/*
* Returns a pointer past the last object _that_fits_completely_ on
* the given page. Note that the "last" object on a page may
* actually start on a previous page.
*/
internal static UIntPtr Last(UIntPtr page)
{
UIntPtr currAddr = InteriorPtrTable.First(page);
UIntPtr endAddr = PageTable.PageAddr(page + 1);
// Look out for the unused space token: this page may not
// have been completely allocated: its "first" object might not
// be valid.
if (BumpAllocator.IsUnusedSpace(currAddr) || currAddr >= endAddr)
{
// Back up to the previous object. Should be fast
// since First updated the InteriorPtrTable entries.
currAddr = Before(PageTable.PageAddr(page));
}
// REVIEW this is very similar to Find(addr) below.
VTable.Assert(currAddr <= endAddr);
while (true)
{
// Watch out for alignment padding; advance the pointer if
// it points to a syncblock index rather than a vtable
// pointer. Note that we must do this before scrolling,
// since the page table value was set before we knew the
// required alignment.
if (Allocator.IsAlignment(currAddr))
{
currAddr += UIntPtr.Size;
}
else if (BumpAllocator.IsUnusedSpace(currAddr))
{
UIntPtr nextAddr =
PageTable.PagePad(currAddr) + PreHeader.Size;
if (nextAddr >= endAddr)
{
return(currAddr);
}
else
{
currAddr = nextAddr;
}
}
else
{
VTable.Assert(currAddr <= endAddr);
UIntPtr size = ObjectSize(currAddr);
UIntPtr postAddr = currAddr + size;
if (postAddr > endAddr)
{
if (postAddr - PreHeader.Size > endAddr)
{
// The object spills over onto the next page
return(currAddr);
}
else
{
// The object ended at or before the page boundary
return(postAddr);
}
}
else
{
currAddr = postAddr;
}
}
}
}