Add NYTimes/gziphandler dependency

2017-06-27 13:04:36 -07:00
parent bd38dd4d12
commit f617df7d6a
17 changed files with 625 additions and 0 deletions
--- a/vendor/github.com/NYTimes/gziphandler/gzip.go
+++ b/vendor/github.com/NYTimes/gziphandler/gzip.go
@@ -0,0 +1,332 @@
+package gziphandler
+
+import (
+	"bufio"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+const (
+	vary            = "Vary"
+	acceptEncoding  = "Accept-Encoding"
+	contentEncoding = "Content-Encoding"
+	contentType     = "Content-Type"
+	contentLength   = "Content-Length"
+)
+
+type codings map[string]float64
+
+const (
+	// DefaultQValue is the default qvalue to assign to an encoding if no explicit qvalue is set.
+	// This is actually kind of ambiguous in RFC 2616, so hopefully it's correct.
+	// The examples seem to indicate that it is.
+	DefaultQValue = 1.0
+
+	// DefaultMinSize defines the minimum size to reach to enable compression.
+	// It's 512 bytes.
+	DefaultMinSize = 512
+)
+
+// gzipWriterPools stores a sync.Pool for each compression level for reuse of
+// gzip.Writers. Use poolIndex to covert a compression level to an index into
+// gzipWriterPools.
+var gzipWriterPools [gzip.BestCompression - gzip.BestSpeed + 2]*sync.Pool
+
+func init() {
+	for i := gzip.BestSpeed; i <= gzip.BestCompression; i++ {
+		addLevelPool(i)
+	}
+	addLevelPool(gzip.DefaultCompression)
+}
+
+// poolIndex maps a compression level to its index into gzipWriterPools. It
+// assumes that level is a valid gzip compression level.
+func poolIndex(level int) int {
+	// gzip.DefaultCompression == -1, so we need to treat it special.
+	if level == gzip.DefaultCompression {
+		return gzip.BestCompression - gzip.BestSpeed + 1
+	}
+	return level - gzip.BestSpeed
+}
+
+func addLevelPool(level int) {
+	gzipWriterPools[poolIndex(level)] = &sync.Pool{
+		New: func() interface{} {
+			// NewWriterLevel only returns error on a bad level, we are guaranteeing
+			// that this will be a valid level so it is okay to ignore the returned
+			// error.
+			w, _ := gzip.NewWriterLevel(nil, level)
+			return w
+		},
+	}
+}
+
+// GzipResponseWriter provides an http.ResponseWriter interface, which gzips
+// bytes before writing them to the underlying response. This doesn't close the
+// writers, so don't forget to do that.
+// It can be configured to skip response smaller than minSize.
+type GzipResponseWriter struct {
+	http.ResponseWriter
+	index int // Index for gzipWriterPools.
+	gw    *gzip.Writer
+
+	code int // Saves the WriteHeader value.
+
+	minSize int    // Specifed the minimum response size to gzip. If the response length is bigger than this value, it is compressed.
+	buf     []byte // Holds the first part of the write before reaching the minSize or the end of the write.
+}
+
+// Write appends data to the gzip writer.
+func (w *GzipResponseWriter) Write(b []byte) (int, error) {
+	// If content type is not set.
+	if _, ok := w.Header()[contentType]; !ok {
+		// It infer it from the uncompressed body.
+		w.Header().Set(contentType, http.DetectContentType(b))
+	}
+
+	// GZIP responseWriter is initialized. Use the GZIP responseWriter.
+	if w.gw != nil {
+		n, err := w.gw.Write(b)
+		return n, err
+	}
+
+	// Save the write into a buffer for later use in GZIP responseWriter (if content is long enough) or at close with regular responseWriter.
+	// On the first write, w.buf changes from nil to a valid slice
+	w.buf = append(w.buf, b...)
+
+	// If the global writes are bigger than the minSize, compression is enable.
+	if len(w.buf) >= w.minSize {
+		err := w.startGzip()
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	return len(b), nil
+}
+
+// startGzip initialize any GZIP specific informations.
+func (w *GzipResponseWriter) startGzip() error {
+
+	// Set the GZIP header.
+	w.Header().Set(contentEncoding, "gzip")
+
+	// if the Content-Length is already set, then calls to Write on gzip
+	// will fail to set the Content-Length header since its already set
+	// See: https://github.com/golang/go/issues/14975.
+	w.Header().Del(contentLength)
+
+	// Write the header to gzip response.
+	if w.code != 0 {
+		w.ResponseWriter.WriteHeader(w.code)
+	}
+
+	// Initialize the GZIP response.
+	w.init()
+
+	// Flush the buffer into the gzip reponse.
+	n, err := w.gw.Write(w.buf)
+
+	// This should never happen (per io.Writer docs), but if the write didn't
+	// accept the entire buffer but returned no specific error, we have no clue
+	// what's going on, so abort just to be safe.
+	if err == nil && n < len(w.buf) {
+		return io.ErrShortWrite
+	}
+
+	w.buf = nil
+	return err
+}
+
+// WriteHeader just saves the response code until close or GZIP effective writes.
+func (w *GzipResponseWriter) WriteHeader(code int) {
+	w.code = code
+}
+
+// init graps a new gzip writer from the gzipWriterPool and writes the correct
+// content encoding header.
+func (w *GzipResponseWriter) init() {
+	// Bytes written during ServeHTTP are redirected to this gzip writer
+	// before being written to the underlying response.
+	gzw := gzipWriterPools[w.index].Get().(*gzip.Writer)
+	gzw.Reset(w.ResponseWriter)
+	w.gw = gzw
+}
+
+// Close will close the gzip.Writer and will put it back in the gzipWriterPool.
+func (w *GzipResponseWriter) Close() error {
+	if w.gw == nil {
+		// Gzip not trigged yet, write out regular response.
+		if w.code != 0 {
+			w.ResponseWriter.WriteHeader(w.code)
+		}
+		if w.buf != nil {
+			_, writeErr := w.ResponseWriter.Write(w.buf)
+			// Returns the error if any at write.
+			if writeErr != nil {
+				return fmt.Errorf("gziphandler: write to regular responseWriter at close gets error: %q", writeErr.Error())
+			}
+		}
+		return nil
+	}
+
+	err := w.gw.Close()
+	gzipWriterPools[w.index].Put(w.gw)
+	w.gw = nil
+	return err
+}
+
+// Flush flushes the underlying *gzip.Writer and then the underlying
+// http.ResponseWriter if it is an http.Flusher. This makes GzipResponseWriter
+// an http.Flusher.
+func (w *GzipResponseWriter) Flush() {
+	if w.gw != nil {
+		w.gw.Flush()
+	}
+
+	if fw, ok := w.ResponseWriter.(http.Flusher); ok {
+		fw.Flush()
+	}
+}
+
+// Hijack implements http.Hijacker. If the underlying ResponseWriter is a
+// Hijacker, its Hijack method is returned. Otherwise an error is returned.
+func (w *GzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if hj, ok := w.ResponseWriter.(http.Hijacker); ok {
+		return hj.Hijack()
+	}
+	return nil, nil, fmt.Errorf("http.Hijacker interface is not supported")
+}
+
+// verify Hijacker interface implementation
+var _ http.Hijacker = &GzipResponseWriter{}
+
+// MustNewGzipLevelHandler behaves just like NewGzipLevelHandler except that in
+// an error case it panics rather than returning an error.
+func MustNewGzipLevelHandler(level int) func(http.Handler) http.Handler {
+	wrap, err := NewGzipLevelHandler(level)
+	if err != nil {
+		panic(err)
+	}
+	return wrap
+}
+
+// NewGzipLevelHandler returns a wrapper function (often known as middleware)
+// which can be used to wrap an HTTP handler to transparently gzip the response
+// body if the client supports it (via the Accept-Encoding header). Responses will
+// be encoded at the given gzip compression level. An error will be returned only
+// if an invalid gzip compression level is given, so if one can ensure the level
+// is valid, the returned error can be safely ignored.
+func NewGzipLevelHandler(level int) (func(http.Handler) http.Handler, error) {
+	return NewGzipLevelAndMinSize(level, DefaultMinSize)
+}
+
+// NewGzipLevelAndMinSize behave as NewGzipLevelHandler except it let the caller
+// specify the minimum size before compression.
+func NewGzipLevelAndMinSize(level, minSize int) (func(http.Handler) http.Handler, error) {
+	if level != gzip.DefaultCompression && (level < gzip.BestSpeed || level > gzip.BestCompression) {
+		return nil, fmt.Errorf("invalid compression level requested: %d", level)
+	}
+	if minSize < 0 {
+		return nil, fmt.Errorf("minimum size must be more than zero")
+	}
+	return func(h http.Handler) http.Handler {
+		index := poolIndex(level)
+
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Add(vary, acceptEncoding)
+
+			if acceptsGzip(r) {
+				gw := &GzipResponseWriter{
+					ResponseWriter: w,
+					index:          index,
+					minSize:        minSize,
+				}
+				defer gw.Close()
+
+				h.ServeHTTP(gw, r)
+			} else {
+				h.ServeHTTP(w, r)
+			}
+		})
+	}, nil
+}
+
+// GzipHandler wraps an HTTP handler, to transparently gzip the response body if
+// the client supports it (via the Accept-Encoding header). This will compress at
+// the default compression level.
+func GzipHandler(h http.Handler) http.Handler {
+	wrapper, _ := NewGzipLevelHandler(gzip.DefaultCompression)
+	return wrapper(h)
+}
+
+// acceptsGzip returns true if the given HTTP request indicates that it will
+// accept a gzipped response.
+func acceptsGzip(r *http.Request) bool {
+	acceptedEncodings, _ := parseEncodings(r.Header.Get(acceptEncoding))
+	return acceptedEncodings["gzip"] > 0.0
+}
+
+// parseEncodings attempts to parse a list of codings, per RFC 2616, as might
+// appear in an Accept-Encoding header. It returns a map of content-codings to
+// quality values, and an error containing the errors encountered. It's probably
+// safe to ignore those, because silently ignoring errors is how the internet
+// works.
+//
+// See: http://tools.ietf.org/html/rfc2616#section-14.3.
+func parseEncodings(s string) (codings, error) {
+	c := make(codings)
+	var e []string
+
+	for _, ss := range strings.Split(s, ",") {
+		coding, qvalue, err := parseCoding(ss)
+
+		if err != nil {
+			e = append(e, err.Error())
+		} else {
+			c[coding] = qvalue
+		}
+	}
+
+	// TODO (adammck): Use a proper multi-error struct, so the individual errors
+	//                 can be extracted if anyone cares.
+	if len(e) > 0 {
+		return c, fmt.Errorf("errors while parsing encodings: %s", strings.Join(e, ", "))
+	}
+
+	return c, nil
+}
+
+// parseCoding parses a single conding (content-coding with an optional qvalue),
+// as might appear in an Accept-Encoding header. It attempts to forgive minor
+// formatting errors.
+func parseCoding(s string) (coding string, qvalue float64, err error) {
+	for n, part := range strings.Split(s, ";") {
+		part = strings.TrimSpace(part)
+		qvalue = DefaultQValue
+
+		if n == 0 {
+			coding = strings.ToLower(part)
+		} else if strings.HasPrefix(part, "q=") {
+			qvalue, err = strconv.ParseFloat(strings.TrimPrefix(part, "q="), 64)
+
+			if qvalue < 0.0 {
+				qvalue = 0.0
+			} else if qvalue > 1.0 {
+				qvalue = 1.0
+			}
+		}
+	}
+
+	if coding == "" {
+		err = fmt.Errorf("empty content-coding")
+	}
+
+	return
+}