newFromFd
Maps a file into memory. On UNIX, this is using the mmap() function.
If @writable is true, the mapped buffer may be modified, otherwise it is an error to modify the mapped buffer. Modifications to the buffer are not visible to other processes mapping the same file, and are not written back to the file.
Note that modifications of the underlying file might affect the contents of the #GMappedFile. Therefore, mapping should only be used if the file will not be modified, or if all modifications of the file are done atomically (e.g. using g_file_set_contents()).
Return
a newly allocated #GMappedFile which must be unref'd with g_mapped_file_unref(), or null if the mapping failed.
Since
2.32
Parameters
The file descriptor of the file to load
whether the mapping should be writable