/* free_block -- free a block, merging it with its neighbours */
static header *free_block(header *h, bool mapped) {
/* Mapped is true if this memory is being recycled: it's already
in the page table, but we'll need to zero it. */
header *prev = left_neighbour(h), *next = right_neighbour(h);
/* Base and size of area where page table needs updating */
uchar *pg_memory = h->h_memory;
unsigned pg_size = (mapped ? 0 : h->h_size);
#ifdef TRACE
if (debug['l']) {
printf("Freeing block at %p, size %#x\n",
h->h_memory, h->h_size);
if (prev == NULL) printf("prev=null, ");
else printf("prev=%p, ", prev->h_memory);
if (next == NULL) printf("next=null\n");
else printf("next=%p\n", next->h_memory);
}
#endif
if (mapped) memset(h->h_memory, 0, h->h_size);
if (prev != NULL && prev->h_objsize == 0) {
DEBUG_PRINT('l', ("Merging with prev\n"));
unlink(prev);
prev->h_size += h->h_size;
pg_memory = h->h_memory;
pg_size = h->h_size;
free_header(h);
h = prev;
}
if (next != NULL && next->h_objsize == 0) {
DEBUG_PRINT('l', ("Merging with next\n"));
unlink(next);
next->h_memory = h->h_memory;
next->h_size += h->h_size;
pg_memory = h->h_memory;
pg_size = h->h_size;
free_header(h);
h = next;
}
if (pg_size > 0) page_setup(pg_memory, pg_size, h);
make_free(h);
/* Return the merged block */
return h;
}
bool LOSfinder::bresen_y(PosPoint source, PosPoint target)
{
int x = source.posx;
int error = 0;
int delta_y = std::abs(source.posy - target.posy);
int deltaerr = std::abs(source.posx - target.posx);
int deltastep = sign(target.posx - source.posx);
int incrstep = sign(target.posy - source.posy);
for (int y = source.posy; y != target.posy; y += incrstep)
{
if ((x % RAY_MULTIPLIER) == 0 && (y % RAY_MULTIPLIER) == 0)
{
// when in corner check side neighbours
// if both of them are not transparent then corner is not transparent
PosPoint left_neighbour(x + deltastep, y, source.posz);
PosPoint right_neighbour(x, y + incrstep, source.posz);
if (!is_transparent(left_neighbour) && !is_transparent(right_neighbour))
{
return false;
}
}
else if (x % RAY_MULTIPLIER == 0)
{
// when ray hits an edge check both tiles. Since ray travels through edge both of them
// must be transparent
PosPoint left_neighbour(x - deltastep, y, source.posz);
PosPoint right_neighbour(x + deltastep, y, source.posz);
if (!is_transparent(left_neighbour) || !is_transparent(right_neighbour))
{
return false;
}
}
else if (y % RAY_MULTIPLIER == 0)
{
// second case of edge handling
PosPoint left_neighbour(x, y - incrstep, source.posz);
PosPoint right_neighbour(x, y + incrstep, source.posz);
if (!is_transparent(left_neighbour) || !is_transparent(right_neighbour))
{
return false;
}
}
else
{
PosPoint new_point(x, y, source.posz);
if (!is_transparent(new_point))
{
return false;
}
}
error += deltaerr;
if (error >= delta_y)
{
x += deltastep;
error -= delta_y;
}
}
return true;
}