The following is from c.l.c++. "Vince" <vsix@caramail.com> wrote in message news:42c02e57$0$27313$626a14ce@news.free.fr...
Hi,
I would like to extract or insert some values (of different size) inside a buffer. I would like to have something like this :
BYTE Buffer[207];
CBitAPI bitbuf<Buffer, sizeof(Buffer)>;
// Extract different data int version = bitbuf.get(0,4); // Extract 4 bits from bit 0 int whatever = bitbuf.get(4,2); // Extract 2 bits from bit 4 bool ack = bitbuf.get(6,1) //Extract 1 bit from bit 6
or even better :
int nValue; bitbuf.get(4,2, nValue);
DWORD dwValue; bitbuf.get(6,4, dwValue);
Unfortunately I searched everywhere (boost, google, ) and I didn't found anything appropriate.
dynamic_bitset for instance cannot be initialized from an array...
It can according to: http://www.boost.org/libs/dynamic_bitset/dynamic_bitset.html#header-files You would use the constructor that takes two input iterators. Since this is a templated constructor, Buffer elements don't have to be 8bit bytes. boost::dynamic_bitset<> bits( &Buffer[0], &Buffer[0] + 207 ); Also see the non-member functions from_block_range,to_block_range and to_ulong that allow transfer from/to integral data types. The latter could be used to create a templated function to implement your desired behavior. // Untested and needs error checking template< typename T, class BITSET > T extract_value( BITSET aBits, size_t aBegin, size_t aSize ) { // implement size assertions here aBits.resize( aBegin + aSize ); return T((aBits<<aBegin).to_ulong()); } I'm surprised that this wasn't available for either std::bitset or boost::dynamic_bitset. Any particular reasons? Would a function with this ability be a useful addition? Certainly a more efficient implementation would be desirable. Jeff Flinn