io_uring_prep_read_fixed - prepare I/O read request with registered buffer

       The  io_uring_prep_read_fixed(3)  prepares an IO read request with a previously registered IO buffer. The
       submission queue entry sqe is setup to use the file descriptor fd to start reading nbytes into the buffer
       buf at the specified offset, and with the buffer matching the registered index of buf_index.

       This works just like io_uring_prep_read(3)  except  it  requires  the  use  of  buffers  that  have  been
       registered  with  io_uring_register_buffers(3).   The  buf and nbytes arguments must fall within a region
       specified by buf_index in the previously registered buffer. The buffer need not be aligned with the start
       of the registered buffer.

       After the read has been prepared it can be submitted with one of the submit functions.

       The CQE res field will contain the result of the operation. See the  related  man  page  for  details  on
       possible  values. Note that where synchronous system calls will return -1 on failure and set errno to the
       actual error value, io_uring never uses errno.  Instead it returns the negated errno directly in the  CQE
       res field.

       io_uring_prep_read_fixed - prepare I/O read request with registered buffer

       None

io_uring_prep_read(3), io_uring_register_buffers(3)

liburing-2.1                                    February 13, 2022                    io_uring_prep_read_fixed(3)

#include<liburing.h>voidio_uring_prep_read_fixed(structio_uring_sqe*sqe,intfd,void*buf,unsignednbytes,__u64offset,intbuf_index);