internal/byteslice: rename package unsafe

All functions left in the old package unsafe were provided byte slice
views of other types. Rename the package accordingly and avoid a name
clash with the standard library package unsafe.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

internal/byteslice/byteslice.go

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// Package byteslice provides byte slice views of other Go values  such as
+// slices and structs.
+package byteslice
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// Struct returns a byte slice view of a struct.
+func Struct(s interface{}) []byte {
+	v := reflect.ValueOf(s).Elem()
+	sz := int(v.Type().Size())
+	var res []byte
+	h := (*reflect.SliceHeader)(unsafe.Pointer(&res))
+	h.Data = uintptr(unsafe.Pointer(v.UnsafeAddr()))
+	h.Cap = sz
+	h.Len = sz
+	return res
+}
+
+// Slice returns a byte slice view of a slice.
+func Slice(s interface{}) []byte {
+	v := reflect.ValueOf(s)
+	first := v.Index(0)
+	sz := int(first.Type().Size())
+	var res []byte
+	h := (*reflect.SliceHeader)(unsafe.Pointer(&res))
+	h.Data = first.UnsafeAddr()
+	h.Cap = v.Cap() * sz
+	h.Len = v.Len() * sz
+	return res
+}