44package trace // import "go.opentelemetry.io/otel/trace"
55
66import (
7- "bytes"
8- "encoding/hex"
97 "encoding/json"
108)
119
@@ -41,18 +39,44 @@ var (
4139// IsValid checks whether the trace TraceID is valid. A valid trace ID does
4240// not consist of zeros only.
4341func (t TraceID ) IsValid () bool {
44- return ! bytes . Equal ( t [:], nilTraceID [:])
42+ return t != nilTraceID
4543}
4644
4745// MarshalJSON implements a custom marshal function to encode TraceID
4846// as a hex string.
4947func (t TraceID ) MarshalJSON () ([]byte , error ) {
50- return json .Marshal (t .String ())
48+ b := [32 + 2 ]byte {0 : '"' , 33 : '"' }
49+ h := t .hexBytes ()
50+ copy (b [1 :], h [:])
51+ return b [:], nil
5152}
5253
5354// String returns the hex string representation form of a TraceID.
5455func (t TraceID ) String () string {
55- return hex .EncodeToString (t [:])
56+ h := t .hexBytes ()
57+ return string (h [:])
58+ }
59+
60+ // hexBytes returns the hex string representation form of a TraceID.
61+ func (t TraceID ) hexBytes () [32 ]byte {
62+ return [32 ]byte {
63+ hexLU [t [0x0 ]>> 4 ], hexLU [t [0x0 ]& 0xf ],
64+ hexLU [t [0x1 ]>> 4 ], hexLU [t [0x1 ]& 0xf ],
65+ hexLU [t [0x2 ]>> 4 ], hexLU [t [0x2 ]& 0xf ],
66+ hexLU [t [0x3 ]>> 4 ], hexLU [t [0x3 ]& 0xf ],
67+ hexLU [t [0x4 ]>> 4 ], hexLU [t [0x4 ]& 0xf ],
68+ hexLU [t [0x5 ]>> 4 ], hexLU [t [0x5 ]& 0xf ],
69+ hexLU [t [0x6 ]>> 4 ], hexLU [t [0x6 ]& 0xf ],
70+ hexLU [t [0x7 ]>> 4 ], hexLU [t [0x7 ]& 0xf ],
71+ hexLU [t [0x8 ]>> 4 ], hexLU [t [0x8 ]& 0xf ],
72+ hexLU [t [0x9 ]>> 4 ], hexLU [t [0x9 ]& 0xf ],
73+ hexLU [t [0xa ]>> 4 ], hexLU [t [0xa ]& 0xf ],
74+ hexLU [t [0xb ]>> 4 ], hexLU [t [0xb ]& 0xf ],
75+ hexLU [t [0xc ]>> 4 ], hexLU [t [0xc ]& 0xf ],
76+ hexLU [t [0xd ]>> 4 ], hexLU [t [0xd ]& 0xf ],
77+ hexLU [t [0xe ]>> 4 ], hexLU [t [0xe ]& 0xf ],
78+ hexLU [t [0xf ]>> 4 ], hexLU [t [0xf ]& 0xf ],
79+ }
5680}
5781
5882// SpanID is a unique identity of a span in a trace.
@@ -66,78 +90,88 @@ var (
6690// IsValid checks whether the SpanID is valid. A valid SpanID does not consist
6791// of zeros only.
6892func (s SpanID ) IsValid () bool {
69- return ! bytes . Equal ( s [:], nilSpanID [:])
93+ return s != nilSpanID
7094}
7195
7296// MarshalJSON implements a custom marshal function to encode SpanID
7397// as a hex string.
7498func (s SpanID ) MarshalJSON () ([]byte , error ) {
75- return json .Marshal (s .String ())
99+ b := [16 + 2 ]byte {0 : '"' , 17 : '"' }
100+ h := s .hexBytes ()
101+ copy (b [1 :], h [:])
102+ return b [:], nil
76103}
77104
78105// String returns the hex string representation form of a SpanID.
79106func (s SpanID ) String () string {
80- return hex .EncodeToString (s [:])
107+ b := s .hexBytes ()
108+ return string (b [:])
109+ }
110+
111+ func (s SpanID ) hexBytes () [16 ]byte {
112+ return [16 ]byte {
113+ hexLU [s [0 ]>> 4 ], hexLU [s [0 ]& 0xf ],
114+ hexLU [s [1 ]>> 4 ], hexLU [s [1 ]& 0xf ],
115+ hexLU [s [2 ]>> 4 ], hexLU [s [2 ]& 0xf ],
116+ hexLU [s [3 ]>> 4 ], hexLU [s [3 ]& 0xf ],
117+ hexLU [s [4 ]>> 4 ], hexLU [s [4 ]& 0xf ],
118+ hexLU [s [5 ]>> 4 ], hexLU [s [5 ]& 0xf ],
119+ hexLU [s [6 ]>> 4 ], hexLU [s [6 ]& 0xf ],
120+ hexLU [s [7 ]>> 4 ], hexLU [s [7 ]& 0xf ],
121+ }
81122}
82123
83124// TraceIDFromHex returns a TraceID from a hex string if it is compliant with
84125// the W3C trace-context specification. See more at
85126// https://www.w3.org/TR/trace-context/#trace-id
86127// nolint:revive // revive complains about stutter of `trace.TraceIDFromHex`.
87128func TraceIDFromHex (h string ) (TraceID , error ) {
88- t := TraceID {}
89129 if len (h ) != 32 {
90- return t , errInvalidTraceIDLength
130+ return [ 16 ] byte {} , errInvalidTraceIDLength
91131 }
92-
93- if err := decodeHex (h , t [:]); err != nil {
94- return t , err
132+ var b [16 ]byte
133+ invalidMark := byte (0 )
134+ for i := 0 ; i < len (h ); i += 4 {
135+ b [i / 2 ] = (hexRev [h [i ]] << 4 ) | hexRev [h [i + 1 ]]
136+ b [i / 2 + 1 ] = (hexRev [h [i + 2 ]] << 4 ) | hexRev [h [i + 3 ]]
137+ invalidMark |= hexRev [h [i ]] | hexRev [h [i + 1 ]] | hexRev [h [i + 2 ]] | hexRev [h [i + 3 ]]
95138 }
96-
97- if ! t .IsValid () {
98- return t , errNilTraceID
139+ // If the upper 4 bits of any byte are not zero, there was an invalid hex
140+ // character since invalid hex characters are 0xff in hexLU.
141+ if invalidMark & 0xf0 != 0 {
142+ return [16 ]byte {}, errInvalidHexID
143+ }
144+ // If we didn't set any bits, then h was all zeros.
145+ if invalidMark == 0 {
146+ return [16 ]byte {}, errNilTraceID
99147 }
100- return t , nil
148+ return b , nil
101149}
102150
103151// SpanIDFromHex returns a SpanID from a hex string if it is compliant
104152// with the w3c trace-context specification.
105153// See more at https://www.w3.org/TR/trace-context/#parent-id
106154func SpanIDFromHex (h string ) (SpanID , error ) {
107- s := SpanID {}
108155 if len (h ) != 16 {
109- return s , errInvalidSpanIDLength
110- }
111-
112- if err := decodeHex (h , s [:]); err != nil {
113- return s , err
156+ return [8 ]byte {}, errInvalidSpanIDLength
114157 }
115-
116- if ! s .IsValid () {
117- return s , errNilSpanID
158+ var b [8 ]byte
159+ invalidMark := byte (0 )
160+ for i := 0 ; i < len (h ); i += 4 {
161+ b [i / 2 ] = (hexRev [h [i ]] << 4 ) | hexRev [h [i + 1 ]]
162+ b [i / 2 + 1 ] = (hexRev [h [i + 2 ]] << 4 ) | hexRev [h [i + 3 ]]
163+ invalidMark |= hexRev [h [i ]] | hexRev [h [i + 1 ]] | hexRev [h [i + 2 ]] | hexRev [h [i + 3 ]]
118164 }
119- return s , nil
120- }
121-
122- func decodeHex (h string , b []byte ) error {
123- for _ , r := range h {
124- switch {
125- case 'a' <= r && r <= 'f' :
126- continue
127- case '0' <= r && r <= '9' :
128- continue
129- default :
130- return errInvalidHexID
131- }
165+ // If the upper 4 bits of any byte are not zero, there was an invalid hex
166+ // character since invalid hex characters are 0xff in hexLU.
167+ if invalidMark & 0xf0 != 0 {
168+ return [8 ]byte {}, errInvalidHexID
132169 }
133-
134- decoded , err := hex .DecodeString (h )
135- if err != nil {
136- return err
170+ // If we didn't set any bits, then h was all zeros.
171+ if invalidMark == 0 {
172+ return [8 ]byte {}, errNilSpanID
137173 }
138-
139- copy (b , decoded )
140- return nil
174+ return b , nil
141175}
142176
143177// TraceFlags contains flags that can be set on a SpanContext.
@@ -160,12 +194,20 @@ func (tf TraceFlags) WithSampled(sampled bool) TraceFlags { // nolint:revive //
160194// MarshalJSON implements a custom marshal function to encode TraceFlags
161195// as a hex string.
162196func (tf TraceFlags ) MarshalJSON () ([]byte , error ) {
163- return json .Marshal (tf .String ())
197+ b := [2 + 2 ]byte {0 : '"' , 3 : '"' }
198+ h := tf .hexBytes ()
199+ copy (b [1 :], h [:])
200+ return b [:], nil
164201}
165202
166203// String returns the hex string representation form of TraceFlags.
167204func (tf TraceFlags ) String () string {
168- return hex .EncodeToString ([]byte {byte (tf )}[:])
205+ h := tf .hexBytes ()
206+ return string (h [:])
207+ }
208+
209+ func (tf TraceFlags ) hexBytes () [2 ]byte {
210+ return [2 ]byte {hexLU [tf >> 4 ], hexLU [tf & 0xf ]}
169211}
170212
171213// SpanContextConfig contains mutable fields usable for constructing
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