access dynamically allocated structure

rupeshkp728

I want to fill a structure and then print it. How to print the values of the structue? The structure is: #define UINT32 unsigned int #define INT32 int #define UCHAR unsigned char typedef struct CheckSumPair { UINT32 weakcs; // The weak, rolling Adler32 checksum. UCHAR StrongCS[10]; }; I have dynamically allocated memory to it as folows. CheckSumPair* CSPair = (CheckSumPair*)malloc(sizeof(CheckSumPair)*10); for(int x = 0;x < 10;x++) { CSPair->weakcs = (UINT32)x+1; strncpy((char*)CSPair->StrongCS,(char*)"XYZ",10); strncpy((char*)CSPair->StrongCSString,(char*)"CEDVCD",10*2+1); } Now print the values for(int x = 0;x < 10;x++) printf("%d %s %s\n\n",CSPair[x]->.weakcs,CSPair[x]->StrongCS,CSPair[x]->StrongCSString); While printing the values I get the following error: error C2232: '->CheckSumPair::StrongCS' : left operand has 'struct' type, use '.' error C2819: type 'CheckSumPair' does not have an overloaded member 'operator ->' see declaration of 'CheckSumPair'

Eugen Podsypalnikov

Try this access in your loops :) :

{
CheckSumPair* psTempPair = (CheckSumPair*) ((BYTE*)CSPair + sizeof(CheckSumPair) * x);
// psTempPair->Member1
// psTempPair->Member2
}

virtual void BeHappy() = 0;

Lost User

The address CSPair[x] is a structure reference not a pointer, hence use the '.' member access operator.

txtspeak is the realm of 9 year old children, not developers. Christian Graus

Lost User

Eugen Podsypalnikov wrote:

CheckSumPair* psTempPair = (CheckSumPair*) ((BYTE*)CSPair + sizeof(CheckSumPair) * x);

All this casting is unnecessary and prone to error, the compiler handles pointer arithmetic automatically.

txtspeak is the realm of 9 year old children, not developers. Christian Graus

rupeshkp728

thanks eugen for the reply that was a typing mistake issue is resolved by using CheckSumpair[x].memberN; . . . since i am using [] operator to access pointer no need of using ->

KingsGambit

I think you have to print the values as follows:

for(int x = 0; x < 10; x++)
printf("%d %s %s\n\n",CSPair[x].weakcs, CSPair[x].StrongCS, CSPair[x].StrongCSString);

or

for(int x = 0; x < 10; x++)
{
printf("%d %s %s\n\n",CSPair->weakcs,CSPair->StrongCS,CSPair->StrongCSString);

CSPair++;
}

CPallini

Your code is really ugly.

rupeshkp728 wrote:

#define UINT32 unsigned int #define INT32 int #define UCHAR unsigned char

Why do you use #define instead of typedef?

rupeshkp728 wrote:

typedef struct CheckSumPair { UINT32 weakcs; // The weak, rolling Adler32 checksum. UCHAR StrongCS[10]; };

Typedef what?

rupeshkp728 wrote:

CheckSumPair* CSPair = (CheckSumPair*)malloc(sizeof(CheckSumPair)*10);

Why are you using malloc? Do you really need to use C memory allocation functions?

rupeshkp728 wrote:

strncpy((char*)CSPair->StrongCSString,(char*)"CEDVCD",10*2+1);

struct CheckSumPair has no StrongCSString member.

rupeshkp728 wrote:

printf("%d %s %s\n\n",CSPair[x]->.weakcs,CSPair[x]->StrongCS,CSPair[x]->StrongCSString);

This is the ugliest part. What are you trying to do? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

Eugen Podsypalnikov

In this case - it is necessary, since sizeof(CheckSumPair*) != sizeof(CheckSumPair) ! :)

virtual void BeHappy() = 0;

User 3919723

is CheckSumPair not CheckSumPair*, so you can't use "->", use "." instead. Instruction "CSPair[x]->.weakcs" contains "->" and ".". Why malloc? use the new operator instead:

CheckSumPair* CSPair = new CheckSumPair[10];

or better, if possible:

CheckSumPair CSPair[10];

And finally, you have to explain what are you trying to do with the two strncpy, maybe your code has to be like:

#define UINT32 unsigned int
#define INT32 int
#define UCHAR unsigned char

typedef struct
{
UINT32 weakcs; // The weak, rolling Adler32 checksum.
UCHAR StrongCS[10 + 1]; // including the string terminator
UCHAR StrongCSString[10 + 1]; // including the string terminator
} CheckSumPair;

int main()
{
CheckSumPair CSPair[10];

for(int x = 0; x < 10; x++)
{
	CSPair\[x\].weakcs = (UINT32)x+1;
	strncpy((char\*)CSPair\[x\].StrongCS, "XYZ", 10);
	strncpy((char\*)CSPair\[x\].StrongCSString, "CEDVCD", 10);
}


for(int x = 0; x < 10; x++)
{
	printf("%d %s %s\\n\\n", CSPair\[x\].weakcs, CSPair\[x\].StrongCS, CSPair\[x\].StrongCSString);
}

return 0;

}

Lost User

Pointers to structures can be incremented by simple expressions thus:

CSPair++;

that is all that is needed to point to the next entry in the array.

txtspeak is the realm of 9 year old children, not developers. Christian Graus

Eugen Podsypalnikov

Yes, they can !!! :-D You are right, Richard ! (probably I was intricated by malloc... :-D ) Thank you very much ! :thumbsup:

virtual void BeHappy() = 0;