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Daniel Stenberg 2001-04-27 14:46:17 +00:00
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103
docs/INTERNALS
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@ -1,4 +1,4 @@
Updated for curl 7.7 on March 13, 2001
Updated for curl 7.7.2 on April 26, 2001
_ _ ____ _
___| | | | _ \| |
/ __| | | | |_) | |
@ -73,7 +73,7 @@ Library
makes sure we stay absolutely platform independent.
curl_easy_init() allocates an internal struct and makes some initializations.
The returned handle does not revail internals.
The returned handle does not reveal internals.
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
@ -81,33 +81,68 @@ Library
curl_easy_perform() does a whole lot of things:
It starts off in the lib/easy.c file by calling curl_transfer(), but the main
work is lib/url.c. The function first 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.
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
Curl_connect() to connect to the remote site.
When connected, 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).
o Curl_connect()
The protocol-specific functions of course deal with protocol-specific
negotiations and setup. They have access to the Curl_sendf() (from
lib/sendf.c) function to send printf-style formatted data to the remote host
and when they're ready to make the actual file transfer they call the
Curl_Transfer() function (in lib/transfer.c) to setup the transfer and
returns. Curl_perform() then calls Transfer() in lib/transfer.c that performs
the entire file transfer. Curl_perform() is what does the main "connect - do
- transfer - done" loop. It loops if there's a Location: to follow.
... 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.
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
called). The speedcheck functions in lib/speedcheck.c are also used to verify
that the transfer is as fast as required.
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.
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).
The protocol-specific functions of course deal with protocol-specific
negotiations and setup. They have access to the Curl_sendf() (from
lib/sendf.c) function to send printf-style formatted data to the remote
host and when they're ready to make the actual file transfer they call the
Curl_Transfer() function (in lib/transfer.c) to setup the transfer and
returns.
o 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
called). The speedcheck functions in lib/speedcheck.c are also used to
verify that the transfer is as fast as required.
o Curl_done()
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().
o Curl_disconnect()
During normal connection 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.
This function cleans up all resources that are associated with a single
connection.
Curl_perform() is the function that does the main "connect - do - transfer -
done" loop. It loops if there's a Location: to follow.
When completed, the curl_easy_cleanup() should be called to free up used
resources.
resources. It runs Curl_disconnect() on all open connectons.
A quick roundup on internal function sequences (many of these call
protocol-specific function-pointers):
@ -257,6 +292,7 @@ Client
======
main() resides in src/main.c together with most of the client code.
src/hugehelp.c is automatically generated by the mkhelp.pl perl script to
display the complete "manual" and the src/urlglob.c file holds the functions
used for the URL-"globbing" support. Globbing in the sense that the {} and []
@ -272,25 +308,26 @@ Client
curl_easy_getinfo() function to extract useful information from the curl
session.
Recent versions may loop and do all that several times if many URLs were
Recent versions may loop and do all this several times if many URLs were
specified on the command line or config file.
Memory Debugging
================
The file named lib/memdebug.c contains debug-versions of a few
functions. Functions such as malloc, free, fopen, fclose, etc that somehow
deal with resources that might give us problems if we "leak" them. The
functions in the memdebug system do nothing fancy, they do their normal
function and then log information about what they just did. The logged data
can then be analyzed after a complete session,
The file lib/memdebug.c contains debug-versions of a few functions. Functions
such as malloc, free, fopen, fclose, etc that somehow deal with resources
that might give us problems if we "leak" them. The functions in the memdebug
system do nothing fancy, they do their normal function and then log
information about what they just did. The logged data can then be analyzed
after a complete session,
memanalyze.pl is a perl script present only present in CVS (not part of the
memanalyze.pl is the perl script present only present in CVS (not part of the
release archives) that analyzes a log file generated by the memdebug
system. It detects if resources are allocated but never freed and other kinds
of errors related to resource management.
Use -DMALLOCDEBUG when compiling to enable memory debugging.
Use -DMALLOCDEBUG when compiling to enable memory debugging, this is also
switched on by running configure with --enable-debug.
Test Suite
==========