From dffcf6c203f7542e4503f0a9ee83663cf8298d8b Mon Sep 17 00:00:00 2001 From: Ankit Patial Date: Thu, 20 Nov 2025 22:50:28 +0530 Subject: [PATCH] feat: add compression middleware for response body optimization --- middleware/compress.go | 407 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 407 insertions(+) create mode 100644 middleware/compress.go diff --git a/middleware/compress.go b/middleware/compress.go new file mode 100644 index 0000000..b2f3933 --- /dev/null +++ b/middleware/compress.go @@ -0,0 +1,407 @@ +// Originally from: https://github.com/go-chi/chi/blob/master/mw/compress.go +// Copyright (c) 2015-present Peter Kieltyka (https://github.com/pkieltyka), Google Inc. +// MIT License + +package middleware + +import ( + "bufio" + "compress/flate" + "compress/gzip" + "errors" + "fmt" + "io" + "net" + "net/http" + "strings" + "sync" +) + +var defaultCompressibleContentTypes = []string{ + "text/html", + "text/css", + "text/plain", + "text/javascript", + "application/javascript", + "application/x-javascript", + "application/json", + "application/atom+xml", + "application/rss+xml", + "image/svg+xml", +} + +// Compress is a middleware that compresses response +// body of a given content types to a data format based +// on Accept-Encoding request header. It uses a given +// compression level. +// +// NOTE: make sure to set the Content-Type header on your response +// otherwise this middleware will not compress the response body. For ex, in +// your handler you should set w.Header().Set("Content-Type", http.DetectContentType(yourBody)) +// or set it manually. +// +// Passing a compression level of 5 is sensible value +func Compress(level int, types ...string) func(next http.Handler) http.Handler { + compressor := NewCompressor(level, types...) + return compressor.Handler +} + +// Compressor represents a set of encoding configurations. +type Compressor struct { + // The mapping of encoder names to encoder functions. + encoders map[string]EncoderFunc + // The mapping of pooled encoders to pools. + pooledEncoders map[string]*sync.Pool + // The set of content types allowed to be compressed. + allowedTypes map[string]struct{} + allowedWildcards map[string]struct{} + // The list of encoders in order of decreasing precedence. + encodingPrecedence []string + level int // The compression level. +} + +// NewCompressor creates a new Compressor that will handle encoding responses. +// +// The level should be one of the ones defined in the flate package. +// The types are the content types that are allowed to be compressed. +func NewCompressor(level int, types ...string) *Compressor { + // If types are provided, set those as the allowed types. If none are + // provided, use the default list. + allowedTypes := make(map[string]struct{}) + allowedWildcards := make(map[string]struct{}) + if len(types) > 0 { + for _, t := range types { + if strings.Contains(strings.TrimSuffix(t, "/*"), "*") { + panic(fmt.Sprintf("mw/compress: Unsupported content-type wildcard pattern '%s'. Only '/*' supported", t)) + } + if strings.HasSuffix(t, "/*") { + allowedWildcards[strings.TrimSuffix(t, "/*")] = struct{}{} + } else { + allowedTypes[t] = struct{}{} + } + } + } else { + for _, t := range defaultCompressibleContentTypes { + allowedTypes[t] = struct{}{} + } + } + + c := &Compressor{ + level: level, + encoders: make(map[string]EncoderFunc), + pooledEncoders: make(map[string]*sync.Pool), + allowedTypes: allowedTypes, + allowedWildcards: allowedWildcards, + } + + // Set the default encoders. The precedence order uses the reverse + // ordering that the encoders were added. This means adding new encoders + // will move them to the front of the order. + // + // TODO: + // lzma: Opera. + // sdch: Chrome, Android. Gzip output + dictionary header. + // br: Brotli, see https://github.com/go-chi/chi/pull/326 + + // HTTP 1.1 "deflate" (RFC 2616) stands for DEFLATE data (RFC 1951) + // wrapped with zlib (RFC 1950). The zlib wrapper uses Adler-32 + // checksum compared to CRC-32 used in "gzip" and thus is faster. + // + // But.. some old browsers (MSIE, Safari 5.1) incorrectly expect + // raw DEFLATE data only, without the mentioned zlib wrapper. + // Because of this major confusion, most modern browsers try it + // both ways, first looking for zlib headers. + // Quote by Mark Adler: http://stackoverflow.com/a/9186091/385548 + // + // The list of browsers having problems is quite big, see: + // http://zoompf.com/blog/2012/02/lose-the-wait-http-compression + // https://web.archive.org/web/20120321182910/http://www.vervestudios.co/projects/compression-tests/results + // + // That's why we prefer gzip over deflate. It's just more reliable + // and not significantly slower than deflate. + c.SetEncoder("deflate", encoderDeflate) + + // TODO: Exception for old MSIE browsers that can't handle non-HTML? + // https://zoompf.com/blog/2012/02/lose-the-wait-http-compression + c.SetEncoder("gzip", encoderGzip) + + // NOTE: Not implemented, intentionally: + // case "compress": // LZW. Deprecated. + // case "bzip2": // Too slow on-the-fly. + // case "zopfli": // Too slow on-the-fly. + // case "xz": // Too slow on-the-fly. + return c +} + +// SetEncoder can be used to set the implementation of a compression algorithm. +// +// The encoding should be a standardised identifier. See: +// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding +// +// For example, add the Brotli algorithm: +// +// import brotli_enc "gopkg.in/kothar/brotli-go.v0/enc" +// +// compressor := middleware.NewCompressor(5, "text/html") +// compressor.SetEncoder("br", func(w io.Writer, level int) io.Writer { +// params := brotli_enc.NewBrotliParams() +// params.SetQuality(level) +// return brotli_enc.NewBrotliWriter(params, w) +// }) +func (c *Compressor) SetEncoder(encoding string, fn EncoderFunc) { + encoding = strings.ToLower(encoding) + if encoding == "" { + panic("the encoding can not be empty") + } + if fn == nil { + panic("attempted to set a nil encoder function") + } + + // If we are adding a new encoder that is already registered, we have to + // clear that one out first. + delete(c.pooledEncoders, encoding) + delete(c.encoders, encoding) + + // If the encoder supports Resetting (IoReseterWriter), then it can be pooled. + encoder := fn(io.Discard, c.level) + if _, ok := encoder.(ioResetterWriter); ok { + pool := &sync.Pool{ + New: func() any { + return fn(io.Discard, c.level) + }, + } + c.pooledEncoders[encoding] = pool + } + // If the encoder is not in the pooledEncoders, add it to the normal encoders. + if _, ok := c.pooledEncoders[encoding]; !ok { + c.encoders[encoding] = fn + } + + for i, v := range c.encodingPrecedence { + if v == encoding { + c.encodingPrecedence = append(c.encodingPrecedence[:i], c.encodingPrecedence[i+1:]...) + } + } + + c.encodingPrecedence = append([]string{encoding}, c.encodingPrecedence...) +} + +// Handler returns a new middleware that will compress the response based on the +// current Compressor. +func (c *Compressor) Handler(next http.Handler) http.Handler { + return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { + // Skip compression for WebSocket upgrades + if r.Header.Get("Upgrade") == "websocket" { + next.ServeHTTP(w, r) + return + } + + encoder, encoding, cleanup := c.selectEncoder(r.Header, w) + + cw := &compressResponseWriter{ + ResponseWriter: w, + w: w, + contentTypes: c.allowedTypes, + contentWildcards: c.allowedWildcards, + encoding: encoding, + compressible: false, // determined in post-handler + } + if encoder != nil { + cw.w = encoder + } + // Re-add the encoder to the pool if applicable. + defer cleanup() + defer cw.Close() + + next.ServeHTTP(cw, r) + }) +} + +// selectEncoder returns the encoder, the name of the encoder, and a closer function. +func (c *Compressor) selectEncoder(h http.Header, w io.Writer) (io.Writer, string, func()) { + header := h.Get("Accept-Encoding") + + // Parse the names of all accepted algorithms from the header. + accepted := strings.Split(strings.ToLower(header), ",") + + // Find supported encoder by accepted list by precedence + for _, name := range c.encodingPrecedence { + if matchAcceptEncoding(accepted, name) { + if pool, ok := c.pooledEncoders[name]; ok { + encoder := pool.Get().(ioResetterWriter) + cleanup := func() { + pool.Put(encoder) + } + encoder.Reset(w) + return encoder, name, cleanup + + } + if fn, ok := c.encoders[name]; ok { + return fn(w, c.level), name, func() {} + } + } + + } + + // No encoder found to match the accepted encoding + return nil, "", func() {} +} + +func matchAcceptEncoding(accepted []string, encoding string) bool { + for _, v := range accepted { + v = strings.TrimSpace(v) + // Handle quality values like "gzip;q=0.8" + if idx := strings.Index(v, ";"); idx != -1 { + v = strings.TrimSpace(v[:idx]) + } + if v == encoding { + return true + } + } + return false +} + +// An EncoderFunc is a function that wraps the provided io.Writer with a +// streaming compression algorithm and returns it. +// +// In case of failure, the function should return nil. +type EncoderFunc func(w io.Writer, level int) io.Writer + +// Interface for types that allow resetting io.Writers. +type ioResetterWriter interface { + io.Writer + Reset(w io.Writer) +} + +type compressResponseWriter struct { + http.ResponseWriter + + // The streaming encoder writer to be used if there is one. Otherwise, + // this is just the normal writer. + w io.Writer + contentTypes map[string]struct{} + contentWildcards map[string]struct{} + encoding string + wroteHeader bool + compressible bool +} + +func (cw *compressResponseWriter) isCompressible() bool { + // Parse the first part of the Content-Type response header. + contentType := cw.Header().Get("Content-Type") + contentType, _, _ = strings.Cut(contentType, ";") + + // Is the content type compressible? + if _, ok := cw.contentTypes[contentType]; ok { + return true + } + if contentType, _, hadSlash := strings.Cut(contentType, "/"); hadSlash { + _, ok := cw.contentWildcards[contentType] + return ok + } + return false +} + +func (cw *compressResponseWriter) WriteHeader(code int) { + if cw.wroteHeader { + cw.ResponseWriter.WriteHeader(code) // Allow multiple calls to propagate. + return + } + cw.wroteHeader = true + defer cw.ResponseWriter.WriteHeader(code) + + // Already compressed data? + if cw.Header().Get("Content-Encoding") != "" { + return + } + + if !cw.isCompressible() { + cw.compressible = false + return + } + + if cw.encoding != "" { + cw.compressible = true + cw.Header().Set("Content-Encoding", cw.encoding) + cw.Header().Add("Vary", "Accept-Encoding") + + // The content-length after compression is unknown + cw.Header().Del("Content-Length") + } +} + +func (cw *compressResponseWriter) Write(p []byte) (int, error) { + if !cw.wroteHeader { + cw.WriteHeader(http.StatusOK) + } + + return cw.writer().Write(p) +} + +func (cw *compressResponseWriter) writer() io.Writer { + if cw.compressible { + return cw.w + } + return cw.ResponseWriter +} + +type compressFlusher interface { + Flush() error +} + +func (cw *compressResponseWriter) Flush() { + if f, ok := cw.writer().(http.Flusher); ok { + f.Flush() + } + // If the underlying writer has a compression flush signature, + // call this Flush() method instead + if f, ok := cw.writer().(compressFlusher); ok { + f.Flush() + + // Also flush the underlying response writer + if f, ok := cw.ResponseWriter.(http.Flusher); ok { + f.Flush() + } + } +} + +func (cw *compressResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) { + if hj, ok := cw.writer().(http.Hijacker); ok { + return hj.Hijack() + } + return nil, nil, errors.New("mw/compress: http.Hijacker is unavailable on the writer") +} + +func (cw *compressResponseWriter) Push(target string, opts *http.PushOptions) error { + if ps, ok := cw.writer().(http.Pusher); ok { + return ps.Push(target, opts) + } + return errors.New("mw/compress: http.Pusher is unavailable on the writer") +} + +func (cw *compressResponseWriter) Close() error { + if c, ok := cw.writer().(io.WriteCloser); ok { + return c.Close() + } + return errors.New("mw/compress: io.WriteCloser is unavailable on the writer") +} + +func (cw *compressResponseWriter) Unwrap() http.ResponseWriter { + return cw.ResponseWriter +} + +func encoderGzip(w io.Writer, level int) io.Writer { + gw, err := gzip.NewWriterLevel(w, level) + if err != nil { + return nil + } + return gw +} + +func encoderDeflate(w io.Writer, level int) io.Writer { + dw, err := flate.NewWriter(w, level) + if err != nil { + return nil + } + return dw +}