// 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 import ( "internal/bytealg" "unsafe" ) // 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 unsafe.Pointer a2 unsafe.Pointer 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) bool { if !v1.IsValid() || !v2.IsValid() { return v1.IsValid() == v2.IsValid() } if v1.Type() != v2.Type() { return false } // We want to avoid putting more in the visited map than we need to. // For any possible reference cycle that might be encountered, // hard(v1, v2) needs to return true for at least one of the types in the cycle, // and it's safe and valid to get Value's internal pointer. hard := func(v1, v2 Value) bool { switch v1.Kind() { case Pointer: if v1.typ().PtrBytes == 0 { // not-in-heap pointers can't be cyclic. // At least, all of our current uses of runtime/internal/sys.NotInHeap // have that property. The runtime ones aren't cyclic (and we don't use // DeepEqual on them anyway), and the cgo-generated ones are // all empty structs. return false } fallthrough case Map, Slice, Interface: // Nil pointers cannot be cyclic. Avoid putting them in the visited map. return !v1.IsNil() && !v2.IsNil() } return false } if hard(v1, v2) { // For a Pointer or Map value, we need to check flagIndir, // which we do by calling the pointer method. // For Slice or Interface, flagIndir is always set, // and using v.ptr suffices. ptrval := func(v Value) unsafe.Pointer { switch v.Kind() { case Pointer, Map: return v.pointer() default: return v.ptr } } addr1 := ptrval(v1) addr2 := ptrval(v2) if uintptr(addr1) > uintptr(addr2) { // Canonicalize order to reduce number of entries in visited. // Assumes non-moving garbage collector. addr1, addr2 = addr2, addr1 } // Short circuit if references are 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) { return false } } return true case Slice: if v1.IsNil() != v2.IsNil() { return false } if v1.Len() != v2.Len() { return false } if v1.UnsafePointer() == v2.UnsafePointer() { return true } // Special case for []byte, which is common. if v1.Type().Elem().Kind() == Uint8 { return bytealg.Equal(v1.Bytes(), v2.Bytes()) } for i := 0; i < v1.Len(); i++ { if !deepValueEqual(v1.Index(i), v2.Index(i), visited) { return false } } return true case Interface: if v1.IsNil() || v2.IsNil() { return v1.IsNil() == v2.IsNil() } return deepValueEqual(v1.Elem(), v2.Elem(), visited) case Pointer: if v1.UnsafePointer() == v2.UnsafePointer() { return true } return deepValueEqual(v1.Elem(), v2.Elem(), visited) case Struct: for i, n := 0, v1.NumField(); i < n; i++ { if !deepValueEqual(v1.Field(i), v2.Field(i), visited) { return false } } return true case Map: if v1.IsNil() != v2.IsNil() { return false } if v1.Len() != v2.Len() { return false } if v1.UnsafePointer() == v2.UnsafePointer() { return true } iter := v1.MapRange() for iter.Next() { val1 := iter.Value() val2 := v2.MapIndex(iter.Key()) if !val1.IsValid() || !val2.IsValid() || !deepValueEqual(val1, val2, visited) { return false } } return true case Func: if v1.IsNil() && v2.IsNil() { return true } // Can't do better than this: return false case Int, Int8, Int16, Int32, Int64: return v1.Int() == v2.Int() case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return v1.Uint() == v2.Uint() case String: return v1.String() == v2.String() case Bool: return v1.Bool() == v2.Bool() case Float32, Float64: return v1.Float() == v2.Float() case Complex64, Complex128: return v1.Complex() == v2.Complex() default: // Normal equality suffices return valueInterface(v1, false) == valueInterface(v2, false) } } // DeepEqual reports whether x and y are “deeply equal,” defined as follows. // Two values of identical type are deeply equal if one of the following cases applies. // Values of distinct types are never deeply equal. // // Array values are deeply equal when their corresponding elements are deeply equal. // // Struct values are deeply equal if their corresponding fields, // both exported and unexported, are deeply equal. // // Func values are deeply equal if both are nil; otherwise they are not deeply equal. // // Interface values are deeply equal if they hold deeply equal concrete values. // // Map values are deeply equal when all of the following are true: // they are both nil or both non-nil, they have the same length, // and either they are the same map object or their corresponding keys // (matched using Go equality) map to deeply equal values. // // Pointer values are deeply equal if they are equal using Go's == operator // or if they point to deeply equal values. // // Slice values are deeply equal when all of the following are true: // they are both nil or both non-nil, they have the same length, // and either they point to the same initial entry of the same underlying array // (that is, &x[0] == &y[0]) or their corresponding elements (up to length) are deeply equal. // Note that a non-nil empty slice and a nil slice (for example, []byte{} and []byte(nil)) // are not deeply equal. // // Other values - numbers, bools, strings, and channels - are deeply equal // if they are equal using Go's == operator. // // In general DeepEqual is a recursive relaxation of Go's == operator. // However, this idea is impossible to implement without some inconsistency. // Specifically, it is possible for a value to be unequal to itself, // either because it is of func type (uncomparable in general) // or because it is a floating-point NaN value (not equal to itself in floating-point comparison), // or because it is an array, struct, or interface containing // such a value. // On the other hand, pointer values are always equal to themselves, // even if they point at or contain such problematic values, // because they compare equal using Go's == operator, and that // is a sufficient condition to be deeply equal, regardless of content. // DeepEqual has been defined so that the same short-cut applies // to slices and maps: if x and y are the same slice or the same map, // they are deeply equal regardless of content. // // As DeepEqual traverses the data values it may find a cycle. The // second and subsequent times that DeepEqual compares two pointer // values that have been compared before, it treats the values as // equal rather than examining the values to which they point. // This ensures that DeepEqual terminates. func DeepEqual(x, y any) bool { if x == nil || y == nil { return x == y } v1 := ValueOf(x) v2 := ValueOf(y) if v1.Type() != v2.Type() { return false } return deepValueEqual(v1, v2, make(map[visit]bool)) }