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200 lines
8.0 KiB
200 lines
8.0 KiB
; HGROUP.INC
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;
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; WARNING: This file contains structures used by both 16-bit and 32-bit code.
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; Make sure the structures align the same in both!
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;
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; These structures support *handle groups*. Handle groups are global
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; memory blocks that are ganged together so than when one gets freed,
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; all get freed automatically. This solves the problems of cleanup when
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; a Win32 thunk has to copy a shared block (for say DDE or clipboard)
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; to repack a structure or move data into a shared heap. Figuring out
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; when to free these intermediate copies is a nightmare (especially for DDE).
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; Since the copy and the original are one "virtual block", a better solution
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; is to put them in a handle group. Then all copies get cleaned
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; up automatically.
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;
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; A "global block" is either a Win16 global memory block or a native
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; Win32 global memory block. Blocks of different types can and do mix in the
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; same group. Groups are disjoint.
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;
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; No attempt is made to keep the blocks in a group consistent. Win32
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; apps cannot assume that DDE blocks represent shared memory. These blocks
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; are used for short term, one way, read-only data transfer.
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;
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; If any member of a group is freed by an app (or dll), the memory
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; managers nuke the entire group and free all of its members (due
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; to implementation reasons, Win32 handles may not be freed till
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; later. However, the group itself will disappear.)
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;
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; A block can also defect from a group. Blocks defect if they're cleaned
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; up as a result of process termination. Since such a cleanup is probably
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; unintentional and an abornal event, we prefer the memory leak to
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; causing other apps to crash. Defections don't affect any other member
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; of the group.
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;
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;
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;
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; For example, suppose a 32-bit DDE server posts a WM_DDE_DATA message.
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; The DDE thunk gets a native Win32 handle that can't be used out of context.
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;
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; The DDE thunk gamely creates a Win16 copy of the block, creates a
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; new group and puts the copy and original in the group. Then it sends
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; the Win16 copy to the client. Both blocks (and the group) will get
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; cleaned up when either the server or the client frees his block. Neither
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; the thunk nor the group manager cares which way it happens.
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;
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; The DDE thunk can also do this to repack a structure. It can make
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; a repacked copy and gang it to the original. All group members act
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; as a single "virtual handle" which is what an app would expect to see
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; in Win3.1.
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;
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;-------------------------------------------------------------------------
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; This structure contains the global variables (in K16) used by the group
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; manager. These globals are locked in linear memory since they're used
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; by K32 as well. They're packaged in a structure to simplify commmunication
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; between the two kernels.
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;
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; Access to this structure is synchronized by Win16Lock.
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;
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;
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; hg_wSelHeap:
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; Contains the *selector* of a movable Win16 global block which is an
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; array of HG_NODE structs. Every element is on exactly one of three
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; linked lists: the handle list, the death list and the free list.
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;
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; Initial value: 0. Lazily initialized.
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;
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; hg_wHndList:
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; 16-bit offset into wSelHeap of the first node in the handle list (-1
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; if empty). Each node represents a Win32 or Win16 handle that is part
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; of some existing group. The list is not sorted in any way.
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;
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; For implementation reasons, NULL handles can appear on this list for
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; short times (*)
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;
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; Initial value: -1.
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;
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;
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; hg_wDeathList:
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; 16-bit offset into wSelHeap of the first node in the death list (-1
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; if empty). Each node represents a Win32 handle who is logically
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; dead becaues their groups got nuked. The Win32 heap manager walks this
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; list periodically and frees the handles. To keep innocent apps from
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; paying a performance penalty, we set the TDBF_HGCLEANUP flag in
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; the hTask iff the death list contains any handles with that hTask.
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;
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; DeathList handles do not have group id's. Their group has already gone.
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;
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; Initial value: -1.
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;
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; hg_wFreeList:
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; 16-bit offset into wSelHeap of the first node in the free list (-1
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; if empty). Basically, all nodes that aren't being used for some other
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; purpose.
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;
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;
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; hg_wDontTouch:
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; normally 0. Set to 1 by certain routines to tell GlobalFree
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; not to examine or modify the HG database. Used to prevent
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; unwanted recursion when destroying groups. This flag is always set
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; and reset within a single Win16 lock session.
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;
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;
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; hg_wDeadGroup:
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; used for communication between free_object and GlobalFree. free_object
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; sets this global to the hgroup of the dying handle (unless
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; hg_wDontTouch is set.) GlobalFree uses this to nuke the group
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; and all its other members.
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;
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;
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; (*) Why do NULL handles appear in the handle list? Because nodes need to
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; defect from their group when they get freed since we can't have
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; invalid handles in the database. But we can't always unlink the node
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; at that time since it may be a group leader. So we null out its
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; handle but leave the node intact to serve as a group leader.
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;
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; GrowHGHeap runs a garbage collector that goes and cleans up
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; old groups that have no real handles left (BUGBUG: Not yet.)
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;
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;
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; MAINTENANCE WARNING: If you change this structure, you have to build
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; both k16 and k32 again. Also, you must ensure that all fields align
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; identically in both 32-bit and 16-bit code.
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;
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; THIS STRUCTURE IS PROTECTED BY THE crstGHeap16Lock, *not* the
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; Win16Mutex! Beware!
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;
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;------------------------------------------------------------------------
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HG_GLOBALS STRUCT
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hg_wSelHeap dw 0
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hg_wHndList dw -1 ;Offset into wSelHeap
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hg_wDeathList dw -1 ;Offset into wSelHeap
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hg_wFreeList dw -1 ;Offset into wSelHeap
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hg_wSlotCnt dw 0 ;# of HG_NODE slots in hg_wSelHeap
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hg_wDontTouch dw 0 ;Special use: see above
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hg_wDeadGroup dw -1 ;Special use: see above
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HG_GLOBALS ENDS
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;------------------------------------------------------------------------
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; This structure represents nodes in the group manager's database.
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; Each node lives on one of three linked lists: the handle list, the
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; death list, and the free list.
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;
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; hgn_wNext: Next node in list (as 16-bit offset into hg_wSelHeap).
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;
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; hgn_wGroup: Handle-list nodes only: the group id. The group id
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; is the address (16-bit offset into hg_wSelHeap) of
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; a designated group member (called the group leader).
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; All members of a group must use the same group leader.
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;
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; hgn_hTask16: Win32 handle-list and death-list nodes only: the
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; hTask of the Win32 process that created the handle.
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; Set to 0 for Win16 handles.
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; Native handles are private to each process so they can
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; be disambiguated only by using hTask16.
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;
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; hgn_wChkMk: Private field used by CheckHGHeap.
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;
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; hgn_dwHnd: Handle-list and death-list nodes only: the heap handle
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; (either Win32, or a zero-extended Win16 handle).
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; Death-list nodes can only contain native handles here.
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;
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; hgn_Flags: Flag bits
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;
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;
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; MAINTENANCE WARNING: If you change this structure, you have to build
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; both k16 and k32 again. Also, you must ensure that all fields align
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; identically in both 32-bit and 16-bit code. You must also change
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; SCALE_BY_SIZEOF_HGNODE to reflect any size changes.
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;
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; THIS STRUCTURE IS PROTECTED BY THE crstGHeap16Lock, *not* the
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; Win16Mutex! Beware!
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;
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;
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;------------------------------------------------------------------------
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HG_NODE STRUCT
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hgn_wNext dw 0 ;Next HG_NODE (offset into wSelHeap)
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hgn_wGroup dw 0 ;Group leader (offset into wSelHeap)
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hgn_hTask16 dw 0 ;Context of native Win32 handle
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hgn_wChkMk dw 0 ;For CheckHGHeap's private use.
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hgn_dwHnd dd 0 ;Win32 handle or 0-extended Win16 handle
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hgn_Flags dd 0 ;Padding
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HG_NODE ENDS
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HGF_CANONICAL equ 00000001h ;This handle is a canonical DDE_EXECUTE handle
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HGF_BLOWITAWAY equ 00000002h ;Used by HGGarbageCollect
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SCALE_BY_SIZEOF_HGNODE macro reg
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shl reg,4
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endm
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