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Kent Hagermane566c2e2019-06-03 17:56:42 -04001// Copyright 2013 Dario Castañé. All rights reserved.
2// Copyright 2009 The Go Authors. All rights reserved.
3// Use of this source code is governed by a BSD-style
4// license that can be found in the LICENSE file.
5
6// Based on src/pkg/reflect/deepequal.go from official
7// golang's stdlib.
8
9package mergo
10
11import (
12 "errors"
13 "reflect"
14)
15
16// Errors reported by Mergo when it finds invalid arguments.
17var (
18 ErrNilArguments = errors.New("src and dst must not be nil")
19 ErrDifferentArgumentsTypes = errors.New("src and dst must be of same type")
20 ErrNotSupported = errors.New("only structs and maps are supported")
21 ErrExpectedMapAsDestination = errors.New("dst was expected to be a map")
22 ErrExpectedStructAsDestination = errors.New("dst was expected to be a struct")
23)
24
25// During deepMerge, must keep track of checks that are
26// in progress. The comparison algorithm assumes that all
27// checks in progress are true when it reencounters them.
28// Visited are stored in a map indexed by 17 * a1 + a2;
29type visit struct {
30 ptr uintptr
31 typ reflect.Type
32 next *visit
33}
34
35// From src/pkg/encoding/json/encode.go.
36func isEmptyValue(v reflect.Value) bool {
37 switch v.Kind() {
38 case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
39 return v.Len() == 0
40 case reflect.Bool:
41 return !v.Bool()
42 case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
43 return v.Int() == 0
44 case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
45 return v.Uint() == 0
46 case reflect.Float32, reflect.Float64:
47 return v.Float() == 0
48 case reflect.Interface, reflect.Ptr:
49 if v.IsNil() {
50 return true
51 }
52 return isEmptyValue(v.Elem())
53 case reflect.Func:
54 return v.IsNil()
55 case reflect.Invalid:
56 return true
57 }
58 return false
59}
60
61func resolveValues(dst, src interface{}) (vDst, vSrc reflect.Value, err error) {
62 if dst == nil || src == nil {
63 err = ErrNilArguments
64 return
65 }
66 vDst = reflect.ValueOf(dst).Elem()
67 if vDst.Kind() != reflect.Struct && vDst.Kind() != reflect.Map {
68 err = ErrNotSupported
69 return
70 }
71 vSrc = reflect.ValueOf(src)
72 // We check if vSrc is a pointer to dereference it.
73 if vSrc.Kind() == reflect.Ptr {
74 vSrc = vSrc.Elem()
75 }
76 return
77}
78
79// Traverses recursively both values, assigning src's fields values to dst.
80// The map argument tracks comparisons that have already been seen, which allows
81// short circuiting on recursive types.
82func deeper(dst, src reflect.Value, visited map[uintptr]*visit, depth int) (err error) {
83 if dst.CanAddr() {
84 addr := dst.UnsafeAddr()
85 h := 17 * addr
86 seen := visited[h]
87 typ := dst.Type()
88 for p := seen; p != nil; p = p.next {
89 if p.ptr == addr && p.typ == typ {
90 return nil
91 }
92 }
93 // Remember, remember...
94 visited[h] = &visit{addr, typ, seen}
95 }
96 return // TODO refactor
97}