sizeof

[Slain]

I am using sizeof to doa memcpy but run into probs because of the
following problem.

static char arr1[] = {0x01,0x00,0x03 ,0x04};
static char arr2[] = {0x00,0x03,0x04 ,0x06,0x07};

const char* string_CDR[8]= {arr1,arr2};


cout<<"The size of is " <<sizeof(arr1)< <" and "<<sizeof(a rr2) <<endl;
cout<<"The size of is " <<sizeof(string _CDR[0])<<" and
"<<sizeof(strin g_CDR[1]) <<endl;

I expect the sizeof(string_C DR[0]) to be 4 and of
sizeof(string_C DR[1]) to be 5. But the output is as below.
The size of is 4 and 5
The size of is 4 and 4


This is messing up my memcpy in the main function as the sizeof is not
what I am expecting. Can anyone point out the problem.

Thanks
Manny

[Ian Collins]

Re: sizeof

Slain wrote:

I am using sizeof to doa memcpy but run into probs because of the
following problem.
>
static char arr1[] = {0x01,0x00,0x03 ,0x04};
static char arr2[] = {0x00,0x03,0x04 ,0x06,0x07};
>
const char* string_CDR[8]= {arr1,arr2};
>
>
cout<<"The size of is " <<sizeof(arr1)< <" and "<<sizeof(a rr2) <<endl;
cout<<"The size of is " <<sizeof(string _CDR[0])<<" and
"<<sizeof(strin g_CDR[1]) <<endl;
>

This line outputs sizeof(char*) twice.

>
This is messing up my memcpy in the main function as the sizeof is not
what I am expecting. Can anyone point out the problem.
>

There is no way to calculate the size of the arrays pointed to in
string_CDR.

Use std::vector.

--
Ian Collins.

[Slain]

Re: sizeof

On Mar 7, 4:19 pm, Ian Collins <ian-n...@hotmail.co mwrote:

Slain wrote:

I am using sizeof to doa memcpy but run into probs because of the
following problem.

>

static char arr1[] = {0x01,0x00,0x03 ,0x04};
static char arr2[] = {0x00,0x03,0x04 ,0x06,0x07};

>

const char* string_CDR[8]= {arr1,arr2};

>

cout<<"The size of is " <<sizeof(arr1)< <" and "<<sizeof(a rr2)  <<endl;
cout<<"The size of is " <<sizeof(string _CDR[0])<<" and
"<<sizeof(strin g_CDR[1])  <<endl;

>
This line outputs sizeof(char*) twice.
>
>
>

This is messing up my memcpy in the main function as the sizeof is not
what I am expecting. Can anyone point out the problem.

>
There is no way to calculate the size of the arrays pointed to in
string_CDR.
>
Use std::vector.
>
--
Ian Collins.

DOn't have STL's. Is there any other way to define either string_CDR
or some kind of casting?

[Ian Collins]

Re: sizeof

Slain wrote:

On Mar 7, 4:19 pm, Ian Collins <ian-n...@hotmail.co mwrote:

>Slain wrote:

>>I am using sizeof to doa memcpy but run into probs because of the
>>following problem.
>>static char arr1[] = {0x01,0x00,0x03 ,0x04};
>>static char arr2[] = {0x00,0x03,0x04 ,0x06,0x07};
>>const char* string_CDR[8]= {arr1,arr2};
>>cout<<"The size of is " <<sizeof(arr1)< <" and "<<sizeof(a rr2) <<endl;
>>cout<<"The size of is " <<sizeof(string _CDR[0])<<" and
>>"<<sizeof(str ing_CDR[1]) <<endl;

>This line outputs sizeof(char*) twice.
>>

>>This is messing up my memcpy in the main function as the sizeof is not
>>what I am expecting. Can anyone point out the problem.

>There is no way to calculate the size of the arrays pointed to in
>string_CDR.
>>
>Use std::vector.
>>

*PLease* don't quote signatures.

>
DOn't have STL's. Is there any other way to define either string_CDR
or some kind of casting?

Then you have to save the length of the arrays somewhere. Why not use a
small struct (with the pointer to the array and its size as members) as
the type for string_CDR?

--
Ian Collins.

[Shobhit Gupta]

Re: sizeof

You could do something like this: (I chose to stick closely with your
problem, otherwise you would be better off with dynamically allocated
arrays)



struct MyArray{
public:
char *arr;
unsigned int size;
MyArray() {}
void initialize(char tempArr[], int tempSize){
arr = tempArr;
size = tempSize;
}


};

#define initialize(arg) initialize(arg, sizeof(arg))

int main()
{
static char arr1[] = {0x01,0x00,0x03 ,0x04};
static char arr2[] = {0x00,0x03,0x04 ,0x06,0x07};

MyArray m1, m2;
m1.initialize(a rr1);
m2.initialize(a rr2);
const MyArray string_CDR[8]= {m1,m2};

cout<<"The size of is " << string_CDR[0].size<<" and "<<
string_CDR[1].size <<endl;
return 0;
}

-Shobhit

http://shobhitgupta12.blogspot.com

[Ian Collins]

Re: sizeof

[please retain context and attributions]

Shobhit Gupta wrote:

You could do something like this: (I chose to stick closely with your
problem, otherwise you would be better off with dynamically allocated
arrays)
>
struct MyArray{
public:
char *arr;
unsigned int size;
MyArray() {}
void initialize(char tempArr[], int tempSize){
arr = tempArr;
size = tempSize;
}
>

Why not do this in the constructor?

>
};
>
#define initialize(arg) initialize(arg, sizeof(arg))
>

You never use this.

--
Ian Collins.

[Shobhit Gupta]

Re: sizeof

Why not do this in the constructor?

>

#define initialize(arg) initialize(arg, sizeof(arg))

>
You never use this.

I thought of making code inside main() more readable for Slain guy
( Manny )

So I thought of having only 1 argument, by which both array and its
size could be set.
Thats why I used a #define.
And #defining a constructor didn't seem like a good idea, so I created
an initialize().

I just wanted to float the idea of grouping "The array" & "its size"
in a struct; and as I said earlier there could be definitely be much
more better way of implementing it.

[Ian Collins]

Re: sizeof

[*please* don't snip attributions!]

Shobhit Gupta wrote:

Ian Collins wrote:

>Why not do this in the constructor?
>>

>>#define initialize(arg) initialize(arg, sizeof(arg))

>You never use this.

>
I thought of making code inside main() more readable for Slain guy
( Manny )
>
So I thought of having only 1 argument, by which both array and its
size could be set.
Thats why I used a #define.
And #defining a constructor didn't seem like a good idea, so I created
an initialize().
>
I just wanted to float the idea of grouping "The array" & "its size"
in a struct; and as I said earlier there could be definitely be much
more better way of implementing it.
>

OK. The simple template approach hinted at by Victor has the advantage
of not adding a size member to the struct.

--
Ian Collins.

[James Kanze]

Re: sizeof

On 7 mar, 22:37, Slain <Slai...@gmail. comwrote:

On Mar 7, 4:19 pm, Ian Collins <ian-n...@hotmail.co mwrote:

Slain wrote:

I am using sizeof to doa memcpy but run into probs because of the
following problem.

static char arr1[] = {0x01,0x00,0x03 ,0x04};
static char arr2[] = {0x00,0x03,0x04 ,0x06,0x07};

const char* string_CDR[8]= {arr1,arr2};

cout<<"The size of is " <<sizeof(arr1)< <" and "<<sizeof(a rr2) <<endl;
cout<<"The size of is " <<sizeof(string _CDR[0])<<" and
"<<sizeof(strin g_CDR[1]) <<endl;

This line outputs sizeof(char*) twice.

This is messing up my memcpy in the main function as the
sizeof is not what I am expecting. Can anyone point out
the problem.

There is no way to calculate the size of the arrays pointed to in
string_CDR.

Use std::vector.

DOn't have STL's.

Why not? The alternative is reimplementing all of the logic it
contains manually. You seem to want the behavoir of a
container. So you really only have two choices: use the
standard containers, or implement one yourself.

--
James Kanze (GABI Software) email:james.kan ze@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34

[Micah Cowan]

Re: sizeof

James Kanze <james.kanze@gm ail.comwrites:

On 7 mar, 22:37, Slain <Slai...@gmail. comwrote:

>On Mar 7, 4:19 pm, Ian Collins <ian-n...@hotmail.co mwrote:

Slain wrote:
I am using sizeof to doa memcpy but run into probs because of the
following problem.

>

static char arr1[] = {0x01,0x00,0x03 ,0x04};
static char arr2[] = {0x00,0x03,0x04 ,0x06,0x07};

>

const char* string_CDR[8]= {arr1,arr2};

>

cout<<"The size of is " <<sizeof(arr1)< <" and "<<sizeof(a rr2) <<endl;
cout<<"The size of is " <<sizeof(string _CDR[0])<<" and
"<<sizeof(strin g_CDR[1]) <<endl;

>

This line outputs sizeof(char*) twice.

>

This is messing up my memcpy in the main function as the
sizeof is not what I am expecting. Can anyone point out
the problem.

>

There is no way to calculate the size of the arrays pointed to in
string_CDR.

>

Use std::vector.

>

>DOn't have STL's.

>
Why not? The alternative is reimplementing all of the logic it
contains manually.

Might be using a freestanding implementation.

You seem to want the behavoir of a
container. So you really only have two choices: use the
standard containers, or implement one yourself.

Or learn to use arrays properly.

I suppose one could take an approach similar to:

struct Sized_array {
const char *ary;
size_t size;
};

Sized_aray string_CDR[] = {
{arr1, sizeof arr1}, {arr2, sizeof arr2}
};

--
Micah J. Cowan
Programmer, musician, typesetting enthusiast, gamer...

http://micah.cowan.name/

[James Kanze]

Re: sizeof

Micah Cowan wrote:

James Kanze <james.kanze@gm ail.comwrites:

DOn't have STL's.

Why not? The alternative is reimplementing all of the logic it
contains manually.

Might be using a freestanding implementation.

In which case, he might have to do some additional work (which
probably requires a higher level of experience as well).

You seem to want the behavoir of a
container. So you really only have two choices: use the
standard containers, or implement one yourself.

Or learn to use arrays properly.

You mean, learn enough to be able to implement std::vector
oneself.

Sooner or later, I think that most C++ programmers probably
should get to that point. (It's not as difficult as it seems.)
But it's certainly not where one should start.

--
James Kanze (GABI Software) email:james.kan ze@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34