[NaCl SDK] Support non blocking TCP/UDP

native_client_sdk/src/libraries/nacl_io/fifo_char.h

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef LIBRARIES_NACL_IO_FIFO_CHAR_H_
+#define LIBRARIES_NACL_IO_FIFO_CHAR_H_
+
+#include <vector>
+
+#include "nacl_io/fifo_interface.h"
+
+#include "sdk_util/macros.h"
+
+namespace nacl_io {
+
+// FIFOChar
+//
+// A FIFOChar is a circular buffer, signalling FULL and EMPTY as appropriate.
+class FIFOChar : public FIFOInterface {
+ public:
+  explicit FIFOChar(size_t size);
+  virtual ~FIFOChar();
+
+  virtual bool IsEmpty();
+  virtual bool IsFull();
+  virtual bool Resize(size_t len);
+
+  size_t ReadAvailable();
+  size_t WriteAvailable();
+
+  // Reads out no more than the requested len without updating the tail.
+  // Returns actual amount read.
+  size_t Peek(void* buf, size_t len);
+
+  // Reads out the data making room in the FIFO.  Returns actual amount
+  // read.
+  size_t Read(void* buf, size_t len);
+
+  // Writes into the FIFO no more than len bytes, returns actual amount
+  // written.
+  size_t Write(const void* buf, size_t len);
+
+private:
+  char* buffer_;
+  size_t size_;   // Size of the FIFO
+  size_t avail_;  // How much data is currently available
+  size_t tail_;   // Next read location
+
+  DISALLOW_COPY_AND_ASSIGN(FIFOChar);
+};
+
+}  // namespace nacl_io
+
+#endif  // LIBRARIES_NACL_IO_FIFO_CHAR_H_