1 files changed, 145 insertions, 0 deletions
diff --git a/src/reflect/deepequal.go b/src/reflect/deepequal.go
new file mode 100644
index 000000000..f63715c9a
--- /dev/null
+++ b/src/reflect/deepequal.go
@@ -0,0 +1,145 @@
+// 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
+
+// During deepValueEqual, must keep track of checks that are
+// in progress.  The comparison algorithm assumes that all
+// checks in progress are true when it reencounters them.
+// Visited comparisons are stored in a map indexed by visit.
+type visit struct {
+	a1  uintptr
+	a2  uintptr
+	typ Type
+}
+
+// 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[visit]bool, depth int) bool {
+	if !v1.IsValid() || !v2.IsValid() {
+		return v1.IsValid() == v2.IsValid()
+	}
+	if v1.Type() != v2.Type() {
+		return false
+	}
+
+	// if depth > 10 { panic("deepValueEqual") }	// for debugging
+	hard := func(k Kind) bool {
+		switch k {
+		case Array, Map, Slice, Struct:
+			return true
+		}
+		return false
+	}
+
+	if v1.CanAddr() && v2.CanAddr() && hard(v1.Kind()) {
+		addr1 := v1.UnsafeAddr()
+		addr2 := v2.UnsafeAddr()
+		if addr1 > addr2 {
+			// Canonicalize order to reduce number of entries in visited.
+			addr1, addr2 = addr2, addr1
+		}
+
+		// Short circuit if references are identical ...
+		if addr1 == addr2 {
+			return true
+		}
+
+		// ... or already seen
+		typ := v1.Type()
+		v := visit{addr1, addr2, typ}
+		if visited[v] {
+			return true
+		}
+
+		// Remember for later.
+		visited[v] = true
+	}
+
+	switch v1.Kind() {
+	case Array:
+		for i := 0; i < v1.Len(); i++ {
+			if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case Slice:
+		if v1.IsNil() != v2.IsNil() {
+			return false
+		}
+		if v1.Len() != v2.Len() {
+			return false
+		}
+		if v1.Pointer() == v2.Pointer() {
+			return true
+		}
+		for i := 0; i < v1.Len(); i++ {
+			if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case Interface:
+		if v1.IsNil() || v2.IsNil() {
+			return v1.IsNil() == v2.IsNil()
+		}
+		return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
+	case Ptr:
+		return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
+	case Struct:
+		for i, n := 0, v1.NumField(); i < n; i++ {
+			if !deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case Map:
+		if v1.IsNil() != v2.IsNil() {
+			return false
+		}
+		if v1.Len() != v2.Len() {
+			return false
+		}
+		if v1.Pointer() == v2.Pointer() {
+			return true
+		}
+		for _, k := range v1.MapKeys() {
+			if !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case Func:
+		if v1.IsNil() && v2.IsNil() {
+			return true
+		}
+		// Can't do better than this:
+		return false
+	default:
+		// Normal equality suffices
+		return valueInterface(v1, false) == valueInterface(v2, false)
+	}
+}
+
+// DeepEqual tests for deep equality. It uses normal == equality where
+// possible but will scan elements of arrays, slices, maps, and fields of
+// structs. In maps, keys are compared with == but elements use deep
+// equality. DeepEqual correctly handles recursive types. Functions are equal
+// only if they are both nil.
+// An empty slice is not equal to a nil slice.
+func DeepEqual(a1, a2 interface{}) bool {
+	if a1 == nil || a2 == nil {
+		return a1 == a2
+	}
+	v1 := ValueOf(a1)
+	v2 := ValueOf(a2)
+	if v1.Type() != v2.Type() {
+		return false
+	}
+	return deepValueEqual(v1, v2, make(map[visit]bool), 0)
+}