// Finds the object base for an interior pointer. In the case of a
// pointer to the tail of an object and the head of another, it will
// return the former object (the one whose tail we point at). To
// get the base pointer for a pointer into the pre-header, you should
// add PreHeader.Size before calling this.
internal static UIntPtr Find(UIntPtr addr)
{
UIntPtr page = PageTable.Page(addr);
UIntPtr currAddr = InteriorPtrTable.First(page);
// 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 > addr)
{
// Back up to the previous object. Should be fast
// since First updated the InteriorPtrTable entries.
currAddr = Before(PageTable.PageAddr(page));
}
VTable.Assert(!BumpAllocator.IsUnusedSpace(currAddr),
"InteriorPtrTable.Find 0");
VTable.Assert(currAddr <= addr, "InteriorPtrTable.Find 1");
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 postAddr =
PageTable.PagePad(currAddr) + PreHeader.Size;
VTable.Assert(postAddr <= addr, "InteriorPtrTable.Find 2");
currAddr = postAddr;
}
else
{
VTable.Assert(currAddr <= addr, "InteriorPtrTable.Find 3");
UIntPtr size = ObjectSize(currAddr);
VTable.Assert(size >= UIntPtr.Zero,
"InteriorPtrTable.Find 4");
UIntPtr postAddr = currAddr + size;
if (postAddr > addr)
{
return(currAddr);
}
else
{
currAddr = postAddr;
}
}
}
}
private static UIntPtr FirstPinnedObjectAddr(UIntPtr startPage)
{
return(InteriorPtrTable.First(startPage));
}
private static void CleanPageTail(UIntPtr postPinnedAddr)
{
if (!PageTable.PageAligned(postPinnedAddr))
{
// If postPinnedAddr points to the first object on its page,
// then we are removing all objects (specifically the part
// of the object that the InteriorPtrTable tracks, the
// vtables) from the page, so we should clear the page's
// entry in the InteriorPtrTable.
UIntPtr page = PageTable.Page(postPinnedAddr);
UIntPtr firstObjPtr = InteriorPtrTable.First(page);
if (firstObjPtr > postPinnedAddr)
{
VTable.Assert
(firstObjPtr - PreHeader.Size >= postPinnedAddr,
"postPinnedAddr should not point to the "
+ "interior of an object (1)");
InteriorPtrTable.ClearFirst(page);
}
else if (!BumpAllocator.IsUnusedSpace(firstObjPtr))
{
UIntPtr firstObjSize =
InteriorPtrTable.ObjectSize(firstObjPtr);
VTable.Assert
(firstObjPtr + firstObjSize - PreHeader.Size
<= postPinnedAddr,
"postPinnedAddr should not point to the "
+ "interior of an object (2)");
}
UIntPtr byteCount = PageTable.PagePad(postPinnedAddr)
- postPinnedAddr;
Util.MemClear(postPinnedAddr, byteCount);
BumpAllocator.WriteUnusedMarker(postPinnedAddr);
if (GC.remsetType == RemSetType.Cards && byteCount > 0)
{
UIntPtr firstCard = CardTable.CardNo(postPinnedAddr);
UIntPtr lastCard =
CardTable.CardNo(postPinnedAddr + byteCount - 1);
if (!OffsetTable.NoObjectPtrToTheCard(firstCard))
{
UIntPtr offset = OffsetTable.GetOffset(firstCard);
UIntPtr objPtr =
CardTable.CardAddr(firstCard) + offset;
UIntPtr size = OffsetTable.ObjectSize(objPtr);
VTable.Assert
((objPtr + size - PreHeader.Size
<= postPinnedAddr) ||
(objPtr >= postPinnedAddr),
"Object should be totally "
+ "above or below postPinnedAddr");
if (objPtr >= postPinnedAddr)
{
OffsetTable.ClearCards(firstCard, firstCard);
}
}
OffsetTable.ClearCards(firstCard + 1, lastCard);
}
}
}
/*
* 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;
}
}
}
}
