Pointer Confusion

Question

received_data is a global char array of length 256. It contains a string at offset rx_pos_p i.e. received_data[rx_pos_p]. I want to return the address of this string through a pointer mem, but I think I am making a mistake. I have written the function as follows:

uint8_t get_bytes(char **mem, uint8_t len){// Be watchful pointer to a pointer
        if(bytes_received() >= len){
            mem = &received_data[rx_pos_p]; //(char *)( received_data + rx_pos_p );

            return 0;
        }
        else
        return FOO;
    }

What should be the type of mem i.e. **mem or *mem ?

Devolus · Accepted Answer · 2014-01-12 08:39:04Z

4

You need to do :

*mem = &received_data[rx_pos_p];

You want to return the pointer in the pointerpointer, so you must dereference it.

answered Jan 12, 2014 at 8:39

Devolus

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cairnc · Accepted Answer · 2014-01-12 10:15:26Z

1

What should be the type of mem i.e. **mem or *mem ?

Since mem is a pointer to a pointer *mem is a pointer to a character (such as the address of the first char of an array)
**mem is a character and is equivalent to (*mem)[0]

answered Jan 12, 2014 at 10:15

cairnc

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