Inserting bytes into float array

Hi,
I welcome myself to my first visit to the form - hope it will justify my expectations.

Here is my first question.
I declare a float array (takes 4 bytes, 32 bits).
Most of my array is filled with float numbers which is fine.
I wish to fill some cells with several addressable bytes each.

I have tried (example):

array[x] = byte << 16; which works OK, but overwrites other bytes.

array[x] |= byte << 16; Get lvalue error.

tried (uint32) array[x] |= byte << 16; Get lvalue error.

I realize the array is a pointer, so I tried even dereferencing it (&), but for no avail.

What is the right way to load separate bytes into a floating point array cell, and be able to read them back one by one?

Thanks
samtal

Welcome :)

You can create a char* pointer to the array and access the bytes that way.

Code:

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char * c_arr = array;
c_arr[5] = 0; //writes the 6th byte, in the 2nd floating point num
c_arr[x*4+2] = 0; // access second halfword of element x

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Beware of Endianness! -- be sure that you're writing the bytes you wanted to.

You may have to do

char * c_arr = reinterpret_cast<char*>(array);

And btw, an array is not a pointer and you don't dereference a pointer with & (it's *).

Thanks for your support.
Unfortunately I could not get it to work.

The line
char * c_arr = (char*)array; (array is my floating point array)
compiles OK, but when I load data into its locations

c_arr[5] = 0xA; or *(c_arr+x) = y;

It builds a new array c-arr[], where the data is loacted.
This is not what I was looking for.
I want to load byte or half word into cells in my floating point array.
Any other idea ?
My basic thinking was that I can simply write anything into any of the array addresses (&array+offset), but it seems as if once the array is defined as floating point, it will refuse any casting.
I even tried casting it into a uint32 which is its basic size, but it only generates casting errors.

Can anyone come up with a tested working solution?
I'd appreciate it very much becasue I need it and because I need to understand how to do it and why it does not work the way I do.


and, Elaysia you were right, I should have wrote 'referencing' (&), not 'dereferencing' (*).
but, Array address IS a pointer.
"array[i]" equals "*(array + i)".

samtal

Quote:

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Originally Posted by samtal

The line
char * c_arr = (char*)array; (array is my floating point array)
compiles OK, but when I load data into its locations

c_arr[5] = 0xA; or *(c_arr+x) = y;

It builds a new array c-arr[], where the data is loacted.

---

No, c_arr is a pointer, not an array, so "builds a new array" is nonsense. It overwrites the data of the array named array (assuming you don't go out of bounds).

Quote:

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Originally Posted by samtal

but, Array address IS a pointer.
"array[i]" equals "*(array + i)".

---

Yeah, but that does not mean that an array is a pointer.

Why do you want to do this, anyway?