Re: [Boost-users] Seekg on a gzip'd file...Is this possible?

13 Mar 2009

      I changed my code a bit but I¹m still getting errors when trying to use
boost::iostreams::seek as follows:

 boost::iostreams::seek(inputStream,position_to_offset(bytesToSkip),BOOST_IO
S::cur); 

What is the correct way to go about this?
Gerrick

On 3/13/09 9:29 AM, "Gerrick Bivins"  wrote:
...
Hello all, 
I¹m switching one of my projects over from java to c++. Basically it¹s a gzip
file reader, where I¹d like to parse a bunch of numbers (floats, ints,
doubles)
 and in some instances I¹d like to skip some of the data. I¹m a  ³noob² to
boost and after getting the file reader working using the boost like this:
{
....
std::ifstream ormodelFile(filenameForTimeStep.c_str(),
                                  std::ios_base::in|std::ios_base::binary);
boost::iostreams::filtering_istreambuf compressedFileFilter;
compressedFileFilter.push(boost::iostreams::gzip_decompressor());
compressedFileFilter.push(ormodelFile);
this->inputFile.rdbuf(&compressedFileFilter); //where inputFile is a an
istream.
...
//do the file reading
}
I tried to add the skipping parts to the code by simply calling:
{
...
 double value;
 this->inputFile->seekg(sizeof(double),ios::cur);
...
}
 the fail bit is set on the inputFile istream. Is it possible to do this using
boost? I¹m pretty ³green² with boost so I¹m sure it¹s just my misunderstanding
of how to use the lib but I couldn¹t find my way around the docs to well.
The best I could find was that I need to somehow make my stream ³seekable² but
it wasn¹t too clear to me how to do this.
Any help would be greatly appreciated.
Gerrick