mirror of https://github.com/status-im/consul.git
430 lines
12 KiB
Go
430 lines
12 KiB
Go
package gziphandler
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import (
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"bufio"
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"compress/gzip"
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"fmt"
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"io"
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"net"
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"net/http"
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"strconv"
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"strings"
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"sync"
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)
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const (
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vary = "Vary"
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acceptEncoding = "Accept-Encoding"
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contentEncoding = "Content-Encoding"
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contentType = "Content-Type"
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contentLength = "Content-Length"
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)
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type codings map[string]float64
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const (
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// DefaultQValue is the default qvalue to assign to an encoding if no explicit qvalue is set.
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// This is actually kind of ambiguous in RFC 2616, so hopefully it's correct.
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// The examples seem to indicate that it is.
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DefaultQValue = 1.0
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// 1500 bytes is the MTU size for the internet since that is the largest size allowed at the network layer.
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// If you take a file that is 1300 bytes and compress it to 800 bytes, it’s still transmitted in that same 1500 byte packet regardless, so you’ve gained nothing.
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// That being the case, you should restrict the gzip compression to files with a size greater than a single packet, 1400 bytes (1.4KB) is a safe value.
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DefaultMinSize = 1400
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)
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// gzipWriterPools stores a sync.Pool for each compression level for reuse of
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// gzip.Writers. Use poolIndex to covert a compression level to an index into
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// gzipWriterPools.
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var gzipWriterPools [gzip.BestCompression - gzip.BestSpeed + 2]*sync.Pool
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func init() {
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for i := gzip.BestSpeed; i <= gzip.BestCompression; i++ {
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addLevelPool(i)
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}
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addLevelPool(gzip.DefaultCompression)
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}
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// poolIndex maps a compression level to its index into gzipWriterPools. It
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// assumes that level is a valid gzip compression level.
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func poolIndex(level int) int {
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// gzip.DefaultCompression == -1, so we need to treat it special.
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if level == gzip.DefaultCompression {
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return gzip.BestCompression - gzip.BestSpeed + 1
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}
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return level - gzip.BestSpeed
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}
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func addLevelPool(level int) {
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gzipWriterPools[poolIndex(level)] = &sync.Pool{
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New: func() interface{} {
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// NewWriterLevel only returns error on a bad level, we are guaranteeing
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// that this will be a valid level so it is okay to ignore the returned
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// error.
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w, _ := gzip.NewWriterLevel(nil, level)
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return w
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},
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}
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}
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// GzipResponseWriter provides an http.ResponseWriter interface, which gzips
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// bytes before writing them to the underlying response. This doesn't close the
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// writers, so don't forget to do that.
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// It can be configured to skip response smaller than minSize.
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type GzipResponseWriter struct {
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http.ResponseWriter
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index int // Index for gzipWriterPools.
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gw *gzip.Writer
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code int // Saves the WriteHeader value.
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minSize int // Specifed the minimum response size to gzip. If the response length is bigger than this value, it is compressed.
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buf []byte // Holds the first part of the write before reaching the minSize or the end of the write.
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contentTypes []string // Only compress if the response is one of these content-types. All are accepted if empty.
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}
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type GzipResponseWriterWithCloseNotify struct {
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*GzipResponseWriter
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}
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func (w GzipResponseWriterWithCloseNotify) CloseNotify() <-chan bool {
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return w.ResponseWriter.(http.CloseNotifier).CloseNotify()
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}
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// Write appends data to the gzip writer.
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func (w *GzipResponseWriter) Write(b []byte) (int, error) {
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// If content type is not set.
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if _, ok := w.Header()[contentType]; !ok {
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// It infer it from the uncompressed body.
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w.Header().Set(contentType, http.DetectContentType(b))
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}
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// GZIP responseWriter is initialized. Use the GZIP responseWriter.
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if w.gw != nil {
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n, err := w.gw.Write(b)
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return n, err
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}
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// Save the write into a buffer for later use in GZIP responseWriter (if content is long enough) or at close with regular responseWriter.
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// On the first write, w.buf changes from nil to a valid slice
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w.buf = append(w.buf, b...)
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// If the global writes are bigger than the minSize and we're about to write
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// a response containing a content type we want to handle, enable
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// compression.
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if len(w.buf) >= w.minSize && handleContentType(w.contentTypes, w) && w.Header().Get(contentEncoding) == "" {
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err := w.startGzip()
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if err != nil {
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return 0, err
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}
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}
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return len(b), nil
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}
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// startGzip initialize any GZIP specific informations.
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func (w *GzipResponseWriter) startGzip() error {
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// Set the GZIP header.
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w.Header().Set(contentEncoding, "gzip")
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// if the Content-Length is already set, then calls to Write on gzip
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// will fail to set the Content-Length header since its already set
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// See: https://github.com/golang/go/issues/14975.
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w.Header().Del(contentLength)
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// Write the header to gzip response.
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if w.code != 0 {
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w.ResponseWriter.WriteHeader(w.code)
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}
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// Initialize the GZIP response.
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w.init()
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// Flush the buffer into the gzip response.
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n, err := w.gw.Write(w.buf)
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// This should never happen (per io.Writer docs), but if the write didn't
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// accept the entire buffer but returned no specific error, we have no clue
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// what's going on, so abort just to be safe.
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if err == nil && n < len(w.buf) {
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return io.ErrShortWrite
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}
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w.buf = nil
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return err
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}
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// WriteHeader just saves the response code until close or GZIP effective writes.
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func (w *GzipResponseWriter) WriteHeader(code int) {
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if w.code == 0 {
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w.code = code
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}
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}
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// init graps a new gzip writer from the gzipWriterPool and writes the correct
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// content encoding header.
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func (w *GzipResponseWriter) init() {
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// Bytes written during ServeHTTP are redirected to this gzip writer
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// before being written to the underlying response.
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gzw := gzipWriterPools[w.index].Get().(*gzip.Writer)
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gzw.Reset(w.ResponseWriter)
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w.gw = gzw
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}
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// Close will close the gzip.Writer and will put it back in the gzipWriterPool.
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func (w *GzipResponseWriter) Close() error {
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if w.gw == nil {
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// Gzip not trigged yet, write out regular response.
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if w.code != 0 {
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w.ResponseWriter.WriteHeader(w.code)
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}
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if w.buf != nil {
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_, writeErr := w.ResponseWriter.Write(w.buf)
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// Returns the error if any at write.
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if writeErr != nil {
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return fmt.Errorf("gziphandler: write to regular responseWriter at close gets error: %q", writeErr.Error())
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}
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}
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return nil
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}
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err := w.gw.Close()
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gzipWriterPools[w.index].Put(w.gw)
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w.gw = nil
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return err
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}
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// Flush flushes the underlying *gzip.Writer and then the underlying
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// http.ResponseWriter if it is an http.Flusher. This makes GzipResponseWriter
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// an http.Flusher.
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func (w *GzipResponseWriter) Flush() {
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if w.gw == nil {
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// Only flush once startGzip has been called.
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//
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// Flush is thus a no-op until the written body
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// exceeds minSize.
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return
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}
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w.gw.Flush()
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if fw, ok := w.ResponseWriter.(http.Flusher); ok {
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fw.Flush()
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}
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}
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// Hijack implements http.Hijacker. If the underlying ResponseWriter is a
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// Hijacker, its Hijack method is returned. Otherwise an error is returned.
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func (w *GzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
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if hj, ok := w.ResponseWriter.(http.Hijacker); ok {
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return hj.Hijack()
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}
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return nil, nil, fmt.Errorf("http.Hijacker interface is not supported")
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}
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// verify Hijacker interface implementation
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var _ http.Hijacker = &GzipResponseWriter{}
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// MustNewGzipLevelHandler behaves just like NewGzipLevelHandler except that in
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// an error case it panics rather than returning an error.
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func MustNewGzipLevelHandler(level int) func(http.Handler) http.Handler {
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wrap, err := NewGzipLevelHandler(level)
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if err != nil {
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panic(err)
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}
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return wrap
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}
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// NewGzipLevelHandler returns a wrapper function (often known as middleware)
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// which can be used to wrap an HTTP handler to transparently gzip the response
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// body if the client supports it (via the Accept-Encoding header). Responses will
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// be encoded at the given gzip compression level. An error will be returned only
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// if an invalid gzip compression level is given, so if one can ensure the level
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// is valid, the returned error can be safely ignored.
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func NewGzipLevelHandler(level int) (func(http.Handler) http.Handler, error) {
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return NewGzipLevelAndMinSize(level, DefaultMinSize)
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}
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// NewGzipLevelAndMinSize behave as NewGzipLevelHandler except it let the caller
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// specify the minimum size before compression.
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func NewGzipLevelAndMinSize(level, minSize int) (func(http.Handler) http.Handler, error) {
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return GzipHandlerWithOpts(CompressionLevel(level), MinSize(minSize))
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}
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func GzipHandlerWithOpts(opts ...option) (func(http.Handler) http.Handler, error) {
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c := &config{
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level: gzip.DefaultCompression,
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minSize: DefaultMinSize,
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}
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for _, o := range opts {
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o(c)
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}
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if err := c.validate(); err != nil {
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return nil, err
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}
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return func(h http.Handler) http.Handler {
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index := poolIndex(c.level)
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.Header().Add(vary, acceptEncoding)
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if acceptsGzip(r) {
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gw := &GzipResponseWriter{
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ResponseWriter: w,
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index: index,
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minSize: c.minSize,
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contentTypes: c.contentTypes,
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}
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defer gw.Close()
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if _, ok := w.(http.CloseNotifier); ok {
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gwcn := GzipResponseWriterWithCloseNotify{gw}
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h.ServeHTTP(gwcn, r)
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} else {
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h.ServeHTTP(gw, r)
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}
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} else {
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h.ServeHTTP(w, r)
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}
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})
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}, nil
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}
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// Used for functional configuration.
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type config struct {
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minSize int
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level int
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contentTypes []string
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}
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func (c *config) validate() error {
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if c.level != gzip.DefaultCompression && (c.level < gzip.BestSpeed || c.level > gzip.BestCompression) {
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return fmt.Errorf("invalid compression level requested: %d", c.level)
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}
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if c.minSize < 0 {
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return fmt.Errorf("minimum size must be more than zero")
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}
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return nil
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}
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type option func(c *config)
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func MinSize(size int) option {
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return func(c *config) {
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c.minSize = size
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}
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}
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func CompressionLevel(level int) option {
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return func(c *config) {
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c.level = level
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}
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}
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func ContentTypes(types []string) option {
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return func(c *config) {
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c.contentTypes = []string{}
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for _, v := range types {
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c.contentTypes = append(c.contentTypes, strings.ToLower(v))
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}
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}
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}
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// GzipHandler wraps an HTTP handler, to transparently gzip the response body if
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// the client supports it (via the Accept-Encoding header). This will compress at
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// the default compression level.
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func GzipHandler(h http.Handler) http.Handler {
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wrapper, _ := NewGzipLevelHandler(gzip.DefaultCompression)
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return wrapper(h)
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}
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// acceptsGzip returns true if the given HTTP request indicates that it will
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// accept a gzipped response.
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func acceptsGzip(r *http.Request) bool {
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acceptedEncodings, _ := parseEncodings(r.Header.Get(acceptEncoding))
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return acceptedEncodings["gzip"] > 0.0
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}
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// returns true if we've been configured to compress the specific content type.
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func handleContentType(contentTypes []string, w http.ResponseWriter) bool {
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// If contentTypes is empty we handle all content types.
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if len(contentTypes) == 0 {
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return true
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}
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ct := strings.ToLower(w.Header().Get(contentType))
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for _, c := range contentTypes {
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if c == ct {
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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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// parseEncodings attempts to parse a list of codings, per RFC 2616, as might
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// appear in an Accept-Encoding header. It returns a map of content-codings to
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// quality values, and an error containing the errors encountered. It's probably
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// safe to ignore those, because silently ignoring errors is how the internet
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// works.
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//
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// See: http://tools.ietf.org/html/rfc2616#section-14.3.
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func parseEncodings(s string) (codings, error) {
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c := make(codings)
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var e []string
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for _, ss := range strings.Split(s, ",") {
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coding, qvalue, err := parseCoding(ss)
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if err != nil {
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e = append(e, err.Error())
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} else {
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c[coding] = qvalue
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}
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}
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// TODO (adammck): Use a proper multi-error struct, so the individual errors
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// can be extracted if anyone cares.
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if len(e) > 0 {
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return c, fmt.Errorf("errors while parsing encodings: %s", strings.Join(e, ", "))
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}
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return c, nil
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}
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// parseCoding parses a single conding (content-coding with an optional qvalue),
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// as might appear in an Accept-Encoding header. It attempts to forgive minor
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// formatting errors.
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func parseCoding(s string) (coding string, qvalue float64, err error) {
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for n, part := range strings.Split(s, ";") {
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part = strings.TrimSpace(part)
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qvalue = DefaultQValue
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if n == 0 {
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coding = strings.ToLower(part)
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} else if strings.HasPrefix(part, "q=") {
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qvalue, err = strconv.ParseFloat(strings.TrimPrefix(part, "q="), 64)
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if qvalue < 0.0 {
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qvalue = 0.0
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} else if qvalue > 1.0 {
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qvalue = 1.0
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}
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}
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}
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if coding == "" {
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err = fmt.Errorf("empty content-coding")
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}
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return
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}
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