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/event"
    12  	"internal/trace/event/go122"
    13  )
    14  
    15  // Version represents the version of a trace file.
    16  type Version uint32
    17  
    18  const (
    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  
    27  var 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.
    42  func (v Version) Specs() []event.Spec {
    43  	return versions[v]
    44  }
    45  
    46  func (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.
    52  const 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.
    56  func 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.
    69  func WriteHeader(w io.Writer, v Version) (int, error) {
    70  	return fmt.Fprintf(w, headerFmt, v)
    71  }
    72
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