Re: Convert short to byte array

From:
Victor Bazarov <v.bazarov@comcast.invalid>
Newsgroups:
comp.lang.c++
Date:
Thu, 28 Feb 2013 16:47:35 -0500
Message-ID:
<kgoj7e$4f8$1@dont-email.me>
On 2/28/2013 4:43 PM, Nobody wrote:

On Thu, 28 Feb 2013 11:21:55 -0800, porcelli.giuseppe wrote:

Sorry for this stupid question by I am very new to C++

how to convert this routine to C++ ?

    private byte[] getByteFromShort(short x) {
        byte[] a = new byte[2];
        a[0] = (byte) (x & 0xff);
        a[1] = (byte) ((x >> 8) & 0xff);
        return a;
    }

Bare (C-style) arrays can't be returned by value. You need to use
e.g. std::array (std::tr1::array prior to C++11), e.g.:

    std::array<uint8_t, 2> getByteFromShort(uint16_t x) {
        std::array<uint8_t, 2> a;
        a[0] = (uint8_t) (x & 0xff);
        a[1] = (uint8_t) ((x >> 8) & 0xff);
        return a;
    }

If you really want to use a bare array, have the caller pass it in:

    void getByteFromShort(uint16_t x, uint8_t a[2]) {

To the OP: this is a bit dangerous. The second argument is an address
of a 'uint8_t' value, but there is no guarantee that it points to an
array of two such values (so the index 1 can be used), and there is no
way for the compiler to verify that. I would probably recommend passing
this array by reference:

     void getByteFromShort(uint16_t x, uint8_t (&a)[2]) {

         a[0] = (uint8_t) (x & 0xff);
        a[1] = (uint8_t) ((x >> 8) & 0xff);
    }

[..]


V
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