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-rw-r--r--src/pkg/reflect/deepequal.go126
1 files changed, 126 insertions, 0 deletions
diff --git a/src/pkg/reflect/deepequal.go b/src/pkg/reflect/deepequal.go
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+// 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 are stored in a map indexed by 17 * a1 + a2;
+type visit struct {
+ a1 uintptr
+ a2 uintptr
+ typ Type
+ next *visit
+}
+
+// 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[uintptr]*visit, depth int) (b 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
+
+ if v1.CanAddr() && v2.CanAddr() {
+ 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
+ h := 17*addr1 + addr2
+ seen := visited[h]
+ typ := v1.Type()
+ for p := seen; p != nil; p = p.next {
+ if p.a1 == addr1 && p.a2 == addr2 && p.typ == typ {
+ return true
+ }
+ }
+
+ // Remember for later.
+ visited[h] = &visit{addr1, addr2, typ, seen}
+ }
+
+ switch v1.Kind() {
+ case Array:
+ if v1.Len() != v2.Len() {
+ return false
+ }
+ 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.Len() != v2.Len() {
+ return false
+ }
+ 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.Len() != v2.Len() {
+ return false
+ }
+ for _, k := range v1.MapKeys() {
+ if !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) {
+ 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.
+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[uintptr]*visit), 0)
+}