Copy negotiateContentEncoding.

A little copying is better than a little dependency.

Fixes #8

go.mod

@@ -1,5 +1,3 @@
 module github.com/andybalholm/brotli
 
 go 1.12
-
-require github.com/golang/gddo v0.0.0-20190419222130-af0f2af80721

go.sum

@@ -1,2 +0,0 @@
-github.com/golang/gddo v0.0.0-20190419222130-af0f2af80721 h1:KRMr9A3qfbVM7iV/WcLY/rL5LICqwMHLhwRXKu99fXw=
-github.com/golang/gddo v0.0.0-20190419222130-af0f2af80721/go.mod h1:xEhNfoBDX1hzLm2Nf80qUvZ2sVwoMZ8d6IE2SrsQfh4=

http.go

@@ -0,0 +1,192 @@
+package brotli
+
+import (
+	"compress/gzip"
+	"io"
+	"net/http"
+	"strings"
+)
+
+// HTTPCompressor chooses a compression method (brotli, gzip, or none) based on
+// the Accept-Encoding header, sets the Content-Encoding header, and returns a
+// WriteCloser that implements that compression. The Close method must be called
+// before the current HTTP handler returns.
+//
+// Due to https://github.com/golang/go/issues/31753, the response will not be
+// compressed unless you set a Content-Type header before you call
+// HTTPCompressor.
+func HTTPCompressor(w http.ResponseWriter, r *http.Request) io.WriteCloser {
+	if w.Header().Get("Content-Type") == "" {
+		return nopCloser{w}
+	}
+
+	if w.Header().Get("Vary") == "" {
+		w.Header().Set("Vary", "Accept-Encoding")
+	}
+
+	encoding := negotiateContentEncoding(r, []string{"br", "gzip"})
+	switch encoding {
+	case "br":
+		w.Header().Set("Content-Encoding", "br")
+		return NewWriter(w)
+	case "gzip":
+		w.Header().Set("Content-Encoding", "gzip")
+		return gzip.NewWriter(w)
+	}
+	return nopCloser{w}
+}
+
+// negotiateContentEncoding returns the best offered content encoding for the
+// request's Accept-Encoding header. If two offers match with equal weight and
+// then the offer earlier in the list is preferred. If no offers are
+// acceptable, then "" is returned.
+func negotiateContentEncoding(r *http.Request, offers []string) string {
+	bestOffer := "identity"
+	bestQ := -1.0
+	specs := parseAccept(r.Header, "Accept-Encoding")
+	for _, offer := range offers {
+		for _, spec := range specs {
+			if spec.Q > bestQ &&
+				(spec.Value == "*" || spec.Value == offer) {
+				bestQ = spec.Q
+				bestOffer = offer
+			}
+		}
+	}
+	if bestQ == 0 {
+		bestOffer = ""
+	}
+	return bestOffer
+}
+
+// acceptSpec describes an Accept* header.
+type acceptSpec struct {
+	Value string
+	Q     float64
+}
+
+// parseAccept parses Accept* headers.
+func parseAccept(header http.Header, key string) (specs []acceptSpec) {
+loop:
+	for _, s := range header[key] {
+		for {
+			var spec acceptSpec
+			spec.Value, s = expectTokenSlash(s)
+			if spec.Value == "" {
+				continue loop
+			}
+			spec.Q = 1.0
+			s = skipSpace(s)
+			if strings.HasPrefix(s, ";") {
+				s = skipSpace(s[1:])
+				if !strings.HasPrefix(s, "q=") {
+					continue loop
+				}
+				spec.Q, s = expectQuality(s[2:])
+				if spec.Q < 0.0 {
+					continue loop
+				}
+			}
+			specs = append(specs, spec)
+			s = skipSpace(s)
+			if !strings.HasPrefix(s, ",") {
+				continue loop
+			}
+			s = skipSpace(s[1:])
+		}
+	}
+	return
+}
+
+func skipSpace(s string) (rest string) {
+	i := 0
+	for ; i < len(s); i++ {
+		if octetTypes[s[i]]&isSpace == 0 {
+			break
+		}
+	}
+	return s[i:]
+}
+
+func expectTokenSlash(s string) (token, rest string) {
+	i := 0
+	for ; i < len(s); i++ {
+		b := s[i]
+		if (octetTypes[b]&isToken == 0) && b != '/' {
+			break
+		}
+	}
+	return s[:i], s[i:]
+}
+
+func expectQuality(s string) (q float64, rest string) {
+	switch {
+	case len(s) == 0:
+		return -1, ""
+	case s[0] == '0':
+		q = 0
+	case s[0] == '1':
+		q = 1
+	default:
+		return -1, ""
+	}
+	s = s[1:]
+	if !strings.HasPrefix(s, ".") {
+		return q, s
+	}
+	s = s[1:]
+	i := 0
+	n := 0
+	d := 1
+	for ; i < len(s); i++ {
+		b := s[i]
+		if b < '0' || b > '9' {
+			break
+		}
+		n = n*10 + int(b) - '0'
+		d *= 10
+	}
+	return q + float64(n)/float64(d), s[i:]
+}
+
+// Octet types from RFC 2616.
+var octetTypes [256]octetType
+
+type octetType byte
+
+const (
+	isToken octetType = 1 << iota
+	isSpace
+)
+
+func init() {
+	// OCTET      = <any 8-bit sequence of data>
+	// CHAR       = <any US-ASCII character (octets 0 - 127)>
+	// CTL        = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
+	// CR         = <US-ASCII CR, carriage return (13)>
+	// LF         = <US-ASCII LF, linefeed (10)>
+	// SP         = <US-ASCII SP, space (32)>
+	// HT         = <US-ASCII HT, horizontal-tab (9)>
+	// <">        = <US-ASCII double-quote mark (34)>
+	// CRLF       = CR LF
+	// LWS        = [CRLF] 1*( SP | HT )
+	// TEXT       = <any OCTET except CTLs, but including LWS>
+	// separators = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" | "\" | <">
+	//              | "/" | "[" | "]" | "?" | "=" | "{" | "}" | SP | HT
+	// token      = 1*<any CHAR except CTLs or separators>
+	// qdtext     = <any TEXT except <">>
+
+	for c := 0; c < 256; c++ {
+		var t octetType
+		isCtl := c <= 31 || c == 127
+		isChar := 0 <= c && c <= 127
+		isSeparator := strings.IndexRune(" \t\"(),/:;<=>?@[]\\{}", rune(c)) >= 0
+		if strings.IndexRune(" \t\r\n", rune(c)) >= 0 {
+			t |= isSpace
+		}
+		if isChar && !isCtl && !isSeparator {
+			t |= isToken
+		}
+		octetTypes[c] = t
+	}
+}

writer.go

@@ -1,12 +1,8 @@
 package brotli
 
 import (
-	"compress/gzip"
 	"errors"
 	"io"
-	"net/http"
-
-	"github.com/golang/gddo/httputil"
 )
 
 const (
@@ -125,32 +121,3 @@ type nopCloser struct {
 }
 
 func (nopCloser) Close() error { return nil }
-
-// HTTPCompressor chooses a compression method (brotli, gzip, or none) based on
-// the Accept-Encoding header, sets the Content-Encoding header, and returns a
-// WriteCloser that implements that compression. The Close method must be called
-// before the current HTTP handler returns.
-//
-// Due to https://github.com/golang/go/issues/31753, the response will not be
-// compressed unless you set a Content-Type header before you call
-// HTTPCompressor.
-func HTTPCompressor(w http.ResponseWriter, r *http.Request) io.WriteCloser {
-	if w.Header().Get("Content-Type") == "" {
-		return nopCloser{w}
-	}
-
-	if w.Header().Get("Vary") == "" {
-		w.Header().Set("Vary", "Accept-Encoding")
-	}
-
-	encoding := httputil.NegotiateContentEncoding(r, []string{"br", "gzip"})
-	switch encoding {
-	case "br":
-		w.Header().Set("Content-Encoding", "br")
-		return NewWriter(w)
-	case "gzip":
-		w.Header().Set("Content-Encoding", "gzip")
-		return gzip.NewWriter(w)
-	}
-	return nopCloser{w}
-}