Synchronizing shared resources with TMonitor
TMonitor
is a record used to synchronize threads. Just to be clear, we are talking about System.TMonitor
, not Vcl.Forms.TMonitor
.
Since Delphi 2009, the TObject
instance size has been doubled to make room for an additional 4 bytes. What are these 4 bytes for? They provide TMonitor
support!
Now, every TObject
descendant can be used as a lock. The type that allows this is the System.TMonitor
record, which implements a generic Monitor synchronization structure.
Getting ready
In this recipe, you'll face one of the classic multithreading problems—concurrent access to a shared file. Specifically, you'll have a lot of threads writing some information on a file—the same file—and all the threads have to be synchronized for this. Otherwise, the file will not be accessible due to locking, which will cause exceptions in your program code. This problem can be solved in a lot of ways, but TMonitor
offers the simplest solution. Let's start.
How to do it…
Follow these...