SimpleCache: merge the first and second stream in one file

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/file_util.h"
 #include "base/format_macros.h"
@@ skipping 80 matching lines @@
                     sizeof(SimpleFileEOF);
   DCHECK_GE(implicit_cast<int64>(std::numeric_limits<int32>::max()), data_size);
   return data_size;
 }
 
 int64 GetFileSizeFromKeyAndDataSize(const std::string& key, int32 data_size) {
   return data_size + key.size() + sizeof(SimpleFileHeader) +
       sizeof(SimpleFileEOF);
 }
 
-int64 GetFileOffsetFromKeyAndDataOffset(const std::string& key,
-                                        int data_offset) {
+int GetFileIndexFromStreamIndex(int stream_index) {
+  return (stream_index == 2) ? 1 : 0;
+}
+
+int GetLastEOFRecordOffset(int file_index, const int data_size[]) {
+  if (file_index == 0)
+    return data_size[0] + data_size[1] + sizeof(SimpleFileEOF);

[Deprecated (see juliatuttle), 2013/09/16 20:01:52]

This looks like it's vulnerable to an integer overflow if someone manages to
cache a 2+ GB resource in stream 1 -- the stream 0 offset could easily end up
negative.  (For that matter, caching something that is INT_MAX could still make
the offset of the last SimpleFileHeader's worth of the resource negative.)

[pasko, 2013/09/17 10:06:34]

This should be fine.

Currently Write operations will start failing after reaching 1/8 of the cache
size, which itself is itself an int32, so this leaves a maximum of 256MiB of
data per entry stream.

+  return data_size[2];
+}
+
+int64 GetFileOffsetFromDataOffset(const std::string& key,
+                                  int data_offset,
+                                  int index,
+                                  int stream_1_size) {
   const int64 headers_size = sizeof(disk_cache::SimpleFileHeader) + key.size();
-  return headers_size + data_offset;
+  const int64 additional_offset =
+      index == 0 ? stream_1_size + sizeof(SimpleFileEOF) : 0;
+  return headers_size + data_offset + additional_offset;
 }
 
 // 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)
   base::ThreadRestrictions::AssertIOAllowed();
   struct stat file_stat;
   if (stat(path.value().c_str(), &file_stat) != 0)
     return false;
   time_t sec;
   long nsec;
   if (GetNanoSecsFromStat(file_stat, &sec, &nsec)) {
     int64 usec = (nsec / base::Time::kNanosecondsPerMicrosecond);
     *out_mtime = base::Time::FromTimeT(sec)
         + base::TimeDelta::FromMicroseconds(usec);
     return true;
   }
 #endif
   base::PlatformFileInfo file_info;
   if (!file_util::GetFileInfo(path, &file_info))
     return false;
   *out_mtime = file_info.last_modified;
   return true;
 }
 
 }  // namespace simple_backend
 
 }  // namespace disk_cache