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Daniel Stenberg 2001-01-17 14:17:49 +00:00
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docs/INTERNALS
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@ -14,14 +14,13 @@ INTERNALS
SYMBOLS
=======
All symbols used internally must use a 'Curl_' prefix if they're used in
more than a single file. Single file symbols must be made static. Public
symbols must use a 'curl_' prefix. (There are exceptions, but they are
destined to change to this pattern in the future.)
All symbols used internally 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.)
CVS
===
All changes to the sources are committed to the CVS repository as soon as
they're somewhat verified to work. Changes shall be commited as independently
as possible so that individual changes can be easier spotted and tracked
@ -34,7 +33,7 @@ Windows vs Unix
===============
There are a few differences in how to program curl the unix way compared to
the Windows way. The four most notable details are:
the Windows way. The four perhaps most notable details are:
1. Different function names for close(), read(), write()
2. Windows requires a couple of init calls for the socket stuff
@ -61,6 +60,9 @@ Windows vs Unix
supposed to look exactly as a config.h file would have looked like on a
Windows machine!
Generally speaking: always remember that this will be compiled on dozens of
operating systems. Don't walk on the edge.
Library
=======
@ -75,6 +77,9 @@ Library
rather small and easy-to-follow. All the ones prefixed with 'curl_easy' are
put in the lib/easy.c file.
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 revail internals.
@ -84,27 +89,31 @@ Library
curl_easy_perform() does a whole lot of things:
The function analyzes the URL, get the different components and connects to
the remote host. This may involve using a proxy and/or using SSL. The
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_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.
When connected, the proper function is called. The functions are named after
the protocols they handle. ftp(), http(), dict(), etc. They all reside in
their respective files (ftp.c, http.c and dict.c).
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).
The protocol-specific functions deal with protocol-specific negotiations and
setup. They have access to the 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 Transfer() function (in
lib/download.c) to do the transfer. All printf()-style functions use the
supplied clones in lib/mprintf.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. curl_transfer() then calls _Tranfer() in lib/transfer.c that
performs the entire file transfer.
While transfering, the progress functions in lib/progress.c are called at a
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 completed curl_easy_cleanup() should be called to free up used
When completed, the curl_easy_cleanup() should be called to free up used
resources.
HTTP(S)
@ -113,9 +122,8 @@ Library
code. There is a special file (lib/formdata.c) that offers all the multipart
post functions.
base64-functions for user+password stuff is in (lib/base64.c) and all
functions for parsing and sending cookies are found in
(lib/cookie.c).
base64-functions for user+password stuff (and more) is in (lib/base64.c) and
all functions for parsing and sending cookies are found in (lib/cookie.c).
HTTPS uses in almost every means the same procedure as HTTP, with only two
exceptions: the connect procedure is different and the function used to read
@ -125,9 +133,17 @@ Library
FTP
The if2ip() function can be used for getting the IP number of a specified
network interface, and it resides in lib/if2ip.c. It is only used for the FTP
PORT command.
The Curl_if2ip() function can be used for getting the IP number of a
specified network interface, and it resides in lib/if2ip.c.
Curl_ftpsendf() is used for sending FTP commands to the remote server. It was
made a separate function to prevent us programmers from forgetting that they
must be CRLF terminated. They must also be sent in one single write() to make
firewalls and similar happy.
Kerberos
The kerberos support is mainly in lib/krb4.c and lib/security.c.
TELNET
@ -146,32 +162,54 @@ 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
While transfering data in _Transfer() a few functions might get
used. curl_getdate() in lib/getdate.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
lib/url.c when checking the proxy environment variables.
lib/url.c when checking the proxy environment variables. Note that contrary
to the normal unix getenv(), this returns an allocated buffer that must be
free()ed after use.
lib/netrc.c holds the .netrc parser
lib/timeval.c features replacement functions for systems that don't have
gettimeofday().
gettimeofday() and a few support functions for timeval convertions.
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.
Return Codes and Informationals
===============================
I've made things simple. Almost every function in libcurl returns a CURLcode,
that must be CURLE_OK if everything is OK or otherwise a suitable error code
as the curl/curl.h include file defines. The very spot that detects an error
must use the Curl_failf() function to set the human-readable error
description.
In aiding the user to understand what's happening and to debug curl usage, we
must supply a fair amount of informational messages by using the Curl_infof()
function. Those messages are only displayed when the user explicitly asks for
them. They are best used when revealing information that isn't otherwise
obvious.
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 multiple-URL support.
used for the URL-"globbing" support. Globbing in the sense that the {} and []
expansion stuff is there.
The client mostly mess around to setup its config struct properly, then it
calls the curl_easy_*() functions of the library and when it gets back
The client mostly messes around to setup its 'config' struct properly, then
it calls the curl_easy_*() functions of the library and when it gets back
control after the curl_easy_perform() it cleans up the library, checks status
and exits.
@ -180,10 +218,30 @@ 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
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
is then analyzed after a complete session,
memanalyze.pl is a perl script present only 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.
Test Suite
==========
During November 2000, a test suite has evolved. It is placed in its own
Since November 2000, a test suite has evolved. It is placed in its own
subdirectory directly off the root in the curl archive tree, and it contains
a bunch of scripts and a lot of test case data.
@ -193,3 +251,17 @@ Test Suite
You'll find a complete description of the test case data files in the README
file in the test directory.
The test suite automatically detects if curl was built with the memory
debugging enabled, and if it was it will detect memory leaks too.
Building Releases
=================
There's no magic to this. When you consider everything stable enough to be
released, run the 'maketgz' script (using 'make distcheck' will give you a
pretty good view on the status of the current sources). maketgz prompts for
version number of the client and the library before it creates a release
archive.
You must have autoconf installed to build release archives.