Structure memory allocation

[uday]

Hi All,
I need one clarification regarding memory allocation for
structure. The details are as given below :

let us consider one structure

struct {
uit32 len0;
uint8 *pointer0;
uit32 len1;
uint8 *pointer1;
);

When i want to allocate memory using malloc() for this structure is
there any way i can allocate memory for only for len0 and pointer0 or
len1 and pointer1 .

Regards,
udaykumar

 

[Ian Collins]

Hi All,
I need one clarification regarding memory allocation for
structure. The details are as given below :

let us consider one structure

struct {
uit32 len0;
uint8 *pointer0;
uit32 len1;
uint8 *pointer1;
);

When i want to allocate memory using malloc() for this structure is
there any way i can allocate memory for only for len0 and pointer0 or
len1 and pointer1 .

No, why would you want to?

 

[uday]

No, why would you want to?

I need to combine 2 function which uses the same structure .... i.e
for Ipv6 and Ipv6oEth i want to use the same struct .... so i will abe
able to combine the functionality

 

[p_cricket_guy]

Hi All,
I need one clarification regarding memory allocation for
structure. The details are as given below :

let us consider one structure

struct {
uit32 len0;
uint8 *pointer0;
uit32 len1;
uint8 *pointer1;
);

When i want to allocate memory using malloc() for this structure is
there any way i can allocate memory for only for len0 and pointer0 or
len1 and pointer1 .

I assume you do not intend to use {len0, pointer0} and {len1,
pointer1}
simultaneously. In that case, an union may be what you want.

-p_c_g.

 

[Army1987]

Hi All,
I need one clarification regarding memory allocation for
structure. The details are as given below :

let us consider one structure

struct {
uit32 len0;
uint8 *pointer0;
uit32 len1;
uint8 *pointer1;
);

When i want to allocate memory using malloc() for this structure is
there any way i can allocate memory for only for len0 and pointer0 or
len1 and pointer1 .

The latter is impossible. For the former you could try
malloc(offsetof(struct unnamed, len1)), I think it has undefined
behavior if you do enough language lawyering on the Standard, but
it is very likely to work.

 

[Army1987]

uday wrote: [snip]

let us consider one structure

struct {
uit32 len0;
uint8 *pointer0;
uit32 len1;
uint8 *pointer1;
);

When i want to allocate memory using malloc() for this structure is
there any way i can allocate memory for only for len0 and pointer0 or
len1 and pointer1 .

No, why would you want to?

I need to combine 2 function which uses the same structure .... i.e
for Ipv6 and Ipv6oEth i want to use the same struct .... so i will abe
able to combine the functionality

A union of two structs, maybe?

 

[Keith Thompson]

I need to combine 2 function which uses the same structure .... i.e
for Ipv6 and Ipv6oEth i want to use the same struct .... so i will abe
able to combine the functionality

I'm not entirely clear on what you're trying to do, but it would
probably make sense to use nested structures. For example:

struct s0 {
uint32 len0;
uint8 *pointer0;
};
struct s1 {
uint32 len1;
uint8 *pointer1;
};
struct both {
struct s0 member0;
struct s1 member1;
};

You can then allocate the entire outer structure or just one of the
inner structures.

 

[pete]

Hi All,
I need one clarification regarding memory allocation for
structure. The details are as given below :

let us consider one structure

struct {
uit32 len0;
uint8 *pointer0;
uit32 len1;
uint8 *pointer1;
);

When i want to allocate memory using malloc() for this structure is
there any way i can allocate memory for only for len0 and pointer0 or
len1 and pointer1 .

struct {
uit32 len;
uint8 *pointer;
);

 

[Tor Rustad]

I need to combine 2 function which uses the same structure .... i.e
for Ipv6 and Ipv6oEth i want to use the same struct .... so i will abe
able to combine the functionality

Hmm.. what with:

struct ip
{
uint32 len;
uint8 *ptr;
};

union ip_v6
{
struct ip v6;
struct ip v6Eth;
};

?

 

[uday]

I'm not entirely clear on what you're trying to do, but it would
probably make sense to use nested structures. For example:

struct s0 {
uint32 len0;
uint8 *pointer0;
};
struct s1 {
uint32 len1;
uint8 *pointer1;
};
struct both {
struct s0 member0;
struct s1 member1;
};

You can then allocate the entire outer structure or just one of the
inner structures.

--
Keith Thompson (The_Other_Keith) (e-mail address removed) <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

hi thanks for the possible solution ... In my case i think the use of
union dont serve my purpose but defining 2 struct within one struct
will serve my purpose ...
Regards,
udaykumar