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updated, improved language at a few places

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Daniel Stenberg 2001-05-29 13:23:41 +00:00
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commit de16ddd5b4
1 changed files with 41 additions and 26 deletions
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67
docs/INTERNALS
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@ -1,4 +1,4 @@
Updated for curl 7.7.2 on April 26, 2001
Updated for curl 7.8 on May 29, 2001
_ _ ____ _
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/ __| | | | |_) | |
@ -69,20 +69,29 @@ Library
rather small and easy-to-follow. All the ones prefixed with 'curl_easy' are
put in the lib/easy.c file.
Starting with libcurl 7.8, curl_global_init_() and curl_global_cleanup() were
introduced. They should be called by the application to initialize and clean
up global stuff in the library. As of today, they just do the global SSL
initing if SSL is enabled. libcurl itself has no "global" scope.
All printf()-style functions use the supplied clones in lib/mprintf.c. This
makes sure we stay absolutely platform independent.
curl_easy_init() allocates an internal struct and makes some initializations.
The returned handle does not reveal internals.
The returned handle does not reveal internals. This is the 'UrlData' struct
which works as a global "anchor" struct. All connections performed will get
connect-specific data allocated that should be used for things related to
particular connections/requests.
curl_easy_setopt() takes a three arguments, where the option stuff must be
passed in pairs, the parameter-ID and the parameter-value. The list of
options is documented in the man page.
curl_easy_setopt() takes three arguments, where the option stuff must be
passed in pairs: the parameter-ID and the parameter-value. The list of
options is documented in the man page. This function mainly sets things in
the 'UrlData' struct.
curl_easy_perform() does a whole lot of things:
It starts off in the lib/easy.c file by calling Curl_perform() and the main
work then continues lib/url.c. The flow continues with a call to
work then continues in lib/url.c. The flow continues with a call to
Curl_connect() to connect to the remote site.
o Curl_connect()
@ -94,12 +103,18 @@ Library
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.
This function makes sure there's an allocated and initiated 'connectdata'
struct that is used for this particular connection only (although there may
be several requests performed on the same connect). A bunch of things are
inited/inherited from the UrlData struct.
o Curl_do()
Curl_do() makes sure the proper protocol-specific function is called. The
functions are named after the protocols they handle. Curl_ftp(),
Curl_http(), Curl_dict(), etc. They all reside in their respective files
(ftp.c, http.c and dict.c).
(ftp.c, http.c and dict.c). HTTPS is handled by Curl_http() and FTPS by
Curl_ftp().
The protocol-specific functions of course deal with protocol-specific
negotiations and setup. They have access to the Curl_sendf() (from
@ -123,17 +138,18 @@ Library
Called after a transfer is done. This function takes care of everything
that has to be done after a transfer. This function attempts to leave
matters in a state so that Curl_do() should be possible to call again on
the same connection (in a persistent connection case). It may also soon be
closed with Curl_disconnect().
the same connection (in a persistent connection case). It might also soon
be closed with Curl_disconnect().
o Curl_disconnect()
During normal connection and transfers, no one ever tries to close any
When doing normal connections and transfers, no one ever tries to close any
connection so this is not normally called when curl_easy_perform() is
used. This function is only used when we are certain that no more transfers
is going to be made on the connection (it can be also closed by
force). This function can also be called at times to make sure that libcurl
doesn't keep too many connections alive at the same time.
is going to be made on the connection. It can be also closed by force, or
it can be called to make sure that libcurl doesn't keep too many
connections alive at the same time (there's a default amount of 5 but that
can be changed with the CURLOPT_MAXCONNECTS option).
This function cleans up all resources that are associated with a single
connection.
@ -239,26 +255,26 @@ Library
Persistent Connections
======================
With curl 7.7, we added persistent connection support to libcurl which has
introduced a somewhat different treatmeant of things inside of libcurl.
The persistent connection support in libcurl requires some considerations on
how to do things inside of the library.
o The 'UrlData' struct returned in the curl_easy_init() call must never
hold connection-oriented data. It is meant to hold the root data as well
as all the options etc that the library-user may choose.
o The 'UrlData' struct holds the cache array of pointers to 'connectdata'
structs. There's one connectdata struct for each connection that libcurl
knows about.
o The 'UrlData' 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 in pre-7.7 versions.
something that was illegal before libcurl 7.7.
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
already when we add a new connection, we close one of the present ones. We
select which one to close dependent on the close policy that may have been
previously set.
o When the tranfer 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 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.
You do realize that the curl handle must be re-used in order for the
@ -268,10 +284,9 @@ Library Symbols
===============
All symbols used internally in libcurl must use a 'Curl_' prefix if they're
used in more than a single file. Single-file symbols must be made
static. Public (exported) symbols must use a 'curl_' prefix. (There are
exceptions, but they are destined to be changed to follow this pattern in the
future.)
used in more than a single file. Single-file symbols must be made static.
Public ("exported") symbols must use a 'curl_' prefix. (There are exceptions,
but they are to be changed to follow this pattern in future versions.)
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