TBSpaceAllocator::Space *TBSpaceAllocator::GetSmallestAvailableSpace(int needed_w)
{
assert(needed_w > 0);
// Add free space covering all available space if empty.
if (!m_free_space_list.HasLinks() && IsAllAvailable())
{
if (Space *fs = new Space)
{
fs->x = 0;
fs->width = m_available_space;
m_free_space_list.AddLast(fs);
}
}
// Check for the smallest space where we fit
Space *best_fs = nullptr;
for (Space *fs = m_free_space_list.GetFirst(); fs; fs = fs->GetNext())
{
if (needed_w == fs->width)
return fs; // It can't be better than a perfect match!
if (needed_w < fs->width)
if (!best_fs || fs->width < best_fs->width)
best_fs = fs;
}
return best_fs;
}
bool TBSpaceAllocator::HasSpace(int needed_w) const
{
if (needed_w > m_available_space)
return false;
if (IsAllAvailable())
return true;
for (Space *fs = m_free_space_list.GetFirst(); fs; fs = fs->GetNext())
{
if (needed_w <= fs->width)
return true;
}
return false;
}
void TBSpaceAllocator::FreeSpace(Space *space)
{
m_used_space_list.Remove(space);
m_available_space += space->width;
// Find where in m_free_space_list we should insert the space,
// or which existing space we can extend.
Space *preceeding = nullptr;
Space *succeeding = nullptr;
for (Space *fs = m_free_space_list.GetFirst(); fs; fs = fs->GetNext())
{
if (fs->x < space->x)
preceeding = fs;
if (fs->x > space->x)
{
succeeding = fs;
break;
}
}
if (preceeding && preceeding->x + preceeding->width == space->x)
{
preceeding->width += space->width;
delete space;
}
else if (succeeding && succeeding->x == space->x + space->width)
{
succeeding->x -= space->width;
succeeding->width += space->width;
delete space;
}
else
{
if (preceeding)
m_free_space_list.AddAfter(space, preceeding);
else if (succeeding)
m_free_space_list.AddBefore(space, succeeding);
else
{
assert(!m_free_space_list.HasLinks());
m_free_space_list.AddLast(space);
}
}
// Merge free spaces
Space *fs = m_free_space_list.GetFirst();
while (fs)
{
Space *next_fs = fs->GetNext();
if (!next_fs)
break;
if (fs->x + fs->width == next_fs->x)
{
fs->width += next_fs->width;
m_free_space_list.Delete(next_fs);
continue;
}
fs = next_fs;
}
#ifdef TB_RUNTIME_DEBUG_INFO
// Check that free space is in order
Space *tmp = m_free_space_list.GetFirst();
int x = 0;
while (tmp)
{
assert(tmp->x >= x);
x = tmp->x + tmp->width;
tmp = tmp->GetNext();
}
#endif // TB_RUNTIME_DEBUG_INFO
}