Start work on a SHM implementation in Go

tools/utils/shm/shm_test.go

@@ -0,0 +1,43 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package shm
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"math/rand"
+	"os"
+	"reflect"
+	"testing"
+)
+
+var _ = fmt.Print
+
+func TestSHM(t *testing.T) {
+	data := make([]byte, 13347)
+	rand.Read(data)
+	mm, err := CreateTemp("test-kitty-shm-", uint64(len(data)))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	copy(mm.Slice(), data)
+	mm.Close()
+
+	g, err := Open(mm.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	data2 := g.Slice()
+	if !reflect.DeepEqual(data, data2) {
+		t.Fatalf("Could not read back written data: Written data length: %d Read data length: %d", len(data), len(data2))
+	}
+	g.Close()
+	g.Unlink()
+	_, err = os.Stat(mm.Name())
+	if !errors.Is(err, fs.ErrNotExist) {
+		t.Fatalf("Unlinking %s did not work", mm.Name())
+	}
+
+}