text: /*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
  │vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
  ╞══════════════════════════════════════════════════════════════════════════════╡
  │ Copyright 2020 Justine Alexandra Roberts Tunney                              │
  │                                                                              │
  │ Permission to use, copy, modify, and/or distribute this software for         │
  │ any purpose with or without fee is hereby granted, provided that the         │
  │ above copyright notice and this permission notice appear in all copies.      │
  │                                                                              │
  │ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
  │ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
  │ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
  │ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
  │ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
  │ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
  │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
  │ PERFORMANCE OF THIS SOFTWARE.                                                │
  ╚─────────────────────────────────────────────────────────────────────────────*/
  #include "libc/calls/syscall_support-nt.internal.h"
  #include "libc/macros.internal.h"
  #include "libc/nt/enum/offerpriority.h"
  #include "libc/nt/memory.h"
  #include "libc/nt/runtime.h"
  #include "libc/nt/struct/memoryrangeentry.h"
  #include "libc/sysv/consts/madv.h"
  #include "libc/sysv/errfuns.h"
  
  forceinline typeof(PrefetchVirtualMemory) *GetPrefetchVirtualMemory(void) {
    static bool once;
    static typeof(PrefetchVirtualMemory) *PrefetchVirtualMemory_;
    if (!once) {
      PrefetchVirtualMemory_ = /* win8.1+ */
          GetProcAddressModule("Kernel32.dll", "PrefetchVirtualMemory");
      once = true;
    }
    return PrefetchVirtualMemory_;
  }
  
  forceinline typeof(OfferVirtualMemory) *GetOfferVirtualMemory(void) {
    static bool once;
    static typeof(OfferVirtualMemory) *OfferVirtualMemory_;
    if (!once) {
      OfferVirtualMemory_ = /* win8.1+ */
          GetProcAddressModule("Kernel32.dll", "OfferVirtualMemory");
      once = true;
    }
    return OfferVirtualMemory_;
  }
  
  textwindows int sys_madvise_nt(void *addr, size_t length, int advice) {
    uint32_t rangecount;
    struct NtMemoryRangeEntry ranges[1];
    if (advice == MADV_WILLNEED || advice == MADV_SEQUENTIAL) {
      typeof(PrefetchVirtualMemory) *fn = GetPrefetchVirtualMemory();
      if (fn) {
        ranges[0].VirtualAddress = addr;
        ranges[0].NumberOfBytes = length;
        rangecount = ARRAYLEN(ranges);
        if (fn(GetCurrentProcess(), &rangecount, ranges, 0)) {
          return 0;
        } else {
          return __winerr();
        }
      } else {
        return enosys();
      }
    } else if (advice == MADV_FREE) {
      typeof(OfferVirtualMemory) *fn = GetOfferVirtualMemory();
      if (fn) {
        if (fn(addr, length, kNtVmOfferPriorityNormal)) {
          return 0;
        } else {
          return __winerr();
        }
      } else {
        return enosys();
      }
    } else {
      return einval();
    }
  }
  