1// Copyright 2023 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package version
6
7import (
8	"fmt"
9	"io"
10
11	"internal/trace/event"
12	"internal/trace/event/go122"
13)
14
15// Version represents the version of a trace file.
16type Version uint32
17
18const (
19	Go111   Version = 11
20	Go119   Version = 19
21	Go121   Version = 21
22	Go122   Version = 22
23	Go123   Version = 23
24	Current         = Go123
25)
26
27var versions = map[Version][]event.Spec{
28	// Go 1.11–1.21 use a different parser and are only set here for the sake of
29	// Version.Valid.
30	Go111: nil,
31	Go119: nil,
32	Go121: nil,
33
34	Go122: go122.Specs(),
35	// Go 1.23 adds backwards-incompatible events, but
36	// traces produced by Go 1.22 are also always valid
37	// Go 1.23 traces.
38	Go123: go122.Specs(),
39}
40
41// Specs returns the set of event.Specs for this version.
42func (v Version) Specs() []event.Spec {
43	return versions[v]
44}
45
46func (v Version) Valid() bool {
47	_, ok := versions[v]
48	return ok
49}
50
51// headerFmt is the format of the header of all Go execution traces.
52const headerFmt = "go 1.%d trace\x00\x00\x00"
53
54// ReadHeader reads the version of the trace out of the trace file's
55// header, whose prefix must be present in v.
56func ReadHeader(r io.Reader) (Version, error) {
57	var v Version
58	_, err := fmt.Fscanf(r, headerFmt, &v)
59	if err != nil {
60		return v, fmt.Errorf("bad file format: not a Go execution trace?")
61	}
62	if !v.Valid() {
63		return v, fmt.Errorf("unknown or unsupported trace version go 1.%d", v)
64	}
65	return v, nil
66}
67
68// WriteHeader writes a header for a trace version v to w.
69func WriteHeader(w io.Writer, v Version) (int, error) {
70	return fmt.Fprintf(w, headerFmt, v)
71}
72