init commit for coverting to podman

engine/util.go

@@ -3,3 +3,80 @@
 // that can be found in the LICENSE file.
 
 package engine
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"reflect"
+)
+
+// if another module requires this function
+// then remove this function and place in util module
+func toPtr[T any](a T) *T {
+	ptr := new(T)
+	*ptr = a
+	return ptr
+}
+
+func flattenToBytes(data []string) []byte {
+	var total int
+	for i := range data {
+		total += len(data[i])
+	}
+
+	b := make([]byte, total)
+	for i := range data {
+		b = append(b, data[i]...)
+	}
+
+	return b
+}
+
+type ReaderClose struct {
+	ctx      context.Context
+	channels []chan string
+}
+
+func NewChansReadClose(ctx context.Context, channels ...chan string) ReaderClose {
+	return ReaderClose{
+		ctx:      ctx,
+		channels: channels,
+	}
+}
+
+func (c *ReaderClose) Read(p []byte) (int, error) {
+	cases := make([]reflect.SelectCase, len(c.channels))
+	for i := range c.channels {
+		cases[i] = reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(c.channels[i])}
+	}
+
+	remaining := len(cases)
+	for remaining > 0 {
+		select {
+		case <-c.ctx.Done():
+			c.Close()
+			return len(p), nil
+		default:
+		}
+
+		chosen, value, ok := reflect.Select(cases)
+		if !ok {
+			cases[chosen].Chan = reflect.ValueOf(nil)
+			remaining -= 1
+			continue
+		}
+
+		io.WriteString(bytes.NewBuffer(p), value.String())
+	}
+
+	return len(p), io.EOF
+}
+
+func (c *ReaderClose) Close() error {
+	for i := range c.channels {
+		close(c.channels[i])
+	}
+
+	return nil
+}