Re: Copying Few Octets from Vector

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 10 Apr 2009 12:28:00 -0700 (PDT)
Message-ID:
<764ba3fc-9cae-4a78-84da-e8cff6c8fb41@u16g2000vbb.googlegroups.com>
On Apr 10, 3:18 pm, smilesonisa...@gmail.com wrote:

    I am facing difficulty in copying few octets from a vector to a
buffer.

typedef unsigned char uint8_t;
I have a vector std::vector<uint8_t*> m_Data;


I'm not sure about the rest, but this vector doesn't contain
octets; it contains pointers.

which contains the following octets.


And none follow. So we have a vector which contains
pointers, and there are no octets. So far, so good.

I want to copy (30 74 64 230 0 8) to a buffer.


Where do these octets come from?

I saw in the web and got code where iterator is used to
copy all the octets not partial elements. How will I
retrieve 6 octets from the vector?


If the vector contains pointers, you can't. All you can get
from it is pointers.

Supposing you have a vector of octets:
    std::vector< uint8_t > data ;
*and* supposing that offset plus length are less than the
size, you can copy the first length octets, starting from
offset, using std::copy:
    std::copy( data.begin() + offset,
               data.begin() + offest + length,
               destination ) ;
You'd best check that offset + length <= data.size()
beforehand, though.

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