Search code examples
vbscriptregistrywmi

Setting Size of String Buffer When Accessing Windows Registry

I'm working on a VBScript web application that has a newly-introduced requirement to talk to the registry to pull connection string information instead of using hard-coded strings. I'm doing performance profiling because of the overhead this will introduce, and noticed in Process Monitor that reading the value returns two BUFFER OVERFLOW results before finally returning a success.

Registry Work

Looking online, Mark Russinovich posted about this topic a few years back, indicating that since the size of the registry entry isn't known, a default buffer of 144 bytes is used. Since there are two buffer overflow responses, the amount of time taken by the entire call is approximately doubled (and yes, I realize the difference is 40 microseconds, but with 1,000 or more page hits per second, I'm willing to invest some time in optimization).

My question is this: is there a way to tell WMI what the size of the registry value is before it tries to get it? Here's a sample of the code I'm using to access the registry:

svComputer = "." ' Local machine is simply "."
ivHKey = &H80000002 ' HKEY_LOCAL_MACHINE = &H80000002 (from WinReg.h)
svRegPath = "SOFTWARE\Path\To\My\Values"

Set oRegistry = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" & svComputer & "\root\default:StdRegProv")
oRegistry.GetStringValue ivHKey, svRegPath, "Value", svValue
Solution

  • In VBScript strings are strings. They are however long they need to be. You don't pre-define their length. Also, if performance is that much of an issue for you, you should consider using a compiled instead of an interpreted language (or a cache for values you read before).