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[svn] Improved comments for the persistent connections feature.

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hniksic 2000-11-20 02:20:39 -08:00
parent 6f7fd37186
commit 7302e69dc2
1 changed files with 20 additions and 7 deletions
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27
src/http.c
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@ -264,27 +264,28 @@ http_process_connection (const char *hdr, void *arg)
return 1; return 1;
} }
/* Persistent connections (pc). Currently, we cache the most recently /* Persistent connections. Currently, we cache the most recently used
used connection as persistent, provided that the HTTP server agrees connection as persistent, provided that the HTTP server agrees to
to make it such. The persistence data is stored in the variables make it such. The persistence data is stored in the variables
below. Ideally, it would be in a structure, and it should be below. Ideally, it would be in a structure, and it should be
possible to cache an arbitrary fixed number of these connections. possible to cache an arbitrary fixed number of these connections.
I think the code is quite easy to extend in that direction. */ I think the code is quite easy to extend in that direction. */
/* Whether the persistent connection is active. */ /* Whether a persistent connection is active. */
static int pc_active_p; static int pc_active_p;
/* Host and port of the last persistent connection. */ /* Host and port of currently active persistent connection. */
static unsigned char pc_last_host[4]; static unsigned char pc_last_host[4];
static unsigned short pc_last_port; static unsigned short pc_last_port;
/* File descriptor of the last persistent connection. */ /* File descriptor of the currently active persistent connection. */
static int pc_last_fd; static int pc_last_fd;
/* Mark the persistent connection as invalid. This is used by the /* Mark the persistent connection as invalid. This is used by the
CLOSE_* macros after they forcefully close a registered persistent CLOSE_* macros after they forcefully close a registered persistent
connection. */ connection. This does not close the file descriptor -- it is left
to the caller to do that. (Maybe it should, though.) */
static void static void
invalidate_persistent (void) invalidate_persistent (void)
@ -343,16 +344,28 @@ static int
persistent_available_p (const char *host, unsigned short port) persistent_available_p (const char *host, unsigned short port)
{ {
unsigned char this_host[4]; unsigned char this_host[4];
/* First, check whether a persistent connection is active at all. */
if (!pc_active_p) if (!pc_active_p)
return 0; return 0;
/* Second, check if the active connection pertains to the correct
(HOST, PORT) ordered pair. */
if (port != pc_last_port) if (port != pc_last_port)
return 0; return 0;
if (!store_hostaddress (this_host, host)) if (!store_hostaddress (this_host, host))
return 0; return 0;
if (memcmp (pc_last_host, this_host, 4)) if (memcmp (pc_last_host, this_host, 4))
return 0; return 0;
/* Third: check whether the connection is still open. This is
important because most server implement a liberal (short) timeout
on persistent connections. Wget can of course always reconnect
if the connection doesn't work out, but it's nicer to know in
advance. This test is a logical followup of the first test, but
is "expensive" and therefore placed at the end of the list. */
if (!test_socket_open (pc_last_fd)) if (!test_socket_open (pc_last_fd))
{ {
/* Oops, the socket is no longer open. Now that we know that,
let's invalidate the persistent connection before returning
0. */
CLOSE (pc_last_fd); CLOSE (pc_last_fd);
invalidate_persistent (); invalidate_persistent ();
return 0; return 0;