Re: [Boost-users] [iostreams] use of gzip_compressor with strings

Subject: Re: [Boost-users] [iostreams] use of gzip_compressor with strings
From: Boncek, John (jboncek_at_[hidden])
Date: 2016-06-23 16:49:41

Thanks, just what I needed!

John

-----Original Message-----
From: Boost-users [mailto:boost-users-bounces_at_[hidden]] On Behalf Of eg
Sent: Tuesday, June 21, 2016 11:16 AM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [iostreams] use of gzip_compressor with strings

On 6/17/2016 10:26 AM, Boncek, John wrote:
> I need to do some in-memory manipulation of strings, including
> compression to gzip format.  I am new to the use of Boost and to the use
> of gzip.  I found the following snippet on the Internet, compressing a
> std::string and producing a new std::string as output.  This implies
> that gzip_compressor never produces a null byte in its output but the
> gzip_compressor documentation doesn't say that and my search of the
> underlying library zlib documentation doesn't say anything like that
> either.  So is this a correct use?
>
> std::string compress(const std::string& data)
>
> {
>
>      namespace bio = boost::iostreams;
>
> std::stringstream compressed;
>
> std::stringstream origin(data);
>
> bio::filtering_streambuf<bio::input> out;
>
> out.push(bio::gzip_compressor(bio::gzip_params(bio::gzip::best_compression)));
>
> out.push(origin);
>
> bio::copy(out, compressed);
>
>      return compressed.str();
>
> }
>

std::string() can handle strings with embedded NULL's (0's). However, 
certain other operators and functions of the class do not (e.g. 
c_str()).  See 
http://stackoverflow.com/questions/2845769/can-a-stdstring-contain-embedded-nulls

If you need to pass this as a string to someone else or use these other 
functions/operators, you may wish to encode the compressed string before 
returning it. See 
http://stackoverflow.com/questions/27529570/simple-zlib-c-string-compression-and-decompression

Ed