Mojo: Implement MojoUnmapBuffer().

mojo/system/mapping_table.cc

+// Copyright 2014 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 "mojo/system/mapping_table.h"
+
+#include "base/logging.h"
+#include "mojo/system/constants.h"
+#include "mojo/system/raw_shared_buffer.h"
+
+namespace mojo {
+namespace system {
+
+MappingTable::MappingTable() {
+}
+
+MappingTable::~MappingTable() {
+  // This should usually not be reached (the only instance should be owned by
+  // the singleton |CoreImpl|, which lives forever), except in tests.
+}
+
+MojoResult MappingTable::AddMapping(
+    scoped_ptr<RawSharedBufferMapping> mapping) {
+  DCHECK(mapping);
+
+  if (address_to_mapping_map_.size() >= kMaxMappingTableSize)
+    return MOJO_RESULT_RESOURCE_EXHAUSTED;
+
+  uintptr_t address = reinterpret_cast<uintptr_t>(mapping->base());
+  DCHECK(address_to_mapping_map_.find(address) ==
+             address_to_mapping_map_.end());
+  address_to_mapping_map_[address] = mapping.release();
+  return MOJO_RESULT_OK;
+}
+
+MojoResult MappingTable::RemoveMapping(void* address) {
+  AddressToMappingMap::iterator it =
+      address_to_mapping_map_.find(reinterpret_cast<uintptr_t>(address));
+  if (it == address_to_mapping_map_.end())
+    return MOJO_RESULT_INVALID_ARGUMENT;
+  delete it->second;

[darin (slow to review), 2014/03/31 23:40:12]

micro-nit: might want to do the .erase() call before running the destructor of
RawSharedBufferMapping as that is slightly foreign code (might have
side-effects). just something i'm probably needlessly pendantic about :-/

+  address_to_mapping_map_.erase(it);
+  return MOJO_RESULT_OK;
+}
+
+}  // namespace system
+}  // namespace mojo