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Diffstat (limited to 'vendor/go.opencensus.io/trace/tracestate/tracestate.go')
-rw-r--r--vendor/go.opencensus.io/trace/tracestate/tracestate.go147
1 files changed, 147 insertions, 0 deletions
diff --git a/vendor/go.opencensus.io/trace/tracestate/tracestate.go b/vendor/go.opencensus.io/trace/tracestate/tracestate.go
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1// Copyright 2018, OpenCensus Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15// Package tracestate implements support for the Tracestate header of the
16// W3C TraceContext propagation format.
17package tracestate
18
19import (
20 "fmt"
21 "regexp"
22)
23
24const (
25 keyMaxSize = 256
26 valueMaxSize = 256
27 maxKeyValuePairs = 32
28)
29
30const (
31 keyWithoutVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,255}`
32 keyWithVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}`
33 keyFormat = `(` + keyWithoutVendorFormat + `)|(` + keyWithVendorFormat + `)`
34 valueFormat = `[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]`
35)
36
37var keyValidationRegExp = regexp.MustCompile(`^(` + keyFormat + `)$`)
38var valueValidationRegExp = regexp.MustCompile(`^(` + valueFormat + `)$`)
39
40// Tracestate represents tracing-system specific context in a list of key-value pairs. Tracestate allows different
41// vendors propagate additional information and inter-operate with their legacy Id formats.
42type Tracestate struct {
43 entries []Entry
44}
45
46// Entry represents one key-value pair in a list of key-value pair of Tracestate.
47type Entry struct {
48 // Key is an opaque string up to 256 characters printable. It MUST begin with a lowercase letter,
49 // and can only contain lowercase letters a-z, digits 0-9, underscores _, dashes -, asterisks *, and
50 // forward slashes /.
51 Key string
52
53 // Value is an opaque string up to 256 characters printable ASCII RFC0020 characters (i.e., the
54 // range 0x20 to 0x7E) except comma , and =.
55 Value string
56}
57
58// Entries returns a slice of Entry.
59func (ts *Tracestate) Entries() []Entry {
60 if ts == nil {
61 return nil
62 }
63 return ts.entries
64}
65
66func (ts *Tracestate) remove(key string) *Entry {
67 for index, entry := range ts.entries {
68 if entry.Key == key {
69 ts.entries = append(ts.entries[:index], ts.entries[index+1:]...)
70 return &entry
71 }
72 }
73 return nil
74}
75
76func (ts *Tracestate) add(entries []Entry) error {
77 for _, entry := range entries {
78 ts.remove(entry.Key)
79 }
80 if len(ts.entries)+len(entries) > maxKeyValuePairs {
81 return fmt.Errorf("adding %d key-value pairs to current %d pairs exceeds the limit of %d",
82 len(entries), len(ts.entries), maxKeyValuePairs)
83 }
84 ts.entries = append(entries, ts.entries...)
85 return nil
86}
87
88func isValid(entry Entry) bool {
89 return keyValidationRegExp.MatchString(entry.Key) &&
90 valueValidationRegExp.MatchString(entry.Value)
91}
92
93func containsDuplicateKey(entries ...Entry) (string, bool) {
94 keyMap := make(map[string]int)
95 for _, entry := range entries {
96 if _, ok := keyMap[entry.Key]; ok {
97 return entry.Key, true
98 }
99 keyMap[entry.Key] = 1
100 }
101 return "", false
102}
103
104func areEntriesValid(entries ...Entry) (*Entry, bool) {
105 for _, entry := range entries {
106 if !isValid(entry) {
107 return &entry, false
108 }
109 }
110 return nil, true
111}
112
113// New creates a Tracestate object from a parent and/or entries (key-value pair).
114// Entries from the parent are copied if present. The entries passed to this function
115// are inserted in front of those copied from the parent. If an entry copied from the
116// parent contains the same key as one of the entry in entries then the entry copied
117// from the parent is removed. See add func.
118//
119// An error is returned with nil Tracestate if
120// 1. one or more entry in entries is invalid.
121// 2. two or more entries in the input entries have the same key.
122// 3. the number of entries combined from the parent and the input entries exceeds maxKeyValuePairs.
123// (duplicate entry is counted only once).
124func New(parent *Tracestate, entries ...Entry) (*Tracestate, error) {
125 if parent == nil && len(entries) == 0 {
126 return nil, nil
127 }
128 if entry, ok := areEntriesValid(entries...); !ok {
129 return nil, fmt.Errorf("key-value pair {%s, %s} is invalid", entry.Key, entry.Value)
130 }
131
132 if key, duplicate := containsDuplicateKey(entries...); duplicate {
133 return nil, fmt.Errorf("contains duplicate keys (%s)", key)
134 }
135
136 tracestate := Tracestate{}
137
138 if parent != nil && len(parent.entries) > 0 {
139 tracestate.entries = append([]Entry{}, parent.entries...)
140 }
141
142 err := tracestate.add(entries)
143 if err != nil {
144 return nil, err
145 }
146 return &tracestate, nil
147}