zip

package module
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 Go to latest Published: May 31, 2024 License: BSD-3-Clause Imports: 18 Imported by: 0

README

Go zip library

This project is based on the archive/zip Go standard library. It adds a new Updater struct that allows appending new files to the existing zip archive without having to decompress the whole file, and allows overwriting of files already stored in the zip archive.

Usage

import "github.com/meteologica/zip"

// Open an existing test.zip archive with read/write only mode for Updater.
f, err := os.OpenFile("test.zip", os.O_RDWR, 0)
handleErr(err)
zu, err := zip.NewUpdater(f)
handleErr(err)
defer zu.Close()

// Updater supports modify the zip comment.
err = zu.SetComment("Test update zip archive")
handleErr(err)

// Append a new file into existing archive.
// The Append method will create a new io.Writer.
w, err := zu.Append("example.txt")
handleErr(err)
// Write data into writer.
_, err = w.Write([]byte("hello world"))
handleErr(err)

Example test code: updater_example_test.go.

License

BSD 3-Clause

The zip library is based on Go standard library.

Documentation

Overview

Package zip provides support for reading and writing ZIP archives.

See the ZIP specification for details.

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

Examples

Constants

View Source 
const (
	Store   uint16 = 0 // no compression
	Deflate uint16 = 8 // DEFLATE compressed
)

Compression methods.

Variables

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

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 AppendMode added in v0.3.0 

type AppendMode int

AppendMode specifies the way to append new file to existing zip archive. 

const (
	// ZIP_APPEND_OVERWRITE removes the existing file data and append the new
	// data to the end of the zip archive.
	APPEND_MODE_OVERWRITE AppendMode = iota

	// ZIP_APPEND_KEEP_ORIGINAL will keep the original file data and only
	// write the new file data at the end of the existing zip archive file.
	// This mode will keep multiple file with same name into one archive file.
	APPEND_MODE_KEEP_ORIGINAL
)

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 Directory 

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

func (*Directory) HeaderOffset 

func (d *Directory) HeaderOffset() int64

type File 

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

A File is a single file in a ZIP archive. The file information is in the embedded FileHeader. The file content can be accessed by calling File.Open.

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 File.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.

func (*File) OpenRaw 

func (f *File) OpenRaw() (io.Reader, error)

OpenRaw returns a Reader that provides access to the File's contents without decompression.

type FileHeader 

type FileHeader struct {
	// Name is the name of the file.
	//
	// It must be a relative path, not start with a drive letter (such as "C:"),
	// and must use forward slashes instead of back slashes. A trailing slash
	// indicates that this file is a directory and should have no data.
	Name string

	// Comment is any arbitrary user-defined string shorter than 64KiB.
	Comment string

	// NonUTF8 indicates that Name and Comment are not encoded in UTF-8.
	//
	// By specification, the only other encoding permitted should be CP-437,
	// but historically many ZIP readers interpret Name and Comment as whatever
	// the system's local character encoding happens to be.
	//
	// This flag should only be set if the user intends to encode a non-portable
	// ZIP file for a specific localized region. Otherwise, the Writer
	// automatically sets the ZIP format's UTF-8 flag for valid UTF-8 strings.
	NonUTF8 bool

	CreatorVersion uint16
	ReaderVersion  uint16
	Flags          uint16

	// Method is the compression method. If zero, Store is used.
	Method uint16

	// Modified is the modified time of the file.
	//
	// When reading, an extended timestamp is preferred over the legacy MS-DOS
	// date field, and the offset between the times is used as the timezone.
	// If only the MS-DOS date is present, the timezone is assumed to be UTC.
	//
	// When writing, an extended timestamp (which is timezone-agnostic) is
	// always emitted. The legacy MS-DOS date field is encoded according to the
	// location of the Modified time.
	Modified time.Time

	// ModifiedTime is an MS-DOS-encoded time.
	//
	// Deprecated: Use Modified instead.
	ModifiedTime uint16

	// ModifiedDate is an MS-DOS-encoded date.
	//
	// Deprecated: Use Modified instead.
	ModifiedDate uint16

	// CRC32 is the CRC32 checksum of the file content.
	CRC32 uint32

	// CompressedSize is the compressed size of the file in bytes.
	// If either the uncompressed or compressed size of the file
	// does not fit in 32 bits, CompressedSize is set to ^uint32(0).
	//
	// Deprecated: Use CompressedSize64 instead.
	CompressedSize uint32

	// UncompressedSize is the compressed size of the file in bytes.
	// If either the uncompressed or compressed size of the file
	// does not fit in 32 bits, CompressedSize is set to ^uint32(0).
	//
	// Deprecated: Use UncompressedSize64 instead.
	UncompressedSize uint32

	// CompressedSize64 is the compressed size of the file in bytes.
	CompressedSize64 uint64

	// UncompressedSize64 is the uncompressed size of the file in bytes.
	UncompressedSize64 uint64

	Extra         []byte
	ExternalAttrs uint32 // Meaning depends on CreatorVersion
}

FileHeader describes a file within a ZIP file. See the ZIP specification for details.

func FileInfoHeader 

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

FileInfoHeader creates a partially-populated FileHeader from an fs.FileInfo. Because fs.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() fs.FileInfo

FileInfo returns an fs.FileInfo for the FileHeader.

func (*FileHeader) ModTime deprecated 

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 fs.FileMode)

Mode returns the permission and mode bits for the FileHeader.

func (*FileHeader) SetModTime deprecated 

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 fs.FileMode)

SetMode changes the permission and mode bits for the FileHeader.

type ReadCloser 

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

A ReadCloser is a Reader that must be closed when no longer needed.

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
}

A Reader serves content from a ZIP archive.

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.

If any file inside the archive uses a non-local name (as defined by filepath.IsLocal) or a name containing backslashes and the GODEBUG environment variable contains `zipinsecurepath=0`, NewReader returns the reader with an ErrInsecurePath error. A future version of Go may introduce this behavior by default. Programs that want to accept non-local names can ignore the ErrInsecurePath error and use the returned reader.

func (*Reader) Open 

func (r *Reader) Open(name string) (fs.File, error)

Open opens the named file in the ZIP archive, using the semantics of fs.FS.Open: paths are always slash separated, with no leading / or ../ elements.

func (*Reader) RegisterDecompressor 

func (r *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 Updater 

type Updater struct {
	// contains filtered or unexported fields
}

Updater allows to modify & append files into an existing zip archive without decompress the whole file.

func NewUpdater 

func NewUpdater(rws io.ReadWriteSeeker) (*Updater, error)

NewUpdater returns a new Updater from io.ReadWriteSeeker, which is assumed to have the given size in bytes.

func (*Updater) Append 

func (u *Updater) Append(name string, mode AppendMode) (io.Writer, error)

Append 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.

If mode is set to APPEND_MODE_OVERWRITE, and file name already exists in the zip archive, Append will delete the existing file data and write the new file data at the end of the zip file.

If mode is set to APPEND_MODE_KEEP_ORIGINAL, the existing data won't be deleted from the zip file and Append only write the file data with the same file name at the end of the zip file.

The file's contents must be written to the io.Writer before the next call to [Append], [AppendHeader], or [Close].

func (*Updater) AppendHeader added in v0.3.0 

func (u *Updater) AppendHeader(fh *FileHeader, mode AppendMode) (io.Writer, error)

AppendHeader adds a file to the zip archive using the provided FileHeader for the file metadata to the specific offset. Writer takes ownership of fh and may mutate its fields. The caller must not modify fh after calling CreateHeader.

If the file name of the FileHeader already exists in the zip file, AppendHeader will remove the existing file data and the new file data will write at the end of the archive file.

It should be noted that the size of the newly appended file size should be larger than the size of the replaced file. Especially when using the Deflate compression method, the compressed data size should be larger than the original file data size.

func (*Updater) Close 

func (u *Updater) Close() error

func (*Updater) GetComment 

func (u *Updater) GetComment() string

func (*Updater) SetComment 

func (u *Updater) SetComment(comment string) error

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)
	}
}

Output:

func NewWriter 

func NewWriter(w io.Writer) *Writer

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

func (*Writer) AddFS added in v0.3.0 

func (w *Writer) AddFS(fsys fs.FS) error

AddFS adds the files from fs.FS to the archive. It walks the directory tree starting at the root of the filesystem adding each file to the zip using deflate while maintaining the directory structure.

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) Copy 

func (w *Writer) Copy(f *File) error

Copy copies the file f (obtained from a Reader) into w. It copies the raw form directly bypassing decompression, compression, and validation.

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 Writer.Create, Writer.CreateHeader, or Writer.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 Writer.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 Writer.Create, Writer.CreateHeader, Writer.CreateRaw, or Writer.Close.

func (*Writer) CreateRaw 

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

CreateRaw adds a file to the zip archive using the provided FileHeader and 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 Writer.Create, Writer.CreateHeader, Writer.CreateRaw, or Writer.Close.

In contrast to Writer.CreateHeader, the bytes passed to Writer are not compressed.

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.
}

Output:

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 Writer.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.

Source Files

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