RemoveBitPlanes
Synopsis
num = RemoveBitPlanes(bm, num)
D0 A0 D0C Prototype
ULONG RemoveBitPlanes(struct BitMap *bm, ULONG num);Description
Removes a specified number of bitplanes from a BitMap structure. The planes are physically removed from the BitMap structure, and the memory they occupied is freed. For each plane removed, the bm_Depth field of the BitMap is decremented, and the plane pointer is cleared.
Inputs
- bm — Address of an initialized BitMap structure.
- num — Number of bitplanes to remove. This can be equal to the total number of planes present in the BitMap, meaning all planes can be removed. The important thing is that
nummust be equal to or less than the value in thebm_Depthfield; otherwise, this function fails.
Result
- num — If NULL, no planes were removed, or the number of planes to remove was too high relative to the
bm_Depthfield. Otherwise, indicates the number of planes that were successfully removed.
Notes
This function currently does not use graphics.library/GetBitMapAttr() — it will be updated in future versions of the library.
See Also
- AddBitPlanes
graphics.library/FreeBitMap(),FreeRaster(),GetBitMapAttr()
Implementation
The original 68020 assembly implementation:
; (06-10-1994) --- num = RemoveBitPlanes(bm, num) (a0,d0)
_LVORemoveBitPlanes
movem.l d2-d4/a2-a6,-(sp)
moveq #0,d3
move.w d0,d4 ; num of raster...
subq.w #1,d4
sub.b bm_Depth(a0),d0
bpl.s FalExit
movem.w bm_BytesPerRow(a0),d2-d3
mulu.w d3,d2 ; D2 = amount of memory to free
lea bm_Depth(a0),a3 ; A3^Point to depth field
move.b (a3),d3
ext.w d3
lea bm_Planes(a0,d3.w*4),a2 ; Start to added bitplanes...
moveq #0,d3 ; bitplanes counter
suba.l a4,a4 ; Clear planeptr
move.l ab_ExecBase(a6),a6
RVB_LOP move.l -(a2),a1
subq.b #1,(a3)
move.l a4,(a2) ; Clear planeptr
move.l d2,d0
jsr _LVOFreeMem(a6)
addq.b #1,d3
dbf d4,RVB_LOP
RVBExit move.l d3,d0
movem.l (sp)+,d2-d4/a2-a6
rtsLast updated on