Adding crash utilities to chromecast/crash.

chromecast/crash/linux/synchronized_minidump_manager.h

+// Copyright 2015 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 CHROMECAST_CRASH_LINUX_SYNCHRONIZED_MINIDUMP_MANAGER_H_
+#define CHROMECAST_CRASH_LINUX_SYNCHRONIZED_MINIDUMP_MANAGER_H_
+
+#include <string>
+
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/memory/scoped_vector.h"
+
+namespace chromecast {
+
+class DumpInfo;
+
+// Abstract base class for mutually-exclusive minidump handling. Ensures
+// synchronized access among instances of this class to the minidumps directory
+// using a file lock. The "lockfile" also holds serialized metadata about each
+// of the minidumps in the directory. Derived classes should not access the
+// lockfile directly. Instead, use protected methods to query and modify the
+// metadata, but only within the implementation of DoWork().
+class SynchronizedMinidumpManager {
+ public:
+  virtual ~SynchronizedMinidumpManager();
+
+  // Returns whether this object's file locking method is nonblocking or not.
+  bool non_blocking() { return non_blocking_; }
+
+  // Sets the file locking mechansim to be nonblocking or not.
+  void set_non_blocking(bool non_blocking) { non_blocking_ = non_blocking; }
+
+ protected:
+  SynchronizedMinidumpManager();
+
+  // Acquires the lock, calls DoWork(), then releases the lock when DoWork()
+  // returns. Derived classes should expose a method which calls this. Returns
+  // the status of DoWork(), or -1 if the lock was not successfully acquired.
+  int AcquireLockAndDoWork();
+
+  // Derived classes must implement this method. It will be called from
+  // DoWorkLocked after the lock has been successfully acquired. The lockfile
+  // shall be accessed and mutated only through the methods below. All other
+  // files shall be managed as needed by the derived class.
+  virtual int DoWork() = 0;
+
+  // Access the container holding all the metadata for the dumps. Note that
+  // the child class must only call this inside DoWork(). This is lazy. If the
+  // lockfile has not been parsed yet, it will be parsed when this is called.
+  const ScopedVector<DumpInfo>& GetDumpMetadata();
+
+  // Serialize |dump_info| and append it to the lockfile. Note that the child
+  // class must only call this inside DoWork(). This should be the only method
+  // used to write to the lockfile. Only call this if the minidump has been
+  // generated in the minidumps directory successfully. Returns 0 on success,
+  // -1 otherwise.
+  int AddEntryToLockFile(const DumpInfo& dump_info);
+
+  // Remove the lockfile entry at |index| in the container returned by
+  // GetDumpMetadata(). If the index is invalid or an IO error occurred, returns
+  // -1. Otherwise returns 0. When this function returns, both the in-memory
+  // containter returned by GetDumpMetadata and the persistent lockfile will be
+  // current.
+  int RemoveEntryFromLockFile(int index);
+
+  // Get the number of un-uploaded dumps in the dump_path directory.
+  // If delete_all_dumps is true, also delete all these files, this is used to
+  // clean lingering dump files.
+  int GetNumDumps(bool delete_all_dumps);
+
+  // TODO(slan): Remove this accessor. All I/O on the lockfile in inherited
+  // classes should be done via GetDumpMetadata(), AddEntryToLockFile(), and
+  // RemoveEntryFromLockFile().
+  const std::string& lockfile_path() { return lockfile_path_; }
+
+  // If true, the flock on the lockfile will be nonblocking
+  bool non_blocking_;
+
+  // Cached path for the minidumps directory.
+  base::FilePath dump_path_;
+
+ private:
+  // Acquire the lock file. Blocks if another process holds it, or if called
+  // a second time by the same process. Returns the fd of the lockfile if
+  // successful, or -1 if failed.
+  int AcquireLockFile();
+
+  // Parse the lockfile, populating |dumps_| for descendants to use. Return -1
+  // if an error occurred. Otherwise, return 0. This must not be called unless
+  // |this| has acquired the lock.
+  int ParseLockFile();
+
+  // Release the lock file with the associated *fd*.
+  void ReleaseLockFile();
+
+  std::string lockfile_path_;
+  int lockfile_fd_;
+  scoped_ptr<ScopedVector<DumpInfo> > dump_metadata_;
+
+  DISALLOW_COPY_AND_ASSIGN(SynchronizedMinidumpManager);
+};
+
+}  // namespace chromecast
+
+#endif  // CHROMECAST_CRASH_LINUX_SYNCHRONIZED_MINIDUMP_MANAGER_H_