buildid.go

Documentation: cmd/buildid

     1  // Copyright 2017 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 main
     6  
     7  import (
     8  	"flag"
     9  	"fmt"
    10  	"log"
    11  	"os"
    12  	"strings"
    13  
    14  	"cmd/internal/buildid"
    15  	"cmd/internal/telemetry/counter"
    16  )
    17  
    18  func usage() {
    19  	fmt.Fprintf(os.Stderr, "usage: go tool buildid [-w] file\n")
    20  	flag.PrintDefaults()
    21  	os.Exit(2)
    22  }
    23  
    24  var wflag = flag.Bool("w", false, "write build ID")
    25  
    26  func main() {
    27  	log.SetPrefix("buildid: ")
    28  	log.SetFlags(0)
    29  	counter.Open()
    30  	flag.Usage = usage
    31  	flag.Parse()
    32  	counter.Inc("buildid/invocations")
    33  	counter.CountFlags("buildid/flag:", *flag.CommandLine)
    34  	if flag.NArg() != 1 {
    35  		usage()
    36  	}
    37  
    38  	file := flag.Arg(0)
    39  	id, err := buildid.ReadFile(file)
    40  	if err != nil {
    41  		log.Fatal(err)
    42  	}
    43  	if !*wflag {
    44  		fmt.Printf("%s\n", id)
    45  		return
    46  	}
    47  
    48  	// Keep in sync with src/cmd/go/internal/work/buildid.go:updateBuildID
    49  
    50  	f, err := os.Open(file)
    51  	if err != nil {
    52  		log.Fatal(err)
    53  	}
    54  	matches, hash, err := buildid.FindAndHash(f, id, 0)
    55  	f.Close()
    56  	if err != nil {
    57  		log.Fatal(err)
    58  	}
    59  
    60  	// <= go 1.7 doesn't embed the contentID or actionID, so no slash is present
    61  	if !strings.Contains(id, "/") {
    62  		log.Fatalf("%s: build ID is a legacy format...binary too old for this tool", file)
    63  	}
    64  
    65  	newID := id[:strings.LastIndex(id, "/")] + "/" + buildid.HashToString(hash)
    66  	if len(newID) != len(id) {
    67  		log.Fatalf("%s: build ID length mismatch %q vs %q", file, id, newID)
    68  	}
    69  
    70  	if len(matches) == 0 {
    71  		return
    72  	}
    73  
    74  	f, err = os.OpenFile(file, os.O_RDWR, 0)
    75  	if err != nil {
    76  		log.Fatal(err)
    77  	}
    78  	if err := buildid.Rewrite(f, matches, newID); err != nil {
    79  		log.Fatal(err)
    80  	}
    81  	if err := f.Close(); err != nil {
    82  		log.Fatal(err)
    83  	}
    84  }
    85
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