! @abstract Determine format by peeking at the start of a file @param fp File opened for reading, positioned at the beginning @param fmt Format structure that will be filled out on return @return 0 for success, or negative if an error occurred.
See Implementation
! @abstract Determine format by peeking at the start of a file @param fp File opened for reading, positioned at the beginning @param fmt Format structure that will be filled out on return @return 0 for success, or negative if an error occurred.