Disk cache: Detect hardware failures when reading the headers

net/disk_cache/mapped_file_win.cc

-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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 "net/disk_cache/mapped_file.h"
 
 #include "base/file_path.h"
 #include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
 #include "net/disk_cache/disk_cache.h"
 
 namespace disk_cache {
 
 void* MappedFile::Init(const FilePath& name, size_t size) {
   DCHECK(!init_);
   if (init_ || !File::Init(name))
     return NULL;
 
   buffer_ = NULL;
   init_ = true;
   section_ = CreateFileMapping(platform_file(), NULL, PAGE_READWRITE, 0,
                                static_cast<DWORD>(size), NULL);
   if (!section_)
     return NULL;
 
   buffer_ = MapViewOfFile(section_, FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, size);
   DCHECK(buffer_);
   view_size_ = size;
 
+  // Make sure we detect hardware failures reading the headers.
+  size_t temp_len = size ? size : 4096;
+  scoped_array<char> temp(new char[temp_len]);
+  if (!Read(temp.get(), temp_len, 0))
+    return NULL;

[gavinp, 2011/08/16 17:00:45]

Minor Nit: Although this is almost at the end of the scope, I'd be ε happier if
the scoped_array<char> had been in a scope that ended right after this if.

+
   return buffer_;
 }
 
 MappedFile::~MappedFile() {
   if (!init_)
     return;
 
   if (buffer_) {
     BOOL ret = UnmapViewOfFile(buffer_);
     DCHECK(ret);
   }
 
   if (section_)
     CloseHandle(section_);
 }
 
 bool MappedFile::Load(const FileBlock* block) {
   size_t offset = block->offset() + view_size_;
   return Read(block->buffer(), block->size(), offset);
 }
 
 bool MappedFile::Store(const FileBlock* block) {
   size_t offset = block->offset() + view_size_;
   return Write(block->buffer(), block->size(), offset);
 }
 
 }  // namespace disk_cache