git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6163 65c4cc65-6c06-0410-ace0-fbb531ad65f3
422 lines
14 KiB
Text
Executable file
422 lines
14 KiB
Text
Executable file
== Asterisk Patch/Coding Guidelines ==
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To be accepted into the codebase, all non-trivial changes must be
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disclaimed to Digium or placed in the public domain. For more information
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see http://bugs.digium.com
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Patches should be in the form of a unified (-u) diff, made from the directory
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above the top-level Asterisk source directory. For example:
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- the base code you are working from is in ~/work/asterisk-base
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- the changes are in ~/work/asterisk-new
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~/work$ diff -urN asterisk-base asterisk-new
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All code, filenames, function names and comments must be in ENGLISH.
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Do not declare variables mid-function (e.g. like recent GNU compilers support)
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since it is harder to read and not portable to GCC 2.95 and others.
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Don't annotate your changes with comments like "/* JMG 4/20/04 */";
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Comments should explain what the code does, not when something was changed
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or who changed it.
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Don't make unnecessary whitespace changes throughout the code.
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Don't use C++ type (//) comments.
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Try to match the existing formatting of the file you are working on.
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Functions and variables that are not intended to be used outside the module
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must be declared static.
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When reading integer numeric input with scanf (or variants), do _NOT_ use '%i'
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unless you specifically want to allow non-base-10 input; '%d' is always a better
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choice, since it will not silently turn numbers with leading zeros into base-8.
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Use spaces instead of tabs when aligning in-line comments or #defines (this makes
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your comments aligned even if the code is viewed with another tabsize)
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Roughly, Asterisk code formatting guidelines are generally equivalent to the
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following:
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# indent -i4 -ts4 -br -brs -cdw -cli0 -ce -nbfda -npcs -nprs -npsl -saf -sai -saw foo.c
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this means in verbose:
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-i4: indent level 4
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-ts4: tab size 4
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-br: braces on if line
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-brs: braces on struct decl line
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-cdw: cuddle do while
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-cli0: case indentation 0
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-ce: cuddle else
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-nbfda: dont break function decl args
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-npcs: no space after function call names
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-nprs: no space after parentheses
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-npsl: dont break procedure type
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-saf: space after for
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-sai: space after if
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-saw: space after while
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Function calls and arguments should be spaced in a consistent way across
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the codebase.
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GOOD: foo(arg1, arg2);
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GOOD: foo(arg1,arg2); /* Acceptable but not preferred */
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BAD: foo (arg1, arg2);
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BAD: foo( arg1, arg2 );
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BAD: foo(arg1, arg2,arg3);
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Don't treat keywords (if, while, do, return) as if they were functions;
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leave space between the keyword and the expression used (if any). For 'return',
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don't even put parentheses around the expression, since they are not
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required.
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There is no shortage of whitespace characters :-) Use them when they make
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the code easier to read. For example:
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for (str=foo;str;str=str->next)
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is harder to read than
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for (str = foo; str; str = str->next)
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Following are examples of how code should be formatted.
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Functions:
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int foo(int a, char *s)
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{
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return 0;
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}
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If statements:
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if (foo) {
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bar();
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} else {
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blah();
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}
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Case statements:
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switch (foo) {
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case BAR:
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blah();
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break;
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case OTHER:
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other();
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break;
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}
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No nested statements without braces, e.g.:
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for (x = 0; x < 5; x++)
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if (foo)
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if (bar)
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baz();
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instead do:
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for (x = 0; x < 5; x++) {
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if (foo) {
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if (bar)
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baz();
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}
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}
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Don't build code like this:
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if (foo) {
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/* .... 50 lines of code ... */
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} else {
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result = 0;
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return;
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}
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Instead, try to minimize the number of lines of code that need to be
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indented, by only indenting the shortest case of the 'if'
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statement, like so:
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if !(foo) {
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result = 0;
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return;
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}
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.... 50 lines of code ....
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When this technique is used properly, it makes functions much easier to read
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and follow, especially those with more than one or two 'setup' operations
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that must succeed for the rest of the function to be able to execute.
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Proper use of this technique may occasionally result in the need for a
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label/goto combination so that error/failure conditions can exit the
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function while still performing proper cleanup. This is not a bad thing!
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Use of goto in this situation is encouraged, since it removes the need
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for excess code indenting without requiring duplication of cleanup code.
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Make sure you never use an uninitialized variable. The compiler will
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usually warn you if you do so. However, do not go too far the other way,
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and needlessly initialize variables that do not require it. If the first
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time you use a variable in a function is to store a value there, then
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initializing it at declaration is pointless, and will generate extra
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object code and data in the resulting binary with no purpose. When in doubt,
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trust the compiler to tell you when you need to initialize a variable;
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if it does not warn you, initialization is not needed.
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Do not explicitly cast 'void *' into any other type, nor should you cast any
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other type into 'void *'. Implicit casts to/from 'void *' are explicitly
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allowed by the C specification. This means the results of malloc(), calloc(),
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alloca(), and similar functions do not _ever_ need to be cast to a specific
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type, and when you are passing a pointer to (for example) a callback function
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that accepts a 'void *' you do not need to cast into that type.
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Name global variables (or local variables when you have a lot of them or
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are in a long function) something that will make sense to aliens who
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find your code in 100 years. All variable names should be in lower
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case, except when following external APIs or specifications that normally
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use upper- or mixed-case variable names; in that situation, it is
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preferable to follow the external API/specification for ease of
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understanding.
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Make some indication in the name of global variables which represent
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options that they are in fact intended to be global.
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e.g.: static char global_something[80]
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Don't use 'typedef' just to shorten the amount of typing; there is no substantial
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benefit in this:
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struct foo {
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int bar;
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};
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typedef foo_t struct foo;
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In fact, don't use 'variable type' suffixes at all; it's much preferable to
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just type 'struct foo' rather than 'foo_s'.
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Use enums rather than long lists of #define-d numeric constants when possible;
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this allows structure members, local variables and function arguments to
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be declared as using the enum's type. For example:
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enum option {
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OPT_FOO = 1
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OPT_BAR = 2
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OPT_BAZ = 4
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};
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static enum option global_option;
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static handle_option(const enum option opt)
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{
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...
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}
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Note: The compiler will _not_ force you to pass an entry from the enum
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as an argument to this function; this recommendation serves only to make
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the code clearer and somewhat self-documenting.
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When making applications, always ast_strdupa(data) to a local pointer if
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you intend to parse the incoming data string.
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if (data)
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mydata = ast_strdupa(data);
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Use ast_separate_app_args() to separate the arguments to your application
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once you have made a local copy of the string.
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Use strsep() for parsing strings when possible; there is no worry about
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're-entrancy' as with strtok(), and even though it modifies the original
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string (which the man page warns about), in many cases that is exactly
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what you want!
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Always derefrence or localize pointers to things that are not yours like
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channel members in a channel that is not associated with the current
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thread and for which you do not have a lock.
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channame = ast_strdupa(otherchan->name);
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If you do the same or a similar operation more than 1 time, make it a
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function or macro.
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Make sure you are not duplicating any functionality already found in an
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API call somewhere. If you are duplicating functionality found in
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another static function, consider the value of creating a new API call
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which can be shared.
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As a common example of this point, make an effort to use the lockable
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linked-list macros found in include/asterisk/linkedlists.h. They are
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efficient, easy to use and provide every operation that should be
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necessary for managing a singly-linked list (if something is missing,
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let us know!). Just because you see other open-coded list implementations
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in the source tree is no reason to continue making new copies of
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that code... There are also a number of common string manipulation
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and timeval manipulation functions in asterisk/strings.h and asterisk/time.h;
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use them when possible.
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When you achieve your desired functionalty, make another few refactor
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passes over the code to optimize it.
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Before submitting a patch, *read* the actual patch file to be sure that
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all the changes you expect to be there are, and that there are no
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surprising changes you did not expect.
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If you are asked to make changes to your patch, there is a good chance
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the changes will introduce bugs, check it even more at this stage.
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Avoid needless malloc(), strdup() calls. If you only need the value in
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the scope of your function try ast_strdupa() or declare structs on the
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stack and pass a pointer to them. However, be careful to _never_ call
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alloca(), ast_strdupa() or similar functions in the argument list
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of a function you are calling; this can cause very strange stack
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arrangements and produce unexpected behavior.
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If you are going to reuse a computed value, save it in a variable
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instead of recomputing it over and over. This can prevent you from
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making a mistake in subsequent computations, make it easier to correct
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if the formula has an error and may or may not help optimization but
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will at least help readability.
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Just an example, so don't over analyze it, that'd be a shame:
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const char *prefix = "pre";
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const char *postfix = "post";
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char *newname;
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char *name = "data";
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if (name && (newname = alloca(strlen(name) + strlen(prefix) + strlen(postfix) + 3)))
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snprintf(newname, strlen(name) + strlen(prefix) + strlen(postfix) + 3, "%s/%s/%s", prefix, name, postfix);
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vs
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const char *prefix = "pre";
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const char *postfix = "post";
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char *newname;
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char *name = "data";
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int len = 0;
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if (name && (len = strlen(name) + strlen(prefix) + strlen(postfix) + 3) && (newname = alloca(len)))
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snprintf(newname, len, "%s/%s/%s", prefix, name, postfix);
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Use const on pointer arguments which your function will not be modifying, as this
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allows the compiler to make certain optimizations. In general, use 'const'
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on any argument that you have no direct intention of modifying, as it can
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catch logic/typing errors in your code when you use the argument variable
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in a way that you did not intend.
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Don't use strncpy for copying whole strings; it does not guarantee that the
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output buffer will be null-terminated. Use ast_copy_string instead, which
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is also slightly more efficient (and allows passing the actual buffer
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size, which makes the code clearer).
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Don't use ast_copy_string (or any length-limited copy function) for copying
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fixed (known at compile time) strings into buffers, if the buffer is something
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that has been allocated in the function doing the copying. In that case, you
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know at the time you are writing the code whether the buffer is large enough
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for the fixed string or not, and if it's not, your code won't work anyway!
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Use strcpy() for this operation, or directly set the first two characters
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of the buffer if you are just trying store a one-character string in the
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buffer. If you are trying to 'empty' the buffer, just store a single
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NULL character ('\0') in the first byte of the buffer; nothing else is
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needed, and any other method is wasteful.
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In addition, if the previous operations in the function have already
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determined that the buffer in use is adequately sized to hold the string
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you wish to put into it (even if you did not allocate the buffer yourself),
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use a direct strcpy(), as it can be inlined and optimized to simple
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processor operations, unlike ast_copy_string().
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When allocating/zeroing memory for a structure, try to use code like this:
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struct foo *tmp;
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...
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tmp = malloc(sizeof(*tmp));
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if (tmp)
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memset(tmp, 0, sizeof(*tmp));
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This eliminates duplication of the 'struct foo' identifier, which makes the
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code easier to read and also ensures that if it is copy-and-pasted it won't
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require as much editing. In fact, you can even use:
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struct foo *tmp;
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...
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tmp = calloc(1, sizeof(*tmp));
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This will allocate and zero the memory in a single operation.
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== CLI Commands ==
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New CLI commands should be named using the module's name, followed by a verb
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and then any parameters that the command needs. For example:
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*CLI> iax2 show peer <peername>
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not
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*CLI> show iax2 peer <peername>
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== New dialplan applications/functions ==
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There are two methods of adding functionality to the Asterisk
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dialplan: applications and functions. Applications (found generally in
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the apps/ directory) should be collections of code that interact with
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a channel and/or user in some significant way. Functions (which can be
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provided by any type of module) are used when the provided
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functionality is simple... getting/retrieving a value, for
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example. Functions should also be used when the operation is in no way
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related to a channel (a computation or string operation, for example).
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Applications are registered and invoked using the
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ast_register_application function; see the apps/app_skel.c file for an
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example.
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Functions are registered using 'struct ast_custom_function'
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structures and the ast_custom_function_register function.
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== Doxygen API Documentation Guidelines ==
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When writing Asterisk API documentation the following format should be
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followed.
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/*!
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* \brief Do interesting stuff.
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* \param thing1 interesting parameter 1.
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* \param thing2 interesting parameter 2.
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*
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* This function does some interesting stuff.
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*
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* \return zero on success, -1 on error.
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*/
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int ast_interesting_stuff(int thing1, int thing2)
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{
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return 0;
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}
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Notice the use of the \param, \brief, and \return constructs. These should be
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used to describe the corresponding pieces of the function being documented.
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Also notice the blank line after the last \param directive. All doxygen
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comments must be in one /*! */ block. If the function or struct does not need
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an extended description it can be left out.
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Please make sure to review the doxygen manual and make liberal use of the \a,
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\code, \c, \b, \note, \li and \e modifiers as appropriate.
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When documenting a 'static' function or an internal structure in a module,
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use the \internal modifier to ensure that the resulting documentation
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explicitly says 'for internal use only'.
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Structures should be documented as follows.
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/*!
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* \brief A very interesting structure.
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*/
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struct interesting_struct
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{
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/*! \brief A data member. */
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int member1;
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int member2; /*!< \brief Another data member. */
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}
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Note that /*! */ blocks document the construct immediately following them
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unless they are written, /*!< */, in which case they document the construct
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preceding them.
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