| // Copyright 2018, OpenCensus Authors |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| // Package tracestate implements support for the Tracestate header of the |
| // W3C TraceContext propagation format. |
| package tracestate |
| |
| import ( |
| "fmt" |
| "regexp" |
| ) |
| |
| const ( |
| keyMaxSize = 256 |
| valueMaxSize = 256 |
| maxKeyValuePairs = 32 |
| ) |
| |
| const ( |
| keyWithoutVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,255}` |
| keyWithVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}` |
| keyFormat = `(` + keyWithoutVendorFormat + `)|(` + keyWithVendorFormat + `)` |
| valueFormat = `[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]` |
| ) |
| |
| var keyValidationRegExp = regexp.MustCompile(`^(` + keyFormat + `)$`) |
| var valueValidationRegExp = regexp.MustCompile(`^(` + valueFormat + `)$`) |
| |
| // Tracestate represents tracing-system specific context in a list of key-value pairs. Tracestate allows different |
| // vendors propagate additional information and inter-operate with their legacy Id formats. |
| type Tracestate struct { |
| entries []Entry |
| } |
| |
| // Entry represents one key-value pair in a list of key-value pair of Tracestate. |
| type Entry struct { |
| // Key is an opaque string up to 256 characters printable. It MUST begin with a lowercase letter, |
| // and can only contain lowercase letters a-z, digits 0-9, underscores _, dashes -, asterisks *, and |
| // forward slashes /. |
| Key string |
| |
| // Value is an opaque string up to 256 characters printable ASCII RFC0020 characters (i.e., the |
| // range 0x20 to 0x7E) except comma , and =. |
| Value string |
| } |
| |
| // Entries returns a slice of Entry. |
| func (ts *Tracestate) Entries() []Entry { |
| if ts == nil { |
| return nil |
| } |
| return ts.entries |
| } |
| |
| func (ts *Tracestate) remove(key string) *Entry { |
| for index, entry := range ts.entries { |
| if entry.Key == key { |
| ts.entries = append(ts.entries[:index], ts.entries[index+1:]...) |
| return &entry |
| } |
| } |
| return nil |
| } |
| |
| func (ts *Tracestate) add(entries []Entry) error { |
| for _, entry := range entries { |
| ts.remove(entry.Key) |
| } |
| if len(ts.entries)+len(entries) > maxKeyValuePairs { |
| return fmt.Errorf("adding %d key-value pairs to current %d pairs exceeds the limit of %d", |
| len(entries), len(ts.entries), maxKeyValuePairs) |
| } |
| ts.entries = append(entries, ts.entries...) |
| return nil |
| } |
| |
| func isValid(entry Entry) bool { |
| return keyValidationRegExp.MatchString(entry.Key) && |
| valueValidationRegExp.MatchString(entry.Value) |
| } |
| |
| func containsDuplicateKey(entries ...Entry) (string, bool) { |
| keyMap := make(map[string]int) |
| for _, entry := range entries { |
| if _, ok := keyMap[entry.Key]; ok { |
| return entry.Key, true |
| } |
| keyMap[entry.Key] = 1 |
| } |
| return "", false |
| } |
| |
| func areEntriesValid(entries ...Entry) (*Entry, bool) { |
| for _, entry := range entries { |
| if !isValid(entry) { |
| return &entry, false |
| } |
| } |
| return nil, true |
| } |
| |
| // New creates a Tracestate object from a parent and/or entries (key-value pair). |
| // Entries from the parent are copied if present. The entries passed to this function |
| // are inserted in front of those copied from the parent. If an entry copied from the |
| // parent contains the same key as one of the entry in entries then the entry copied |
| // from the parent is removed. See add func. |
| // |
| // An error is returned with nil Tracestate if |
| // 1. one or more entry in entries is invalid. |
| // 2. two or more entries in the input entries have the same key. |
| // 3. the number of entries combined from the parent and the input entries exceeds maxKeyValuePairs. |
| // (duplicate entry is counted only once). |
| func New(parent *Tracestate, entries ...Entry) (*Tracestate, error) { |
| if parent == nil && len(entries) == 0 { |
| return nil, nil |
| } |
| if entry, ok := areEntriesValid(entries...); !ok { |
| return nil, fmt.Errorf("key-value pair {%s, %s} is invalid", entry.Key, entry.Value) |
| } |
| |
| if key, duplicate := containsDuplicateKey(entries...); duplicate { |
| return nil, fmt.Errorf("contains duplicate keys (%s)", key) |
| } |
| |
| tracestate := Tracestate{} |
| |
| if parent != nil && len(parent.entries) > 0 { |
| tracestate.entries = append([]Entry{}, parent.entries...) |
| } |
| |
| err := tracestate.add(entries) |
| if err != nil { |
| return nil, err |
| } |
| return &tracestate, nil |
| } |