/* https://en.wikipedia.org/wiki/Operating_system_abstraction_layer */

/*
 * Copyright 2015-2022 Leonid Yuriev <leo@yuriev.ru>
 * and other libmdbx authors: please see AUTHORS file.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted only as authorized by the OpenLDAP
 * Public License.
 *
 * A copy of this license is available in the file LICENSE in the
 * top-level directory of the distribution or, alternatively, at
 * <http://www.OpenLDAP.org/license.html>.
 */

#pragma once

/*----------------------------------------------------------------------------*/
/* C11 Atomics */

#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

/*----------------------------------------------------------------------------*/
/* Memory/Compiler barriers, cache coherence */

#if __has_include(<sys/cachectl.h>)
#include <sys/cachectl.h>
#elif defined(__mips) || defined(__mips__) || defined(__mips64) ||             \
    defined(__mips64__) || defined(_M_MRX000) || defined(_MIPS_) ||            \
    defined(__MWERKS__) || defined(__sgi)
/* MIPS should have explicit cache control */
#include <sys/cachectl.h>
#endif

MDBX_MAYBE_UNUSED static __inline void osal_compiler_barrier(void) {
#if defined(__clang__) || defined(__GNUC__)
  __asm__ __volatile__("" ::: "memory");
#elif defined(_MSC_VER)
  _ReadWriteBarrier();
#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
  __memory_barrier();
#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
  __compiler_barrier();
#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
    (defined(HP_IA64) || defined(__ia64))
  _Asm_sched_fence(/* LY: no-arg meaning 'all expect ALU', e.g. 0x3D3D */);
#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
    defined(__ppc64__) || defined(__powerpc64__)
  __fence();
#else
#error "Could not guess the kind of compiler, please report to us."
#endif
}

MDBX_MAYBE_UNUSED static __inline void osal_memory_barrier(void) {
#ifdef MDBX_HAVE_C11ATOMICS
  atomic_thread_fence(memory_order_seq_cst);
#elif defined(__ATOMIC_SEQ_CST)
#ifdef __clang__
  __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
#else
  __atomic_thread_fence(__ATOMIC_SEQ_CST);
#endif
#elif defined(__clang__) || defined(__GNUC__)
  __sync_synchronize();
#elif defined(_WIN32) || defined(_WIN64)
  MemoryBarrier();
#elif defined(__INTEL_COMPILER) /* LY: Intel Compiler may mimic GCC and MSC */
#if defined(__ia32__)
  _mm_mfence();
#else
  __mf();
#endif
#elif defined(__SUNPRO_C) || defined(__sun) || defined(sun)
  __machine_rw_barrier();
#elif (defined(_HPUX_SOURCE) || defined(__hpux) || defined(__HP_aCC)) &&       \
    (defined(HP_IA64) || defined(__ia64))
  _Asm_mf();
#elif defined(_AIX) || defined(__ppc__) || defined(__powerpc__) ||             \
    defined(__ppc64__) || defined(__powerpc64__)
  __lwsync();
#else
#error "Could not guess the kind of compiler, please report to us."
#endif
}

/*----------------------------------------------------------------------------*/
/* system-depended definitions */

#if defined(_WIN32) || defined(_WIN64)
#define HAVE_SYS_STAT_H
#define HAVE_SYS_TYPES_H
typedef HANDLE osal_thread_t;
typedef unsigned osal_thread_key_t;
#define MAP_FAILED NULL
#define HIGH_DWORD(v) ((DWORD)((sizeof(v) > 4) ? ((uint64_t)(v) >> 32) : 0))
#define THREAD_CALL WINAPI
#define THREAD_RESULT DWORD
typedef struct {
  HANDLE mutex;
  HANDLE event[2];
} osal_condpair_t;
typedef CRITICAL_SECTION osal_fastmutex_t;

#if !defined(_MSC_VER) && !defined(__try)
/* *INDENT-OFF* */
/* clang-format off */
#define __try
#define __except(COND) if (false)
/* *INDENT-ON* */
/* clang-format on */
#endif /* stub for MSVC's __try/__except */

#if MDBX_WITHOUT_MSVC_CRT

#ifndef osal_malloc
static inline void *osal_malloc(size_t bytes) {
  return HeapAlloc(GetProcessHeap(), 0, bytes);
}
#endif /* osal_malloc */

#ifndef osal_calloc
static inline void *osal_calloc(size_t nelem, size_t size) {
  return HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, nelem * size);
}
#endif /* osal_calloc */

#ifndef osal_realloc
static inline void *osal_realloc(void *ptr, size_t bytes) {
  return ptr ? HeapReAlloc(GetProcessHeap(), 0, ptr, bytes)
             : HeapAlloc(GetProcessHeap(), 0, bytes);
}
#endif /* osal_realloc */

#ifndef osal_free
static inline void osal_free(void *ptr) { HeapFree(GetProcessHeap(), 0, ptr); }
#endif /* osal_free */

#else /* MDBX_WITHOUT_MSVC_CRT */

#define osal_malloc malloc
#define osal_calloc calloc
#define osal_realloc realloc
#define osal_free free
#define osal_strdup _strdup

#endif /* MDBX_WITHOUT_MSVC_CRT */

#ifndef snprintf
#define snprintf _snprintf /* ntdll */
#endif

#ifndef vsnprintf
#define vsnprintf _vsnprintf /* ntdll */
#endif

#else /*----------------------------------------------------------------------*/

typedef pthread_t osal_thread_t;
typedef pthread_key_t osal_thread_key_t;
#define INVALID_HANDLE_VALUE (-1)
#define THREAD_CALL
#define THREAD_RESULT void *
typedef struct {
  pthread_mutex_t mutex;
  pthread_cond_t cond[2];
} osal_condpair_t;
typedef pthread_mutex_t osal_fastmutex_t;
#define osal_malloc malloc
#define osal_calloc calloc
#define osal_realloc realloc
#define osal_free free
#define osal_strdup strdup
#endif /* Platform */

#if __GLIBC_PREREQ(2, 12) || defined(__FreeBSD__) || defined(malloc_usable_size)
/* malloc_usable_size() already provided */
#elif defined(__APPLE__)
#define malloc_usable_size(ptr) malloc_size(ptr)
#elif defined(_MSC_VER) && !MDBX_WITHOUT_MSVC_CRT
#define malloc_usable_size(ptr) _msize(ptr)
#endif /* malloc_usable_size */

/*----------------------------------------------------------------------------*/
/* OS abstraction layer stuff */

MDBX_INTERNAL_VAR unsigned sys_pagesize;
MDBX_MAYBE_UNUSED MDBX_INTERNAL_VAR unsigned sys_pagesize_ln2,
    sys_allocation_granularity;

/* Get the size of a memory page for the system.
 * This is the basic size that the platform's memory manager uses, and is
 * fundamental to the use of memory-mapped files. */
MDBX_MAYBE_UNUSED MDBX_NOTHROW_CONST_FUNCTION static __inline size_t
osal_syspagesize(void) {
  assert(sys_pagesize > 0 && (sys_pagesize & (sys_pagesize - 1)) == 0);
  return sys_pagesize;
}

#if defined(_WIN32) || defined(_WIN64)
typedef wchar_t pathchar_t;
#define MDBX_PRIsPATH "ls"
#else
typedef char pathchar_t;
#define MDBX_PRIsPATH "s"
#endif

typedef struct osal_mmap {
  union {
    void *base;
    struct MDBX_lockinfo *lck;
  };
  mdbx_filehandle_t fd;
  size_t limit;   /* mapping length, but NOT a size of file nor DB */
  size_t current; /* mapped region size, i.e. the size of file and DB */
  uint64_t filesize /* in-process cache of a file size */;
#if defined(_WIN32) || defined(_WIN64)
  HANDLE section; /* memory-mapped section handle */
#endif
} osal_mmap_t;

typedef union bin128 {
  __anonymous_struct_extension__ struct { uint64_t x, y; };
  __anonymous_struct_extension__ struct { uint32_t a, b, c, d; };
} bin128_t;

#if defined(_WIN32) || defined(_WIN64)
typedef union osal_srwlock {
  __anonymous_struct_extension__ struct {
    long volatile readerCount;
    long volatile writerCount;
  };
  RTL_SRWLOCK native;
} osal_srwlock_t;
#endif /* Windows */

#ifndef MDBX_HAVE_PWRITEV
#if defined(_WIN32) || defined(_WIN64)

#define MDBX_HAVE_PWRITEV 0

#elif defined(__ANDROID_API__)

#if __ANDROID_API__ < 24
#define MDBX_HAVE_PWRITEV 0
#else
#define MDBX_HAVE_PWRITEV 1
#endif

#elif defined(__APPLE__) || defined(__MACH__) || defined(_DARWIN_C_SOURCE)

#if defined(MAC_OS_X_VERSION_MIN_REQUIRED) && defined(MAC_OS_VERSION_11_0) &&  \
    MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
/* FIXME: add checks for IOS versions, etc */
#define MDBX_HAVE_PWRITEV 1
#else
#define MDBX_HAVE_PWRITEV 0
#endif

#elif defined(_SC_IOV_MAX) || (defined(IOV_MAX) && IOV_MAX > 1)
#define MDBX_HAVE_PWRITEV 1
#else
#define MDBX_HAVE_PWRITEV 0
#endif
#endif /* MDBX_HAVE_PWRITEV */

typedef struct ior_item {
#if defined(_WIN32) || defined(_WIN64)
  OVERLAPPED ov;
#define ior_svg_gap4terminator 1
#define ior_sgv_element FILE_SEGMENT_ELEMENT
#else
  size_t offset;
#if MDBX_HAVE_PWRITEV
  size_t sgvcnt;
#define ior_svg_gap4terminator 0
#define ior_sgv_element struct iovec
#endif /* MDBX_HAVE_PWRITEV */
#endif /* !Windows */
  union {
    MDBX_val single;
#if defined(ior_sgv_element)
    ior_sgv_element sgv[1 + ior_svg_gap4terminator];
#endif /* ior_sgv_element */
  };
} ior_item_t;

typedef struct osal_ioring {
  unsigned slots_left;
  unsigned allocated;
#if defined(_WIN32) || defined(_WIN64)
#define IOR_STATE_LOCKED 1
  HANDLE overlapped_fd;
  unsigned pagesize;
  unsigned last_sgvcnt;
  size_t last_bytes;
  uint8_t direct, state, pagesize_ln2;
  unsigned event_stack;
  HANDLE *event_pool;
  volatile LONG async_waiting;
  volatile LONG async_completed;
  HANDLE async_done;

#define ior_last_sgvcnt(ior, item) (ior)->last_sgvcnt
#define ior_last_bytes(ior, item) (ior)->last_bytes
#elif MDBX_HAVE_PWRITEV
  unsigned last_bytes;
#define ior_last_sgvcnt(ior, item) (item)->sgvcnt
#define ior_last_bytes(ior, item) (ior)->last_bytes
#else
#define ior_last_sgvcnt(ior, item) (1)
#define ior_last_bytes(ior, item) (item)->single.iov_len
#endif /* !Windows */
  ior_item_t *last;
  ior_item_t *pool;
  char *boundary;
} osal_ioring_t;

#ifndef __cplusplus

/* Actually this is not ioring for now, but on the way. */
MDBX_INTERNAL_FUNC int osal_ioring_create(osal_ioring_t *
#if defined(_WIN32) || defined(_WIN64)
                                          ,
                                          bool enable_direct,
                                          mdbx_filehandle_t overlapped_fd
#endif /* Windows */
);
MDBX_INTERNAL_FUNC int osal_ioring_resize(osal_ioring_t *, size_t items);
MDBX_INTERNAL_FUNC void osal_ioring_destroy(osal_ioring_t *);
MDBX_INTERNAL_FUNC void osal_ioring_reset(osal_ioring_t *);
MDBX_INTERNAL_FUNC int osal_ioring_add(osal_ioring_t *ctx, const size_t offset,
                                       void *data, const size_t bytes);
typedef struct osal_ioring_write_result {
  int err;
  unsigned wops;
} osal_ioring_write_result_t;
MDBX_INTERNAL_FUNC osal_ioring_write_result_t
osal_ioring_write(osal_ioring_t *ior, mdbx_filehandle_t fd);

typedef struct iov_ctx iov_ctx_t;
MDBX_INTERNAL_FUNC void osal_ioring_walk(
    osal_ioring_t *ior, iov_ctx_t *ctx,
    void (*callback)(iov_ctx_t *ctx, size_t offset, void *data, size_t bytes));

MDBX_MAYBE_UNUSED static inline unsigned
osal_ioring_left(const osal_ioring_t *ior) {
  return ior->slots_left;
}

MDBX_MAYBE_UNUSED static inline unsigned
osal_ioring_used(const osal_ioring_t *ior) {
  return ior->allocated - ior->slots_left;
}

MDBX_MAYBE_UNUSED static inline int
osal_ioring_prepare(osal_ioring_t *ior, size_t items, size_t bytes) {
  items = (items > 32) ? items : 32;
#if defined(_WIN32) || defined(_WIN64)
  if (ior->direct) {
    const size_t npages = bytes >> ior->pagesize_ln2;
    items = (items > npages) ? items : npages;
  }
#else
  (void)bytes;
#endif
  items = (items < 65536) ? items : 65536;
  if (likely(ior->allocated >= items))
    return MDBX_SUCCESS;
  return osal_ioring_resize(ior, items);
}

/*----------------------------------------------------------------------------*/
/* libc compatibility stuff */

#if (!defined(__GLIBC__) && __GLIBC_PREREQ(2, 1)) &&                           \
    (defined(_GNU_SOURCE) || defined(_BSD_SOURCE))
#define osal_asprintf asprintf
#define osal_vasprintf vasprintf
#else
MDBX_MAYBE_UNUSED MDBX_INTERNAL_FUNC
    MDBX_PRINTF_ARGS(2, 3) int osal_asprintf(char **strp, const char *fmt, ...);
MDBX_INTERNAL_FUNC int osal_vasprintf(char **strp, const char *fmt, va_list ap);
#endif

#if !defined(MADV_DODUMP) && defined(MADV_CORE)
#define MADV_DODUMP MADV_CORE
#endif /* MADV_CORE -> MADV_DODUMP */

#if !defined(MADV_DONTDUMP) && defined(MADV_NOCORE)
#define MADV_DONTDUMP MADV_NOCORE
#endif /* MADV_NOCORE -> MADV_DONTDUMP */

MDBX_MAYBE_UNUSED MDBX_INTERNAL_FUNC void osal_jitter(bool tiny);
MDBX_MAYBE_UNUSED static __inline void jitter4testing(bool tiny);

/* max bytes to write in one call */
#if defined(_WIN64)
#define MAX_WRITE UINT32_C(0x10000000)
#elif defined(_WIN32)
#define MAX_WRITE UINT32_C(0x04000000)
#else
#define MAX_WRITE UINT32_C(0x3f000000)

#if defined(F_GETLK64) && defined(F_SETLK64) && defined(F_SETLKW64) &&         \
    !defined(__ANDROID_API__)
#define MDBX_F_SETLK F_SETLK64
#define MDBX_F_SETLKW F_SETLKW64
#define MDBX_F_GETLK F_GETLK64
#if (__GLIBC_PREREQ(2, 28) &&                                                  \
     (defined(__USE_LARGEFILE64) || defined(__LARGEFILE64_SOURCE) ||           \
      defined(_USE_LARGEFILE64) || defined(_LARGEFILE64_SOURCE))) ||           \
    defined(fcntl64)
#define MDBX_FCNTL fcntl64
#else
#define MDBX_FCNTL fcntl
#endif
#define MDBX_STRUCT_FLOCK struct flock64
#ifndef OFF_T_MAX
#define OFF_T_MAX UINT64_C(0x7fffFFFFfff00000)
#endif /* OFF_T_MAX */
#else
#define MDBX_F_SETLK F_SETLK
#define MDBX_F_SETLKW F_SETLKW
#define MDBX_F_GETLK F_GETLK
#define MDBX_FCNTL fcntl
#define MDBX_STRUCT_FLOCK struct flock
#endif /* MDBX_F_SETLK, MDBX_F_SETLKW, MDBX_F_GETLK */

#if defined(F_OFD_SETLK64) && defined(F_OFD_SETLKW64) &&                       \
    defined(F_OFD_GETLK64) && !defined(__ANDROID_API__)
#define MDBX_F_OFD_SETLK F_OFD_SETLK64
#define MDBX_F_OFD_SETLKW F_OFD_SETLKW64
#define MDBX_F_OFD_GETLK F_OFD_GETLK64
#else
#define MDBX_F_OFD_SETLK F_OFD_SETLK
#define MDBX_F_OFD_SETLKW F_OFD_SETLKW
#define MDBX_F_OFD_GETLK F_OFD_GETLK
#ifndef OFF_T_MAX
#define OFF_T_MAX                                                              \
  (((sizeof(off_t) > 4) ? INT64_MAX : INT32_MAX) & ~(size_t)0xFffff)
#endif /* OFF_T_MAX */
#endif /* MDBX_F_OFD_SETLK64, MDBX_F_OFD_SETLKW64, MDBX_F_OFD_GETLK64 */

#endif

#if defined(__linux__) || defined(__gnu_linux__)
MDBX_INTERNAL_VAR uint32_t linux_kernel_version;
MDBX_INTERNAL_VAR bool mdbx_RunningOnWSL1 /* Windows Subsystem 1 for Linux */;
#endif /* Linux */

#ifndef osal_strdup
LIBMDBX_API char *osal_strdup(const char *str);
#endif

MDBX_MAYBE_UNUSED static __inline int osal_get_errno(void) {
#if defined(_WIN32) || defined(_WIN64)
  DWORD rc = GetLastError();
#else
  int rc = errno;
#endif
  return rc;
}

#ifndef osal_memalign_alloc
MDBX_INTERNAL_FUNC int osal_memalign_alloc(size_t alignment, size_t bytes,
                                           void **result);
#endif
#ifndef osal_memalign_free
MDBX_INTERNAL_FUNC void osal_memalign_free(void *ptr);
#endif

MDBX_INTERNAL_FUNC int osal_condpair_init(osal_condpair_t *condpair);
MDBX_INTERNAL_FUNC int osal_condpair_lock(osal_condpair_t *condpair);
MDBX_INTERNAL_FUNC int osal_condpair_unlock(osal_condpair_t *condpair);
MDBX_INTERNAL_FUNC int osal_condpair_signal(osal_condpair_t *condpair,
                                            bool part);
MDBX_INTERNAL_FUNC int osal_condpair_wait(osal_condpair_t *condpair, bool part);
MDBX_INTERNAL_FUNC int osal_condpair_destroy(osal_condpair_t *condpair);

MDBX_INTERNAL_FUNC int osal_fastmutex_init(osal_fastmutex_t *fastmutex);
MDBX_INTERNAL_FUNC int osal_fastmutex_acquire(osal_fastmutex_t *fastmutex);
MDBX_INTERNAL_FUNC int osal_fastmutex_release(osal_fastmutex_t *fastmutex);
MDBX_INTERNAL_FUNC int osal_fastmutex_destroy(osal_fastmutex_t *fastmutex);

MDBX_INTERNAL_FUNC int osal_pwritev(mdbx_filehandle_t fd, struct iovec *iov,
                                    size_t sgvcnt, uint64_t offset);
MDBX_INTERNAL_FUNC int osal_pread(mdbx_filehandle_t fd, void *buf, size_t count,
                                  uint64_t offset);
MDBX_INTERNAL_FUNC int osal_pwrite(mdbx_filehandle_t fd, const void *buf,
                                   size_t count, uint64_t offset);
MDBX_INTERNAL_FUNC int osal_write(mdbx_filehandle_t fd, const void *buf,
                                  size_t count);

MDBX_INTERNAL_FUNC int
osal_thread_create(osal_thread_t *thread,
                   THREAD_RESULT(THREAD_CALL *start_routine)(void *),
                   void *arg);
MDBX_INTERNAL_FUNC int osal_thread_join(osal_thread_t thread);

enum osal_syncmode_bits {
  MDBX_SYNC_NONE = 0,
  MDBX_SYNC_KICK = 1,
  MDBX_SYNC_DATA = 2,
  MDBX_SYNC_SIZE = 4,
  MDBX_SYNC_IODQ = 8
};

MDBX_INTERNAL_FUNC int osal_fsync(mdbx_filehandle_t fd,
                                  const enum osal_syncmode_bits mode_bits);
MDBX_INTERNAL_FUNC int osal_ftruncate(mdbx_filehandle_t fd, uint64_t length);
MDBX_INTERNAL_FUNC int osal_fseek(mdbx_filehandle_t fd, uint64_t pos);
MDBX_INTERNAL_FUNC int osal_filesize(mdbx_filehandle_t fd, uint64_t *length);

enum osal_openfile_purpose {
  MDBX_OPEN_DXB_READ,
  MDBX_OPEN_DXB_LAZY,
  MDBX_OPEN_DXB_DSYNC,
#if defined(_WIN32) || defined(_WIN64)
  MDBX_OPEN_DXB_OVERLAPPED,
  MDBX_OPEN_DXB_OVERLAPPED_DIRECT,
#endif /* Windows */
  MDBX_OPEN_LCK,
  MDBX_OPEN_COPY,
  MDBX_OPEN_DELETE
};

MDBX_MAYBE_UNUSED static __inline bool osal_isdirsep(pathchar_t c) {
  return
#if defined(_WIN32) || defined(_WIN64)
      c == '\\' ||
#endif
      c == '/';
}

MDBX_INTERNAL_FUNC bool osal_pathequal(const pathchar_t *l, const pathchar_t *r,
                                       size_t len);
MDBX_INTERNAL_FUNC pathchar_t *osal_fileext(const pathchar_t *pathname,
                                            size_t len);
MDBX_INTERNAL_FUNC int osal_fileexists(const pathchar_t *pathname);
MDBX_INTERNAL_FUNC int osal_openfile(const enum osal_openfile_purpose purpose,
                                     const MDBX_env *env,
                                     const pathchar_t *pathname,
                                     mdbx_filehandle_t *fd,
                                     mdbx_mode_t unix_mode_bits);
MDBX_INTERNAL_FUNC int osal_closefile(mdbx_filehandle_t fd);
MDBX_INTERNAL_FUNC int osal_removefile(const pathchar_t *pathname);
MDBX_INTERNAL_FUNC int osal_removedirectory(const pathchar_t *pathname);
MDBX_INTERNAL_FUNC int osal_is_pipe(mdbx_filehandle_t fd);
MDBX_INTERNAL_FUNC int osal_lockfile(mdbx_filehandle_t fd, bool wait);

#define MMAP_OPTION_TRUNCATE 1
#define MMAP_OPTION_SEMAPHORE 2
MDBX_INTERNAL_FUNC int osal_mmap(const int flags, osal_mmap_t *map, size_t size,
                                 const size_t limit, const unsigned options);
MDBX_INTERNAL_FUNC int osal_munmap(osal_mmap_t *map);
#define MDBX_MRESIZE_MAY_MOVE 0x00000100
#define MDBX_MRESIZE_MAY_UNMAP 0x00000200
MDBX_INTERNAL_FUNC int osal_mresize(const int flags, osal_mmap_t *map,
                                    size_t size, size_t limit);
#if defined(_WIN32) || defined(_WIN64)
typedef struct {
  unsigned limit, count;
  HANDLE handles[31];
} mdbx_handle_array_t;
MDBX_INTERNAL_FUNC int
osal_suspend_threads_before_remap(MDBX_env *env, mdbx_handle_array_t **array);
MDBX_INTERNAL_FUNC int
osal_resume_threads_after_remap(mdbx_handle_array_t *array);
#endif /* Windows */
MDBX_INTERNAL_FUNC int osal_msync(const osal_mmap_t *map, size_t offset,
                                  size_t length,
                                  enum osal_syncmode_bits mode_bits);
MDBX_INTERNAL_FUNC int osal_check_fs_rdonly(mdbx_filehandle_t handle,
                                            const pathchar_t *pathname,
                                            int err);
MDBX_INTERNAL_FUNC int osal_check_fs_incore(mdbx_filehandle_t handle);

MDBX_MAYBE_UNUSED static __inline uint32_t osal_getpid(void) {
  STATIC_ASSERT(sizeof(mdbx_pid_t) <= sizeof(uint32_t));
#if defined(_WIN32) || defined(_WIN64)
  return GetCurrentProcessId();
#else
  STATIC_ASSERT(sizeof(pid_t) <= sizeof(uint32_t));
  return getpid();
#endif
}

MDBX_MAYBE_UNUSED static __inline uintptr_t osal_thread_self(void) {
  mdbx_tid_t thunk;
  STATIC_ASSERT(sizeof(uintptr_t) >= sizeof(thunk));
#if defined(_WIN32) || defined(_WIN64)
  thunk = GetCurrentThreadId();
#else
  thunk = pthread_self();
#endif
  return (uintptr_t)thunk;
}

#if !defined(_WIN32) && !defined(_WIN64)
#if defined(__ANDROID_API__) || defined(ANDROID) || defined(BIONIC)
MDBX_INTERNAL_FUNC int osal_check_tid4bionic(void);
#else
static __inline int osal_check_tid4bionic(void) { return 0; }
#endif /* __ANDROID_API__ || ANDROID) || BIONIC */

MDBX_MAYBE_UNUSED static __inline int
osal_pthread_mutex_lock(pthread_mutex_t *mutex) {
  int err = osal_check_tid4bionic();
  return unlikely(err) ? err : pthread_mutex_lock(mutex);
}
#endif /* !Windows */

MDBX_INTERNAL_FUNC uint64_t osal_monotime(void);
MDBX_INTERNAL_FUNC uint64_t osal_cputime(size_t *optional_page_faults);
MDBX_INTERNAL_FUNC uint64_t osal_16dot16_to_monotime(uint32_t seconds_16dot16);
MDBX_INTERNAL_FUNC uint32_t osal_monotime_to_16dot16(uint64_t monotime);

MDBX_MAYBE_UNUSED static inline uint32_t
osal_monotime_to_16dot16_noUnderflow(uint64_t monotime) {
  uint32_t seconds_16dot16 = osal_monotime_to_16dot16(monotime);
  return seconds_16dot16 ? seconds_16dot16 : /* fix underflow */ (monotime > 0);
}

MDBX_INTERNAL_FUNC bin128_t osal_bootid(void);
/*----------------------------------------------------------------------------*/
/* lck stuff */

/// \brief Initialization of synchronization primitives linked with MDBX_env
///   instance both in LCK-file and within the current process.
/// \param
///   global_uniqueness_flag = true - denotes that there are no other processes
///     working with DB and LCK-file. Thus the function MUST initialize
///     shared synchronization objects in memory-mapped LCK-file.
///   global_uniqueness_flag = false - denotes that at least one process is
///     already working with DB and LCK-file, including the case when DB
///     has already been opened in the current process. Thus the function
///     MUST NOT initialize shared synchronization objects in memory-mapped
///     LCK-file that are already in use.
/// \return Error code or zero on success.
MDBX_INTERNAL_FUNC int osal_lck_init(MDBX_env *env,
                                     MDBX_env *inprocess_neighbor,
                                     int global_uniqueness_flag);

/// \brief Disconnects from shared interprocess objects and destructs
///   synchronization objects linked with MDBX_env instance
///   within the current process.
/// \param
///   inprocess_neighbor = NULL - if the current process does not have other
///     instances of MDBX_env linked with the DB being closed.
///     Thus the function MUST check for other processes working with DB or
///     LCK-file, and keep or destroy shared synchronization objects in
///     memory-mapped LCK-file depending on the result.
///   inprocess_neighbor = not-NULL - pointer to another instance of MDBX_env
///     (anyone of there is several) working with DB or LCK-file within the
///     current process. Thus the function MUST NOT try to acquire exclusive
///     lock and/or try to destruct shared synchronization objects linked with
///     DB or LCK-file. Moreover, the implementation MUST ensure correct work
///     of other instances of MDBX_env within the current process, e.g.
///     restore POSIX-fcntl locks after the closing of file descriptors.
/// \return Error code (MDBX_PANIC) or zero on success.
MDBX_INTERNAL_FUNC int osal_lck_destroy(MDBX_env *env,
                                        MDBX_env *inprocess_neighbor);

/// \brief Connects to shared interprocess locking objects and tries to acquire
///   the maximum lock level (shared if exclusive is not available)
///   Depending on implementation or/and platform (Windows) this function may
///   acquire the non-OS super-level lock (e.g. for shared synchronization
///   objects initialization), which will be downgraded to OS-exclusive or
///   shared via explicit calling of osal_lck_downgrade().
/// \return
///   MDBX_RESULT_TRUE (-1) - if an exclusive lock was acquired and thus
///     the current process is the first and only after the last use of DB.
///   MDBX_RESULT_FALSE (0) - if a shared lock was acquired and thus
///     DB has already been opened and now is used by other processes.
///   Otherwise (not 0 and not -1) - error code.
MDBX_INTERNAL_FUNC int osal_lck_seize(MDBX_env *env);

/// \brief Downgrades the level of initially acquired lock to
///   operational level specified by argument. The reason for such downgrade:
///    - unblocking of other processes that are waiting for access, i.e.
///      if (env->me_flags & MDBX_EXCLUSIVE) != 0, then other processes
///      should be made aware that access is unavailable rather than
///      wait for it.
///    - freeing locks that interfere file operation (especially for Windows)
///   (env->me_flags & MDBX_EXCLUSIVE) == 0 - downgrade to shared lock.
///   (env->me_flags & MDBX_EXCLUSIVE) != 0 - downgrade to exclusive
///   operational lock.
/// \return Error code or zero on success
MDBX_INTERNAL_FUNC int osal_lck_downgrade(MDBX_env *env);

/// \brief Locks LCK-file or/and table of readers for (de)registering.
/// \return Error code or zero on success
MDBX_INTERNAL_FUNC int osal_rdt_lock(MDBX_env *env);

/// \brief Unlocks LCK-file or/and table of readers after (de)registering.
MDBX_INTERNAL_FUNC void osal_rdt_unlock(MDBX_env *env);

/// \brief Acquires lock for DB change (on writing transaction start)
///   Reading transactions will not be blocked.
///   Declared as LIBMDBX_API because it is used in mdbx_chk.
/// \return Error code or zero on success
LIBMDBX_API int mdbx_txn_lock(MDBX_env *env, bool dont_wait);

/// \brief Releases lock once DB changes is made (after writing transaction
///   has finished).
///   Declared as LIBMDBX_API because it is used in mdbx_chk.
LIBMDBX_API void mdbx_txn_unlock(MDBX_env *env);

/// \brief Sets alive-flag of reader presence (indicative lock) for PID of
///   the current process. The function does no more than needed for
///   the correct working of osal_rpid_check() in other processes.
/// \return Error code or zero on success
MDBX_INTERNAL_FUNC int osal_rpid_set(MDBX_env *env);

/// \brief Resets alive-flag of reader presence (indicative lock)
///   for PID of the current process. The function does no more than needed
///   for the correct working of osal_rpid_check() in other processes.
/// \return Error code or zero on success
MDBX_INTERNAL_FUNC int osal_rpid_clear(MDBX_env *env);

/// \brief Checks for reading process status with the given pid with help of
///   alive-flag of presence (indicative lock) or using another way.
/// \return
///   MDBX_RESULT_TRUE (-1) - if the reader process with the given PID is alive
///     and working with DB (indicative lock is present).
///   MDBX_RESULT_FALSE (0) - if the reader process with the given PID is absent
///     or not working with DB (indicative lock is not present).
///   Otherwise (not 0 and not -1) - error code.
MDBX_INTERNAL_FUNC int osal_rpid_check(MDBX_env *env, uint32_t pid);

#if defined(_WIN32) || defined(_WIN64)

MDBX_INTERNAL_FUNC size_t osal_mb2w(wchar_t *dst, size_t dst_n, const char *src,
                                    size_t src_n);

#define OSAL_MB2WIDE(FROM, TO)                                                 \
  do {                                                                         \
    const char *const from_tmp = (FROM);                                       \
    const size_t from_mblen = strlen(from_tmp);                                \
    const size_t to_wlen = osal_mb2w(nullptr, 0, from_tmp, from_mblen);        \
    if (to_wlen < 1 || to_wlen > /* MAX_PATH */ INT16_MAX)                     \
      return ERROR_INVALID_NAME;                                               \
    wchar_t *const to_tmp = _alloca((to_wlen + 1) * sizeof(wchar_t));          \
    if (to_wlen + 1 !=                                                         \
        osal_mb2w(to_tmp, to_wlen + 1, from_tmp, from_mblen + 1))              \
      return ERROR_INVALID_NAME;                                               \
    (TO) = to_tmp;                                                             \
  } while (0)

typedef void(WINAPI *osal_srwlock_t_function)(osal_srwlock_t *);
MDBX_INTERNAL_VAR osal_srwlock_t_function osal_srwlock_Init,
    osal_srwlock_AcquireShared, osal_srwlock_ReleaseShared,
    osal_srwlock_AcquireExclusive, osal_srwlock_ReleaseExclusive;

#if _WIN32_WINNT < 0x0600 /* prior to Windows Vista */
typedef enum _FILE_INFO_BY_HANDLE_CLASS {
  FileBasicInfo,
  FileStandardInfo,
  FileNameInfo,
  FileRenameInfo,
  FileDispositionInfo,
  FileAllocationInfo,
  FileEndOfFileInfo,
  FileStreamInfo,
  FileCompressionInfo,
  FileAttributeTagInfo,
  FileIdBothDirectoryInfo,
  FileIdBothDirectoryRestartInfo,
  FileIoPriorityHintInfo,
  FileRemoteProtocolInfo,
  MaximumFileInfoByHandleClass
} FILE_INFO_BY_HANDLE_CLASS,
    *PFILE_INFO_BY_HANDLE_CLASS;

typedef struct _FILE_END_OF_FILE_INFO {
  LARGE_INTEGER EndOfFile;
} FILE_END_OF_FILE_INFO, *PFILE_END_OF_FILE_INFO;

#define REMOTE_PROTOCOL_INFO_FLAG_LOOPBACK 0x00000001
#define REMOTE_PROTOCOL_INFO_FLAG_OFFLINE 0x00000002

typedef struct _FILE_REMOTE_PROTOCOL_INFO {
  USHORT StructureVersion;
  USHORT StructureSize;
  DWORD Protocol;
  USHORT ProtocolMajorVersion;
  USHORT ProtocolMinorVersion;
  USHORT ProtocolRevision;
  USHORT Reserved;
  DWORD Flags;
  struct {
    DWORD Reserved[8];
  } GenericReserved;
  struct {
    DWORD Reserved[16];
  } ProtocolSpecificReserved;
} FILE_REMOTE_PROTOCOL_INFO, *PFILE_REMOTE_PROTOCOL_INFO;

#endif /* _WIN32_WINNT < 0x0600 (prior to Windows Vista) */

typedef BOOL(WINAPI *MDBX_GetFileInformationByHandleEx)(
    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
MDBX_INTERNAL_VAR MDBX_GetFileInformationByHandleEx
    mdbx_GetFileInformationByHandleEx;

typedef BOOL(WINAPI *MDBX_GetVolumeInformationByHandleW)(
    _In_ HANDLE hFile, _Out_opt_ LPWSTR lpVolumeNameBuffer,
    _In_ DWORD nVolumeNameSize, _Out_opt_ LPDWORD lpVolumeSerialNumber,
    _Out_opt_ LPDWORD lpMaximumComponentLength,
    _Out_opt_ LPDWORD lpFileSystemFlags,
    _Out_opt_ LPWSTR lpFileSystemNameBuffer, _In_ DWORD nFileSystemNameSize);
MDBX_INTERNAL_VAR MDBX_GetVolumeInformationByHandleW
    mdbx_GetVolumeInformationByHandleW;

typedef DWORD(WINAPI *MDBX_GetFinalPathNameByHandleW)(_In_ HANDLE hFile,
                                                      _Out_ LPWSTR lpszFilePath,
                                                      _In_ DWORD cchFilePath,
                                                      _In_ DWORD dwFlags);
MDBX_INTERNAL_VAR MDBX_GetFinalPathNameByHandleW mdbx_GetFinalPathNameByHandleW;

typedef BOOL(WINAPI *MDBX_SetFileInformationByHandle)(
    _In_ HANDLE hFile, _In_ FILE_INFO_BY_HANDLE_CLASS FileInformationClass,
    _Out_ LPVOID lpFileInformation, _In_ DWORD dwBufferSize);
MDBX_INTERNAL_VAR MDBX_SetFileInformationByHandle
    mdbx_SetFileInformationByHandle;

typedef NTSTATUS(NTAPI *MDBX_NtFsControlFile)(
    IN HANDLE FileHandle, IN OUT HANDLE Event,
    IN OUT PVOID /* PIO_APC_ROUTINE */ ApcRoutine, IN OUT PVOID ApcContext,
    OUT PIO_STATUS_BLOCK IoStatusBlock, IN ULONG FsControlCode,
    IN OUT PVOID InputBuffer, IN ULONG InputBufferLength,
    OUT OPTIONAL PVOID OutputBuffer, IN ULONG OutputBufferLength);
MDBX_INTERNAL_VAR MDBX_NtFsControlFile mdbx_NtFsControlFile;

typedef uint64_t(WINAPI *MDBX_GetTickCount64)(void);
MDBX_INTERNAL_VAR MDBX_GetTickCount64 mdbx_GetTickCount64;

#if !defined(_WIN32_WINNT_WIN8) || _WIN32_WINNT < _WIN32_WINNT_WIN8
typedef struct _WIN32_MEMORY_RANGE_ENTRY {
  PVOID VirtualAddress;
  SIZE_T NumberOfBytes;
} WIN32_MEMORY_RANGE_ENTRY, *PWIN32_MEMORY_RANGE_ENTRY;
#endif /* Windows 8.x */

typedef BOOL(WINAPI *MDBX_PrefetchVirtualMemory)(
    HANDLE hProcess, ULONG_PTR NumberOfEntries,
    PWIN32_MEMORY_RANGE_ENTRY VirtualAddresses, ULONG Flags);
MDBX_INTERNAL_VAR MDBX_PrefetchVirtualMemory mdbx_PrefetchVirtualMemory;

typedef enum _SECTION_INHERIT { ViewShare = 1, ViewUnmap = 2 } SECTION_INHERIT;

typedef NTSTATUS(NTAPI *MDBX_NtExtendSection)(IN HANDLE SectionHandle,
                                              IN PLARGE_INTEGER NewSectionSize);
MDBX_INTERNAL_VAR MDBX_NtExtendSection mdbx_NtExtendSection;

static __inline bool mdbx_RunningUnderWine(void) {
  return !mdbx_NtExtendSection;
}

typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
                                           LPCSTR lpValue, DWORD dwFlags,
                                           LPDWORD pdwType, PVOID pvData,
                                           LPDWORD pcbData);
MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;

NTSYSAPI ULONG RtlRandomEx(PULONG Seed);

typedef BOOL(WINAPI *MDBX_SetFileIoOverlappedRange)(HANDLE FileHandle,
                                                    PUCHAR OverlappedRangeStart,
                                                    ULONG Length);
MDBX_INTERNAL_VAR MDBX_SetFileIoOverlappedRange mdbx_SetFileIoOverlappedRange;

#endif /* Windows */

#endif /* !__cplusplus */

/*----------------------------------------------------------------------------*/

MDBX_MAYBE_UNUSED MDBX_NOTHROW_PURE_FUNCTION static __always_inline uint64_t
osal_bswap64(uint64_t v) {
#if __GNUC_PREREQ(4, 4) || __CLANG_PREREQ(4, 0) ||                             \
    __has_builtin(__builtin_bswap64)
  return __builtin_bswap64(v);
#elif defined(_MSC_VER) && !defined(__clang__)
  return _byteswap_uint64(v);
#elif defined(__bswap_64)
  return __bswap_64(v);
#elif defined(bswap_64)
  return bswap_64(v);
#else
  return v << 56 | v >> 56 | ((v << 40) & UINT64_C(0x00ff000000000000)) |
         ((v << 24) & UINT64_C(0x0000ff0000000000)) |
         ((v << 8) & UINT64_C(0x000000ff00000000)) |
         ((v >> 8) & UINT64_C(0x00000000ff000000)) |
         ((v >> 24) & UINT64_C(0x0000000000ff0000)) |
         ((v >> 40) & UINT64_C(0x000000000000ff00));
#endif
}

MDBX_MAYBE_UNUSED MDBX_NOTHROW_PURE_FUNCTION static __always_inline uint32_t
osal_bswap32(uint32_t v) {
#if __GNUC_PREREQ(4, 4) || __CLANG_PREREQ(4, 0) ||                             \
    __has_builtin(__builtin_bswap32)
  return __builtin_bswap32(v);
#elif defined(_MSC_VER) && !defined(__clang__)
  return _byteswap_ulong(v);
#elif defined(__bswap_32)
  return __bswap_32(v);
#elif defined(bswap_32)
  return bswap_32(v);
#else
  return v << 24 | v >> 24 | ((v << 8) & UINT32_C(0x00ff0000)) |
         ((v >> 8) & UINT32_C(0x0000ff00));
#endif
}

/*----------------------------------------------------------------------------*/

#if defined(_MSC_VER) && _MSC_VER >= 1900
/* LY: MSVC 2015/2017/2019 has buggy/inconsistent PRIuPTR/PRIxPTR macros
 * for internal format-args checker. */
#undef PRIuPTR
#undef PRIiPTR
#undef PRIdPTR
#undef PRIxPTR
#define PRIuPTR "Iu"
#define PRIiPTR "Ii"
#define PRIdPTR "Id"
#define PRIxPTR "Ix"
#define PRIuSIZE "zu"
#define PRIiSIZE "zi"
#define PRIdSIZE "zd"
#define PRIxSIZE "zx"
#endif /* fix PRI*PTR for _MSC_VER */

#ifndef PRIuSIZE
#define PRIuSIZE PRIuPTR
#define PRIiSIZE PRIiPTR
#define PRIdSIZE PRIdPTR
#define PRIxSIZE PRIxPTR
#endif /* PRI*SIZE macros for MSVC */

#ifdef _MSC_VER
#pragma warning(pop)
#endif