zip

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) SetComment(comment string) error
  • func (w *Writer) SetOffset(n int64)

Examples

• Reader
• Writer
• Writer.RegisterCompressor

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")
)

Functions

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.

Types

type Compressor

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

A Compressor returns a new compressing writer, writing to w. The 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 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 a ReadCloser that provides access to the File's contents. Multiple files may be read concurrently.

type FileHeader

type FileHeader struct {
	Name string

	Comment string

	NonUTF8 bool

	CreatorVersion uint16
	ReaderVersion  uint16
	Flags          uint16

	Method uint16

	Modified     time.Time
	ModifiedTime uint16
	ModifiedDate uint16

	CRC32              uint32
	CompressedSize     uint32
	UncompressedSize   uint32
	CompressedSize64   uint64
	UncompressedSize64 uint64
	Extra              []byte
	ExternalAttrs      uint32
}

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. If compression is desired, callers should set the FileHeader.Method field; it is unset by default.

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 using the legacy ModifiedDate and ModifiedTime fields.

Deprecated: Use Modified instead.

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 Modified, ModifiedTime, and ModifiedDate fields to the given time in UTC.

Deprecated: Use Modified instead.

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
}

Example

package main

import (
	"archive/zip"
	"fmt"
	"io"
	"log"
	"os"
)

func main() {
	// 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 {
	// contains filtered or unexported fields
}

Writer implements a zip file writer.

Example

package main

import (
	"archive/zip"
	"bytes"
	"log"
)

func main() {
	// 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 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 a Writer to which the file contents should be written. The file contents will be compressed using the Deflate method. 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. To create a directory instead of a file, add a trailing slash to the name. 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 archive using the provided FileHeader for the file metadata. Writer takes ownership of fh and may mutate its fields. The caller must not modify fh after calling CreateHeader.

This 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 (*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.

Example

package main

import (
	"archive/zip"
	"bytes"
	"compress/flate"
	"io"
)

func main() {
	// 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) SetComment

func (w *Writer) SetComment(comment string) error

SetComment sets the end-of-central-directory comment field. It can only be called before Close.

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.