io_uring_prep_read - prepare I/O read request
#include <liburing.h>
void io_uring_prep_read(struct io_uring_sqe *sqe,
int fd,
void *buf,
unsigned nbytes,
__u64 offset);
The prepares an IO read request. 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.
On files that support seeking, if the offset is set to
-1, the read
operation commences at the file offset, and the file offset is incremented by
the number of bytes read. See
read(2) for more details. Note that for
an async API, reading and updating the current file offset may result in
unpredictable behavior, unless access to the file is serialized. It is not
encouraged to use this feature, if it's possible to provide the desired IO
offset from the application or library.
On files that are not capable of seeking, the offset must be 0 or -1.
After the read has been prepared it can be submitted with one of the submit
functions.
None
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_get_sqe(3),
io_uring_prep_readv(3),
io_uring_prep_readv2(3),
io_uring_submit(3)