dlls/shlwapi/istream.c

   1 /*
   2  * SHLWAPI IStream functions
   3  *
   4  * Copyright 2002 Jon Griffiths
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  19  */
  20 #include <stdarg.h>
  21 #include <string.h>
  22
  23 #define COBJMACROS
  24 #include "windef.h"
  25 #include "winbase.h"
  26 #include "winerror.h"
  27 #include "winnls.h"
  28 #define NO_SHLWAPI_REG
  29 #define NO_SHLWAPI_PATH
  30 #include "shlwapi.h"
  31 #include "wine/debug.h"
  32
  33 WINE_DEFAULT_DEBUG_CHANNEL(shell);
  34
  35 /*************************************************************************
  36  * @       [SHLWAPI.166]
  37  *
  38  * Determine if a stream has 0 length.
  39  *
  40  * PARAMS
  41  *  lpStream [I] IStream object
  42  *
  43  * RETURNS
  44  *  TRUE:  If the stream has 0 length
  45  *  FALSE: Otherwise.
  46  */
  47 BOOL WINAPI SHIsEmptyStream(IStream *lpStream)
  48 {
  49   STATSTG statstg;
  50   BOOL bRet = TRUE;
  51
  52   TRACE("(%p)\n", lpStream);
  53
  54   memset(&statstg, 0, sizeof(statstg));
  55
  56   if(SUCCEEDED(IStream_Stat(lpStream, &statstg, 1)))
  57   {
  58     if(statstg.cbSize.QuadPart)
  59       bRet = FALSE; /* Non-Zero */
  60   }
  61   else
  62   {
  63     DWORD dummy, read_len;
  64
  65     /* Try to read from the stream */
  66     if (SUCCEEDED(IStream_Read(lpStream, &dummy, sizeof(dummy), &read_len)) && read_len == sizeof(dummy))
  67     {
  68       LARGE_INTEGER zero;
  69       zero.QuadPart = 0;
  70
  71       IStream_Seek(lpStream, zero, 0, NULL);
  72       bRet = FALSE; /* Non-Zero */
  73     }
  74   }
  75   return bRet;
  76 }