Function array_bitmap_copy

src/backend/utils/adt/arrayfuncs.c:4855–4919

* Copy nitems null-bitmap bits from source to destination * * destbitmap: start of destination array's null bitmap (mustn't be NULL) * destoffset: 0-based linear element number of first dest element * srcbitmap: start of source array's null bitmap, or NULL if none * srcoffset: 0-based linear element number of first source element * nitems: number of bits to copy (>= 0) * * If srcbitmap is

 * to make it worth worrying too much.  For the moment, KISS.
 */
void
array_bitmap_copy(bits8 *destbitmap, int destoffset,
				  const bits8 *srcbitmap, int srcoffset,
				  int nitems)
{
	int			destbitmask,
				destbitval,
				srcbitmask,
				srcbitval;

	Assert(destbitmap);
	if (nitems <= 0)
		return;					/* don't risk fetch off end of memory */
	destbitmap += destoffset / 8;
	destbitmask = 1 << (destoffset % 8);
	destbitval = *destbitmap;
	if (srcbitmap)
	{
		srcbitmap += srcoffset / 8;
		srcbitmask = 1 << (srcoffset % 8);
		srcbitval = *srcbitmap;
		while (nitems-- > 0)
		{
			if (srcbitval & srcbitmask)
				destbitval |= destbitmask;
			else
				destbitval &= ~destbitmask;
			destbitmask <<= 1;
			if (destbitmask == 0x100 /* (1<<8) */)
			{
				*destbitmap++ = destbitval;
				destbitmask = 1;
				if (nitems > 0)
					destbitval = *destbitmap;
			}
			srcbitmask <<= 1;
			if (srcbitmask == 0x100 /* (1<<8) */)
			{
				srcbitmap++;
				srcbitmask = 1;
				if (nitems > 0)
					srcbitval = *srcbitmap;
			}
		}
		if (destbitmask != 1)
			*destbitmap = destbitval;
	}
	else
	{
		while (nitems-- > 0)
		{
			destbitval |= destbitmask;
			destbitmask <<= 1;
			if (destbitmask == 0x100 /* (1<<8) */)
			{
				*destbitmap++ = destbitval;
				destbitmask = 1;
				if (nitems > 0)