iofunc_lseek()

Handle an _IO_LSEEK message

Synopsis:

#include <sys/iofunc.h>

int iofunc_lseek ( resmgr_context_t* ctp,
                   io_lseek_t* msg,
                   iofunc_ocb_t* ocb,
                   iofunc_attr_t* attr );

Library:

libc

Description:

The iofunc_lseek() 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.

Returns:

EOK

Successful completion.

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).

Classification:

QNX 6

See also:

iofunc_chmod_default(), iofunc_chown_default(), iofunc_close_dup_default(), iofunc_close_ocb_default(), iofunc_devctl_default(), iofunc_lock_default(), iofunc_lseek_default(), iofunc_mmap_default(), iofunc_open_default(), iofunc_pathconf_default(), iofunc_stat_default(), iofunc_time_update(), iofunc_unblock_default(), iofunc_utime_default(), resmgr_attach()