internal SequencePosition Seek(SequencePosition start, SequencePosition end, long count, bool checkEndReachable = true)
{
int startIndex = start.Index;
int endIndex = end.Index;
SequenceType type = GetSequenceType();
startIndex = GetIndex(startIndex);
endIndex = GetIndex(endIndex);
switch (type)
{
case SequenceType.MemoryList:
if (start.Segment == end.Segment && endIndex - startIndex >= count)
{
// end.Index >= count + Index and end.Index is int
return(new SequencePosition(start.Segment, startIndex + (int)count));
}
return(SeekMultiSegment((IMemoryList <byte>)start.Segment, startIndex, (IMemoryList <byte>)end.Segment, endIndex, count, checkEndReachable));
case SequenceType.OwnedMemory:
case SequenceType.Array:
if (endIndex - startIndex >= count)
{
// end.Index >= count + Index and end.Index is int
return(new SequencePosition(start.Segment, startIndex + (int)count));
}
ThrowHelper.ThrowArgumentOutOfRangeException_CountOutOfRange();
return(default);
default:
ThrowHelper.ThrowInvalidOperationException_UnexpectedSegmentType();
return(default);
}
}
private static SequencePosition SeekMultiSegment(IMemoryList <byte> start, int startIndex, IMemoryList <byte> end, int endPosition, long count, bool checkEndReachable)
{
SequencePosition result = default;
bool foundResult = false;
IMemoryList <byte> current = start;
int currentIndex = startIndex;
while (current != null)
{
// We need to loop up until the end to make sure start and end are connected
// if end is not trusted
if (!foundResult)
{
var isEnd = current == end;
int currentEnd = isEnd ? endPosition : current.Memory.Length;
int currentLength = currentEnd - currentIndex;
// We would prefer to put position in the beginning of next segment
// then past the end of previous one, but only if we are not leaving current buffer
if (currentLength > count ||
(currentLength == count && isEnd))
{
result = new SequencePosition(current, currentIndex + (int)count);
foundResult = true;
if (!checkEndReachable)
{
break;
}
}
count -= currentLength;
}
if (current.Next == null && current != end)
{
ThrowHelper.ThrowInvalidOperationException_EndPositionNotReached();
}
current = current.Next;
currentIndex = 0;
}
if (!foundResult)
{
ThrowHelper.ThrowArgumentOutOfRangeException_CountOutOfRange();
}
return(result);
}
internal SequencePosition Seek(SequencePosition start, SequencePosition end, int count, bool checkEndReachable = true)
{
int startIndex = start.GetInteger();
int endIndex = end.GetInteger();
SequenceType type = GetSequenceType();
startIndex = GetIndex(startIndex);
endIndex = GetIndex(endIndex);
switch (type)
{
case SequenceType.MemoryList:
if (start.GetObject() == end.GetObject() && endIndex - startIndex >= count)
{
return(new SequencePosition(start.GetObject(), startIndex + count));
}
return(SeekMultiSegment((IMemoryList <byte>)start.GetObject(), startIndex, (IMemoryList <byte>)end.GetObject(), endIndex, count, checkEndReachable));
case SequenceType.OwnedMemory:
case SequenceType.Array:
if (start.GetObject() != end.GetObject())
{
ThrowHelper.ThrowInvalidOperationException_EndPositionNotReached();
}
if (endIndex - startIndex >= count)
{
return(new SequencePosition(start.GetObject(), startIndex + count));
}
ThrowHelper.ThrowArgumentOutOfRangeException_CountOutOfRange();
return(default);
default:
ThrowHelper.ThrowInvalidOperationException_UnexpectedSegmentType();
return(default);
}
}
