Thread: C passing an array of struct to delete one problems (from a newbie)

Originally Posted by phantomotap

You know what, I should be ashamed. I knew that you weren't as experienced as you claim.

Do try not to be a complete idiot.

I'll take bets that you've never worked with random access files... not even as a learning experience.

Tell me one good reason why I should have to write all this extra code when I can simply copy the string data into a buffer inside the struct and write the whole thing to disk?

Here's a little learning experience for you...
Write an inventory program capable of accessing/maintaining a 1gb+ inventory data file with over 400,000 entries in it... Do you really think you're going to load that whole thing into a linked list and work with string literals?

CLUE TIME!

Originally Posted by phantomotap

^_^

Are you writing a download manager?

Anyway, considering the state of your program, I'd say you are a long way from managing whatever it is you are doing. Why not grab a C implementation of a linked list and see if you can follow it? Better yet, why not write one yourself first because that will surely help with your memory management problems.

In any event, a tree indexed with the most relevant data is probably your best bet.

Soma

Well yes an no, kinda.

I'm watching the packets (all of them). Now packets destined for a certain ports are the ones that I'm after. In a simple case let's say IM.

What I have working so far...

I get each packet. If tcp AND that port, process it. In processing I already have everything for capturing and logging to disk the "conversation"... no problems there. It knows how/where to get the username from/to, how to distinguish that it is a properly constructed im packet, etc.

Now usera sends userb a file. I see that, I have that already. User b accepts the file. See it, got it. Now what I want to do is when userb accepts, It will have a certain signature and filename that I will see in the originating request packet for the file. I store this signature and filename and watch for it. Working fine. Now I see that request packet, and parsing it, I know where the data is going (destination port) and what size it is expecting to get.

I want to store all that and be watching for it in the main loop. Basically I want this array, or list, or whatever is the best way to rack this information to be checked back at the beginning.

So I get a packet - I check this watch list. If nothing in the list - continue. If something in the watch list - check that destination port. Did I find a match? Yes - ok - run a different packet_processing function that is basically going to take the data element from this packet, and append it to a temporary file of the filename stored (actually the md5 hash of the origin datetime request+filename... in case multiple files of same filename are sent). Now in this second process (writing data to the file) - at the end of each receipt - stat the file... is it correct? Do I have all the data expected? Yes? Move the file to a processing directory. Remove that port, filename, etc from the watch list.

Originally Posted by snowolfe

Well yes an no, kinda.

Just so you know snowolfe ... I've just put that total idiot Phantomotap in my ignore list.

I'm going to bow out of this and let you continue with the others.

*shrug*

Well, it depends on how much traffic you may process, but yea, you are almost certainly better off with a tree indexed on the port number.

The point I was trying to make to you though, is that this isn't trivial and you are much better served starting with something simpler until and build up to modifying your program.

Soma

Ok - how's this look?

(Seems to work the way I need it)

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct ts{
  char *fname;
  char *lname;
  char *fingers;
  char *toes;
  struct ts *next;
}TS;

TS *mainrec=NULL;

void addone(char *, char *, char *, char *);
void printout();
void findandprint(char *, char *);

int delone(char *, char*);

int main(int argc, char **argv){
  
  addone("joe", "bob", "1", "1");
  printout();

  addone("bobby", "sue", "2", "2");
  printout();

  addone("blah", "blah", "3", "3");
  printout();

  addone("bobby", "joe", "4", "4");
  printout();

  addone("bobby", "hill", "5", "5");
  printout();

  if(delone("joe", "bob")){
    printf("Did not find - error\n\n");
  }
  else{
    printf("found and deleted\n\n");
  }

  if(delone("joey", "bob")){
    printf("Did not find - error\n\n");
  }
  else{
    printf("found and deleted\n\n");
  }

  printout();

  if(delone("bobby", "hill")){
    printf("Did not find - error\n\n");
  }
  else{
    printf("found and deleted\n\n");
  }

  printout();

  findandprint("blah", "blah");  

  return 0;
}

void addone(char *pfname, char *plname, char *pfingers, char *ptoes){
  TS *trec;
  trec=(TS *)malloc(sizeof(TS));
  trec->fname=pfname;
  trec->lname=plname;
  trec->fingers=pfingers;
  trec->toes=ptoes;

  if(mainrec==NULL){
    mainrec=trec;
    mainrec->next=NULL;
  }
  else{
    trec->next=mainrec;
    mainrec=trec;
  }
}

int delone(char *pfname, char *plname){
  TS *tprev, *tcur;

  tcur=mainrec;

  while(tcur!=NULL){
    if(tcur->fname==pfname && tcur->lname==plname){
      if(tcur==mainrec){
        mainrec=tcur->next;
        free(tcur);
        return 0;
      }
      else{
        tprev->next=tcur->next;
        free(tcur);
        return 0;
      }
    }
    else{
      tprev=tcur;
      tcur=tcur->next;
    }
  }

  return 1;
}

void printout(){
  TS *trec;

  trec=mainrec;

  if(trec==NULL){
    return;
  }
  else{
    printf("What we have so far\n");
    printf("___________________\n");

    while(trec!=NULL){
      printf("fname: %s\n", trec->fname);
      printf("lname: %s\n", trec->lname);
      printf("fingers: %s\n", trec->fingers);
      printf("toes: %s\n\n", trec->toes);
      trec=trec->next;
    }
  }
  return;
}

void findandprint(char *pfname, char *plname){
  TS *trec;

  trec=mainrec;

  if(trec==NULL){
    return;
  }
  else{
    while(trec!=NULL){
      if(trec->fname==pfname && trec->lname==plname){
        printf("found record for fname:%s, lname:%s\n", pfname, plname);
        printf("___________________________________\n");
        printf("fname: %s\n", trec->fname);
        printf("lname: %s\n", trec->lname);
        printf("fingers: %s\n", trec->fingers);
        printf("toes: %s\n\n", trec->toes);
        return;
       }
      trec=trec->next;
    }
  }
  return;
}

Still assigning string literals I see....

Ok, something to ponder... Joe has changed his name to John, which you have in NewName[30] and now you need to update that record...

Originally Posted by CommonTater

Still assigning string literals I see....

Ok, something to ponder... Joe has changed his name to John, which you have in NewName[30] and now you need to update that record...

Just doing the literals for working with it - actually are already char *'s in the function that will be calling the add/delete/find.

Was not actually concerned with anything changing. Basically I will be tracking a service, time, destination port, filename. None of that is going to change, so all I was looking for was basically to add onto the stack, or remove off the stack and find in the stack.

But, in interest of learning, couldn't I simply create a proc that would take arguments such as

Code:

TS *replace(char *oldfname, char *oldlname, char *newfname, char *newlname){
  TS *trec;
    

  trec=mainrec;
  if(trec==NULL){
    return trec;
  }
  else{
    while(trec!=NULL){
      if(trec->fname==oldfname && trec->lname==oldlname){
        trec->fname=newfname;
        trec->lname=newlname;
        return trec;
       }
      trec=trec->next;
    }
  }
  return trec;
}

Originally Posted by CommonTater

All this to avoid using char[20]; (or such) in a struct? Really...
Watch this...

Code:

// the struct
typedef struct t_User
   { char Name1[20];
     char Name2[20];
     // whatever else you need 
    } User;

// get names
void GetName(char *Name)
  { printf("Enter your name  : ");
     scanf("%19s", Name); }

int main (void)
   {  User Users;
       GetName(Users.Name1);
       GetName(Users.Name2);
       printf("%s %s\n", Users.Name1,Users.Name2); 
       return 0; }

See how much easier that is? And it works...

In your code where you have something in a string just use strcpy();

Code:

strcpy(users.name1,NewName);

Over my time dabbling in C I've probably tried a dozen different "bright idea" ways of assigning strings across the equals sign... exactly none of them worked.

Thanks much for all the help... like I said - been years and now re-learning. I'm used to perl and php where I can do simple assignments and not worry so much with reference to, address, pointers, etc (mostly web programming).

I just want to point out that the only reason assignment does not work with C strings is because C strings are a particular kind of array. You can't assign a C string because you can't assign arrays.

You can use initialization, though.

Code:

char username[] = "John Doe";

Perfectly legal, but not useful at any other time.

There is no real trick to get string assignment, so don't waste your time. You have to use something like strncpy. Or strncat even: As long as dest[0] is '\0' you will always get a C string in return.