package gzip

Import Path
	github.com/klauspost/compress/gzip (on go.dev)

Dependency Relation
	imports 9 packages, and imported by one package


Involved Source Files

	
		Package gzip implements reading and writing of gzip format compressed files,
		as specified in RFC 1952.

	    gzip.go


Code Examples

	
		package main
		
		import (
			"bytes"
			"compress/gzip"
			"fmt"
			"io"
			"log"
			"os"
			"time"
		)
		
		func main() {
			var buf bytes.Buffer
			zw := gzip.NewWriter(&buf)
		
			var files = []struct {
				name    string
				comment string
				modTime time.Time
				data    string
			}{
				{"file-1.txt", "file-header-1", time.Date(2006, time.February, 1, 3, 4, 5, 0, time.UTC), "Hello Gophers - 1"},
				{"file-2.txt", "file-header-2", time.Date(2007, time.March, 2, 4, 5, 6, 1, time.UTC), "Hello Gophers - 2"},
			}
		
			for _, file := range files {
				zw.Name = file.name
				zw.Comment = file.comment
				zw.ModTime = file.modTime
		
				if _, err := zw.Write([]byte(file.data)); err != nil {
					log.Fatal(err)
				}
		
				if err := zw.Close(); err != nil {
					log.Fatal(err)
				}
		
				zw.Reset(&buf)
			}
		
			zr, err := gzip.NewReader(&buf)
			if err != nil {
				log.Fatal(err)
			}
		
			for {
				zr.Multistream(false)
				fmt.Printf("Name: %s\nComment: %s\nModTime: %s\n\n", zr.Name, zr.Comment, zr.ModTime.UTC())
		
				if _, err := io.Copy(os.Stdout, zr); err != nil {
					log.Fatal(err)
				}
		
				fmt.Print("\n\n")
		
				err = zr.Reset(&buf)
				if err == io.EOF {
					break
				}
				if err != nil {
					log.Fatal(err)
				}
			}
		
			if err := zr.Close(); err != nil {
				log.Fatal(err)
			}
		
		}

	
		package main
		
		import (
			"bytes"
			"compress/gzip"
			"fmt"
			"io"
			"log"
			"os"
			"time"
		)
		
		func main() {
			var buf bytes.Buffer
			zw := gzip.NewWriter(&buf)
		
			// Setting the Header fields is optional.
			zw.Name = "a-new-hope.txt"
			zw.Comment = "an epic space opera by George Lucas"
			zw.ModTime = time.Date(1977, time.May, 25, 0, 0, 0, 0, time.UTC)
		
			_, err := zw.Write([]byte("A long time ago in a galaxy far, far away..."))
			if err != nil {
				log.Fatal(err)
			}
		
			if err := zw.Close(); err != nil {
				log.Fatal(err)
			}
		
			zr, err := gzip.NewReader(&buf)
			if err != nil {
				log.Fatal(err)
			}
		
			fmt.Printf("Name: %s\nComment: %s\nModTime: %s\n\n", zr.Name, zr.Comment, zr.ModTime.UTC())
		
			if _, err := io.Copy(os.Stdout, zr); err != nil {
				log.Fatal(err)
			}
		
			if err := zr.Close(); err != nil {
				log.Fatal(err)
			}
		
		}




Package-Level Type Names (total 5, in which 3 are exported)


	/* sort exporteds by:  |  */
	
		The gzip file stores a header giving metadata about the compressed file.
		That header is exposed as the fields of the Writer and Reader structs.
		
		Strings must be UTF-8 encoded and may only contain Unicode code points
		U+0001 through U+00FF, due to limitations of the GZIP file format.

		
			
				// comment

			
				// "extra data"

			
				// modification time

			
				// file name

			
				// operating system type

		
			


	
		A Reader is an io.Reader that can be read to retrieve
		uncompressed data from a gzip-format compressed file.
		
		In general, a gzip file can be a concatenation of gzip files,
		each with its own header. Reads from the Reader
		return the concatenation of the uncompressed data of each.
		Only the first header is recorded in the Reader fields.
		
		Gzip files store a length and checksum of the uncompressed data.
		The Reader will return a ErrChecksum when Read
		reaches the end of the uncompressed data if it does not
		have the expected length or checksum. Clients should treat data
		returned by Read as tentative until they receive the io.EOF
		marking the end of the data.

		
			
				// valid after NewReader or Reader.Reset

			
				// comment

			
				// "extra data"

			
				// modification time

			
				// file name

			
				// operating system type

			
		
			
				Close closes the Reader. It does not close the underlying io.Reader.
				In order for the GZIP checksum to be verified, the reader must be
				fully consumed until the io.EOF.

			
				Multistream controls whether the reader supports multistream files.
				
				If enabled (the default), the Reader expects the input to be a sequence
				of individually gzipped data streams, each with its own header and
				trailer, ending at EOF. The effect is that the concatenation of a sequence
				of gzipped files is treated as equivalent to the gzip of the concatenation
				of the sequence. This is standard behavior for gzip readers.
				
				Calling Multistream(false) disables this behavior; disabling the behavior
				can be useful when reading file formats that distinguish individual gzip
				data streams or mix gzip data streams with other data streams.
				In this mode, when the Reader reaches the end of the data stream,
				Read returns io.EOF. If the underlying reader implements io.ByteReader,
				it will be left positioned just after the gzip stream.
				To start the next stream, call z.Reset(r) followed by z.Multistream(false).
				If there is no next stream, z.Reset(r) will return io.EOF.

			
				Read implements io.Reader, reading uncompressed bytes from its underlying Reader.

			
				Reset discards the Reader z's state and makes it equivalent to the
				result of its original state from NewReader, but reading from r instead.
				This permits reusing a Reader rather than allocating a new one.

			
				WriteTo support the io.WriteTo interface for io.Copy and friends.

			
		
			*Reader : io.Closer
			*Reader : io.ReadCloser
			*Reader : io.Reader
			*Reader : io.WriterTo
		
			func NewReader(r io.Reader) (*Reader, error)


	
		A Writer is an io.WriteCloser.
		Writes to a Writer are compressed and written to w.

		
			
				// written at first call to Write, Flush, or Close

			
				// comment

			
				// "extra data"

			
				// modification time

			
				// file name

			
				// operating system type

			
		
			
				Close closes the Writer, flushing any unwritten data to the underlying
				io.Writer, but does not close the underlying io.Writer.

			
				Flush flushes any pending compressed data to the underlying writer.
				
				It is useful mainly in compressed network protocols, to ensure that
				a remote reader has enough data to reconstruct a packet. Flush does
				not return until the data has been written. If the underlying
				writer returns an error, Flush returns that error.
				
				In the terminology of the zlib library, Flush is equivalent to Z_SYNC_FLUSH.

			
				Reset discards the Writer z's state and makes it equivalent to the
				result of its original state from NewWriter or NewWriterLevel, but
				writing to w instead. This permits reusing a Writer rather than
				allocating a new one.

			
				Write writes a compressed form of p to the underlying io.Writer. The
				compressed bytes are not necessarily flushed until the Writer is closed.

			
		
			*Writer : internal/bisect.Writer
			*Writer : io.Closer
			*Writer : io.WriteCloser
			*Writer : io.Writer
			
		
			func NewWriter(w io.Writer) *Writer
			func NewWriterLevel(w io.Writer, level int) (*Writer, error)
			func NewWriterWindow(w io.Writer, windowSize int) (*Writer, error)


	


Package-Level Functions (total 5, in which 4 are exported)


	
		NewReader creates a new Reader reading the given reader.
		If r does not also implement io.ByteReader,
		the decompressor may read more data than necessary from r.
		
		It is the caller's responsibility to call Close on the Reader when done.
		
		The Reader.Header fields will be valid in the Reader returned.


	
		NewWriter returns a new Writer.
		Writes to the returned writer are compressed and written to w.
		
		It is the caller's responsibility to call Close on the WriteCloser when done.
		Writes may be buffered and not flushed until Close.
		
		Callers that wish to set the fields in Writer.Header must do so before
		the first call to Write, Flush, or Close.


	
		NewWriterLevel is like NewWriter but specifies the compression level instead
		of assuming DefaultCompression.
		
		The compression level can be DefaultCompression, NoCompression, or any
		integer value between BestSpeed and BestCompression inclusive. The error
		returned will be nil if the level is valid.


	
		NewWriterWindow returns a new Writer compressing data with a custom window size.
		windowSize must be from MinCustomWindowSize to MaxCustomWindowSize.


	


Package-Level Variables (total 3, in which 2 are exported)


	
		ErrChecksum is returned when reading GZIP data that has an invalid checksum.


	
		ErrHeader is returned when reading GZIP data that has an invalid header.


	


Package-Level Constants (total 17, in which 9 are exported)


	
		These constants are copied from the flate package, so that code that imports
		"compress/gzip" does not also have to import "compress/flate".


	
		These constants are copied from the flate package, so that code that imports
		"compress/gzip" does not also have to import "compress/flate".


	
		These constants are copied from the flate package, so that code that imports
		"compress/gzip" does not also have to import "compress/flate".


	
		These constants are copied from the flate package, so that code that imports
		"compress/gzip" does not also have to import "compress/flate".


	
		These constants are copied from the flate package, so that code that imports
		"compress/gzip" does not also have to import "compress/flate".


	
		MaxCustomWindowSize is the maximum custom window that can be sent to NewWriterWindow.


	
		MinCustomWindowSize is the minimum window size that can be sent to NewWriterWindow.


	
		These constants are copied from the flate package, so that code that imports
		"compress/gzip" does not also have to import "compress/flate".


	
		StatelessCompression will do compression but without maintaining any state
		between Write calls.
		There will be no memory kept between Write calls,
		but compression and speed will be suboptimal.
		Because of this, the size of actual Write calls will affect output size.