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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.IsNil() != v2.IsNil() {
return false
}
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.IsNil() != v2.IsNil() {
return false
}
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
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[uintptr]*visit), 0)
}
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