src/port/win32common.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * win32common.c
   4  *        Common routines shared among the win32*.c ports.
   5  *
   6  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/port/win32common.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #ifdef FRONTEND
  17 #include "postgres_fe.h"
  18 #else
  19 #include "postgres.h"
  20 #endif
  21
  22 /*
  23  * pgwin32_get_file_type
  24  *
  25  * Convenience wrapper for GetFileType() with specific error handling for all the
  26  * port implementations.  Returns the file type associated with a HANDLE.
  27  *
  28  * On error, sets errno with FILE_TYPE_UNKNOWN as file type.
  29  */
  30 DWORD
  31 pgwin32_get_file_type(HANDLE hFile)
  32 {
  33         DWORD           fileType = FILE_TYPE_UNKNOWN;
  34         DWORD           lastError;
  35
  36         errno = 0;
  37
  38         /*
  39          * When stdin, stdout, and stderr aren't associated with a stream the
  40          * special value -2 is returned:
  41          * https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/get-osfhandle
  42          */
  43         if (hFile == INVALID_HANDLE_VALUE || hFile == (HANDLE) -2)
  44         {
  45                 errno = EINVAL;
  46                 return FILE_TYPE_UNKNOWN;
  47         }
  48
  49         fileType = GetFileType(hFile);
  50         lastError = GetLastError();
  51
  52         /*
  53          * Invoke GetLastError in order to distinguish between a "valid" return of
  54          * FILE_TYPE_UNKNOWN and its return due to a calling error.  In case of
  55          * success, GetLastError() returns NO_ERROR.
  56          */
  57         if (fileType == FILE_TYPE_UNKNOWN && lastError != NO_ERROR)
  58         {
  59                 _dosmaperr(lastError);
  60                 return FILE_TYPE_UNKNOWN;
  61         }
  62
  63         return fileType;
  64 }