root/net/disk_cache/memory/mem_backend_impl.cc

DEFINITIONS

1. LowWaterAdjust
2. net_log_
3. CreateBackend
4. Init
5. SetMaxSize
6. InternalDoomEntry
7. UpdateRank
8. ModifyStorageSize
9. MaxFileSize
10. InsertIntoRankingList
11. RemoveFromRankingList
12. GetCacheType
13. GetEntryCount
14. OpenEntry
15. CreateEntry
16. DoomEntry
17. DoomAllEntries
18. DoomEntriesBetween
19. DoomEntriesSince
20. OpenNextEntry
21. EndEnumeration
22. OnExternalCacheHit
23. OpenEntry
24. CreateEntry
25. DoomEntry
26. DoomAllEntries
27. DoomEntriesBetween
28. DoomEntriesSince
29. OpenNextEntry
30. TrimCache
31. AddStorageSize
32. SubstractStorageSize

// 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 "net/disk_cache/memory/mem_backend_impl.h"

#include "base/logging.h"
#include "base/sys_info.h"
#include "net/base/net_errors.h"
#include "net/disk_cache/cache_util.h"
#include "net/disk_cache/memory/mem_entry_impl.h"

using base::Time;

namespace {

const int kDefaultInMemoryCacheSize = 10 * 1024 * 1024;
const int kCleanUpMargin = 1024 * 1024;

int LowWaterAdjust(int high_water) {
  if (high_water < kCleanUpMargin)
    return 0;

  return high_water - kCleanUpMargin;
}

}  // namespace

namespace disk_cache {

MemBackendImpl::MemBackendImpl(net::NetLog* net_log)
    : max_size_(0), current_size_(0), net_log_(net_log) {}

MemBackendImpl::~MemBackendImpl() {
  EntryMap::iterator it = entries_.begin();
  while (it != entries_.end()) {
    it->second->Doom();
    it = entries_.begin();
  }
  DCHECK(!current_size_);
}

// Static.
scoped_ptr<Backend> MemBackendImpl::CreateBackend(int max_bytes,
                                                  net::NetLog* net_log) {
  scoped_ptr<MemBackendImpl> cache(new MemBackendImpl(net_log));
  cache->SetMaxSize(max_bytes);
  if (cache->Init())
    return cache.PassAs<Backend>();

  LOG(ERROR) << "Unable to create cache";
  return scoped_ptr<Backend>();
}

bool MemBackendImpl::Init() {
  if (max_size_)
    return true;

  int64 total_memory = base::SysInfo::AmountOfPhysicalMemory();

  if (total_memory <= 0) {
    max_size_ = kDefaultInMemoryCacheSize;
    return true;
  }

  // We want to use up to 2% of the computer's memory, with a limit of 50 MB,
  // reached on systemd with more than 2.5 GB of RAM.
  total_memory = total_memory * 2 / 100;
  if (total_memory > kDefaultInMemoryCacheSize * 5)
    max_size_ = kDefaultInMemoryCacheSize * 5;
  else
    max_size_ = static_cast<int32>(total_memory);

  return true;
}

bool MemBackendImpl::SetMaxSize(int max_bytes) {
  COMPILE_ASSERT(sizeof(max_bytes) == sizeof(max_size_), unsupported_int_model);
  if (max_bytes < 0)
    return false;

  // Zero size means use the default.
  if (!max_bytes)
    return true;

  max_size_ = max_bytes;
  return true;
}

void MemBackendImpl::InternalDoomEntry(MemEntryImpl* entry) {
  // Only parent entries can be passed into this method.
  DCHECK(entry->type() == MemEntryImpl::kParentEntry);

  rankings_.Remove(entry);
  EntryMap::iterator it = entries_.find(entry->GetKey());
  if (it != entries_.end())
    entries_.erase(it);
  else
    NOTREACHED();

  entry->InternalDoom();
}

void MemBackendImpl::UpdateRank(MemEntryImpl* node) {
  rankings_.UpdateRank(node);
}

void MemBackendImpl::ModifyStorageSize(int32 old_size, int32 new_size) {
  if (old_size >= new_size)
    SubstractStorageSize(old_size - new_size);
  else
    AddStorageSize(new_size - old_size);
}

int MemBackendImpl::MaxFileSize() const {
  return max_size_ / 8;
}

void MemBackendImpl::InsertIntoRankingList(MemEntryImpl* entry) {
  rankings_.Insert(entry);
}

void MemBackendImpl::RemoveFromRankingList(MemEntryImpl* entry) {
  rankings_.Remove(entry);
}

net::CacheType MemBackendImpl::GetCacheType() const {
  return net::MEMORY_CACHE;
}

int32 MemBackendImpl::GetEntryCount() const {
  return static_cast<int32>(entries_.size());
}

int MemBackendImpl::OpenEntry(const std::string& key, Entry** entry,
                              const CompletionCallback& callback) {
  if (OpenEntry(key, entry))
    return net::OK;

  return net::ERR_FAILED;
}

int MemBackendImpl::CreateEntry(const std::string& key, Entry** entry,
                                const CompletionCallback& callback) {
  if (CreateEntry(key, entry))
    return net::OK;

  return net::ERR_FAILED;
}

int MemBackendImpl::DoomEntry(const std::string& key,
                              const CompletionCallback& callback) {
  if (DoomEntry(key))
    return net::OK;

  return net::ERR_FAILED;
}

int MemBackendImpl::DoomAllEntries(const CompletionCallback& callback) {
  if (DoomAllEntries())
    return net::OK;

  return net::ERR_FAILED;
}

int MemBackendImpl::DoomEntriesBetween(const base::Time initial_time,
                                       const base::Time end_time,
                                       const CompletionCallback& callback) {
  if (DoomEntriesBetween(initial_time, end_time))
    return net::OK;

  return net::ERR_FAILED;
}

int MemBackendImpl::DoomEntriesSince(const base::Time initial_time,
                                     const CompletionCallback& callback) {
  if (DoomEntriesSince(initial_time))
    return net::OK;

  return net::ERR_FAILED;
}

int MemBackendImpl::OpenNextEntry(void** iter, Entry** next_entry,
                                  const CompletionCallback& callback) {
  if (OpenNextEntry(iter, next_entry))
    return net::OK;

  return net::ERR_FAILED;
}

void MemBackendImpl::EndEnumeration(void** iter) {
  *iter = NULL;
}

void MemBackendImpl::OnExternalCacheHit(const std::string& key) {
  EntryMap::iterator it = entries_.find(key);
  if (it != entries_.end()) {
    UpdateRank(it->second);
  }
}

bool MemBackendImpl::OpenEntry(const std::string& key, Entry** entry) {
  EntryMap::iterator it = entries_.find(key);
  if (it == entries_.end())
    return false;

  it->second->Open();

  *entry = it->second;
  return true;
}

bool MemBackendImpl::CreateEntry(const std::string& key, Entry** entry) {
  EntryMap::iterator it = entries_.find(key);
  if (it != entries_.end())
    return false;

  MemEntryImpl* cache_entry = new MemEntryImpl(this);
  if (!cache_entry->CreateEntry(key, net_log_)) {
    delete entry;
    return false;
  }

  rankings_.Insert(cache_entry);
  entries_[key] = cache_entry;

  *entry = cache_entry;
  return true;
}

bool MemBackendImpl::DoomEntry(const std::string& key) {
  Entry* entry;
  if (!OpenEntry(key, &entry))
    return false;

  entry->Doom();
  entry->Close();
  return true;
}

bool MemBackendImpl::DoomAllEntries() {
  TrimCache(true);
  return true;
}

bool MemBackendImpl::DoomEntriesBetween(const Time initial_time,
                                        const Time end_time) {
  if (end_time.is_null())
    return DoomEntriesSince(initial_time);

  DCHECK(end_time >= initial_time);

  MemEntryImpl* node = rankings_.GetNext(NULL);
  // Last valid entry before |node|.
  // Note, that entries after |node| may become invalid during |node| doom in
  // case when they are child entries of it. It is guaranteed that
  // parent node will go prior to it childs in ranking list (see
  // InternalReadSparseData and InternalWriteSparseData).
  MemEntryImpl* last_valid = NULL;

  // rankings_ is ordered by last used, this will descend through the cache
  // and start dooming items before the end_time, and will stop once it reaches
  // an item used before the initial time.
  while (node) {
    if (node->GetLastUsed() < initial_time)
      break;

    if (node->GetLastUsed() < end_time)
      node->Doom();
    else
      last_valid = node;
    node = rankings_.GetNext(last_valid);
  }

  return true;
}

bool MemBackendImpl::DoomEntriesSince(const Time initial_time) {
  for (;;) {
    // Get the entry in the front.
    Entry* entry = rankings_.GetNext(NULL);

    // Break the loop when there are no more entries or the entry is too old.
    if (!entry || entry->GetLastUsed() < initial_time)
      return true;
    entry->Doom();
  }
}

bool MemBackendImpl::OpenNextEntry(void** iter, Entry** next_entry) {
  MemEntryImpl* current = reinterpret_cast<MemEntryImpl*>(*iter);
  MemEntryImpl* node = rankings_.GetNext(current);
  // We should never return a child entry so iterate until we hit a parent
  // entry.
  while (node && node->type() != MemEntryImpl::kParentEntry) {
    node = rankings_.GetNext(node);
  }
  *next_entry = node;
  *iter = node;

  if (node)
    node->Open();

  return NULL != node;
}

void MemBackendImpl::TrimCache(bool empty) {
  MemEntryImpl* next = rankings_.GetPrev(NULL);
  if (!next)
    return;

  int target_size = empty ? 0 : LowWaterAdjust(max_size_);
  while (current_size_ > target_size && next) {
    MemEntryImpl* node = next;
    next = rankings_.GetPrev(next);
    if (!node->InUse() || empty) {
      node->Doom();
    }
  }

  return;
}

void MemBackendImpl::AddStorageSize(int32 bytes) {
  current_size_ += bytes;
  DCHECK_GE(current_size_, 0);

  if (current_size_ > max_size_)
    TrimCache(false);
}

void MemBackendImpl::SubstractStorageSize(int32 bytes) {
  current_size_ -= bytes;
  DCHECK_GE(current_size_, 0);
}

}  // namespace disk_cache