Add a DeepEqual function to the reflect package

R=r,rsc
APPROVED=rsc
DELTA=167  (166 added, 0 deleted, 1 changed)
OCL=26982
CL=27017

src/lib/reflect/Makefile

@@ -40,6 +40,7 @@ O2=\
 
 O3=\
 	tostring.$O\
+	deepequal.$O\
 
 reflect.a: a1 a2 a3
 
@@ -52,7 +53,7 @@ a2:	$(O2)
 	rm -f $(O2)
 
 a3:	$(O3)
-	$(AR) grc reflect.a tostring.$O
+	$(AR) grc reflect.a tostring.$O deepequal.$O
 	rm -f $(O3)
 
 newpkg: clean

src/lib/reflect/all_test.go

@@ -356,3 +356,91 @@ func TestBigStruct(t *testing.T) {
 		t.Errorf("NewValue(%v).Interface().(big) = %v", b, b1);
 	}
 }
+
+type Basic struct {
+	x int;
+	y float32
+}
+
+type Recursive struct {
+	x int;
+	r *Recursive
+}
+
+type Complex struct {
+	a int;
+	b [3]*Complex;
+	c *string;
+	d map[float]float
+}
+
+type DeepEqualTest struct {
+	a, b interface{};
+	eq bool;
+}
+
+var deepEqualTests = []DeepEqualTest {
+	// Equalities
+	DeepEqualTest{ 1, 1, true },
+	DeepEqualTest{ int32(1), int32(1), true },
+	DeepEqualTest{ 0.5, 0.5, true },
+	DeepEqualTest{ float32(0.5), float32(0.5), true },
+	DeepEqualTest{ "hello", "hello", true },
+	DeepEqualTest{ make([]int, 10), make([]int, 10), true },
+	DeepEqualTest{ &[3]int{ 1, 2, 3 }, &[3]int{ 1, 2, 3 }, true },
+	DeepEqualTest{ Basic{ 1, 0.5 }, Basic{ 1, 0.5 }, true },
+	// Inequalities
+	DeepEqualTest{ 1, 2, false },
+	DeepEqualTest{ int32(1), int32(2), false },
+	DeepEqualTest{ 0.5, 0.6, false },
+	DeepEqualTest{ float32(0.5), float32(0.6), false },
+	DeepEqualTest{ "hello", "hey", false },
+	DeepEqualTest{ make([]int, 10), make([]int, 11), false },
+	DeepEqualTest{ &[3]int{ 1, 2, 3 }, &[3]int{ 1, 2, 4 }, false },
+	DeepEqualTest{ Basic{ 1, 0.5 }, Basic{ 1, 0.6 }, false },
+	// Mismatched types
+	DeepEqualTest{ 1, 1.0, false },
+	DeepEqualTest{ int32(1), int64(1), false },
+	DeepEqualTest{ 0.5, "hello", false },
+	DeepEqualTest{ []int{ 1, 2, 3 }, [3]int{ 1, 2, 3 }, false },
+	DeepEqualTest{ &[3]interface{} { 1, 2, 4 }, &[3]interface{} { 1, 2, "s" }, false },
+}
+
+func TestDeepEqual(t *testing.T) {
+	for i, test := range deepEqualTests {
+		if r := DeepEqual(test.a, test.b); r != test.eq {
+			t.Errorf("DeepEqual(%v, %v) = %v, want %v", test.a, test.b, r, test.eq);
+		}
+	}
+}
+
+func TestDeepEqualRecursiveStruct(t *testing.T) {
+	a, b := new(Recursive), new(Recursive);
+	*a = Recursive{ 12, a };
+	*b = Recursive{ 12, b };
+	if !DeepEqual(a, b) {
+		t.Error("DeepEqual(recursive same) = false, want true");
+	}
+}
+
+func TestDeepEqualComplexStruct(t *testing.T) {
+	m := make(map[float]float);
+	stra, strb := "hello", "hello";
+	a, b := new(Complex), new(Complex);
+	*a = Complex{5, [3]*Complex{a, b, a}, &stra, m};
+	*b = Complex{5, [3]*Complex{b, a, a}, &strb, m};
+	if !DeepEqual(a, b) {
+		t.Error("DeepEqual(complex same) = false, want true");
+	}
+}
+
+func TestDeepEqualComplexStructInequality(t *testing.T) {
+	m := make(map[float]float);
+	stra, strb := "hello", "helloo";  // Difference is here
+	a, b := new(Complex), new(Complex);
+	*a = Complex{5, [3]*Complex{a, b, a}, &stra, m};
+	*b = Complex{5, [3]*Complex{b, a, a}, &strb, m};
+	if DeepEqual(a, b) {
+		t.Error("DeepEqual(complex different) = true, want false");
+	}
+}

src/lib/reflect/deepequal.go

@@ -0,0 +1,78 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Deep equality test via reflection
+
+package reflect
+
+import "reflect"
+
+// Tests for deep equality using reflected types. The map argument tracks
+// comparisons that have already been seen, which allows short circuiting on
+// recursive types.
+func deepValueEqual(v1, v2 Value, visited map[Addr]Addr) bool {
+	if v1.Kind() != v2.Kind() {
+		return false;
+	}
+
+	// Short circuit if references are identical or already seen
+	addr1 := v1.Addr();
+	addr2 := v2.Addr();
+
+	if addr1 == addr2 {
+		return true;
+	}
+	if vaddr, ok := visited[addr1]; ok && vaddr == addr2 {
+		return true;
+	}
+	visited[addr1] = addr2;
+
+	switch v1.Kind() {
+	case ArrayKind:
+		arr1 := v1.(ArrayValue);
+		arr2 := v2.(ArrayValue);
+		if arr1.IsSlice() != arr2.IsSlice() || arr1.Len() != arr2.Len() {
+			return false;
+		}
+		for i := 0; i < arr1.Len(); i++ {
+			if !deepValueEqual(arr1.Elem(i), arr2.Elem(i), visited) {
+				return false;
+			}
+		}
+		return true;
+	case InterfaceKind:
+		return deepValueEqual(NewValue(v1.(InterfaceValue).Get()),
+				NewValue(v2.(InterfaceValue).Get()), visited);
+	case MapKind:
+		// TODO(dnadasi): Implement this fully once MapValue is implemented
+		return v1.Interface() == v2.Interface();
+	case PtrKind:
+		return deepValueEqual(v1.(PtrValue).Sub(), v2.(PtrValue).Sub(), visited);
+	case StructKind:
+		struct1 := v1.(StructValue);
+		struct2 := v2.(StructValue);
+		if struct1.Len() != struct2.Len() {
+			return false;
+		}
+		for i := 0; i < struct1.Len(); i++ {
+			if !deepValueEqual(struct1.Field(i), struct2.Field(i), visited) {
+				return false;
+			}
+		}
+		return true;
+	default:
+		// Normal equality suffices
+		return v1.Interface() == v2.Interface();
+	}
+
+	panic("Not reached");
+}
+
+// DeepEqual tests for deep equality. It uses normal == equality where possible
+// but will scan members of arrays, slices, and fields of structs. It correctly
+// handles recursive types. Until reflection supports maps, maps are equal iff
+// they are identical.
+func DeepEqual(a1, a2 interface{}) bool {
+	return deepValueEqual(NewValue(a1), NewValue(a2), make(map[Addr]Addr));
+}