Output all remaining data on a gz-file pointer
Reads to EOF on the given gz-file pointer from the current position and
writes the (uncompressed) results to standard output.
You may need to call gzrewind() to reset the file
pointer to the beginning of the file if you have already written data
If you just want to dump the contents of a file to the output buffer,
without first modifying it or seeking to a particular offset, you may
want to use the readgzfile() function, which saves
you the gzopen() call.
The gz-file pointer. It must be valid, and must point to a file
successfully opened by gzopen().
The number of uncompressed characters read from gz
and passed through to the input, or FALSE on error.