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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) bool {
if v1 == nil || v2 == nil {
return v1 == v2
}
if v1.Type() != v2.Type() {
return false
}
// if depth > 10 { panic("deepValueEqual") } // for debugging
addr1 := v1.Addr()
addr2 := v2.Addr()
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 v := v1.(type) {
case *ArrayValue:
arr1 := v
arr2 := v2.(*ArrayValue)
if arr1.Len() != arr2.Len() {
return false
}
for i := 0; i < arr1.Len(); i++ {
if !deepValueEqual(arr1.Elem(i), arr2.Elem(i), visited, depth+1) {
return false
}
}
return true
case *SliceValue:
arr1 := v
arr2 := v2.(*SliceValue)
if arr1.Len() != arr2.Len() {
return false
}
for i := 0; i < arr1.Len(); i++ {
if !deepValueEqual(arr1.Elem(i), arr2.Elem(i), visited, depth+1) {
return false
}
}
return true
case *InterfaceValue:
i1 := v.Interface()
i2 := v2.Interface()
if i1 == nil || i2 == nil {
return i1 == i2
}
return deepValueEqual(NewValue(i1), NewValue(i2), visited, depth+1)
case *PtrValue:
return deepValueEqual(v.Elem(), v2.(*PtrValue).Elem(), visited, depth+1)
case *StructValue:
struct1 := v
struct2 := v2.(*StructValue)
for i, n := 0, v.NumField(); i < n; i++ {
if !deepValueEqual(struct1.Field(i), struct2.Field(i), visited, depth+1) {
return false
}
}
return true
case *MapValue:
map1 := v
map2 := v2.(*MapValue)
if map1.Len() != map2.Len() {
return false
}
for _, k := range map1.Keys() {
if !deepValueEqual(map1.Elem(k), map2.Elem(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 := NewValue(a1)
v2 := NewValue(a2)
if v1.Type() != v2.Type() {
return false
}
return deepValueEqual(v1, v2, make(map[uintptr]*visit), 0)
}
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