writer.go

Documentation: github.com/klauspost/compress/zip

     1  // Copyright 2011 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 zip
     6  
     7  import (
     8  	"bufio"
     9  	"encoding/binary"
    10  	"errors"
    11  	"hash"
    12  	"hash/crc32"
    13  	"io"
    14  	"strings"
    15  	"unicode/utf8"
    16  )
    17  
    18  var (
    19  	errLongName  = errors.New("zip: FileHeader.Name too long")
    20  	errLongExtra = errors.New("zip: FileHeader.Extra too long")
    21  )
    22  
    23  // Writer implements a zip file writer.
    24  type Writer struct {
    25  	cw          *countWriter
    26  	dir         []*header
    27  	last        *fileWriter
    28  	closed      bool
    29  	compressors map[uint16]Compressor
    30  	comment     string
    31  
    32  	// testHookCloseSizeOffset if non-nil is called with the size
    33  	// of offset of the central directory at Close.
    34  	testHookCloseSizeOffset func(size, offset uint64)
    35  }
    36  
    37  type header struct {
    38  	*FileHeader
    39  	offset uint64
    40  	raw    bool
    41  }
    42  
    43  // NewWriter returns a new Writer writing a zip file to w.
    44  func NewWriter(w io.Writer) *Writer {
    45  	return &Writer{cw: &countWriter{w: bufio.NewWriter(w)}}
    46  }
    47  
    48  // SetOffset sets the offset of the beginning of the zip data within the
    49  // underlying writer. It should be used when the zip data is appended to an
    50  // existing file, such as a binary executable.
    51  // It must be called before any data is written.
    52  func (w *Writer) SetOffset(n int64) {
    53  	if w.cw.count != 0 {
    54  		panic("zip: SetOffset called after data was written")
    55  	}
    56  	w.cw.count = n
    57  }
    58  
    59  // Flush flushes any buffered data to the underlying writer.
    60  // Calling Flush is not normally necessary; calling Close is sufficient.
    61  func (w *Writer) Flush() error {
    62  	return w.cw.w.(*bufio.Writer).Flush()
    63  }
    64  
    65  // SetComment sets the end-of-central-directory comment field.
    66  // It can only be called before Close.
    67  func (w *Writer) SetComment(comment string) error {
    68  	if len(comment) > uint16max {
    69  		return errors.New("zip: Writer.Comment too long")
    70  	}
    71  	w.comment = comment
    72  	return nil
    73  }
    74  
    75  // Close finishes writing the zip file by writing the central directory.
    76  // It does not close the underlying writer.
    77  func (w *Writer) Close() error {
    78  	if w.last != nil && !w.last.closed {
    79  		if err := w.last.close(); err != nil {
    80  			return err
    81  		}
    82  		w.last = nil
    83  	}
    84  	if w.closed {
    85  		return errors.New("zip: writer closed twice")
    86  	}
    87  	w.closed = true
    88  
    89  	// write central directory
    90  	start := w.cw.count
    91  	for _, h := range w.dir {
    92  		var buf [directoryHeaderLen]byte
    93  		b := writeBuf(buf[:])
    94  		b.uint32(uint32(directoryHeaderSignature))
    95  		b.uint16(h.CreatorVersion)
    96  		b.uint16(h.ReaderVersion)
    97  		b.uint16(h.Flags)
    98  		b.uint16(h.Method)
    99  		b.uint16(h.ModifiedTime)
   100  		b.uint16(h.ModifiedDate)
   101  		b.uint32(h.CRC32)
   102  		if h.isZip64() || h.offset >= uint32max {
   103  			// the file needs a zip64 header. store maxint in both
   104  			// 32 bit size fields (and offset later) to signal that the
   105  			// zip64 extra header should be used.
   106  			b.uint32(uint32max) // compressed size
   107  			b.uint32(uint32max) // uncompressed size
   108  
   109  			// append a zip64 extra block to Extra
   110  			var buf [28]byte // 2x uint16 + 3x uint64
   111  			eb := writeBuf(buf[:])
   112  			eb.uint16(zip64ExtraID)
   113  			eb.uint16(24) // size = 3x uint64
   114  			eb.uint64(h.UncompressedSize64)
   115  			eb.uint64(h.CompressedSize64)
   116  			eb.uint64(h.offset)
   117  			h.Extra = append(h.Extra, buf[:]...)
   118  		} else {
   119  			b.uint32(h.CompressedSize)
   120  			b.uint32(h.UncompressedSize)
   121  		}
   122  
   123  		b.uint16(uint16(len(h.Name)))
   124  		b.uint16(uint16(len(h.Extra)))
   125  		b.uint16(uint16(len(h.Comment)))
   126  		b = b[4:] // skip disk number start and internal file attr (2x uint16)
   127  		b.uint32(h.ExternalAttrs)
   128  		if h.isZip64() || h.offset > uint32max {
   129  			b.uint32(uint32max)
   130  		} else {
   131  			b.uint32(uint32(h.offset))
   132  		}
   133  		if _, err := w.cw.Write(buf[:]); err != nil {
   134  			return err
   135  		}
   136  		if _, err := io.WriteString(w.cw, h.Name); err != nil {
   137  			return err
   138  		}
   139  		if _, err := w.cw.Write(h.Extra); err != nil {
   140  			return err
   141  		}
   142  		if _, err := io.WriteString(w.cw, h.Comment); err != nil {
   143  			return err
   144  		}
   145  	}
   146  	end := w.cw.count
   147  
   148  	records := uint64(len(w.dir))
   149  	size := uint64(end - start)
   150  	offset := uint64(start)
   151  
   152  	if f := w.testHookCloseSizeOffset; f != nil {
   153  		f(size, offset)
   154  	}
   155  
   156  	if records >= uint16max || size >= uint32max || offset >= uint32max {
   157  		var buf [directory64EndLen + directory64LocLen]byte
   158  		b := writeBuf(buf[:])
   159  
   160  		// zip64 end of central directory record
   161  		b.uint32(directory64EndSignature)
   162  		b.uint64(directory64EndLen - 12) // length minus signature (uint32) and length fields (uint64)
   163  		b.uint16(zipVersion45)           // version made by
   164  		b.uint16(zipVersion45)           // version needed to extract
   165  		b.uint32(0)                      // number of this disk
   166  		b.uint32(0)                      // number of the disk with the start of the central directory
   167  		b.uint64(records)                // total number of entries in the central directory on this disk
   168  		b.uint64(records)                // total number of entries in the central directory
   169  		b.uint64(size)                   // size of the central directory
   170  		b.uint64(offset)                 // offset of start of central directory with respect to the starting disk number
   171  
   172  		// zip64 end of central directory locator
   173  		b.uint32(directory64LocSignature)
   174  		b.uint32(0)           // number of the disk with the start of the zip64 end of central directory
   175  		b.uint64(uint64(end)) // relative offset of the zip64 end of central directory record
   176  		b.uint32(1)           // total number of disks
   177  
   178  		if _, err := w.cw.Write(buf[:]); err != nil {
   179  			return err
   180  		}
   181  
   182  		// store max values in the regular end record to signal
   183  		// that the zip64 values should be used instead
   184  		records = uint16max
   185  		size = uint32max
   186  		offset = uint32max
   187  	}
   188  
   189  	// write end record
   190  	var buf [directoryEndLen]byte
   191  	b := writeBuf(buf[:])
   192  	b.uint32(uint32(directoryEndSignature))
   193  	b = b[4:]                        // skip over disk number and first disk number (2x uint16)
   194  	b.uint16(uint16(records))        // number of entries this disk
   195  	b.uint16(uint16(records))        // number of entries total
   196  	b.uint32(uint32(size))           // size of directory
   197  	b.uint32(uint32(offset))         // start of directory
   198  	b.uint16(uint16(len(w.comment))) // byte size of EOCD comment
   199  	if _, err := w.cw.Write(buf[:]); err != nil {
   200  		return err
   201  	}
   202  	if _, err := io.WriteString(w.cw, w.comment); err != nil {
   203  		return err
   204  	}
   205  
   206  	return w.cw.w.(*bufio.Writer).Flush()
   207  }
   208  
   209  // Create adds a file to the zip file using the provided name.
   210  // It returns a Writer to which the file contents should be written.
   211  // The file contents will be compressed using the Deflate method.
   212  // The name must be a relative path: it must not start with a drive
   213  // letter (e.g. C:) or leading slash, and only forward slashes are
   214  // allowed. To create a directory instead of a file, add a trailing
   215  // slash to the name.
   216  // The file's contents must be written to the io.Writer before the next
   217  // call to Create, CreateHeader, or Close.
   218  func (w *Writer) Create(name string) (io.Writer, error) {
   219  	header := &FileHeader{
   220  		Name:   name,
   221  		Method: Deflate,
   222  	}
   223  	return w.CreateHeader(header)
   224  }
   225  
   226  // detectUTF8 reports whether s is a valid UTF-8 string, and whether the string
   227  // must be considered UTF-8 encoding (i.e., not compatible with CP-437, ASCII,
   228  // or any other common encoding).
   229  func detectUTF8(s string) (valid, require bool) {
   230  	for i := 0; i < len(s); {
   231  		r, size := utf8.DecodeRuneInString(s[i:])
   232  		i += size
   233  		// Officially, ZIP uses CP-437, but many readers use the system's
   234  		// local character encoding. Most encoding are compatible with a large
   235  		// subset of CP-437, which itself is ASCII-like.
   236  		//
   237  		// Forbid 0x7e and 0x5c since EUC-KR and Shift-JIS replace those
   238  		// characters with localized currency and overline characters.
   239  		if r < 0x20 || r > 0x7d || r == 0x5c {
   240  			if !utf8.ValidRune(r) || (r == utf8.RuneError && size == 1) {
   241  				return false, false
   242  			}
   243  			require = true
   244  		}
   245  	}
   246  	return true, require
   247  }
   248  
   249  // prepare performs the bookkeeping operations required at the start of
   250  // CreateHeader and CreateRaw.
   251  func (w *Writer) prepare(fh *FileHeader) error {
   252  	if w.last != nil && !w.last.closed {
   253  		if err := w.last.close(); err != nil {
   254  			return err
   255  		}
   256  	}
   257  	if len(w.dir) > 0 && w.dir[len(w.dir)-1].FileHeader == fh {
   258  		// See https://golang.org/issue/11144 confusion.
   259  		return errors.New("archive/zip: invalid duplicate FileHeader")
   260  	}
   261  	return nil
   262  }
   263  
   264  // CreateHeader adds a file to the zip archive using the provided FileHeader
   265  // for the file metadata. Writer takes ownership of fh and may mutate
   266  // its fields. The caller must not modify fh after calling CreateHeader.
   267  //
   268  // This returns a Writer to which the file contents should be written.
   269  // The file's contents must be written to the io.Writer before the next
   270  // call to Create, CreateHeader, CreateRaw, or Close.
   271  func (w *Writer) CreateHeader(fh *FileHeader) (io.Writer, error) {
   272  	if err := w.prepare(fh); err != nil {
   273  		return nil, err
   274  	}
   275  
   276  	// The ZIP format has a sad state of affairs regarding character encoding.
   277  	// Officially, the name and comment fields are supposed to be encoded
   278  	// in CP-437 (which is mostly compatible with ASCII), unless the UTF-8
   279  	// flag bit is set. However, there are several problems:
   280  	//
   281  	//	* Many ZIP readers still do not support UTF-8.
   282  	//	* If the UTF-8 flag is cleared, several readers simply interpret the
   283  	//	name and comment fields as whatever the local system encoding is.
   284  	//
   285  	// In order to avoid breaking readers without UTF-8 support,
   286  	// we avoid setting the UTF-8 flag if the strings are CP-437 compatible.
   287  	// However, if the strings require multibyte UTF-8 encoding and is a
   288  	// valid UTF-8 string, then we set the UTF-8 bit.
   289  	//
   290  	// For the case, where the user explicitly wants to specify the encoding
   291  	// as UTF-8, they will need to set the flag bit themselves.
   292  	utf8Valid1, utf8Require1 := detectUTF8(fh.Name)
   293  	utf8Valid2, utf8Require2 := detectUTF8(fh.Comment)
   294  	switch {
   295  	case fh.NonUTF8:
   296  		fh.Flags &^= 0x800
   297  	case (utf8Require1 || utf8Require2) && (utf8Valid1 && utf8Valid2):
   298  		fh.Flags |= 0x800
   299  	}
   300  
   301  	fh.CreatorVersion = fh.CreatorVersion&0xff00 | zipVersion20 // preserve compatibility byte
   302  	fh.ReaderVersion = zipVersion20
   303  
   304  	// If Modified is set, this takes precedence over MS-DOS timestamp fields.
   305  	if !fh.Modified.IsZero() {
   306  		// Contrary to the FileHeader.SetModTime method, we intentionally
   307  		// do not convert to UTC, because we assume the user intends to encode
   308  		// the date using the specified timezone. A user may want this control
   309  		// because many legacy ZIP readers interpret the timestamp according
   310  		// to the local timezone.
   311  		//
   312  		// The timezone is only non-UTC if a user directly sets the Modified
   313  		// field directly themselves. All other approaches sets UTC.
   314  		fh.ModifiedDate, fh.ModifiedTime = timeToMsDosTime(fh.Modified)
   315  
   316  		// Use "extended timestamp" format since this is what Info-ZIP uses.
   317  		// Nearly every major ZIP implementation uses a different format,
   318  		// but at least most seem to be able to understand the other formats.
   319  		//
   320  		// This format happens to be identical for both local and central header
   321  		// if modification time is the only timestamp being encoded.
   322  		var mbuf [9]byte // 2*SizeOf(uint16) + SizeOf(uint8) + SizeOf(uint32)
   323  		mt := uint32(fh.Modified.Unix())
   324  		eb := writeBuf(mbuf[:])
   325  		eb.uint16(extTimeExtraID)
   326  		eb.uint16(5)  // Size: SizeOf(uint8) + SizeOf(uint32)
   327  		eb.uint8(1)   // Flags: ModTime
   328  		eb.uint32(mt) // ModTime
   329  		fh.Extra = append(fh.Extra, mbuf[:]...)
   330  	}
   331  
   332  	var (
   333  		ow io.Writer
   334  		fw *fileWriter
   335  	)
   336  	h := &header{
   337  		FileHeader: fh,
   338  		offset:     uint64(w.cw.count),
   339  	}
   340  
   341  	if strings.HasSuffix(fh.Name, "/") {
   342  		// Set the compression method to Store to ensure data length is truly zero,
   343  		// which the writeHeader method always encodes for the size fields.
   344  		// This is necessary as most compression formats have non-zero lengths
   345  		// even when compressing an empty string.
   346  		fh.Method = Store
   347  		fh.Flags &^= 0x8 // we will not write a data descriptor
   348  
   349  		// Explicitly clear sizes as they have no meaning for directories.
   350  		fh.CompressedSize = 0
   351  		fh.CompressedSize64 = 0
   352  		fh.UncompressedSize = 0
   353  		fh.UncompressedSize64 = 0
   354  
   355  		ow = dirWriter{}
   356  	} else {
   357  		fh.Flags |= 0x8 // we will write a data descriptor
   358  
   359  		fw = &fileWriter{
   360  			zipw:      w.cw,
   361  			compCount: &countWriter{w: w.cw},
   362  			crc32:     crc32.NewIEEE(),
   363  		}
   364  		comp := w.compressor(fh.Method)
   365  		if comp == nil {
   366  			return nil, ErrAlgorithm
   367  		}
   368  		var err error
   369  		fw.comp, err = comp(fw.compCount)
   370  		if err != nil {
   371  			return nil, err
   372  		}
   373  		fw.rawCount = &countWriter{w: fw.comp}
   374  		fw.header = h
   375  		ow = fw
   376  	}
   377  	w.dir = append(w.dir, h)
   378  	if err := writeHeader(w.cw, h); err != nil {
   379  		return nil, err
   380  	}
   381  	// If we're creating a directory, fw is nil.
   382  	w.last = fw
   383  	return ow, nil
   384  }
   385  
   386  func writeHeader(w io.Writer, h *header) error {
   387  	const maxUint16 = 1<<16 - 1
   388  	if len(h.Name) > maxUint16 {
   389  		return errLongName
   390  	}
   391  	if len(h.Extra) > maxUint16 {
   392  		return errLongExtra
   393  	}
   394  
   395  	var buf [fileHeaderLen]byte
   396  	b := writeBuf(buf[:])
   397  	b.uint32(uint32(fileHeaderSignature))
   398  	b.uint16(h.ReaderVersion)
   399  	b.uint16(h.Flags)
   400  	b.uint16(h.Method)
   401  	b.uint16(h.ModifiedTime)
   402  	b.uint16(h.ModifiedDate)
   403  	// In raw mode (caller does the compression), the values are either
   404  	// written here or in the trailing data descriptor based on the header
   405  	// flags.
   406  	if h.raw && !h.hasDataDescriptor() {
   407  		b.uint32(h.CRC32)
   408  		b.uint32(uint32(min64(h.CompressedSize64, uint32max)))
   409  		b.uint32(uint32(min64(h.UncompressedSize64, uint32max)))
   410  	} else {
   411  		// When this package handle the compression, these values are
   412  		// always written to the trailing data descriptor.
   413  		b.uint32(0) // crc32
   414  		b.uint32(0) // compressed size
   415  		b.uint32(0) // uncompressed size
   416  	}
   417  	b.uint16(uint16(len(h.Name)))
   418  	b.uint16(uint16(len(h.Extra)))
   419  	if _, err := w.Write(buf[:]); err != nil {
   420  		return err
   421  	}
   422  	if _, err := io.WriteString(w, h.Name); err != nil {
   423  		return err
   424  	}
   425  	_, err := w.Write(h.Extra)
   426  	return err
   427  }
   428  
   429  func min64(x, y uint64) uint64 {
   430  	if x < y {
   431  		return x
   432  	}
   433  	return y
   434  }
   435  
   436  // CreateHeaderRaw is replaced by CreateRaw.
   437  // Deprecated: CreateHeaderRaw is replaced by CreateRaw (stdlib name).
   438  func (w *Writer) CreateHeaderRaw(fh *FileHeader) (io.Writer, error) {
   439  	return w.CreateRaw(fh)
   440  }
   441  
   442  // CreateRaw adds a file to the zip archive using the provided FileHeader and
   443  // returns a Writer to which the file contents should be written. The file's
   444  // contents must be written to the io.Writer before the next call to Create,
   445  // CreateHeader, CreateRaw, or Close.
   446  //
   447  // In contrast to CreateHeader, the bytes passed to Writer are not compressed.
   448  func (w *Writer) CreateRaw(fh *FileHeader) (io.Writer, error) {
   449  	if err := w.prepare(fh); err != nil {
   450  		return nil, err
   451  	}
   452  
   453  	fh.CompressedSize = uint32(min64(fh.CompressedSize64, uint32max))
   454  	fh.UncompressedSize = uint32(min64(fh.UncompressedSize64, uint32max))
   455  
   456  	h := &header{
   457  		FileHeader: fh,
   458  		offset:     uint64(w.cw.count),
   459  		raw:        true,
   460  	}
   461  	w.dir = append(w.dir, h)
   462  	if err := writeHeader(w.cw, h); err != nil {
   463  		return nil, err
   464  	}
   465  
   466  	if strings.HasSuffix(fh.Name, "/") {
   467  		w.last = nil
   468  		return dirWriter{}, nil
   469  	}
   470  
   471  	fw := &fileWriter{
   472  		header: h,
   473  		zipw:   w.cw,
   474  	}
   475  	w.last = fw
   476  	return fw, nil
   477  }
   478  
   479  // Copy copies the file f (obtained from a Reader) into w. It copies the raw
   480  // form directly bypassing decompression, compression, and validation.
   481  // CHANGE: Optional file name cannot be specified any more due to stdlib api.
   482  func (w *Writer) Copy(f *File) error {
   483  	r, err := f.OpenRaw()
   484  	if err != nil {
   485  		return err
   486  	}
   487  	fw, err := w.CreateRaw(&f.FileHeader)
   488  	if err != nil {
   489  		return err
   490  	}
   491  	_, err = io.Copy(fw, r)
   492  	return err
   493  }
   494  
   495  // RegisterCompressor registers or overrides a custom compressor for a specific
   496  // method ID. If a compressor for a given method is not found, Writer will
   497  // default to looking up the compressor at the package level.
   498  func (w *Writer) RegisterCompressor(method uint16, comp Compressor) {
   499  	if w.compressors == nil {
   500  		w.compressors = make(map[uint16]Compressor)
   501  	}
   502  	w.compressors[method] = comp
   503  }
   504  
   505  func (w *Writer) compressor(method uint16) Compressor {
   506  	comp := w.compressors[method]
   507  	if comp == nil {
   508  		comp = compressor(method)
   509  	}
   510  	return comp
   511  }
   512  
   513  type dirWriter struct{}
   514  
   515  func (dirWriter) Write(b []byte) (int, error) {
   516  	if len(b) == 0 {
   517  		return 0, nil
   518  	}
   519  	return 0, errors.New("zip: write to directory")
   520  }
   521  
   522  type fileWriter struct {
   523  	*header
   524  	zipw      io.Writer
   525  	rawCount  *countWriter
   526  	comp      io.WriteCloser
   527  	compCount *countWriter
   528  	crc32     hash.Hash32
   529  	closed    bool
   530  }
   531  
   532  func (w *fileWriter) Write(p []byte) (int, error) {
   533  	if w.closed {
   534  		return 0, errors.New("zip: write to closed file")
   535  	}
   536  	if w.raw {
   537  		return w.zipw.Write(p)
   538  	}
   539  	w.crc32.Write(p)
   540  	return w.rawCount.Write(p)
   541  }
   542  
   543  func (w *fileWriter) close() error {
   544  	if w.closed {
   545  		return errors.New("zip: file closed twice")
   546  	}
   547  	w.closed = true
   548  	if w.raw {
   549  		return w.writeDataDescriptor()
   550  	}
   551  	if err := w.comp.Close(); err != nil {
   552  		return err
   553  	}
   554  
   555  	// update FileHeader
   556  	fh := w.header.FileHeader
   557  	fh.CRC32 = w.crc32.Sum32()
   558  	fh.CompressedSize64 = uint64(w.compCount.count)
   559  	fh.UncompressedSize64 = uint64(w.rawCount.count)
   560  
   561  	if fh.isZip64() {
   562  		fh.CompressedSize = uint32max
   563  		fh.UncompressedSize = uint32max
   564  		fh.ReaderVersion = zipVersion45 // requires 4.5 - File uses ZIP64 format extensions
   565  	} else {
   566  		fh.CompressedSize = uint32(fh.CompressedSize64)
   567  		fh.UncompressedSize = uint32(fh.UncompressedSize64)
   568  	}
   569  
   570  	return w.writeDataDescriptor()
   571  }
   572  
   573  func (w *fileWriter) writeDataDescriptor() error {
   574  	if !w.hasDataDescriptor() {
   575  		return nil
   576  	}
   577  	// Write data descriptor. This is more complicated than one would
   578  	// think, see e.g. comments in zipfile.c:putextended() and
   579  	// http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7073588.
   580  	// The approach here is to write 8 byte sizes if needed without
   581  	// adding a zip64 extra in the local header (too late anyway).
   582  	var buf []byte
   583  	if w.isZip64() {
   584  		buf = make([]byte, dataDescriptor64Len)
   585  	} else {
   586  		buf = make([]byte, dataDescriptorLen)
   587  	}
   588  	b := writeBuf(buf)
   589  	b.uint32(dataDescriptorSignature) // de-facto standard, required by OS X
   590  	b.uint32(w.CRC32)
   591  	if w.isZip64() {
   592  		b.uint64(w.CompressedSize64)
   593  		b.uint64(w.UncompressedSize64)
   594  	} else {
   595  		b.uint32(w.CompressedSize)
   596  		b.uint32(w.UncompressedSize)
   597  	}
   598  	_, err := w.zipw.Write(buf)
   599  	return err
   600  }
   601  
   602  type countWriter struct {
   603  	w     io.Writer
   604  	count int64
   605  }
   606  
   607  func (w *countWriter) Write(p []byte) (int, error) {
   608  	n, err := w.w.Write(p)
   609  	w.count += int64(n)
   610  	return n, err
   611  }
   612  
   613  type nopCloser struct {
   614  	io.Writer
   615  }
   616  
   617  func (w nopCloser) Close() error {
   618  	return nil
   619  }
   620  
   621  type writeBuf []byte
   622  
   623  func (b *writeBuf) uint8(v uint8) {
   624  	(*b)[0] = v
   625  	*b = (*b)[1:]
   626  }
   627  
   628  func (b *writeBuf) uint16(v uint16) {
   629  	binary.LittleEndian.PutUint16(*b, v)
   630  	*b = (*b)[2:]
   631  }
   632  
   633  func (b *writeBuf) uint32(v uint32) {
   634  	binary.LittleEndian.PutUint32(*b, v)
   635  	*b = (*b)[4:]
   636  }
   637  
   638  func (b *writeBuf) uint64(v uint64) {
   639  	binary.LittleEndian.PutUint64(*b, v)
   640  	*b = (*b)[8:]
   641  }
   642
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