how faster is to use pointers
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well,i know that returning a pointer in a function is faster than return the struct(or class) that it point to(i don''t know how to say this,my english sucks),but it make a real difference?, because i was watching some code,from an online tutorial,and they simple return the struct.
that''s all folks
The pointer can fit into a register. Returning something via a register is fast.
Most structs wont fit into a single register, so they have to be copied around memory. Memory is slow.
To answer you question, pointers are a hell of a lot faster.
Most structs wont fit into a single register, so they have to be copied around memory. Memory is slow.
To answer you question, pointers are a hell of a lot faster.
When your function returns a class/struct it makes yet another object in the memory which takes more memory, if its a pointer it doesnt make a new object, its also faster.
Just to be another cook...
Often if you''re passing a structure or class into a function you should use a reference or pointer. If you''re not going to change the struct, use a const reference or const pointer.
For example, in C:
Note that the last function, BadFunction, returns a pointer to a local variable that no longer exists when the function returns. You can''t return structs by pointers like this. Instead you should do something like this:
Hope this helps. Passing things by pointer or reference is a good way to avoid passing around huge chunks of data, and modifying data without making a copy.
In C++ you''d use references if you could. Change the "*" to "&" and the "->" to ".". A reference is like it sounds. It''s "another name" for a variable.
Hope this helps.
Helpful links:
How To Ask Questions The Smart Way | Google can help with your question | Search MSDN for help with standard C or Windows functions
Often if you''re passing a structure or class into a function you should use a reference or pointer. If you''re not going to change the struct, use a const reference or const pointer.
For example, in C:
typedef struct{ float x, y, z;}VECTOR3;void MyFunction (const VECTOR3 * v){ printf ("%f, %f, %f\n", v->x, v->y, v->z);}VECTOR * BadFunction (void){ VECTOR3 v = {0, 1, 0}; return &v // NEVER EVER DO THIS OR YOUR APP DIES} Note that the last function, BadFunction, returns a pointer to a local variable that no longer exists when the function returns. You can''t return structs by pointers like this. Instead you should do something like this:
void BetterFunction (VECTOR3 * v){ v->x = 0; v->y = 1; v->z = 0;} Hope this helps. Passing things by pointer or reference is a good way to avoid passing around huge chunks of data, and modifying data without making a copy.
In C++ you''d use references if you could. Change the "*" to "&" and the "->" to ".". A reference is like it sounds. It''s "another name" for a variable.
Hope this helps.
Helpful links:
How To Ask Questions The Smart Way | Google can help with your question | Search MSDN for help with standard C or Windows functions
Just don''t return a pointer to a locally allocated object. An example is
What you should do is
Object* f(){ Object a; return &a;} What you should do is
Object* g(){ Object* a = new Object(); return a;}
...and delete it later.
Or return some kind of smart pointer instead, like std::auto_ptr or boost::shared_ptr.
Helpful links:
How To Ask Questions The Smart Way | Google can help with your question | Search MSDN for help with standard C or Windows functions
Or return some kind of smart pointer instead, like std::auto_ptr or boost::shared_ptr.
Helpful links:
How To Ask Questions The Smart Way | Google can help with your question | Search MSDN for help with standard C or Windows functions
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