net/disk_cache/simple/simple_synchronous_entry.h

// 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.

#ifndef NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_
#define NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_

#include <algorithm>
#include <string>
#include <utility>
#include <vector>

#include "base/files/file_path.h"
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_ptr.h"
#include "base/platform_file.h"
#include "base/time/time.h"
#include "net/base/cache_type.h"
#include "net/base/net_export.h"
#include "net/disk_cache/simple/simple_entry_format.h"

namespace net {
class GrowableIOBuffer;
class IOBuffer;
}

namespace disk_cache {

class SimpleSynchronousEntry;

// This class handles the passing of data about the entry between
// SimpleEntryImplementation and SimpleSynchronousEntry and the computation of
// file offsets based on the data size for all streams.
class NET_EXPORT_PRIVATE SimpleEntryStat {
 public:
  SimpleEntryStat(base::Time last_used,
                  base::Time last_modified,
                  const int32 data_size[]);

  int GetOffsetInFile(const std::string& key,
                      int offset,
                      int stream_index) const;
  int GetEOFOffsetInFile(const std::string& key, int stream_index) const;
  int GetLastEOFOffsetInFile(const std::string& key, int file_index) const;
  int GetFileSize(const std::string& key, int file_index) const;

  base::Time last_used() const { return last_used_; }
  base::Time last_modified() const { return last_modified_; }
  void set_last_used(base::Time last_used) { last_used_ = last_used; }
  void set_last_modified(base::Time last_modified) {
    last_modified_ = last_modified;
  }

  int32 data_size(int stream_index) const { return data_size_[stream_index]; }
  void set_data_size(int stream_index, int data_size) {
    data_size_[stream_index] = data_size;
  }

 private:
  base::Time last_used_;
  base::Time last_modified_;
  int32 data_size_[kSimpleEntryStreamCount];
};

struct SimpleEntryCreationResults {
  explicit SimpleEntryCreationResults(SimpleEntryStat entry_stat);
  ~SimpleEntryCreationResults();

  SimpleSynchronousEntry* sync_entry;
  scoped_refptr<net::GrowableIOBuffer> stream_0_data;
  SimpleEntryStat entry_stat;
  uint32 stream_0_crc32;
  int result;
};

// Worker thread interface to the very simple cache. This interface is not
// thread safe, and callers must ensure that it is only ever accessed from
// a single thread between synchronization points.
class SimpleSynchronousEntry {
 public:
  struct CRCRecord {
    CRCRecord();
    CRCRecord(int index_p, bool has_crc32_p, uint32 data_crc32_p);

    int index;
    bool has_crc32;
    uint32 data_crc32;
  };

  struct EntryOperationData {
    EntryOperationData(int index_p, int offset_p, int buf_len_p);
    EntryOperationData(int index_p,
                       int offset_p,
                       int buf_len_p,
                       bool truncate_p,
                       bool doomed_p);

    int index;
    int offset;
    int buf_len;
    bool truncate;
    bool doomed;
  };

  static void OpenEntry(net::CacheType cache_type,
                        const base::FilePath& path,
                        uint64 entry_hash,
                        bool had_index,
                        SimpleEntryCreationResults* out_results);

  static void CreateEntry(net::CacheType cache_type,
                          const base::FilePath& path,
                          const std::string& key,
                          uint64 entry_hash,
                          bool had_index,
                          SimpleEntryCreationResults* out_results);

  // Deletes an entry from the file system without affecting the state of the
  // corresponding instance, if any (allowing operations to continue to be
  // executed through that instance). Returns a net error code.
  static int DoomEntry(const base::FilePath& path,
                       uint64 entry_hash);

  // Like |DoomEntry()| above. Deletes all entries corresponding to the
  // |key_hashes|. Succeeds only when all entries are deleted. Returns a net
  // error code.
  static int DoomEntrySet(const std::vector<uint64>* key_hashes,
                          const base::FilePath& path);

  // N.B. ReadData(), WriteData(), CheckEOFRecord() and Close() may block on IO.
  void ReadData(const EntryOperationData& in_entry_op,
                net::IOBuffer* out_buf,
                uint32* out_crc32,
                SimpleEntryStat* entry_stat,
                int* out_result) const;
  void WriteData(const EntryOperationData& in_entry_op,
                 net::IOBuffer* in_buf,
                 SimpleEntryStat* out_entry_stat,
                 int* out_result);
  void CheckEOFRecord(int index,
                      const SimpleEntryStat& entry_stat,
                      uint32 expected_crc32,
                      int* out_result) const;

  // Close all streams, and add write EOF records to streams indicated by the
  // CRCRecord entries in |crc32s_to_write|.
  void Close(const SimpleEntryStat& entry_stat,
             scoped_ptr<std::vector<CRCRecord> > crc32s_to_write,
             net::GrowableIOBuffer* stream_0_data);

  const base::FilePath& path() const { return path_; }
  std::string key() const { return key_; }

 private:
  enum CreateEntryResult {
    CREATE_ENTRY_SUCCESS = 0,
    CREATE_ENTRY_PLATFORM_FILE_ERROR = 1,
    CREATE_ENTRY_CANT_WRITE_HEADER = 2,
    CREATE_ENTRY_CANT_WRITE_KEY = 3,
    CREATE_ENTRY_MAX = 4,
  };

  enum FileRequired {
    FILE_NOT_REQUIRED,
    FILE_REQUIRED
  };

  SimpleSynchronousEntry(
      net::CacheType cache_type,
      const base::FilePath& path,
      const std::string& key,
      uint64 entry_hash);

  // Like Entry, the SimpleSynchronousEntry self releases when Close() is
  // called.
  ~SimpleSynchronousEntry();

  // Tries to open one of the cache entry files.  Succeeds if the open succeeds
  // or if the file was not found and is allowed to be omitted if the
  // corresponding stream is empty.
  bool MaybeOpenFile(int file_index,
                     base::PlatformFileError* out_error);
  // Creates one of the cache entry files if necessary.  If the file is allowed
  // to be omitted if the corresponding stream is empty, and if |file_required|
  // is FILE_NOT_REQUIRED, then the file is not created; otherwise, it is.
  bool MaybeCreateFile(int file_index,
                       FileRequired file_required,
                       base::PlatformFileError* out_error);
  bool OpenFiles(bool had_index,
                 SimpleEntryStat* out_entry_stat);
  bool CreateFiles(bool had_index,
                   SimpleEntryStat* out_entry_stat);
  void CloseFile(int index);
  void CloseFiles();

  // Returns a net error, i.e. net::OK on success.  |had_index| is passed
  // from the main entry for metrics purposes, and is true if the index was
  // initialized when the open operation began.
  int InitializeForOpen(bool had_index,
                        SimpleEntryStat* out_entry_stat,
                        scoped_refptr<net::GrowableIOBuffer>* stream_0_data,
                        uint32* out_stream_0_crc32);

  // Writes the header and key to a newly-created stream file.  |index| is the
  // index of the stream.  Returns true on success; returns false and sets
  // |*out_result| on failure.
  bool InitializeCreatedFile(int index, CreateEntryResult* out_result);

  // Returns a net error, including net::OK on success and net::FILE_EXISTS
  // when the entry already exists.  |had_index| is passed from the main entry
  // for metrics purposes, and is true if the index was initialized when the
  // create operation began.
  int InitializeForCreate(bool had_index, SimpleEntryStat* out_entry_stat);

  // Allocates and fills a buffer with stream 0 data in |stream_0_data|, then
  // checks its crc32.
  int ReadAndValidateStream0(
      int total_data_size,
      SimpleEntryStat* out_entry_stat,
      scoped_refptr<net::GrowableIOBuffer>* stream_0_data,
      uint32* out_stream_0_crc32) const;

  int GetEOFRecordData(int index,
                       const SimpleEntryStat& entry_stat,
                       bool* out_has_crc32,
                       uint32* out_crc32,
                       int* out_data_size) const;
  void Doom() const;

  static bool DeleteFileForEntryHash(const base::FilePath& path,
                                     uint64 entry_hash,
                                     int file_index);
  static bool DeleteFilesForEntryHash(const base::FilePath& path,
                                      uint64 entry_hash);

  void RecordSyncCreateResult(CreateEntryResult result, bool had_index);

  base::FilePath GetFilenameFromFileIndex(int file_index);

  const net::CacheType cache_type_;
  const base::FilePath path_;
  const uint64 entry_hash_;
  std::string key_;

  bool have_open_files_;
  bool initialized_;

  base::PlatformFile files_[kSimpleEntryFileCount];

  // True if the corresponding stream is empty and therefore no on-disk file
  // was created to store it.
  bool empty_file_omitted_[kSimpleEntryFileCount];
};

}  // namespace disk_cache

#endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_