Move vm into subdir

vm/memory.go

@@ -0,0 +1,39 @@
+package vm
+
+import "fmt"
+
+type memory struct {
+	entries []uint64
+}
+
+func newMemory(size uint64) *memory {
+	return &memory{
+		entries: make([]uint64, size),
+	}
+}
+
+func (mem *memory) readUnsigned(index uint64) (uint64, error) {
+	if index >= uint64(len(mem.entries)) {
+		return 0, fmt.Errorf("Invalid memory index: %016x", index)
+	}
+
+	return mem.entries[index], nil
+}
+
+func (mem *memory) mustReadUnsigned(index uint64) uint64 {
+	value, err := mem.readUnsigned(index)
+	if err != nil {
+		panic(err)
+	}
+	return value
+}
+
+func (mem *memory) writeUnsigned(index uint64, value uint64) error {
+	if index >= uint64(len(mem.entries)) {
+		return fmt.Errorf("Invalid memory index: %016x", index)
+	}
+
+	mem.entries[index] = value
+
+	return nil
+}