http: add http.SetCookie(ResponseWriter, *Cookie)

R=golang-dev, gary.burd, rsc
CC=golang-dev
https://golang.org/cl/4526062

src/pkg/http/cookie.go

@@ -130,6 +130,37 @@ func readSetCookies(h Header) []*Cookie {
 	return cookies
 }
 
+// SetCookie adds a Set-Cookie header to the provided ResponseWriter's headers.
+func SetCookie(w ResponseWriter, cookie *Cookie) {
+	var b bytes.Buffer
+	writeSetCookieToBuffer(&b, cookie)
+	w.Header().Add("Set-Cookie", b.String())
+}
+
+func writeSetCookieToBuffer(buf *bytes.Buffer, c *Cookie) {
+	fmt.Fprintf(buf, "%s=%s", sanitizeName(c.Name), sanitizeValue(c.Value))
+	if len(c.Path) > 0 {
+		fmt.Fprintf(buf, "; Path=%s", sanitizeValue(c.Path))
+	}
+	if len(c.Domain) > 0 {
+		fmt.Fprintf(buf, "; Domain=%s", sanitizeValue(c.Domain))
+	}
+	if len(c.Expires.Zone) > 0 {
+		fmt.Fprintf(buf, "; Expires=%s", c.Expires.Format(time.RFC1123))
+	}
+	if c.MaxAge > 0 {
+		fmt.Fprintf(buf, "; Max-Age=%d", c.MaxAge)
+	} else if c.MaxAge < 0 {
+		fmt.Fprintf(buf, "; Max-Age=0")
+	}
+	if c.HttpOnly {
+		fmt.Fprintf(buf, "; HttpOnly")
+	}
+	if c.Secure {
+		fmt.Fprintf(buf, "; Secure")
+	}
+}
+
 // writeSetCookies writes the wire representation of the set-cookies
 // to w. Each cookie is written on a separate "Set-Cookie: " line.
 // This choice is made because HTTP parsers tend to have a limit on
@@ -142,27 +173,7 @@ func writeSetCookies(w io.Writer, kk []*Cookie) os.Error {
 	var b bytes.Buffer
 	for _, c := range kk {
 		b.Reset()
-		fmt.Fprintf(&b, "%s=%s", sanitizeName(c.Name), sanitizeValue(c.Value))
-		if len(c.Path) > 0 {
-			fmt.Fprintf(&b, "; Path=%s", sanitizeValue(c.Path))
-		}
-		if len(c.Domain) > 0 {
-			fmt.Fprintf(&b, "; Domain=%s", sanitizeValue(c.Domain))
-		}
-		if len(c.Expires.Zone) > 0 {
-			fmt.Fprintf(&b, "; Expires=%s", c.Expires.Format(time.RFC1123))
-		}
-		if c.MaxAge > 0 {
-			fmt.Fprintf(&b, "; Max-Age=%d", c.MaxAge)
-		} else if c.MaxAge < 0 {
-			fmt.Fprintf(&b, "; Max-Age=0")
-		}
-		if c.HttpOnly {
-			fmt.Fprintf(&b, "; HttpOnly")
-		}
-		if c.Secure {
-			fmt.Fprintf(&b, "; Secure")
-		}
+		writeSetCookieToBuffer(&b, c)
 		lines = append(lines, "Set-Cookie: "+b.String()+"\r\n")
 	}
 	sort.SortStrings(lines)

src/pkg/http/cookie_test.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"fmt"
 	"json"
+	"os"
 	"reflect"
 	"testing"
 )
@@ -43,6 +44,35 @@ func TestWriteSetCookies(t *testing.T) {
 	}
 }
 
+type headerOnlyResponseWriter Header
+
+func (ho headerOnlyResponseWriter) Header() Header {
+	return Header(ho)
+}
+
+func (ho headerOnlyResponseWriter) Write([]byte) (int, os.Error) {
+	panic("NOIMPL")
+}
+
+func (ho headerOnlyResponseWriter) WriteHeader(int) {
+	panic("NOIMPL")
+}
+
+func TestSetCookie(t *testing.T) {
+	m := make(Header)
+	SetCookie(headerOnlyResponseWriter(m), &Cookie{Name: "cookie-1", Value: "one", Path: "/restricted/"})
+	SetCookie(headerOnlyResponseWriter(m), &Cookie{Name: "cookie-2", Value: "two", MaxAge: 3600})
+	if l := len(m["Set-Cookie"]); l != 2 {
+		t.Fatalf("expected %d cookies, got %d", 2, l)
+	}
+	if g, e := m["Set-Cookie"][0], "cookie-1=one; Path=/restricted/"; g != e {
+		t.Errorf("cookie #1: want %q, got %q", e, g)
+	}
+	if g, e := m["Set-Cookie"][1], "cookie-2=two; Max-Age=3600"; g != e {
+		t.Errorf("cookie #2: want %q, got %q", e, g)
+	}
+}
+
 var writeCookiesTests = []struct {
 	Cookies []*Cookie
 	Raw     string