flate package - compress/flate

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<nav class="go-Main-nav go-Main-nav--sticky js-mainNav" aria-label="Outline"> <div class="go-Main-navDesktop"> <div class="UnitOutline-jumpTo"> <button class="UnitOutline-jumpToInput go-ShortcutKey js-jumpToInput" aria-controls="jump-to-modal" aria-label="Open Jump to Identifier" data-shortcut="f" data-shortcut-alt="find" data-test-id="jump-to-button" data-gtmc="outline button"> Jump to ... </button> </div> <ul class="go-Tree js-tree" role="tree" aria-label="Outline"> <li> <a href="#section-documentation" data-gtmc="outline link"> Documentation </a> <ul> <li> <a href="#pkg-overview" data-gtmc="doc outline link">Overview</a> </li> <li class="DocNav-overview"> <a href="#pkg-index" data-gtmc="doc outline link"> Index </a> <ul> <li> <a href="#pkg-examples" data-gtmc="doc outline link"> Examples </a> </li> </ul> </li> <li class="DocNav-constants"> <a href="#pkg-constants" data-gtmc="doc outline link"> Constants </a> </li> <li class="DocNav-variables"> <a href="#pkg-variables" data-gtmc="doc 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ReadError" data-gtmc="doc outline link"> type ReadError </a> <ul> <li> <a href="#ReadError.Error" title="(e) Error()" data-gtmc="doc outline link"> (e) Error() </a> </li> </ul> </li> <li> <a href="#Reader" title="type Reader" data-gtmc="doc outline link"> type Reader </a> </li> <li> <a href="#Resetter" title="type Resetter" data-gtmc="doc outline link"> type Resetter </a> </li> <li> <a href="#WriteError" title="type WriteError" data-gtmc="doc outline link"> type WriteError </a> <ul> <li> <a href="#WriteError.Error" title="(e) Error()" data-gtmc="doc outline link"> (e) Error() </a> </li> </ul> </li> <li> <a href="#Writer" title="type Writer" data-gtmc="doc outline link"> type Writer </a> <ul> <li> <a href="#NewWriter" title="NewWriter(w, level)" data-gtmc="doc outline link"> NewWriter(w, level) </a> </li> <li> <a href="#NewWriterDict" title="NewWriterDict(w, level, dict)" data-gtmc="doc outline link"> NewWriterDict(w, level, dict) </a> </li> <li> <a href="#Writer.Close" title="(w) Close()" data-gtmc="doc outline link"> (w) Close() </a> </li> <li> <a href="#Writer.Flush" title="(w) Flush()" data-gtmc="doc outline link"> (w) Flush() </a> </li> <li> <a href="#Writer.Reset" title="(w) Reset(dst)" data-gtmc="doc outline link"> (w) Reset(dst) </a> </li> <li> <a href="#Writer.Write" title="(w) Write(data)" data-gtmc="doc outline link"> (w) Write(data) </a> </li> </ul> </li> </ul> </li> </ul> </li> <li> <a href="#section-sourcefiles" data-gtmc="outline link"> Source Files </a> </li> </ul> </div> <div class="go-Main-navMobile js-mainNavMobile"> <label class="go-Label"> <select class="go-Select"> <option selected disabled>Documentation</option> </select> </label> </div> </nav> <article class="go-Main-article js-mainContent"> <div class="UnitDetails" data-test-id="UnitDetails" style="display: block;"> <div class="UnitDetails-content js-unitDetailsContent" data-test-id="UnitDetails-content"> <div class="UnitDoc"> <h2 class="UnitDoc-title" id="section-documentation"> <img class="go-Icon" height="24" width="24" src="/static/shared/icon/code_gm_grey_24dp.svg" alt=""> Documentation <a class="UnitDoc-idLink" href="#section-documentation" title="Go to Documentation" aria-label="Go to Documentation">露</a> </h2> <div class="Documentation js-documentation"> <div class="Documentation-content js-docContent"> <section class="Documentation-overview"> <h3 tabindex="-1" id="pkg-overview" class="Documentation-overviewHeader">Overview <a href="#pkg-overview" title="Go to Overview" aria-label="Go to Overview">露</a></h3> <p>Package flate implements the DEFLATE compressed data format, described in <a href="https://rfc-editor.org/rfc/rfc1951.html">RFC 1951</a>. The gzip and zlib packages implement access to DEFLATE-based file formats. </p> <details tabindex="-1" id="example-package-Dictionary" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example (Dictionary) <a href="#example-package-Dictionary" title="Go to Example (Dictionary)" aria-label="Go to Example (Dictionary)">露</a></summary> <div class="Documentation-exampleDetailsBody"> <p>A preset dictionary can be used to improve the compression ratio. The downside to using a dictionary is that the compressor and decompressor must agree in advance what dictionary to use. </p> <pre class="Documentation-exampleCode"> package main import ( "bytes" "compress/flate" "fmt" "io" "log" "os" "strings" ) 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.DefaultCompression, []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) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">Decompressed output using the dictionary: <?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> Substrings matched by the dictionary are marked with #: ##################### ###### ############title###########The Go Programming Language"/# ############authors###########Alan Donovan and Brian Kernighan"/# ############published###########2015-10-26"/# ############isbn###########978-0134190440"/# ######...</##### </##### </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> <details tabindex="-1" id="example-package-Reset" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example (Reset) <a href="#example-package-Reset" title="Go to Example (Reset)" aria-label="Go to Example (Reset)">露</a></summary> <div class="Documentation-exampleDetailsBody"> <p>In performance critical applications, Reset can be used to discard the current compressor or decompressor state and reinitialize them quickly by taking advantage of previously allocated memory. </p> <pre class="Documentation-exampleCode"> package main import ( "bytes" "compress/flate" "io" "log" "os" "strings" ) 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) } } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">Don't communicate by sharing memory, share memory by communicating. Concurrency is not parallelism. The bigger the interface, the weaker the abstraction. Documentation is for users. </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> <details tabindex="-1" id="example-package-Synchronization" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example (Synchronization) <a href="#example-package-Synchronization" title="Go to Example (Synchronization)" aria-label="Go to Example (Synchronization)">露</a></summary> <div class="Documentation-exampleDetailsBody"> <p>DEFLATE is suitable for transmitting compressed data across the network. </p> <pre class="Documentation-exampleCode"> package main import ( "compress/flate" "fmt" "io" "log" "strings" "sync" ) 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() 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) } }() } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">Received 1 bytes: A Received 4 bytes: long Received 4 bytes: time Received 3 bytes: ago Received 2 bytes: in Received 1 bytes: a Received 6 bytes: galaxy Received 4 bytes: far, Received 3 bytes: far Received 7 bytes: away... </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </section><section class="Documentation-index"> <h3 id="pkg-index" class="Documentation-indexHeader">Index <a href="#pkg-index" title="Go to Index" aria-label="Go to Index">露</a></h3> <ul class="Documentation-indexList"> <li class="Documentation-indexConstants"><a href="#pkg-constants">Constants</a></li> <li class="Documentation-indexFunction"> <a href="#NewReader">func NewReader(r io.Reader) io.ReadCloser</a></li> <li class="Documentation-indexFunction"> <a href="#NewReaderDict">func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser</a></li> <li class="Documentation-indexType"> <a href="#CorruptInputError">type CorruptInputError</a></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#CorruptInputError.Error">func (e CorruptInputError) Error() string</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#InternalError">type InternalError</a></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#InternalError.Error">func (e InternalError) Error() string</a></li> </ul></li> <li class="Documentation-indexType"> <a class="js-deprecatedTagLink" href="#ReadError">type ReadError</a><span class="Documentation-indexDeprecated Documentation-deprecatedTag">deprecated</span></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#ReadError.Error">func (e *ReadError) Error() string</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#Reader">type Reader</a></li> <li class="Documentation-indexType"> <a href="#Resetter">type Resetter</a></li> <li class="Documentation-indexType"> <a class="js-deprecatedTagLink" href="#WriteError">type WriteError</a><span class="Documentation-indexDeprecated Documentation-deprecatedTag">deprecated</span></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#WriteError.Error">func (e *WriteError) Error() string</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#Writer">type Writer</a></li> <li><ul class="Documentation-indexTypeFunctions"> <li> <a href="#NewWriter">func NewWriter(w io.Writer, level int) (*Writer, error)</a></li> <li> <a href="#NewWriterDict">func NewWriterDict(w io.Writer, level int, dict []byte) (*Writer, error)</a></li> </ul></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#Writer.Close">func (w *Writer) Close() error</a></li> <li> <a href="#Writer.Flush">func (w *Writer) Flush() error</a></li> <li> <a href="#Writer.Reset">func (w *Writer) Reset(dst io.Writer)</a></li> <li> <a href="#Writer.Write">func (w *Writer) Write(data []byte) (n int, err error)</a></li> </ul></li> </ul> </section><section class="Documentation-examples"> <h4 tabindex="-1" id="pkg-examples" class="Documentation-examplesHeader">Examples <a class="Documentation-idLink" href="#pkg-examples" title="Go to Examples" aria-label="Go to Examples">露</a></h4> <ul class="Documentation-examplesList"> <li><a href="#example-package-Dictionary" class="js-exampleHref">Package (Dictionary)</a></li> <li><a href="#example-package-Reset" class="js-exampleHref">Package (Reset)</a></li> <li><a href="#example-package-Synchronization" class="js-exampleHref">Package (Synchronization)</a></li> </ul> </section><h3 tabindex="-1" id="pkg-constants" class="Documentation-constantsHeader">Constants <a href="#pkg-constants" title="Go to Constants" aria-label="Go to Constants">露</a></h3> <section class="Documentation-constants"> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=14">View Source</a></span> <pre>const ( <span id="NoCompression" data-kind="constant"> NoCompression = 0 </span><span id="BestSpeed" data-kind="constant"> BestSpeed = 1 </span><span id="BestCompression" data-kind="constant"> BestCompression = 9 </span><span id="DefaultCompression" data-kind="constant"> DefaultCompression = -1 </span> <span id="HuffmanOnly" data-kind="constant"> <span class="comment">// HuffmanOnly disables Lempel-Ziv match searching and only performs Huffman</span> </span> <span class="comment">// entropy encoding. This mode is useful in compressing data that has</span> <span class="comment">// already been compressed with an LZ style algorithm (e.g. Snappy or LZ4)</span> <span class="comment">// that lacks an entropy encoder. Compression gains are achieved when</span> <span class="comment">// certain bytes in the input stream occur more frequently than others.</span> <span class="comment">//</span> <span class="comment">// Note that HuffmanOnly produces a compressed output that is</span> <span class="comment">// <a href="https://rfc-editor.org/rfc/rfc1951.html">RFC 1951</a> compliant. That is, any valid DEFLATE decompressor will</span> <span class="comment">// continue to be able to decompress this output.</span> HuffmanOnly = -2 )</pre> </div> </section> <h3 tabindex="-1" id="pkg-variables" class="Documentation-variablesHeader">Variables <a href="#pkg-variables" title="Go to Variables" aria-label="Go to Variables">露</a></h3> <section class="Documentation-variables"><p class="Documentation-empty">This section is empty.</p></section> <h3 tabindex="-1" id="pkg-functions" class="Documentation-functionsHeader">Functions <a href="#pkg-functions" title="Go to Functions" aria-label="Go to Functions">露</a></h3> <section class="Documentation-functions"><div class="Documentation-function"> <h4 tabindex="-1" id="NewReader" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=807">NewReader</a> <a class="Documentation-idLink" href="#NewReader" title="Go to NewReader" aria-label="Go to NewReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func NewReader(r <a href="/io">io</a>.<a href="/io#Reader">Reader</a>) <a href="/io">io</a>.<a href="/io#ReadCloser">ReadCloser</a></pre> </div> <p>NewReader returns a new ReadCloser that can be used to read the uncompressed version of r. If r does not also implement <a href="/io#ByteReader">io.ByteReader</a>, the decompressor may read more data than necessary from r. The reader returns <a href="/io#EOF">io.EOF</a> after the final block in the DEFLATE stream has been encountered. Any trailing data after the final block is ignored. </p><p>The <a href="/io#ReadCloser">io.ReadCloser</a> returned by NewReader also implements <a href="#Resetter">Resetter</a>. </p> </div><div class="Documentation-function"> <h4 tabindex="-1" id="NewReaderDict" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=826">NewReaderDict</a> <a class="Documentation-idLink" href="#NewReaderDict" title="Go to NewReaderDict" aria-label="Go to NewReaderDict">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func NewReaderDict(r <a href="/io">io</a>.<a href="/io#Reader">Reader</a>, dict []<a href="/builtin#byte">byte</a>) <a href="/io">io</a>.<a href="/io#ReadCloser">ReadCloser</a></pre> </div> <p>NewReaderDict is like <a href="#NewReader">NewReader</a> but initializes the reader with a preset dictionary. The returned <a href="#Reader">Reader</a> behaves as if the uncompressed data stream started with the given dictionary, which has already been read. NewReaderDict is typically used to read data compressed by NewWriterDict. </p><p>The ReadCloser returned by NewReaderDict also implements <a href="#Resetter">Resetter</a>. </p> </div></section> <h3 tabindex="-1" id="pkg-types" class="Documentation-typesHeader">Types <a href="#pkg-types" title="Go to Types" aria-label="Go to Types">露</a></h3> <section class="Documentation-types"><div class="Documentation-type"> <h4 tabindex="-1" id="CorruptInputError" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=33">CorruptInputError</a> <a class="Documentation-idLink" href="#CorruptInputError" title="Go to CorruptInputError" aria-label="Go to CorruptInputError">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type CorruptInputError <a href="/builtin#int64">int64</a></pre> </div> <p>A CorruptInputError reports the presence of corrupt input at a given offset. </p> <div class="Documentation-typeMethod"> <h4 tabindex="-1" id="CorruptInputError.Error" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (CorruptInputError) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=35">Error</a> <a class="Documentation-idLink" href="#CorruptInputError.Error" title="Go to CorruptInputError.Error" aria-label="Go to CorruptInputError.Error">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (e <a href="#CorruptInputError">CorruptInputError</a>) Error() <a href="/builtin#string">string</a></pre> </div> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="InternalError" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=40">InternalError</a> <a class="Documentation-idLink" href="#InternalError" title="Go to InternalError" aria-label="Go to InternalError">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type InternalError <a href="/builtin#string">string</a></pre> </div> <p>An InternalError reports an error in the flate code itself. </p> <div class="Documentation-typeMethod"> <h4 tabindex="-1" id="InternalError.Error" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (InternalError) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=42">Error</a> <a class="Documentation-idLink" href="#InternalError.Error" title="Go to InternalError.Error" aria-label="Go to InternalError.Error">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (e <a href="#InternalError">InternalError</a>) Error() <a href="/builtin#string">string</a></pre> </div> </div> </div><div class="Documentation-type"> <details class="Documentation-deprecatedDetails js-deprecatedDetails"> <summary> <h4 tabindex="-1" id="ReadError" data-kind="type" class="Documentation-typeHeader"> <span class="Documentation-deprecatedTitle"> type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=47">ReadError</a> <span class="Documentation-deprecatedTag">deprecated</span> <span class="Documentation-deprecatedBody"></span> </span> <span class="Documentation-sinceVersion"> </span> </h4> </summary> <div class="go-Message go-Message--warning Documentation-deprecatedItemBody"> <div class="Documentation-declaration"> <pre>type ReadError struct { <span id="ReadError.Offset" data-kind="field"> Offset <a href="/builtin#int64">int64</a> <span class="comment">// byte offset where error occurred</span> </span><span id="ReadError.Err" data-kind="field"> Err <a href="/builtin#error">error</a> <span class="comment">// error returned by underlying Read</span> </span>}</pre> </div> <p>A ReadError reports an error encountered while reading input. </p><p>Deprecated: No longer returned. </p> <div class="Documentation-typeMethod"> <h4 tabindex="-1" id="ReadError.Error" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*ReadError) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=52">Error</a> <a class="Documentation-idLink" href="#ReadError.Error" title="Go to ReadError.Error" aria-label="Go to ReadError.Error">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (e *<a href="#ReadError">ReadError</a>) Error() <a href="/builtin#string">string</a></pre> </div> </div> </div> </details> </div><div class="Documentation-type"> <h4 tabindex="-1" id="Reader" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=261">Reader</a> <a class="Documentation-idLink" href="#Reader" title="Go to Reader" aria-label="Go to Reader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type Reader interface { <a href="/io">io</a>.<a href="/io#Reader">Reader</a> <a href="/io">io</a>.<a href="/io#ByteReader">ByteReader</a> }</pre> </div> <p>The actual read interface needed by <a href="#NewReader">NewReader</a>. If the passed in io.Reader does not also have ReadByte, the <a href="#NewReader">NewReader</a> will introduce its own buffering. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="Resetter" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=71">Resetter</a> <a class="Documentation-idLink" href="#Resetter" title="Go to Resetter" aria-label="Go to Resetter">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.4</span> </span> </h4> <div class="Documentation-declaration"> <pre>type Resetter interface { <span id="Resetter.Reset" data-kind="method"> <span class="comment">// Reset discards any buffered data and resets the Resetter as if it was</span> </span> <span class="comment">// newly initialized with the given reader.</span> Reset(r <a href="/io">io</a>.<a href="/io#Reader">Reader</a>, dict []<a href="/builtin#byte">byte</a>) <a href="/builtin#error">error</a> }</pre> </div> <p>Resetter resets a ReadCloser returned by <a href="#NewReader">NewReader</a> or <a href="#NewReaderDict">NewReaderDict</a> to switch to a new underlying <a href="#Reader">Reader</a>. This permits reusing a ReadCloser instead of allocating a new one. </p> </div><div class="Documentation-type"> <details class="Documentation-deprecatedDetails js-deprecatedDetails"> <summary> <h4 tabindex="-1" id="WriteError" data-kind="type" class="Documentation-typeHeader"> <span class="Documentation-deprecatedTitle"> type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=59">WriteError</a> <span class="Documentation-deprecatedTag">deprecated</span> <span class="Documentation-deprecatedBody"></span> </span> <span class="Documentation-sinceVersion"> </span> </h4> </summary> <div class="go-Message go-Message--warning Documentation-deprecatedItemBody"> <div class="Documentation-declaration"> <pre>type WriteError struct { <span id="WriteError.Offset" data-kind="field"> Offset <a href="/builtin#int64">int64</a> <span class="comment">// byte offset where error occurred</span> </span><span id="WriteError.Err" data-kind="field"> Err <a href="/builtin#error">error</a> <span class="comment">// error returned by underlying Write</span> </span>}</pre> </div> <p>A WriteError reports an error encountered while writing output. </p><p>Deprecated: No longer returned. </p> <div class="Documentation-typeMethod"> <h4 tabindex="-1" id="WriteError.Error" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*WriteError) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go;l=64">Error</a> <a class="Documentation-idLink" href="#WriteError.Error" title="Go to WriteError.Error" aria-label="Go to WriteError.Error">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (e *<a href="#WriteError">WriteError</a>) Error() <a href="/builtin#string">string</a></pre> </div> </div> </div> </details> </div><div class="Documentation-type"> <h4 tabindex="-1" id="Writer" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=699">Writer</a> <a class="Documentation-idLink" href="#Writer" title="Go to Writer" aria-label="Go to Writer">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type Writer struct { <span class="comment">// contains filtered or unexported fields</span> }</pre> </div> <p>A Writer takes data written to it and writes the compressed form of that data to an underlying writer (see <a href="#NewWriter">NewWriter</a>). </p> <div class="Documentation-typeFunc"> <h4 tabindex="-1" id="NewWriter" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=662">NewWriter</a> <a class="Documentation-idLink" href="#NewWriter" title="Go to NewWriter" aria-label="Go to NewWriter">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func NewWriter(w <a href="/io">io</a>.<a href="/io#Writer">Writer</a>, level <a href="/builtin#int">int</a>) (*<a href="#Writer">Writer</a>, <a href="/builtin#error">error</a>)</pre> </div> <p>NewWriter returns a new <a href="#Writer">Writer</a> compressing data at the given level. Following zlib, levels range from 1 (<a href="#BestSpeed">BestSpeed</a>) to 9 (<a href="#BestCompression">BestCompression</a>); higher levels typically run slower but compress more. Level 0 (<a href="#NoCompression">NoCompression</a>) does not attempt any compression; it only adds the necessary DEFLATE framing. Level -1 (<a href="#DefaultCompression">DefaultCompression</a>) uses the default compression level. Level -2 (<a href="#HuffmanOnly">HuffmanOnly</a>) will use Huffman compression only, giving a very fast compression for all types of input, but sacrificing considerable compression efficiency. </p><p>If level is in the range [-2, 9] then the error returned will be nil. Otherwise the error returned will be non-nil. </p> </div><div class="Documentation-typeFunc"> <h4 tabindex="-1" id="NewWriterDict" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=676">NewWriterDict</a> <a class="Documentation-idLink" href="#NewWriterDict" title="Go to NewWriterDict" aria-label="Go to NewWriterDict">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func NewWriterDict(w <a href="/io">io</a>.<a href="/io#Writer">Writer</a>, level <a href="/builtin#int">int</a>, dict []<a href="/builtin#byte">byte</a>) (*<a href="#Writer">Writer</a>, <a href="/builtin#error">error</a>)</pre> </div> <p>NewWriterDict is like <a href="#NewWriter">NewWriter</a> but initializes the new <a href="#Writer">Writer</a> with a preset dictionary. The returned <a href="#Writer">Writer</a> behaves as if the dictionary had been written to it without producing any compressed output. The compressed data written to w can only be decompressed by a <a href="#Reader">Reader</a> initialized with the same dictionary. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="Writer.Close" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*Writer) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=726">Close</a> <a class="Documentation-idLink" href="#Writer.Close" title="Go to Writer.Close" aria-label="Go to Writer.Close">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (w *<a href="#Writer">Writer</a>) Close() <a href="/builtin#error">error</a></pre> </div> <p>Close flushes and closes the writer. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="Writer.Flush" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*Writer) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=719">Flush</a> <a class="Documentation-idLink" href="#Writer.Flush" title="Go to Writer.Flush" aria-label="Go to Writer.Flush">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (w *<a href="#Writer">Writer</a>) Flush() <a href="/builtin#error">error</a></pre> </div> <p>Flush flushes any pending 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. Calling Flush when there is no pending data still causes the <a href="#Writer">Writer</a> to emit a sync marker of at least 4 bytes. If the underlying writer returns an error, Flush returns that error. </p><p>In the terminology of the zlib library, Flush is equivalent to Z_SYNC_FLUSH. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="Writer.Reset" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*Writer) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=733">Reset</a> <a class="Documentation-idLink" href="#Writer.Reset" title="Go to Writer.Reset" aria-label="Go to Writer.Reset">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.2</span> </span> </h4> <div class="Documentation-declaration"> <pre>func (w *<a href="#Writer">Writer</a>) Reset(dst <a href="/io">io</a>.<a href="/io#Writer">Writer</a>)</pre> </div> <p>Reset discards the writer's state and makes it equivalent to the result of <a href="#NewWriter">NewWriter</a> or <a href="#NewWriterDict">NewWriterDict</a> called with dst and w's level and dictionary. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="Writer.Write" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*Writer) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go;l=706">Write</a> <a class="Documentation-idLink" href="#Writer.Write" title="Go to Writer.Write" aria-label="Go to Writer.Write">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (w *<a href="#Writer">Writer</a>) Write(data []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>Write writes data to w, which will eventually write the compressed form of data to its underlying writer. </p> </div> </div></section></div> </div> </div> <div class="UnitFiles js-unitFiles"> <h2 class="UnitFiles-title" id="section-sourcefiles"> <img class="go-Icon" height="24" width="24" src="/static/shared/icon/insert_drive_file_gm_grey_24dp.svg" alt=""> Source Files <a class="UnitFiles-idLink" href="#section-sourcefiles" title="Go to Source Files" aria-label="Go to Source Files">露</a> </h2> <div class="UnitFiles-titleLink"> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate" target="_blank" rel="noopener">View all Source files</a> </div> <div> <ul class="UnitFiles-fileList"><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflate.go" target="_blank" rel="noopener" title="deflate.go">deflate.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/deflatefast.go" target="_blank" rel="noopener" title="deflatefast.go">deflatefast.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/dict_decoder.go" target="_blank" rel="noopener" title="dict_decoder.go">dict_decoder.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/huffman_bit_writer.go" target="_blank" rel="noopener" title="huffman_bit_writer.go">huffman_bit_writer.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/huffman_code.go" target="_blank" rel="noopener" title="huffman_code.go">huffman_code.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/inflate.go" target="_blank" rel="noopener" title="inflate.go">inflate.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/compress/flate/token.go" target="_blank" rel="noopener" title="token.go">token.go</a> </li></ul> </div> </div> </div> </div> <div id="showInternal-description" hidden> Click to show internal directories. </div> <div id="hideInternal-description" hidden> Click to hide internal directories. </div> </article> <footer class="go-Main-footer"></footer> </main> 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flate package - compress/flate - Go Packages