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
new file mode 100644
index 0000000..2d6c713
--- /dev/null
+++ b/vendor/go.opencensus.io/trace/tracestate/tracestate.go
@@ -0,0 +1,147 @@
+// 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
+}