win32common.c

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/*-------------------------------------------------------------------------
 *
 * win32common.c
 *    Common routines shared among the win32*.c ports.
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/port/win32common.c
 *
 *-------------------------------------------------------------------------
 */
 
#ifdef FRONTEND
#include "postgres_fe.h"
#else
#include "postgres.h"
#endif
 
/*
 * pgwin32_get_file_type
 *
 * Convenience wrapper for GetFileType() with specific error handling for all the
 * port implementations.  Returns the file type associated with a HANDLE.
 *
 * On error, sets errno with FILE_TYPE_UNKNOWN as file type.
 */
DWORD
pgwin32_get_file_type(HANDLE hFile)
{
    DWORD       fileType = FILE_TYPE_UNKNOWN;
    DWORD       lastError;
 
    errno = 0;
 
    /*
     * When stdin, stdout, and stderr aren't associated with a stream the
     * special value -2 is returned:
     * https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/get-osfhandle
     */
    if (hFile == INVALID_HANDLE_VALUE || hFile == (HANDLE) -2)
    {
        errno = EINVAL;
        return FILE_TYPE_UNKNOWN;
    }
 
    fileType = GetFileType(hFile);
    lastError = GetLastError();
 
    /*
     * Invoke GetLastError in order to distinguish between a "valid" return of
     * FILE_TYPE_UNKNOWN and its return due to a calling error.  In case of
     * success, GetLastError() returns NO_ERROR.
     */
    if (fileType == FILE_TYPE_UNKNOWN && lastError != NO_ERROR)
    {
        _dosmaperr(lastError);
        return FILE_TYPE_UNKNOWN;
    }
 
    return fileType;
}