Add rotating log file stream.

webrtc/base/stream.h

Index: webrtc/base/stream.h
diff --git a/webrtc/base/stream.h b/webrtc/base/stream.h
index f67c704aa5155f8ed64cbc2cd2a32e4c6b376efd..030f831bcdd33fb6f29a44dcafd3539d2c742843 100644
--- a/webrtc/base/stream.h
+++ b/webrtc/base/stream.h
@@ -418,6 +418,151 @@ class FileStream : public StreamInterface {
   DISALLOW_COPY_AND_ASSIGN(FileStream);
 };
 
+// FileRotatingStream writes to a file in the directory specified in the

[jiayl2, 2015/07/20 23:27:06]

I think the declaration and impl are big enough to be put in its own files.

[tkchin_webrtc, 2015/07/21 20:39:13]

Done.

+// constructor. It rotates the files once the current file is full. The
+// individual file size and the number of files used is configurable in the
+// constructor. Open must be called before using this stream.
+class FileRotatingStream : public StreamInterface {
+ public:
+  // Use this constructor for reading a directory previously written to with
+  // this stream.
+  FileRotatingStream(const std::string& dir_path,
+                     const std::string& file_prefix);
+
+  // Use this constructor for writing to a directory. Files in the directory
+  // matching the prefix will be deleted on open.
+  FileRotatingStream(const std::string& dir_path,
+                     const std::string& file_prefix,
+                     size_t max_file_size,
+                     size_t num_files);
+
+  ~FileRotatingStream() override;
+
+  // StreamInterface methods.
+  StreamState GetState() const override;
+  StreamResult Read(void* buffer,
+                    size_t buffer_len,
+                    size_t* read,
+                    int* error) override;
+  StreamResult Write(const void* data,
+                     size_t data_len,
+                     size_t* written,
+                     int* error) override;
+  bool Flush() override;
+  void Close() override;
+
+  // Opens the appropriate file(s). Call this before using the stream.
+  bool Open();
+
+  // Disabling buffering causes writes to block until disk is updated. This is
+  // enabled by default for performance.
+  bool DisableBuffering();
+
+  // Returns the path used for the file at the i-th index. The file may or may
+  // not exist, this is just used for formatting. Index must be less than
+  // GetNumFiles().
+  std::string GetFilePath(size_t index) const;
+
+  // Returns the number of files that will used by this stream.
+  size_t GetNumFiles() { return file_names_.size(); }
+
+ protected:
+  size_t GetMaxFileSize() const { return max_file_size_; }
+
+  void SetMaxFileSize(size_t size) { max_file_size_ = size; }
+
+  size_t GetLastFileIndex() const { return last_file_index_; }
+
+  void SetLastFileIndex(size_t index) { last_file_index_ = index; }
+
+  virtual void OnRotation() {}
+
+ private:
+  enum Mode { kRead, kWrite };
+
+  FileRotatingStream(const std::string& dir_path,
+                     const std::string& file_prefix,
+                     size_t max_file_size,
+                     size_t num_files,
+                     Mode mode);
+
+  // Opens the file at the current file index.  Set |delete_existing| to true
+  // to also delete files that begin with the prefix.
+  bool Open(bool delete_existing);
+
+  // Rotates the files by creating a new current file, renaming the
+  // existing files, and deleting the oldest one. e.g.
+  // file_0 -> file_1
+  // file_1 -> file_2
+  // file_2 -> delete
+  // create new file_0
+  void RotateFiles();
+
+  // Returns a list of file names in the directory beginning with the prefix.
+  std::vector<std::string> GetFilesWithPrefix() const;
+  // Private version of GetFilePath.
+  std::string GetFilePath(size_t index, size_t num_files) const;
+
+  const std::string dir_path_;
+  const std::string file_prefix_;
+  const Mode mode_;
+
+  // FileStream is used to write to the current file.
+  scoped_ptr<FileStream> file_stream_;
+  // Convenience storage for file names so we don't generate them over and over.
+  std::vector<std::string> file_names_;
+  size_t max_file_size_;
+  size_t current_file_index_;
+  // The last file index indicates the index of the file that will be deleted
+  // first on rotation.
+  size_t last_file_index_;
+  // Number of bytes written to current file. We need this because with
+  // buffering the file size read from disk might not be accurate.
+  size_t current_bytes_written_;
+  bool disable_buffering_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileRotatingStream);
+};
+
+// MobileDeviceLogStream is meant to be used on mobile devices where we will
+// have limited disk space. Its purpose is to read and write logs up to a
+// maximum size. Once the maximum  size is exceeded, logs from the middle are
+// deleted whereas logs from the beginning and end are preserved. The reason for
+// this is because we anticipate that in WebRTC the beginning and end of the
+// logs are most useful for call diagnostics.
+//
+// This implementation simply writes to a single file until
+// |max_total_log_size| / 2 bytes are written to it, and subsequently writes to
+// a set of rotating files. We do this by inheriting FileRotatingStream and
+// setting the appropriate internal variables so that we don't delete the last
+// (earliest) file on rotate, and that that file's size is bigger.
+//
+// Open() must be called before using this stream.
+class MobileDeviceLogStream : public FileRotatingStream {

[jiayl2, 2015/07/20 23:27:06]

nit: this is useful not only for mobile devices, but almost everywhere since we
always have a limit on disk size or upload size.
I know it's hard to capture what it does in the name, so maybe something vague
on purpose, e.g. PriorityFileRotatingStream (since the start and the end are
given higher priority), or CallSessionRotatingStream, ...

Same comment applies to the log sink class.

[tkchin_webrtc, 2015/07/21 20:39:13]

Done.

+ public:
+  // Use this constructor for reading a directory previously written to with
+  // this stream.
+  MobileDeviceLogStream(const std::string& dir_path);
+  // Use this constructor for writing to a directory. Files in the directory
+  // matching what's used by the stream will be deleted.
+  MobileDeviceLogStream(const std::string& dir_path, size_t max_total_log_size);
+  ~MobileDeviceLogStream() override {}
+
+ protected:
+  void OnRotation() override;
+
+ private:
+  static size_t GetRotatingLogSize(size_t max_total_log_size);
+  static size_t GetNumRotatingLogFiles(size_t max_total_log_size);
+  static const char* kLogPrefix;
+  static const size_t kRotatingLogFileDefaultSize;
+
+  const size_t max_total_log_size_;
+  size_t num_rotations_;
+
+  DISALLOW_COPY_AND_ASSIGN(MobileDeviceLogStream);
+};
+
 // A stream that caps the output at a certain size, dropping content from the
 // middle of the logical stream and maintaining equal parts of the start/end of
 // the logical stream.