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400 lines
11 KiB
Go
400 lines
11 KiB
Go
4 years ago
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package middleware
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import (
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"bufio"
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"compress/flate"
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"compress/gzip"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"net"
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"net/http"
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"strings"
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"sync"
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)
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var defaultCompressibleContentTypes = []string{
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"text/html",
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"text/css",
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"text/plain",
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"text/javascript",
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"application/javascript",
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"application/x-javascript",
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"application/json",
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"application/atom+xml",
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"application/rss+xml",
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"image/svg+xml",
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}
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// Compress is a middleware that compresses response
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// body of a given content types to a data format based
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// on Accept-Encoding request header. It uses a given
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// compression level.
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//
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// NOTE: make sure to set the Content-Type header on your response
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// otherwise this middleware will not compress the response body. For ex, in
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// your handler you should set w.Header().Set("Content-Type", http.DetectContentType(yourBody))
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// or set it manually.
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//
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// Passing a compression level of 5 is sensible value
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func Compress(level int, types ...string) func(next http.Handler) http.Handler {
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compressor := NewCompressor(level, types...)
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return compressor.Handler
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}
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// Compressor represents a set of encoding configurations.
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type Compressor struct {
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level int // The compression level.
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// The mapping of encoder names to encoder functions.
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encoders map[string]EncoderFunc
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// The mapping of pooled encoders to pools.
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pooledEncoders map[string]*sync.Pool
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// The set of content types allowed to be compressed.
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allowedTypes map[string]struct{}
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allowedWildcards map[string]struct{}
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// The list of encoders in order of decreasing precedence.
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encodingPrecedence []string
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}
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// NewCompressor creates a new Compressor that will handle encoding responses.
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//
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// The level should be one of the ones defined in the flate package.
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// The types are the content types that are allowed to be compressed.
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func NewCompressor(level int, types ...string) *Compressor {
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// If types are provided, set those as the allowed types. If none are
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// provided, use the default list.
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allowedTypes := make(map[string]struct{})
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allowedWildcards := make(map[string]struct{})
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if len(types) > 0 {
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for _, t := range types {
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if strings.Contains(strings.TrimSuffix(t, "/*"), "*") {
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panic(fmt.Sprintf("middleware/compress: Unsupported content-type wildcard pattern '%s'. Only '/*' supported", t))
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}
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if strings.HasSuffix(t, "/*") {
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allowedWildcards[strings.TrimSuffix(t, "/*")] = struct{}{}
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} else {
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allowedTypes[t] = struct{}{}
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}
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}
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} else {
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for _, t := range defaultCompressibleContentTypes {
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allowedTypes[t] = struct{}{}
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}
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}
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c := &Compressor{
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level: level,
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encoders: make(map[string]EncoderFunc),
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pooledEncoders: make(map[string]*sync.Pool),
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allowedTypes: allowedTypes,
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allowedWildcards: allowedWildcards,
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}
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// Set the default encoders. The precedence order uses the reverse
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// ordering that the encoders were added. This means adding new encoders
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// will move them to the front of the order.
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//
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// TODO:
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// lzma: Opera.
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// sdch: Chrome, Android. Gzip output + dictionary header.
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// br: Brotli, see https://github.com/go-chi/chi/pull/326
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// HTTP 1.1 "deflate" (RFC 2616) stands for DEFLATE data (RFC 1951)
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// wrapped with zlib (RFC 1950). The zlib wrapper uses Adler-32
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// checksum compared to CRC-32 used in "gzip" and thus is faster.
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//
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// But.. some old browsers (MSIE, Safari 5.1) incorrectly expect
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// raw DEFLATE data only, without the mentioned zlib wrapper.
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// Because of this major confusion, most modern browsers try it
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// both ways, first looking for zlib headers.
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// Quote by Mark Adler: http://stackoverflow.com/a/9186091/385548
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//
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// The list of browsers having problems is quite big, see:
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// http://zoompf.com/blog/2012/02/lose-the-wait-http-compression
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// https://web.archive.org/web/20120321182910/http://www.vervestudios.co/projects/compression-tests/results
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//
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// That's why we prefer gzip over deflate. It's just more reliable
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// and not significantly slower than gzip.
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c.SetEncoder("deflate", encoderDeflate)
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// TODO: Exception for old MSIE browsers that can't handle non-HTML?
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// https://zoompf.com/blog/2012/02/lose-the-wait-http-compression
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c.SetEncoder("gzip", encoderGzip)
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// NOTE: Not implemented, intentionally:
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// case "compress": // LZW. Deprecated.
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// case "bzip2": // Too slow on-the-fly.
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// case "zopfli": // Too slow on-the-fly.
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// case "xz": // Too slow on-the-fly.
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return c
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}
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// SetEncoder can be used to set the implementation of a compression algorithm.
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//
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// The encoding should be a standardised identifier. See:
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// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding
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//
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// For example, add the Brotli algortithm:
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//
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// import brotli_enc "gopkg.in/kothar/brotli-go.v0/enc"
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//
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// compressor := middleware.NewCompressor(5, "text/html")
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// compressor.SetEncoder("br", func(w http.ResponseWriter, level int) io.Writer {
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// params := brotli_enc.NewBrotliParams()
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// params.SetQuality(level)
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// return brotli_enc.NewBrotliWriter(params, w)
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// })
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func (c *Compressor) SetEncoder(encoding string, fn EncoderFunc) {
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encoding = strings.ToLower(encoding)
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if encoding == "" {
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panic("the encoding can not be empty")
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}
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if fn == nil {
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panic("attempted to set a nil encoder function")
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}
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// If we are adding a new encoder that is already registered, we have to
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// clear that one out first.
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if _, ok := c.pooledEncoders[encoding]; ok {
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delete(c.pooledEncoders, encoding)
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}
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if _, ok := c.encoders[encoding]; ok {
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delete(c.encoders, encoding)
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}
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// If the encoder supports Resetting (IoReseterWriter), then it can be pooled.
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encoder := fn(ioutil.Discard, c.level)
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if encoder != nil {
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if _, ok := encoder.(ioResetterWriter); ok {
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pool := &sync.Pool{
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New: func() interface{} {
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return fn(ioutil.Discard, c.level)
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},
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}
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c.pooledEncoders[encoding] = pool
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}
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}
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// If the encoder is not in the pooledEncoders, add it to the normal encoders.
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if _, ok := c.pooledEncoders[encoding]; !ok {
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c.encoders[encoding] = fn
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}
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for i, v := range c.encodingPrecedence {
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if v == encoding {
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c.encodingPrecedence = append(c.encodingPrecedence[:i], c.encodingPrecedence[i+1:]...)
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}
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}
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c.encodingPrecedence = append([]string{encoding}, c.encodingPrecedence...)
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}
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// Handler returns a new middleware that will compress the response based on the
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// current Compressor.
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func (c *Compressor) Handler(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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encoder, encoding, cleanup := c.selectEncoder(r.Header, w)
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cw := &compressResponseWriter{
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ResponseWriter: w,
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w: w,
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contentTypes: c.allowedTypes,
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contentWildcards: c.allowedWildcards,
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encoding: encoding,
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compressable: false, // determined in post-handler
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}
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if encoder != nil {
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cw.w = encoder
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}
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// Re-add the encoder to the pool if applicable.
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defer cleanup()
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defer cw.Close()
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next.ServeHTTP(cw, r)
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})
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}
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// selectEncoder returns the encoder, the name of the encoder, and a closer function.
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func (c *Compressor) selectEncoder(h http.Header, w io.Writer) (io.Writer, string, func()) {
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header := h.Get("Accept-Encoding")
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// Parse the names of all accepted algorithms from the header.
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accepted := strings.Split(strings.ToLower(header), ",")
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// Find supported encoder by accepted list by precedence
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for _, name := range c.encodingPrecedence {
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if matchAcceptEncoding(accepted, name) {
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if pool, ok := c.pooledEncoders[name]; ok {
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encoder := pool.Get().(ioResetterWriter)
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cleanup := func() {
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pool.Put(encoder)
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}
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encoder.Reset(w)
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return encoder, name, cleanup
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}
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if fn, ok := c.encoders[name]; ok {
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return fn(w, c.level), name, func() {}
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}
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}
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}
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// No encoder found to match the accepted encoding
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return nil, "", func() {}
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}
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func matchAcceptEncoding(accepted []string, encoding string) bool {
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for _, v := range accepted {
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if strings.Contains(v, encoding) {
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return true
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}
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}
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return false
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}
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// An EncoderFunc is a function that wraps the provided io.Writer with a
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// streaming compression algorithm and returns it.
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//
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// In case of failure, the function should return nil.
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type EncoderFunc func(w io.Writer, level int) io.Writer
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// Interface for types that allow resetting io.Writers.
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type ioResetterWriter interface {
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io.Writer
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Reset(w io.Writer)
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}
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type compressResponseWriter struct {
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http.ResponseWriter
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// The streaming encoder writer to be used if there is one. Otherwise,
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// this is just the normal writer.
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w io.Writer
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encoding string
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contentTypes map[string]struct{}
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contentWildcards map[string]struct{}
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wroteHeader bool
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compressable bool
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}
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func (cw *compressResponseWriter) isCompressable() bool {
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// Parse the first part of the Content-Type response header.
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contentType := cw.Header().Get("Content-Type")
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if idx := strings.Index(contentType, ";"); idx >= 0 {
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contentType = contentType[0:idx]
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}
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// Is the content type compressable?
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if _, ok := cw.contentTypes[contentType]; ok {
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return true
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}
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if idx := strings.Index(contentType, "/"); idx > 0 {
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contentType = contentType[0:idx]
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_, ok := cw.contentWildcards[contentType]
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return ok
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}
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return false
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}
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func (cw *compressResponseWriter) WriteHeader(code int) {
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if cw.wroteHeader {
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cw.ResponseWriter.WriteHeader(code) // Allow multiple calls to propagate.
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return
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}
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cw.wroteHeader = true
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defer cw.ResponseWriter.WriteHeader(code)
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// Already compressed data?
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if cw.Header().Get("Content-Encoding") != "" {
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return
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}
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if !cw.isCompressable() {
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cw.compressable = false
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return
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}
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if cw.encoding != "" {
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cw.compressable = true
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cw.Header().Set("Content-Encoding", cw.encoding)
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cw.Header().Set("Vary", "Accept-Encoding")
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// The content-length after compression is unknown
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cw.Header().Del("Content-Length")
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}
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}
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func (cw *compressResponseWriter) Write(p []byte) (int, error) {
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if !cw.wroteHeader {
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cw.WriteHeader(http.StatusOK)
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}
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return cw.writer().Write(p)
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}
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func (cw *compressResponseWriter) writer() io.Writer {
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if cw.compressable {
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return cw.w
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} else {
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return cw.ResponseWriter
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}
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}
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type compressFlusher interface {
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Flush() error
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}
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func (cw *compressResponseWriter) Flush() {
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if f, ok := cw.writer().(http.Flusher); ok {
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f.Flush()
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}
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// If the underlying writer has a compression flush signature,
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// call this Flush() method instead
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if f, ok := cw.writer().(compressFlusher); ok {
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f.Flush()
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// Also flush the underlying response writer
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if f, ok := cw.ResponseWriter.(http.Flusher); ok {
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f.Flush()
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}
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}
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}
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func (cw *compressResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
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if hj, ok := cw.writer().(http.Hijacker); ok {
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return hj.Hijack()
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}
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return nil, nil, errors.New("chi/middleware: http.Hijacker is unavailable on the writer")
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}
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func (cw *compressResponseWriter) Push(target string, opts *http.PushOptions) error {
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if ps, ok := cw.writer().(http.Pusher); ok {
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return ps.Push(target, opts)
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}
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return errors.New("chi/middleware: http.Pusher is unavailable on the writer")
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}
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func (cw *compressResponseWriter) Close() error {
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if c, ok := cw.writer().(io.WriteCloser); ok {
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return c.Close()
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}
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return errors.New("chi/middleware: io.WriteCloser is unavailable on the writer")
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}
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func encoderGzip(w io.Writer, level int) io.Writer {
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gw, err := gzip.NewWriterLevel(w, level)
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if err != nil {
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return nil
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}
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return gw
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}
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func encoderDeflate(w io.Writer, level int) io.Writer {
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dw, err := flate.NewWriter(w, level)
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if err != nil {
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return nil
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}
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return dw
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}
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