This call is used to initialize a segment or to reset a reallocated segment for suballocation.


DosSubSet (SegSelector, Flags, Size)


;SegSelector (SEL) - input : Target data segment selector. ;Flags (USHORT) - input : 0 = Increasing the size of a segment already initialized. 1 = Initializing a segment. ;Size (USHORT) - input : Segment size in bytes.

Return Code

rc (USHORT) - return Return code descriptions are: * 0 NO_ERROR * 310 ERROR_DOSSUB_SHRINK * 313 ERROR_DOSSUB_BADSIZE * 314 ERROR_DOSSUB_BADFLAG


To initialize a segment for suballocation, issue DosSubSet before issuing DosSubAlloc and set Flags = 1. The segment must have been allocated with DosAllocSeg or DosAllocShrSeg.

If a segment allocated by a DosAllocSeg call has already been set for suballocation, and a call to DosSubAlloc returns Error_DOSSUB_NOMEM, the segment's size can be increased by a call to DosReallocSeg. After reallocation, the segment must be reset by a DosSubSet. Failure to reset the segment after changing its size can yield unpredictable results.

The size parameter should be a multiple of four bytes, or it is rounded up to a multiple of four. Note in DosSubSet, a size parameter of 0 indicates the segment is 64KB, while in DosSubAlloc and DosSubFree, a size parameter of 0 is an error. Other than this special case of 0 meaning 64KB, the minimum size that can be set is 12 bytes.

Example Code

C Binding


USHORT rc = DosSubSet(SegSelector, Flags, Size);

SEL SegSelector; /* Segment selector */ USHORT Flags; /* Parameter flags */ USHORT Size; /* Size of a block */

USHORT rc; /* return code */ </PRE>

MASM Binding


PUSH WORD SegSelector ;Segment selector PUSH WORD Flags ;Parameter flags PUSH WORD Size ;Size of a segment CALL DosSubSet

Returns WORD </PRE>


en/docs/fapi/dossubset.txt · Last modified: 2020/12/04 14:02 by prokushev