root/webkit/browser/fileapi/isolated_context.cc

DEFINITIONS

1. GetRegisterNameForPath
2. IsSinglePathIsolatedFileSystem
3. AddPath
4. AddPathWithName
5. type
6. file_info
7. files
8. ref_counts
9. AddRef
10. RemoveRef
11. ref_counts_
12. ref_counts_
13. ResolvePathForName
14. IsSinglePathInstance
15. GetInstance
16. IsIsolatedType
17. RegisterDraggedFileSystem
18. RegisterFileSystemForPath
19. RegisterFileSystemForVirtualPath
20. HandlesFileSystemMountType
21. RevokeFileSystem
22. GetRegisteredPath
23. CrackVirtualPath
24. CrackURL
25. CreateCrackedFileSystemURL
26. RevokeFileSystemByPath
27. AddReference
28. RemoveReference
29. GetDraggedFileInfo
30. CreateVirtualRootPath
31. CrackFileSystemURL
32. UnregisterFileSystem
33. GetNewFileSystemId

// 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 "webkit/browser/fileapi/isolated_context.h"

#include "base/basictypes.h"
#include "base/files/file_path.h"
#include "base/logging.h"
#include "base/rand_util.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "webkit/browser/fileapi/file_system_url.h"

namespace fileapi {

namespace {

base::FilePath::StringType GetRegisterNameForPath(const base::FilePath& path) {
  // If it's not a root path simply return a base name.
  if (path.DirName() != path)
    return path.BaseName().value();

#if defined(FILE_PATH_USES_DRIVE_LETTERS)
  base::FilePath::StringType name;
  for (size_t i = 0;
       i < path.value().size() && !base::FilePath::IsSeparator(path.value()[i]);
       ++i) {
    if (path.value()[i] == L':') {
      name.append(L"_drive");
      break;
    }
    name.append(1, path.value()[i]);
  }
  return name;
#else
  return FILE_PATH_LITERAL("<root>");
#endif
}

bool IsSinglePathIsolatedFileSystem(FileSystemType type) {
  DCHECK_NE(kFileSystemTypeUnknown, type);
  // As of writing dragged file system is the only filesystem which could have
  // multiple top-level paths.
  return type != kFileSystemTypeDragged;
}

static base::LazyInstance<IsolatedContext>::Leaky g_isolated_context =
    LAZY_INSTANCE_INITIALIZER;

}  // namespace

IsolatedContext::FileInfoSet::FileInfoSet() {}
IsolatedContext::FileInfoSet::~FileInfoSet() {}

bool IsolatedContext::FileInfoSet::AddPath(
    const base::FilePath& path, std::string* registered_name) {
  // The given path should not contain any '..' and should be absolute.
  if (path.ReferencesParent() || !path.IsAbsolute())
    return false;
  base::FilePath::StringType name = GetRegisterNameForPath(path);
  std::string utf8name = base::FilePath(name).AsUTF8Unsafe();
  base::FilePath normalized_path = path.NormalizePathSeparators();
  bool inserted =
      fileset_.insert(MountPointInfo(utf8name, normalized_path)).second;
  if (!inserted) {
    int suffix = 1;
    std::string basepart =
        base::FilePath(name).RemoveExtension().AsUTF8Unsafe();
    std::string ext =
        base::FilePath(base::FilePath(name).Extension()).AsUTF8Unsafe();
    while (!inserted) {
      utf8name = base::StringPrintf("%s (%d)", basepart.c_str(), suffix++);
      if (!ext.empty())
        utf8name.append(ext);
      inserted =
          fileset_.insert(MountPointInfo(utf8name, normalized_path)).second;
    }
  }
  if (registered_name)
    *registered_name = utf8name;
  return true;
}

bool IsolatedContext::FileInfoSet::AddPathWithName(
    const base::FilePath& path, const std::string& name) {
  // The given path should not contain any '..' and should be absolute.
  if (path.ReferencesParent() || !path.IsAbsolute())
    return false;
  return fileset_.insert(
      MountPointInfo(name, path.NormalizePathSeparators())).second;
}

//--------------------------------------------------------------------------

class IsolatedContext::Instance {
 public:
  enum PathType {
    PLATFORM_PATH,
    VIRTUAL_PATH
  };

  // For a single-path isolated file system, which could be registered by
  // IsolatedContext::RegisterFileSystemForPath() or
  // IsolatedContext::RegisterFileSystemForVirtualPath().
  // Most of isolated file system contexts should be of this type.
  Instance(FileSystemType type, const MountPointInfo& file_info,
           PathType path_type);

  // For a multi-paths isolated file system.  As of writing only file system
  // type which could have multi-paths is Dragged file system, and
  // could be registered by IsolatedContext::RegisterDraggedFileSystem().
  Instance(FileSystemType type, const std::set<MountPointInfo>& files);

  ~Instance();

  FileSystemType type() const { return type_; }
  const MountPointInfo& file_info() const { return file_info_; }
  const std::set<MountPointInfo>& files() const { return files_; }
  int ref_counts() const { return ref_counts_; }

  void AddRef() { ++ref_counts_; }
  void RemoveRef() { --ref_counts_; }

  bool ResolvePathForName(const std::string& name, base::FilePath* path) const;

  // Returns true if the instance is a single-path instance.
  bool IsSinglePathInstance() const;

 private:
  const FileSystemType type_;

  // For single-path instance.
  const MountPointInfo file_info_;
  const PathType path_type_;

  // For multiple-path instance (e.g. dragged file system).
  const std::set<MountPointInfo> files_;

  // Reference counts. Note that an isolated filesystem is created with ref==0
  // and will get deleted when the ref count reaches <=0.
  int ref_counts_;

  DISALLOW_COPY_AND_ASSIGN(Instance);
};

IsolatedContext::Instance::Instance(FileSystemType type,
                                    const MountPointInfo& file_info,
                                    Instance::PathType path_type)
    : type_(type),
      file_info_(file_info),
      path_type_(path_type),
      ref_counts_(0) {
  DCHECK(IsSinglePathIsolatedFileSystem(type_));
}

IsolatedContext::Instance::Instance(FileSystemType type,
                                    const std::set<MountPointInfo>& files)
    : type_(type),
      path_type_(PLATFORM_PATH),
      files_(files),
      ref_counts_(0) {
  DCHECK(!IsSinglePathIsolatedFileSystem(type_));
}

IsolatedContext::Instance::~Instance() {}

bool IsolatedContext::Instance::ResolvePathForName(const std::string& name,
                                                   base::FilePath* path) const {
  if (IsSinglePathIsolatedFileSystem(type_)) {
    switch (path_type_) {
      case PLATFORM_PATH:
        *path = file_info_.path;
        break;
      case VIRTUAL_PATH:
        *path = base::FilePath();
        break;
      default:
        NOTREACHED();
    }

    return file_info_.name == name;
  }
  std::set<MountPointInfo>::const_iterator found = files_.find(
      MountPointInfo(name, base::FilePath()));
  if (found == files_.end())
    return false;
  *path = found->path;
  return true;
}

bool IsolatedContext::Instance::IsSinglePathInstance() const {
  return IsSinglePathIsolatedFileSystem(type_);
}

//--------------------------------------------------------------------------

// static
IsolatedContext* IsolatedContext::GetInstance() {
  return g_isolated_context.Pointer();
}

// static
bool IsolatedContext::IsIsolatedType(FileSystemType type) {
  return type == kFileSystemTypeIsolated || type == kFileSystemTypeExternal;
}

std::string IsolatedContext::RegisterDraggedFileSystem(
    const FileInfoSet& files) {
  base::AutoLock locker(lock_);
  std::string filesystem_id = GetNewFileSystemId();
  instance_map_[filesystem_id] = new Instance(
      kFileSystemTypeDragged, files.fileset());
  return filesystem_id;
}

std::string IsolatedContext::RegisterFileSystemForPath(
    FileSystemType type,
    const base::FilePath& path_in,
    std::string* register_name) {
  base::FilePath path(path_in.NormalizePathSeparators());
  if (path.ReferencesParent() || !path.IsAbsolute())
    return std::string();
  std::string name;
  if (register_name && !register_name->empty()) {
    name = *register_name;
  } else {
    name = base::FilePath(GetRegisterNameForPath(path)).AsUTF8Unsafe();
    if (register_name)
      register_name->assign(name);
  }

  base::AutoLock locker(lock_);
  std::string filesystem_id = GetNewFileSystemId();
  instance_map_[filesystem_id] = new Instance(type, MountPointInfo(name, path),
                                              Instance::PLATFORM_PATH);
  path_to_id_map_[path].insert(filesystem_id);
  return filesystem_id;
}

std::string IsolatedContext::RegisterFileSystemForVirtualPath(
    FileSystemType type,
    const std::string& register_name,
    const base::FilePath& cracked_path_prefix) {
  base::AutoLock locker(lock_);
  base::FilePath path(cracked_path_prefix.NormalizePathSeparators());
  if (path.ReferencesParent())
    return std::string();
  std::string filesystem_id = GetNewFileSystemId();
  instance_map_[filesystem_id] = new Instance(
      type,
      MountPointInfo(register_name, cracked_path_prefix),
      Instance::VIRTUAL_PATH);
  path_to_id_map_[path].insert(filesystem_id);
  return filesystem_id;
}

bool IsolatedContext::HandlesFileSystemMountType(FileSystemType type) const {
  return type == kFileSystemTypeIsolated;
}

bool IsolatedContext::RevokeFileSystem(const std::string& filesystem_id) {
  base::AutoLock locker(lock_);
  return UnregisterFileSystem(filesystem_id);
}

bool IsolatedContext::GetRegisteredPath(
    const std::string& filesystem_id, base::FilePath* path) const {
  DCHECK(path);
  base::AutoLock locker(lock_);
  IDToInstance::const_iterator found = instance_map_.find(filesystem_id);
  if (found == instance_map_.end() || !found->second->IsSinglePathInstance())
    return false;
  *path = found->second->file_info().path;
  return true;
}

bool IsolatedContext::CrackVirtualPath(
    const base::FilePath& virtual_path,
    std::string* id_or_name,
    FileSystemType* type,
    base::FilePath* path,
    FileSystemMountOption* mount_option) const {
  DCHECK(id_or_name);
  DCHECK(path);

  // This should not contain any '..' references.
  if (virtual_path.ReferencesParent())
    return false;

  // Set the default mount option.
  *mount_option = FileSystemMountOption();

  // The virtual_path should comprise <id_or_name> and <relative_path> parts.
  std::vector<base::FilePath::StringType> components;
  virtual_path.GetComponents(&components);
  if (components.size() < 1)
    return false;
  std::vector<base::FilePath::StringType>::iterator component_iter =
      components.begin();
  std::string fsid = base::FilePath(*component_iter++).MaybeAsASCII();
  if (fsid.empty())
    return false;

  base::FilePath cracked_path;
  {
    base::AutoLock locker(lock_);
    IDToInstance::const_iterator found_instance = instance_map_.find(fsid);
    if (found_instance == instance_map_.end())
      return false;
    *id_or_name = fsid;
    const Instance* instance = found_instance->second;
    if (type)
      *type = instance->type();

    if (component_iter == components.end()) {
      // The virtual root case.
      path->clear();
      return true;
    }

    // *component_iter should be a name of the registered path.
    std::string name = base::FilePath(*component_iter++).AsUTF8Unsafe();
    if (!instance->ResolvePathForName(name, &cracked_path))
      return false;
  }

  for (; component_iter != components.end(); ++component_iter)
    cracked_path = cracked_path.Append(*component_iter);
  *path = cracked_path;
  return true;
}

FileSystemURL IsolatedContext::CrackURL(const GURL& url) const {
  FileSystemURL filesystem_url = FileSystemURL(url);
  if (!filesystem_url.is_valid())
    return FileSystemURL();
  return CrackFileSystemURL(filesystem_url);
}

FileSystemURL IsolatedContext::CreateCrackedFileSystemURL(
    const GURL& origin,
    FileSystemType type,
    const base::FilePath& path) const {
  return CrackFileSystemURL(FileSystemURL(origin, type, path));
}

void IsolatedContext::RevokeFileSystemByPath(const base::FilePath& path_in) {
  base::AutoLock locker(lock_);
  base::FilePath path(path_in.NormalizePathSeparators());
  PathToID::iterator ids_iter = path_to_id_map_.find(path);
  if (ids_iter == path_to_id_map_.end())
    return;
  std::set<std::string>& ids = ids_iter->second;
  for (std::set<std::string>::iterator iter = ids.begin();
       iter != ids.end(); ++iter) {
    IDToInstance::iterator found = instance_map_.find(*iter);
    if (found != instance_map_.end()) {
      delete found->second;
      instance_map_.erase(found);
    }
  }
  path_to_id_map_.erase(ids_iter);
}

void IsolatedContext::AddReference(const std::string& filesystem_id) {
  base::AutoLock locker(lock_);
  DCHECK(instance_map_.find(filesystem_id) != instance_map_.end());
  instance_map_[filesystem_id]->AddRef();
}

void IsolatedContext::RemoveReference(const std::string& filesystem_id) {
  base::AutoLock locker(lock_);
  // This could get called for non-existent filesystem if it has been
  // already deleted by RevokeFileSystemByPath.
  IDToInstance::iterator found = instance_map_.find(filesystem_id);
  if (found == instance_map_.end())
    return;
  Instance* instance = found->second;
  DCHECK_GT(instance->ref_counts(), 0);
  instance->RemoveRef();
  if (instance->ref_counts() == 0) {
    bool deleted = UnregisterFileSystem(filesystem_id);
    DCHECK(deleted);
  }
}

bool IsolatedContext::GetDraggedFileInfo(
    const std::string& filesystem_id,
    std::vector<MountPointInfo>* files) const {
  DCHECK(files);
  base::AutoLock locker(lock_);
  IDToInstance::const_iterator found = instance_map_.find(filesystem_id);
  if (found == instance_map_.end() ||
      found->second->type() != kFileSystemTypeDragged)
    return false;
  files->assign(found->second->files().begin(),
                found->second->files().end());
  return true;
}

base::FilePath IsolatedContext::CreateVirtualRootPath(
    const std::string& filesystem_id) const {
  return base::FilePath().AppendASCII(filesystem_id);
}

IsolatedContext::IsolatedContext() {
}

IsolatedContext::~IsolatedContext() {
  STLDeleteContainerPairSecondPointers(instance_map_.begin(),
                                       instance_map_.end());
}

FileSystemURL IsolatedContext::CrackFileSystemURL(
    const FileSystemURL& url) const {
  if (!HandlesFileSystemMountType(url.type()))
    return FileSystemURL();

  std::string mount_name;
  FileSystemType cracked_type;
  base::FilePath cracked_path;
  FileSystemMountOption cracked_mount_option;
  if (!CrackVirtualPath(url.path(), &mount_name, &cracked_type,
                        &cracked_path, &cracked_mount_option)) {
    return FileSystemURL();
  }

  return FileSystemURL(
      url.origin(), url.mount_type(), url.virtual_path(),
      !url.filesystem_id().empty() ? url.filesystem_id() : mount_name,
      cracked_type, cracked_path, mount_name, cracked_mount_option);
}

bool IsolatedContext::UnregisterFileSystem(const std::string& filesystem_id) {
  lock_.AssertAcquired();
  IDToInstance::iterator found = instance_map_.find(filesystem_id);
  if (found == instance_map_.end())
    return false;
  Instance* instance = found->second;
  if (instance->IsSinglePathInstance()) {
    PathToID::iterator ids_iter = path_to_id_map_.find(
        instance->file_info().path);
    DCHECK(ids_iter != path_to_id_map_.end());
    ids_iter->second.erase(filesystem_id);
    if (ids_iter->second.empty())
      path_to_id_map_.erase(ids_iter);
  }
  delete found->second;
  instance_map_.erase(found);
  return true;
}

std::string IsolatedContext::GetNewFileSystemId() const {
  // Returns an arbitrary random string which must be unique in the map.
  lock_.AssertAcquired();
  uint32 random_data[4];
  std::string id;
  do {
    base::RandBytes(random_data, sizeof(random_data));
    id = base::HexEncode(random_data, sizeof(random_data));
  } while (instance_map_.find(id) != instance_map_.end());
  return id;
}

}  // namespace fileapi