libmdbx/src/atomics-types.h

/// \copyright SPDX-License-Identifier: Apache-2.0
/// \author Леонид Юрьев aka Leonid Yuriev <leo@yuriev.ru> \date 2015-2024

#pragma once

#include "essentials.h"

#ifndef MDBX_64BIT_ATOMIC
#error "The MDBX_64BIT_ATOMIC must be defined before"
#endif /* MDBX_64BIT_ATOMIC */

#ifndef MDBX_64BIT_CAS
#error "The MDBX_64BIT_CAS must be defined before"
#endif /* MDBX_64BIT_CAS */

#if defined(__cplusplus) && !defined(__STDC_NO_ATOMICS__) && __has_include(<cstdatomic>)
#include <cstdatomic>
#define MDBX_HAVE_C11ATOMICS
#elif !defined(__cplusplus) &&                                                 \
    (__STDC_VERSION__ >= 201112L || __has_extension(c_atomic)) &&              \
    !defined(__STDC_NO_ATOMICS__) &&                                           \
    (__GNUC_PREREQ(4, 9) || __CLANG_PREREQ(3, 8) ||                            \
     !(defined(__GNUC__) || defined(__clang__)))
#include <stdatomic.h>
#define MDBX_HAVE_C11ATOMICS
#elif defined(__GNUC__) || defined(__clang__)
#elif defined(_MSC_VER)
#pragma warning(disable : 4163) /* 'xyz': not available as an intrinsic */
#pragma warning(disable : 4133) /* 'function': incompatible types - from       \
                                   'size_t' to 'LONGLONG' */
#pragma warning(disable : 4244) /* 'return': conversion from 'LONGLONG' to     \
                                   'std::size_t', possible loss of data */
#pragma warning(disable : 4267) /* 'function': conversion from 'size_t' to     \
                                   'long', possible loss of data */
#pragma intrinsic(_InterlockedExchangeAdd, _InterlockedCompareExchange)
#pragma intrinsic(_InterlockedExchangeAdd64, _InterlockedCompareExchange64)
#elif defined(__APPLE__)
#include <libkern/OSAtomic.h>
#else
#error FIXME atomic-ops
#endif

typedef enum mdbx_memory_order {
  mo_Relaxed,
  mo_AcquireRelease
  /* , mo_SequentialConsistency */
} mdbx_memory_order_t;

typedef union {
  volatile uint32_t weak;
#ifdef MDBX_HAVE_C11ATOMICS
  volatile _Atomic uint32_t c11a;
#endif /* MDBX_HAVE_C11ATOMICS */
} mdbx_atomic_uint32_t;

typedef union {
  volatile uint64_t weak;
#if defined(MDBX_HAVE_C11ATOMICS) && (MDBX_64BIT_CAS || MDBX_64BIT_ATOMIC)
  volatile _Atomic uint64_t c11a;
#endif
#if !defined(MDBX_HAVE_C11ATOMICS) || !MDBX_64BIT_CAS || !MDBX_64BIT_ATOMIC
  __anonymous_struct_extension__ struct {
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
    mdbx_atomic_uint32_t low, high;
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
    mdbx_atomic_uint32_t high, low;
#else
#error "FIXME: Unsupported byte order"
#endif /* __BYTE_ORDER__ */
  };
#endif
} mdbx_atomic_uint64_t;

#ifdef MDBX_HAVE_C11ATOMICS

/* Crutches for C11 atomic compiler's bugs */
#if defined(__e2k__) && defined(__LCC__) && __LCC__ < /* FIXME */ 127
#define MDBX_c11a_ro(type, ptr) (&(ptr)->weak)
#define MDBX_c11a_rw(type, ptr) (&(ptr)->weak)
#elif defined(__clang__) && __clang__ < 8
#define MDBX_c11a_ro(type, ptr) ((volatile _Atomic(type) *)&(ptr)->c11a)
#define MDBX_c11a_rw(type, ptr) (&(ptr)->c11a)
#else
#define MDBX_c11a_ro(type, ptr) (&(ptr)->c11a)
#define MDBX_c11a_rw(type, ptr) (&(ptr)->c11a)
#endif /* Crutches for C11 atomic compiler's bugs */

#define mo_c11_store(fence)                                                    \
  (((fence) == mo_Relaxed)          ? memory_order_relaxed                     \
   : ((fence) == mo_AcquireRelease) ? memory_order_release                     \
                                    : memory_order_seq_cst)
#define mo_c11_load(fence)                                                     \
  (((fence) == mo_Relaxed)          ? memory_order_relaxed                     \
   : ((fence) == mo_AcquireRelease) ? memory_order_acquire                     \
                                    : memory_order_seq_cst)

#endif /* MDBX_HAVE_C11ATOMICS */

#define SAFE64_INVALID_THRESHOLD UINT64_C(0xffffFFFF00000000)