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// Copyright 2011 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
import (
"bufio"
"encoding/binary"
"errors"
"hash"
"hash/crc32"
"io"
)
// TODO(adg): support zip file comments
// TODO(adg): support specifying deflate level
// Writer implements a zip file writer.
type Writer struct {
cw *countWriter
dir []*header
last *fileWriter
closed bool
}
type header struct {
*FileHeader
offset uint64
}
// NewWriter returns a new Writer writing a zip file to w.
func NewWriter(w io.Writer) *Writer {
return &Writer{cw: &countWriter{w: bufio.NewWriter(w)}}
}
// SetOffset sets the offset of the beginning of the zip data within the
// underlying writer. It should be used when the zip data is appended to an
// existing file, such as a binary executable.
// It must be called before any data is written.
func (w *Writer) SetOffset(n int64) {
if w.cw.count != 0 {
panic("zip: SetOffset called after data was written")
}
w.cw.count = n
}
// Flush flushes any buffered data to the underlying writer.
// Calling Flush is not normally necessary; calling Close is sufficient.
func (w *Writer) Flush() error {
return w.cw.w.(*bufio.Writer).Flush()
}
// Close finishes writing the zip file by writing the central directory.
// It does not (and can not) close the underlying writer.
func (w *Writer) Close() error {
if w.last != nil && !w.last.closed {
if err := w.last.close(); err != nil {
return err
}
w.last = nil
}
if w.closed {
return errors.New("zip: writer closed twice")
}
w.closed = true
// write central directory
start := w.cw.count
for _, h := range w.dir {
var buf [directoryHeaderLen]byte
b := writeBuf(buf[:])
b.uint32(uint32(directoryHeaderSignature))
b.uint16(h.CreatorVersion)
b.uint16(h.ReaderVersion)
b.uint16(h.Flags)
b.uint16(h.Method)
b.uint16(h.ModifiedTime)
b.uint16(h.ModifiedDate)
b.uint32(h.CRC32)
if h.isZip64() || h.offset > uint32max {
// the file needs a zip64 header. store maxint in both
// 32 bit size fields (and offset later) to signal that the
// zip64 extra header should be used.
b.uint32(uint32max) // compressed size
b.uint32(uint32max) // uncompressed size
// append a zip64 extra block to Extra
var buf [28]byte // 2x uint16 + 3x uint64
eb := writeBuf(buf[:])
eb.uint16(zip64ExtraId)
eb.uint16(24) // size = 3x uint64
eb.uint64(h.UncompressedSize64)
eb.uint64(h.CompressedSize64)
eb.uint64(h.offset)
h.Extra = append(h.Extra, buf[:]...)
} else {
b.uint32(h.CompressedSize)
b.uint32(h.UncompressedSize)
}
b.uint16(uint16(len(h.Name)))
b.uint16(uint16(len(h.Extra)))
b.uint16(uint16(len(h.Comment)))
b = b[4:] // skip disk number start and internal file attr (2x uint16)
b.uint32(h.ExternalAttrs)
if h.offset > uint32max {
b.uint32(uint32max)
} else {
b.uint32(uint32(h.offset))
}
if _, err := w.cw.Write(buf[:]); err != nil {
return err
}
if _, err := io.WriteString(w.cw, h.Name); err != nil {
return err
}
if _, err := w.cw.Write(h.Extra); err != nil {
return err
}
if _, err := io.WriteString(w.cw, h.Comment); err != nil {
return err
}
}
end := w.cw.count
records := uint64(len(w.dir))
size := uint64(end - start)
offset := uint64(start)
if records > uint16max || size > uint32max || offset > uint32max {
var buf [directory64EndLen + directory64LocLen]byte
b := writeBuf(buf[:])
// zip64 end of central directory record
b.uint32(directory64EndSignature)
b.uint64(directory64EndLen - 12) // length minus signature (uint32) and length fields (uint64)
b.uint16(zipVersion45) // version made by
b.uint16(zipVersion45) // version needed to extract
b.uint32(0) // number of this disk
b.uint32(0) // number of the disk with the start of the central directory
b.uint64(records) // total number of entries in the central directory on this disk
b.uint64(records) // total number of entries in the central directory
b.uint64(size) // size of the central directory
b.uint64(offset) // offset of start of central directory with respect to the starting disk number
// zip64 end of central directory locator
b.uint32(directory64LocSignature)
b.uint32(0) // number of the disk with the start of the zip64 end of central directory
b.uint64(uint64(end)) // relative offset of the zip64 end of central directory record
b.uint32(1) // total number of disks
if _, err := w.cw.Write(buf[:]); err != nil {
return err
}
// store max values in the regular end record to signal that
// that the zip64 values should be used instead
records = uint16max
size = uint32max
offset = uint32max
}
// write end record
var buf [directoryEndLen]byte
b := writeBuf(buf[:])
b.uint32(uint32(directoryEndSignature))
b = b[4:] // skip over disk number and first disk number (2x uint16)
b.uint16(uint16(records)) // number of entries this disk
b.uint16(uint16(records)) // number of entries total
b.uint32(uint32(size)) // size of directory
b.uint32(uint32(offset)) // start of directory
// skipped size of comment (always zero)
if _, err := w.cw.Write(buf[:]); err != nil {
return err
}
return w.cw.w.(*bufio.Writer).Flush()
}
// Create adds a file to the zip file using the provided name.
// It returns a Writer to which the file contents should be written.
// The name 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.
// The file's contents must be written to the io.Writer before the next
// call to Create, CreateHeader, or Close.
func (w *Writer) Create(name string) (io.Writer, error) {
header := &FileHeader{
Name: name,
Method: Deflate,
}
return w.CreateHeader(header)
}
// CreateHeader adds a file to the zip file using the provided FileHeader
// for the file metadata.
// It returns a Writer to which the file contents should be written.
// The file's contents must be written to the io.Writer before the next
// call to Create, CreateHeader, or Close.
func (w *Writer) CreateHeader(fh *FileHeader) (io.Writer, error) {
if w.last != nil && !w.last.closed {
if err := w.last.close(); err != nil {
return nil, err
}
}
fh.Flags |= 0x8 // we will write a data descriptor
fh.CreatorVersion = fh.CreatorVersion&0xff00 | zipVersion20 // preserve compatibility byte
fh.ReaderVersion = zipVersion20
fw := &fileWriter{
zipw: w.cw,
compCount: &countWriter{w: w.cw},
crc32: crc32.NewIEEE(),
}
comp := compressor(fh.Method)
if comp == nil {
return nil, ErrAlgorithm
}
var err error
fw.comp, err = comp(fw.compCount)
if err != nil {
return nil, err
}
fw.rawCount = &countWriter{w: fw.comp}
h := &header{
FileHeader: fh,
offset: uint64(w.cw.count),
}
w.dir = append(w.dir, h)
fw.header = h
if err := writeHeader(w.cw, fh); err != nil {
return nil, err
}
w.last = fw
return fw, nil
}
func writeHeader(w io.Writer, h *FileHeader) error {
var buf [fileHeaderLen]byte
b := writeBuf(buf[:])
b.uint32(uint32(fileHeaderSignature))
b.uint16(h.ReaderVersion)
b.uint16(h.Flags)
b.uint16(h.Method)
b.uint16(h.ModifiedTime)
b.uint16(h.ModifiedDate)
b.uint32(0) // since we are writing a data descriptor crc32,
b.uint32(0) // compressed size,
b.uint32(0) // and uncompressed size should be zero
b.uint16(uint16(len(h.Name)))
b.uint16(uint16(len(h.Extra)))
if _, err := w.Write(buf[:]); err != nil {
return err
}
if _, err := io.WriteString(w, h.Name); err != nil {
return err
}
_, err := w.Write(h.Extra)
return err
}
type fileWriter struct {
*header
zipw io.Writer
rawCount *countWriter
comp io.WriteCloser
compCount *countWriter
crc32 hash.Hash32
closed bool
}
func (w *fileWriter) Write(p []byte) (int, error) {
if w.closed {
return 0, errors.New("zip: write to closed file")
}
w.crc32.Write(p)
return w.rawCount.Write(p)
}
func (w *fileWriter) close() error {
if w.closed {
return errors.New("zip: file closed twice")
}
w.closed = true
if err := w.comp.Close(); err != nil {
return err
}
// update FileHeader
fh := w.header.FileHeader
fh.CRC32 = w.crc32.Sum32()
fh.CompressedSize64 = uint64(w.compCount.count)
fh.UncompressedSize64 = uint64(w.rawCount.count)
if fh.isZip64() {
fh.CompressedSize = uint32max
fh.UncompressedSize = uint32max
fh.ReaderVersion = zipVersion45 // requires 4.5 - File uses ZIP64 format extensions
} else {
fh.CompressedSize = uint32(fh.CompressedSize64)
fh.UncompressedSize = uint32(fh.UncompressedSize64)
}
// Write data descriptor. This is more complicated than one would
// think, see e.g. comments in zipfile.c:putextended() and
// http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7073588.
// The approach here is to write 8 byte sizes if needed without
// adding a zip64 extra in the local header (too late anyway).
var buf []byte
if fh.isZip64() {
buf = make([]byte, dataDescriptor64Len)
} else {
buf = make([]byte, dataDescriptorLen)
}
b := writeBuf(buf)
b.uint32(dataDescriptorSignature) // de-facto standard, required by OS X
b.uint32(fh.CRC32)
if fh.isZip64() {
b.uint64(fh.CompressedSize64)
b.uint64(fh.UncompressedSize64)
} else {
b.uint32(fh.CompressedSize)
b.uint32(fh.UncompressedSize)
}
_, err := w.zipw.Write(buf)
return err
}
type countWriter struct {
w io.Writer
count int64
}
func (w *countWriter) Write(p []byte) (int, error) {
n, err := w.w.Write(p)
w.count += int64(n)
return n, err
}
type nopCloser struct {
io.Writer
}
func (w nopCloser) Close() error {
return nil
}
type writeBuf []byte
func (b *writeBuf) uint16(v uint16) {
binary.LittleEndian.PutUint16(*b, v)
*b = (*b)[2:]
}
func (b *writeBuf) uint32(v uint32) {
binary.LittleEndian.PutUint32(*b, v)
*b = (*b)[4:]
}
func (b *writeBuf) uint64(v uint64) {
binary.LittleEndian.PutUint64(*b, v)
*b = (*b)[8:]
}