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slightly less outdated

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Daniel Stenberg 2007-11-26 11:02:45 +00:00
parent d59841618d
commit dc11239ff1
1 changed files with 23 additions and 20 deletions
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43
docs/INTERNALS
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@ -97,7 +97,9 @@ Library
... analyzes the URL, it separates the different components and connects to
the remote host. This may involve using a proxy and/or using SSL. The
Curl_gethost() function in lib/hostip.c is used for looking up host names.
Curl_resolv() function in lib/hostip.c is used for looking up host names
(it does then use the proper underlying method, which may vary between
platforms and builds).
When Curl_connect is done, we are connected to the remote site. Then it is
time to tell the server to get a document/file. Curl_do() arranges this.
@ -122,17 +124,20 @@ Library
Curl_Transfer() function (in lib/transfer.c) to setup the transfer and
returns.
Starting in 7.9.1, if this DO function fails and the connection is being
re-used, libcurl will then close this connection, setup a new connection
and re-issue the DO request on that. This is because there is no way to be
perfectly sure that we have discovered a dead connection before the DO
function and thus we might wrongly be re-using a connection that was closed
by the remote peer.
If this DO function fails and the connection is being re-used, libcurl will
then close this connection, setup a new connection and re-issue the DO
request on that. This is because there is no way to be perfectly sure that
we have discovered a dead connection before the DO function and thus we
might wrongly be re-using a connection that was closed by the remote peer.
Some time during the DO function, the Curl_setup_transfer() function must
be called with some basic info about the upcoming transfer: what socket(s)
to read/write and the expected file tranfer sizes (if known).
o Transfer()
Curl_perform() then calls Transfer() in lib/transfer.c that performs
the entire file transfer.
Curl_perform() then calls Transfer() in lib/transfer.c that performs the
entire file transfer.
During transfer, the progress functions in lib/progress.c are called at a
frequent interval (or at the user's choice, a specified callback might get
@ -236,9 +241,8 @@ Library
URL encoding and decoding, called escaping and unescaping in the source code,
is found in lib/escape.c.
While transfering data in Transfer() a few functions might get
used. curl_getdate() in lib/getdate.c is for HTTP date comparisons (and
more).
While transfering data in Transfer() a few functions might get used.
curl_getdate() in lib/parsedate.c is for HTTP date comparisons (and more).
lib/getenv.c offers curl_getenv() which is for reading environment variables
in a neat platform independent way. That's used in the client, but also in
@ -254,10 +258,6 @@ Library
A function named curl_version() that returns the full curl version string is
found in lib/version.c.
If authentication is requested but no password is given, a getpass_r() clone
exists in lib/getpass.c. libcurl offers a custom callback that can be used
instead of this, but it doesn't change much to us.
Persistent Connections
======================
@ -269,9 +269,11 @@ Persistent Connections
all the options etc that the library-user may choose.
o The 'SessionHandle' struct holds the "connection cache" (an array of
pointers to 'connectdata' structs). There's one connectdata struct
allocated for each connection that libcurl knows about.
o This also enables the 'curl handle' to be reused on subsequent transfers,
something that was illegal before libcurl 7.7.
allocated for each connection that libcurl knows about. Note that when you
use the multi interface, the multi handle will hold the connection cache
and not the particular easy handle. This of course to allow all easy handles
in a multi stack to be able to share and re-use connections.
o This enables the 'curl handle' to be reused on subsequent transfers.
o When we are about to perform a transfer with curl_easy_perform(), we first
check for an already existing connection in the cache that we can use,
otherwise we create a new one and add to the cache. If the cache is full
@ -281,7 +283,8 @@ Persistent Connections
o When the transfer operation is complete, we try to leave the connection
open. Particular options may tell us not to, and protocols may signal
closure on connections and then we don't keep it open of course.
o When curl_easy_cleanup() is called, we close all still opened connections.
o When curl_easy_cleanup() is called, we close all still opened connections,
unless of course the multi interface "owns" the connections.
You do realize that the curl handle must be re-used in order for the
persistent connections to work.