Add an implementation of base::SyncSocket::Peek for posix platforms.

base/sync_socket_posix.cc

 // Copyright (c) 2009 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.
 
 #include "base/sync_socket.h"
 
 #include <errno.h>
 #include <limits.h>
 #include <stdio.h>
 #include <sys/types.h>
+#include <sys/ioctl.h>
 #include <sys/socket.h>
 
 #include "base/atomicops.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 
 
 namespace base {
 
 namespace {
@@ skipping 70 matching lines @@
 size_t SyncSocket::Receive(void* buffer, size_t length) {
   DCHECK(length <= kMaxMessageLength);
   char* charbuffer = static_cast<char*>(buffer);
   if (file_util::ReadFromFD(handle_, charbuffer, length)) {
     return length;
   } else {
     return -1;
   }
 }
 
-// TODO(port). Some kind of select?
 size_t SyncSocket::Peek() {
-  NOTIMPLEMENTED();
-  return 0;
+  int number_chars;
+  if (-1 == ioctl(handle_, FIONREAD, &number_chars)) {
+    // If there is an error in ioctl, signal that the channel would block.
+    return 0;
+  }
+  return (size_t) number_chars;
 }
 
 }  // namespace base