device: add generic methods for working with user+session devices (#3710)

pkg/slices/slices.go

@@ -0,0 +1,47 @@
+// Package slices contains functions for working with slices.
+package slices
+
+// Contains returns true if e is in s.
+func Contains[S ~[]E, E comparable](s S, e E) bool {
+	for _, el := range s {
+		if el == e {
+			return true
+		}
+	}
+	return false
+}
+
+// Filter returns a new slice containing only those elements for which f(element) is true.
+func Filter[S ~[]E, E any](s S, f func(E) bool) S {
+	var ns S
+	for _, el := range s {
+		if f(el) {
+			ns = append(ns, el)
+		}
+	}
+	return ns
+}
+
+// Remove removes e from s.
+func Remove[S ~[]E, E comparable](s S, e E) S {
+	var ns S
+	for _, el := range s {
+		if el != e {
+			ns = append(ns, el)
+		}
+	}
+	return ns
+}
+
+// Unique returns the unique elements of s.
+func Unique[S ~[]E, E comparable](s S) S {
+	var ns S
+	h := map[E]struct{}{}
+	for _, el := range s {
+		if _, ok := h[el]; !ok {
+			h[el] = struct{}{}
+			ns = append(ns, el)
+		}
+	}
+	return ns
+}