--- /dev/null
+ Open vSwitch Coding Style
+ =========================
+
+This file describes the coding style used in most C files in the Open
+vSwitch distribution. However, Linux kernel code datapath directory
+follows the Linux kernel's established coding conventions.
+
+BASICS
+
+ Limit lines to 79 characters.
+
+ Use form feeds (control+L) to divide long source files into logical
+pieces. A form feed should appear as the only character on a line.
+
+ Do not use tabs for indentation.
+
+ Avoid trailing spaces on lines.
+
+
+NAMING
+
+ Use names that explain the purpose of a function or object.
+
+ Use underscores to separate words in an identifier: multi_word_name.
+
+ Use lowercase for most names. Use uppercase for macros, macro
+parameters, and members of enumerations.
+
+ Give arrays names that are plural.
+
+ Pick a unique name prefix (ending with an underscore) for each
+module, and apply that prefix to all of that module's externally
+visible names. Names of macro parameters, struct and union members,
+and parameters in function prototypes are not considered externally
+visible for this purpose.
+
+ Do not use names that begin with _. If you need a name for
+"internal use only", use __ as a suffix instead of a prefix.
+
+ Avoid negative names: "found" is a better name than "not_found".
+
+ In names, a "size" is a count of bytes, a "length" is a count of
+characters. A buffer has size, but a string has length. The length
+of a string does not include the null terminator, but the size of the
+buffer that contains the string does.
+
+
+COMMENTS
+
+ Comments should be written as full sentences that start with a
+capital letter and end with a period. Put two spaces between
+sentences.
+
+ Write block comments as shown below. You may put the /* and */ on
+the same line as comment text if you prefer.
+
+ /*
+ * We redirect stderr to /dev/null because we often want to remove all
+ * traffic control configuration on a port so its in a known state. If
+ * this done when there is no such configuration, tc complains, so we just
+ * always ignore it.
+ */
+
+ Each function and each variable declared outside a function, and
+each struct, union, and typedef declaration should be preceded by a
+comment. See FUNCTION DEFINITIONS below for function comment
+guidelines.
+
+ Each struct and union member should each have an inline comment that
+explains its meaning. structs and unions with many members should be
+additionally divided into logical groups of members by block comments,
+e.g.:
+
+ /* An event that will wake the following call to poll_block(). */
+ struct poll_waiter {
+ /* Set when the waiter is created. */
+ struct list node; /* Element in global waiters list. */
+ int fd; /* File descriptor. */
+ short int events; /* Events to wait for (POLLIN, POLLOUT). */
+ poll_fd_func *function; /* Callback function, if any, or null. */
+ void *aux; /* Argument to callback function. */
+ struct backtrace *backtrace; /* Event that created waiter, or null. */
+
+ /* Set only when poll_block() is called. */
+ struct pollfd *pollfd; /* Pointer to element of the pollfds array
+ (null if added from a callback). */
+ };
+
+ Use XXX or FIXME comments to mark code that needs work.
+
+ Don't use // comments.
+
+ Don't comment out or #if 0 out code. Just remove it. The code that
+was there will still be in version control history.
+
+
+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).
+
+ Simple static functions do not need a comment.
+
+ Within a file, non-static functions should come first, in the order
+that they are declared in the header file, followed by static
+functions. Static functions should be in one or more separate pages
+(separated by form feed characters) in logical groups. A commonly
+useful way to divide groups is by "level", with high-level functions
+first, followed by groups of progressively lower-level functions.
+This makes it easy for the program's reader to see the top-down
+structure by reading from top to bottom.
+
+ All function declarations and definitions should include a
+prototype. Empty parentheses, e.g. "int foo();", do not include a
+prototype (they state that the function's parameters are unknown);
+write "void" in parentheses instead, e.g. "int foo(void);".
+
+ Prototypes for static functions should either all go at the top of
+the file, separated into groups by blank lines, or they should appear
+at the top of each page of functions. Don't comment individual
+prototypes, but a comment on each group of prototypes is often
+appropriate.
+
+ In the absence of good reasons for another order, the following
+parameter order is preferred. One notable exception is that data
+parameters and their corresponding size parameters should be paired.
+
+ 1. The primary object being manipulated, if any (equivalent to the
+ "this" pointer in C++).
+ 2. Input-only parameters.
+ 3. Input/output parameters.
+ 4. Output-only parameters.
+ 5. Status parameter.
+
+ Example:
+
+ /* Stores the features supported by 'netdev' into each of '*current',
+ * '*advertised', '*supported', and '*peer' that are non-null. Each value
+ * is a bitmap of "enum ofp_port_features" bits, in host byte order.
+ * Returns 0 if successful, otherwise a positive errno value. On failure,
+ * all of the passed-in values are set to 0. */
+ int
+ netdev_get_features(struct netdev *netdev,
+ uint32_t *current, uint32_t *advertised,
+ uint32_t *supported, uint32_t *peer)
+ {
+ ...
+ }
+
+
+FUNCTION PROTOTYPES
+
+ Put the return type and function name on the same line in a function
+prototype:
+
+ static const struct option_class *get_option_class(int code);
+
+
+ Omit parameter names from function prototypes when the names do not
+give useful information, e.g.:
+
+ int netdev_get_mtu(const struct netdev *);
+
+
+STATEMENTS
+
+ Indent each level of code with 4 spaces. Use BSD-style brace
+placement:
+
+ if (a()) {
+ b();
+ d();
+ }
+
+ Put a space between "if", "while", "for", etc. and the expressions
+that follow them.
+
+ Enclose single statements in braces:
+
+ if (a > b) {
+ return a;
+ } else {
+ return b;
+ }
+
+ Use comments and blank lines to divide long functions into logical
+groups of statements.
+
+ Avoid assignments inside "if" and "while" conditions.
+
+ Do not put gratuitous parentheses around the expression in a return
+statement, that is, write "return 0;" and not "return(0);"
+
+ Write only one statement per line.
+
+ Indent "switch" statements like this:
+
+ switch (conn->state) {
+ case S_RECV:
+ error = run_connection_input(conn);
+ break;
+
+ case S_PROCESS:
+ error = 0;
+ break;
+
+ case S_SEND:
+ error = run_connection_output(conn);
+ break;
+
+ default:
+ NOT_REACHED();
+ }
+
+ "switch" statements with very short, uniform cases may use an
+abbreviated style:
+
+ switch (code) {
+ case 200: return "OK";
+ case 201: return "Created";
+ case 202: return "Accepted";
+ case 204: return "No Content";
+ default: return "Unknown";
+ }
+
+ Use "for (;;)" to write an infinite loop.
+
+ In an if/else construct where one branch is the "normal" or "common"
+case and the other branch is the "uncommon" or "error" case, put the
+common case after the "if", not the "else". This is a form of
+documentation. It also places the most important code in sequential
+order without forcing the reader to visually skip past less important
+details. (Some compilers also assume that the "if" branch is the more
+common case, so this can be a real form of optimization as well.)
+
+
+MACROS
+
+ Don't define an object-like macro if an enum can be used instead.
+
+ Don't define a function-like macro if a "static inline" function
+can be used instead.
+
+ If a macro's definition contains multiple statements, enclose them
+with "do { ... } while (0)" to allow them to work properly in all
+syntactic circumstances.
+
+ Do use macros to eliminate the need to update different parts of a
+single file in parallel, e.g. a list of enums and an array that gives
+the name of each enum. For example:
+
+ /* Logging importance levels. */
+ #define VLOG_LEVELS \
+ VLOG_LEVEL(EMER, LOG_ALERT) \
+ VLOG_LEVEL(ERR, LOG_ERR) \
+ VLOG_LEVEL(WARN, LOG_WARNING) \
+ VLOG_LEVEL(INFO, LOG_NOTICE) \
+ VLOG_LEVEL(DBG, LOG_DEBUG)
+ enum vlog_level {
+ #define VLOG_LEVEL(NAME, SYSLOG_LEVEL) VLL_##NAME,
+ VLOG_LEVELS
+ #undef VLOG_LEVEL
+ VLL_N_LEVELS
+ };
+
+ /* Name for each logging level. */
+ static const char *level_names[VLL_N_LEVELS] = {
+ #define VLOG_LEVEL(NAME, SYSLOG_LEVEL) #NAME,
+ VLOG_LEVELS
+ #undef VLOG_LEVEL
+ };
+
+
+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 <config.h>
+
+#include directives should appear in the following order:
+
+ 1. #include <config.h>
+
+ 2. The module's own headers, if any. Including this before any
+ other header (besides <config.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.
+
+
+HEADER FILES
+
+ Each header file should start with its license, as described under
+SOURCE FILES above, followed by a "header guard" to make the header
+file idempotent, like so:
+
+ #ifndef NETDEV_H
+ #define NETDEV_H 1
+
+ ...
+
+ #endif /* netdev.h */
+
+ Header files should be self-contained; that is, they should #include
+whatever additional headers are required, without requiring the client
+to #include them for it.
+
+ Don't define the members of a struct or union in a header file,
+unless client code is actually intended to access them directly or if
+the definition is otherwise actually needed (e.g. inline functions
+defined in the header need them).
+
+ Similarly, don't #include a header file just for the declaration of
+a struct or union tag (e.g. just for "struct <name>;"). Just declare
+the tag yourself. This reduces the number of header file
+dependencies.
+
+
+TYPES
+
+ Use typedefs sparingly. Code is clearer if the actual type is
+visible at the point of declaration. Do not, in general, declare a
+typedef for a struct, union, or enum. Do not declare a typedef for a
+pointer type, because this can be very confusing to the reader.
+
+ A function type is a good use for a typedef because it can clarify
+code. The type should be a function type, not a pointer-to-function
+type. That way, the typedef name can be used to declare function
+prototypes. (It cannot be used for function definitions, because that
+is explicitly prohibited by C89 and C99.)
+
+ You may assume that "char" is exactly 8 bits and that "int" and
+"long" are at least 32 bits.
+
+ Don't assume that "long" is big enough to hold a pointer. If you
+need to cast a pointer to an integer, use "intptr_t" or "uintptr_t"
+from <stdint.h>.
+
+ Use the int<N>_t and uint<N>_t types from <stdint.h> for exact-width
+integer types. Use the PRId<N>, PRIu<N>, and PRIx<N> macros from
+<inttypes.h> for formatting them with printf() and related functions.
+
+ Use %zu to format size_t with printf().
+
+ Use bit-fields sparingly. Do not use bit-fields for layout of
+network protocol fields or in other circumstances where the exact
+format is important.
+
+ Declare bit-fields to be type "unsigned int" or "signed int". Do
+*not* declare bit-fields of type "int": C89 allows these to be either
+signed or unsigned according to the compiler's whim. (A 1-bit
+bit-field of type "int" may have a range of -1...0!) Do not declare
+bit-fields of type _Bool or enum or any other type, because these are
+not portable.
+
+ Try to order structure members such that they pack well on a system
+with 2-byte "short", 4-byte "int", and 4- or 8-byte "long" and pointer
+types. Prefer clear organization over size optimization unless you
+are convinced there is a size or speed benefit.
+
+ Pointer declarators bind to the variable name, not the type name.
+Write "int *x", not "int* x" and definitely not "int * x".
+
+
+EXPRESSIONS
+
+ Put one space on each side of infix binary and ternary operators:
+
+ * / %
+ + -
+ << >>
+ < <= > >=
+ == !=
+ &
+ ^
+ |
+ &&
+ ||
+ ?:
+ = += -= *= /= %= &= ^= |= <<= >>=
+
+ Avoid comma operators.
+
+ Do not put any white space around postfix, prefix, or grouping
+operators:
+
+ () [] -> .
+ ! ~ ++ -- + - * &
+
+Exception 1: Put a space after (but not before) the "sizeof" keyword.
+Exception 2: Put a space between the () used in a cast and the
+expression whose type is cast: (void *) 0.
+
+ Break long lines before binary operators and the ternary operators ?
+and :, rather than after them, e.g.
+
+ if (first_long_condition() || second_long_condition()
+ || third_long_condition())
+
+and
+
+ return (out_port != VIGP_CONTROL_PATH
+ ? alpheus_output_port(dp, skb, out_port)
+ : alpheus_output_control(dp, skb, fwd_save_skb(skb),
+ VIGR_ACTION));
+
+
+ Do not parenthesize the operands of && and || unless operator
+precedence makes it necessary, or unless the operands are themselves
+expressions that use && and ||. Thus:
+
+ if (!isdigit(s[0]) || !isdigit(s[1]) || !isdigit(s[2])) {
+ printf("string %s does not start with 3-digit code\n", s);
+ }
+
+but
+
+ if (rule && (!best || rule->priority > best->priority)) {
+ best = rule;
+ }
+
+ Do parenthesize a subexpression that must be split across more than
+one line, e.g.:
+
+ *idxp = ((l1_idx << PORT_ARRAY_L1_SHIFT)
+ | (l2_idx << PORT_ARRAY_L2_SHIFT)
+ | (l3_idx << PORT_ARRAY_L3_SHIFT));
+
+ Try to avoid casts. Don't cast the return value of malloc().
+
+ The "sizeof" operator is unique among C operators in that it accepts
+two very different kinds of operands: an expression or a type. In
+general, prefer to specify an expression, e.g. "int *x =
+xmalloc(sizeof *x);". When the operand of sizeof is an expression,
+there is no need to parenthesize that operand, and please don't.
+
+ Use the ARRAY_SIZE macro from lib/util.h to calculate the number of
+elements in an array.
+
+ When using a relational operator like "<" or "==", put an expression
+or variable argument on the left and a constant argument on the
+right, e.g. "x == 0", *not* "0 == x".
+
+
+BLANK LINES
+
+ Put one blank line between top-level definitions of functions and
+global variables.
+
+
+C DIALECT
+
+ Try to avoid using GCC extensions where possible.
+
+ Some C99 extensions are OK:
+
+ * Flexible array members (e.g. struct { int foo[]; }).
+
+ * "static inline" functions (but no other forms of "inline", for
+ which GCC and C99 have differing interpretations).
+
+ * "long long"
+
+ * <stdint.h> and <inttypes.h>.
+
+ * bool and <stdbool.h>, but don't assume that bool or _Bool can
+ only take on the values 0 or 1, because this behavior can't be
+ simulated on C89 compilers.
+
+ Don't use other C99 extensions, and especially:
+
+ * Don't use // comments.
+
+ * Don't use designated initializers (e.g. don't write "struct foo
+ foo = {.a = 1};" or "int a[] = {[2] = 5};").
+
+ * Don't mix declarations and code within a block.
+
+ * Don't use declarations in iteration statements (e.g. don't write
+ "for (int i = 0; i < 10; i++)").
+
+ * Don't put a trailing comma in an enum declaration (e.g. don't
+ write "enum { x = 1, };").
projects / openvswitch / commitdiff