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Open vSwitch Windows Datapath Coding Style
==========================================
The coding style described in the Open vSwitch distribution gives the
flexiblity for each platform to use its own coding style for the kernel
datapath. This file describes the specific coding style used in most
of the C files in the Windows kernel datapath of the Open vSwitch distribution.
Most of the coding conventions applicable for the Open vSwitch distribution are
applicable to the Windows kernel datapath as well. There are some exceptions
and new guidlines owing to the commonly followed practices in Windows
kernel/driver code. They are noted as follows:
BASICS
Limit lines to 79 characters. Many times, this is not possible due to long
names of functions and it is fine to go beyond the characters limit. One
common example is when calling into NDIS functions.
TYPES
Use data types defined by Windows for most of the code. This is a common
practice in Windows driver code, and it makes integrating with the data
structures and functions defined by Windows easier. Example: DWORD and
BOOLEAN.
Use caution in portions of the code that interface with the OVS userspace.
OVS userspace does not use Windows specific data types, and when copying data
back and forth between kernel and userspace, care should be exercised.
NAMING
It is common practice to use camel casing for naming variables, functions
and files in Windows. For types, especially structures, unions and enums,
using all upper case letters with words seprated by '_' is common. These
practices can be used for OVS Windows datapath. However, use the following
guidelines:
Use lower case to begin the name of a variable.
Do not use '_' to begin the name of the variable. '_' is to be used to begin
the parameters of a pre-processor macro.
Use upper case to begin the name of a function, enum, file name etc.
Static functions whose scope is limited to the file they are defined in can
be prefixed with '_'. This is not mandatory though.
For types, use all upper case for all letters with words separated by '_'. If
camel casing is preferred, use upper case for the first letter.
It is a common practice to define a pointer type by prefixing the letter
'P' to a data type. The same practice can be followed here as well.
Example:
static __inline BOOLEAN
OvsDetectTunnelRxPkt(POVS_FORWARDING_CONTEXT ovsFwdCtx,
POVS_FLOW_KEY flowKey)
{
POVS_VPORT_ENTRY tunnelVport = NULL;
if (!flowKey->ipKey.nwFrag &&
flowKey->ipKey.nwProto == IPPROTO_UDP &&
flowKey->ipKey.l4.tpDst == VXLAN_UDP_PORT_NBO) {
tunnelVport = OvsGetTunnelVport(OVSWIN_VPORT_TYPE_VXLAN);
ovsActionStats.rxVxlan++;
}
if (tunnelVport) {
ASSERT(ovsFwdCtx->tunnelRxNic == NULL);
ovsFwdCtx->tunnelRxNic = tunnelVport;
return TRUE;
}
return FALSE;
}
For declaring variables of pointer type, use of the pointer data type
prefixed with 'P' is preferred over using '*'. This is not mandatory though,
and is only prescribed since it is a common practice in Windows.
Example, #1 is preferred over #2 though #2 is also equally correct:
1. PNET_BUFFER_LIST curNbl;
2. NET_BUFFER_LIST *curNbl;
COMMENTS
Comments should be written as full sentences that start with a
capital letter and end with a period. Putting two spaces between sentances is
not necessary.
// can be used for comments as long as the comment is a single line comment.
For block comments, use /* */ comments
FUNCTIONS
Put the return type, function name, and the braces that surround the
function's code on separate lines, all starting in column 0.
Before each function definition, write a comment that describes the
function's purpose, including each parameter, the return value, and
side effects. References to argument names should be given in
single-quotes, e.g. 'arg'. The comment should not include the
function name, nor need it follow any formal structure. The comment
does not need to describe how a function does its work, unless this
information is needed to use the function correctly (this is often
better done with comments *inside* the function).
Mention any side effects that the function has that are not obvious based on
the name of the function or based on the workflow it is called from.
In the interest of keeping comments describing functions similar in
structure, use the following template.
/*
*----------------------------------------------------------------------------
* Any description of the function, arguments, return types, assumptions and
* side effects.
*----------------------------------------------------------------------------
*/
SOURCE FILES
Each source file should state its license in a comment at the very
top, followed by a comment explaining the purpose of the code that is
in that file. The comment should explain how the code in the file
relates to code in other files. The goal is to allow a programmer to
quickly figure out where a given module fits into the larger system.
The first non-comment line in a .c source file should be:
#include <precomp.h>
#include directives should appear in the following order:
1. #include <precomp.h>
2. The module's own headers, if any. Including this before any
other header (besides <precomp.h>) ensures that the module's
header file is self-contained (see HEADER FILES) below.
3. Standard C library headers and other system headers, preferably
in alphabetical order. (Occasionally one encounters a set of
system headers that must be included in a particular order, in
which case that order must take precedence.)
4. Open vSwitch headers, in alphabetical order. Use "", not <>,
to specify Open vSwitch header names.
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