Asynchronous initialization in Simple Index.

net/disk_cache/simple/simple_index.cc

Index: net/disk_cache/simple/simple_index.cc
diff --git a/net/disk_cache/simple/simple_index.cc b/net/disk_cache/simple/simple_index.cc
index cff8b011c6e3bce20f0b7b756fcb3d32b1312939..027004747e73f8f39ca7c5be39b47474d6504f96 100644
--- a/net/disk_cache/simple/simple_index.cc
+++ b/net/disk_cache/simple/simple_index.cc
@@ -37,29 +37,75 @@ bool CheckHeader(disk_cache::SimpleIndexFile::Header header) {
       header.version == disk_cache::kSimpleVersion;
 }
 
+class FileAutoCloser {
+ public:
+  explicit FileAutoCloser(const base::PlatformFile& file) : file_(file) { }
+  ~FileAutoCloser() {
+    base::ClosePlatformFile(file_);
+  }
+ private:
+  base::PlatformFile file_;
+  DISALLOW_COPY_AND_ASSIGN(FileAutoCloser);
+};
+
 }  // namespace
 
 namespace disk_cache {
 
 SimpleIndex::SimpleIndex(
     const scoped_refptr<base::TaskRunner>& cache_thread,
+    const scoped_refptr<base::TaskRunner>& io_thread,
     const base::FilePath& path)
-    : path_(path),
-      cache_thread_(cache_thread) {
-  index_filename_ = path_.AppendASCII("index");
+    : cache_size_(0),
+      initialized_(false),
+      index_filename_(path.AppendASCII("simple-index")),
+      cache_thread_(cache_thread),
+      io_thread_(io_thread) {}
+
+SimpleIndex::~SimpleIndex() {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+}
+
+void SimpleIndex::Initialize() {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  MergeCallback merge_callback = base::Bind(&SimpleIndex::MergeInitializingSet,
+                                            this->AsWeakPtr());
+  base::WorkerPool::PostTask(FROM_HERE,
+                             base::Bind(&SimpleIndex::LoadFromDisk,
+                                        index_filename_,
+                                        io_thread_,
+                                        merge_callback),
+                             true);
 }
 
-bool SimpleIndex::Initialize() {
-  if (!OpenIndexFile())
-    return RestoreFromDisk();
+// static
+void SimpleIndex::LoadFromDisk(
+    const base::FilePath& index_filename,
+    const scoped_refptr<base::TaskRunner>& io_thread,
+    const MergeCallback& merge_callback) {
+  // Open the index file.
+  base::PlatformFileError error;
+  base::PlatformFile index_file = base::CreatePlatformFile(
+      index_filename,
+      base::PLATFORM_FILE_OPEN_ALWAYS |
+      base::PLATFORM_FILE_READ |
+      base::PLATFORM_FILE_WRITE,
+      NULL,
+      &error);
+  FileAutoCloser auto_close_index_file(index_file);
+  if (error != base::PLATFORM_FILE_OK) {
+    LOG(ERROR) << "Error opening file " << index_filename.value();
+    return RestoreFromDisk(index_filename, io_thread, merge_callback);
+  }
+
   uLong incremental_crc = crc32(0L, Z_NULL, 0);
   int64 index_file_offset = 0;
   SimpleIndexFile::Header header;
-  if (base::ReadPlatformFile(index_file_,
+  if (base::ReadPlatformFile(index_file,
                              index_file_offset,
                              reinterpret_cast<char*>(&header),
                              sizeof(header)) != sizeof(header)) {
-    return RestoreFromDisk();
+    return RestoreFromDisk(index_filename, io_thread, merge_callback);
   }
   index_file_offset += sizeof(header);
   incremental_crc = crc32(incremental_crc,
@@ -68,18 +114,18 @@ bool SimpleIndex::Initialize() {
 
   if (!CheckHeader(header)) {
     LOG(ERROR) << "Invalid header on Simple Cache Index.";
-    return RestoreFromDisk();
+    return RestoreFromDisk(index_filename, io_thread, merge_callback);
   }
 
   const int entries_buffer_size =
       header.number_of_entries * SimpleIndexFile::kEntryMetadataSize;
 
   scoped_ptr<char[]> entries_buffer(new char[entries_buffer_size]);
-  if (base::ReadPlatformFile(index_file_,
+  if (base::ReadPlatformFile(index_file,
                              index_file_offset,
                              entries_buffer.get(),
                              entries_buffer_size) != entries_buffer_size) {
-    return RestoreFromDisk();
+    return RestoreFromDisk(index_filename, io_thread, merge_callback);
   }
   index_file_offset += entries_buffer_size;
   incremental_crc = crc32(incremental_crc,
@@ -87,56 +133,76 @@ bool SimpleIndex::Initialize() {
                           implicit_cast<uInt>(entries_buffer_size));
 
   SimpleIndexFile::Footer footer;
-  if (base::ReadPlatformFile(index_file_,
+  if (base::ReadPlatformFile(index_file,
                              index_file_offset,
                              reinterpret_cast<char*>(&footer),
                              sizeof(footer)) != sizeof(footer)) {
-    return RestoreFromDisk();
+    return RestoreFromDisk(index_filename, io_thread, merge_callback);
   }
   const uint32 crc_read = footer.crc;
   const uint32 crc_calculated = incremental_crc;
   if (crc_read != crc_calculated)
-    return RestoreFromDisk();
+    return RestoreFromDisk(index_filename, io_thread, merge_callback);
 
+  scoped_ptr<EntrySet> index_file_entries(new EntrySet());
   int entries_buffer_offset = 0;
   while(entries_buffer_offset < entries_buffer_size) {
     SimpleIndexFile::EntryMetadata entry_metadata;
     SimpleIndexFile::EntryMetadata::DeSerialize(
         &entries_buffer.get()[entries_buffer_offset], &entry_metadata);
-    InsertInternal(entry_metadata);
+    InsertInternal(index_file_entries.get(), entry_metadata);
     entries_buffer_offset += SimpleIndexFile::kEntryMetadataSize;
   }
-  DCHECK_EQ(header.number_of_entries, entries_set_.size());
-  CloseIndexFile();
-  return true;
+  DCHECK_EQ(header.number_of_entries, index_file_entries->size());
+
+  io_thread->PostTask(FROM_HERE,
+                      base::Bind(merge_callback,
+                                 base::Passed(&index_file_entries)));
 }
 
 void SimpleIndex::Insert(const std::string& key) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
   // Upon insert we don't know yet the size of the entry.
   // It will be updated later when the SimpleEntryImpl finishes opening or
   // creating the new entry, and then UpdateEntrySize will be called.
-  InsertInternal(SimpleIndexFile::EntryMetadata(GetEntryHashForKey(key),
-                                                base::Time::Now(), 0));
+  const std::string hash_key = GetEntryHashForKey(key);
+  InsertInternal(&entries_set_, SimpleIndexFile::EntryMetadata(
+      hash_key,
+      base::Time::Now(), 0));
+  if (!initialized_)
+    removed_entries_.erase(hash_key);
 }
 
 void SimpleIndex::Remove(const std::string& key) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
   UpdateEntrySize(key, 0);
-  entries_set_.erase(GetEntryHashForKey(key));
+  const std::string hash_key = GetEntryHashForKey(key);
+  entries_set_.erase(hash_key);
+
+  if (!initialized_)
+    removed_entries_.insert(hash_key);
 }
 
 bool SimpleIndex::Has(const std::string& key) const {
-  return entries_set_.count(GetEntryHashForKey(key)) != 0;
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  // If not initialized, always return true, forcing it to go to the disk.
+  return !initialized_ || entries_set_.count(GetEntryHashForKey(key)) != 0;
 }
 
 bool SimpleIndex::UseIfExists(const std::string& key) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  // Always update the last used time, even if it is during initialization.
+  // It will be merged later.
   EntrySet::iterator it = entries_set_.find(GetEntryHashForKey(key));
   if (it == entries_set_.end())
-    return false;
+    // If not initialized, always return true, forcing it to go to the disk.
+    return !initialized_;
   it->second.SetLastUsedTime(base::Time::Now());
   return true;
 }
 
 bool SimpleIndex::UpdateEntrySize(const std::string& key, uint64 entry_size) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
   EntrySet::iterator it = entries_set_.find(GetEntryHashForKey(key));
   if (it == entries_set_.end())
     return false;
@@ -149,27 +215,34 @@ bool SimpleIndex::UpdateEntrySize(const std::string& key, uint64 entry_size) {
   return true;
 }
 
+// static
 void SimpleIndex::InsertInternal(
+    EntrySet* entry_set,
     const SimpleIndexFile::EntryMetadata& entry_metadata) {
-  entries_set_.insert(make_pair(entry_metadata.GetHashKey(), entry_metadata));
+  // TODO(felipeg): Use a hash_set instead of a hash_map.
+  DCHECK(entry_set);
+  entry_set->insert(make_pair(entry_metadata.GetHashKey(), entry_metadata));
 }
 
-bool SimpleIndex::RestoreFromDisk() {
+// static
+void SimpleIndex::RestoreFromDisk(
+    const base::FilePath& index_filename,
+    const scoped_refptr<base::TaskRunner>& io_thread,
+    const MergeCallback& merge_callback) {
   using file_util::FileEnumerator;
   LOG(INFO) << "Simple Cache Index is being restored from disk.";
-  CloseIndexFile();
-  file_util::Delete(index_filename_, /* recursive = */ false);
-  entries_set_.clear();
+
+  file_util::Delete(index_filename, /* recursive = */ false);
+  scoped_ptr<EntrySet> index_file_entries(new EntrySet());
 
   // TODO(felipeg,gavinp): Fix this once we have a one-file per entry format.
   COMPILE_ASSERT(kSimpleEntryFileCount == 3,
                  file_pattern_must_match_file_count);
   const base::FilePath::StringType file_pattern = FILE_PATH_LITERAL("*_[0-2]");
-  FileEnumerator enumerator(path_,
+  FileEnumerator enumerator(index_filename.DirName(),
                             false /* recursive */,
                             FileEnumerator::FILES,
                             file_pattern);
-
   for (base::FilePath file_path = enumerator.Next(); !file_path.empty();
        file_path = enumerator.Next()) {
     const base::FilePath::StringType base_name = file_path.BaseName().value();
@@ -190,9 +263,9 @@ bool SimpleIndex::RestoreFromDisk() {
       last_used_time = FileEnumerator::GetLastModifiedTime(find_info);
 
     int64 file_size = FileEnumerator::GetFilesize(find_info);
-    EntrySet::iterator it = entries_set_.find(hash_key);
-    if (it == entries_set_.end()) {
-      InsertInternal(SimpleIndexFile::EntryMetadata(
+    EntrySet::iterator it = index_file_entries->find(hash_key);
+    if (it == index_file_entries->end()) {
+      InsertInternal(index_file_entries.get(), SimpleIndexFile::EntryMetadata(
           hash_key, last_used_time, file_size));
     } else {
       // Summing up the total size of the entry through all the *_[0-2] files
@@ -200,11 +273,45 @@ bool SimpleIndex::RestoreFromDisk() {
     }
   }
 
-  // TODO(felipeg): Detect unrecoverable problems and return false here.
-  return true;
+  io_thread->PostTask(FROM_HERE,
+                      base::Bind(merge_callback,
+                                 base::Passed(&index_file_entries)));
+}
+
+void SimpleIndex::MergeInitializingSet(
+    scoped_ptr<EntrySet> index_file_entries) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  // First, remove the entries that are in the |removed_entries_| from both
+  // sets.
+  for (base::hash_set<std::string>::const_iterator it =
+           removed_entries_.begin(); it != removed_entries_.end(); ++it) {
+    entries_set_.erase(*it);
+    index_file_entries->erase(*it);
+  }
+
+  // Recalculate the cache size while merging the two sets.
+  cache_size_ = 0;
+  for (EntrySet::const_iterator it = index_file_entries->begin();
+       it != index_file_entries->end(); ++it) {
+    // If there is already an entry in the current entries_set_, we need to
+    // merge the new data there with the data loaded in the initialization.
+    EntrySet::iterator current_entry = entries_set_.find(it->first);
+    if (current_entry != entries_set_.end()) {
+      // When Merging, existing valid data in the |current_entry| will prevail.
+      SimpleIndexFile::EntryMetadata::Merge(
+          it->second, &(current_entry->second));
+      cache_size_ += current_entry->second.entry_size;
+    } else {
+      InsertInternal(&entries_set_, it->second);
+      cache_size_ += it->second.entry_size;
+    }
+  }
+
+  initialized_ = true;
 }
 
 void SimpleIndex::Serialize(std::string* out_buffer) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
   DCHECK(out_buffer);
   SimpleIndexFile::Header header;
   SimpleIndexFile::Footer footer;
@@ -235,37 +342,15 @@ void SimpleIndex::Serialize(std::string* out_buffer) {
   out_buffer->append(reinterpret_cast<const char*>(&footer), sizeof(footer));
 }
 
-void SimpleIndex::Cleanup() {
+void SimpleIndex::WriteToDisk() {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
   scoped_ptr<std::string> buffer(new std::string());
   Serialize(buffer.get());
-  cache_thread_->PostTask(FROM_HERE,
-                            base::Bind(&SimpleIndex::UpdateFile,
-                                       index_filename_,
-                                       path_.AppendASCII("index_temp"),
-                                       base::Passed(&buffer)));
-}
-
-SimpleIndex::~SimpleIndex() {
-  CloseIndexFile();
-}
-
-bool SimpleIndex::OpenIndexFile() {
-  base::PlatformFileError error;
-  index_file_ = base::CreatePlatformFile(index_filename_,
-                                         base::PLATFORM_FILE_OPEN_ALWAYS |
-                                         base::PLATFORM_FILE_READ |
-                                         base::PLATFORM_FILE_WRITE,
-                                         NULL,
-                                         &error);
-  if (error != base::PLATFORM_FILE_OK) {
-    LOG(ERROR) << "Error opening file " << index_filename_.value();
-    return false;
-  }
-  return true;
-}
-
-bool SimpleIndex::CloseIndexFile() {
-  return base::ClosePlatformFile(index_file_);
+  cache_thread_->PostTask(FROM_HERE, base::Bind(
+      &SimpleIndex::UpdateFile,
+      index_filename_,
+      index_filename_.DirName().AppendASCII("index_temp"),
+      base::Passed(&buffer)));
 }
 
 // static