Introducing a new persistent connection caching system using "bundles".

A bundle is a list of all persistent connections to the same host.
The connection cache consists of a hash of bundles, with the
hostname as the key.
The benefits may not be obvious, but they are two:

1) Faster search for connections to reuse, since the hash
   lookup only finds connections to the host in question.
2) It lays out the groundworks for an upcoming patch,
   which will introduce multiple HTTP pipelines.

This patch also removes the awkward list of "closure handles",
which were needed to send QUIT commands to the FTP server
when closing a connection.
Now we allocate a separate closure handle and use that
one to close all connections.

This has been tested in a live system for a few weeks, and of
course passes the test suite.

1 files changed, 56 insertions, 0 deletions

diff --git a/lib/conncache.h b/lib/conncache.h
new file mode 100644
index 000000000..a6e1af70c
--- /dev/null
+++ b/lib/conncache.h
@@ -0,0 +1,56 @@
+#ifndef __CONNCACHE_H
+#define __CONNCACHE_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2012, Linus Nielsen Feltzing, <linus@haxx.se>
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+struct conncache {
+  struct curl_hash *hash;
+  enum {
+    CONNCACHE_PRIVATE, /* used for an easy handle alone */
+    CONNCACHE_MULTI    /* shared within a multi handle */
+  } type;
+  size_t num_connections;
+};
+
+struct conncache *Curl_conncache_init(int type);
+
+void Curl_conncache_destroy(struct conncache *connc);
+
+struct connectbundle *Curl_conncache_find_bundle(struct conncache *connc,
+                                                 char *hostname);
+
+CURLcode Curl_conncache_add_conn(struct conncache *connc,
+                                 struct connectdata *conn);
+
+void Curl_conncache_remove_conn(struct conncache *connc,
+                                struct connectdata *conn);
+
+void Curl_conncache_foreach(struct conncache *connc,
+                            void *param,
+                            void (*func)(void *, void *));
+
+struct connectdata *
+Curl_conncache_find_first_connection(struct conncache *connc);
+
+void Curl_conncache_print(struct conncache *connc);
+
+#endif /* __CONNCACHE_H */