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Commit b099701d authored by Kevin P. Fleming's avatar Kevin P. Fleming
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various text/formatting updates (issue #5503 plus some minor additions) 

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== Asterisk Patch/Coding Guidelines ==
--------------------------------------
We are looking forward to your contributions to Asterisk - the
Open Source PBX! As Asterisk is a large and in some parts very
time-sensitive application, the code base needs to conform to
a common set of coding rules so that many developers can enhance
and maintain the code. Code also needs to be reviewed and tested
so that it works and follows the general architecture and guide-
lines, and is well documented.
Asterisk is published under a dual-licensing scheme by Digium.
To be accepted into the codebase, all non-trivial changes must be
disclaimed to Digium or placed in the public domain. For more information
see http://bugs.digium.com
......@@ -12,30 +22,57 @@ above the top-level Asterisk source directory. For example:
~/work$ diff -urN asterisk-base asterisk-new
All code, filenames, function names and comments must be in ENGLISH.
If you are changing within a fresh CVS/SVN repository, you can create
a patch with
$ cvs diff -urN <mycodefile>.c
* General rules
---------------
- All code, filenames, function names and comments must be in ENGLISH.
- Don't annotate your changes with comments like "/* JMG 4/20/04 */";
Comments should explain what the code does, not when something was changed
or who changed it. If you have done a larger contribution, make sure
that you are added to the CREDITS file.
- Don't make unnecessary whitespace changes throughout the code.
If you make changes, submit them to the tracker as separate patches
that only include whitespace and formatting changes.
Do not declare variables mid-function (e.g. like recent GNU compilers support)
since it is harder to read and not portable to GCC 2.95 and others.
- Don't use C++ type (//) comments.
Don't annotate your changes with comments like "/* JMG 4/20/04 */";
Comments should explain what the code does, not when something was changed
or who changed it.
- Try to match the existing formatting of the file you are working on.
Don't make unnecessary whitespace changes throughout the code.
- Use spaces instead of tabs when aligning in-line comments or #defines (this makes
your comments aligned even if the code is viewed with another tabsize)
Don't use C++ type (//) comments.
* Declaration of functions and variables
----------------------------------------
Try to match the existing formatting of the file you are working on.
- Do not declare variables mid-block (e.g. like recent GNU compilers support)
since it is harder to read and not portable to GCC 2.95 and others.
Functions and variables that are not intended to be used outside the module
must be declared static.
- Functions and variables that are not intended to be used outside the module
must be declared static.
When reading integer numeric input with scanf (or variants), do _NOT_ use '%i'
unless you specifically want to allow non-base-10 input; '%d' is always a better
choice, since it will not silently turn numbers with leading zeros into base-8.
- When reading integer numeric input with scanf (or variants), do _NOT_ use '%i'
unless you specifically want to allow non-base-10 input; '%d' is always a better
choice, since it will not silently turn numbers with leading zeros into base-8.
Use spaces instead of tabs when aligning in-line comments or #defines (this makes
your comments aligned even if the code is viewed with another tabsize)
- Strings that are coming from input should not be used as a first argument to
a formatted *printf function.
* Use the internal API
----------------------
- Make sure you are aware of the string and data handling functions that exist
within Asterisk to enhance portability and in some cases to produce more
secure and thread-safe code. Check utils.c/utils.h for these.
* Code formatting
-----------------
Roughly, Asterisk code formatting guidelines are generally equivalent to the
following:
......@@ -60,11 +97,11 @@ this means in verbose:
Function calls and arguments should be spaced in a consistent way across
the codebase.
GOOD: foo(arg1, arg2);
GOOD: foo(arg1,arg2); /* Acceptable but not preferred */
BAD: foo (arg1, arg2);
BAD: foo( arg1, arg2 );
BAD: foo(arg1, arg2,arg3);
GOOD: foo(arg1, arg2);
GOOD: foo(arg1,arg2); /* Acceptable but not preferred */
BAD: foo (arg1, arg2);
BAD: foo( arg1, arg2 );
BAD: foo(arg1, arg2,arg3);
Don't treat keywords (if, while, do, return) as if they were functions;
leave space between the keyword and the expression used (if any). For 'return',
......@@ -74,28 +111,28 @@ required.
There is no shortage of whitespace characters :-) Use them when they make
the code easier to read. For example:
for (str=foo;str;str=str->next)
for (str=foo;str;str=str->next)
is harder to read than
for (str = foo; str; str = str->next)
for (str = foo; str; str = str->next)
Following are examples of how code should be formatted.
Functions:
- Functions:
int foo(int a, char *s)
{
return 0;
}
If statements:
- If statements:
if (foo) {
bar();
} else {
blah();
}
Case statements:
- Case statements:
switch (foo) {
case BAR:
blah();
......@@ -105,7 +142,7 @@ case OTHER:
break;
}
No nested statements without braces, e.g.:
- No nested statements without braces, e.g.:
for (x = 0; x < 5; x++)
if (foo)
......@@ -120,7 +157,7 @@ for (x = 0; x < 5; x++) {
}
}
Don't build code like this:
- Don't build code like this:
if (foo) {
/* .... 50 lines of code ... */
......@@ -144,12 +181,14 @@ When this technique is used properly, it makes functions much easier to read
and follow, especially those with more than one or two 'setup' operations
that must succeed for the rest of the function to be able to execute.
- Labels/goto are acceptable
Proper use of this technique may occasionally result in the need for a
label/goto combination so that error/failure conditions can exit the
function while still performing proper cleanup. This is not a bad thing!
Use of goto in this situation is encouraged, since it removes the need
for excess code indenting without requiring duplication of cleanup code.
- Never use an uninitialized variable
Make sure you never use an uninitialized variable. The compiler will
usually warn you if you do so. However, do not go too far the other way,
and needlessly initialize variables that do not require it. If the first
......@@ -159,6 +198,7 @@ object code and data in the resulting binary with no purpose. When in doubt,
trust the compiler to tell you when you need to initialize a variable;
if it does not warn you, initialization is not needed.
- Do not cast 'void *'
Do not explicitly cast 'void *' into any other type, nor should you cast any
other type into 'void *'. Implicit casts to/from 'void *' are explicitly
allowed by the C specification. This means the results of malloc(), calloc(),
......@@ -166,6 +206,10 @@ alloca(), and similar functions do not _ever_ need to be cast to a specific
type, and when you are passing a pointer to (for example) a callback function
that accepts a 'void *' you do not need to cast into that type.
* Variable naming
-----------------
- Global variables
Name global variables (or local variables when you have a lot of them or
are in a long function) something that will make sense to aliens who
find your code in 100 years. All variable names should be in lower
......@@ -178,6 +222,7 @@ Make some indication in the name of global variables which represent
options that they are in fact intended to be global.
e.g.: static char global_something[80]
- Don't use un-necessary typedef's
Don't use 'typedef' just to shorten the amount of typing; there is no substantial
benefit in this:
......@@ -189,6 +234,7 @@ typedef foo_t struct foo;
In fact, don't use 'variable type' suffixes at all; it's much preferable to
just type 'struct foo' rather than 'foo_s'.
- Use enums instead of #define where possible
Use enums rather than long lists of #define-d numeric constants when possible;
this allows structure members, local variables and function arguments to
be declared as using the enum's type. For example:
......@@ -208,7 +254,38 @@ static handle_option(const enum option opt)
Note: The compiler will _not_ force you to pass an entry from the enum
as an argument to this function; this recommendation serves only to make
the code clearer and somewhat self-documenting.
the code clearer and somewhat self-documenting. In addition, when using
switch/case blocks that switch on enum values, the compiler will warn
you if you forget to handle one or more of the enum values, which can be
handy.
* String handling
-----------------
Don't use strncpy for copying whole strings; it does not guarantee that the
output buffer will be null-terminated. Use ast_copy_string instead, which
is also slightly more efficient (and allows passing the actual buffer
size, which makes the code clearer).
Don't use ast_copy_string (or any length-limited copy function) for copying
fixed (known at compile time) strings into buffers, if the buffer is something
that has been allocated in the function doing the copying. In that case, you
know at the time you are writing the code whether the buffer is large enough
for the fixed string or not, and if it's not, your code won't work anyway!
Use strcpy() for this operation, or directly set the first two characters
of the buffer if you are just trying to store a one-character string in the
buffer. If you are trying to 'empty' the buffer, just store a single
NULL character ('\0') in the first byte of the buffer; nothing else is
needed, and any other method is wasteful.
In addition, if the previous operations in the function have already
determined that the buffer in use is adequately sized to hold the string
you wish to put into it (even if you did not allocate the buffer yourself),
use a direct strcpy(), as it can be inlined and optimized to simple
processor operations, unlike ast_copy_string().
* Use of functions
------------------
When making applications, always ast_strdupa(data) to a local pointer if
you intend to parse the incoming data string.
......@@ -216,20 +293,19 @@ you intend to parse the incoming data string.
if (data)
mydata = ast_strdupa(data);
- Separating arguments to dialplan applications and functions
Use ast_separate_app_args() to separate the arguments to your application
once you have made a local copy of the string.
- Parsing strings with strsep
Use strsep() for parsing strings when possible; there is no worry about
're-entrancy' as with strtok(), and even though it modifies the original
string (which the man page warns about), in many cases that is exactly
what you want!
Always derefrence or localize pointers to things that are not yours like
channel members in a channel that is not associated with the current
thread and for which you do not have a lock.
channame = ast_strdupa(otherchan->name);
If you do the same or a similar operation more than 1 time, make it a
- Create generic code!
If you do the same or a similar operation more than one time, make it a
function or macro.
Make sure you are not duplicating any functionality already found in an
......@@ -237,6 +313,23 @@ API call somewhere. If you are duplicating functionality found in
another static function, consider the value of creating a new API call
which can be shared.
* Handling of pointers and allocations
--------------------------------------
- Dereference or localize pointers
Always dereference or localize pointers to things that are not yours like
channel members in a channel that is not associated with the current
thread and for which you do not have a lock.
channame = ast_strdupa(otherchan->name);
- Use const on pointer arguments if possible
Use const on pointer arguments which your function will not be modifying, as this
allows the compiler to make certain optimizations. In general, use 'const'
on any argument that you have no direct intention of modifying, as it can
catch logic/typing errors in your code when you use the argument variable
in a way that you did not intend.
- Do not create your own linked list code - reuse!
As a common example of this point, make an effort to use the lockable
linked-list macros found in include/asterisk/linkedlists.h. They are
efficient, easy to use and provide every operation that should be
......@@ -247,16 +340,7 @@ that code... There are also a number of common string manipulation
and timeval manipulation functions in asterisk/strings.h and asterisk/time.h;
use them when possible.
When you achieve your desired functionalty, make another few refactor
passes over the code to optimize it.
Before submitting a patch, *read* the actual patch file to be sure that
all the changes you expect to be there are, and that there are no
surprising changes you did not expect.
If you are asked to make changes to your patch, there is a good chance
the changes will introduce bugs, check it even more at this stage.
- Avoid needless allocations!
Avoid needless malloc(), strdup() calls. If you only need the value in
the scope of your function try ast_strdupa() or declare structs on the
stack and pass a pointer to them. However, be careful to _never_ call
......@@ -264,62 +348,7 @@ alloca(), ast_strdupa() or similar functions in the argument list
of a function you are calling; this can cause very strange stack
arrangements and produce unexpected behavior.
If you are going to reuse a computed value, save it in a variable
instead of recomputing it over and over. This can prevent you from
making a mistake in subsequent computations, make it easier to correct
if the formula has an error and may or may not help optimization but
will at least help readability.
Just an example, so don't over analyze it, that'd be a shame:
const char *prefix = "pre";
const char *postfix = "post";
char *newname;
char *name = "data";
if (name && (newname = alloca(strlen(name) + strlen(prefix) + strlen(postfix) + 3)))
snprintf(newname, strlen(name) + strlen(prefix) + strlen(postfix) + 3, "%s/%s/%s", prefix, name, postfix);
vs
const char *prefix = "pre";
const char *postfix = "post";
char *newname;
char *name = "data";
int len = 0;
if (name && (len = strlen(name) + strlen(prefix) + strlen(postfix) + 3) && (newname = alloca(len)))
snprintf(newname, len, "%s/%s/%s", prefix, name, postfix);
Use const on pointer arguments which your function will not be modifying, as this
allows the compiler to make certain optimizations. In general, use 'const'
on any argument that you have no direct intention of modifying, as it can
catch logic/typing errors in your code when you use the argument variable
in a way that you did not intend.
Don't use strncpy for copying whole strings; it does not guarantee that the
output buffer will be null-terminated. Use ast_copy_string instead, which
is also slightly more efficient (and allows passing the actual buffer
size, which makes the code clearer).
Don't use ast_copy_string (or any length-limited copy function) for copying
fixed (known at compile time) strings into buffers, if the buffer is something
that has been allocated in the function doing the copying. In that case, you
know at the time you are writing the code whether the buffer is large enough
for the fixed string or not, and if it's not, your code won't work anyway!
Use strcpy() for this operation, or directly set the first two characters
of the buffer if you are just trying store a one-character string in the
buffer. If you are trying to 'empty' the buffer, just store a single
NULL character ('\0') in the first byte of the buffer; nothing else is
needed, and any other method is wasteful.
In addition, if the previous operations in the function have already
determined that the buffer in use is adequately sized to hold the string
you wish to put into it (even if you did not allocate the buffer yourself),
use a direct strcpy(), as it can be inlined and optimized to simple
processor operations, unlike ast_copy_string().
-Allocations for structures
When allocating/zeroing memory for a structure, try to use code like this:
struct foo *tmp;
......@@ -342,7 +371,8 @@ tmp = calloc(1, sizeof(*tmp));
This will allocate and zero the memory in a single operation.
== CLI Commands ==
* CLI Commands
--------------
New CLI commands should be named using the module's name, followed by a verb
and then any parameters that the command needs. For example:
......@@ -353,7 +383,8 @@ not
*CLI> show iax2 peer <peername>
== New dialplan applications/functions ==
* New dialplan applications/functions
-------------------------------------
There are two methods of adding functionality to the Asterisk
dialplan: applications and functions. Applications (found generally in
......@@ -371,10 +402,11 @@ example.
Functions are registered using 'struct ast_custom_function'
structures and the ast_custom_function_register function.
== Doxygen API Documentation Guidelines ==
* Doxygen API Documentation Guidelines
--------------------------------------
When writing Asterisk API documentation the following format should be
followed.
followed. Do not use the javadoc style.
/*!
* \brief Do interesting stuff.
......@@ -419,3 +451,60 @@ struct interesting_struct
Note that /*! */ blocks document the construct immediately following them
unless they are written, /*!< */, in which case they document the construct
preceding them.
* Finishing up before you submit your code
------------------------------------------
- Look at the code once more
When you achieve your desired functionalty, make another few refactor
passes over the code to optimize it.
- Read the patch
Before submitting a patch, *read* the actual patch file to be sure that
all the changes you expect to be there are, and that there are no
surprising changes you did not expect. During your development, that
part of Asterisk may have changed, so make sure you compare with the
latest CVS.
- Listen to advice
If you are asked to make changes to your patch, there is a good chance
the changes will introduce bugs, check it even more at this stage.
Also remember that the bug marshal or co-developer that adds comments
is only human, they may be in error :-)
- Optimize, optimize, optimize
If you are going to reuse a computed value, save it in a variable
instead of recomputing it over and over. This can prevent you from
making a mistake in subsequent computations, making it easier to correct
if the formula has an error and may or may not help optimization but
will at least help readability.
Just an example (so don't over analyze it, that'd be a shame):
const char *prefix = "pre";
const char *postfix = "post";
char *newname;
char *name = "data";
if (name && (newname = alloca(strlen(name) + strlen(prefix) + strlen(postfix) + 3)))
snprintf(newname, strlen(name) + strlen(prefix) + strlen(postfix) + 3, "%s/%s/%s", prefix, name, postfix);
...vs this alternative:
const char *prefix = "pre";
const char *postfix = "post";
char *newname;
char *name = "data";
int len = 0;
if (name && (len = strlen(name) + strlen(prefix) + strlen(postfix) + 3) && (newname = alloca(len)))
snprintf(newname, len, "%s/%s/%s", prefix, name, postfix);
-----------------------------------------------
Welcome to the Asterisk development community!
Meet you on the asterisk-dev mailing list.
Subscribe at http://lists.digium.com!
Mark Spencer, Kevin P. Fleming and
the Asterisk.org Development Team
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