SimpleCache: open with fewer seeks.

net/disk_cache/simple/simple_util.cc

 // Copyright (c) 2013 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/simple/simple_util.h"
 
 #include <limits>
 
 #include "base/files/file_util.h"
 #include "base/format_macros.h"
@@ skipping 79 matching lines @@
 std::string GetSparseFilenameFromEntryHash(uint64_t entry_hash) {
   return base::StringPrintf("%016" PRIx64 "_s", entry_hash);
 }
 
 std::string GetFilenameFromKeyAndFileIndex(const std::string& key,
                                            int file_index) {
   return GetEntryHashKeyAsHexString(key) +
          base::StringPrintf("_%1d", file_index);
 }
 
-int32_t GetDataSizeFromKeyAndFileSize(const std::string& key,
-                                      int64_t file_size) {
+size_t GetHeaderSize(size_t key_length) {
+  return sizeof(SimpleFileHeader) + key_length;
+}
+
+int32_t GetDataSizeFromFileSize(size_t key_length, int64_t file_size) {
   int64_t data_size =
-      file_size - key.size() - sizeof(SimpleFileHeader) - sizeof(SimpleFileEOF);
+      file_size - key_length - sizeof(SimpleFileHeader) - sizeof(SimpleFileEOF);
   return base::checked_cast<int32_t>(data_size);
 }
 
-int64_t GetFileSizeFromKeyAndDataSize(const std::string& key,
-                                      int32_t data_size) {
-  return data_size + key.size() + sizeof(SimpleFileHeader) +
-      sizeof(SimpleFileEOF);
+int64_t GetFileSizeFromDataSize(size_t key_length, int32_t data_size) {
+  return data_size + key_length + sizeof(SimpleFileHeader) +
+         sizeof(SimpleFileEOF);
 }
 
 int GetFileIndexFromStreamIndex(int stream_index) {
   return (stream_index == 2) ? 1 : 0;
 }
 
 // TODO(clamy, gavinp): this should go in base
 bool GetMTime(const base::FilePath& path, base::Time* out_mtime) {
   DCHECK(out_mtime);
 #if defined(OS_POSIX)
@@ skipping 13 matching lines @@
   base::File::Info file_info;
   if (!base::GetFileInfo(path, &file_info))
     return false;
   *out_mtime = file_info.last_modified;
   return true;
 }
 
 }  // namespace simple_backend
 
 }  // namespace disk_cache