ovs/include/openvswitch/util.h

/*
 * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef OPENVSWITCH_UTIL_H
#define OPENVSWITCH_UTIL_H 1

#include <openvswitch/version.h>
#include <openvswitch/compiler.h>

#ifdef __cplusplus
extern "C" {
#endif

void ovs_set_program_name__(const char *name, const char *version,
                            const char *date, const char *time);

#define ovs_set_program_name(name, version) \
        ovs_set_program_name__(name, version, __DATE__, __TIME__)

const char *ovs_get_program_name(void);
const char *ovs_get_program_version(void);

/* Expands to a string that looks like "<file>:<line>", e.g. "tmp.c:10".
 *
 * See http://c-faq.com/ansi/stringize.html for an explanation of OVS_STRINGIZE
 * and OVS_STRINGIZE2. */
#define OVS_SOURCE_LOCATOR __FILE__ ":" OVS_STRINGIZE(__LINE__)
#define OVS_STRINGIZE(ARG) OVS_STRINGIZE2(ARG)
#define OVS_STRINGIZE2(ARG) #ARG

/* Saturating multiplication of "unsigned int"s: overflow yields UINT_MAX. */
#define OVS_SAT_MUL(X, Y)                                               \
    ((Y) == 0 ? 0                                                       \
     : (X) <= UINT_MAX / (Y) ? (unsigned int) (X) * (unsigned int) (Y)  \
     : UINT_MAX)

/* Like the standard assert macro, except writes the failure message to the
 * log. */
#ifndef NDEBUG
#define ovs_assert(CONDITION)                                           \
    if (!OVS_LIKELY(CONDITION)) {                                       \
        ovs_assert_failure(OVS_SOURCE_LOCATOR, __func__, #CONDITION);       \
    }
#else
#define ovs_assert(CONDITION) ((void) (CONDITION))
#endif
OVS_NO_RETURN void ovs_assert_failure(const char *, const char *, const char *);

/* This is a void expression that issues a compiler error if POINTER cannot be
 * compared for equality with the given pointer TYPE.  This generally means
 * that POINTER is a qualified or unqualified TYPE.  However,
 * BUILD_ASSERT_TYPE(POINTER, void *) will accept any pointer to object type,
 * because any pointer to object can be compared for equality with "void *".
 *
 * POINTER can be any expression.  The use of "sizeof" ensures that the
 * expression is not actually evaluated, so that any side effects of the
 * expression do not occur.
 *
 * The cast to int is present only to suppress an "expression using sizeof
 * bool" warning from "sparse" (see
 * http://permalink.gmane.org/gmane.comp.parsers.sparse/2967). */
#define BUILD_ASSERT_TYPE(POINTER, TYPE) \
    ((void) sizeof ((int) ((POINTER) == (TYPE) (POINTER))))

/* Casts 'pointer' to 'type' and issues a compiler warning if the cast changes
 * anything other than an outermost "const" or "volatile" qualifier.
 *
 * The cast to int is present only to suppress an "expression using sizeof
 * bool" warning from "sparse" (see
 * http://permalink.gmane.org/gmane.comp.parsers.sparse/2967). */
#define CONST_CAST(TYPE, POINTER)                               \
    (BUILD_ASSERT_TYPE(POINTER, TYPE),                          \
     (TYPE) (POINTER))

/* Given a pointer-typed lvalue OBJECT, expands to a pointer type that may be
 * assigned to OBJECT. */
#ifdef __GNUC__
#define OVS_TYPEOF(OBJECT) typeof(OBJECT)
#else
#define OVS_TYPEOF(OBJECT) void *
#endif

/* Given OBJECT of type pointer-to-structure, expands to the offset of MEMBER
 * within an instance of the structure.
 *
 * The GCC-specific version avoids the technicality of undefined behavior if
 * OBJECT is null, invalid, or not yet initialized.  This makes some static
 * checkers (like Coverity) happier.  But the non-GCC version does not actually
 * dereference any pointer, so it would be surprising for it to cause any
 * problems in practice.
 */
#ifdef __GNUC__
#define OBJECT_OFFSETOF(OBJECT, MEMBER) offsetof(typeof(*(OBJECT)), MEMBER)
#else
#define OBJECT_OFFSETOF(OBJECT, MEMBER) \
    ((char *) &(OBJECT)->MEMBER - (char *) (OBJECT))
#endif

/* Yields the size of MEMBER within STRUCT. */
#define MEMBER_SIZEOF(STRUCT, MEMBER) (sizeof(((STRUCT *) NULL)->MEMBER))

/* Yields the offset of the end of MEMBER within STRUCT. */
#define OFFSETOFEND(STRUCT, MEMBER) \
        (offsetof(STRUCT, MEMBER) + MEMBER_SIZEOF(STRUCT, MEMBER))

/* Given POINTER, the address of the given MEMBER in a STRUCT object, returns
   the STRUCT object. */
#define CONTAINER_OF(POINTER, STRUCT, MEMBER)                           \
        ((STRUCT *) (void *) ((char *) (POINTER) - offsetof (STRUCT, MEMBER)))

/* Given POINTER, the address of the given MEMBER within an object of the type
 * that that OBJECT points to, returns OBJECT as an assignment-compatible
 * pointer type (either the correct pointer type or "void *").  OBJECT must be
 * an lvalue.
 *
 * This is the same as CONTAINER_OF except that it infers the structure type
 * from the type of '*OBJECT'. */
#define OBJECT_CONTAINING(POINTER, OBJECT, MEMBER)                      \
    ((OVS_TYPEOF(OBJECT)) (void *)                                      \
     ((char *) (POINTER) - OBJECT_OFFSETOF(OBJECT, MEMBER)))

/* Given POINTER, the address of the given MEMBER within an object of the type
 * that that OBJECT points to, assigns the address of the outer object to
 * OBJECT, which must be an lvalue.
 *
 * Evaluates to (void) 0 as the result is not to be used. */
#define ASSIGN_CONTAINER(OBJECT, POINTER, MEMBER) \
    ((OBJECT) = OBJECT_CONTAINING(POINTER, OBJECT, MEMBER), (void) 0)

/* As explained in the comment above OBJECT_OFFSETOF(), non-GNUC compilers
 * like MSVC will complain about un-initialized variables if OBJECT
 * hasn't already been initialized. To prevent such warnings, INIT_CONTAINER()
 * can be used as a wrapper around ASSIGN_CONTAINER. */
#define INIT_CONTAINER(OBJECT, POINTER, MEMBER) \
    ((OBJECT) = NULL, ASSIGN_CONTAINER(OBJECT, POINTER, MEMBER))

#ifdef __cplusplus
}
#endif

#endif