Refactor minidump test utilities for MinidumpWritable, …

minidump/minidump_thread_writer_test.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 26 matching lines @@
                          const MINIDUMP_MEMORY_LIST** memory_list) {
   const size_t kDirectoryOffset = sizeof(MINIDUMP_HEADER);
   const uint32_t kExpectedStreams = memory_list ? 2 : 1;
   const size_t kThreadListStreamOffset =
       kDirectoryOffset + kExpectedStreams * sizeof(MINIDUMP_DIRECTORY);
   const size_t kThreadsOffset =
       kThreadListStreamOffset + sizeof(MINIDUMP_THREAD_LIST);
 
   ASSERT_GE(file_contents.size(), kThreadsOffset);
 
+  const MINIDUMP_DIRECTORY* directory;
   const MINIDUMP_HEADER* header =
-      reinterpret_cast<const MINIDUMP_HEADER*>(&file_contents[0]);
-
+      MinidumpHeaderAtStart(file_contents, &directory);
   ASSERT_NO_FATAL_FAILURE(VerifyMinidumpHeader(header, kExpectedStreams, 0));
-
-  const MINIDUMP_DIRECTORY* directory =
-      reinterpret_cast<const MINIDUMP_DIRECTORY*>(
-          &file_contents[kDirectoryOffset]);
+  ASSERT_TRUE(directory);
 
   ASSERT_EQ(kMinidumpStreamTypeThreadList, directory[0].StreamType);
   ASSERT_GE(directory[0].Location.DataSize, sizeof(MINIDUMP_THREAD_LIST));
   ASSERT_EQ(kThreadListStreamOffset, directory[0].Location.Rva);
 
   *thread_list = reinterpret_cast<const MINIDUMP_THREAD_LIST*>(
       &file_contents[kThreadListStreamOffset]);
 
   ASSERT_EQ(sizeof(MINIDUMP_THREAD_LIST) +
                 (*thread_list)->NumberOfThreads * sizeof(MINIDUMP_THREAD),
@@ skipping 416 matching lines @@
   thread_list_writer.AddThread(&thread_writer);
   minidump_file_writer.AddStream(&thread_list_writer);
 
   StringFileWriter file_writer;
   ASSERT_DEATH(minidump_file_writer.WriteEverything(&file_writer), "context_");
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace crashpad