public static void Setup()
{
BitMapIndexTable = new BitMapIndexTable(BootPageAllocator.AllocatePage());
var maximumMemoryAddress = BootMemoryMap.GetMaximumAddress();
TotalPages = (uint)(maximumMemoryAddress.ToInt64() / Page.Size);
var bitMapCount = TotalPages / (Page.Size * 8);
for (uint i = 0; i < bitMapCount; i++)
{
var bitmap = BootPageAllocator.AllocatePage();
Page.ClearPage(bitmap);
BitMapIndexTable.AddBitMapEntry(i, bitmap);
}
var entries = BootMemoryMap.GetBootMemoryMapEntryCount();
// pass 0 - mark available pages
for (uint i = 0; i < entries; i++)
{
var entry = BootMemoryMap.GetBootMemoryMapEntry(i);
if (!entry.IsAvailable)
{
continue;
}
var start = Alignment.AlignUp(entry.StartAddress.ToInt64(), Page.Size);
var end = Alignment.AlignDown(entry.EndAddress.ToInt64() + 1, Page.Size);
var pages = (uint)(end - start) / Page.Size;
if (pages <= 0)
{
continue;
}
var startPage = (uint)(start / Page.Shift);
var endPage = startPage + pages - 1;
MinimumAvailablePage = Math.Min(MinimumAvailablePage, startPage);
MaximumAvailablePage = Math.Max(MaximumAvailablePage, endPage);
SetPageBitMapEntry(startPage, pages, entry.IsAvailable);
}
// pass 1 - unmark reserved pages
for (uint i = 0; i < entries; i++)
{
var entry = BootMemoryMap.GetBootMemoryMapEntry(i);
if (entry.IsAvailable)
{
continue;
}
var start = Alignment.AlignUp(entry.StartAddress.ToInt64(), Page.Size);
var end = Alignment.AlignDown(entry.EndAddress.ToInt64() + 1, Page.Size);
var pages = (uint)(end - start) / Page.Size;
if (pages <= 0)
{
continue;
}
var startPage = (uint)(start / Page.Shift);
var endPage = startPage + pages - 1;
MinimumReservedPage = Math.Min(MinimumReservedPage, startPage);
MaximumReservedPage = Math.Max(MaximumReservedPage, endPage);
if (MinimumAvailablePage >= startPage && MinimumAvailablePage <= endPage)
{
MinimumAvailablePage = endPage + 1;
}
if (MaximumAvailablePage >= startPage && MaximumAvailablePage <= endPage)
{
MaximumAvailablePage = startPage - 1;
}
SetPageBitMapEntry(startPage, pages, entry.IsAvailable);
}
SearchNextStartPage = MinimumAvailablePage;
}