| private FlushWriteAsync ( CancellationToken cancellationToken ) : Task | ||
| cancellationToken | CancellationToken | |
| Результат | 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();
}
}