Introduction to CMake
---------------------

CMake is a multi-platform build tool that can generate build files for many
different target platforms. See more info at http://www.cmake.org

CMake also allows/recommends you to do "out of source"-builds, that is, 
the build files are separated from your sources, so there is no need to 
create elaborate clean scripts to get a clean source tree, instead you 
simply remove your build directory.

Libwebsockets has been tested to build successfully on the following platforms
with SSL support (both OpenSSL/CyaSSL):

- Windows
- Linux (x86 and ARM)
- OSX
- NetBSD

Building the library and test apps
----------------------------------

The project settings used by CMake to generate the platform specific build
files is called CMakeLists.txt. CMake then uses one of its "Generators" to
output a Visual Studio project or Make file for instance. To see a list of
the available generators for your platform, simply run the "cmake" command.

Note that by default OpenSSL will be linked, if you don't want SSL support
see below on how to toggle compile options.

Building on Unix:
-----------------

1. Install CMake 2.6 or greater: http://cmake.org/cmake/resources/software.html
   (Most Unix distributions comes with a packaged version also)

2. Install OpenSSL.

3. Generate the build files (default is Make files):

	cd /path/to/src
	mkdir build
	cd build
	cmake ..

	(NOTE: The build/ directory can have any name and be located anywhere
	 on your filesystem, and that the argument ".." given to cmake is simply
	 the source directory of libwebsockets containing the CMakeLists.txt
	 project file. All examples in this file assumes you use "..")

	NOTE2
	A common option you may want to give is to set the install path, same
	as --prefix= with autotools.  It defaults to /usr/local.
	You can do this by, eg

	cmake .. -DCMAKE_INSTALL_PREFIX:PATH=/usr

	NOTE3
	On machines that want libraries in lib64, you can also add the
	following to the cmake line

		-DLIB_SUFFIX=64
		
	NOTE4
	If you are building against a non-distro OpenSSL (eg, in order to get
	access to ALPN support only in newer OpenSSL versions) the nice way to
	express that in one cmake command is eg,
	
		-DOPENSSL_ROOT_DIR=/usr/local/ssl

4. Finally you can build using the generated Makefile:

	make

	
Quirk of cmake
--------------

When changing cmake options, for some reason the only way to get it to see the
changes sometimes is delete the contents of your build directory and do the
cmake from scratch.


Building on Windows (Visual Studio)
-----------------------------------
1. Install CMake 2.6 or greater: http://cmake.org/cmake/resources/software.html

2. Install OpenSSL binaries. http://www.openssl.org/related/binaries.html
   (Preferably in the default location to make it easier for CMake to find them)

3. Generate the Visual studio project by opening the Visual Studio cmd prompt:

   cd <path to src>
   md build
   cd build
   cmake -G "Visual Studio 10" ..

   (NOTE: There is also a cmake-gui available on Windows if you prefer that)

4. Now you should have a generated Visual Studio Solution in  your
   <path to src>/build directory, which can be used to build.

Setting compile options
-----------------------

To set compile time flags you can either use one of the CMake gui applications
or do it via command line.

Command line
------------
To list avaialable options (ommit the H if you don't want the help text):

	cmake -LH ..

Then to set an option and build (for example turn off SSL support):

	cmake -DLWS_WITH_SSL=0 ..
or
	cmake -DLWS_WITH_SSL:BOOL=OFF ..

Unix GUI
--------
If you have a curses enabled build you simply type:
(not all packages include this, my debian install does not for example).
	
	ccmake

Windows GUI
-----------
On windows CMake comes with a gui application:
	Start -> Programs -> CMake -> CMake (cmake-gui)

CyaSSL replacement for OpenSSL
------------------------------
CyaSSL is a lightweight SSL library targeted at embedded system:
http://www.yassl.com/yaSSL/Products-cyassl.html

It contains a OpenSSL compatability layer which makes it possible to pretty
much link to it instead of OpenSSL, giving a much smaller footprint.

NOTE: cyassl needs to be compiled using the --enable-opensslextra flag for
this to work.

Compiling libwebsockets with CyaSSL
-----------------------------------

cmake .. -DLWS_USE_CYASSL=1 \
	 -DLWS_CYASSL_INCLUDE_DIRS=/path/to/cyassl \
	 -DLWS_CYASSL_LIB=/path/to/cyassl/cyassl.a ..

NOTE: On windows use the .lib file extension for LWS_CYASSL_LIB instead.

Cross compiling
---------------
To enable cross compiling libwebsockets using CMake you need to create
a "Toolchain file" that you supply to CMake when generating your build files.
CMake will then use the cross compilers and build paths specified in this file
to look for dependencies and such.

Libwebsockets includes an example toolchain file cross-arm-linux-gnueabihf.cmake
you can use as a starting point.

The commandline to configure for cross with this would look like

cmake .. -DCMAKE_INSTALL_PREFIX:PATH=/usr \
	 -DCMAKE_TOOLCHAIN_FILE=../cross-arm-linux-gnueabihf.cmake \
	 -DWITHOUT_EXTENSIONS=1 -DWITH_SSL=0

The example shows how to build with no external cross lib dependencies, you
need to proide the cross libraries otherwise.

NOTE: start from an EMPTY build directory if you had a non-cross build in there
	before the settings will be cached and your changes ignored.

Additional information on cross compilation with CMake:
	http://www.vtk.org/Wiki/CMake_Cross_Compiling


Memory efficiency
-----------------

Embedded server-only configuration without extensions (ie, no compression
on websocket connections), but with full v13 websocket features and http
server, built on ARM Cortex-A9:

Update at 8dac94d (2013-02-18)

./configure --without-client --without-extensions --disable-debug --without-daemonize

Context Creation, 1024 fd limit[2]:   16720 (includes 12 bytes per fd)
Per-connection [3]:                      72 bytes, +1328 during headers

.text	.rodata	.data	.bss
11512	2784	288	4

This shows the impact of the major configuration with/without options at
13ba5bbc633ea962d46d using Ubuntu ARM on a PandaBoard ES.

These are accounting for static allocations from the library elf, there are
additional dynamic allocations via malloc.  These are a bit old now but give
the right idea for relative "expense" of features.

Static allocations, ARM9
				.text	.rodata	.data	.bss
 All (no without)		35024	9940	336	4104
 without client			25684	7144	336	4104
 without client, exts		21652	6288	288	4104
 without client, exts, debug[1]	19756	3768	288	4104
 without server			30304	8160	336	4104
 without server, exts		25382	7204	288	4104
 without server, exts, debug[1]	23712	4256	288	4104

[1] --disable-debug only removes messages below lwsl_notice.  Since that is
the default logging level the impact is not noticable, error, warn and notice
logs are all still there.

[2] 1024 fd per process is the default limit (set by ulimit) in at least Fedora
and Ubuntu.  You can make significant savings tailoring this to actual expected
peak fds, ie, at a limit of 20, context creation allocation reduces to 4432 +
240 = 4672)

[3] known header content is freed after connection establishment



