From 4be64dd369b4bbdf3c4c0972c949c6e150377699 Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rosehogenson@posteo.net>
Date: Fri, 21 Nov 2025 17:12:34 -0800
Subject: Use a weird encoding for the time.Time
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This way we can save 19 whole bytes per request 😲
---
 roseh.moe.go | 61 ++++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 47 insertions(+), 14 deletions(-)

(limited to 'roseh.moe.go')

diff --git a/roseh.moe.go b/roseh.moe.go
index 5c88422..64d5e83 100644
--- a/roseh.moe.go
+++ b/roseh.moe.go
@@ -346,25 +346,59 @@ func verify(msg []byte) ([]byte, bool) {
 	return msg, true
 }
 
-func makeToken() (string, error) {
-	b, err := time.Now().MarshalBinary()
-	if err != nil {
-		return "", err
+func marshalInt(x int64) []byte {
+	ux := uint64(x) << 1
+	if x < 0 {
+		ux = ^ux
+	}
+	buf := make([]byte, 8)
+	binary.BigEndian.PutUint64(buf, ux)
+	for len(buf) > 0 && buf[0] == 0 {
+		buf = buf[1:]
+	}
+	return buf
+}
+
+func unmarshalInt(b []byte) (int64, bool) {
+	if len(b) > 8 {
+		return 0, false
+	}
+	buf := make([]byte, 8)
+	copy(buf[8-len(b):], b)
+	ux := binary.BigEndian.Uint64(buf)
+	x := int64(ux >> 1)
+	if ux&1 != 0 {
+		x = ^x
+	}
+	return x, true
+}
+
+const yearOffset = 2089
+
+func marshalTime(t time.Time) []byte {
+	year, month, day := t.UTC().Date()
+	return marshalInt((int64(year)-yearOffset)<<9 | int64(month)<<5 | int64(day))
+}
+
+func unmarshalTime(b []byte) (time.Time, bool) {
+	n, ok := unmarshalInt(b)
+	if !ok {
+		return time.Time{}, false
 	}
-	return base64.RawURLEncoding.EncodeToString(sign(b)), nil
+	return time.Date(int(n>>9+yearOffset), time.Month(n>>5&0xf), int(n&0x1f), 0, 0, 0, 0, time.UTC), true
+}
+
+func makeToken() string {
+	return base64.RawURLEncoding.EncodeToString(sign(marshalTime(time.Now())))
 }
 
 const cookieExpiration = 7 * 24 * time.Hour
 const authCookieName = "roseh.moe.auth"
 
-func attachCookie(w http.ResponseWriter) error {
-	token, err := makeToken()
-	if err != nil {
-		return err
-	}
+func attachCookie(w http.ResponseWriter) {
 	http.SetCookie(w, &http.Cookie{
 		Name:        authCookieName,
-		Value:       token,
+		Value:       makeToken(),
 		Path:        "/",
 		Domain:      *domain,
 		Expires:     time.Now().Add(cookieExpiration),
@@ -373,7 +407,6 @@ func attachCookie(w http.ResponseWriter) error {
 		SameSite:    http.SameSiteStrictMode,
 		Partitioned: true,
 	})
-	return nil
 }
 
 func cookieAuth(w http.ResponseWriter, r *http.Request) bool {
@@ -389,8 +422,8 @@ func cookieAuth(w http.ResponseWriter, r *http.Request) bool {
 	if !ok {
 		return false
 	}
-	var t time.Time
-	if err := t.UnmarshalBinary(msg); err != nil {
+	t, ok := unmarshalTime(msg)
+	if !ok {
 		return false
 	}
 	cookieAge := time.Since(t)
-- 
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