./configure --without-ssl
If you have OpenSSL installed, but with the libraries in one place and the
-header files somewhere else, you have to set the LDFLAGS and CPPFLAGS
+header files somewhere else, you have to set the `LDFLAGS` and `CPPFLAGS`
environment variables prior to running configure. Something like this should
work:
KB140584 is a must for any Windows developer. Especially important is full
understanding if you are not going to follow the advice given above.
- - [How To Use the C Run-Time](https://support.microsoft.com/kb/94248/en-us)
- - [Run-Time Library Compiler Options](https://docs.microsoft.com/en-us/cpp/build/reference/md-mt-ld-use-run-time-library)
- - [Potential Errors Passing CRT Objects Across DLL Boundaries](https://msdn.microsoft.com/en-us/library/ms235460)
+ - [How To Use the C Run-Time](https://support.microsoft.com/help/94248/how-to-use-the-c-run-time)
+ - [Run-Time Library Compiler Options](https://docs.microsoft.com/cpp/build/reference/md-mt-ld-use-run-time-library)
+ - [Potential Errors Passing CRT Objects Across DLL Boundaries](https://docs.microsoft.com/cpp/c-runtime-library/potential-errors-passing-crt-objects-across-dll-boundaries)
If your app is misbehaving in some strange way, or it is suffering from
memory corruption, before asking for further help, please try first to
and SSPI support.
If you have any problems linking libraries or finding header files, be sure
-to verify that the provided "Makefile.m32" files use the proper paths, and
+to verify that the provided `Makefile.m32` files use the proper paths, and
adjust as necessary. It is also possible to override these paths with
environment variables, for example:
## Cygwin
Almost identical to the unix installation. Run the configure script in the
-curl source tree root with `sh configure`. Make sure you have the sh
-executable in /bin/ or you'll see the configure fail toward the end.
+curl source tree root with `sh configure`. Make sure you have the `sh`
+executable in `/bin/` or you'll see the configure fail toward the end.
Run `make`
If you want to set any of these defines you have the following options:
- - Modify lib/config-win32.h
- - Modify lib/curl_setup.h
- - Modify winbuild/Makefile.vc
+ - Modify `lib/config-win32.h`
+ - Modify `lib/curl_setup.h`
+ - Modify `winbuild/Makefile.vc`
- Modify the "Preprocessor Definitions" in the libcurl project
Note: The pre-processor settings can be found using the Visual Studio IDE
## Using BSD-style lwIP instead of Winsock TCP/IP stack in Win32 builds
In order to compile libcurl and curl using BSD-style lwIP TCP/IP stack it is
-necessary to make definition of preprocessor symbol USE_LWIPSOCK visible to
+necessary to make definition of preprocessor symbol `USE_LWIPSOCK` visible to
libcurl and curl compilation processes. To set this definition you have the
following alternatives:
- - Modify lib/config-win32.h and src/config-win32.h
- - Modify winbuild/Makefile.vc
+ - Modify `lib/config-win32.h` and `src/config-win32.h`
+ - Modify `winbuild/Makefile.vc`
- Modify the "Preprocessor Definitions" in the libcurl project
Note: The pre-processor settings can be found using the Visual Studio IDE
## Legacy Windows and SSL
-WinSSL (specifically Schannel from Windows SSPI), is the native SSL library in
-Windows. However, WinSSL in Windows <= XP is unable to connect to servers that
+Schannel (from Windows SSPI), is the native SSL library in Windows. However,
+Schannel in Windows <= XP is unable to connect to servers that
no longer support the legacy handshakes and algorithms used by those
versions. If you will be using curl in one of those earlier versions of
Windows you should choose another SSL backend such as OpenSSL.
-# Apple iOS and Mac OS X
+# Apple iOS and macOS
On modern Apple operating systems, curl can be built to use Apple's SSL/TLS
implementation, Secure Transport, instead of OpenSSL. To build with Secure
OS. The `--cert` and `--engine` options, and their libcurl equivalents, are
currently unimplemented in curl with Secure Transport.
-For OS X users: In OS X 10.8 ("Mountain Lion"), Apple made a major overhaul to
-the Secure Transport API that, among other things, added support for the newer
-TLS 1.1 and 1.2 protocols. To get curl to support TLS 1.1 and 1.2, you must
-build curl on Mountain Lion or later, or by using the equivalent SDK. If you
-set the `MACOSX_DEPLOYMENT_TARGET` environmental variable to an earlier
-version of OS X prior to building curl, then curl will use the new Secure
+For macOS users: In OS X 10.8 ("Mountain Lion"), Apple made a major overhaul
+to the Secure Transport API that, among other things, added support for the
+newer TLS 1.1 and 1.2 protocols. To get curl to support TLS 1.1 and 1.2, you
+must build curl on Mountain Lion or later, or by using the equivalent SDK. If
+you set the `MACOSX_DEPLOYMENT_TARGET` environmental variable to an earlier
+version of macOS prior to building curl, then curl will use the new Secure
Transport API on Mountain Lion and later, and fall back on the older API when
the same curl binary is executed on older cats. For example, running these
commands in curl's directory in the shell will build the code such that it
Download and unpack the curl package.
-'cd' to the new directory. (e.g. `cd curl-7.12.3`)
+`cd` to the new directory. (e.g. `cd curl-7.12.3`)
Set environment variables to point to the cross-compile toolchain and call
configure with any options you need. Be sure and specify the `--host` and
There are a number of configure options that can be used to reduce the size of
libcurl for embedded applications where binary size is an important factor.
-First, be sure to set the CFLAGS variable when configuring with any relevant
+First, be sure to set the `CFLAGS` variable when configuring with any relevant
compiler optimization flags to reduce the size of the binary. For gcc, this
would mean at minimum the -Os option, and potentially the `-march=X`,
`-mdynamic-no-pic` and `-flto` options as well, e.g.
The GNU compiler and linker have a number of options that can reduce the
size of the libcurl dynamic libraries on some platforms even further.
-Specify them by providing appropriate CFLAGS and LDFLAGS variables on the
-configure command-line, e.g.
+Specify them by providing appropriate `CFLAGS` and `LDFLAGS` variables on
+the configure command-line, e.g.
CFLAGS="-Os -ffunction-sections -fdata-sections
-fno-unwind-tables -fno-asynchronous-unwind-tables -flto"
Note that the curl test harness can detect the use of some, but not all, of
the `--disable` statements suggested above. Use will cause tests relying on
those features to fail. The test harness can be manually forced to skip the
-relevant tests by specifying certain key words on the runtests.pl command
+relevant tests by specifying certain key words on the `runtests.pl` command
line. Following is a list of appropriate key words:
- `--disable-cookies` !cookies
- [`curl_off_t`](#curl_off_t)
- [curlx](#curlx)
- [Content Encoding](#contentencoding)
- - [hostip.c explained](#hostip)
+ - [`hostip.c` explained](#hostip)
- [Track Down Memory Leaks](#memoryleak)
- [`multi_socket`](#multi_socket)
- [Structs in libcurl](#structs)
Portability
===========
- We write curl and libcurl to compile with C89 compilers. On 32bit and up
+ We write curl and libcurl to compile with C89 compilers. On 32-bit and up
machines. Most of libcurl assumes more or less POSIX compliance but that's
not a requirement.
- GNU M4 1.4
- perl 5.004
- roffit 0.5
- - groff ? (any version that supports "groff -Tps -man [in] [out]")
+ - groff ? (any version that supports `groff -Tps -man [in] [out]`)
- ps2pdf (gs) ?
<a name="winvsunix"></a>
In curl, this is solved with defines and macros, so that the source looks
the same in all places except for the header file that defines them. The
- macros in use are sclose(), sread() and swrite().
+ macros in use are `sclose()`, `sread()` and `swrite()`.
2. Windows requires a couple of init calls for the socket stuff.
There are plenty of entry points to the library, namely each publicly defined
function that libcurl offers to applications. All of those functions are
rather small and easy-to-follow. All the ones prefixed with `curl_easy` are
- put in the lib/easy.c file.
+ put in the `lib/easy.c` file.
`curl_global_init()` and `curl_global_cleanup()` should be called by the
application to initialize and clean up global stuff in the library. As of
today, it can handle the global SSL initing if SSL is enabled and it can init
the socket layer on windows machines. libcurl itself has no "global" scope.
- All printf()-style functions use the supplied clones in lib/mprintf.c. This
+ All printf()-style functions use the supplied clones in `lib/mprintf.c`. This
makes sure we stay absolutely platform independent.
[ `curl_easy_init()`][2] allocates an internal struct and makes some
`curl_multi_wait()`, and `curl_multi_perform()` until the transfer is done
and then returns.
- Some of the most important key functions in url.c are called from multi.c
- when certain key steps are to be made in the transfer operation.
+ Some of the most important key functions in `url.c` are called from
+ `multi.c` when certain key steps are to be made in the transfer operation.
<a name="Curl_connect"></a>
Curl_connect()
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_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).
+ `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.
- This function makes sure there's an allocated and initiated 'connectdata'
+ 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 `Curl_easy` struct.
multi_do()
---------
- `multi_do()` makes sure the proper protocol-specific function is called. The
- functions are named after the protocols they handle.
+ `multi_do()` makes sure the proper protocol-specific function is called.
+ The functions are named after the protocols they handle.
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
+ `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_setup_transfer()` function (in lib/transfer.c) to setup the transfer
- and returns.
+ `Curl_setup_transfer()` function (in `lib/transfer.c`) to setup the
+ transfer and returns.
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
Called during the transfer of the actual protocol payload.
- During transfer, the progress functions in lib/progress.c are called at
+ During transfer, the progress functions in `lib/progress.c` are called at
frequent intervals (or at the user's choice, a specified callback might get
- called). The speedcheck functions in lib/speedcheck.c are also used to
+ called). The speedcheck functions in `lib/speedcheck.c` are also used to
verify that the transfer is as fast as required.
<a name="multi_done"></a>
=======
HTTP offers a lot and is the protocol in curl that uses the most lines of
- code. There is a special file (lib/formdata.c) that offers all the multipart
- post functions.
+ code. There is a special file `lib/formdata.c` that offers all the
+ multipart post functions.
- 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).
+ 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 case the same procedure as HTTP, with only two
exceptions: the connect procedure is different and the function used to read
===
The `Curl_if2ip()` function can be used for getting the IP number of a
- specified network interface, and it resides in lib/if2ip.c.
+ 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.
+ they must be CRLF terminated. They must also be sent in one single `write()`
+ to make firewalls and similar happy.
<a name="kerberos"></a>
Kerberos
========
- Kerberos support is mainly in lib/krb5.c and lib/security.c but also
+ Kerberos support is mainly in `lib/krb5.c` and `lib/security.c` but also
`curl_sasl_sspi.c` and `curl_sasl_gssapi.c` for the email protocols and
`socks_gssapi.c` and `socks_sspi.c` for SOCKS5 proxy specifics.
TELNET
======
- Telnet is implemented in lib/telnet.c.
+ Telnet is implemented in `lib/telnet.c`.
<a name="file"></a>
FILE
====
- The file:// protocol is dealt with in lib/file.c.
+ The `file://` protocol is dealt with in `lib/file.c`.
<a name="smb"></a>
SMB
===
- The smb:// protocol is dealt with in lib/smb.c.
+ The `smb://` protocol is dealt with in `lib/smb.c`.
<a name="ldap"></a>
LDAP
====
- Everything LDAP is in lib/ldap.c and lib/openldap.c
+ Everything LDAP is in `lib/ldap.c` and `lib/openldap.c`.
<a name="email"></a>
E-mail
======
- The e-mail related source code is in lib/imap.c, lib/pop3.c and lib/smtp.c.
+ The e-mail related source code is in `lib/imap.c`, `lib/pop3.c` and
+ `lib/smtp.c`.
<a name="general"></a>
General
=======
URL encoding and decoding, called escaping and unescaping in the source code,
- is found in lib/escape.c.
+ is found in `lib/escape.c`.
- While transferring data in Transfer() a few functions might get used.
- `curl_getdate()` in lib/parsedate.c is for HTTP date comparisons (and more).
+ While transferring 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
+ `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. Note that
- contrary to the normal unix getenv(), this returns an allocated buffer that
- must be free()ed after use.
+ also in `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/netrc.c` holds the `.netrc` parser.
- lib/timeval.c features replacement functions for systems that don't have
- gettimeofday() and a few support functions for timeval conversions.
+ `lib/timeval.c` features replacement functions for systems that don't have
+ `gettimeofday()` and a few support functions for timeval conversions.
A function named `curl_version()` that returns the full curl version string
- is found in lib/version.c.
+ is found in `lib/version.c`.
<a name="persistent"></a>
Persistent Connections
as well as all the options etc that the library-user may choose.
- The `Curl_easy` struct holds the "connection cache" (an array of
- pointers to 'connectdata' structs).
+ pointers to `connectdata` structs).
- This enables the 'curl handle' to be reused on subsequent transfers.
in future libcurl versions.
To deal with this internally in the best way possible, we have a generic SSL
- function API as provided by the vtls/vtls.[ch] system, and they are the only
+ function API as provided by the `vtls/vtls.[ch]` system, and they are the only
SSL functions we must use from within libcurl. vtls is then crafted to use
the appropriate lower-level function calls to whatever SSL library that is in
- use. For example vtls/openssl.[ch] for the OpenSSL library.
+ use. For example `vtls/openssl.[ch]` for the OpenSSL library.
<a name="symbols"></a>
Library Symbols
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
+ 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.
Client
======
- main() resides in `src/tool_main.c`.
+ `main()` resides in `src/tool_main.c`.
- `src/tool_hugehelp.c` is automatically generated by the mkhelp.pl perl script
- to display the complete "manual" and the `src/tool_urlglob.c` file holds the
- functions used for the URL-"globbing" support. Globbing in the sense that the
- {} and [] expansion stuff is there.
+ `src/tool_hugehelp.c` is automatically generated by the `mkhelp.pl` perl
+ script to display the complete "manual" and the `src/tool_urlglob.c` file
+ holds the functions used for the URL-"globbing" support. Globbing in the
+ sense that the `{}` and `[]` expansion stuff is there.
- The client mostly sets up its 'config' struct properly, then
+ The client mostly sets up 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.
- When the operation is done, the ourWriteOut() function in src/writeout.c may
- be called to report about the operation. That function is using the
+ When the operation is done, the `ourWriteOut()` function in `src/writeout.c`
+ may be called to report about the operation. That function is using the
`curl_easy_getinfo()` function to extract useful information from the curl
session.
Memory Debugging
================
- 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,
+ 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 the perl script present in tests/ that analyzes a log file
- generated by the memory tracking system. It detects if resources are
+ `memanalyze.pl` is the perl script present in `tests/` that analyzes a log
+ file generated by the memory tracking system. It detects if resources are
allocated but never freed and other kinds of errors related to resource
management.
- Internally, definition of preprocessor symbol DEBUGBUILD restricts code which
- is only compiled for debug enabled builds. And symbol CURLDEBUG is used to
- differentiate code which is _only_ used for memory tracking/debugging.
+ Internally, definition of preprocessor symbol `DEBUGBUILD` restricts code
+ which is only compiled for debug enabled builds. And symbol `CURLDEBUG` is
+ used to differentiate code which is _only_ used for memory
+ tracking/debugging.
- Use -DCURLDEBUG when compiling to enable memory debugging, this is also
- switched on by running configure with --enable-curldebug. Use -DDEBUGBUILD
- when compiling to enable a debug build or run configure with --enable-debug.
+ Use `-DCURLDEBUG` when compiling to enable memory debugging, this is also
+ switched on by running configure with `--enable-curldebug`. Use
+ `-DDEBUGBUILD` when compiling to enable a debug build or run configure with
+ `--enable-debug`.
- curl --version will list 'Debug' feature for debug enabled builds, and
+ `curl --version` will list 'Debug' feature for debug enabled builds, and
will list 'TrackMemory' feature for curl debug memory tracking capable
builds. These features are independent and can be controlled when running
- the configure script. When --enable-debug is given both features will be
+ the configure script. When `--enable-debug` is given both features will be
enabled, unless some restriction prevents memory tracking from being used.
<a name="test"></a>
curl archive tree, and it contains a bunch of scripts and a lot of test case
data.
- The main test script is runtests.pl that will invoke test servers like
- httpserver.pl and ftpserver.pl before all the test cases are performed. The
- test suite currently only runs on Unix-like platforms.
+ The main test script is `runtests.pl` that will invoke test servers like
+ `httpserver.pl` and `ftpserver.pl` before all the test cases are performed.
+ The test suite currently only runs on Unix-like platforms.
- You'll find a description of the test suite in the tests/README file, and the
- test case data files in the tests/FILEFORMAT file.
+ You'll find a description of the test suite in the `tests/README` file, and
+ the test case data files in the `tests/FILEFORMAT` file.
The test suite automatically detects if curl was built with the memory
debugging enabled, and if it was, it will detect memory leaks, too.
prevent linking errors later on). Then I simply build the areslib project
(the other projects adig/ahost seem to fail under MSVC).
- Next was libcurl. I opened lib/config-win32.h and I added a:
+ Next was libcurl. I opened `lib/config-win32.h` and I added a:
`#define USE_ARES 1`
Next thing I did was I added the path for the ares includes to the include
Lastly, I also changed libcurl to be single-threaded rather than
multi-threaded, again this was to prevent some duplicate symbol errors. I'm
not sure why I needed to change everything to single-threaded, but when I
- didn't I got redefinition errors for several CRT functions (malloc, stricmp,
- etc.)
+ didn't I got redefinition errors for several CRT functions (`malloc()`,
+ `stricmp()`, etc.)
<a name="curl_off_t"></a>
`curl_off_t`
`curl_off_t` is a data type provided by the external libcurl include
headers. It is the type meant to be used for the [`curl_easy_setopt()`][1]
- options that end with LARGE. The type is 64bit large on most modern
+ options that end with LARGE. The type is 64-bit large on most modern
platforms.
<a name="curlx"></a>
additional functions.
We provide them through a single header file for easy access for apps:
- "curlx.h"
+ `curlx.h`
`curlx_strtoofft()`
-------------------
A macro that converts a string containing a number to a `curl_off_t` number.
This might use the `curlx_strtoll()` function which is provided as source
code in strtoofft.c. Note that the function is only provided if no
- strtoll() (or equivalent) function exist on your platform. If `curl_off_t`
- is only a 32 bit number on your platform, this macro uses strtol().
+ `strtoll()` (or equivalent) function exist on your platform. If `curl_off_t`
+ is only a 32-bit number on your platform, this macro uses `strtol()`.
Future
------
[HTTP/1.1][4] specifies that a client may request that a server encode its
response. This is usually used to compress a response using one (or more)
encodings from a set of commonly available compression techniques. These
- schemes include 'deflate' (the zlib algorithm), 'gzip' 'br' (brotli) and
- 'compress'. A client requests that the server perform an encoding by including
- an Accept-Encoding header in the request document. The value of the header
- should be one of the recognized tokens 'deflate', ... (there's a way to
+ schemes include `deflate` (the zlib algorithm), `gzip`, `br` (brotli) and
+ `compress`. A client requests that the server perform an encoding by including
+ an `Accept-Encoding` header in the request document. The value of the header
+ should be one of the recognized tokens `deflate`, ... (there's a way to
register new schemes/tokens, see sec 3.5 of the spec). A server MAY honor
the client's encoding request. When a response is encoded, the server
- includes a Content-Encoding header in the response. The value of the
- Content-Encoding header indicates which encodings were used to encode the
+ includes a `Content-Encoding` header in the response. The value of the
+ `Content-Encoding` header indicates which encodings were used to encode the
data, in the order in which they were applied.
It's also possible for a client to attach priorities to different schemes so
that the server knows which it prefers. See sec 14.3 of RFC 2616 for more
- information on the Accept-Encoding header. See sec [3.1.2.2 of RFC 7231][15]
- for more information on the Content-Encoding header.
+ information on the `Accept-Encoding` header. See sec
+ [3.1.2.2 of RFC 7231][15] for more information on the `Content-Encoding`
+ header.
## Supported content encodings
- The 'deflate', 'gzip' and 'br' content encodings are supported by libcurl.
+ The `deflate`, `gzip` and `br` content encodings are supported by libcurl.
Both regular and chunked transfers work fine. The zlib library is required
- for the 'deflate' and 'gzip' encodings, while the brotli decoding library is
- for the 'br' encoding.
+ for the `deflate` and `gzip` encodings, while the brotli decoding library is
+ for the `br` encoding.
## The libcurl interface
[`curl_easy_setopt`][1](curl, [`CURLOPT_ACCEPT_ENCODING`][5], string)
- where string is the intended value of the Accept-Encoding header.
+ where string is the intended value of the `Accept-Encoding` header.
Currently, libcurl does support multiple encodings but only
- understands how to process responses that use the "deflate", "gzip" and/or
- "br" content encodings, so the only values for [`CURLOPT_ACCEPT_ENCODING`][5]
- that will work (besides "identity," which does nothing) are "deflate",
- "gzip" and "br". If a response is encoded using the "compress" or methods,
+ understands how to process responses that use the `deflate`, `gzip` and/or
+ `br` content encodings, so the only values for [`CURLOPT_ACCEPT_ENCODING`][5]
+ that will work (besides `identity`, which does nothing) are `deflate`,
+ `gzip` and `br`. If a response is encoded using the `compress` or methods,
libcurl will return an error indicating that the response could
- not be decoded. If `<string>` is NULL no Accept-Encoding header is generated.
- If `<string>` is a zero-length string, then an Accept-Encoding header
- containing all supported encodings will be generated.
+ not be decoded. If `<string>` is NULL no `Accept-Encoding` header is
+ generated. If `<string>` is a zero-length string, then an `Accept-Encoding`
+ header containing all supported encodings will be generated.
The [`CURLOPT_ACCEPT_ENCODING`][5] must be set to any non-NULL value for
content to be automatically decoded. If it is not set and the server still
sends encoded content (despite not having been asked), the data is returned
- in its raw form and the Content-Encoding type is not checked.
+ in its raw form and the `Content-Encoding` type is not checked.
## The curl interface
- Use the [--compressed][6] option with curl to cause it to ask servers to
+ Use the [`--compressed`][6] option with curl to cause it to ask servers to
compress responses using any format supported by curl.
<a name="hostip"></a>
-hostip.c explained
-==================
+`hostip.c` explained
+====================
- The main compile-time defines to keep in mind when reading the host*.c source
- file are these:
+ The main compile-time defines to keep in mind when reading the `host*.c`
+ source file are these:
## `CURLRES_IPV6`
- this host has getaddrinfo() and family, and thus we use that. The host may
+ this host has `getaddrinfo()` and family, and thus we use that. The host may
not be able to resolve IPv6, but we don't really have to take that into
account. Hosts that aren't IPv6-enabled have `CURLRES_IPV4` defined.
## `CURLRES_ARES`
is defined if libcurl is built to use c-ares for asynchronous name
- resolves. This can be Windows or *nix.
+ resolves. This can be Windows or \*nix.
## `CURLRES_THREADED`
libcurl is not built to use an asynchronous resolver, `CURLRES_SYNCH` is
defined.
-## host*.c sources
+## `host*.c` sources
- The host*.c sources files are split up like this:
+ The `host*.c` sources files are split up like this:
- - hostip.c - method-independent resolver functions and utility functions
- - hostasyn.c - functions for asynchronous name resolves
- - hostsyn.c - functions for synchronous name resolves
- - asyn-ares.c - functions for asynchronous name resolves using c-ares
- - asyn-thread.c - functions for asynchronous name resolves using threads
- - hostip4.c - IPv4 specific functions
- - hostip6.c - IPv6 specific functions
+ - `hostip.c` - method-independent resolver functions and utility functions
+ - `hostasyn.c` - functions for asynchronous name resolves
+ - `hostsyn.c` - functions for synchronous name resolves
+ - `asyn-ares.c` - functions for asynchronous name resolves using c-ares
+ - `asyn-thread.c` - functions for asynchronous name resolves using threads
+ - `hostip4.c` - IPv4 specific functions
+ - `hostip6.c` - IPv6 specific functions
- The hostip.h is the single united header file for all this. It defines the
- `CURLRES_*` defines based on the config*.h and `curl_setup.h` defines.
+ The `hostip.h` is the single united header file for all this. It defines the
+ `CURLRES_*` defines based on the `config*.h` and `curl_setup.h` defines.
<a name="memoryleak"></a>
Track Down Memory Leaks
than one thread. If you want/need to use it in a multi-threaded app. Please
adjust accordingly.
-
## Build
- Rebuild libcurl with -DCURLDEBUG (usually, rerunning configure with
- --enable-debug fixes this). 'make clean' first, then 'make' so that all
+ Rebuild libcurl with `-DCURLDEBUG` (usually, rerunning configure with
+ `--enable-debug` fixes this). `make clean` first, then `make` so that all
files are actually rebuilt properly. It will also make sense to build
- libcurl with the debug option (usually -g to the compiler) so that debugging
- it will be easier if you actually do find a leak in the library.
+ libcurl with the debug option (usually `-g` to the compiler) so that
+ debugging it will be easier if you actually do find a leak in the library.
This will create a library that has memory debugging enabled.
## Analyze the Flow
- Use the tests/memanalyze.pl perl script to analyze the dump file:
+ Use the `tests/memanalyze.pl` perl script to analyze the dump file:
tests/memanalyze.pl dump
Implementation of the `curl_multi_socket` API
- The main ideas of this API are simply:
-
- 1 - The application can use whatever event system it likes as it gets info
- from libcurl about what file descriptors libcurl waits for what action
- on. (The previous API returns `fd_sets` which is very select()-centric).
-
- 2 - When the application discovers action on a single socket, it calls
- libcurl and informs that there was action on this particular socket and
- libcurl can then act on that socket/transfer only and not care about
- any other transfers. (The previous API always had to scan through all
- the existing transfers.)
-
- The idea is that [`curl_multi_socket_action()`][7] calls a given callback
- with information about what socket to wait for what action on, and the
- callback only gets called if the status of that socket has changed.
-
- We also added a timer callback that makes libcurl call the application when
- the timeout value changes, and you set that with [`curl_multi_setopt()`][9]
- and the [`CURLMOPT_TIMERFUNCTION`][10] option. To get this to work,
- Internally, there's an added struct to each easy handle in which we store
- an "expire time" (if any). The structs are then "splay sorted" so that we
- can add and remove times from the linked list and yet somewhat swiftly
- figure out both how long there is until the next nearest timer expires
- and which timer (handle) we should take care of now. Of course, the upside
- of all this is that we get a [`curl_multi_timeout()`][8] that should also
- work with old-style applications that use [`curl_multi_perform()`][11].
-
- We created an internal "socket to easy handles" hash table that given
- a socket (file descriptor) returns the easy handle that waits for action on
- that socket. This hash is made using the already existing hash code
- (previously only used for the DNS cache).
-
- To make libcurl able to report plain sockets in the socket callback, we had
- to re-organize the internals of the [`curl_multi_fdset()`][12] etc so that
- the conversion from sockets to `fd_sets` for that function is only done in
- the last step before the data is returned. I also had to extend c-ares to
- get a function that can return plain sockets, as that library too returned
- only `fd_sets` and that is no longer good enough. The changes done to c-ares
- are available in c-ares 1.3.1 and later.
+ The main ideas of this API are simply:
+
+ 1. The application can use whatever event system it likes as it gets info
+ from libcurl about what file descriptors libcurl waits for what action
+ on. (The previous API returns `fd_sets` which is very
+ `select()`-centric).
+
+ 2. When the application discovers action on a single socket, it calls
+ libcurl and informs that there was action on this particular socket and
+ libcurl can then act on that socket/transfer only and not care about
+ any other transfers. (The previous API always had to scan through all
+ the existing transfers.)
+
+ The idea is that [`curl_multi_socket_action()`][7] calls a given callback
+ with information about what socket to wait for what action on, and the
+ callback only gets called if the status of that socket has changed.
+
+ We also added a timer callback that makes libcurl call the application when
+ the timeout value changes, and you set that with [`curl_multi_setopt()`][9]
+ and the [`CURLMOPT_TIMERFUNCTION`][10] option. To get this to work,
+ Internally, there's an added struct to each easy handle in which we store
+ an "expire time" (if any). The structs are then "splay sorted" so that we
+ can add and remove times from the linked list and yet somewhat swiftly
+ figure out both how long there is until the next nearest timer expires
+ and which timer (handle) we should take care of now. Of course, the upside
+ of all this is that we get a [`curl_multi_timeout()`][8] that should also
+ work with old-style applications that use [`curl_multi_perform()`][11].
+
+ We created an internal "socket to easy handles" hash table that given
+ a socket (file descriptor) returns the easy handle that waits for action on
+ that socket. This hash is made using the already existing hash code
+ (previously only used for the DNS cache).
+
+ To make libcurl able to report plain sockets in the socket callback, we had
+ to re-organize the internals of the [`curl_multi_fdset()`][12] etc so that
+ the conversion from sockets to `fd_sets` for that function is only done in
+ the last step before the data is returned. I also had to extend c-ares to
+ get a function that can return plain sockets, as that library too returned
+ only `fd_sets` and that is no longer good enough. The changes done to c-ares
+ are available in c-ares 1.3.1 and later.
<a name="structs"></a>
Structs in libcurl
## Curl_easy
The `Curl_easy` struct is the one returned to the outside in the external API
- as a "CURL *". This is usually known as an easy handle in API documentations
+ as a `CURL *`. This is usually known as an easy handle in API documentations
and examples.
Information and state that is related to the actual connection is in the
- 'connectdata' struct. When a transfer is about to be made, libcurl will
+ `connectdata` struct. When a transfer is about to be made, libcurl will
either create a new connection or re-use an existing one. The particular
connectdata that is used by this handle is pointed out by
`Curl_easy->easy_conn`.
Data and information that regard this particular single transfer is put in
- the SingleRequest sub-struct.
+ the `SingleRequest` sub-struct.
When the `Curl_easy` struct is added to a multi handle, as it must be in
- order to do any transfer, the ->multi member will point to the `Curl_multi`
- struct it belongs to. The ->prev and ->next members will then be used by the
- multi code to keep a linked list of `Curl_easy` structs that are added to
- that same multi handle. libcurl always uses multi so ->multi *will* point to
- a `Curl_multi` when a transfer is in progress.
+ order to do any transfer, the `->multi` member will point to the `Curl_multi`
+ struct it belongs to. The `->prev` and `->next` members will then be used by
+ the multi code to keep a linked list of `Curl_easy` structs that are added to
+ that same multi handle. libcurl always uses multi so `->multi` *will* point
+ to a `Curl_multi` when a transfer is in progress.
- ->mstate is the multi state of this particular `Curl_easy`. When
+ `->mstate` is the multi state of this particular `Curl_easy`. When
`multi_runsingle()` is called, it will act on this handle according to which
state it is in. The mstate is also what tells which sockets to return for a
specific `Curl_easy` when [`curl_multi_fdset()`][12] is called etc.
- The libcurl source code generally use the name 'data' for the variable that
+ The libcurl source code generally use the name `data` for the variable that
points to the `Curl_easy`.
When doing multiplexed HTTP/2 transfers, each `Curl_easy` is associated with
re-use an existing one instead of creating a new as it creates a significant
performance boost.
- Each 'connectdata' identifies a single physical connection to a server. If
+ Each `connectdata` identifies a single physical connection to a server. If
the connection can't be kept alive, the connection will be closed after use
and then this struct can be removed from the cache and freed.
Thus, the same `Curl_easy` can be used multiple times and each time select
- another connectdata struct to use for the connection. Keep this in mind, as
- it is then important to consider if options or choices are based on the
+ another `connectdata` struct to use for the connection. Keep this in mind,
+ as it is then important to consider if options or choices are based on the
connection or the `Curl_easy`.
- Functions in libcurl will assume that connectdata->data points to the
+ Functions in libcurl will assume that `connectdata->data` points to the
`Curl_easy` that uses this connection (for the moment).
As a special complexity, some protocols supported by libcurl require a
this single struct and thus can be considered a single connection for most
internal concerns.
- The libcurl source code generally use the name 'conn' for the variable that
+ The libcurl source code generally use the name `conn` for the variable that
points to the connectdata.
<a name="Curl_multi"></a>
Internally, the easy interface is implemented as a wrapper around multi
interface functions. This makes everything multi interface.
- `Curl_multi` is the multi handle struct exposed as "CURLM *" in external
+ `Curl_multi` is the multi handle struct exposed as `CURLM *` in external
APIs.
This struct holds a list of `Curl_easy` structs that have been added to this
`->conn_cache` points to the connection cache. It keeps track of all
connections that are kept after use. The cache has a maximum size.
- `->closure_handle` is described in the 'connectdata' section.
+ `->closure_handle` is described in the `connectdata` section.
- The libcurl source code generally use the name 'multi' for the variable that
+ The libcurl source code generally use the name `multi` for the variable that
points to the `Curl_multi` struct.
<a name="Curl_handler"></a>
Each unique protocol that is supported by libcurl needs to provide at least
one `Curl_handler` struct. It defines what the protocol is called and what
functions the main code should call to deal with protocol specific issues.
- In general, there's a source file named [protocol].c in which there's a
- "struct `Curl_handler` `Curl_handler_[protocol]`" declared. In url.c there's
+ In general, there's a source file named `[protocol].c` in which there's a
+ `struct Curl_handler Curl_handler_[protocol]` declared. In `url.c` there's
then the main array with all individual `Curl_handler` structs pointed to
from a single array which is scanned through when a URL is given to libcurl
to work with.
`->setup_connection` is called to allow the protocol code to allocate
protocol specific data that then gets associated with that `Curl_easy` for
the rest of this transfer. It gets freed again at the end of the transfer.
- It will be called before the 'connectdata' for the transfer has been
+ It will be called before the `connectdata` for the transfer has been
selected/created. Most protocols will allocate its private
- 'struct [PROTOCOL]' here and assign `Curl_easy->req.protop` to point to it.
+ `struct [PROTOCOL]` here and assign `Curl_easy->req.protop` to point to it.
`->connect_it` allows a protocol to do some specific actions after the TCP
connect is done, that can still be considered part of the connection phase.
limit which "direction" of socket actions that the main engine will
concern itself with.
- - `PROTOPT_NONETWORK` - a protocol that doesn't use network (read file:)
+ - `PROTOPT_NONETWORK` - a protocol that doesn't use network (read `file:`)
- `PROTOPT_NEEDSPWD` - this protocol needs a password and will use a default
one unless one is provided
## Curl_share
The libcurl share API allocates a `Curl_share` struct, exposed to the
- external API as "CURLSH *".
+ external API as `CURLSH *`.
The idea is that the struct can have a set of its own versions of caches and
pools and then by providing this struct in the `CURLOPT_SHARE` option, those
## CookieInfo
This is the main cookie struct. It holds all known cookies and related
- information. Each `Curl_easy` has its own private CookieInfo even when
+ information. Each `Curl_easy` has its own private `CookieInfo` even when
they are added to a multi handle. They can be made to share cookies by using
the share API.
projects / curl / commitdiff