(#1554) Add support for all common compressions (write and read)

- Remove the context.Context interface and export the *context, the iris.Context now points to the pointer\nSupport compression and rate limiting in the FileServer\nBit of code organisation


Former-commit-id: ad1c61bf968059510c6be9e7f2cceec7da70ba17

context/accept_header.go

@@ -0,0 +1,206 @@
+package context
+
+import "strings"
+
+func negotiationMatch(in []string, priorities []string) string {
+	// e.g.
+	// match json:
+	// 	in: text/html, application/json
+	// 	prioritities: application/json
+	// not match:
+	// 	in: text/html, application/json
+	// 	prioritities: text/xml
+	// match html:
+	// 	in: text/html, application/json
+	// 	prioritities: */*
+	// not match:
+	// 	in: application/json
+	// 	prioritities: text/xml
+	// match json:
+	// 	in: text/html, application/*
+	// 	prioritities: application/json
+
+	if len(priorities) == 0 {
+		return ""
+	}
+
+	if len(in) == 0 {
+		return priorities[0]
+	}
+
+	for _, accepted := range in {
+		for _, p := range priorities {
+			// wildcard is */* or text/* and etc.
+			// so loop through each char.
+			for i, n := 0, len(accepted); i < n; i++ {
+				if accepted[i] != p[i] {
+					break
+				}
+
+				if accepted[i] == '*' || p[i] == '*' {
+					return p
+				}
+
+				if i == n-1 {
+					return p
+				}
+			}
+		}
+	}
+
+	return ""
+}
+
+func negotiateAcceptHeader(in []string, offers []string, bestOffer string) string {
+	if bestOffer == "" {
+		bestOffer = IDENTITY
+	}
+
+	bestQ := -1.0
+	specs := parseAccept(in)
+	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(in []string) (specs []acceptSpec) {
+loop:
+	for _, s := range in {
+		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
+	}
+}