FlushWriteAsync() private méthode

private FlushWriteAsync ( CancellationToken cancellationToken ) : Task
cancellationToken CancellationToken
Résultat Task
    private static async Task FlushAsyncInternal(CancellationToken cancellationToken,
                                                 BufferedStream _this, Stream stream, Int32 writePos, Int32 readPos, Int32 readLen) {
        
        // We bring instance fields down as local parameters to this async method becasue BufferedStream is derived from MarshalByRefObject.
        // Field access would be from the async state machine i.e., not via the this pointer and would require runtime checking to see
        // if we are talking to a remote object, which is currently very slow 

        Contract.Assert(stream != null);        
        
        SemaphoreSlim sem = _this.EnsureAsyncActiveSemaphoreInitialized();
        await sem.WaitAsync().ConfigureAwait(false);
        try {

            if (writePos > 0) {

                await _this.FlushWriteAsync(cancellationToken).ConfigureAwait(false);
                Contract.Assert(_this._writePos == 0 && _this._readPos == 0 && _this._readLen == 0);
                return;
            }        

            if (readPos < readLen) {

                // If the underlying stream is not seekable AND we have something in the read buffer, then FlushRead would throw.
                // We can either throw away the buffer resulting in date loss (!) or ignore the Flush. (We cannot throw becasue it
                // would be a breaking change.) We opt into ignoring the Flush in that situation.
                if (!stream.CanSeek)
                    return;                                   

                _this.FlushRead();  // not async; it uses Seek, but there's no SeekAsync

                // User streams may have opted to throw from Flush if CanWrite is false (although the abstract Stream does not do so).
                // However, if we do not forward the Flush to the underlying stream, we may have problems when chaining several streams.
                // Let us make a best effort attempt:
                if (stream.CanRead || stream is BufferedStream)
                    await stream.FlushAsync(cancellationToken).ConfigureAwait(false);

                Contract.Assert(_this._writePos == 0 && _this._readPos == 0 && _this._readLen == 0);
                return;
            }            

            // We had no data in the buffer, but we still need to tell the underlying stream to flush.
            if (stream.CanWrite || stream is BufferedStream)
                await stream.FlushAsync(cancellationToken).ConfigureAwait(false);

            // There was nothing in the buffer:
            Contract.Assert(_this._writePos == 0 && _this._readPos == _this._readLen);

        } finally {
            sem.Release();
        }
    }