Convert BeginReadData...() to use the new user pointer handling (see r285350).

mojo/system/local_data_pipe.cc

 // Copyright 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.
 
 // TODO(vtl): I currently potentially overflow in doing index calculations.
 // E.g., |start_index_| and |current_num_bytes_| fit into a |uint32_t|, but
 // their sum may not. This is bad and poses a security risk. (We're currently
 // saved by the limit on capacity -- the maximum size of the buffer, checked in
 // |DataPipe::ValidateOptions()|, is currently sufficiently small.
 
@@ skipping 222 matching lines @@
   return MOJO_RESULT_OK;
 }
 
 MojoResult LocalDataPipe::ConsumerQueryDataImplNoLock(uint32_t* num_bytes) {
   // Note: This cast is safe, since the capacity fits into a |uint32_t|.
   *num_bytes = static_cast<uint32_t>(current_num_bytes_);
   return MOJO_RESULT_OK;
 }
 
 MojoResult LocalDataPipe::ConsumerBeginReadDataImplNoLock(
-    const void** buffer,
-    uint32_t* buffer_num_bytes,
-    bool all_or_none) {
+    UserPointer<const void*> buffer,
+    UserPointer<uint32_t> buffer_num_bytes,
+    uint32_t min_num_bytes_to_read) {
   size_t max_num_bytes_to_read = GetMaxNumBytesToReadNoLock();
-  if (all_or_none && *buffer_num_bytes > max_num_bytes_to_read) {
+  if (min_num_bytes_to_read > max_num_bytes_to_read) {
     // Don't return "should wait" since you can't wait for a specified amount of
     // data.
     return producer_open_no_lock() ? MOJO_RESULT_OUT_OF_RANGE :
                                      MOJO_RESULT_FAILED_PRECONDITION;
   }
 
   // Don't go into a two-phase read if there's no data.
   if (max_num_bytes_to_read == 0) {
     return producer_open_no_lock() ? MOJO_RESULT_SHOULD_WAIT :
                                      MOJO_RESULT_FAILED_PRECONDITION;
   }
 
-  *buffer = buffer_.get() + start_index_;
-  *buffer_num_bytes = static_cast<uint32_t>(max_num_bytes_to_read);
+  buffer.Put(buffer_.get() + start_index_);
+  buffer_num_bytes.Put(static_cast<uint32_t>(max_num_bytes_to_read));
   set_consumer_two_phase_max_num_bytes_read_no_lock(
       static_cast<uint32_t>(max_num_bytes_to_read));
   return MOJO_RESULT_OK;
 }
 
 MojoResult LocalDataPipe::ConsumerEndReadDataImplNoLock(
     uint32_t num_bytes_read) {
   DCHECK_LE(num_bytes_read, consumer_two_phase_max_num_bytes_read_no_lock());
   DCHECK_LE(start_index_ + num_bytes_read, capacity_num_bytes());
   MarkDataAsConsumedNoLock(num_bytes_read);
@@ skipping 51 matching lines @@
 
 void LocalDataPipe::MarkDataAsConsumedNoLock(size_t num_bytes) {
   DCHECK_LE(num_bytes, current_num_bytes_);
   start_index_ += num_bytes;
   start_index_ %= capacity_num_bytes();
   current_num_bytes_ -= num_bytes;
 }
 
 }  // namespace system
 }  // namespace mojo