pack.go

     1  // Copyright 2014 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  	"cmd/internal/archive"
     9  	"cmd/internal/objabi"
    10  	"cmd/internal/telemetry/counter"
    11  	"fmt"
    12  	"io"
    13  	"io/fs"
    14  	"log"
    15  	"os"
    16  	"path/filepath"
    17  )
    18  
    19  const usageMessage = `Usage: pack op file.a [name....]
    20  Where op is one of cprtx optionally followed by v for verbose output.
    21  For compatibility with old Go build environments the op string grc is
    22  accepted as a synonym for c.
    23  
    24  For more information, run
    25  	go doc cmd/pack`
    26  
    27  func usage() {
    28  	fmt.Fprintln(os.Stderr, usageMessage)
    29  	os.Exit(2)
    30  }
    31  
    32  func main() {
    33  	log.SetFlags(0)
    34  	log.SetPrefix("pack: ")
    35  	counter.Open()
    36  	objabi.Flagparse(usage)
    37  	// need "pack op archive" at least.
    38  	if len(os.Args) < 3 {
    39  		log.Print("not enough arguments")
    40  		fmt.Fprintln(os.Stderr)
    41  		usage()
    42  	}
    43  	setOp(os.Args[1])
    44  	counter.Inc("pack/invocations")
    45  	counter.Inc("pack/op:" + string(op))
    46  	var ar *Archive
    47  	switch op {
    48  	case 'p':
    49  		ar = openArchive(os.Args[2], os.O_RDONLY, os.Args[3:])
    50  		ar.scan(ar.printContents)
    51  	case 'r':
    52  		ar = openArchive(os.Args[2], os.O_RDWR|os.O_CREATE, os.Args[3:])
    53  		ar.addFiles()
    54  	case 'c':
    55  		ar = openArchive(os.Args[2], os.O_RDWR|os.O_TRUNC|os.O_CREATE, os.Args[3:])
    56  		ar.addPkgdef()
    57  		ar.addFiles()
    58  	case 't':
    59  		ar = openArchive(os.Args[2], os.O_RDONLY, os.Args[3:])
    60  		ar.scan(ar.tableOfContents)
    61  	case 'x':
    62  		ar = openArchive(os.Args[2], os.O_RDONLY, os.Args[3:])
    63  		ar.scan(ar.extractContents)
    64  	default:
    65  		log.Printf("invalid operation %q", os.Args[1])
    66  		fmt.Fprintln(os.Stderr)
    67  		usage()
    68  	}
    69  	if len(ar.files) > 0 {
    70  		log.Fatalf("file %q not in archive", ar.files[0])
    71  	}
    72  }
    73  
    74  // The unusual ancestry means the arguments are not Go-standard.
    75  // These variables hold the decoded operation specified by the first argument.
    76  // op holds the operation we are doing (prtx).
    77  // verbose tells whether the 'v' option was specified.
    78  var (
    79  	op      rune
    80  	verbose bool
    81  )
    82  
    83  // setOp parses the operation string (first argument).
    84  func setOp(arg string) {
    85  	// Recognize 'go tool pack grc' because that was the
    86  	// formerly canonical way to build a new archive
    87  	// from a set of input files. Accepting it keeps old
    88  	// build systems working with both Go 1.2 and Go 1.3.
    89  	if arg == "grc" {
    90  		arg = "c"
    91  	}
    92  
    93  	for _, r := range arg {
    94  		switch r {
    95  		case 'c', 'p', 'r', 't', 'x':
    96  			if op != 0 {
    97  				// At most one can be set.
    98  				usage()
    99  			}
   100  			op = r
   101  		case 'v':
   102  			if verbose {
   103  				// Can be set only once.
   104  				usage()
   105  			}
   106  			verbose = true
   107  		default:
   108  			usage()
   109  		}
   110  	}
   111  }
   112  
   113  const (
   114  	arHeader = "!<arch>\n"
   115  )
   116  
   117  // An Archive represents an open archive file. It is always scanned sequentially
   118  // from start to end, without backing up.
   119  type Archive struct {
   120  	a        *archive.Archive
   121  	files    []string // Explicit list of files to be processed.
   122  	pad      int      // Padding bytes required at end of current archive file
   123  	matchAll bool     // match all files in archive
   124  }
   125  
   126  // archive opens (and if necessary creates) the named archive.
   127  func openArchive(name string, mode int, files []string) *Archive {
   128  	f, err := os.OpenFile(name, mode, 0666)
   129  	if err != nil {
   130  		log.Fatal(err)
   131  	}
   132  	var a *archive.Archive
   133  	if mode&os.O_TRUNC != 0 { // the c command
   134  		a, err = archive.New(f)
   135  	} else {
   136  		a, err = archive.Parse(f, verbose)
   137  		if err != nil && mode&os.O_CREATE != 0 { // the r command
   138  			a, err = archive.New(f)
   139  		}
   140  	}
   141  	if err != nil {
   142  		log.Fatal(err)
   143  	}
   144  	return &Archive{
   145  		a:        a,
   146  		files:    files,
   147  		matchAll: len(files) == 0,
   148  	}
   149  }
   150  
   151  // scan scans the archive and executes the specified action on each entry.
   152  func (ar *Archive) scan(action func(*archive.Entry)) {
   153  	for i := range ar.a.Entries {
   154  		e := &ar.a.Entries[i]
   155  		action(e)
   156  	}
   157  }
   158  
   159  // listEntry prints to standard output a line describing the entry.
   160  func listEntry(e *archive.Entry, verbose bool) {
   161  	if verbose {
   162  		fmt.Fprintf(stdout, "%s\n", e.String())
   163  	} else {
   164  		fmt.Fprintf(stdout, "%s\n", e.Name)
   165  	}
   166  }
   167  
   168  // output copies the entry to the specified writer.
   169  func (ar *Archive) output(e *archive.Entry, w io.Writer) {
   170  	r := io.NewSectionReader(ar.a.File(), e.Offset, e.Size)
   171  	n, err := io.Copy(w, r)
   172  	if err != nil {
   173  		log.Fatal(err)
   174  	}
   175  	if n != e.Size {
   176  		log.Fatal("short file")
   177  	}
   178  }
   179  
   180  // match reports whether the entry matches the argument list.
   181  // If it does, it also drops the file from the to-be-processed list.
   182  func (ar *Archive) match(e *archive.Entry) bool {
   183  	if ar.matchAll {
   184  		return true
   185  	}
   186  	for i, name := range ar.files {
   187  		if e.Name == name {
   188  			copy(ar.files[i:], ar.files[i+1:])
   189  			ar.files = ar.files[:len(ar.files)-1]
   190  			return true
   191  		}
   192  	}
   193  	return false
   194  }
   195  
   196  // addFiles adds files to the archive. The archive is known to be
   197  // sane and we are positioned at the end. No attempt is made
   198  // to check for existing files.
   199  func (ar *Archive) addFiles() {
   200  	if len(ar.files) == 0 {
   201  		usage()
   202  	}
   203  	for _, file := range ar.files {
   204  		if verbose {
   205  			fmt.Printf("%s\n", file)
   206  		}
   207  
   208  		f, err := os.Open(file)
   209  		if err != nil {
   210  			log.Fatal(err)
   211  		}
   212  		aro, err := archive.Parse(f, false)
   213  		if err != nil || !isGoCompilerObjFile(aro) {
   214  			f.Seek(0, io.SeekStart)
   215  			ar.addFile(f)
   216  			goto close
   217  		}
   218  
   219  		for _, e := range aro.Entries {
   220  			if e.Type != archive.EntryGoObj || e.Name != "_go_.o" {
   221  				continue
   222  			}
   223  			ar.a.AddEntry(archive.EntryGoObj, filepath.Base(file), 0, 0, 0, 0644, e.Size, io.NewSectionReader(f, e.Offset, e.Size))
   224  		}
   225  	close:
   226  		f.Close()
   227  	}
   228  	ar.files = nil
   229  }
   230  
   231  // FileLike abstracts the few methods we need, so we can test without needing real files.
   232  type FileLike interface {
   233  	Name() string
   234  	Stat() (fs.FileInfo, error)
   235  	Read([]byte) (int, error)
   236  	Close() error
   237  }
   238  
   239  // addFile adds a single file to the archive
   240  func (ar *Archive) addFile(fd FileLike) {
   241  	// Format the entry.
   242  	// First, get its info.
   243  	info, err := fd.Stat()
   244  	if err != nil {
   245  		log.Fatal(err)
   246  	}
   247  	// mtime, uid, gid are all zero so repeated builds produce identical output.
   248  	mtime := int64(0)
   249  	uid := 0
   250  	gid := 0
   251  	ar.a.AddEntry(archive.EntryNativeObj, info.Name(), mtime, uid, gid, info.Mode(), info.Size(), fd)
   252  }
   253  
   254  // addPkgdef adds the __.PKGDEF file to the archive, copied
   255  // from the first Go object file on the file list, if any.
   256  // The archive is known to be empty.
   257  func (ar *Archive) addPkgdef() {
   258  	done := false
   259  	for _, file := range ar.files {
   260  		f, err := os.Open(file)
   261  		if err != nil {
   262  			log.Fatal(err)
   263  		}
   264  		aro, err := archive.Parse(f, false)
   265  		if err != nil || !isGoCompilerObjFile(aro) {
   266  			goto close
   267  		}
   268  
   269  		for _, e := range aro.Entries {
   270  			if e.Type != archive.EntryPkgDef {
   271  				continue
   272  			}
   273  			if verbose {
   274  				fmt.Printf("__.PKGDEF # %s\n", file)
   275  			}
   276  			ar.a.AddEntry(archive.EntryPkgDef, "__.PKGDEF", 0, 0, 0, 0644, e.Size, io.NewSectionReader(f, e.Offset, e.Size))
   277  			done = true
   278  		}
   279  	close:
   280  		f.Close()
   281  		if done {
   282  			break
   283  		}
   284  	}
   285  }
   286  
   287  // Finally, the actual commands. Each is an action.
   288  
   289  // can be modified for testing.
   290  var stdout io.Writer = os.Stdout
   291  
   292  // printContents implements the 'p' command.
   293  func (ar *Archive) printContents(e *archive.Entry) {
   294  	ar.extractContents1(e, stdout)
   295  }
   296  
   297  // tableOfContents implements the 't' command.
   298  func (ar *Archive) tableOfContents(e *archive.Entry) {
   299  	if ar.match(e) {
   300  		listEntry(e, verbose)
   301  	}
   302  }
   303  
   304  // extractContents implements the 'x' command.
   305  func (ar *Archive) extractContents(e *archive.Entry) {
   306  	ar.extractContents1(e, nil)
   307  }
   308  
   309  func (ar *Archive) extractContents1(e *archive.Entry, out io.Writer) {
   310  	if ar.match(e) {
   311  		if verbose {
   312  			listEntry(e, false)
   313  		}
   314  		if out == nil {
   315  			f, err := os.OpenFile(e.Name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0444 /*e.Mode*/)
   316  			if err != nil {
   317  				log.Fatal(err)
   318  			}
   319  			defer f.Close()
   320  			out = f
   321  		}
   322  		ar.output(e, out)
   323  	}
   324  }
   325  
   326  // isGoCompilerObjFile reports whether file is an object file created
   327  // by the Go compiler, which is an archive file with exactly one entry
   328  // of __.PKGDEF, or _go_.o, or both entries.
   329  func isGoCompilerObjFile(a *archive.Archive) bool {
   330  	switch len(a.Entries) {
   331  	case 1:
   332  		return (a.Entries[0].Type == archive.EntryGoObj && a.Entries[0].Name == "_go_.o") ||
   333  			(a.Entries[0].Type == archive.EntryPkgDef && a.Entries[0].Name == "__.PKGDEF")
   334  	case 2:
   335  		var foundPkgDef, foundGo bool
   336  		for _, e := range a.Entries {
   337  			if e.Type == archive.EntryPkgDef && e.Name == "__.PKGDEF" {
   338  				foundPkgDef = true
   339  			}
   340  			if e.Type == archive.EntryGoObj && e.Name == "_go_.o" {
   341  				foundGo = true
   342  			}
   343  		}
   344  		return foundPkgDef && foundGo
   345  	default:
   346  		return false
   347  	}
   348  }
   349
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