我正在尝试将代码从dotnetty转换为system.io..io.pipelines。在dotnetty中,我正在利用Length FieldBasedeCoder解码TCP消息,其中前两个字节代表一个指示整个消息长度的整数。
我看到的所有演示都依赖基于字符串的EOL指标。我觉得这应该很容易,但是它逃脱了我如何抓住前两个字节,然后是x字节的数量,如长度前缀所示。
。以下是David Fowler的TCPecho服务器的一个示例。如果前两个字节指示消息大小,而不是指示Message结束的EOL字符?
,我该如何重写以解析消息? private static async Task ReadPipeAsync(Socket socket, PipeReader reader)
{
while (true)
{
ReadResult result = await reader.ReadAsync();
ReadOnlySequence<byte> buffer = result.Buffer;
SequencePosition? position = null;
do
{
// Find the EOL
position = buffer.PositionOf((byte)'n');
if (position != null)
{
var line = buffer.Slice(0, position.Value);
ProcessLine(socket, line);
// This is equivalent to position + 1
var next = buffer.GetPosition(1, position.Value);
// Skip what we've already processed including n
buffer = buffer.Slice(next);
}
}
while (position != null);
// We sliced the buffer until no more data could be processed
// Tell the PipeReader how much we consumed and how much we left to process
reader.AdvanceTo(buffer.Start, buffer.End);
if (result.IsCompleted)
{
break;
}
}
reader.Complete();
}
这就是我最终得到的:
private const int lengthPrefixSize = 2; // number of bytes in the length prefix
private static ushort ParseLengthPrefix(ReadOnlySpan<byte> buffer) => BinaryPrimitives.ReadUInt16LittleEndian(buffer);
private static ushort ParseLengthPrefix(in ReadOnlySequence<byte> buffer)
{
if (buffer.First.Length >= lengthPrefixSize)
return ParseLengthPrefix(buffer.First.Span.Slice(0, lengthPrefixSize));
Span<byte> lengthPrefixBytes = stackalloc byte[lengthPrefixSize];
buffer.Slice(0, lengthPrefixSize).CopyTo(lengthPrefixBytes);
return ParseLengthPrefix(lengthPrefixBytes);
}
private static async Task ReadPipeAsync(Socket socket, PipeReader reader)
{
ushort? lengthPrefix = null;
while (true)
{
ReadResult result = await reader.ReadAsync();
ReadOnlySequence<byte> buffer = result.Buffer;
while (true)
{
if (lengthPrefix == null)
{
// If we don't have enough for the length prefix, then wait for more data.
if (buffer.Length < lengthPrefixSize)
break;
// Read and parse the length prefix
lengthPrefix = ParseLengthPrefix(buffer);
buffer = buffer.Slice(lengthPrefixSize);
}
// If we haven't read the entire packet yet, then wait.
if (buffer.Length < lengthPrefix.Value)
break;
// Read the data packet
var line = buffer.Slice(0, lengthPrefix.Value);
ProcessLine(socket, line);
buffer = buffer.Slice(lengthPrefix.Value);
lengthPrefix = null;
}
// We sliced the buffer until no more data could be processed
// Tell the PipeReader how much we consumed and how much we left to process
reader.AdvanceTo(buffer.Start, buffer.End);
if (result.IsCompleted)
{
break;
}
}
reader.Complete();
}
此解决方案确实具有长度前缀缓冲区,但是仅当长度前缀跨越跨度时才使用。我认为有一个SequenceReader<T>
来了,尽管在长度前缀(很少的字节和没有缓冲区分配(的情况下,差异可能是最小的。