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Source file src/pkg/archive/zip/writer.go

     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	)
    15	
    16	// TODO(adg): support zip file comments
    17	// TODO(adg): support specifying deflate level
    18	
    19	// Writer implements a zip file writer.
    20	type Writer struct {
    21		cw     *countWriter
    22		dir    []*header
    23		last   *fileWriter
    24		closed bool
    25	}
    26	
    27	type header struct {
    28		*FileHeader
    29		offset uint64
    30	}
    31	
    32	// NewWriter returns a new Writer writing a zip file to w.
    33	func NewWriter(w io.Writer) *Writer {
    34		return &Writer{cw: &countWriter{w: bufio.NewWriter(w)}}
    35	}
    36	
    37	// Close finishes writing the zip file by writing the central directory.
    38	// It does not (and can not) close the underlying writer.
    39	func (w *Writer) Close() error {
    40		if w.last != nil && !w.last.closed {
    41			if err := w.last.close(); err != nil {
    42				return err
    43			}
    44			w.last = nil
    45		}
    46		if w.closed {
    47			return errors.New("zip: writer closed twice")
    48		}
    49		w.closed = true
    50	
    51		// write central directory
    52		start := w.cw.count
    53		for _, h := range w.dir {
    54			var buf [directoryHeaderLen]byte
    55			b := writeBuf(buf[:])
    56			b.uint32(uint32(directoryHeaderSignature))
    57			b.uint16(h.CreatorVersion)
    58			b.uint16(h.ReaderVersion)
    59			b.uint16(h.Flags)
    60			b.uint16(h.Method)
    61			b.uint16(h.ModifiedTime)
    62			b.uint16(h.ModifiedDate)
    63			b.uint32(h.CRC32)
    64			if h.isZip64() || h.offset > uint32max {
    65				// the file needs a zip64 header. store maxint in both
    66				// 32 bit size fields (and offset later) to signal that the
    67				// zip64 extra header should be used.
    68				b.uint32(uint32max) // compressed size
    69				b.uint32(uint32max) // uncompressed size
    70	
    71				// append a zip64 extra block to Extra
    72				var buf [28]byte // 2x uint16 + 3x uint64
    73				eb := writeBuf(buf[:])
    74				eb.uint16(zip64ExtraId)
    75				eb.uint16(24) // size = 3x uint64
    76				eb.uint64(h.UncompressedSize64)
    77				eb.uint64(h.CompressedSize64)
    78				eb.uint64(h.offset)
    79				h.Extra = append(h.Extra, buf[:]...)
    80			} else {
    81				b.uint32(h.CompressedSize)
    82				b.uint32(h.UncompressedSize)
    83			}
    84			b.uint16(uint16(len(h.Name)))
    85			b.uint16(uint16(len(h.Extra)))
    86			b.uint16(uint16(len(h.Comment)))
    87			b = b[4:] // skip disk number start and internal file attr (2x uint16)
    88			b.uint32(h.ExternalAttrs)
    89			if h.offset > uint32max {
    90				b.uint32(uint32max)
    91			} else {
    92				b.uint32(uint32(h.offset))
    93			}
    94			if _, err := w.cw.Write(buf[:]); err != nil {
    95				return err
    96			}
    97			if _, err := io.WriteString(w.cw, h.Name); err != nil {
    98				return err
    99			}
   100			if _, err := w.cw.Write(h.Extra); err != nil {
   101				return err
   102			}
   103			if _, err := io.WriteString(w.cw, h.Comment); err != nil {
   104				return err
   105			}
   106		}
   107		end := w.cw.count
   108	
   109		records := uint64(len(w.dir))
   110		size := uint64(end - start)
   111		offset := uint64(start)
   112	
   113		if records > uint16max || size > uint32max || offset > uint32max {
   114			var buf [directory64EndLen + directory64LocLen]byte
   115			b := writeBuf(buf[:])
   116	
   117			// zip64 end of central directory record
   118			b.uint32(directory64EndSignature)
   119			b.uint64(directory64EndLen)
   120			b.uint16(zipVersion45) // version made by
   121			b.uint16(zipVersion45) // version needed to extract
   122			b.uint32(0)            // number of this disk
   123			b.uint32(0)            // number of the disk with the start of the central directory
   124			b.uint64(records)      // total number of entries in the central directory on this disk
   125			b.uint64(records)      // total number of entries in the central directory
   126			b.uint64(size)         // size of the central directory
   127			b.uint64(offset)       // offset of start of central directory with respect to the starting disk number
   128	
   129			// zip64 end of central directory locator
   130			b.uint32(directory64LocSignature)
   131			b.uint32(0)           // number of the disk with the start of the zip64 end of central directory
   132			b.uint64(uint64(end)) // relative offset of the zip64 end of central directory record
   133			b.uint32(1)           // total number of disks
   134	
   135			if _, err := w.cw.Write(buf[:]); err != nil {
   136				return err
   137			}
   138	
   139			// store max values in the regular end record to signal that
   140			// that the zip64 values should be used instead
   141			records = uint16max
   142			size = uint32max
   143			offset = uint32max
   144		}
   145	
   146		// write end record
   147		var buf [directoryEndLen]byte
   148		b := writeBuf(buf[:])
   149		b.uint32(uint32(directoryEndSignature))
   150		b = b[4:]                 // skip over disk number and first disk number (2x uint16)
   151		b.uint16(uint16(records)) // number of entries this disk
   152		b.uint16(uint16(records)) // number of entries total
   153		b.uint32(uint32(size))    // size of directory
   154		b.uint32(uint32(offset))  // start of directory
   155		// skipped size of comment (always zero)
   156		if _, err := w.cw.Write(buf[:]); err != nil {
   157			return err
   158		}
   159	
   160		return w.cw.w.(*bufio.Writer).Flush()
   161	}
   162	
   163	// Create adds a file to the zip file using the provided name.
   164	// It returns a Writer to which the file contents should be written.
   165	// The name must be a relative path: it must not start with a drive
   166	// letter (e.g. C:) or leading slash, and only forward slashes are
   167	// allowed.
   168	// The file's contents must be written to the io.Writer before the next
   169	// call to Create, CreateHeader, or Close.
   170	func (w *Writer) Create(name string) (io.Writer, error) {
   171		header := &FileHeader{
   172			Name:   name,
   173			Method: Deflate,
   174		}
   175		return w.CreateHeader(header)
   176	}
   177	
   178	// CreateHeader adds a file to the zip file using the provided FileHeader
   179	// for the file metadata.
   180	// It returns a Writer to which the file contents should be written.
   181	// The file's contents must be written to the io.Writer before the next
   182	// call to Create, CreateHeader, or Close.
   183	func (w *Writer) CreateHeader(fh *FileHeader) (io.Writer, error) {
   184		if w.last != nil && !w.last.closed {
   185			if err := w.last.close(); err != nil {
   186				return nil, err
   187			}
   188		}
   189	
   190		fh.Flags |= 0x8 // we will write a data descriptor
   191	
   192		fh.CreatorVersion = fh.CreatorVersion&0xff00 | zipVersion20 // preserve compatibility byte
   193		fh.ReaderVersion = zipVersion20
   194	
   195		fw := &fileWriter{
   196			zipw:      w.cw,
   197			compCount: &countWriter{w: w.cw},
   198			crc32:     crc32.NewIEEE(),
   199		}
   200		comp := compressor(fh.Method)
   201		if comp == nil {
   202			return nil, ErrAlgorithm
   203		}
   204		var err error
   205		fw.comp, err = comp(fw.compCount)
   206		if err != nil {
   207			return nil, err
   208		}
   209		fw.rawCount = &countWriter{w: fw.comp}
   210	
   211		h := &header{
   212			FileHeader: fh,
   213			offset:     uint64(w.cw.count),
   214		}
   215		w.dir = append(w.dir, h)
   216		fw.header = h
   217	
   218		if err := writeHeader(w.cw, fh); err != nil {
   219			return nil, err
   220		}
   221	
   222		w.last = fw
   223		return fw, nil
   224	}
   225	
   226	func writeHeader(w io.Writer, h *FileHeader) error {
   227		var buf [fileHeaderLen]byte
   228		b := writeBuf(buf[:])
   229		b.uint32(uint32(fileHeaderSignature))
   230		b.uint16(h.ReaderVersion)
   231		b.uint16(h.Flags)
   232		b.uint16(h.Method)
   233		b.uint16(h.ModifiedTime)
   234		b.uint16(h.ModifiedDate)
   235		b.uint32(0) // since we are writing a data descriptor crc32,
   236		b.uint32(0) // compressed size,
   237		b.uint32(0) // and uncompressed size should be zero
   238		b.uint16(uint16(len(h.Name)))
   239		b.uint16(uint16(len(h.Extra)))
   240		if _, err := w.Write(buf[:]); err != nil {
   241			return err
   242		}
   243		if _, err := io.WriteString(w, h.Name); err != nil {
   244			return err
   245		}
   246		_, err := w.Write(h.Extra)
   247		return err
   248	}
   249	
   250	type fileWriter struct {
   251		*header
   252		zipw      io.Writer
   253		rawCount  *countWriter
   254		comp      io.WriteCloser
   255		compCount *countWriter
   256		crc32     hash.Hash32
   257		closed    bool
   258	}
   259	
   260	func (w *fileWriter) Write(p []byte) (int, error) {
   261		if w.closed {
   262			return 0, errors.New("zip: write to closed file")
   263		}
   264		w.crc32.Write(p)
   265		return w.rawCount.Write(p)
   266	}
   267	
   268	func (w *fileWriter) close() error {
   269		if w.closed {
   270			return errors.New("zip: file closed twice")
   271		}
   272		w.closed = true
   273		if err := w.comp.Close(); err != nil {
   274			return err
   275		}
   276	
   277		// update FileHeader
   278		fh := w.header.FileHeader
   279		fh.CRC32 = w.crc32.Sum32()
   280		fh.CompressedSize64 = uint64(w.compCount.count)
   281		fh.UncompressedSize64 = uint64(w.rawCount.count)
   282	
   283		if fh.isZip64() {
   284			fh.CompressedSize = uint32max
   285			fh.UncompressedSize = uint32max
   286			fh.ReaderVersion = zipVersion45 // requires 4.5 - File uses ZIP64 format extensions
   287		} else {
   288			fh.CompressedSize = uint32(fh.CompressedSize64)
   289			fh.UncompressedSize = uint32(fh.UncompressedSize64)
   290		}
   291	
   292		// Write data descriptor. This is more complicated than one would
   293		// think, see e.g. comments in zipfile.c:putextended() and
   294		// http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7073588.
   295		// The approach here is to write 8 byte sizes if needed without
   296		// adding a zip64 extra in the local header (too late anyway).
   297		var buf []byte
   298		if fh.isZip64() {
   299			buf = make([]byte, dataDescriptor64Len)
   300		} else {
   301			buf = make([]byte, dataDescriptorLen)
   302		}
   303		b := writeBuf(buf)
   304		b.uint32(dataDescriptorSignature) // de-facto standard, required by OS X
   305		b.uint32(fh.CRC32)
   306		if fh.isZip64() {
   307			b.uint64(fh.CompressedSize64)
   308			b.uint64(fh.UncompressedSize64)
   309		} else {
   310			b.uint32(fh.CompressedSize)
   311			b.uint32(fh.UncompressedSize)
   312		}
   313		_, err := w.zipw.Write(buf)
   314		return err
   315	}
   316	
   317	type countWriter struct {
   318		w     io.Writer
   319		count int64
   320	}
   321	
   322	func (w *countWriter) Write(p []byte) (int, error) {
   323		n, err := w.w.Write(p)
   324		w.count += int64(n)
   325		return n, err
   326	}
   327	
   328	type nopCloser struct {
   329		io.Writer
   330	}
   331	
   332	func (w nopCloser) Close() error {
   333		return nil
   334	}
   335	
   336	type writeBuf []byte
   337	
   338	func (b *writeBuf) uint16(v uint16) {
   339		binary.LittleEndian.PutUint16(*b, v)
   340		*b = (*b)[2:]
   341	}
   342	
   343	func (b *writeBuf) uint32(v uint32) {
   344		binary.LittleEndian.PutUint32(*b, v)
   345		*b = (*b)[4:]
   346	}
   347	
   348	func (b *writeBuf) uint64(v uint64) {
   349		binary.LittleEndian.PutUint64(*b, v)
   350		*b = (*b)[8:]
   351	}

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