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Source file src/archive/zip/struct.go

Documentation: archive/zip

  // Copyright 2010 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  /*
  Package zip provides support for reading and writing ZIP archives.
  
  See: https://www.pkware.com/appnote
  
  This package does not support disk spanning.
  
  A note about ZIP64:
  
  To be backwards compatible the FileHeader has both 32 and 64 bit Size
  fields. The 64 bit fields will always contain the correct value and
  for normal archives both fields will be the same. For files requiring
  the ZIP64 format the 32 bit fields will be 0xffffffff and the 64 bit
  fields must be used instead.
  */
  package zip
  
  import (
  	"os"
  	"path"
  	"time"
  )
  
  // Compression methods.
  const (
  	Store   uint16 = 0
  	Deflate uint16 = 8
  )
  
  const (
  	fileHeaderSignature      = 0x04034b50
  	directoryHeaderSignature = 0x02014b50
  	directoryEndSignature    = 0x06054b50
  	directory64LocSignature  = 0x07064b50
  	directory64EndSignature  = 0x06064b50
  	dataDescriptorSignature  = 0x08074b50 // de-facto standard; required by OS X Finder
  	fileHeaderLen            = 30         // + filename + extra
  	directoryHeaderLen       = 46         // + filename + extra + comment
  	directoryEndLen          = 22         // + comment
  	dataDescriptorLen        = 16         // four uint32: descriptor signature, crc32, compressed size, size
  	dataDescriptor64Len      = 24         // descriptor with 8 byte sizes
  	directory64LocLen        = 20         //
  	directory64EndLen        = 56         // + extra
  
  	// Constants for the first byte in CreatorVersion
  	creatorFAT    = 0
  	creatorUnix   = 3
  	creatorNTFS   = 11
  	creatorVFAT   = 14
  	creatorMacOSX = 19
  
  	// version numbers
  	zipVersion20 = 20 // 2.0
  	zipVersion45 = 45 // 4.5 (reads and writes zip64 archives)
  
  	// limits for non zip64 files
  	uint16max = (1 << 16) - 1
  	uint32max = (1 << 32) - 1
  
  	// extra header id's
  	zip64ExtraId = 0x0001 // zip64 Extended Information Extra Field
  )
  
  // FileHeader describes a file within a zip file.
  // See the zip spec for details.
  type FileHeader struct {
  	// Name is the name of the file.
  	// It must be a relative path: it must not start with a drive
  	// letter (e.g. C:) or leading slash, and only forward slashes
  	// are allowed.
  	Name string
  
  	CreatorVersion     uint16
  	ReaderVersion      uint16
  	Flags              uint16
  	Method             uint16
  	ModifiedTime       uint16 // MS-DOS time
  	ModifiedDate       uint16 // MS-DOS date
  	CRC32              uint32
  	CompressedSize     uint32 // Deprecated: Use CompressedSize64 instead.
  	UncompressedSize   uint32 // Deprecated: Use UncompressedSize64 instead.
  	CompressedSize64   uint64
  	UncompressedSize64 uint64
  	Extra              []byte
  	ExternalAttrs      uint32 // Meaning depends on CreatorVersion
  	Comment            string
  }
  
  // FileInfo returns an os.FileInfo for the FileHeader.
  func (h *FileHeader) FileInfo() os.FileInfo {
  	return headerFileInfo{h}
  }
  
  // headerFileInfo implements os.FileInfo.
  type headerFileInfo struct {
  	fh *FileHeader
  }
  
  func (fi headerFileInfo) Name() string { return path.Base(fi.fh.Name) }
  func (fi headerFileInfo) Size() int64 {
  	if fi.fh.UncompressedSize64 > 0 {
  		return int64(fi.fh.UncompressedSize64)
  	}
  	return int64(fi.fh.UncompressedSize)
  }
  func (fi headerFileInfo) IsDir() bool        { return fi.Mode().IsDir() }
  func (fi headerFileInfo) ModTime() time.Time { return fi.fh.ModTime() }
  func (fi headerFileInfo) Mode() os.FileMode  { return fi.fh.Mode() }
  func (fi headerFileInfo) Sys() interface{}   { return fi.fh }
  
  // FileInfoHeader creates a partially-populated FileHeader from an
  // os.FileInfo.
  // Because os.FileInfo's Name method returns only the base name of
  // the file it describes, it may be necessary to modify the Name field
  // of the returned header to provide the full path name of the file.
  func FileInfoHeader(fi os.FileInfo) (*FileHeader, error) {
  	size := fi.Size()
  	fh := &FileHeader{
  		Name:               fi.Name(),
  		UncompressedSize64: uint64(size),
  	}
  	fh.SetModTime(fi.ModTime())
  	fh.SetMode(fi.Mode())
  	if fh.UncompressedSize64 > uint32max {
  		fh.UncompressedSize = uint32max
  	} else {
  		fh.UncompressedSize = uint32(fh.UncompressedSize64)
  	}
  	return fh, nil
  }
  
  type directoryEnd struct {
  	diskNbr            uint32 // unused
  	dirDiskNbr         uint32 // unused
  	dirRecordsThisDisk uint64 // unused
  	directoryRecords   uint64
  	directorySize      uint64
  	directoryOffset    uint64 // relative to file
  	commentLen         uint16
  	comment            string
  }
  
  // msDosTimeToTime converts an MS-DOS date and time into a time.Time.
  // The resolution is 2s.
  // See: http://msdn.microsoft.com/en-us/library/ms724247(v=VS.85).aspx
  func msDosTimeToTime(dosDate, dosTime uint16) time.Time {
  	return time.Date(
  		// date bits 0-4: day of month; 5-8: month; 9-15: years since 1980
  		int(dosDate>>9+1980),
  		time.Month(dosDate>>5&0xf),
  		int(dosDate&0x1f),
  
  		// time bits 0-4: second/2; 5-10: minute; 11-15: hour
  		int(dosTime>>11),
  		int(dosTime>>5&0x3f),
  		int(dosTime&0x1f*2),
  		0, // nanoseconds
  
  		time.UTC,
  	)
  }
  
  // timeToMsDosTime converts a time.Time to an MS-DOS date and time.
  // The resolution is 2s.
  // See: http://msdn.microsoft.com/en-us/library/ms724274(v=VS.85).aspx
  func timeToMsDosTime(t time.Time) (fDate uint16, fTime uint16) {
  	t = t.In(time.UTC)
  	fDate = uint16(t.Day() + int(t.Month())<<5 + (t.Year()-1980)<<9)
  	fTime = uint16(t.Second()/2 + t.Minute()<<5 + t.Hour()<<11)
  	return
  }
  
  // ModTime returns the modification time in UTC.
  // The resolution is 2s.
  func (h *FileHeader) ModTime() time.Time {
  	return msDosTimeToTime(h.ModifiedDate, h.ModifiedTime)
  }
  
  // SetModTime sets the ModifiedTime and ModifiedDate fields to the given time in UTC.
  // The resolution is 2s.
  func (h *FileHeader) SetModTime(t time.Time) {
  	h.ModifiedDate, h.ModifiedTime = timeToMsDosTime(t)
  }
  
  const (
  	// Unix constants. The specification doesn't mention them,
  	// but these seem to be the values agreed on by tools.
  	s_IFMT   = 0xf000
  	s_IFSOCK = 0xc000
  	s_IFLNK  = 0xa000
  	s_IFREG  = 0x8000
  	s_IFBLK  = 0x6000
  	s_IFDIR  = 0x4000
  	s_IFCHR  = 0x2000
  	s_IFIFO  = 0x1000
  	s_ISUID  = 0x800
  	s_ISGID  = 0x400
  	s_ISVTX  = 0x200
  
  	msdosDir      = 0x10
  	msdosReadOnly = 0x01
  )
  
  // Mode returns the permission and mode bits for the FileHeader.
  func (h *FileHeader) Mode() (mode os.FileMode) {
  	switch h.CreatorVersion >> 8 {
  	case creatorUnix, creatorMacOSX:
  		mode = unixModeToFileMode(h.ExternalAttrs >> 16)
  	case creatorNTFS, creatorVFAT, creatorFAT:
  		mode = msdosModeToFileMode(h.ExternalAttrs)
  	}
  	if len(h.Name) > 0 && h.Name[len(h.Name)-1] == '/' {
  		mode |= os.ModeDir
  	}
  	return mode
  }
  
  // SetMode changes the permission and mode bits for the FileHeader.
  func (h *FileHeader) SetMode(mode os.FileMode) {
  	h.CreatorVersion = h.CreatorVersion&0xff | creatorUnix<<8
  	h.ExternalAttrs = fileModeToUnixMode(mode) << 16
  
  	// set MSDOS attributes too, as the original zip does.
  	if mode&os.ModeDir != 0 {
  		h.ExternalAttrs |= msdosDir
  	}
  	if mode&0200 == 0 {
  		h.ExternalAttrs |= msdosReadOnly
  	}
  }
  
  // isZip64 reports whether the file size exceeds the 32 bit limit
  func (fh *FileHeader) isZip64() bool {
  	return fh.CompressedSize64 >= uint32max || fh.UncompressedSize64 >= uint32max
  }
  
  func msdosModeToFileMode(m uint32) (mode os.FileMode) {
  	if m&msdosDir != 0 {
  		mode = os.ModeDir | 0777
  	} else {
  		mode = 0666
  	}
  	if m&msdosReadOnly != 0 {
  		mode &^= 0222
  	}
  	return mode
  }
  
  func fileModeToUnixMode(mode os.FileMode) uint32 {
  	var m uint32
  	switch mode & os.ModeType {
  	default:
  		m = s_IFREG
  	case os.ModeDir:
  		m = s_IFDIR
  	case os.ModeSymlink:
  		m = s_IFLNK
  	case os.ModeNamedPipe:
  		m = s_IFIFO
  	case os.ModeSocket:
  		m = s_IFSOCK
  	case os.ModeDevice:
  		if mode&os.ModeCharDevice != 0 {
  			m = s_IFCHR
  		} else {
  			m = s_IFBLK
  		}
  	}
  	if mode&os.ModeSetuid != 0 {
  		m |= s_ISUID
  	}
  	if mode&os.ModeSetgid != 0 {
  		m |= s_ISGID
  	}
  	if mode&os.ModeSticky != 0 {
  		m |= s_ISVTX
  	}
  	return m | uint32(mode&0777)
  }
  
  func unixModeToFileMode(m uint32) os.FileMode {
  	mode := os.FileMode(m & 0777)
  	switch m & s_IFMT {
  	case s_IFBLK:
  		mode |= os.ModeDevice
  	case s_IFCHR:
  		mode |= os.ModeDevice | os.ModeCharDevice
  	case s_IFDIR:
  		mode |= os.ModeDir
  	case s_IFIFO:
  		mode |= os.ModeNamedPipe
  	case s_IFLNK:
  		mode |= os.ModeSymlink
  	case s_IFREG:
  		// nothing to do
  	case s_IFSOCK:
  		mode |= os.ModeSocket
  	}
  	if m&s_ISGID != 0 {
  		mode |= os.ModeSetgid
  	}
  	if m&s_ISUID != 0 {
  		mode |= os.ModeSetuid
  	}
  	if m&s_ISVTX != 0 {
  		mode |= os.ModeSticky
  	}
  	return mode
  }
  

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