private unsafe long CalculateSize(IEventPayloads payloads)
{
// event count + crc
// foreach event: meta + payload
long size = sizeof(byte) + sizeof(uint);
foreach (var e in payloads)
{
size += sizeof(EventMeta);
size += e.Count;
}
return(size);
}
public unsafe Task <IEnumerable <EventMeta> > Write(IEventPayloads payload)
{
lock (_view) {
// early out if we are complete
if (_isComplete)
{
return(null);
}
// early out if we don't have enough space left in the log
var space = _view.Capacity - _position;
if (space < CalculateSize(payload))
{
return(null);
}
var events = new List <EventMeta>();
try {
byte *ptr = null;
_view.SafeMemoryMappedViewHandle.AcquirePointer(ref ptr);
var start = _position;
// write event count in the batch
*(ptr + _position) = (byte)payload.Count;
_position += sizeof(byte);
foreach (var e in payload)
{
// write event meta block
var meta = new EventMeta {
Created = DateTime.UtcNow,
Id = _start + _count
};
*(EventMeta *)(ptr + _position) = meta;
_position += sizeof(EventMeta);
// write event payload
*(ushort *)(ptr + _position) = (ushort)e.Count;
_position += sizeof(ushort);
Marshal.Copy(e.Array, e.Offset, (IntPtr)(ptr + _position), e.Count);
_position += e.Count;
// increment event count
_count++;
events.Add(meta);
}
// post-fix batch with crc
var length = (int)(_position - start);
var crcBuffer = GetBuffer(length);
Marshal.Copy((IntPtr)(ptr + start), crcBuffer, 0, length);
var crc = Crc32Algorithm.Compute(crcBuffer, 0, length);
*(uint *)(ptr + _position) = crc;
_position += sizeof(uint);
}
finally {
_view.SafeMemoryMappedViewHandle.ReleasePointer();
}
// store a handle to the task - to be completed when the buffer is flushed
var tcs = new TaskCompletionSource <IEnumerable <EventMeta> >();
_awaiting.Add(() => tcs.SetResult(events));
return(tcs.Task);
}
}
public Task <IEnumerable <EventMeta> > Store(IEventPayloads payload) => throw new NotImplementedException();
