Click here to Skip to main content
Click here to Skip to main content
Add your own
alternative version
Go to top

A handy class to make use of Windows Registry

, 15 Aug 2004
Shows how simple accessing Windows Registry can be if you do not need bells and whistles.
simple_registry_demo.zip
a_better_example.exe
dirty_and_fast.exe
main.exe
with_trace.exe
simple_registry_src.zip
dirty_and_fast
dirty_and_fast.dsp
with_trace
with_trace.dsp
main.dsp
main.dsw
a_better_example
a_better_example.dsp
Sources update
sources have been updated. (Hopefully) This will make them compilable on VC 7+.
I couldn't test it with VC 7, but I expect it will be OK now. 
for more info take a look <a href="http://www.codeproject.com/system/simple_registry.asp?msg=896795#xx896795xx">what was the problem.</a>

New Additions
This class has been modified:

Improved internal logic. 
Improved support for writing structured data to registry 
Added possiblitity to see internal execution flow (e.g. when data is read 
from and written to the registry) 
Added support for HKEY_LOCAL_MACHINE, HKEY_USERS, and all the others...
In short, in order to store a structure in registry you only need to do like this:

SomeStruct X;
//set struct values...
reg["SomeStructData"].set_struct(X);

In order to read back the stored structure:

SomeStruct X;
//set struct values...
if(reg["SomeStructData"].get_struct(X)){
	//Ok, X contains the read data...
}else {
	//error reading struct.
}

In order to use HKEY_LOCAL_MACHINE or other you can pass a second parameter 
of type registry::Key to registry constructor:

registry reg("Sowtware\\Whatever",registry::hkey_local_machine);


The second parameter is optional, it defaults to registry::hkey_current_user 

In order to see internal execution flow you may #define WANT_TRACE 
and in console mode you'll see when and what objects are created, 
and when values read to/ written from the registry. There was added 
a new project with_trace to see that. 


//with trace

#define WANT_TRACE //define this to be able to see internal details...

#include "registry.h"
#include "string.h"
#include 

struct Something{
	int area;
	float height;
};

int main(int, char*)
{
	registry reg("Software\\Company");
	{
		Something X;
		X.area=100;
		X.height=4.5;
		
		reg["Something"].set_struct(X);
	}
	Something Z;
	if(reg["Something"].get_struct(Z)){
		printf("area is: %i\nheight is: %f\n", Z.area,Z.height);
	}

	return 0;
}


It produces the following output: 

Introduction
First of all, you need only one file "registry.h", that's included 
in the source distribution. Read on...

//Dirty and fast howto

#include "registry.h"
#include "string.h"

int main(int, char*){

    registry reg("Software\\Company");
    reg["Language"]="English";        //set value
    reg["Width"]=50;
    printf("The address is: %s\n",(char*)reg["Address"]); 
    //prints nothing unless you put something in
    return 0;
}


A more descriptive howto:

//Long story:

#include "registry.h"
#include "string.h"

struct ServerAddress{
    char name[64];
    char ip[15];
    short port;
};

int main(int,char*){

    //first step is to create our home registry 
    //record(or open it if exists)
    //the constructor accepts a string and if you do:
    registry settings("Software\\MyCoolApp");
    //you open HKEY_CURRENT_USER\Sowtware\MyCoolApp

    //Due to simplicity this class is desined to deal with only 
    //HKEY_CURRENT_USER registry group. 
    //You may, however, modify this behavior if you need

    //To make sure that the home key has been created or 
    //opened you can test it like this:

    if(!settings){
        //error code goes here...
        exit(1);
    }

    //The next step is to create (or open if exists) 
    //a value key:
    //the official way is like this: (for another, 
    //simpler way, read below.)

    registry::iterator lang=settings["Language"];    
    //Personally I don't use it this way - too much to type...

    //and then you can retrive value of "Language" key 
    //as follows:

    printf("The selected language is: \"%s\"\n",(char*)lang);

    //if you want to modify a value you can do simply like this:

    lang="Russian";

    //Internally this class stores values as 
    //binary data and therefore 
    //you are not limited to strings only.

    // Example:

    ServerAddress MyCoolServer;
    strcpy(MyCoolServer.name,"somewhere.example.com");
    strcpy(MyCoolServer.ip,"192.168.0.1");
    MyCoolServer.port=1024;

    //now let's put this record into registry key "server"
    //it can be simply done like this:

    registry::iterator server=settings["server"];
    server=string((const char *)(&MyCoolServer),sizeof(MyCoolServer));

    //now let's test by retriving the structure back:

    ServerAddress serAdr;
    const string &FromRegistry=server;
    //copy data only if it's of the size of the struct ServerAddress
    if(FromRegistry.length()==sizeof(ServerAddress)){        
        memcpy(&serAdr,FromRegistry.c_str(), sizeof(ServerAddress));
        //now let's see what we have (see a pic below):
        printf("Print out for my server:\n");
        printf("\tserver's host name is:  %s\n",    serAdr.name);
        printf("\tserver's ip address is: %s\n",    serAdr.ip);
        printf("\tserver's port is:       %u\n\n",  serAdr.port);
    }else{
        //error code goes here...
    }
    return 0;
}





Pic.1 Output from A more descriptive howto. 
 

I coded these few lines with simplisity in mind. I like the 
style, when I can assign value to a registry key as to a usual 
variable. I will describe shortly how I use this code in my projects. 
I put a member variable reg (instance of registry) to my app's 
class (there is a reason, read below) that needs access to the 
registry. Then, in the class's constructor, I instantiate reg 
variable to the registry home key. Since there is no default 
constructor in the registry class, you may do it like this:

class my_app{
protected:
    registry reg;
    string UserName;
public:
    my_app() : reg("Software\\my_app"){ // <--
        UserName = reg["UserName"]; //read value
    }
    ~my_app(){
        //store value back to the registry
        reg["UserName"] = UserName;
    }
}


In the preceiding line you actually don't need to create a 
separate string for UserName - you may have a member variable 
of registry::iterator type, that will be automatically stored 
to the registry when your class is destructed. (see the final 
example at the bottom of the page) 

And then, whenever you need, you can do like this:

SetLanguage(reg["Lang"]); 
string UserName=reg["User"];


that's really simple...

 Background
Now a little background on how it works internally. This is 
actually a very lightweight class. It makes less api calls 
than you would probably do.

For example, the line 


reg["Something"]="nothing";



will only once physically access registry on destruction of 
the returned key-value to assign value "nothing" to key "something". 

Same happens with the next lines (only one api call when the 
group goes out of scope):


registry::iterator name=settings["UserName"];
name="John";
name="Alex";
name="Someone Else";


Basicly, if you intend to use this class you should be 
aware that statement reg["something"]="nothing"; doesn't
 modify anything in registry by itself. The value will be 
 set only when the statement goes out of scope, like this:


{
    reg["UserName"]="Bill";
    printf("The username is: %s\n", (char*)reg["UserName"]); 
    //!!WILL NOT PRINT BILL, 
    //it will print the value that was before the previous line
}//at this point the value Bill is in the registry
printf("The username is: %s\n", (char*)reg["UserName"]); //now it prints Bill;


In order to force it to commit to the registry at some 
point you can use flush() method like this:

registry::iterator name=settings["UserName"];
name="John";
name.flush(); //at this point it will write value "John" to registry.


The same aplies to reading values - they are retrived 
only when you request them, and only once! So, if you 
know (or think) that something else (perhaps Earth's 
magnetic field :) has modified a key's value you may use 
refresh() method. But, be carfull!! Anything you have 
assigned before will not be commited (it's overwritten 
by the returned value from registry);

And a very important point. When the instance of registry 
is destructed, or goes out of scope, then ALL the values 
you created from it will not have access to the registry. 
That is, all iterators on a given registry instance should 
be destructed before their parent registry instance. 
That's why I use this class as a member of another class. 
When the parent class is destroyed it doesn't need access 
to the registry, neither it is possible at that point.

That's it. Hope it will be usefull to someone. 

A better example
#include "registry.h"
#include <iostream>


class my_app{
protected:
    registry reg;
    registry::iterator UserName;
public:
    my_app():reg("Software\\Company"),UserName(reg["UserName"]){}
    ~my_app(){}
    void SetUserName(const char * name){
        UserName = name;
    }
    const char * GetUserName(){
        return (const char *) UserName;
    }
};

int main (int, char *){
    my_app App;
    App.SetUserName("Alex");
    cout<<"The username is: "<<App.GetUserName()<<endl<<"Thanks for playing..."<<endl;
    return 0;
}


/**/ Author: Pavel Pavlov block111@yandex.ru

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

Share

About the Author

__PPS__

Canada Canada
Big Grin | :-D

| Advertise | Privacy | Mobile
Web04 | 2.8.140916.1 | Last Updated 16 Aug 2004
Article Copyright 2004 by __PPS__
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid