I am learning and I'd like to know the best way how to do the following array copy, Consider this code:
void Cast1LineSpell(UINT Serial, char *chant)
{
byte packet[] = { 0x0F, 0x03,
(Serial >> 24) & 0xFF, (Serial >> 16) & 0xFF,(Serial >> 8) & 0xFF, Serial & 0xFF,
0x9A, 0x92, 0x00, 0x00, 0x00, 0x1A };
byte prepareSpell[2] = { 0x4D, 0x01 };
byte chant_length = sizeof(chant) / sizeof(chant[0]);
byte chant_name[] = { 0x4E, chant_length, }; // <= how can i put the bytes in chant* into the rest of this array, and then append bytes 0x00 and 0x4E on to the end of it?
}
how can i put the bytes that are inside of *chant
, and then put them into the end of chant[]
and then append bytes 0x00
and 0x4E
on to the end of it?
Can anybody provide a solution? Much Appreciated.
You are using dynamic arrays so the sizeof(chant)
will always be the size of a pointer, and sizeof(chant) / sizeof(chant[0])
won't be the number of elements in the array. That only works for static arrays .
Also, you are redeclaring chant
which is simply an error.
In conclusion, since you do not know the number of elements in chant
, there is no way to do what you want to do.
According to my understanding, in C++, all arrays passed into a function are treated as pointers no matter they are statically allocated or dynamically allocated or even you write the argument as char chant[]
, (ie, only the address of the first element is passed in).
Example:
void f(int value[]){
cout<<"size in f: "<<sizeof(value)/sizeof(int)<<endl;
}
int main(){
int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
cout<<"size in main: "<<sizeof(arr)/sizeof(int)<<endl;
f(arr);
return 0;
}
the result is:
size in main: 8
size in f: 1
So as you can see, in f()
, value[]
is the same as value *
, and sizeof(value)
is the size of the pointer.
You should (always) also pass in the length when you pass an array into a function.
void f(int value[], size_t size){
cout<<"size in f: "<<size<<endl;
}
int main(){
int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
size_t size = sizeof(arr)/sizeof(int);
cout<<"size in main: "<<size<<endl;
f(arr, size);
return 0;
}
The output:
size in main: 8
size in f: 8
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