Forcing copy of array item

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December 9th, 2005, 09:54 AM

crazyone

Contributing User

Join Date: Dec 2005

Posts: 75

Time spent in forums: 18 h 56 m 9 sec
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Forcing copy of array item

Hi all,

IM currently programming good old ANSI C for a PALM application. My problem is i have a global var in the form of an array containing several structs.

For the sake of simplicity and to save the current settings the user might have entered previously, i make a copy of the current struct he wants to modify (typedef struct {...} medication

from the array "normal_medications" to a new standalone var called "current_medication".

Problem is, it seems its copying a pointer of the struct from the array into my standalone variable. Needless to say that this can't work since my main objective is to have a temp copy of this item at hand.

So i tried to copy each element of the struct manually item by item but it still copies pointers to these items. I'm clueless as to what to do. I remember from a long time ago that there is supposed to be an operator in the assignement i can use to force a copy of this item to be passed from the array to my standalone variable.

Here is some code that can help you understand my prob:

MAIN.C
-------

medication normal_start[4];

MAIN.H
-------

//A product chosen in the start portion is described by these params
typedef struct {
Boolean hasBeenInit; //SelfExplains
Boolean substSet; //Since 0 is still valid for subst, we need a flag to make sure it's been set
Boolean stypeSet; //Since 0 is still valid for stype, we need a flag to make sure it's been set
Boolean vaSet; //Since 0 is still valid for va, we need a flag to make sure it's been set
UInt16 subst; //Contains a substance (See defines below)
UInt16 va; //Contains the VA(See defines below)
UInt16 stype; //Contains the stype (See defines below)
char name[32]; //Contains the commercial name of the product chosen
double dosage; //Contains the dose administered
char finalconstr[32]; //Contains the final constructed string
} medication;

MEDFORM.C
-----------
...
...
extern medication normal_start[4];
medication current_medication;
....
....
switch(curMedFormState.substatepos){
case state_main:
current_medication = normal_start[curMedFormState.medicationIndex];
break;
case state_interdose:
current_medication = interdose_start[curMedFormState.medicationIndex];
break;
}
....
....

December 9th, 2005, 10:21 AM

Dave Sinkula

Contributing User

Dev Shed Intermediate (1500 - 1999 posts)

Join Date: Apr 2004

Posts: 1,676

Time spent in forums: 1 Month 3 Days 8 h 23 m 46 sec
Reputation Power: 132

Structure assignment should make a bytewise copy. I don't supposed you could strip the issue down to a canned code sample that demonstrates the problem? (That is, make some example that is not scattered in separate files with some example data and perhaps a few printf's -- the answer may pop out at you while doing so, and if not it would be easier for others here to try to compile it and give you an answer.)

[edit]For example,

Code:

#include <stdio.h>

struct T
{
   short    changed;
   unsigned check;
   double   digits;
   char     broiled[20];
};

struct T array[] =
{
   {42, 12345, 67.89, "Element 0"},
   {-1, 23456, 78.91, "Element 1"},
   {10, 34567, 89.12, "Element 2"},
   {-5, 45678, 90.23, "Element 3"},
};

void print(struct T *item)
{
   printf("changed = %hd, check = %u, digits = %g, broiled = %s\n",
          item->changed, item->check, item->digits, item->broiled);
}

int main()
{
   size_t i;
   for ( i = 0; i < sizeof array / sizeof *array; ++i )
   {
      struct T copy = array[i];
      print(&copy);
   }
   return 0;
}

/* my output
changed = 42, check = 12345, digits = 67.89, broiled = Element 0
changed = -1, check = 23456, digits = 78.91, broiled = Element 1
changed = 10, check = 34567, digits = 89.12, broiled = Element 2
changed = -5, check = 45678, digits = 90.23, broiled = Element 3
*/

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Last edited by Dave Sinkula : December 9th, 2005 at 10:35 AM.

December 9th, 2005, 04:33 PM

crazyone

Contributing User

Join Date: Dec 2005

Posts: 75

Time spent in forums: 18 h 56 m 9 sec
Reputation Power: 9

For some reason i don't know, i changed nothing at all in the code except the index of the array which was 1 based at the time but since being 1 based in a 4 item array, the item #1 wasnt technically wrong... but since i changed it to a 0 based array (changed my for loop) everything worked... strange...

CrazyOne

Forcing copy of array item

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