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  • Your email address will not be published.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

  • Bonita BPM 7 is here! And for you, an in-depth tour of its innovation. In this webinar, we'll guide you through the brand-new features of this release and demonstrate them live. You will: Discover how business application implementation and maintenance is now even easier, with decoupling of process logic, business data and user interface Learn how to create "living applications" for business processes which present business data in custom views We recommend that you watch the half-hour recording of our …

  • Thanks to wide spread cloud hosting and innovations small businesses can meet and exceed the legacy systems of goliath corporations. Explore the freedom to work how you want, with a phone system that will adapt to your evolving needs and actually save you lots of expense—read Get an Enterprise Phone System without High Cost and Complexity. The article clearly illustrates: The only hardware you'll need is phone equipment for advanced voice and fax. How to join all your employees, mobile devices, …

Most Popular Programming Stories

More for Developers

RSS Feeds

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