Cache backend for devices with flash storage

net/disk_cache/flash/segment.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 "base/logging.h"
 #include "net/disk_cache/flash/format.h"
 #include "net/disk_cache/flash/segment.h"
 #include "net/disk_cache/flash/storage.h"
 
 namespace disk_cache {
 
 Segment::Segment(int32 index, bool read_only, Storage* storage)
     : read_only_(read_only),
       init_(false),
       storage_(storage),
       offset_(index * kFlashSegmentSize),
       summary_offset_(offset_ + kFlashSegmentSize - kFlashSummarySize),
       write_offset_(offset_) {
   DCHECK(storage);
   DCHECK(storage->size() % kFlashSegmentSize == 0);
-  DCHECK(offset_ >= 0 && offset_ + kFlashSegmentSize <= storage->size());
 }
 
 Segment::~Segment() {
-  DCHECK(read_only_);
+  DCHECK(!init_ || read_only_);
 }
 
 bool Segment::Init() {
   if (init_)
     return false;
 
+  if (offset_ < 0 || offset_ + kFlashSegmentSize > storage_->size())
+    return false;
+
   if (!read_only_) {
     init_ = true;
     return true;
   }
 
   int32 summary[kFlashMaxEntryCount + 1];
   if (!storage_->Read(summary, kFlashSummarySize, summary_offset_))
     return false;
 
   size_t entry_count = summary[0];
@@ skipping 33 matching lines @@
 }
 
 bool Segment::Close() {
   DCHECK(init_);
   if (read_only_)
     return true;
 
   DCHECK(header_offsets_.size() <= kFlashMaxEntryCount);
 
   int32 summary[kFlashMaxEntryCount + 1];
+  memset(summary, 0, kFlashSummarySize);
   summary[0] = header_offsets_.size();
   std::copy(header_offsets_.begin(), header_offsets_.end(), summary + 1);
   if (!storage_->Write(summary, kFlashSummarySize, summary_offset_))
     return false;
 
   read_only_ = true;
   return true;
 }
 
 bool Segment::CanHold(int32 size) const {
   return header_offsets_.size() < kFlashMaxEntryCount &&
       write_offset_ + size <= summary_offset_;
 }
 
 }  // namespace disk_cache