Struct IoContext

pub struct IoContext(/* private fields */);

Newtype for aio_context_t.

Implementations

impl IoContext

pub fn new(nr_events: c_uint) -> Result<Self>

Create a new aio context instance.

Refer to Linux io_setup.

Arguments

• nr_events: maximum number of concurrently processing IO operations.

pub fn submit(&self, iocbs: &[&mut IoControlBlock]) -> Result<usize>

Submit asynchronous I/O blocks for processing.

Refer to Linux io_submit.

Arguments

• iocbs: array of AIO control blocks, which will be submitted to the context.

Examples

extern crate vmm_sys_util;
use vmm_sys_util::aio::*;

let file = File::open("/dev/zero").unwrap();
let ctx = IoContext::new(128).unwrap();
let mut buf: [u8; 4096] = unsafe { std::mem::uninitialized() };
let iocbs = [&mut IoControlBlock {
    aio_fildes: file.as_raw_fd() as u32,
    aio_lio_opcode: IOCB_CMD_PREAD as u16,
    aio_buf: buf.as_mut_ptr() as u64,
    aio_nbytes: buf.len() as u64,
    ..Default::default()
}];
assert_eq!(ctx.submit(&iocbs[..]).unwrap(), 1);

pub fn cancel(&self, iocb: &IoControlBlock, result: &mut IoEvent) -> Result<()>

Cancel an outstanding asynchronous I/O operation.

Refer to Linux io_cancel. Note: according to current Linux kernel implementation(v4.19), libc::SYS_io_cancel always return failure, thus rendering it useless.

Arguments

• iocb: The iocb for the operation to be canceled.
• result: If the operation is successfully canceled, the event will be copied into the memory pointed to by result without being placed into the completion queue.

pub fn get_events( &self, min_nr: c_long, events: &mut [IoEvent], timeout: Option<&mut timespec>, ) -> Result<usize>

Read asynchronous I/O events from the completion queue.

Refer to Linux io_getevents.

Arguments

• min_nr: read at least min_nr events.
• events: array to receive the io operation results.
• timeout: optional amount of time to wait for events.

Examples

extern crate vmm_sys_util;
use vmm_sys_util::aio::*;

let file = File::open("/dev/zero").unwrap();
let ctx = IoContext::new(128).unwrap();
let mut buf: [u8; 4096] = unsafe { std::mem::uninitialized() };
let iocbs = [
    &mut IoControlBlock {
        aio_fildes: file.as_raw_fd() as u32,
        aio_lio_opcode: IOCB_CMD_PREAD as u16,
        aio_buf: buf.as_mut_ptr() as u64,
        aio_nbytes: buf.len() as u64,
        ..Default::default()
    },
    &mut IoControlBlock {
        aio_fildes: file.as_raw_fd() as u32,
        aio_lio_opcode: IOCB_CMD_PREAD as u16,
        aio_buf: buf.as_mut_ptr() as u64,
        aio_nbytes: buf.len() as u64,
        ..Default::default()
    },
];

let mut rc = ctx.submit(&iocbs[..]).unwrap();
let mut events = [unsafe { std::mem::uninitialized::<IoEvent>() }];
rc = ctx.get_events(1, &mut events, None).unwrap();
assert_eq!(rc, 1);
assert!(events[0].res > 0);
rc = ctx.get_events(1, &mut events, None).unwrap();
assert_eq!(rc, 1);
assert!(events[0].res > 0);

Trait Implementations

impl Debug for IoContext

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Drop for IoContext

fn drop(&mut self)

Executes the destructor for this type.