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 to it.
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.