File: structhash.go

package info (click to toggle)
golang-github-cnf-structhash 0.0~git20180104.62a607e-2
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, sid
  • size: 92 kB
  • sloc: makefile: 2
file content (257 lines) | stat: -rw-r--r-- 6,058 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
package structhash

import (
	"bytes"
	"crypto/md5"
	"crypto/sha1"
	"fmt"
	"reflect"
	"sort"
	"strconv"
	"strings"
)

// Version returns the version of the supplied hash as an integer
// or -1 on failure
func Version(h string) int {
	if h == "" {
		return -1
	}
	if h[0] != 'v' {
		return -1
	}
	if spos := strings.IndexRune(h[1:], '_'); spos >= 0 {
		n, e := strconv.Atoi(h[1 : spos+1])
		if e != nil {
			return -1
		}
		return n
	}
	return -1
}

// Hash takes a data structure and returns a hash string of that data structure
// at the version asked.
//
// This function uses md5 hashing function and default formatter. See also Dump()
// function.
func Hash(c interface{}, version int) (string, error) {
	return fmt.Sprintf("v%d_%x", version, Md5(c, version)), nil
}

// Dump takes a data structure and returns its byte representation. This can be
// useful if you need to use your own hashing function or formatter.
func Dump(c interface{}, version int) []byte {
	return serialize(c, version)
}

// Md5 takes a data structure and returns its md5 hash.
// This is a shorthand for md5.Sum(Dump(c, version)).
func Md5(c interface{}, version int) []byte {
	sum := md5.Sum(Dump(c, version))
	return sum[:]
}

// Sha1 takes a data structure and returns its sha1 hash.
// This is a shorthand for sha1.Sum(Dump(c, version)).
func Sha1(c interface{}, version int) []byte {
	sum := sha1.Sum(Dump(c, version))
	return sum[:]
}

type item struct {
	name  string
	value reflect.Value
}

type itemSorter []item

func (s itemSorter) Len() int {
	return len(s)
}

func (s itemSorter) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}

func (s itemSorter) Less(i, j int) bool {
	return s[i].name < s[j].name
}

type tagError string

func (e tagError) Error() string {
	return "incorrect tag " + string(e)
}

type structFieldFilter func(reflect.StructField, *item) (bool, error)

func writeValue(buf *bytes.Buffer, val reflect.Value, fltr structFieldFilter) {
	switch val.Kind() {
	case reflect.String:
		buf.WriteByte('"')
		buf.WriteString(val.String())
		buf.WriteByte('"')
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		buf.WriteString(strconv.FormatInt(val.Int(), 10))
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		buf.WriteString(strconv.FormatUint(val.Uint(), 10))
	case reflect.Float32, reflect.Float64:
		buf.WriteString(strconv.FormatFloat(val.Float(), 'E', -1, 64))
	case reflect.Bool:
		if val.Bool() {
			buf.WriteByte('t')
		} else {
			buf.WriteByte('f')
		}
	case reflect.Ptr:
		if !val.IsNil() || val.Type().Elem().Kind() == reflect.Struct {
			writeValue(buf, reflect.Indirect(val), fltr)
		} else {
			writeValue(buf, reflect.Zero(val.Type().Elem()), fltr)
		}
	case reflect.Array, reflect.Slice:
		buf.WriteByte('[')
		len := val.Len()
		for i := 0; i < len; i++ {
			if i != 0 {
				buf.WriteByte(',')
			}
			writeValue(buf, val.Index(i), fltr)
		}
		buf.WriteByte(']')
	case reflect.Map:
		mk := val.MapKeys()
		items := make([]item, len(mk), len(mk))
		// Get all values
		for i, _ := range items {
			items[i].name = formatValue(mk[i], fltr)
			items[i].value = val.MapIndex(mk[i])
		}

		// Sort values by key
		sort.Sort(itemSorter(items))

		buf.WriteByte('[')
		for i, _ := range items {
			if i != 0 {
				buf.WriteByte(',')
			}
			buf.WriteString(items[i].name)
			buf.WriteByte(':')
			writeValue(buf, items[i].value, fltr)
		}
		buf.WriteByte(']')
	case reflect.Struct:
		vtype := val.Type()
		flen := vtype.NumField()
		items := make([]item, 0, flen)
		// Get all fields
		for i := 0; i < flen; i++ {
			field := vtype.Field(i)
			it := item{field.Name, val.Field(i)}
			if fltr != nil {
				ok, err := fltr(field, &it)
				if err != nil && strings.Contains(err.Error(), "method:") {
					panic(err)
				}
				if !ok {
					continue
				}
			}
			items = append(items, it)
		}
		// Sort fields by name
		sort.Sort(itemSorter(items))

		buf.WriteByte('{')
		for i, _ := range items {
			if i != 0 {
				buf.WriteByte(',')
			}
			buf.WriteString(items[i].name)
			buf.WriteByte(':')
			writeValue(buf, items[i].value, fltr)
		}
		buf.WriteByte('}')
	case reflect.Interface:
		writeValue(buf, reflect.ValueOf(val.Interface()), fltr)
	default:
		buf.WriteString(val.String())
	}
}

func formatValue(val reflect.Value, fltr structFieldFilter) string {
	if val.Kind() == reflect.String {
		return "\"" + val.String() + "\""
	}

	var buf bytes.Buffer
	writeValue(&buf, val, fltr)

	return string(buf.Bytes())
}

func filterField(f reflect.StructField, i *item, version int) (bool, error) {
	var err error
	ver := 0
	lastver := -1
	if str := f.Tag.Get("hash"); str != "" {
		if str == "-" {
			return false, nil
		}
		for _, tag := range strings.Split(str, " ") {
			args := strings.Split(strings.TrimSpace(tag), ":")
			if len(args) != 2 {
				return false, tagError(tag)
			}
			switch args[0] {
			case "name":
				i.name = args[1]
			case "version":
				if ver, err = strconv.Atoi(args[1]); err != nil {
					return false, tagError(tag)
				}
			case "lastversion":
				if lastver, err = strconv.Atoi(args[1]); err != nil {
					return false, tagError(tag)
				}
			case "method":
				property, found := f.Type.MethodByName(strings.TrimSpace(args[1]))
				if !found || property.Type.NumOut() != 1 {
					return false, tagError(tag)
				}
				i.value = property.Func.Call([]reflect.Value{i.value})[0]
			}
		}
	} else {
		if str := f.Tag.Get("lastversion"); str != "" {
			if lastver, err = strconv.Atoi(str); err != nil {
				return false, tagError(str)
			}
		}
		if str := f.Tag.Get("version"); str != "" {
			if ver, err = strconv.Atoi(str); err != nil {
				return false, tagError(str)
			}
		}
	}
	if lastver != -1 && lastver < version {
		return false, nil
	}
	if ver > version {
		return false, nil
	}
	return true, nil
}

func serialize(object interface{}, version int) []byte {
	var buf bytes.Buffer

	writeValue(&buf, reflect.ValueOf(object),
		func(f reflect.StructField, i *item) (bool, error) {
			return filterField(f, i, version)
		})

	return buf.Bytes()
}