How to fetch values from memory using structure variable name.

shanmugarajaa

my application consists of structure with 200 member variable.

For Example: Struct sample { char xyz[200]; int x1[400]; char y2[100][10]; float z2[200]; ................... ................. .................. ................ } Now user will just passes the value like xyz[100], x1[201] and my application need to fetch the corresponding value from memory and display to them kindly help me friends..

Albert Holguin

200 members in a structure? ...sounds like bad design already. It's not clear what you mean when you say user will "pass a value and application will fetch the corresponding value". Fetch from where?

shanmugarajaa

For example: 1. x1[100] is the Struct variable which hold the value of 10 2. Now User gives the input as x1[100] in the given textbox. 3. My application need to fetch the value 10(for x1[100]) from the memory location and display value 10 to user.

Albert Holguin

there are multiple steps... which one do you need help with? ...for a user to point out a variable in an array, all you need to do is ask for the name of the array and the index... then look up the name or label against a set of valid labels, and use the index specified to grab the value.

shanmugarajaa

whether it is possible to calculate offset value? and Using offset, the struct variable value is fetched from the memory loaction.

Chandrasekharan P

Calculate Offset Value?? why?? Albert has given a very good suggestion. why not try that?

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shanmugarajaa

My senior engineer Implemented offset table procedure concept. Using offset table particular structure variable value is fetched from memory location and whenever structure get updated or modified then obviously offset table get modified or changed.Now days it became big problem for us. my question is whether albert idea is effect than this offset table procedure or any other suggestion is there to implement.

CPallini

shanmugarajaa wrote:

my application consists of structure with 200 member variable.

Uhm... Is that really needed?

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shanmugarajaa

Long year ago my senior engineers designed like that and i can't change those things. now my aim is to findout new way to get value for those structure variable without using offset table... any other choice is there?

Lost User

200 member variables! Holy crap! Are they all named as badly as these? Just how is a user supposed to know the relevance of what IS stored at x1[100]? Apart from that, quite simply your app, which contains the struct instance, lets say it is called strinst, when asked for the value x1[100] just returns strint.x1[100], probably printfed into a string, for display.

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shanmugarajaa

But they are not created instant for an structure... instead of that they calculated offset value for each variable which is present in the structure. I dont know why they using such procedure...

Lost User

So you have the memory address, and you know the structure format, just cast the address to a struct pointer and access it as mystrinstptr->x1[100] If you dont have access to the memory you cant do anything.

============================== Nothing to say.

Albert Holguin

Using an offset value for this is just silly. There's no practical purpose and adds complexity with no benefit.

Lost User

Hi, It sounds to me like you want to do this with the compiler preprocessor. Yes you can do this but it will be very ugly indeed. You will need to build the structs with #define statements and you can retrieve the member names with the #NAME directive[^]. You can get the offset to the struct members with the FIELD_OFFSET macro. Best Wishes, -David Delaune