acpi: implement VM entity lookup and visit wrappers

src/gopheros/device/acpi/aml/vm.go

@@ -104,6 +104,30 @@ func (vm *VM) Init() *Error {
 	return nil
 }
 
+// Lookup traverses a potentially nested absolute AML path and returns the
+// Entity reachable via that path or nil if the path does not point to a
+// defined Entity.
+func (vm *VM) Lookup(absPath string) Entity {
+	if absPath == "" || absPath[0] != '\\' {
+		return nil
+	}
+
+	// If we just search for `\` return the root namespace
+	if len(absPath) == 1 {
+		return vm.rootNS
+	}
+
+	return scopeFindRelative(vm.rootNS, absPath[1:])
+}
+
+// Visit performs a DFS on the AML namespace tree invoking the visitor for each
+// encountered entity whose type matches entType. Namespace nodes are visited
+// in parent to child order a property which allows the supplied visitor
+// function to signal that it's children should not be visited.
+func (vm *VM) Visit(entType EntityType, visitorFn Visitor) {
+	scopeVisit(0, vm.rootNS, entType, visitorFn)
+}
+
 // defaultACPIScopes constructs a tree of scoped entities that correspond to
 // the predefined scopes contained in the ACPI specification and returns back
 // its root node.

src/gopheros/device/acpi/aml/vm_test.go

@@ -31,3 +31,66 @@ func TestVMInit(t *testing.T) {
 		}
 	})
 }
+
+func TestVMObjectLookups(t *testing.T) {
+	resolver := &mockResolver{
+		tableFiles: []string{"DSDT.aml"},
+	}
+	vm := NewVM(os.Stderr, resolver)
+	if err := vm.Init(); err != nil {
+		t.Fatal(err)
+	}
+
+	specs := []struct {
+		absPath string
+		match   bool
+	}{
+		{
+			``,
+			false,
+		},
+		{
+			`\`,
+			true,
+		},
+		{
+			`\_SB_.PCI0.SBRG.PIC_`,
+			true,
+		},
+		{
+			`\_SB_.PCI0.UNKNOWN_PATH`,
+			false,
+		},
+	}
+
+	for specIndex, spec := range specs {
+		foundMatch := vm.Lookup(spec.absPath) != nil
+		if foundMatch != spec.match {
+			t.Errorf("[spec %d] expected lookup match status to be %t", specIndex, spec.match)
+		}
+	}
+}
+
+func TestVMVisit(t *testing.T) {
+	resolver := &mockResolver{
+		tableFiles: []string{"parser-testsuite-DSDT.aml"},
+	}
+	vm := NewVM(os.Stderr, resolver)
+	if err := vm.Init(); err != nil {
+		t.Fatal(err)
+	}
+
+	var (
+		methodCount int
+		expCount    = 2
+	)
+
+	vm.Visit(EntityTypeMethod, func(_ int, ent Entity) bool {
+		methodCount++
+		return true
+	})
+
+	if methodCount != expCount {
+		t.Fatalf("expected visitor to be invoked for %d methods; got %d", expCount, methodCount)
+	}
+}