aiocb, aiocb64

Asynchronous I/O control block

Synopsis:

#include <aio.h>

struct aiocb {
    int                 aio_fildes;
    int                 aio_reqprio;
#if _FILE_OFFSET_BITS - 0 == 64
    off_t               aio_offset;
#elif !defined(_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS == 32
#if defined(__LITTLEENDIAN__)
    off_t               aio_offset;
    off_t               aio_offset_hi;
#elif defined(__BIGENDIAN__)
    off_t               aio_offset_hi;
    off_t               aio_offset;
#else
 #error endian not configured for system
#endif
#else
 #error _FILE_OFFSET_BITS value is unsupported
#endif
    __volatile void*    aio_buf;
    size_t              aio_nbytes;
    struct sigevent     aio_sigevent;
    int                 aio_lio_opcode;
    ssize_t             _aio_reserved;
    int                 _aio_pad[3];
    ... 
};

#if _LARGEFILE64_SOURCE - 0 > 0
struct aiocb64 {
    int                 aio_fildes;
    int                 aio_reqprio;
    off64_t             aio_offset;
    __volatile void*    aio_buf;
    size_t              aio_nbytes;
    struct sigevent     aio_sigevent;
    int                 aio_lio_opcode;
    ssize_t             _aio_reserved;
    int                 _aio_pad[3];
    ...
};
#endif /* _LARGEFILE64_SOURCE */

Description:

The aiocb and aiocb64 structures define the control block for asynchronous I/O operations. They include at least the following:

aio_fildes
The file descriptor to use in an asynchronous I/O operation.
aio_reqprio
The request priority offset.
aio_offset
The file offset.
aio_offset_hi
(aiocb only) The high-order bits of the file offset.
aio_buf
A pointer to a buffer.
aio_nbytes
The length of a transfer.
aio_sigevent
A pointer to a sigevent structure that specifies the signal number and value.
aio_lio_opcode
The operation to be performed; one of the following:
  • LIO_NOP — a lio_listio() element operation option indicating that no transfer is requested.
  • LIO_NOWAIT — a lio_listio() synchronization operation indicating that the calling thread is to continue execution while the lio_listio() operation is being performed, and no notification is given when the operation is complete.
  • LIO_READ — a lio_listio() element operation option requesting a read.
  • LIO_WAIT — a lio_listio() synchronization operation indicating that the calling thread is to suspend until the lio_listio() operation is complete.
  • LIO_WRITE — a lio_listio() element operation option requesting a write.

Classification:

aiocb is POSIX 1003.1 AIO; aiocb64 is Large-file support

Caveats:

The first time you call an aio_* function, a thread pool is created, making your process multithreaded if it isn't already. The thread pool isn't destroyed until your process ends.

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