writewindows_fix.nim

proc c_fputc(c: char, f: File): cint {.
  importc: "fputs", header: "<stdio.h>", tags: [WriteIOEffect].}


# ...  


when defined(windows):
  proc writeWindows(f: File; s: string; doRaise = false) =
    # Don't ask why but the 'printf' family of function is the only thing
    # that writes utf-8 strings reliably on Windows. At least on my Win 10
    # machine. We also enable `setConsoleOutputCP(65001)` now by default.
    # But we cannot call printf directly as the string might contain \0.
    # So we have to loop over all the sections separated by potential \0s.
    var i = c_fprintf(f, "%s", s)
    while i < s.len:
      if s[i] == '\0':
        let c = c_fputc('\0', f)
        if c != 0:
          if doRaise: raiseEIO("cannot write string to file")
          break
        inc i
      else:
        let w = c_fprintf(f, "%s", unsafeAddr s[i])
        if w <= 0:
          if doRaise: raiseEIO("cannot write string to file")
          break
        inc i, w