/*
 * An implementation of C11 stdatomic.h directly borrowed from FreeBSD
 * (original copyright follows), with minor modifications for
 * portability to other systems. Works for recent Clang (that
 * implement the feature c_atomic) and GCC 4.7+; includes
 * compatibility for GCC below 4.7 but I wouldn't recommend it.
 *
 * Caveats and limitations:
 * - Only the ``_Atomic parentheses'' notation is implemented, while
 *   the ``_Atomic space'' one is not.
 * - _Atomic types must be typedef'ed, or programs using them will
 *   not type check correctly (incompatible anonymous structure
 *   types).
 * - Non-scalar _Atomic types would require runtime support for
 *   runtime locking, which, as far as I know, is not currently
 *   available on any system.
 */

/*-
 * Copyright (c) 2011 Ed Schouten <ed@FreeBSD.org>
 *                    David Chisnall <theraven@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/include/stdatomic.h,v 1.10.2.2 2012/05/30 19:21:54 theraven Exp $
 */

#ifndef _STDATOMIC_H_
#define _STDATOMIC_H_

#include <stddef.h>
#include <stdint.h>

#if !defined(__has_feature)
#define __has_feature(x) 0
#endif
#if !defined(__has_builtin)
#define __has_builtin(x) 0
#endif
#if !defined(__GNUC_PREREQ__)
#if defined(__GNUC__) && defined(__GNUC_MINOR__)
#define __GNUC_PREREQ__(maj, min) ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
#else
#define __GNUC_PREREQ__(maj, min) 0
#endif
#endif

#if !defined(__CLANG_ATOMICS) && !defined(__GNUC_ATOMICS)
#if __has_feature(c_atomic)
#define __CLANG_ATOMICS
#elif __GNUC_PREREQ__(4, 7)
#define __GNUC_ATOMICS
#elif !defined(__GNUC__)
#error "stdatomic.h does not support your compiler"
#endif
#endif

#if !defined(__CLANG_ATOMICS)
#define _Atomic(T)                                                                                                                                                                                                                             \
    struct                                                                                                                                                                                                                                     \
    {                                                                                                                                                                                                                                          \
        volatile __typeof__(T) __val;                                                                                                                                                                                                          \
    }
#endif

/*
 * 7.17.2 Initialization.
 */

#if defined(__CLANG_ATOMICS)
#define ATOMIC_VAR_INIT(value)  (value)
#define atomic_init(obj, value) __c11_atomic_init(obj, value)
#else
#define ATOMIC_VAR_INIT(value) {.__val = (value)}
#define atomic_init(obj, value)                                                                                                                                                                                                                \
    do                                                                                                                                                                                                                                         \
    {                                                                                                                                                                                                                                          \
        (obj)->__val = (value);                                                                                                                                                                                                                \
    } while(0)
#endif

/*
 * Clang and recent GCC both provide predefined macros for the memory
 * orderings.  If we are using a compiler that doesn't define them, use the
 * clang values - these will be ignored in the fallback path.
 */

#ifndef __ATOMIC_RELAXED
#define __ATOMIC_RELAXED 0
#endif
#ifndef __ATOMIC_CONSUME
#define __ATOMIC_CONSUME 1
#endif
#ifndef __ATOMIC_ACQUIRE
#define __ATOMIC_ACQUIRE 2
#endif
#ifndef __ATOMIC_RELEASE
#define __ATOMIC_RELEASE 3
#endif
#ifndef __ATOMIC_ACQ_REL
#define __ATOMIC_ACQ_REL 4
#endif
#ifndef __ATOMIC_SEQ_CST
#define __ATOMIC_SEQ_CST 5
#endif

/*
 * 7.17.3 Order and consistency.
 *
 * The memory_order_* constants that denote the barrier behaviour of the
 * atomic operations.
 */

enum memory_order
{
    memory_order_relaxed = __ATOMIC_RELAXED,
    memory_order_consume = __ATOMIC_CONSUME,
    memory_order_acquire = __ATOMIC_ACQUIRE,
    memory_order_release = __ATOMIC_RELEASE,
    memory_order_acq_rel = __ATOMIC_ACQ_REL,
    memory_order_seq_cst = __ATOMIC_SEQ_CST
};

typedef enum memory_order memory_order;

/*
 * 7.17.4 Fences.
 */

#ifdef __CLANG_ATOMICS
#define atomic_thread_fence(order) __c11_atomic_thread_fence(order)
#define atomic_signal_fence(order) __c11_atomic_signal_fence(order)
#elif defined(__GNUC_ATOMICS)
#define atomic_thread_fence(order) __atomic_thread_fence(order)
#define atomic_signal_fence(order) __atomic_signal_fence(order)
#else
#define atomic_thread_fence(order) __sync_synchronize()
#define atomic_signal_fence(order) __asm volatile("" : : : "memory")
#endif

/*
 * 7.17.5 Lock-free property.
 */

#if defined(__CLANG_ATOMICS)
#define atomic_is_lock_free(obj) __c11_atomic_is_lock_free(sizeof(obj))
#elif defined(__GNUC_ATOMICS)
#define atomic_is_lock_free(obj) __atomic_is_lock_free(sizeof((obj)->__val))
#else
#define atomic_is_lock_free(obj) (sizeof((obj)->__val) <= sizeof(void *))
#endif

/*
 * 7.17.6 Atomic integer types.
 */

typedef _Atomic(_Bool)              atomic_bool;
typedef _Atomic(char)               atomic_char;
typedef _Atomic(signed char)        atomic_schar;
typedef _Atomic(unsigned char)      atomic_uchar;
typedef _Atomic(short)              atomic_short;
typedef _Atomic(unsigned short)     atomic_ushort;
typedef _Atomic(int)                atomic_int;
typedef _Atomic(unsigned int)       atomic_uint;
typedef _Atomic(long)               atomic_long;
typedef _Atomic(unsigned long)      atomic_ulong;
typedef _Atomic(long long)          atomic_llong;
typedef _Atomic(unsigned long long) atomic_ullong;
#if 0
typedef _Atomic(char16_t)		atomic_char16_t;
typedef _Atomic(char32_t)		atomic_char32_t;
#endif
typedef _Atomic(wchar_t)        atomic_wchar_t;
typedef _Atomic(int_least8_t)   atomic_int_least8_t;
typedef _Atomic(uint_least8_t)  atomic_uint_least8_t;
typedef _Atomic(int_least16_t)  atomic_int_least16_t;
typedef _Atomic(uint_least16_t) atomic_uint_least16_t;
typedef _Atomic(int_least32_t)  atomic_int_least32_t;
typedef _Atomic(uint_least32_t) atomic_uint_least32_t;
typedef _Atomic(int_least64_t)  atomic_int_least64_t;
typedef _Atomic(uint_least64_t) atomic_uint_least64_t;
typedef _Atomic(int_fast8_t)    atomic_int_fast8_t;
typedef _Atomic(uint_fast8_t)   atomic_uint_fast8_t;
typedef _Atomic(int_fast16_t)   atomic_int_fast16_t;
typedef _Atomic(uint_fast16_t)  atomic_uint_fast16_t;
typedef _Atomic(int_fast32_t)   atomic_int_fast32_t;
typedef _Atomic(uint_fast32_t)  atomic_uint_fast32_t;
typedef _Atomic(int_fast64_t)   atomic_int_fast64_t;
typedef _Atomic(uint_fast64_t)  atomic_uint_fast64_t;
typedef _Atomic(intptr_t)       atomic_intptr_t;
typedef _Atomic(uintptr_t)      atomic_uintptr_t;
typedef _Atomic(size_t)         atomic_size_t;
typedef _Atomic(ptrdiff_t)      atomic_ptrdiff_t;
typedef _Atomic(intmax_t)       atomic_intmax_t;
typedef _Atomic(uintmax_t)      atomic_uintmax_t;

/*
 * 7.17.7 Operations on atomic types.
 */

/*
 * Compiler-specific operations.
 */

#if defined(__CLANG_ATOMICS)
#define atomic_compare_exchange_strong_explicit(object, expected, desired, success, failure) __c11_atomic_compare_exchange_strong(object, expected, desired, success, failure)
#define atomic_compare_exchange_weak_explicit(object, expected, desired, success, failure)   __c11_atomic_compare_exchange_weak(object, expected, desired, success, failure)
#define atomic_exchange_explicit(object, desired, order)                                     __c11_atomic_exchange(object, desired, order)
#define atomic_fetch_add_explicit(object, operand, order)                                    __c11_atomic_fetch_add(object, operand, order)
#define atomic_fetch_and_explicit(object, operand, order)                                    __c11_atomic_fetch_and(object, operand, order)
#define atomic_fetch_or_explicit(object, operand, order)                                     __c11_atomic_fetch_or(object, operand, order)
#define atomic_fetch_sub_explicit(object, operand, order)                                    __c11_atomic_fetch_sub(object, operand, order)
#define atomic_fetch_xor_explicit(object, operand, order)                                    __c11_atomic_fetch_xor(object, operand, order)
#define atomic_load_explicit(object, order)                                                  __c11_atomic_load(object, order)
#define atomic_store_explicit(object, desired, order)                                        __c11_atomic_store(object, desired, order)
#elif defined(__GNUC_ATOMICS)
#define atomic_compare_exchange_strong_explicit(object, expected, desired, success, failure) __atomic_compare_exchange_n(&(object)->__val, expected, desired, 0, success, failure)
#define atomic_compare_exchange_weak_explicit(object, expected, desired, success, failure)   __atomic_compare_exchange_n(&(object)->__val, expected, desired, 1, success, failure)
#define atomic_exchange_explicit(object, desired, order)                                     __atomic_exchange_n(&(object)->__val, desired, order)
#define atomic_fetch_add_explicit(object, operand, order)                                    __atomic_fetch_add(&(object)->__val, operand, order)
#define atomic_fetch_and_explicit(object, operand, order)                                    __atomic_fetch_and(&(object)->__val, operand, order)
#define atomic_fetch_or_explicit(object, operand, order)                                     __atomic_fetch_or(&(object)->__val, operand, order)
#define atomic_fetch_sub_explicit(object, operand, order)                                    __atomic_fetch_sub(&(object)->__val, operand, order)
#define atomic_fetch_xor_explicit(object, operand, order)                                    __atomic_fetch_xor(&(object)->__val, operand, order)
#define atomic_load_explicit(object, order)                                                  __atomic_load_n(&(object)->__val, order)
#define atomic_store_explicit(object, desired, order)                                        __atomic_store_n(&(object)->__val, desired, order)
#else
#define atomic_compare_exchange_strong_explicit(object, expected, desired, success, failure)                                                                                                                                                   \
    ({                                                                                                                                                                                                                                         \
        __typeof__((object)->__val) __v;                                                                                                                                                                                                       \
        _Bool                       __r;                                                                                                                                                                                                       \
        __v = __sync_val_compare_and_swap(&(object)->__val, *(expected), desired);                                                                                                                                                             \
        __r = *(expected) == __v;                                                                                                                                                                                                              \
        *(expected) = __v;                                                                                                                                                                                                                     \
        __r;                                                                                                                                                                                                                                   \
    })

#define atomic_compare_exchange_weak_explicit(object, expected, desired, success, failure) atomic_compare_exchange_strong_explicit(object, expected, desired, success, failure)
#if __has_builtin(__sync_swap)
/* Clang provides a full-barrier atomic exchange - use it if available. */
#define atomic_exchange_explicit(object, desired, order) __sync_swap(&(object)->__val, desired)
#else
/*
 * __sync_lock_test_and_set() is only an acquire barrier in theory (although in
 * practice it is usually a full barrier) so we need an explicit barrier after
 * it.
 */
#define atomic_exchange_explicit(object, desired, order)                                                                                                                                                                                       \
    ({                                                                                                                                                                                                                                         \
        __typeof__((object)->__val) __v;                                                                                                                                                                                                       \
        __v = __sync_lock_test_and_set(&(object)->__val, desired);                                                                                                                                                                             \
        __sync_synchronize();                                                                                                                                                                                                                  \
        __v;                                                                                                                                                                                                                                   \
    })
#endif
#define atomic_fetch_add_explicit(object, operand, order) __sync_fetch_and_add(&(object)->__val, operand)
#define atomic_fetch_and_explicit(object, operand, order) __sync_fetch_and_and(&(object)->__val, operand)
#define atomic_fetch_or_explicit(object, operand, order)  __sync_fetch_and_or(&(object)->__val, operand)
#define atomic_fetch_sub_explicit(object, operand, order) __sync_fetch_and_sub(&(object)->__val, operand)
#define atomic_fetch_xor_explicit(object, operand, order) __sync_fetch_and_xor(&(object)->__val, operand)
#define atomic_load_explicit(object, order)               __sync_fetch_and_add(&(object)->__val, 0)
#define atomic_store_explicit(object, desired, order)                                                                                                                                                                                          \
    do                                                                                                                                                                                                                                         \
    {                                                                                                                                                                                                                                          \
        __sync_synchronize();                                                                                                                                                                                                                  \
        (object)->__val = (desired);                                                                                                                                                                                                           \
        __sync_synchronize();                                                                                                                                                                                                                  \
    } while(0)
#endif

/*
 * Convenience functions.
 */

#define atomic_compare_exchange_strong(object, expected, desired) atomic_compare_exchange_strong_explicit(object, expected, desired, memory_order_seq_cst, memory_order_seq_cst)
#define atomic_compare_exchange_weak(object, expected, desired)   atomic_compare_exchange_weak_explicit(object, expected, desired, memory_order_seq_cst, memory_order_seq_cst)
#define atomic_exchange(object, desired)                          atomic_exchange_explicit(object, desired, memory_order_seq_cst)
#define atomic_fetch_add(object, operand)                         atomic_fetch_add_explicit(object, operand, memory_order_seq_cst)
#define atomic_fetch_and(object, operand)                         atomic_fetch_and_explicit(object, operand, memory_order_seq_cst)
#define atomic_fetch_or(object, operand)                          atomic_fetch_or_explicit(object, operand, memory_order_seq_cst)
#define atomic_fetch_sub(object, operand)                         atomic_fetch_sub_explicit(object, operand, memory_order_seq_cst)
#define atomic_fetch_xor(object, operand)                         atomic_fetch_xor_explicit(object, operand, memory_order_seq_cst)
#define atomic_load(object)                                       atomic_load_explicit(object, memory_order_seq_cst)
#define atomic_store(object, desired)                             atomic_store_explicit(object, desired, memory_order_seq_cst)

/*
 * 7.17.8 Atomic flag type and operations.
 */

typedef atomic_bool atomic_flag;

#define ATOMIC_FLAG_INIT                                 ATOMIC_VAR_INIT(0)

#define atomic_flag_clear_explicit(object, order)        atomic_store_explicit(object, 0, order)
#define atomic_flag_test_and_set_explicit(object, order) atomic_compare_exchange_strong_explicit(object, 0, 1, order, order)

#define atomic_flag_clear(object)                        atomic_flag_clear_explicit(object, memory_order_seq_cst)
#define atomic_flag_test_and_set(object)                 atomic_flag_test_and_set_explicit(object, memory_order_seq_cst)

#endif /* !_STDATOMIC_H_ */
