Tips, Hints and Documentation Posts for SamplingProfiler and other Delphi Tools
I’ve now been running the DWScript Sample Web Server for 8 months in a metered host (Ikoula’s 1€/month VM), so it’s time for a more formal introduction article.
It served web pages and JSON dynamically generated by DWScript, using an SQLite database for storage. It ran on a Windows 2008 R2 Standard installation, minimized so that OS+Server stayed around 256 MB RAM.
This article deals with reference-counted String theory, it doesn’t relate to String Theory, unification of gravity with other quantum forces or canadian fashion.
Instead it deals with leveraging reference-counted String data to unify them and minimize memory usage requirements.
edit: as pointed in the comments, the usual terminology for that optimization is interning, which is a misnomer derived from an old LISP function “intern” which related to internal/external and packages.
In this new episode of the TMonitor saga is a comparison of its locking features vs TRTLCriticalSection, aka the OS-supported critical section mechanism. Is it fair? is it fast?
Fairness means that if you have several threads attempting to lock the same resources, they’ll all get a chance and none of them gets the lion’s share. In other words, that there are no race conditions.
Speed is obvious, it’s about the overhead the locking mechanism incurs.
Edit 2013-08-24: looks like the issue discussed here should be resolved in XE5, cf Monitoring the Monitor by Allen Bauer.
One of the “novelties” of the NextGen Delphi compiler is immutable strings, which I find quite puzzling, for lack of a better word, given that Delphi already had reference-counted copy-on-write strings, and the NextGen compiler uses reference-counted strings.
I always considered that Delphi’s String type was one of its remaining strong points, being a high-level abstraction (higher than Java’s or .Net’s String/StringBuilder dichotomy) with excellent low-level performance (on par with C/C++ character arrays).
From the recent discussions, it appears many don’t know what makes/made Delphi String so special, so here is a quick summary.
Visual Basic in its various incarnations and off-springs has super-powers when it comes to OLE Automation, aka late-bound COM through IDispatch.
Where do they come from?
DWScript COM Connector has just received a spring cleanup, as it had grown a bit mouldy over the last years. The COM Connector optionally gives scripts direct access to ActiveX and COM objects.
As part of the cleanup, it now support IEnumVARIANT and ComVariantArray can now be enumerated as well with “for in“.
This is a belated followup to the L-System Fiddle series from last year (more like a forgotten article), which ended with a Pascal-based HTML5 app being used to generate fractals and publish them to imgur.
In Delphi you can initialize a dynamic array in two ways, either manually or via the Create magic constructor
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This is a simple trick that can be handy to cleanup or simplify Boolean expressions, and is always good to have in your code-writing toolchest: De Morgan’s laws.
These two laws allow to apply a negation to an and or or expression:
After having survived the Mayan apocalypse and just before the year ends, and the US economy falls from the fiscal cliff into the pit of recession, here is a quick look at thirteen features of DWScript, so you don’t come into 2013 unaware 🙂