Fuchsia sockets:

runtime/bin/fdutils_fuchsia.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_FUCHSIA)
 
 #include "bin/fdutils.h"
 
 #include <errno.h>      // NOLINT
@@ skipping 53 matching lines @@
   status = NO_RETRY_EXPECTED(fcntl(fd, F_GETFL));
   if (status < 0) {
     return false;
   }
   *is_blocking = (status & O_NONBLOCK) == 0;
   return true;
 }
 
 
 intptr_t FDUtils::AvailableBytes(intptr_t fd) {
-// TODO(MG-364): Enable this code when it is supported.
-#if 0
   int available;  // ioctl for FIONREAD expects an 'int*' argument.
   int result = NO_RETRY_EXPECTED(ioctl(fd, FIONREAD, &available));
   if (result < 0) {
     return result;
   }
   ASSERT(available >= 0);
   return static_cast<intptr_t>(available);
-#endif
-  errno = ENOTSUP;
-  return -1;
 }
 
 
 ssize_t FDUtils::ReadFromBlocking(int fd, void* buffer, size_t count) {
 #ifdef DEBUG
   bool is_blocking = false;
   ASSERT(FDUtils::IsBlocking(fd, &is_blocking));
   ASSERT(is_blocking);
 #endif
   size_t remaining = count;
@@ skipping 49 matching lines @@
 void FDUtils::SaveErrorAndClose(intptr_t fd) {
   int err = errno;
   NO_RETRY_EXPECTED(close(fd));
   errno = err;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_FUCHSIA)