mmap_readat - memory map a file for reading

       mmap_readat  opens  filename  for  reading,  maps the whole file into memory, closes the file, writes the
       length of the file to filesize and returns a pointer to the mapped file.

       If filename is a relative path and dirfd is not AT_FDCWD (defined in fcntl.h),  filename  is  interpreted
       relative to dirfd, which must be an open directory.

       The file is unmapped by the operating system if the process terminates.  It can also be manually unmapped
       by calling munmap from <sys/mman.h>.

       If the file could not be opened or mapped, (void*)0 is returned.

       mmap_readat - memory map a file for reading

mmap_unmap(3)

                                                                                                  mmap_readat(3)

#include<libowfat/mmap.h>

       const char* mmap_readat(const char* filename,size_t* filesize,int dirfd);