mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-05 10:02:47 +00:00
331 lines
8.9 KiB
Go
331 lines
8.9 KiB
Go
// Copyright The OpenTelemetry Authors
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// SPDX-License-Identifier: Apache-2.0
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package trace // import "go.opentelemetry.io/otel/trace"
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import (
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"encoding/json"
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"fmt"
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"strings"
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)
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const (
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maxListMembers = 32
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listDelimiters = ","
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memberDelimiter = "="
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errInvalidKey errorConst = "invalid tracestate key"
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errInvalidValue errorConst = "invalid tracestate value"
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errInvalidMember errorConst = "invalid tracestate list-member"
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errMemberNumber errorConst = "too many list-members in tracestate"
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errDuplicate errorConst = "duplicate list-member in tracestate"
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)
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type member struct {
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Key string
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Value string
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}
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// according to (chr = %x20 / (nblk-char = %x21-2B / %x2D-3C / %x3E-7E) )
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// means (chr = %x20-2B / %x2D-3C / %x3E-7E) .
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func checkValueChar(v byte) bool {
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return v >= '\x20' && v <= '\x7e' && v != '\x2c' && v != '\x3d'
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}
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// according to (nblk-chr = %x21-2B / %x2D-3C / %x3E-7E) .
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func checkValueLast(v byte) bool {
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return v >= '\x21' && v <= '\x7e' && v != '\x2c' && v != '\x3d'
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}
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// based on the W3C Trace Context specification
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//
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// value = (0*255(chr)) nblk-chr
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// nblk-chr = %x21-2B / %x2D-3C / %x3E-7E
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// chr = %x20 / nblk-chr
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//
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// see https://www.w3.org/TR/trace-context-1/#value
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func checkValue(val string) bool {
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n := len(val)
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if n == 0 || n > 256 {
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return false
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}
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for i := 0; i < n-1; i++ {
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if !checkValueChar(val[i]) {
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return false
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}
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}
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return checkValueLast(val[n-1])
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}
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func checkKeyRemain(key string) bool {
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// ( lcalpha / DIGIT / "_" / "-"/ "*" / "/" )
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for _, v := range key {
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if isAlphaNum(byte(v)) {
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continue
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}
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switch v {
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case '_', '-', '*', '/':
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continue
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}
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return false
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}
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return true
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}
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// according to
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//
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// simple-key = lcalpha (0*255( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
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// system-id = lcalpha (0*13( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
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//
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// param n is remain part length, should be 255 in simple-key or 13 in system-id.
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func checkKeyPart(key string, n int) bool {
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if len(key) == 0 {
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return false
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}
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first := key[0] // key's first char
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ret := len(key[1:]) <= n
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ret = ret && first >= 'a' && first <= 'z'
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return ret && checkKeyRemain(key[1:])
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}
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func isAlphaNum(c byte) bool {
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if c >= 'a' && c <= 'z' {
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return true
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}
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return c >= '0' && c <= '9'
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}
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// according to
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//
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// tenant-id = ( lcalpha / DIGIT ) 0*240( lcalpha / DIGIT / "_" / "-"/ "*" / "/" )
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//
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// param n is remain part length, should be 240 exactly.
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func checkKeyTenant(key string, n int) bool {
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if len(key) == 0 {
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return false
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}
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return isAlphaNum(key[0]) && len(key[1:]) <= n && checkKeyRemain(key[1:])
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}
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// based on the W3C Trace Context specification
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//
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// key = simple-key / multi-tenant-key
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// simple-key = lcalpha (0*255( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
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// multi-tenant-key = tenant-id "@" system-id
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// tenant-id = ( lcalpha / DIGIT ) (0*240( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
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// system-id = lcalpha (0*13( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
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// lcalpha = %x61-7A ; a-z
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//
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// see https://www.w3.org/TR/trace-context-1/#tracestate-header.
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func checkKey(key string) bool {
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tenant, system, ok := strings.Cut(key, "@")
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if !ok {
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return checkKeyPart(key, 255)
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}
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return checkKeyTenant(tenant, 240) && checkKeyPart(system, 13)
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}
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func newMember(key, value string) (member, error) {
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if !checkKey(key) {
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return member{}, errInvalidKey
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}
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if !checkValue(value) {
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return member{}, errInvalidValue
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}
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return member{Key: key, Value: value}, nil
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}
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func parseMember(m string) (member, error) {
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key, val, ok := strings.Cut(m, memberDelimiter)
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if !ok {
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return member{}, fmt.Errorf("%w: %s", errInvalidMember, m)
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}
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key = strings.TrimLeft(key, " \t")
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val = strings.TrimRight(val, " \t")
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result, e := newMember(key, val)
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if e != nil {
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return member{}, fmt.Errorf("%w: %s", errInvalidMember, m)
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}
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return result, nil
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}
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// String encodes member into a string compliant with the W3C Trace Context
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// specification.
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func (m member) String() string {
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return m.Key + "=" + m.Value
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}
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// TraceState provides additional vendor-specific trace identification
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// information across different distributed tracing systems. It represents an
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// immutable list consisting of key/value pairs, each pair is referred to as a
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// list-member.
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//
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// TraceState conforms to the W3C Trace Context specification
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// (https://www.w3.org/TR/trace-context-1). All operations that create or copy
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// a TraceState do so by validating all input and will only produce TraceState
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// that conform to the specification. Specifically, this means that all
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// list-member's key/value pairs are valid, no duplicate list-members exist,
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// and the maximum number of list-members (32) is not exceeded.
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type TraceState struct { //nolint:revive // revive complains about stutter of `trace.TraceState`
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// list is the members in order.
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list []member
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}
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var _ json.Marshaler = TraceState{}
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// ParseTraceState attempts to decode a TraceState from the passed
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// string. It returns an error if the input is invalid according to the W3C
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// Trace Context specification.
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func ParseTraceState(ts string) (TraceState, error) {
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if ts == "" {
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return TraceState{}, nil
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}
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wrapErr := func(err error) error {
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return fmt.Errorf("failed to parse tracestate: %w", err)
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}
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var members []member
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found := make(map[string]struct{})
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for ts != "" {
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var memberStr string
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memberStr, ts, _ = strings.Cut(ts, listDelimiters)
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if len(memberStr) == 0 {
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continue
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}
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m, err := parseMember(memberStr)
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if err != nil {
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return TraceState{}, wrapErr(err)
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}
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if _, ok := found[m.Key]; ok {
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return TraceState{}, wrapErr(errDuplicate)
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}
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found[m.Key] = struct{}{}
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members = append(members, m)
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if n := len(members); n > maxListMembers {
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return TraceState{}, wrapErr(errMemberNumber)
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}
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}
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return TraceState{list: members}, nil
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}
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// MarshalJSON marshals the TraceState into JSON.
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func (ts TraceState) MarshalJSON() ([]byte, error) {
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return json.Marshal(ts.String())
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}
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// String encodes the TraceState into a string compliant with the W3C
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// Trace Context specification. The returned string will be invalid if the
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// TraceState contains any invalid members.
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func (ts TraceState) String() string {
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if len(ts.list) == 0 {
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return ""
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}
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var n int
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n += len(ts.list) // member delimiters: '='
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n += len(ts.list) - 1 // list delimiters: ','
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for _, mem := range ts.list {
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n += len(mem.Key)
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n += len(mem.Value)
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}
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var sb strings.Builder
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sb.Grow(n)
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_, _ = sb.WriteString(ts.list[0].Key)
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_ = sb.WriteByte('=')
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_, _ = sb.WriteString(ts.list[0].Value)
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for i := 1; i < len(ts.list); i++ {
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_ = sb.WriteByte(listDelimiters[0])
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_, _ = sb.WriteString(ts.list[i].Key)
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_ = sb.WriteByte('=')
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_, _ = sb.WriteString(ts.list[i].Value)
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}
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return sb.String()
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}
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// Get returns the value paired with key from the corresponding TraceState
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// list-member if it exists, otherwise an empty string is returned.
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func (ts TraceState) Get(key string) string {
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for _, member := range ts.list {
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if member.Key == key {
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return member.Value
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}
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}
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return ""
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}
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// Walk walks all key value pairs in the TraceState by calling f
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// Iteration stops if f returns false.
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func (ts TraceState) Walk(f func(key, value string) bool) {
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for _, m := range ts.list {
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if !f(m.Key, m.Value) {
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break
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}
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}
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}
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// Insert adds a new list-member defined by the key/value pair to the
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// TraceState. If a list-member already exists for the given key, that
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// list-member's value is updated. The new or updated list-member is always
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// moved to the beginning of the TraceState as specified by the W3C Trace
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// Context specification.
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//
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// If key or value are invalid according to the W3C Trace Context
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// specification an error is returned with the original TraceState.
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//
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// If adding a new list-member means the TraceState would have more members
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// then is allowed, the new list-member will be inserted and the right-most
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// list-member will be dropped in the returned TraceState.
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func (ts TraceState) Insert(key, value string) (TraceState, error) {
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m, err := newMember(key, value)
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if err != nil {
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return ts, err
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}
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n := len(ts.list)
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found := n
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for i := range ts.list {
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if ts.list[i].Key == key {
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found = i
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}
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}
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cTS := TraceState{}
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if found == n && n < maxListMembers {
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cTS.list = make([]member, n+1)
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} else {
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cTS.list = make([]member, n)
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}
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cTS.list[0] = m
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// When the number of members exceeds capacity, drop the "right-most".
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copy(cTS.list[1:], ts.list[0:found])
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if found < n {
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copy(cTS.list[1+found:], ts.list[found+1:])
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}
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return cTS, nil
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}
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// Delete returns a copy of the TraceState with the list-member identified by
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// key removed.
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func (ts TraceState) Delete(key string) TraceState {
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members := make([]member, ts.Len())
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copy(members, ts.list)
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for i, member := range ts.list {
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if member.Key == key {
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members = append(members[:i], members[i+1:]...)
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// TraceState should contain no duplicate members.
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break
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}
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}
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return TraceState{list: members}
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}
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// Len returns the number of list-members in the TraceState.
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func (ts TraceState) Len() int {
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return len(ts.list)
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}
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