -340,6 +340,7 @@ GLOBAL OPTIONS:
    --buildtag value, -b value [ --buildtag value, -b value ]  Adds build tags to a generated enum file.
    --output-suffix .go                                        Changes the default filename suffix of _enum to something else.  .go will be appended to the end of the string no matter what, so that `_test.go` cases can be accommodated
    --no-iota                                                  Disables the use of iota in generated enums. (default: false)
+   --bitfield                                                 Generates the values as bit fields. (default: false)
    --help, -h                                                 show help
    --version, -v                                              print the version
 ```

example/enum_bitfield.go

@@ -0,0 +1,43 @@
+//go:generate ../bin/go-enum --names -b example --bitfield --values
+
+package example
+
+/*
+ENUM(
+
+E2P0
+E2P1
+E2P2
+E2P3
+E2P4
+E2P5
+E2P6
+E2P7
+E2P8
+E2P9
+E2P10
+E2P11
+E2P12
+E2P13
+E2P14
+E2P15
+E2P16
+E2P17
+E2P18
+E2P19
+E2P20
+E2P21
+E2P22
+E2P23
+E2P24
+E2P25
+E2P26
+E2P27
+E2P28
+E2P29
+E2P30
+E2P31
+
+)
+*/
+type Enum32bitfield uint32

example/enum_bitfield_test.go

@@ -0,0 +1,49 @@
+//go:build example
+// +build example
+
+package example
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEnum32bitfield(t *testing.T) {
+	t.Parallel()
+
+	allFields := Enum32bitfieldValues()
+
+	// Generate all pairs (i, j) where i < j to avoid duplicates
+	testCases := make([]struct {
+		name   string
+		field1 Enum32bitfield
+		field2 Enum32bitfield
+	}, 0, len(allFields)*(len(allFields)-1)/2)
+
+	for i := 0; i < len(allFields); i++ {
+		for j := i + 1; j < len(allFields); j++ {
+			testCases = append(testCases, struct {
+				name   string
+				field1 Enum32bitfield
+				field2 Enum32bitfield
+			}{
+				name:   allFields[i].String() + "_" + allFields[j].String(),
+				field1: allFields[i],
+				field2: allFields[j],
+			})
+		}
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			// Collapse the two views
+			collapsed := tc.field1 | tc.field2
+
+			assert.Equal(t, tc.field1, collapsed^tc.field2)
+			assert.Equal(t, tc.field2, collapsed^tc.field1)
+		})
+	}
+}

generator/enum.tmpl

@@ -23,6 +23,7 @@ const (
 {{- $enumType := .enum.Type -}}
 {{- $noComments := .nocomments -}}
 {{- $noIota := .noIota -}}
+{{- $bitField := .bitField -}}
 {{- $vars := dict "lastoffset" "0" -}}
 {{ range $rIndex, $value := .enum.Values }}
 	{{- $lastOffset := pluck "lastoffset" $vars | first }}{{ $offset := offset $rIndex $enumType $value }}
@@ -32,7 +33,7 @@ const (
 	// {{$value.Comment}}
 	{{- end}}
 		{{if $noIota }}{{$value.PrefixedName}} {{$enumName}} = {{directVal $enumType $value}}{{else -}}
-    {{$value.PrefixedName}} {{ if eq $rIndex 0 }}{{$enumName}} = iota{{ if ne "0" $offset }} + {{ $offset }}{{end}}{{else if ne $lastOffset $offset }}{{$enumName}} = iota + {{ $offset }}{{end}}{{$_ := set $vars "lastoffset" $offset}}
+    {{$value.PrefixedName}} {{ if eq $rIndex 0 }}{{$enumName}} = {{if $bitField }}1<<{{end}}iota{{ if ne "0" $offset }} + {{ $offset }}{{end}}{{else if ne $lastOffset $offset }}{{$enumName}} = iota + {{ $offset }}{{end}}{{$_ := set $vars "lastoffset" $offset}}
 		{{- end}}
 {{- end}}
 )