/// <summary>
/// Create a page with the size of an item and add it to the SMT at a certain page
/// </summary>
/// <param name="aItemSize">Object size in bytes</param>
/// <exception cref="Exception">Thrown if:
/// <list type="bullet">
/// <item>aItemSize is 0.</item>
/// <item>aItemSize is not word aligned.</item>
/// <item>SMT is not initialized.</item>
/// <item>The item size is bigger then a small heap size.</item>
/// </list>
/// </exception>
static void CreatePage(SMTPage *aPage, uint aItemSize)
{
var xPtr = (byte *)RAT.AllocPages(RAT.PageType.HeapSmall, 1);
if (xPtr == null)
{
return; // we failed to create the page, Alloc should still handle this case
}
uint xSlotSize = aItemSize + PrefixItemBytes;
uint xItemCount = RAT.PageSize / xSlotSize;
for (uint i = 0; i < xItemCount; i++)
{
byte * xSlotPtr = xPtr + i * xSlotSize;
ushort *xMetaDataPtr = (ushort *)xSlotPtr;
xMetaDataPtr[0] = 0; // Actual data size. 0 is empty.
xMetaDataPtr[1] = 0; // Ref count
}
//now add it to the smt
var parent = GetLastBlock(aPage, aItemSize);
var smtBlock = NextFreeBlock(aPage); //get the next free block in the smt
if (smtBlock == null) // we could not allocate a new block since the SMT table is all full
{
// we need to expand the SMT table by a page
var last = SMT;
while (last->Next != null)
{
last = last->Next;
}
last->Next = InitSMTPage();
parent = GetLastBlock(last->Next, aItemSize);
smtBlock = NextFreeBlock();
if (smtBlock == null)
{
Debugger.SendKernelPanic(0x93);
while (true)
{
}
;
}
}
if (parent != null)
{
// there is already a block for the same size on the same page
parent->NextBlock = smtBlock;
}
else
{
// in this case this is the first block of the size, so we can link it to root
var root = GetFirstBlock(aPage, aItemSize);
root->First = smtBlock;
}
smtBlock->SpacesLeft = xItemCount;
smtBlock->PagePtr = xPtr;
}
/// <summary>
/// Alloc memory block, of a given size.
/// </summary>
/// <param name="aSize">A size of block to alloc, in bytes.</param>
/// <returns>Byte pointer to the start of the block.</returns>
static public byte *Alloc(Native aSize)
{
Native xPages = (Native)((aSize + PrefixBytes) / RAT.PageSize) + 1;
var xPtr = (Native *)RAT.AllocPages(RAT.PageType.HeapLarge, xPages);
xPtr[0] = xPages * RAT.PageSize - PrefixBytes; // Allocated data size
xPtr[1] = aSize; // Actual data size
xPtr[2] = 0; // Ref count
xPtr[3] = 0; // Ptr to first
return((byte *)xPtr + PrefixBytes);
}
/// <summary>
/// Create a page with the size of an item.
/// </summary>
/// <param name="aItemSize">Item size.</param>
/// <exception cref="Exception">Thrown if:
/// <list type="bullet">
/// <item>aItemSize is 0.</item>
/// <item>aItemSize is not word aligned.</item>
/// <item>SMT is not initialized.</item>
/// <item>The item size is bigger then a small heap size.</item>
/// </list>
/// </exception>
static void CreatePage(Native aItemSize)
{
if (aItemSize == 0)
{
throw new Exception("aItemSize cannot be 0.");
}
else if (aItemSize % sizeof(Native) != 0)
{
throw new Exception("aItemSize must be word aligned.");
}
else if (mMaxItemSize == 0)
{
throw new Exception("SMT is not initialized.");
}
else if (aItemSize > mMaxItemSize)
{
throw new Exception("Cannot allocate more than MaxItemSize in SmallHeap.");
}
// Limit to one page so they are allocated low and easy to move around.
// In future may put some up top and be larger as well.
Native xPages = 1;
var xPtr = (Native *)RAT.AllocPages(RAT.PageType.HeapSmall, xPages);
// Ptr to next page of same size
xPtr[0] = 0;
//
// # of slots. Necessary for future use when more than one page, but used currently as well.
Native xSlotSize = aItemSize + PrefixItemBytes;
Native xItemCount = RAT.PageSize * xPages / xSlotSize;
xPtr[1] = xItemCount;
//
// # of free slots
xPtr[2] = xItemCount;
//
xPtr = xPtr + 3;
for (Native i = 0; i < xItemCount; i++)
{
byte * xSlotPtr = (byte *)xPtr + i * xSlotSize;
Native *xMetaDataPtr = (Native *)xSlotPtr;
xMetaDataPtr[0] = 0; // Actual data size. 0 is empty.
xMetaDataPtr[1] = 0; // Ref count
xMetaDataPtr[2] = 0; // Ptr to first
}
}
/// <summary>
/// Alloc memory block, of a given size.
/// </summary>
/// <param name="aSize">A size of block to alloc, in bytes.</param>
/// <returns>Byte pointer to the start of the block.</returns>
public static byte *Alloc(uint aSize, byte aType = RAT.PageType.HeapLarge)
{
uint xPages = ((aSize + PrefixBytes) / RAT.PageSize) + 1;
var xPtr = (uint *)RAT.AllocPages(aType, xPages);
if (xPtr == null)
{
Debugger.SendKernelPanic(0x67); // out of pages
while (true)
{
}
}
xPtr[0] = xPages * RAT.PageSize - PrefixBytes; // Allocated data size
xPtr[1] = aSize; // Actual data size
xPtr[3] = 0; // padding for now?,
xPtr[2] = 0; // padding + GC object status
return((byte *)xPtr + PrefixBytes);
}
/// <summary>
/// Allocates and initialise a page for the SMT table
/// </summary>
/// <returns></returns>
private static SMTPage *InitSMTPage()
{
var page = (SMTPage *)RAT.AllocPages(RAT.PageType.SMT, 1);
page->First = (RootSMTBlock *)(page + 1);
// TODO Change these sizes after further study and also when page size changes.
// SMT can be grown as needed. Also can adjust and create new ones dynamicaly as it runs.
// The current algorithm only works if we create the inital pages in increasing order
AddRootSMTBlock(page, 16);
AddRootSMTBlock(page, 24);
AddRootSMTBlock(page, 48);
AddRootSMTBlock(page, 64);
AddRootSMTBlock(page, 128);
AddRootSMTBlock(page, 256);
AddRootSMTBlock(page, 512);
AddRootSMTBlock(page, mMaxItemSize);
return(page);
}