osi/include/osi.h

/******************************************************************************
 *
 *  Copyright (C) 2016 Google, 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.
 *
 ******************************************************************************/

#pragma once

#include <stdbool.h>
#include <stdint.h>

#define UNUSED_ATTR __attribute__((unused))
#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
#define INVALID_FD (-1)

#define CONCAT(a, b) a##b

// Use during compile time to check conditional values
// NOTE: The the failures will present as a generic error
// "error: initialization makes pointer from integer without a cast"
// but the file and line number will present the condition that
// failed.
#define DUMMY_COUNTER(c) CONCAT(__osi_dummy_, c)
#define DUMMY_PTR DUMMY_COUNTER(__COUNTER__)

// base/macros.h defines a COMPILE_ASSERT macro to the C++11 keyword
// "static_assert" (it undef's COMPILE_ASSERT before redefining it).
// C++ code that includes base and osi/include/osi.h can thus easily default to
// the definition from libbase but we should check here to avoid compile errors.
#ifndef COMPILE_ASSERT
#define COMPILE_ASSERT(COND) \
  typedef int failed_compile_assert[(COND) ? 1 : -1] __attribute__((unused))
#endif  // COMPILE_ASSERT

// Macros for safe integer to pointer conversion. In the C language, data is
// commonly cast to opaque pointer containers and back for generic parameter
// passing in callbacks. These macros should be used sparingly in new code
// (never in C++ code). Whenever integers need to be passed as a pointer, use
// these macros.
#define PTR_TO_UINT(p) ((unsigned int)((uintptr_t)(p)))
#define UINT_TO_PTR(u) ((void*)((uintptr_t)(u)))

#define PTR_TO_INT(p) ((int)((intptr_t)(p)))
#define INT_TO_PTR(i) ((void*)((intptr_t)(i)))

// Obtain a random number between 0 and INT_MAX inclusive.
// Taken from a system random source such as /dev/random.
// No guarantees of distribution are made.
// Effort is made for this to come from a real random source.
int osi_rand(void);

// Re-run |fn| system call until the system call doesn't cause EINTR.
#define OSI_NO_INTR(fn) \
  do {                  \
  } while ((fn) == -1 && errno == EINTR)