private static List <T> ProcessStream <T>(MemoryStream stream, FuncSpanT <T> parser)
{
var reader = PipeReader.Create(stream);
var records = new List <T>();
while (true)
{
ReadResult read = reader.ReadAsync().Result;
ReadOnlySequence <byte> buffer = read.Buffer;
while (TryReadLine(ref buffer, out ReadOnlySequence <byte> sequence))
{
var item = ProcessSequence(sequence, parser);
records.Add(item);
}
reader.AdvanceTo(buffer.Start, buffer.End);
if (read.IsCompleted)
{
break;
}
}
return(records);
}
public static async IAsyncEnumerable <T> ProcessFile <T>(Stream stream, FuncSpanT <T> parser)
{
PipeReader reader = PipeReader.Create(stream);
var i = 0;
while (true)
{
ReadResult read = await reader.ReadAsync();
ReadOnlySequence <byte> buffer = read.Buffer;
ReadOnlySequence <byte> sequence;
// read header row.
TryReadLine(ref buffer, out sequence);
while (TryReadLine(ref buffer, out sequence))
{
var item = ProcessSequence(sequence, parser);
yield return(item);
}
reader.AdvanceTo(buffer.Start, buffer.End);
if (read.IsCompleted)
{
break;
}
}
}
private static T Parse <T>(ReadOnlySpan <byte> bytes, FuncSpanT <T> parser)
{
Span <char> chars = stackalloc char[bytes.Length];
Encoding.UTF8.GetChars(bytes, chars);
return(parser(chars));
}
private static T ProcessSequence <T>(ReadOnlySequence <byte> sequence, FuncSpanT <T> parser)
{
if (sequence.IsSingleSegment)
{
return(Parse(sequence.FirstSpan, parser));
}
var length = (int)sequence.Length;
Span <byte> span = stackalloc byte[length];
sequence.CopyTo(span);
return(Parse(span, parser));
}
private static T ProcessSequence <T>(ReadOnlySequence <byte> sequence, FuncSpanT <T> parser)
{
const int LengthLimit = 256;
if (sequence.IsSingleSegment)
{
return(Parse(sequence.FirstSpan, parser));
}
var length = (int)sequence.Length;
if (length > LengthLimit)
{
throw new ArgumentException($"Line has a length exceeding the limit: {length}");
}
Span <byte> span = stackalloc byte[(int)sequence.Length];
sequence.CopyTo(span);
return(Parse(span, parser));
}