net/disk_cache/cache_util.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/disk_cache/cache_util.h"
   6
   7 #include "base/file_util.h"
   8 #include "base/files/file_enumerator.h"
   9 #include "base/location.h"
  10 #include "base/strings/string_util.h"
  11 #include "base/strings/stringprintf.h"
  12 #include "base/threading/thread_restrictions.h"
  13 #include "base/threading/worker_pool.h"
  14
  15 namespace {
  16
  17 const int kMaxOldFolders = 100;
  18
  19 // Returns a fully qualified name from path and name, using a given name prefix
  20 // and index number. For instance, if the arguments are "/foo", "bar" and 5, it
  21 // will return "/foo/old_bar_005".
  22 base::FilePath GetPrefixedName(const base::FilePath& path,
  23                                const std::string& name,
  24                                int index) {
  25   std::string tmp = base::StringPrintf("%s%s_%03d", "old_",
  26                                        name.c_str(), index);
  27   return path.AppendASCII(tmp);
  28 }
  29
  30 // This is a simple callback to cleanup old caches.
  31 void CleanupCallback(const base::FilePath& path, const std::string& name) {
  32   for (int i = 0; i < kMaxOldFolders; i++) {
  33     base::FilePath to_delete = GetPrefixedName(path, name, i);
  34     disk_cache::DeleteCache(to_delete, true);
  35   }
  36 }
  37
  38 // Returns a full path to rename the current cache, in order to delete it. path
  39 // is the current folder location, and name is the current folder name.
  40 base::FilePath GetTempCacheName(const base::FilePath& path,
  41                                 const std::string& name) {
  42   // We'll attempt to have up to kMaxOldFolders folders for deletion.
  43   for (int i = 0; i < kMaxOldFolders; i++) {
  44     base::FilePath to_delete = GetPrefixedName(path, name, i);
  45     if (!base::PathExists(to_delete))
  46       return to_delete;
  47   }
  48   return base::FilePath();
  49 }
  50
  51 int64 PreferredCacheSizeInternal(int64 available) {
  52   using disk_cache::kDefaultCacheSize;
  53   // Return 80% of the available space if there is not enough space to use
  54   // kDefaultCacheSize.
  55   if (available < kDefaultCacheSize * 10 / 8)
  56     return available * 8 / 10;
  57
  58   // Return kDefaultCacheSize if it uses 10% to 80% of the available space.
  59   if (available < kDefaultCacheSize * 10)
  60     return kDefaultCacheSize;
  61
  62   // Return 10% of the available space if the target size
  63   // (2.5 * kDefaultCacheSize) is more than 10%.
  64   if (available < static_cast<int64>(kDefaultCacheSize) * 25)
  65     return available / 10;
  66
  67   // Return the target size (2.5 * kDefaultCacheSize) if it uses 10% to 1%
  68   // of the available space.
  69   if (available < static_cast<int64>(kDefaultCacheSize) * 250)
  70     return kDefaultCacheSize * 5 / 2;
  71
  72   // Return 1% of the available space.
  73   return available / 100;
  74 }
  75
  76 }  // namespace
  77
  78 namespace disk_cache {
  79
  80 const int kDefaultCacheSize = 80 * 1024 * 1024;
  81
  82 void DeleteCache(const base::FilePath& path, bool remove_folder) {
  83   if (remove_folder) {
  84     if (!base::DeleteFile(path, /* recursive */ true))
  85       LOG(WARNING) << "Unable to delete cache folder.";
  86     return;
  87   }
  88
  89   base::FileEnumerator iter(
  90       path,
  91       /* recursive */ false,
  92       base::FileEnumerator::FILES | base::FileEnumerator::DIRECTORIES);
  93   for (base::FilePath file = iter.Next(); !file.value().empty();
  94        file = iter.Next()) {
  95     if (!base::DeleteFile(file, /* recursive */ true)) {
  96       LOG(WARNING) << "Unable to delete cache.";
  97       return;
  98     }
  99   }
 100 }
 101
 102 // In order to process a potentially large number of files, we'll rename the
 103 // cache directory to old_ + original_name + number, (located on the same parent
 104 // directory), and use a worker thread to delete all the files on all the stale
 105 // cache directories. The whole process can still fail if we are not able to
 106 // rename the cache directory (for instance due to a sharing violation), and in
 107 // that case a cache for this profile (on the desired path) cannot be created.
 108 bool DelayedCacheCleanup(const base::FilePath& full_path) {
 109   // GetTempCacheName() and MoveCache() use synchronous file
 110   // operations.
 111   base::ThreadRestrictions::ScopedAllowIO allow_io;
 112
 113   base::FilePath current_path = full_path.StripTrailingSeparators();
 114
 115   base::FilePath path = current_path.DirName();
 116   base::FilePath name = current_path.BaseName();
 117 #if defined(OS_POSIX)
 118   std::string name_str = name.value();
 119 #elif defined(OS_WIN)
 120   // We created this file so it should only contain ASCII.
 121   std::string name_str = WideToASCII(name.value());
 122 #endif
 123
 124   base::FilePath to_delete = GetTempCacheName(path, name_str);
 125   if (to_delete.empty()) {
 126     LOG(ERROR) << "Unable to get another cache folder";
 127     return false;
 128   }
 129
 130   if (!disk_cache::MoveCache(full_path, to_delete)) {
 131     LOG(ERROR) << "Unable to move cache folder " << full_path.value() << " to "
 132                << to_delete.value();
 133     return false;
 134   }
 135
 136   base::WorkerPool::PostTask(
 137       FROM_HERE, base::Bind(&CleanupCallback, path, name_str), true);
 138   return true;
 139 }
 140
 141 // Returns the preferred maximum number of bytes for the cache given the
 142 // number of available bytes.
 143 int PreferredCacheSize(int64 available) {
 144   if (available < 0)
 145     return kDefaultCacheSize;
 146
 147   int64 max_size = PreferredCacheSizeInternal(available);
 148
 149   // Limit cache size to somewhat less than kint32max to avoid potential
 150   // integer overflows in cache backend implementations.
 151   DCHECK(kDefaultCacheSize * 4 < kint32max);
 152   if (max_size > kDefaultCacheSize * 4)
 153     max_size = kDefaultCacheSize * 4;
 154
 155   return implicit_cast<int32>(max_size);
 156 }
 157
 158 }  // namespace disk_cache