iofunc_lseek()

Обработать сообщение _IO_LSEEK

Прототип:

#include <sys/iofunc.h>
                                       
int iofunc_lseek( resmgr_context_t *ctp,
                  io_lseek_t *msg,
                  iofunc_ocb_t *ocb,
                  iofunc_attr_t *attr );

Аргументы:

ctp

A pointer to a resmgr_context_t structure that the resource-manager library uses to pass context information between functions.

msg

A pointer to the io_lseek_t structure that contains the message that the resource manager received.

ocb

A pointer to the iofunc_ocb_t structure for the Open Control Block that was created when the client opened the resource.

attr

A pointer to the iofunc_attr_t structure that describes the characteristics of the device that's associated with your resource manager.

Библиотека:

libc

Описание:

The iofunc_lseek() helper function implements POSIX semantics for the client's lseek() call, which is received as an _IO_LSEEK message by the resource manager.

The iofunc_lseek() function handles the three different whence cases: SEEK_SET, SEEK_CUR, and SEEK_END, updating the ocb->offset field with the new position.

Note that if the IOFUNC_MOUNT_32BIT flag isn't set in the mount structure, iofunc_lseek() handles 64-bit position offsets. If the flag is set (meaning this device supports only 32-bit offsets), the resulting offset value is treated as a 32-bit offset, and if it overflows 32 bits, it's truncated to LONG_MAX. Also, this function handles combine messages correctly, simplifying the work required to support lseek.

Возвращаемое значение:

-1

Успешное завершение; the resource manager library should return a one-part IOV to the client.

EOK

The message is a combine message, and no error occurred.

EINVAL

The whence member in the _IO_LSEEK message wasn't one of SEEK_SET, SEEK_CUR, or SEEK_END, or the resulting position after the offset was applied resulted in a negative number (overflow).

EOVERFLOW

The resulting file offset is a value that can't be represented correctly in an object of type off_t.

Классификация:

ЗОСРВ «Нейтрино»

Точка остановки потока

Нет

Обработчик прерываний

Нет

Обработчик сигналов

Да

В потоке

Да

Тематические ссылки:

iofunc_attr_t, io_lseek_t, iofunc_lseek_default(), iofunc_ocb_t, lseek(), resmgr_context_t

Предыдущий раздел: Описание API системной библиотеки