version.go

     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  
     5  package version
     6  
     7  import (
     8  	"fmt"
     9  	"io"
    10  
    11  	"internal/trace/tracev2"
    12  )
    13  
    14  // Version represents the version of a trace file.
    15  type Version uint32
    16  
    17  const (
    18  	Go111   Version = 11 // v1
    19  	Go119   Version = 19 // v1
    20  	Go121   Version = 21 // v1
    21  	Go122   Version = 22 // v2
    22  	Go123   Version = 23 // v2
    23  	Go125   Version = 25 // v2
    24  	Go126   Version = 26 // v2
    25  	Current         = Go126
    26  )
    27  
    28  var versions = map[Version][]tracev2.EventSpec{
    29  	// Go 1.11–1.21 use a different parser and are only set here for the sake of
    30  	// Version.Valid.
    31  	Go111: nil,
    32  	Go119: nil,
    33  	Go121: nil,
    34  
    35  	Go122: tracev2.Specs()[:tracev2.EvUserLog+1],           // All events after are Go 1.23+.
    36  	Go123: tracev2.Specs()[:tracev2.EvExperimentalBatch+1], // All events after are Go 1.25+.
    37  	Go125: tracev2.Specs()[:tracev2.EvClockSnapshot+1],     // All events after are Go 1.26+.
    38  	Go126: tracev2.Specs(),
    39  }
    40  
    41  // Specs returns the set of event.Specs for this version.
    42  func (v Version) Specs() []tracev2.EventSpec {
    43  	return versions[v]
    44  }
    45  
    46  // EventName returns a string name of a wire format event
    47  // for a particular trace version.
    48  func (v Version) EventName(typ tracev2.EventType) string {
    49  	if !v.Valid() {
    50  		return "<invalid trace version>"
    51  	}
    52  	s := v.Specs()
    53  	if len(s) == 0 {
    54  		return "<v1 trace event type>"
    55  	}
    56  	if int(typ) < len(s) && s[typ].Name != "" {
    57  		return s[typ].Name
    58  	}
    59  	return fmt.Sprintf("Invalid(%d)", typ)
    60  }
    61  
    62  func (v Version) Valid() bool {
    63  	_, ok := versions[v]
    64  	return ok
    65  }
    66  
    67  // headerFmt is the format of the header of all Go execution traces.
    68  const headerFmt = "go 1.%d trace\x00\x00\x00"
    69  
    70  // ReadHeader reads the version of the trace out of the trace file's
    71  // header, whose prefix must be present in v.
    72  func ReadHeader(r io.Reader) (Version, error) {
    73  	var v Version
    74  	_, err := fmt.Fscanf(r, headerFmt, &v)
    75  	if err != nil {
    76  		return v, fmt.Errorf("bad file format: not a Go execution trace?")
    77  	}
    78  	if !v.Valid() {
    79  		return v, fmt.Errorf("unknown or unsupported trace version go 1.%d", v)
    80  	}
    81  	return v, nil
    82  }
    83  
    84  // WriteHeader writes a header for a trace version v to w.
    85  func WriteHeader(w io.Writer, v Version) (int, error) {
    86  	return fmt.Fprintf(w, headerFmt, v)
    87  }
    88
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