WebSocket Pepper API: fix data corruption at ReceiveMessage in NaCl

ppapi/native_client/src/shared/ppapi_proxy/browser_callback.cc

 // Copyright (c) 2012 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 "native_client/src/shared/ppapi_proxy/browser_callback.h"
 
 #include <new>
 
 #include "native_client/src/include/nacl_macros.h"
 #include "native_client/src/include/nacl_scoped_ptr.h"
@@ skipping 118 matching lines @@
 
   if (bytes_to_read > 0 && buffer != NULL) {
     *buffer = new(std::nothrow) char[bytes_to_read];
     if (*buffer == NULL)  // new failed.
       return PP_BlockUntilComplete();
     remote_callback->read_buffer = *buffer;
   }
   if (var)
     *var = &remote_callback->read_var;
 
+  // If caller requires to copy data at completion, the callback must be
+  // asynchronous. Because the copy is performed in RunRemoteCallback.
+  if ((bytes_to_read > 0 && buffer != NULL) || var)
+    return PP_MakeCompletionCallback(
+        RunRemoteCallback, remote_callback.release());

[dmichael (off chromium), 2012/03/21 19:16:47]

This is going to affect URLLoader::ReadResponseBody, which is designed to
correctly handle an optional callback.

I think it would be better to either:
(a) Make your code also handle the optional case (this would be the best
performing approach, though possibly complicated. You can see the way URLLoader
does it for an example)
(b) Clear the "optional" flag after you get the result from
MakeRemoteCompletionCallback (with appropriate documentation there). This is
probably the simplest way to go, but you won't get as good of performance.

+
   return PP_MakeOptionalCompletionCallback(
       RunRemoteCallback, remote_callback.release());
 }
 
 struct PP_CompletionCallback MakeRemoteCompletionCallback(
     NaClSrpcChannel* srpc_channel,
     int32_t callback_id,
     int32_t bytes_to_read,
     char** buffer,
     CheckResultFunc check_result_func,
@@ skipping 26 matching lines @@
   return MakeRemoteCompletionCallback(srpc_channel, callback_id, 0, NULL);
 }
 
 void DeleteRemoteCallbackInfo(struct PP_CompletionCallback callback) {
   nacl::scoped_ptr<RemoteCallbackInfo> remote_callback(
       reinterpret_cast<RemoteCallbackInfo*>(callback.user_data));
   nacl::scoped_array<char> read_buffer(remote_callback->read_buffer);
 }
 
 }  // namespace ppapi_proxy