Subject: Re: [boost] [iostreams] array and gzip_decompressor
From: Chris Hamilton (chamilton_at_[hidden])
Date: 2010-03-01 07:43:54
> On 2/23/2010 10:48 PM, Nikolay Mladenov wrote:
>>
>> Is there another way I should be creating gzipped stream into memory?
>> Or maybe the arrays could be made peekable?
>>
>
> Perhaps you could read it into a stringstream.
>
> namespace io = boost::iostreams;
>
> io::filtering_istream in;
> in.push(io::gzip_decompressor());
> in.push(io::file_source(fileName.c_str(), std::ios_base::in |
> std::ios_base::binary));
> std::stringstream memStream;
> memStream << in.rdbuf();
If you don't know before-hand how big the output can be, you can write
into a std::vector relatively easily. The following creates an
ovectorstream object:
template<typename Ch>
struct basic_vector_sink
{
typedef Ch char_type;
typedef bio::sink_tag category;
typedef std::vector<char_type> vector_type;
basic_vector_sink( vector_type& vector ):
_vector(vector)
{
}
std::streamsize write( const char_type *buf, std::streamsize n )
{
if ( n <= 0 ) return n;
size_t s = _vector.size();
_vector.resize( s + n );
memcpy( (void*)((&_vector[0])+s), (const void*)buf,
n*sizeof(char_type) );
return n;
}
vector_type& _vector;
};
typedef basic_vector_sink<char> vector_sink;
typedef bio::stream<vector_sink> ovectorstream;
In my mind, something like arraystream (but for vectors) would be useful
in boost::iostreams. The above is a pale imitation of the full
functionality offered by an arraystream (bidirectional, seekable, etc),
but it does the job for me.
Cheers,
Chris