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  • Your email address will not be published.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

  • Salesforce has been recognized by Gartner as a leader in this report for three years in a row. This graphic was published by Gartner, Inc. as part of a larger research document and should be evaluated in the context of the entire document. The Gartner document is available upon request from Salesforce.com. Gartner does not endorse any vendor, product or service depicted in its research publications, and does not advise technology users to select only those vendors with the highest ratings. Gartner research …

  • Microsoft® Office 365 is a top choice for enterprises that want a cloud-based suite of productivity/ collaboration applications. With Office 365, you get access to Microsoft™ Office solutions practically anytime, anywhere, on virtually any device. It's a great option for current Microsoft users who can now build on their experience with Microsoft™ solutions while enjoying the flexibility of a cloud-based delivery. But even organizations with no previous investment in Microsoft will find that …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date