From 9a862bc75ae56ec0c0be6e91db343b63b0087d08 Mon Sep 17 00:00:00 2001
From: Paul Beckingham <paul@beckingham.net>
Date: Sun, 14 Aug 2011 11:54:53 -0400
Subject: [PATCH] File - locking

- Made locking an integral part of the File object, so that a client
  may now call File::lock multiple times with no effect beyond the first
  call.  This simplifies situations like the 'cal' command that must scan
  for recurrence changes, modify tasks, then optionally run a second
  report, all without locking issues.
---
 src/File.cpp | 20 +++++++++++++++++++-
 src/File.h   |  1 +
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/File.cpp b/src/File.cpp
index 7a818f5dc..884742555 100644
--- a/src/File.cpp
+++ b/src/File.cpp
@@ -42,6 +42,7 @@ File::File ()
 : Path::Path ()
 , fh (NULL)
 , h (-1)
+, locked (false)
 {
 }
 
@@ -50,6 +51,7 @@ File::File (const Path& other)
 : Path::Path (other)
 , fh (NULL)
 , h (-1)
+, locked (false)
 {
 }
 
@@ -58,6 +60,7 @@ File::File (const File& other)
 : Path::Path (other)
 , fh (NULL)
 , h (-1)
+, locked (false)
 {
 }
 
@@ -66,6 +69,7 @@ File::File (const std::string& in)
 : Path::Path (in)
 , fh (NULL)
 , h (-1)
+, locked (false)
 {
 }
 
@@ -82,6 +86,7 @@ File& File::operator= (const File& other)
   if (this != &other)
     Path::operator= (other);
 
+  locked = false;
   return *this;
 }
 
@@ -117,6 +122,7 @@ bool File::open ()
     if (fh)
     {
       h = fileno (fh);
+      locked = false;
       return true;
     }
   }
@@ -138,6 +144,7 @@ void File::close ()
     fclose (fh);
     fh = NULL;
     h = -1;
+    locked = false;
   }
 }
 
@@ -152,17 +159,28 @@ bool File::lock ()
       ;
 
     if (retry <= 3)
+    {
+      locked = true;
       return true;
+    }
   }
 
+  locked = false;
   return false;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 bool File::waitForLock ()
 {
+  if (locked)
+    return true;
+
   if (fh && h != -1)
-    return flock (h, LOCK_EX) == 0 ? true : false;
+    if (flock (h, LOCK_EX) == 0)
+    {
+      locked = true;
+      return true;
+    }
 
   return false;
 }
diff --git a/src/File.h b/src/File.h
index 2c5ccc292..5a60bbd8f 100644
--- a/src/File.h
+++ b/src/File.h
@@ -82,6 +82,7 @@ public:
 private:
   FILE* fh;
   int   h;
+  bool  locked;
 };
 
 #endif