std::streambuf::pos_type izstream::seekoff ( std::streambuf::off_type  offset, std::ios_base::seekdir  dir, std::ios_base::openmode  = std::ios_base::in  )

inline

Definition at line 102 of file izstream.h.

References clear(), and end.

Referenced by seekpos().

    {
        // Using a switch instead results in:
        //  In member function `virtual std::streampos izstream::seekoff(long int, std::_Ios_Seekdir, std::_Ios_Openmode)':
        //  warning: enumeration value `_M_ios_seekdir_end' not handled in switch
        //  warning: case value `0' not in enumerated type `_Ios_Seekdir'
        //  warning: case value `1' not in enumerated type `_Ios_Seekdir'
        //  warning: case value `2' not in enumerated type `_Ios_Seekdir'

        if (dir==std::ios::end)
        {
            clear(rdstate()|std::ios::failbit);
            return EOF;
        }

        // We only do relative seeking to avoid unnecessary decompression
        // of the whole file
        if (dir==std::ios::beg)
            offset -= tellg();

        // Calculate future position in streambuffer
        const char *ptr = gptr()+offset;

        // This is the number of bytes still available in the buffer
        const size_t sbuf = egptr()-gptr();

        // Check if the new position will still be in the buffer
        // In this case the target data was already decompressed.
        if (ptr>=eback() && ptr<egptr())
        {
            // Absolute position in z-stream
            const z_off_t zpos = gztell(fFile)-sbuf; //gzseek(fFile, 0, SEEK_CUR);

            gbump(offset);

            return zpos+offset;
        }

        const streampos pos = gzseek(fFile, offset-sbuf, SEEK_CUR);

        // Buffer is empty - force refilling
        setg(fBuffer+4, fBuffer+4, fBuffer+4);

        return pos<0 ? streampos(EOF) : pos;

        /*
         // SEEK_END not supported by zlib
         if (dir==ios::end)
         {
             // Position in z-stream
             const z_off_t zpos = gzseek(fFile, offset, SEEK_END);
             if (zpos<0)
                 return EOF;

             return fill_buffer()==EOF ? EOF : zpos;
         }
         */
        return EOF;
    }

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