archive/zip: add Writer

R=bradfitz, dchest, r, rsc
CC=golang-dev
https://golang.org/cl/4523077

src/pkg/archive/zip/Makefile

@@ -8,5 +8,6 @@ TARG=archive/zip
 GOFILES=\
 	reader.go\
 	struct.go\
+	writer.go\
 
 include ../../../Make.pkg

src/pkg/archive/zip/reader.go

@@ -2,13 +2,6 @@
 // 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 ZIP archives.
-
-See: http://www.pkware.com/documents/casestudies/APPNOTE.TXT
-
-This package does not support ZIP64 or disk spanning.
-*/
 package zip
 
 import (
@@ -24,9 +17,9 @@ import (
 )
 
 var (
-	FormatError       = os.NewError("not a valid zip file")
-	UnsupportedMethod = os.NewError("unsupported compression algorithm")
-	ChecksumError     = os.NewError("checksum error")
+	FormatError       = os.NewError("zip: not a valid zip file")
+	UnsupportedMethod = os.NewError("zip: unsupported compression algorithm")
+	ChecksumError     = os.NewError("zip: checksum error")
 )
 
 type Reader struct {
@@ -52,7 +45,7 @@ func (f *File) hasDataDescriptor() bool {
 	return f.Flags&0x8 != 0
 }
 
-// OpenReader will open the Zip file specified by name and return a ReaderCloser.
+// OpenReader will open the Zip file specified by name and return a ReadCloser.
 func OpenReader(name string) (*ReadCloser, os.Error) {
 	f, err := os.Open(name)
 	if err != nil {
@@ -111,6 +104,7 @@ func (rc *ReadCloser) Close() os.Error {
 // Open returns a ReadCloser that provides access to the File's contents.
 func (f *File) Open() (rc io.ReadCloser, err os.Error) {
 	off := int64(f.headerOffset)
+	size := int64(f.CompressedSize)
 	if f.bodyOffset == 0 {
 		r := io.NewSectionReader(f.zipr, off, f.zipsize-off)
 		if err = readFileHeader(f, r); err != nil {
@@ -119,21 +113,19 @@ func (f *File) Open() (rc io.ReadCloser, err os.Error) {
 		if f.bodyOffset, err = r.Seek(0, os.SEEK_CUR); err != nil {
 			return
 		}
-	}
-	size := int64(f.CompressedSize)
-	if f.hasDataDescriptor() {
 		if size == 0 {
-			// permit SectionReader to see the rest of the file
-			size = f.zipsize - (off + f.bodyOffset)
-		} else {
-			size += dataDescriptorLen
+			size = int64(f.CompressedSize)
 		}
 	}
+	if f.hasDataDescriptor() && size == 0 {
+		// permit SectionReader to see the rest of the file
+		size = f.zipsize - (off + f.bodyOffset)
+	}
 	r := io.NewSectionReader(f.zipr, off+f.bodyOffset, size)
 	switch f.Method {
-	case 0: // store (no compression)
+	case Store: // (no compression)
 		rc = ioutil.NopCloser(r)
-	case 8: // DEFLATE
+	case Deflate:
 		rc = flate.NewReader(r)
 	default:
 		err = UnsupportedMethod
@@ -171,11 +163,7 @@ func (r *checksumReader) Read(b []byte) (n int, err os.Error) {
 func (r *checksumReader) Close() os.Error { return r.rc.Close() }
 
 func readFileHeader(f *File, r io.Reader) (err os.Error) {
-	defer func() {
-		if rerr, ok := recover().(os.Error); ok {
-			err = rerr
-		}
-	}()
+	defer recoverError(&err)
 	var (
 		signature      uint32
 		filenameLength uint16
@@ -201,11 +189,7 @@ func readFileHeader(f *File, r io.Reader) (err os.Error) {
 }
 
 func readDirectoryHeader(f *File, r io.Reader) (err os.Error) {
-	defer func() {
-		if rerr, ok := recover().(os.Error); ok {
-			err = rerr
-		}
-	}()
+	defer recoverError(&err)
 	var (
 		signature          uint32
 		filenameLength     uint16
@@ -242,18 +226,14 @@ func readDirectoryHeader(f *File, r io.Reader) (err os.Error) {
 }
 
 func readDataDescriptor(r io.Reader, f *File) (err os.Error) {
-	defer func() {
-		if rerr, ok := recover().(os.Error); ok {
-			err = rerr
-		}
-	}()
+	defer recoverError(&err)
 	read(r, &f.CRC32)
 	read(r, &f.CompressedSize)
 	read(r, &f.UncompressedSize)
 	return
 }
 
-func readDirectoryEnd(r io.ReaderAt, size int64) (d *directoryEnd, err os.Error) {
+func readDirectoryEnd(r io.ReaderAt, size int64) (dir *directoryEnd, err os.Error) {
 	// look for directoryEndSignature in the last 1k, then in the last 65k
 	var b []byte
 	for i, bLen := range []int64{1024, 65 * 1024} {
@@ -274,14 +254,9 @@ func readDirectoryEnd(r io.ReaderAt, size int64) (d *directoryEnd, err os.Error)
 	}
 
 	// read header into struct
-	defer func() {
-		if rerr, ok := recover().(os.Error); ok {
-			err = rerr
-			d = nil
-		}
-	}()
+	defer recoverError(&err)
 	br := bytes.NewBuffer(b[4:]) // skip over signature
-	d = new(directoryEnd)
+	d := new(directoryEnd)
 	read(br, &d.diskNbr)
 	read(br, &d.dirDiskNbr)
 	read(br, &d.dirRecordsThisDisk)

src/pkg/archive/zip/struct.go

@@ -1,5 +1,24 @@
+// 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: http://www.pkware.com/documents/casestudies/APPNOTE.TXT
+
+This package does not support ZIP64 or disk spanning.
+*/
 package zip
 
+import "os"
+
+// Compression methods.
+const (
+	Store   uint16 = 0
+	Deflate uint16 = 8
+)
+
 const (
 	fileHeaderSignature      = 0x04034b50
 	directoryHeaderSignature = 0x02014b50
@@ -32,3 +51,13 @@ type directoryEnd struct {
 	commentLen         uint16
 	comment            string
 }
+
+func recoverError(err *os.Error) {
+	if e := recover(); e != nil {
+		if osErr, ok := e.(os.Error); ok {
+			*err = osErr
+			return
+		}
+		panic(e)
+	}
+}

src/pkg/archive/zip/writer.go

@@ -0,0 +1,244 @@
+// 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"
+	"compress/flate"
+	"encoding/binary"
+	"hash"
+	"hash/crc32"
+	"io"
+	"os"
+)
+
+// TODO(adg): support zip file comments
+// TODO(adg): support specifying deflate level
+
+// Writer implements a zip file writer.
+type Writer struct {
+	*countWriter
+	dir    []*header
+	last   *fileWriter
+	closed bool
+}
+
+type header struct {
+	*FileHeader
+	offset uint32
+}
+
+// NewWriter returns a new Writer writing a zip file to w.
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{countWriter: &countWriter{w: bufio.NewWriter(w)}}
+}
+
+// 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() (err os.Error) {
+	if w.last != nil && !w.last.closed {
+		if err = w.last.close(); err != nil {
+			return
+		}
+		w.last = nil
+	}
+	if w.closed {
+		return os.NewError("zip: writer closed twice")
+	}
+	w.closed = true
+
+	defer recoverError(&err)
+
+	// write central directory
+	start := w.count
+	for _, h := range w.dir {
+		write(w, uint32(directoryHeaderSignature))
+		write(w, h.CreatorVersion)
+		write(w, h.ReaderVersion)
+		write(w, h.Flags)
+		write(w, h.Method)
+		write(w, h.ModifiedTime)
+		write(w, h.ModifiedDate)
+		write(w, h.CRC32)
+		write(w, h.CompressedSize)
+		write(w, h.UncompressedSize)
+		write(w, uint16(len(h.Name)))
+		write(w, uint16(len(h.Extra)))
+		write(w, uint16(len(h.Comment)))
+		write(w, uint16(0)) // disk number start
+		write(w, uint16(0)) // internal file attributes
+		write(w, uint32(0)) // external file attributes
+		write(w, h.offset)
+		writeBytes(w, []byte(h.Name))
+		writeBytes(w, h.Extra)
+		writeBytes(w, []byte(h.Comment))
+	}
+	end := w.count
+
+	// write end record
+	write(w, uint32(directoryEndSignature))
+	write(w, uint16(0))          // disk number
+	write(w, uint16(0))          // disk number where directory starts
+	write(w, uint16(len(w.dir))) // number of entries this disk
+	write(w, uint16(len(w.dir))) // number of entries total
+	write(w, uint32(end-start))  // size of directory
+	write(w, uint32(start))      // start of directory
+	write(w, uint16(0))          // size of comment
+
+	return w.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 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, os.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, os.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 = 0x14
+	fh.ReaderVersion = 0x14
+
+	fw := &fileWriter{
+		zipw:      w,
+		compCount: &countWriter{w: w},
+		crc32:     crc32.NewIEEE(),
+	}
+	switch fh.Method {
+	case Store:
+		fw.comp = nopCloser{fw.compCount}
+	case Deflate:
+		fw.comp = flate.NewWriter(fw.compCount, 5)
+	default:
+		return nil, UnsupportedMethod
+	}
+	fw.rawCount = &countWriter{w: fw.comp}
+
+	h := &header{
+		FileHeader: fh,
+		offset:     uint32(w.count),
+	}
+	w.dir = append(w.dir, h)
+	fw.header = h
+
+	if err := writeHeader(w, fh); err != nil {
+		return nil, err
+	}
+
+	w.last = fw
+	return fw, nil
+}
+
+func writeHeader(w io.Writer, h *FileHeader) (err os.Error) {
+	defer recoverError(&err)
+	write(w, uint32(fileHeaderSignature))
+	write(w, h.ReaderVersion)
+	write(w, h.Flags)
+	write(w, h.Method)
+	write(w, h.ModifiedTime)
+	write(w, h.ModifiedDate)
+	write(w, h.CRC32)
+	write(w, h.CompressedSize)
+	write(w, h.UncompressedSize)
+	write(w, uint16(len(h.Name)))
+	write(w, uint16(len(h.Extra)))
+	writeBytes(w, []byte(h.Name))
+	writeBytes(w, h.Extra)
+	return nil
+}
+
+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, os.Error) {
+	if w.closed {
+		return 0, os.NewError("zip: write to closed file")
+	}
+	w.crc32.Write(p)
+	return w.rawCount.Write(p)
+}
+
+func (w *fileWriter) close() (err os.Error) {
+	if w.closed {
+		return os.NewError("zip: file closed twice")
+	}
+	w.closed = true
+	if err = w.comp.Close(); err != nil {
+		return
+	}
+
+	// update FileHeader
+	fh := w.header.FileHeader
+	fh.CRC32 = w.crc32.Sum32()
+	fh.CompressedSize = uint32(w.compCount.count)
+	fh.UncompressedSize = uint32(w.rawCount.count)
+
+	// write data descriptor
+	defer recoverError(&err)
+	write(w.zipw, fh.CRC32)
+	write(w.zipw, fh.CompressedSize)
+	write(w.zipw, fh.UncompressedSize)
+
+	return nil
+}
+
+type countWriter struct {
+	w     io.Writer
+	count int64
+}
+
+func (w *countWriter) Write(p []byte) (int, os.Error) {
+	n, err := w.w.Write(p)
+	w.count += int64(n)
+	return n, err
+}
+
+type nopCloser struct {
+	io.Writer
+}
+
+func (w nopCloser) Close() os.Error {
+	return nil
+}
+
+func write(w io.Writer, data interface{}) {
+	if err := binary.Write(w, binary.LittleEndian, data); err != nil {
+		panic(err)
+	}
+}
+
+func writeBytes(w io.Writer, b []byte) {
+	n, err := w.Write(b)
+	if err != nil {
+		panic(err)
+	}
+	if n != len(b) {
+		panic(io.ErrShortWrite)
+	}
+}

src/pkg/archive/zip/writer_test.go

@@ -0,0 +1,73 @@
+// 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 (
+	"bytes"
+	"io/ioutil"
+	"rand"
+	"testing"
+)
+
+// TODO(adg): a more sophisticated test suite
+
+const testString = "Rabbits, guinea pigs, gophers, marsupial rats, and quolls."
+
+func TestWriter(t *testing.T) {
+	largeData := make([]byte, 1<<17)
+	for i := range largeData {
+		largeData[i] = byte(rand.Int())
+	}
+
+	// write a zip file
+	buf := new(bytes.Buffer)
+	w := NewWriter(buf)
+	testCreate(t, w, "foo", []byte(testString), Store)
+	testCreate(t, w, "bar", largeData, Deflate)
+	if err := w.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// read it back
+	r, err := NewReader(sliceReaderAt(buf.Bytes()), int64(buf.Len()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	testReadFile(t, r.File[0], []byte(testString))
+	testReadFile(t, r.File[1], largeData)
+}
+
+func testCreate(t *testing.T, w *Writer, name string, data []byte, method uint16) {
+	header := &FileHeader{
+		Name:   name,
+		Method: method,
+	}
+	f, err := w.CreateHeader(header)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = f.Write(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func testReadFile(t *testing.T, f *File, data []byte) {
+	rc, err := f.Open()
+	if err != nil {
+		t.Fatal("opening:", err)
+	}
+	b, err := ioutil.ReadAll(rc)
+	if err != nil {
+		t.Fatal("reading:", err)
+	}
+	err = rc.Close()
+	if err != nil {
+		t.Fatal("closing:", err)
+	}
+	if !bytes.Equal(b, data) {
+		t.Errorf("File contents %q, want %q", b, data)
+	}
+}