mirror of
https://github.com/autc04/Retro68.git
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187 lines
5.6 KiB
Go
187 lines
5.6 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Deep equality test via reflection
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package reflect
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import "unsafe"
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// During deepValueEqual, must keep track of checks that are
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// in progress. The comparison algorithm assumes that all
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// checks in progress are true when it reencounters them.
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// Visited comparisons are stored in a map indexed by visit.
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type visit struct {
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a1 unsafe.Pointer
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a2 unsafe.Pointer
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typ Type
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}
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// Tests for deep equality using reflected types. The map argument tracks
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// comparisons that have already been seen, which allows short circuiting on
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// recursive types.
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func deepValueEqual(v1, v2 Value, visited map[visit]bool, depth int) bool {
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if !v1.IsValid() || !v2.IsValid() {
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return v1.IsValid() == v2.IsValid()
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}
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if v1.Type() != v2.Type() {
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return false
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}
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// if depth > 10 { panic("deepValueEqual") } // for debugging
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hard := func(k Kind) bool {
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switch k {
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case Array, Map, Slice, Struct:
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return true
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}
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return false
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}
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if v1.CanAddr() && v2.CanAddr() && hard(v1.Kind()) {
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addr1 := unsafe.Pointer(v1.UnsafeAddr())
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addr2 := unsafe.Pointer(v2.UnsafeAddr())
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if uintptr(addr1) > uintptr(addr2) {
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// Canonicalize order to reduce number of entries in visited.
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// Assumes non-moving garbage collector.
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addr1, addr2 = addr2, addr1
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}
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// Short circuit if references are already seen.
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typ := v1.Type()
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v := visit{addr1, addr2, typ}
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if visited[v] {
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return true
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}
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// Remember for later.
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visited[v] = true
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}
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switch v1.Kind() {
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case Array:
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for i := 0; i < v1.Len(); i++ {
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if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
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return false
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}
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}
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return true
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case Slice:
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if v1.IsNil() != v2.IsNil() {
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return false
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}
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if v1.Len() != v2.Len() {
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return false
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}
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if v1.Pointer() == v2.Pointer() {
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return true
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}
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for i := 0; i < v1.Len(); i++ {
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if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
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return false
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}
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}
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return true
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case Interface:
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if v1.IsNil() || v2.IsNil() {
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return v1.IsNil() == v2.IsNil()
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}
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return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
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case Ptr:
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if v1.Pointer() == v2.Pointer() {
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return true
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}
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return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
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case Struct:
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for i, n := 0, v1.NumField(); i < n; i++ {
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if !deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) {
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return false
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}
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}
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return true
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case Map:
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if v1.IsNil() != v2.IsNil() {
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return false
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}
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if v1.Len() != v2.Len() {
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return false
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}
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if v1.Pointer() == v2.Pointer() {
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return true
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}
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for _, k := range v1.MapKeys() {
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val1 := v1.MapIndex(k)
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val2 := v2.MapIndex(k)
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if !val1.IsValid() || !val2.IsValid() || !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) {
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return false
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}
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}
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return true
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case Func:
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if v1.IsNil() && v2.IsNil() {
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return true
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}
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// Can't do better than this:
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return false
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default:
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// Normal equality suffices
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return valueInterface(v1, false) == valueInterface(v2, false)
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}
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}
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// DeepEqual reports whether x and y are ``deeply equal,'' defined as follows.
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// Two values of identical type are deeply equal if one of the following cases applies.
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// Values of distinct types are never deeply equal.
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//
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// Array values are deeply equal when their corresponding elements are deeply equal.
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//
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// Struct values are deeply equal if their corresponding fields,
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// both exported and unexported, are deeply equal.
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//
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// Func values are deeply equal if both are nil; otherwise they are not deeply equal.
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//
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// Interface values are deeply equal if they hold deeply equal concrete values.
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//
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// Map values are deeply equal if they are the same map object
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// or if they have the same length and their corresponding keys
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// (matched using Go equality) map to deeply equal values.
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//
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// Pointer values are deeply equal if they are equal using Go's == operator
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// or if they point to deeply equal values.
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//
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// Slice values are deeply equal when all of the following are true:
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// they are both nil or both non-nil, they have the same length,
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// and either they point to the same initial entry of the same underlying array
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// (that is, &x[0] == &y[0]) or their corresponding elements (up to length) are deeply equal.
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// Note that a non-nil empty slice and a nil slice (for example, []byte{} and []byte(nil))
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// are not deeply equal.
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//
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// Other values - numbers, bools, strings, and channels - are deeply equal
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// if they are equal using Go's == operator.
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//
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// In general DeepEqual is a recursive relaxation of Go's == operator.
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// However, this idea is impossible to implement without some inconsistency.
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// Specifically, it is possible for a value to be unequal to itself,
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// either because it is of func type (uncomparable in general)
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// or because it is a floating-point NaN value (not equal to itself in floating-point comparison),
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// or because it is an array, struct, or interface containing
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// such a value.
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// On the other hand, pointer values are always equal to themselves,
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// even if they point at or contain such problematic values,
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// because they compare equal using Go's == operator, and that
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// is a sufficient condition to be deeply equal, regardless of content.
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// DeepEqual has been defined so that the same short-cut applies
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// to slices and maps: if x and y are the same slice or the same map,
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// they are deeply equal regardless of content.
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func DeepEqual(x, y interface{}) bool {
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if x == nil || y == nil {
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return x == y
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}
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v1 := ValueOf(x)
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v2 := ValueOf(y)
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if v1.Type() != v2.Type() {
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return false
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}
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return deepValueEqual(v1, v2, make(map[visit]bool), 0)
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}
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