header.go

package sessions

import (
	"net/http"
	"net/textproto"
	"strings"
)

type Header interface {
	Get(key string) string
	Values(key string) []string
	Add(key, value string)
	Set(key, value string)
}

func ReadCookie(h Header, name string) (*http.Cookie, error) {
	for _, c := range readCookies(h, name) {
		return c, nil
	}
	return nil, http.ErrNoCookie
}

// SetCookie adds a Set-Cookie header to the provided ResponseWriter's headers.
// The provided cookie must have a valid Name. Invalid cookies may be
// silently dropped.
func SetCookie(w Header, cookie *http.Cookie) {
	if v := cookie.String(); v != "" {
		w.Add("Set-Cookie", v)
	}
}

// readCookies parses all "Cookie" values from the header h and
// returns the successfully parsed Cookies.
//
// if filter isn't empty, only cookies of that name are returned
func readCookies(h Header, filter string) []*http.Cookie {
	lines := h.Values("Cookie")
	if len(lines) == 0 {
		return []*http.Cookie{}
	}

	cookies := make([]*http.Cookie, 0, len(lines)+strings.Count(lines[0], ";"))
	for _, line := range lines {
		line = textproto.TrimString(line)

		var part string
		for len(line) > 0 { // continue since we have rest
			if splitIndex := strings.Index(line, ";"); splitIndex > 0 {
				part, line = line[:splitIndex], line[splitIndex+1:]
			} else {
				part, line = line, ""
			}
			part = textproto.TrimString(part)
			if len(part) == 0 {
				continue
			}
			name, val := part, ""
			if j := strings.Index(part, "="); j >= 0 {
				name, val = name[:j], name[j+1:]
			}
			if !isCookieNameValid(name) {
				continue
			}
			if filter != "" && filter != name {
				continue
			}
			val, ok := parseCookieValue(val, true)
			if !ok {
				continue
			}
			cookies = append(cookies, &http.Cookie{Name: name, Value: val})
		}
	}
	return cookies
}

func parseCookieValue(raw string, allowDoubleQuote bool) (string, bool) {
	// Strip the quotes, if present.
	if allowDoubleQuote && len(raw) > 1 && raw[0] == '"' && raw[len(raw)-1] == '"' {
		raw = raw[1 : len(raw)-1]
	}
	for i := 0; i < len(raw); i++ {
		if !validCookieValueByte(raw[i]) {
			return "", false
		}
	}
	return raw, true
}
func validCookieValueByte(b byte) bool {
	return 0x20 <= b && b < 0x7f && b != '"' && b != ';' && b != '\\'
}