brought up-to-date and extended

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

===============

 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

 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

=======

 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.

 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.

 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).

 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.

 While transfering, the progress functions in lib/progress.c are called at a

 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 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. curl_transfer() then calls _Tranfer() 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.

 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)

 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

 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

 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.

 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.

 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.