Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 1 | // Copyright 2009 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // Deep equality test via reflection |
| 6 | |
| 7 | package reflect |
| 8 | |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 9 | import "unsafe" |
| 10 | |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 11 | // During deepValueEqual, must keep track of checks that are |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 12 | // in progress. The comparison algorithm assumes that all |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 13 | // checks in progress are true when it reencounters them. |
| 14 | // Visited comparisons are stored in a map indexed by visit. |
| 15 | type visit struct { |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 16 | a1 unsafe.Pointer |
| 17 | a2 unsafe.Pointer |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 18 | typ Type |
| 19 | } |
| 20 | |
| 21 | // Tests for deep equality using reflected types. The map argument tracks |
| 22 | // comparisons that have already been seen, which allows short circuiting on |
| 23 | // recursive types. |
| 24 | func deepValueEqual(v1, v2 Value, visited map[visit]bool, depth int) bool { |
| 25 | if !v1.IsValid() || !v2.IsValid() { |
| 26 | return v1.IsValid() == v2.IsValid() |
| 27 | } |
| 28 | if v1.Type() != v2.Type() { |
| 29 | return false |
| 30 | } |
| 31 | |
| 32 | // if depth > 10 { panic("deepValueEqual") } // for debugging |
Dan Willemsen | ebae302 | 2017-01-13 23:01:08 -0800 | [diff] [blame] | 33 | |
| 34 | // We want to avoid putting more in the visited map than we need to. |
| 35 | // For any possible reference cycle that might be encountered, |
| 36 | // hard(t) needs to return true for at least one of the types in the cycle. |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 37 | hard := func(k Kind) bool { |
| 38 | switch k { |
Dan Willemsen | ebae302 | 2017-01-13 23:01:08 -0800 | [diff] [blame] | 39 | case Map, Slice, Ptr, Interface: |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 40 | return true |
| 41 | } |
| 42 | return false |
| 43 | } |
| 44 | |
| 45 | if v1.CanAddr() && v2.CanAddr() && hard(v1.Kind()) { |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 46 | addr1 := unsafe.Pointer(v1.UnsafeAddr()) |
| 47 | addr2 := unsafe.Pointer(v2.UnsafeAddr()) |
| 48 | if uintptr(addr1) > uintptr(addr2) { |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 49 | // Canonicalize order to reduce number of entries in visited. |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 50 | // Assumes non-moving garbage collector. |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 51 | addr1, addr2 = addr2, addr1 |
| 52 | } |
| 53 | |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 54 | // Short circuit if references are already seen. |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 55 | typ := v1.Type() |
| 56 | v := visit{addr1, addr2, typ} |
| 57 | if visited[v] { |
| 58 | return true |
| 59 | } |
| 60 | |
| 61 | // Remember for later. |
| 62 | visited[v] = true |
| 63 | } |
| 64 | |
| 65 | switch v1.Kind() { |
| 66 | case Array: |
| 67 | for i := 0; i < v1.Len(); i++ { |
| 68 | if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) { |
| 69 | return false |
| 70 | } |
| 71 | } |
| 72 | return true |
| 73 | case Slice: |
| 74 | if v1.IsNil() != v2.IsNil() { |
| 75 | return false |
| 76 | } |
| 77 | if v1.Len() != v2.Len() { |
| 78 | return false |
| 79 | } |
| 80 | if v1.Pointer() == v2.Pointer() { |
| 81 | return true |
| 82 | } |
| 83 | for i := 0; i < v1.Len(); i++ { |
| 84 | if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) { |
| 85 | return false |
| 86 | } |
| 87 | } |
| 88 | return true |
| 89 | case Interface: |
| 90 | if v1.IsNil() || v2.IsNil() { |
| 91 | return v1.IsNil() == v2.IsNil() |
| 92 | } |
| 93 | return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1) |
| 94 | case Ptr: |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 95 | if v1.Pointer() == v2.Pointer() { |
| 96 | return true |
| 97 | } |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 98 | return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1) |
| 99 | case Struct: |
| 100 | for i, n := 0, v1.NumField(); i < n; i++ { |
| 101 | if !deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) { |
| 102 | return false |
| 103 | } |
| 104 | } |
| 105 | return true |
| 106 | case Map: |
| 107 | if v1.IsNil() != v2.IsNil() { |
| 108 | return false |
| 109 | } |
| 110 | if v1.Len() != v2.Len() { |
| 111 | return false |
| 112 | } |
| 113 | if v1.Pointer() == v2.Pointer() { |
| 114 | return true |
| 115 | } |
| 116 | for _, k := range v1.MapKeys() { |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 117 | val1 := v1.MapIndex(k) |
| 118 | val2 := v2.MapIndex(k) |
| 119 | if !val1.IsValid() || !val2.IsValid() || !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) { |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 120 | return false |
| 121 | } |
| 122 | } |
| 123 | return true |
| 124 | case Func: |
| 125 | if v1.IsNil() && v2.IsNil() { |
| 126 | return true |
| 127 | } |
| 128 | // Can't do better than this: |
| 129 | return false |
| 130 | default: |
| 131 | // Normal equality suffices |
| 132 | return valueInterface(v1, false) == valueInterface(v2, false) |
| 133 | } |
| 134 | } |
| 135 | |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 136 | // DeepEqual reports whether x and y are ``deeply equal,'' defined as follows. |
| 137 | // Two values of identical type are deeply equal if one of the following cases applies. |
| 138 | // Values of distinct types are never deeply equal. |
| 139 | // |
| 140 | // Array values are deeply equal when their corresponding elements are deeply equal. |
| 141 | // |
| 142 | // Struct values are deeply equal if their corresponding fields, |
| 143 | // both exported and unexported, are deeply equal. |
| 144 | // |
| 145 | // Func values are deeply equal if both are nil; otherwise they are not deeply equal. |
| 146 | // |
| 147 | // Interface values are deeply equal if they hold deeply equal concrete values. |
| 148 | // |
Dan Willemsen | ebae302 | 2017-01-13 23:01:08 -0800 | [diff] [blame] | 149 | // Map values are deeply equal when all of the following are true: |
| 150 | // they are both nil or both non-nil, they have the same length, |
| 151 | // and either they are the same map object or their corresponding keys |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 152 | // (matched using Go equality) map to deeply equal values. |
| 153 | // |
| 154 | // Pointer values are deeply equal if they are equal using Go's == operator |
| 155 | // or if they point to deeply equal values. |
| 156 | // |
| 157 | // Slice values are deeply equal when all of the following are true: |
| 158 | // they are both nil or both non-nil, they have the same length, |
| 159 | // and either they point to the same initial entry of the same underlying array |
| 160 | // (that is, &x[0] == &y[0]) or their corresponding elements (up to length) are deeply equal. |
| 161 | // Note that a non-nil empty slice and a nil slice (for example, []byte{} and []byte(nil)) |
| 162 | // are not deeply equal. |
| 163 | // |
| 164 | // Other values - numbers, bools, strings, and channels - are deeply equal |
| 165 | // if they are equal using Go's == operator. |
| 166 | // |
| 167 | // In general DeepEqual is a recursive relaxation of Go's == operator. |
| 168 | // However, this idea is impossible to implement without some inconsistency. |
| 169 | // Specifically, it is possible for a value to be unequal to itself, |
| 170 | // either because it is of func type (uncomparable in general) |
| 171 | // or because it is a floating-point NaN value (not equal to itself in floating-point comparison), |
| 172 | // or because it is an array, struct, or interface containing |
| 173 | // such a value. |
| 174 | // On the other hand, pointer values are always equal to themselves, |
| 175 | // even if they point at or contain such problematic values, |
| 176 | // because they compare equal using Go's == operator, and that |
| 177 | // is a sufficient condition to be deeply equal, regardless of content. |
| 178 | // DeepEqual has been defined so that the same short-cut applies |
| 179 | // to slices and maps: if x and y are the same slice or the same map, |
| 180 | // they are deeply equal regardless of content. |
Dan Willemsen | 214ca0d | 2017-08-09 12:44:57 -0700 | [diff] [blame] | 181 | // |
| 182 | // As DeepEqual traverses the data values it may find a cycle. The |
| 183 | // second and subsequent times that DeepEqual compares two pointer |
| 184 | // values that have been compared before, it treats the values as |
| 185 | // equal rather than examining the values to which they point. |
| 186 | // This ensures that DeepEqual terminates. |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 187 | func DeepEqual(x, y interface{}) bool { |
| 188 | if x == nil || y == nil { |
| 189 | return x == y |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 190 | } |
Dan Willemsen | 38f2dba | 2016-07-08 14:54:35 -0700 | [diff] [blame] | 191 | v1 := ValueOf(x) |
| 192 | v2 := ValueOf(y) |
Brent Austin | ba3052e | 2015-04-21 16:08:23 -0700 | [diff] [blame] | 193 | if v1.Type() != v2.Type() { |
| 194 | return false |
| 195 | } |
| 196 | return deepValueEqual(v1, v2, make(map[visit]bool), 0) |
| 197 | } |