public Chunk(ChunkReader reader, long pos, ChunkHeader header)
{
_reader = reader;
_header = header;
BeginPosition = pos;
}
async Task <Meter?> ReadMeter(long pos)
{
Debug.Assert(pos >= 0 && pos % MeterInterval == 0);
if (pos == 0)
{
return new Meter()
{
ChunkBeginPosition = 0
}
}
;
_reader.Seek(pos);
if (await _reader.ReadAsync(_meter, 0, _meter.Length) != _meter.Length)
{
return(null);
}
var res = new Meter();
if (!res.ReadFrom(_meter))
{
return(null);
}
if (res.ChunkBeginPosition > pos)
{
return(null);
}
return(res);
}
async Task <ChunkHeader?> ReadChunkHeader(long pos)
{
if (!await ReadMetered(pos, _header, 0, _header.Length))
{
return(null);
}
var res = new ChunkHeader();
if (!res.ReadFrom(_header))
{
return(null);
}
if (!res.EndPosition(pos).HasValue)
{
return(null);
}
return(res);
}
async Task <bool> ReadMetered(long pos, byte[] array, int offset, int count)
{
Debug.Assert(array != null);
Debug.Assert(offset >= 0);
Debug.Assert(array.Length - offset >= count);
if (!(MeteredPosition(pos, count) <= Length))
{
return(false);
}
while (count > 0)
{
Debug.Assert(IsValidPosition(pos));
if (pos % MeterInterval == 0)
{
pos += Meter.Size;
}
_reader.Seek(pos);
int n = Math.Min(count, MeterInterval - (int)(pos % MeterInterval));
if (await _reader.ReadAsync(array, offset, n) != n)
{
return(false);
}
pos += n;
offset += n;
count -= n;
}
return(true);
}