improved lock file handling (#50)

- Feature: `zen down`
  - --`data-dir` to specify a data directory to deduce which zen instance to bring down
- Feature: `zen attach`
  - --`data-dir` to specify a data directory to deduce which zen instance to attach to222
  
- Feature: `zen status`
  -  --`port` filter running zen instances based on port
  - --`data-dir` filter running zen instances based on information in the data directory

- Improvement: Trying to load a compact binary object from an empty file no longer causes access violation

1 files changed, 19 insertions, 2 deletions

diff --git a/src/zenutil/include/zenutil/zenserverprocess.h b/src/zenutil/include/zenutil/zenserverprocess.h
index 720b30766..af5125471 100644
--- a/src/zenutil/include/zenutil/zenserverprocess.h
+++ b/src/zenutil/include/zenutil/zenserverprocess.h
@@ -15,6 +15,8 @@
 
 namespace zen {
 
+class CbObject;
+
 /** Zen Server Environment configuration
 
 	This class allows a user to configure where a spawned server should place any
@@ -171,10 +173,11 @@ public:
 
 	void						  Initialize();
 	[[nodiscard]] bool			  InitializeReadOnly();
-	[[nodiscard]] ZenServerEntry* Lookup(int DesiredListenPort);
+	[[nodiscard]] ZenServerEntry* Lookup(int DesiredListenPort) const;
+	[[nodiscard]] ZenServerEntry* LookupByEffectivePort(int Port) const;
 	ZenServerEntry*				  Register(int DesiredListenPort);
 	void						  Sweep();
-	void						  Snapshot(std::function<void(const ZenServerEntry&)>&& Callback);
+	void						  Snapshot(std::function<void(const ZenServerEntry&)>&& Callback) const;
 	inline bool					  IsReadOnly() const { return m_IsReadOnly; }
 
 private:
@@ -185,4 +188,18 @@ private:
 	bool			m_IsReadOnly	= true;
 };
 
+struct LockFileInfo
+{
+	int32_t				  Pid;
+	Oid					  SessionId;
+	uint16_t			  EffectiveListenPort;
+	bool				  Ready;
+	std::filesystem::path DataDir;
+	std::filesystem::path ExecutablePath;
+};
+
+CbObject	 MakeLockFilePayload(const LockFileInfo& Info);
+LockFileInfo ReadLockFilePayload(const CbObject& Payload);
+bool		 ValidateLockFileInfo(const LockFileInfo& Info, std::string& OutReason);
+
 }  // namespace zen