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need help for dllcall winapi FormatMessage

 
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hughman



Joined: 11 Feb 2007
Posts: 166
PostPosted: Wed Sep 09, 2009 1:45 pm    Post subject: need help for dllcall winapi FormatMessage Reply with quote
the definition of this function is
Code:

DWORD WINAPI FormatMessage(
  __in      DWORD dwFlags,
  __in_opt  LPCVOID lpSource,
  __in      DWORD dwMessageId,
  __in      DWORD dwLanguageId,
  __out     LPTSTR lpBuffer,
  __in      DWORD nSize,
  __in_opt  va_list *Arguments
);


My funtion
Code:

FormatMessageFromSystem(ErrorCode)
{
   VarSetCapacity(Buffer, 500)
   DllCall("FormatMessage"
      , "UInt", 0x1000      ; FORMAT_MESSAGE_FROM_SYSTEM
      , "Int", 0
      , "Int", ErrorCode
      , "Int", 0
      , "UInt", &Buffer
      , "UInt", 500
      , "Str", NULL)
   Return Buffer
}


but it always return null. How should I fix it?
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HotKeyIt



Joined: 18 Jun 2008
Posts: 4652
Location: AHK Forum
PostPosted: Wed Sep 09, 2009 6:50 pm    Post subject: Reply with quote
Check out this, can be always useful Wink WindowsDataTypes
This should work
Code:
MsgBox % FormatMessageFromSystem(0x1100)
FormatMessageFromSystem(ErrorCode)
{
   VarSetCapacity(Buffer, 2000)
   DllCall("FormatMessage"
      , "UInt", 0x1000      ; FORMAT_MESSAGE_FROM_SYSTEM
      , "UInt", 0
      , "UInt", ErrorCode
      , "UInt", 0x800 ;LANG_SYSTEM_DEFAULT (LANG_USER_DEFAULT=0x400)
      , "UInt", &Buffer
      , "UInt", 500
      , "UInt", 0)
   VarSetCapacity(buffer,-1)
   Return Buffer
}

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hughman



Joined: 11 Feb 2007
Posts: 166
PostPosted: Thu Sep 10, 2009 1:36 pm    Post subject: Reply with quote
Thanks very much.
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SKAN



Joined: 26 Dec 2005
Posts: 8688
PostPosted: Fri Sep 11, 2009 5:42 am    Post subject: Reply with quote
VarSetCapacity(buffer,-1) can be avoided:

EITHER

Code:
MsgBox % FormatMessageFromSystem(0x1100)
FormatMessageFromSystem(ErrorCode)
{
   VarSetCapacity(Buffer, 2000)
   DllCall("FormatMessage"
      , "UInt", 0x1000      ; FORMAT_MESSAGE_FROM_SYSTEM
      , "UInt", 0
      , "UInt", ErrorCode
      , "UInt", 0x800 ;LANG_SYSTEM_DEFAULT (LANG_USER_DEFAULT=0x400)
      , "Str", Buffer
      , "UInt", 500
      , "UInt", 0)
   Return Buffer
}


OR

Code:
MsgBox % FormatMessageFromSystem(0x1100)
FormatMessageFromSystem(ErrorCode)
{
   VarSetCapacity(Buffer, 2000, 32 )
   DllCall("FormatMessage"
      , "UInt", 0x1000      ; FORMAT_MESSAGE_FROM_SYSTEM
      , "UInt", 0
      , "UInt", ErrorCode
      , "UInt", 0x800 ;LANG_SYSTEM_DEFAULT (LANG_USER_DEFAULT=0x400)
      , "UInt", &Buffer
      , "UInt", 500
      , "UInt", 0)
   Return Buffer
}
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HotKeyIt



Joined: 18 Jun 2008
Posts: 4652
Location: AHK Forum
PostPosted: Fri Sep 11, 2009 6:51 am    Post subject: Reply with quote
Exclamation Thanks SKAN
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