Re: serialization of arrays

From:

=?ISO-8859-1?Q?Erik_Wikstr=F6m?= <Erik-wikstrom@telia.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 03 Sep 2007 21:18:13 GMT

Message-ID:

<pS_Ci.7777$ZA.4187@newsb.telia.net>

On 2007-09-03 22:48, aaragon wrote:

Hello everyone,

I've been trying to create a simple way to serialize C++ objects so I
can send messages among different processors (using MPI). Something
very simple is shown below:

template <class StorageType>
void Send(StorageType& c, int dest, int tag, MPI_Comm comm) {

    typedef typename StorageType::ValueType ValueType;

    int size = c.size()*sizeof(ValueType);
    char* buffer[size];
    memcpy(buffer, &c[0], size);

    MPI_Send(&buffer, size, MPI_BYTE, dest, tag, comm);
}

I tested the templated function with arrays of integers and it works
fine. However, when I try to use the dynamic_bitset provided by the
boost library, I cannot pass a reference to c[0] because operator& is
private for that class. Is there another efficient way to do a bitwise
copy???

I don't know about dynamic_bitset, but std::bitset has a to_string()
method that converts the content to a string of 1 and 0, if the bitset
is not to large you can still get quite good efficiency from that. There
is also a to_ulong() method to convert it to an unsigned long, but that
only works for small bitsets. I would suspect that dynamic_bitset at
least has a to_string() method.

If small buffers are important you'll have to write code that reads the
value from the bitset and sets the correct bits in a char array, it's
not too much work but just sending a string is a lot easier.

--
Erik Wikstr?m