Cross-platform GMT offset code (was Re: Timezone)

[Paul Scandariato <paul_lists at intellisw dot com>]

on 12/30/2001 12:55 PM, Mike Bailey <mike at realsoftware dot com> wrote:

> I haven't tested on carbon yet (just added the carbonlib declare) and I'm
> not sure about Win32.  Hope this helps.

Here's the GMT offset function I use, which has been tested on Classic,
Carbon, and Win32. Watch out for e-mail text wrapping.

Function OffsetFromGMT() As Integer
   dim tResult as integer
   dim info as memoryBlock
   dim offset as integer
   
   #if targetMacOS then
   #if targetCarbon then
   Declare Sub ReadLocation Lib "CarbonLib" (info As Ptr)
   #else
   Declare Sub ReadLocation Lib "InterfaceLib" (info As Ptr)
Inline68k("205F203C000C00E4A051")
   #endif
   
   info = newMemoryBlock(12)
   ReadLocation info
   offset = info.Long(8)
   offset = BitwiseAnd(offset, &hFFFFFF)
   if offset > &h800000 then
      offset = offset - &h1000000
   end if
   offset = offset \ 3600
   return offset
   #endif
   
   #if targetWin32 then
   
   Declare Function GetTimeZoneInformation Lib "kernel32.dll" (TimeZoneInfo
as Ptr) as integer
   
   info = newMemoryBlock(172)
   tResult = GetTimeZoneInformation(info)
   offset = -info.long(0)\60
   return offset
   
   #endif
   
End Function

- Paul

-- 
Paul Scandariato
Intelli Innovations, Inc.
Phone: (919) 468-0340
E-mail: paul at intellisw dot com
http://www.intellisw.com/

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