Blinker

implement lock name file
Parent 39461e8
Stefan Schuermans

Stefan Schuermans commited on 2019-08-13 19:35:46
Showing 2 changed files, with 173 additions and 0 deletions.

src/common/LockNameFile.cpp
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+/* Blinker
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+   Copyright 2011-2019 Stefan Schuermans <stefan@blinkenarea.org>
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+   Copyleft GNU public license - http://www.gnu.org/copyleft/gpl.html
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+   a blinkenarea.org project */
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+
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+#include "Lock.h"
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+#include "LockMgr.h"
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+#include "LockNameFile.h"
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+#include "NameFile.h"
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+
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+namespace Blinker {
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+
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+/**
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+ * @brief constructor
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+ * @param[in] file basic file object to treat as lock name file
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+ * @param[in] lockMgr lock manager
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+ */
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+LockNameFile::LockNameFile(const File &file, LockMgr &lockMgr):
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+  m_nameFile(file),
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+  m_lockMgr(lockMgr),
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+  m_refLock(nullptr),
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+  m_takenLock(nullptr)
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+{
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+  update();
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+}
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+
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+/// destructor
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+LockNameFile::~LockNameFile()
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+{
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+  release();
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+}
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+
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+/// update lock name if file has been modified
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+void LockNameFile::updateIfModified()
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+{
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+  if (m_nameFile.checkModified()) {
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+    update();
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+  }
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+}
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+
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+/**
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+ * @brief check if lock is free,
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+ *        i.e., no lock configured (i.e. no lock file),
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+ *        lock not locked or taken by this object
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+ * @return whether lock is free
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+ */
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+bool LockNameFile::isfree() const
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+{
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+  return m_takenLock != nullptr ||
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+         m_refLock == nullptr ||
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+         ! m_refLock->islocked();
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+}
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+
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+/**
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+ * @brief take the lock,
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+ *        success if no lock configured (i.e. no lock file),
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+ *        lock was not locked and could be taken by this object
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+ *        or lock was already taken by this object
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+ * @return whether lock could be taken
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+ */
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+bool LockNameFile::take()
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+{
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+  if (m_takenLock != nullptr) {
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+    return true; // already taken
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+  }
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+  if (m_refLock == nullptr) {
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+    return true; // no lock configured
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+  }
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+  if (! m_refLock->trylock()) {
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+    return false; // did not get lock
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+  }
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+  // remember pointer to taken lock
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+  // (important if lock name changes while taken)
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+  m_takenLock = m_refLock;
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+  return true; // lock taken
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+}
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+
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+/// release taken lock
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+void LockNameFile::release()
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+{
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+  if (m_takenLock != nullptr) {
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+    m_takenLock->unlock();
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+    m_takenLock = nullptr;
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+  }
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+}
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+
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+/// update pointer to referenced lock based on name file contents
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+void LockNameFile::update()
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+{
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+  m_nameFile.update();
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+  m_refLock = nullptr; // forget old referenced lock
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+  if (! m_nameFile.m_valid) {
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+    return; // no lock referenced
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+  }
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+  // get new referenced lock
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+  m_refLock = &m_lockMgr.getLock(m_nameFile.m_obj.m_str);
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+}
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+
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+} // namespace Blinker
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+
src/common/LockNameFile.h
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+/* Blinker
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+   Copyright 2011-2019 Stefan Schuermans <stefan@blinkenarea.org>
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+   Copyleft GNU public license - http://www.gnu.org/copyleft/gpl.html
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+   a blinkenarea.org project */
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+
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+#ifndef BLINKER_LOCKNAMEFILE_H
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+#define BLINKER_LOCKNAMEFILE_H
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+
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+#include "LockMgr.h"
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+#include "NameFile.h"
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+
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+namespace Blinker {
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+
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+/// file containting the name of a lock
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+class LockNameFile
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+{
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+public:
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+  /**
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+   * @brief constructor
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+   * @param[in] file basic file object to treat as lock name file
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+   * @param[in] lockMgr lock manager
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+   */
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+  LockNameFile(const File &file, LockMgr &lockMgr);
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+
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+  /// destructor
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+  ~LockNameFile();
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+
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+private:
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+  /// copy constructor disabled
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+  LockNameFile(const LockNameFile &);
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+
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+  /// assignment operator disabled
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+  const LockNameFile & operator=(const LockNameFile &);
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+
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+public:
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+  /// update lock name if file has been modified
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+  void updateIfModified();
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+
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+  /**
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+   * @brief check if lock is free,
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+   *        i.e., no lock configured (i.e. no lock file),
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+   *        lock not locked or taken by this object
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+   * @return whether lock is free
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+   */
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+  bool isfree() const;
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+
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+  /**
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+   * @brief take the lock,
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+   *        success if no lock configured (i.e. no lock file),
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+   *        lock was not locked and could be taken by this object
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+   *        or lock was already taken by this object
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+   * @return whether lock could be taken
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+   */
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+  bool take();
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+
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+  /// release taken lock
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+  void release();
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+
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+protected:
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+  /// update pointer to referenced lock based on name file contents
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+  void update();
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+
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+public:
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+  NameFile m_nameFile; ///< file containing lock name
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+  LockMgr &m_lockMgr; ///< reference to lock manager
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+  class Lock *m_refLock; ///< pointer to re referenced lock (if any) or nullptr
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+  class Lock *m_takenLock; ///< pointer to taken lock (if any) or nullptr
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+}; // class LockNameFile
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+
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+} // namespace Blinker
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+
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+#endif // #ifndef BLINKER_LOCKNAMEFILE_H
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+
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