private uint TakeBlocks(int blocksNeeded)
{
lock (_sync)
{
bool rescan = false;
bool resized = false;
int startingFrom = _prevFreeBlock;
int endingBefore = int.MaxValue;
while (true)
{
int found = 0;
int last = int.MinValue;
int first = int.MaxValue;
foreach (int free in _freeBlocks.EnumerateRange(startingFrom, endingBefore))
{
if (_reservedBlocks.Contains(free))
{
continue;
}
if (found == 0)
{
_prevFreeBlock = free;
if (!resized && rescan)
{
_firstFreeBlock = free;
}
}
first = Math.Min(first, free);
found = (last + 1 != free) ? 1 : found + 1;
last = free;
if (found == blocksNeeded)
{
int start = free - (blocksNeeded - 1);
for (int i = start; i <= free; i++)
{
_freeBlocks.Remove(i);
}
uint blockId = (uint)start;
blockId |= ((uint)Math.Min(16, blocksNeeded) - 1 << 28) & 0xF0000000u;
return(blockId);
}
}
if (resized)
{
throw new ArgumentOutOfRangeException("length");
}
if (!rescan && _firstFreeBlock < startingFrom)
{
rescan = true;
endingBefore = startingFrom + blocksNeeded - 1;
startingFrom = _firstFreeBlock;
}
else
{
resized = true;
startingFrom = AddSection();
endingBefore = int.MaxValue;
}
}
}
}
