CodingStyle

The following file is strongly inspired from the linux kernel documentation. 
I'm using this CodingStyle, because I guess a lot of open-source projects use
a similar one, and I think it makes the code realy clear and concise.
It is also fully compliant with the VIM features (Join the good side of the 
force, and forget other editors :D).
Although the original Supertux codebase use a different coding-style, I have 
chosen to not keep it because I think it makes the code too big (Only one 
curly-brace per line ... really ??). I also think that a 2 characters 
indentation make the code unreadable ...
If you want to contribute to this project, you have to follow the following 
rules or your code will not be merged.
This is not really a coding-style rule, but if you plan to add new code, please
try to use as much as possible C++11 features.
					Have a nice reading ;)
							CHAUVIN Barnabe


	 	Chapter 1: Indentation

Tabs are 8 characters, and thus indentations are also 8 characters.
There are heretic movements that try to make indentations 4 (or even 2!)
characters deep, and that is akin to trying to define the value of PI to
be 3.

Rationale: The whole idea behind indentation is to clearly define where
a block of control starts and ends.  Especially when you've been looking
at your screen for 20 straight hours, you'll find it a lot easier to see
how the indentation works if you have large indentations.

Now, some people will claim that having 8-character indentations makes
the code move too far to the right, and makes it hard to read on a
80-character terminal screen.  The answer to that is that if you need
more than 3 levels of indentation, you're screwed anyway, and should fix
your program.

In short, 8-char indents make things easier to read, and have the added
benefit of warning you when you're nesting your functions too deep.
Heed that warning.

Try to indent cases in a switch, unless your cases content are really long.

	switch (suffix) {
		case 'G':
		case 'g':
			mem <<= 30;
			break;
		case 'M':
		case 'm':
			mem <<= 20;
			break;
		case 'K':
		case 'k':
			mem <<= 10;
			/* fall through */
		default:
			break;
	}


Don't put multiple statements on a single line unless you have
something to hide:

	if (condition) do_this;
	  do_something_everytime;

Outside of comments or documentation, spaces are never used for indentation, 
and the above example is deliberately broken.

Get a decent editor and don't leave whitespace at the end of lines, unless it
is Markdown syntax (e.g. : README.md).

Blank lines should not contains any spaces/tabulations.


		Chapter 2: Breaking long lines and strings

Coding style is all about readability and maintainability using commonly
available tools.

The limit on the length of lines is 80 columns and this is a strongly
preferred limit.

Statements longer than 80 columns will be broken into sensible chunks, unless
exceeding 80 columns significantly increases readability and does not hide
information. Descendants are always substantially shorter than the parent and
are placed substantially to the right. The same applies to function headers
with a long argument list. However, never break user-visible strings such as
printf messages, because that breaks the ability to grep for them.


		Chapter 3: Placing Braces and Spaces

The other issue that always comes up in C styling is the placement of
braces.  Unlike the indent size, there are few technical reasons to
choose one placement strategy over the other, but the preferred way, as
shown to us by the prophets Kernighan and Ritchie, is to put the opening
brace last on the line, and put the closing brace first, thusly:

	if (x is true) {
		we do y
	}

This applies to all non-function statement blocks (if, switch, for,
while, do).  E.g.:

	switch (action) {
		case KOBJ_ADD:
			return "add";
		case KOBJ_REMOVE:
			return "remove";
		case KOBJ_CHANGE:
			return "change";
		default:
			return NULL;
	}

However, there is one special case, namely functions: they have the
opening brace at the beginning of the next line, thus:

	int function(int x)
	{
		body of function
	}

Heretic people all over the world have claimed that this inconsistency
is ...  well ...  inconsistent, but all right-thinking people know that
(a) K&R are _right_ and (b) K&R are right.  Besides, functions are
special anyway (you can't nest them in C).

Note that the closing brace is empty on a line of its own, _except_ in
the cases where it is followed by a continuation of the same statement,
ie a "while" in a do-statement or an "else" in an if-statement, like
this:

	do {
		body of do-loop
	} while (condition);

and

	if (x == y) {
		..
	} else if (x > y) {
		...
	} else {
		....
	}

Rationale: K&R.

Also, note that this brace-placement also minimizes the number of empty
(or almost empty) lines, without any loss of readability.  Thus, as the
supply of new-lines on your screen is not a renewable resource (think
25-line terminal screens here), you have more empty lines to put
comments on.

Do not unnecessarily use braces where a single statement will do.

if (condition)
	action();
else
	do_that();


		3.1:  Spaces

Use a space after (most) keywords.  The notable exceptions are sizeof, typeof,
alignof, and __attribute__, which look somewhat like functions.

So use a space after these keywords:
	if, switch, case, for, do, while
but not with sizeof, typeof, alignof, or __attribute__.  E.g.,
	s = sizeof(struct file);

Do not add spaces around (inside) parenthesized expressions.  This example is
*bad*:

	s = sizeof( struct file );

When declaring pointer data or a function that returns a pointer type, the
preferred use of '*' is adjacent to the data name or function name and not
adjacent to the type name.  Examples:

	char *foo_bar;
	unsigned long long memparse(char *ptr, char **retptr);
	char *match_strdup(substring_t *s);

Use one space around (on each side of) most binary and ternary operators,
such as any of these:

	=  +  -  <  >  *  /  %  |  &  ^  <=  >=  ==  !=  ?  :

but no space after unary operators:
	&  *  +  -  ~  !  sizeof  typeof  alignof  __attribute__  defined

no space before the postfix increment & decrement unary operators:
	++  --

no space after the prefix increment & decrement unary operators:
	++  --

and no space around the '.' and "->" structure member operators.

Do not leave trailing whitespace at the ends of lines.  Some editors with
"smart" indentation will insert whitespace at the beginning of new lines as
appropriate, so you can start typing the next line of code right away.
However, some such editors do not remove the whitespace if you end up not
putting a line of code there, such as if you leave a blank line.  As a result,
you end up with lines containing trailing whitespace.

Git will warn you about patches that introduce trailing whitespace, and can
optionally strip the trailing whitespace for you; however, if applying a series
of patches, this may make later patches in the series fail by changing their
context lines.


		Chapter 4: Naming

C is a Spartan language, and so should your naming be.  Unlike Modula-2
and Pascal programmers, C programmers do not use cute names like
ThisVariableIsATemporaryCounter.  A C programmer would call that
variable "tmp", which is much easier to write, and not the least more
difficult to understand.

HOWEVER, while mixed-case names are frowned upon, descriptive names for
global variables are a must.  To call a global function "foo" is a
shooting offense.

GLOBAL variables (to be used only if you _really_ need them) need to
have descriptive names, as do global functions.  If you have a function
that counts the number of active users, you should call that
"count_active_users()" or similar, you should _not_ call it "cntusr()".

Encoding the type of a function into the name (so-called Hungarian
notation) is brain damaged - the compiler knows the types anyway and can
check those, and it only confuses the programmer.  No wonder MicroSoft
makes buggy programs.

LOCAL variable names should be short, and to the point.  If you have
some random integer loop counter, it should probably be called "i".
Calling it "loop_counter" is non-productive, if there is no chance of it
being mis-understood.  Similarly, "tmp" can be just about any type of
variable that is used to hold a temporary value.

If you are afraid to mix up your local variable names, you have another
problem, which is called the function-growth-hormone-imbalance syndrome.
See chapter 6 (Functions).


		Chapter 5: Typedefs

Please don't use things like "vps_t".

It's a _mistake_ to use typedef for structures and pointers. When you see a

	vps_t a;

in the source, what does it mean?

In contrast, if it says

	struct virtual_container *a;

you can actually tell what "a" is.

Lots of people think that typedefs "help readability". Not so. They are
useful only for:

 (a) totally opaque objects (where the typedef is actively used to _hide_
     what the object is).

     Example: "pte_t" etc. opaque objects that you can only access using
     the proper accessor functions.

     NOTE! Opaqueness and "accessor functions" are not good in themselves.
     The reason we have them for things like pte_t etc. is that there
     really is absolutely _zero_ portably accessible information there.

 (b) Clear integer types, where the abstraction _helps_ avoid confusion
     whether it is "int" or "long".

     u8/u16/u32 are perfectly fine typedefs, although they fit into
     category (d) better than here.

     NOTE! Again - there needs to be a _reason_ for this. If something is
     "unsigned long", then there's no reason to do

	typedef unsigned long myflags_t;

     but if there is a clear reason for why it under certain circumstances
     might be an "unsigned int" and under other configurations might be
     "unsigned long", then by all means go ahead and use a typedef.

 (c) when you use sparse to literally create a _new_ type for
     type-checking.

 (d) New types which are identical to standard C99 types, in certain
     exceptional circumstances.

     Although it would only take a short amount of time for the eyes and
     brain to become accustomed to the standard types like 'uint32_t',
     some people object to their use anyway.

     Therefore, the Linux-specific 'u8/u16/u32/u64' types and their
     signed equivalents which are identical to standard types are
     permitted -- although they are not mandatory in new code of your
     own.

     When editing existing code which already uses one or the other set
     of types, you should conform to the existing choices in that code.

 (e) Types safe for use in userspace.

     In certain structures which are visible to userspace, we cannot
     require C99 types and cannot use the 'u32' form above. Thus, we
     use __u32 and similar types in all structures which are shared
     with userspace.

Maybe there are other cases too, but the rule should basically be to NEVER
EVER use a typedef unless you can clearly match one of those rules.

In general, a pointer, or a struct that has elements that can reasonably
be directly accessed should _never_ be a typedef.


		Chapter 6: Functions

Functions should be short and sweet, and do just one thing.  They should
fit on one or two screenfuls of text (the ISO/ANSI screen size is 80x24,
as we all know), and do one thing and do that well.

The maximum length of a function is inversely proportional to the
complexity and indentation level of that function.  So, if you have a
conceptually simple function that is just one long (but simple)
case-statement, where you have to do lots of small things for a lot of
different cases, it's OK to have a longer function.

However, if you have a complex function, and you suspect that a
less-than-gifted first-year high-school student might not even
understand what the function is all about, you should adhere to the
maximum limits all the more closely.  Use helper functions with
descriptive names (you can ask the compiler to in-line them if you think
it's performance-critical, and it will probably do a better job of it
than you would have done).

Another measure of the function is the number of local variables.  They
shouldn't exceed 5-10, or you're doing something wrong.  Re-think the
function, and split it into smaller pieces.  A human brain can
generally easily keep track of about 7 different things, anything more
and it gets confused.  You know you're brilliant, but maybe you'd like
to understand what you did 2 weeks from now.

In source files, separate functions with one blank line.  If the function is
exported, the EXPORT* macro for it should follow immediately after the closing
function brace line.  E.g.:

int system_is_up(void)
{
	return system_state == SYSTEM_RUNNING;
}
EXPORT_SYMBOL(system_is_up);

In function prototypes, include parameter names with their data types.
Although this is not required by the C language, it is preferred in Linux
because it is a simple way to add valuable information for the reader.


		Appendix I: References

The C Programming Language, Second Edition
by Brian W. Kernighan and Dennis M. Ritchie.
Prentice Hall, Inc., 1988.
ISBN 0-13-110362-8 (paperback), 0-13-110370-9 (hardback).
URL: http://cm.bell-labs.com/cm/cs/cbook/

The Practice of Programming
by Brian W. Kernighan and Rob Pike.
Addison-Wesley, Inc., 1999.
ISBN 0-201-61586-X.
URL: http://cm.bell-labs.com/cm/cs/tpop/

GNU manuals - where in compliance with K&R and this text - for cpp, gcc,
gcc internals and indent, all available from http://www.gnu.org/manual/

WG14 is the international standardization working group for the programming
language C, URL: http://www.open-std.org/JTC1/SC22/WG14/

Kernel CodingStyle, by greg@kroah.com at OLS 2002:
http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/