CreateFileMapping1.nim

#[
    Author: Ward

    Example of CreateFileMapping

    References:
      https://docs.microsoft.com/en-us/windows/win32/memory/creating-named-shared-memory
]#

# This program may need to run as admin.

import winim/lean
import strformat, terminal # for getch

const BUF_SIZE = 256

block:
  let hMapFile = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, 0,
    BUF_SIZE, "Global\\MyFileMappingObject")

  if hMapFile == 0:
    echo fmt"Could not create file mapping object ({GetLastError()})."
    quit()

  defer:
    CloseHandle(hMapFile)

  let pBuf = cast[LPSTR](MapViewOfFile(hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, BUF_SIZE))
  if pBuf.isNil:
    echo fmt"Could not map view of file ({GetLastError()})."
    quit()

  defer:
    UnmapViewOfFile(pBuf)

  # https://khchen.github.io/winim/winstr.html#%3C%3C.t%2CA%2CB
  # Fill operator for SomeBuffer and SomeString.
  # Please make sure both side have the same character size.
  # If destination don't have the length information (e.g. pointer or UncheckedArray),
  # please make sure the buffer size is large enough.
  pBuf << "Message from first process."

  discard getch()