Mapped File Class

-->

CMappedFile was created after some users complained that my apps were storing too much data in the Registry. I needed a way to preserve the multilevel data heirarchy that the Registry provides, but I needed to do it in external files. In addition, I wanted some protection from curious eyes.

CMappedFile is essentially a CMap of COleVariants that will serialize itself to and from files. It supports long, bool, LPCSTR and double. But, because you can cast just about any basic type into a long, you can store just about anything. Plus, it should be fairly simple to extend this class to hold anything a COleVariant can hold.

To provide key support, three functions, SetBaseKey, SetSubKey and MoveUp are provided.

  • SetBaseKey(key) allows you to set the root key for all subsequent read and write operations.
  • SetSubKey(subKey) moves the current key "down" to the specified subkey.
  • MoveUp() moves the current key "up" to the parent key.

The following example write five values to a CMappedFile, in two different keys, and writes the file. Then, it reads the file back into a different CMappedFile and verifies the results. Pretty simple.

// stupid data values
double pi = 3.14159;
CString hi = "Hi There!";
long fiftyFive = 55;
bool thisWorks = true;
bool thisDoesNotWork = false;

CMappedFile mf;

// start off with a key called "Root"
mf.SetBaseKey("Root");

// Root\Pi : 3.14159
mf.Set("Pi", pi);			

// Root\Hi : Hi There!
mf.Set("Hi", hi);			

// move down a subkey
mf.SetSubKey("Subkey");

// Root\Subkey\Success : true
mf.Set("Success", thisWorks);	

// Root\Subkey\55 : 55
mf.Set("55", fiftyFive);	

mf.MoveUp();
// Root\Failure : false
mf.Set("Failure", thisDoesNotWork);

// dump this to the debug output window
mf.Dump();

// save it to a file
mf.Write("test.mf");

// "test.mf" now holds the following values : 
// Root\Pi : 3.14159
// Root\Hi : Hi There!
// Root\Subkey\55 : 55
// Root\Subkey\Success : true
// Root\Failure : false

// read it back, to a different CMappedFile, to be safe
CMappedFile mf2;
mf2.Read("test.mf");

mf2.SetBaseKey("Root");
ASSERT(mf2.Get("Hi", "Bye") == hi);
ASSERT(mf2.Get("Pi", -1.0) == pi);

mf2.SetSubKey("Subkey");
ASSERT(mf2.Get("55", (long)-1) == fiftyFive);
ASSERT(mf2.Get("Success", false) == true);

mf2.MoveUp();
ASSERT(mf2.Get("Failure", true) == false);

Download source - 4 KB



Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • As mobile devices have pushed their way into the enterprise, they have brought cloud apps along with them. This app explosion means account passwords are multiplying, which exposes corporate data and leads to help desk calls from frustrated users. This paper will discover how IT can improve user productivity, gain visibility and control over SaaS and mobile apps, and stop password sprawl. Download this white paper to learn: How you can leverage your existing AD to manage app access. Key capabilities to …

  • Packaged application development teams frequently operate with limited testing environments due to time and labor constraints. By virtualizing the entire application stack, packaged application development teams can deliver business results faster, at higher quality, and with lower risk.

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds