Package zip

import "archive/zip"
Overview
Index
Examples
Documentation

Overview

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.

Index

Constants
Variables
func RegisterCompressor(method uint16, comp Compressor)
func RegisterDecompressor(method uint16, dcomp Decompressor)
type Compressor
type Decompressor
type File
func (f *File) DataOffset() (offset int64, err error)
func (f *File) Open() (io.ReadCloser, error)
type FileHeader
func FileInfoHeader(fi os.FileInfo) (*FileHeader, error)
func (h *FileHeader) FileInfo() os.FileInfo
func (h *FileHeader) ModTime() time.Time
func (h *FileHeader) Mode() (mode os.FileMode)
func (h *FileHeader) SetModTime(t time.Time)
func (h *FileHeader) SetMode(mode os.FileMode)
type ReadCloser
func OpenReader(name string) (*ReadCloser, error)
func (rc *ReadCloser) Close() error
type Reader
func NewReader(r io.ReaderAt, size int64) (*Reader, error)
func (z *Reader) RegisterDecompressor(method uint16, dcomp Decompressor)
type Writer
func NewWriter(w io.Writer) *Writer
func (w *Writer) Close() error
func (w *Writer) Create(name string) (io.Writer, error)
func (w *Writer) CreateHeader(fh *FileHeader) (io.Writer, error)
func (w *Writer) Flush() error
func (w *Writer) RegisterCompressor(method uint16, comp Compressor)
func (w *Writer) SetOffset(n int64)

Examples

Reader
Writer
Writer.RegisterCompressor

Documentation

Constants

const (
    Store   uint16 = 0
    Deflate uint16 = 8
)

Compression methods.

Variables

var (
    ErrFormat    = errors.New("zip: not a valid zip file")
    ErrAlgorithm = errors.New("zip: unsupported compression algorithm")
    ErrChecksum  = errors.New("zip: checksum error")
)

func RegisterCompressor

func RegisterCompressor(method uint16, comp Compressor)

RegisterCompressor registers custom compressors for a specified method ID. The common methods Store and Deflate are built in.

func RegisterDecompressor

func RegisterDecompressor(method uint16, dcomp Decompressor)

RegisterDecompressor allows custom decompressors for a specified method ID. The common methods Store and Deflate are built in.

type Compressor

type Compressor func(w io.Writer) (io.WriteCloser, error)

A Compressor returns a new compressing writer, writing to w. The io.WriteCloser's Close method must be used to flush pending data to w. The Compressor itself must be safe to invoke from multiple goroutines simultaneously, but each returned writer will be used only by one goroutine at a time.

type Decompressor

type Decompressor func(r io.Reader) io.ReadCloser

A Decompressor returns a new decompressing reader, reading from r. The io.ReadCloser's Close method must be used to release associated resources. The Decompressor itself must be safe to invoke from multiple goroutines simultaneously, but each returned reader will be used only by one goroutine at a time.

type File

type File struct {
    FileHeader
    // contains filtered or unexported fields
}

func File.DataOffset

func (f *File) DataOffset() (offset int64, err error)

DataOffset returns the offset of the file's possibly-compressed data, relative to the beginning of the zip file.

Most callers should instead use Open, which transparently decompresses data and verifies checksums.

func File.Open

func (f *File) Open() (io.ReadCloser, error)

Open returns an io.ReadCloser that provides access to the File's contents. Multiple files may be read concurrently.

type FileHeader

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
}

FileHeader describes a file within a zip file. See the zip spec for details.

func FileInfoHeader

func FileInfoHeader(fi os.FileInfo) (*FileHeader, error)

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 FileHeader.FileInfo

func (h *FileHeader) FileInfo() os.FileInfo

FileInfo returns an os.FileInfo for the FileHeader.

func FileHeader.ModTime

func (h *FileHeader) ModTime() time.Time

ModTime returns the modification time in UTC. The resolution is 2s.

func FileHeader.Mode

func (h *FileHeader) Mode() (mode os.FileMode)

Mode returns the permission and mode bits for the FileHeader.

func FileHeader.SetModTime

func (h *FileHeader) SetModTime(t time.Time)

SetModTime sets the ModifiedTime and ModifiedDate fields to the given time in UTC. The resolution is 2s.

func FileHeader.SetMode

func (h *FileHeader) SetMode(mode os.FileMode)

SetMode changes the permission and mode bits for the FileHeader.

type ReadCloser

type ReadCloser struct {
    Reader
    // contains filtered or unexported fields
}

func OpenReader

func OpenReader(name string) (*ReadCloser, error)

OpenReader will open the Zip file specified by name and return a ReadCloser.

func ReadCloser.Close

func (rc *ReadCloser) Close() error

Close closes the Zip file, rendering it unusable for I/O.

type Reader

type Reader struct {
    File    []*File
    Comment string
    // contains filtered or unexported fields
}

Code:

// Open a zip archive for reading.
r, err := zip.OpenReader("testdata/readme.zip")
if err != nil {
    log.Fatal(err)
}
defer r.Close()

// Iterate through the files in the archive,
// printing some of their contents.
for _, f := range r.File {
    fmt.Printf("Contents of %s:\n", f.Name)
    rc, err := f.Open()
    if err != nil {
        log.Fatal(err)
    }
    _, err = io.CopyN(os.Stdout, rc, 68)
    if err != nil {
        log.Fatal(err)
    }
    rc.Close()
    fmt.Println()
}

Output:

Contents of README:
This is the source code repository for the Go programming language.

func NewReader

func NewReader(r io.ReaderAt, size int64) (*Reader, error)

NewReader returns a new Reader reading from r, which is assumed to have the given size in bytes.

func Reader.RegisterDecompressor

func (z *Reader) RegisterDecompressor(method uint16, dcomp Decompressor)

RegisterDecompressor registers or overrides a custom decompressor for a specific method ID. If a decompressor for a given method is not found, Reader will default to looking up the decompressor at the package level.

type Writer

type Writer struct {

    // Comment is the central directory comment and must be set before Close is called.
    Comment string
    // contains filtered or unexported fields
}

Writer implements a zip file writer.

Code:

// Create a buffer to write our archive to.
buf := new(bytes.Buffer)

// Create a new zip archive.
w := zip.NewWriter(buf)

// Add some files to the archive.
var files = []struct {
    Name, Body string
}{
    {"readme.txt", "This archive contains some text files."},
    {"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo"},
    {"todo.txt", "Get animal handling licence.\nWrite more examples."},
}
for _, file := range files {
    f, err := w.Create(file.Name)
    if err != nil {
        log.Fatal(err)
    }
    _, err = f.Write([]byte(file.Body))
    if err != nil {
        log.Fatal(err)
    }
}

// Make sure to check the error on Close.
err := w.Close()
if err != nil {
    log.Fatal(err)
}

func NewWriter

func NewWriter(w io.Writer) *Writer

NewWriter returns a new Writer writing a zip file to w.

func Writer.Close

func (w *Writer) Close() error

Close finishes writing the zip file by writing the central directory. It does not (and cannot) close the underlying writer.

func Writer.Create

func (w *Writer) Create(name string) (io.Writer, error)

Create adds a file to the zip file using the provided name. It returns an io.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 Writer.CreateHeader

func (w *Writer) CreateHeader(fh *FileHeader) (io.Writer, error)

CreateHeader adds a file to the zip file using the provided FileHeader for the file metadata. It returns a io.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. The provided FileHeader fh must not be modified after a call to CreateHeader.

func Writer.Flush

func (w *Writer) Flush() error

Flush flushes any buffered data to the underlying writer. Calling Flush is not normally necessary; calling Close is sufficient.

func Writer.RegisterCompressor

func (w *Writer) RegisterCompressor(method uint16, comp Compressor)

RegisterCompressor registers or overrides a custom compressor for a specific method ID. If a compressor for a given method is not found, Writer will default to looking up the compressor at the package level.

Code:

// Override the default Deflate compressor with a higher compression level.

// Create a buffer to write our archive to.
buf := new(bytes.Buffer)

// Create a new zip archive.
w := zip.NewWriter(buf)

// Register a custom Deflate compressor.
w.RegisterCompressor(zip.Deflate, func(out io.Writer) (io.WriteCloser, error) {
    return flate.NewWriter(out, flate.BestCompression)
})

// Proceed to add files to w.

func Writer.SetOffset

func (w *Writer) SetOffset(n int64)

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.