Package: github.com/klauspost/compress/flate

package flate Import Path github.com/klauspost/compress/flate (on go.dev) Dependency Relation imports 12 packages, and imported by 2 packages

Involved Source Files deflate.go dict_decoder.go fast_encoder.go huffman_bit_writer.go huffman_code.go huffman_sortByFreq.go huffman_sortByLiteral.go d inflate.go Package flate implements the DEFLATE compressed data format, described in RFC 1951. The gzip and zlib packages implement access to DEFLATE-based file formats. inflate_gen.go level1.go level2.go level3.go level4.go level5.go level6.go matchlen_generic.go regmask_amd64.go stateless.go token.go

Code Examples _dictionary package main import ( "bytes" "fmt" "io" "log" "os" "strings" "github.com/klauspost/compress/flate" ) func main() { // The dictionary is a string of bytes. When compressing some input data, // the compressor will attempt to substitute substrings with matches found // in the dictionary. As such, the dictionary should only contain substrings // that are expected to be found in the actual data stream. const dict = `<?xml version="1.0"?>` + `<book>` + `<data>` + `<meta name="` + `" content="` // The data to compress should (but is not required to) contain frequent // substrings that match those in the dictionary. const data = `<?xml version="1.0"?> <book> <meta name="title" content="The Go Programming Language"/> <meta name="authors" content="Alan Donovan and Brian Kernighan"/> <meta name="published" content="2015-10-26"/> <meta name="isbn" content="978-0134190440"/> <data>...</data> </book> ` var b bytes.Buffer // Compress the data using the specially crafted dictionary. zw, err := flate.NewWriterDict(&b, flate.BestCompression, []byte(dict)) if err != nil { log.Fatal(err) } if _, err := io.Copy(zw, strings.NewReader(data)); err != nil { log.Fatal(err) } if err := zw.Close(); err != nil { log.Fatal(err) } // The decompressor must use the same dictionary as the compressor. // Otherwise, the input may appear as corrupted. fmt.Println("Decompressed output using the dictionary:") zr := flate.NewReaderDict(bytes.NewReader(b.Bytes()), []byte(dict)) if _, err := io.Copy(os.Stdout, zr); err != nil { log.Fatal(err) } if err := zr.Close(); err != nil { log.Fatal(err) } fmt.Println() // Substitute all of the bytes in the dictionary with a '#' to visually // demonstrate the approximate effectiveness of using a preset dictionary. fmt.Println("Substrings matched by the dictionary are marked with #:") hashDict := []byte(dict) for i := range hashDict { hashDict[i] = '#' } zr = flate.NewReaderDict(&b, hashDict) if _, err := io.Copy(os.Stdout, zr); err != nil { log.Fatal(err) } if err := zr.Close(); err != nil { log.Fatal(err) } } _reset package main import ( "bytes" "io" "log" "os" "strings" "github.com/klauspost/compress/flate" ) func main() { proverbs := []string{ "Don't communicate by sharing memory, share memory by communicating.\n", "Concurrency is not parallelism.\n", "The bigger the interface, the weaker the abstraction.\n", "Documentation is for users.\n", } var r strings.Reader var b bytes.Buffer buf := make([]byte, 32<<10) zw, err := flate.NewWriter(nil, flate.DefaultCompression) if err != nil { log.Fatal(err) } zr := flate.NewReader(nil) for _, s := range proverbs { r.Reset(s) b.Reset() // Reset the compressor and encode from some input stream. zw.Reset(&b) if _, err := io.CopyBuffer(zw, &r, buf); err != nil { log.Fatal(err) } if err := zw.Close(); err != nil { log.Fatal(err) } // Reset the decompressor and decode to some output stream. if err := zr.(flate.Resetter).Reset(&b, nil); err != nil { log.Fatal(err) } if _, err := io.CopyBuffer(os.Stdout, zr, buf); err != nil { log.Fatal(err) } if err := zr.Close(); err != nil { log.Fatal(err) } } } _synchronization package main import ( "fmt" "io" "log" "strings" "sync" "github.com/klauspost/compress/flate" ) func main() { var wg sync.WaitGroup defer wg.Wait() // Use io.Pipe to simulate a network connection. // A real network application should take care to properly close the // underlying connection. rp, wp := io.Pipe() // Start a goroutine to act as the transmitter. wg.Add(1) go func() { defer wg.Done() defer wp.Close() zw, err := flate.NewWriter(wp, flate.BestSpeed) if err != nil { log.Fatal(err) } b := make([]byte, 256) for _, m := range strings.Fields("A long time ago in a galaxy far, far away...") { // We use a simple framing format where the first byte is the // message length, followed the message itself. b[0] = uint8(copy(b[1:], m)) if _, err := zw.Write(b[:1+len(m)]); err != nil { log.Fatal(err) } // Flush ensures that the receiver can read all data sent so far. if err := zw.Flush(); err != nil { log.Fatal(err) } } if err := zw.Close(); err != nil { log.Fatal(err) } }() // Start a goroutine to act as the receiver. wg.Add(1) go func() { defer wg.Done() zr := flate.NewReader(rp) b := make([]byte, 256) for { // Read the message length. // This is guaranteed to return for every corresponding // Flush and Close on the transmitter side. if _, err := io.ReadFull(zr, b[:1]); err != nil { if err == io.EOF { break // The transmitter closed the stream } log.Fatal(err) } // Read the message content. n := int(b[0]) if _, err := io.ReadFull(zr, b[:n]); err != nil { log.Fatal(err) } fmt.Printf("Received %d bytes: %s\n", n, b[:n]) } fmt.Println() if err := zr.Close(); err != nil { log.Fatal(err) } }() }

Package-Level Constants (total 8)

const BestCompression = 9

const BestSpeed = 1

const ConstantCompression = -2 // compatibility alias.

const DefaultCompression = -1

const HuffmanOnly = -2 HuffmanOnly disables Lempel-Ziv match searching and only performs Huffman entropy encoding. This mode is useful in compressing data that has already been compressed with an LZ style algorithm (e.g. Snappy or LZ4) that lacks an entropy encoder. Compression gains are achieved when certain bytes in the input stream occur more frequently than others. Note that HuffmanOnly produces a compressed output that is RFC 1951 compliant. That is, any valid DEFLATE decompressor will continue to be able to decompress this output.

const MaxCustomWindowSize = 32768 MaxCustomWindowSize is the maximum custom window that can be sent to NewWriterWindow.

const MinCustomWindowSize = 32 MinCustomWindowSize is the minimum window size that can be sent to NewWriterWindow.

const NoCompression = 0