[PATCH] Sending remaining TTL in "read"'s response

[Nicolás Lichtmaier]

In order to implement some local caching before memcached, and to 
properly handle expirations, it would be nice if the remaining TTL could 
be sent to the client. So, the client knows "this value is fresh and can 
be used for another 3601 seconds". This patch is a sample 
implementation, it just adds the remaining ttl to the end of the get's 
response. What do you think? Is this feature worthwhile?

Thanks!
PS: The protocol is not very expansible, adding a value there can be 
risky. I've tested this with PHP's memcache client library and it seems 
to work Ok.

diff -ubBr memcached-1.2.2/items.c memcached-1.2.2.new/items.c
--- memcached-1.2.2/items.c	2007-05-02 19:58:51.000000000 -0300
+++ memcached-1.2.2.new/items.c	2007-12-04 00:27:30.000000000 -0300
@@ -67,7 +67,7 @@
 static size_t item_make_header(const uint8_t nkey, const int flags, const int nbytes,
                      char *suffix, uint8_t *nsuffix) {
     /* suffix is defined at 40 chars elsewhere.. */
-    *nsuffix = (uint8_t) snprintf(suffix, 40, " %d %d\r\n", flags, nbytes - 2);
+    *nsuffix = (uint8_t) snprintf(suffix, 40, " %d %d", flags, nbytes - 2);
     return sizeof(item) + nkey + *nsuffix + nbytes;
 }
 
diff -ubBr memcached-1.2.2/memcached.c memcached-1.2.2.new/memcached.c
--- memcached-1.2.2/memcached.c	2007-05-02 19:58:51.000000000 -0300
+++ memcached-1.2.2.new/memcached.c	2007-12-04 00:29:15.000000000 -0300
@@ -1053,6 +1053,7 @@
     int i = 0;
     item *it;
     token_t *key_token = &tokens[KEY_TOKEN];
+    char ttlstr[20];
 
     assert(c != NULL);
 
@@ -1096,6 +1097,8 @@
                     } else break;
                 }
 
+                sprintf(ttlstr, " %u\r\n", it->exptime - current_time);
+
                 /*
                  * Construct the response. Each hit adds three elements to the
                  * outgoing data list:
@@ -1105,7 +1108,9 @@
                  */
                 if (add_iov(c, "VALUE ", 6) != 0 ||
                     add_iov(c, ITEM_key(it), it->nkey) != 0 ||
-                    add_iov(c, ITEM_suffix(it), it->nsuffix + it->nbytes) != 0)
+                    add_iov(c, ITEM_suffix(it), it->nsuffix) != 0 ||
+                    add_iov(c, ttlstr, strlen(ttlstr)) != 0 ||
+                    add_iov(c, ITEM_suffix(it) + it->nsuffix, it->nbytes) != 0)
                     {
                         break;
                     }